Photo: NASA/JPL-Caltech

The Galaxy Evolution Explorer (GALEX), a space-based observatory surveying distant galaxies in ultraviolet light, has made an important discovery in our own Milky Way galaxy. Mira, a red giant star about 400 light years away from Earth in the constellation Cetus, has a tail of gas and dust that stretches 13 light years through space (this means that light emitted by Mira now won't reach the other end of its tail until the year 2020). A tail like this has never been discovered around a star before.

Thousands of millions of years ago, Mira was a star like our own Sun, a main sequence star. When main sequence stars grow old, they expand to enormous size and cool. Mira has reached this stage, becoming a red giant which is gradually blowing its outer layers of gas away into space. Over time, it will become a planetary nebula and eventually die as a white dwarf - the hot, glowing remnant of a dead star's core.

Mira is unusual, among stars in the Milky Way, in that it is moving very quickly with respect to the stars around it. It moves through space at 130 km/s, or 291,000 miles/hour. It is also a binary star – it has a white dwarf companion star (Mira B) and the pair of stars orbit slowly around each other as they move through space.

Mira's tail is made of gas and dust which has been ejected by the star over the last 30,000 years, forming a wake behind it as it moves through the interstellar gas and dust of the Milky Way. Studies of the chemical composition of the tail, at different distances from the star, will offer a fascinating opportunity to learn about the processes of stellar evolution and mass-loss in red giant stars.

Google has announced Google Sky, a new feature in Google Earth that lets you browse the entire night sky. Download the latest version of Google Earth, and you'll find a new button on the toolbar, which switches you to the sky view.

Sky mode includes clickable layers containing the complete Yale Bright Star Catalogue, Messier Catalogue and Dreyer's New General Catalogue of nebulae. Deep sky objects, such as the Horsehead Nebula, are accompanied by handy explanatory notes from Wikipedia. Other layers include a showcase of photos from the Hubble Space Telescope and a tour of stellar evolution, from star formation in a molecular cloud through to death as a planetary nebula.

The Large and Small Magellanic Clouds
Originally uploaded by Ken Schwarz

The Magellanic Clouds are the nearest neighbours to our own Milky Way galaxy – the Large Magellanic Cloud is about 160,000 light years away, and contains about 10 billion stars (about 1/10 the number of stars in the Milky Way). Its smaller companion, the Small Magellanic Cloud, is about 200,000 light years away and is about 100 times smaller than the Milky Way. They can't be seen from the UK, but are easily visible in the night sky south of the equator. They are named after the explorer Ferdinand Magellan, who observed them while circumnavigating the globe between 1519 and 1522.

Often in the science of astronomy, an image will appear that makes me quietly go "wow" in awe. The Japanese Aerospace eXploration Agency, JAXA, has produced one of those images from its Kaguya (Selene) lunar orbiter.

Kaguya entered lunar orbit a month ago. Its mission is to develop the technology and to gather scientific data for future lunar exploration.

Full details of the spectacular movie of the Earth setting behind the Moon can be seen in this JAXA press release.

"Earth-sets" do not occur naturally on the Moon - the Moon always presents the same face towards the Earth, and so if you were to stand on the side of the Moon that faced the Earth, the Earth would always appear in the same area of the sky. However, Earth-rise and Earth-sets can occur on spacecraft orbiting the Moon.

The first images were taken of the lunar surface by Kaguya in early November 2007, and they can be seen in this JAXA press-release... and they are equally stunning.

We think the moon formed when a Mars-sized planet (Theia) smashed into the proto-Earth four and a half billion years ago. This remarkable idea is supported by the geology of moon rocks, brought back by the Apollo astronauts between 1968-1974, and by much more recent computer simulations.

But one puzzle remains: the relative proportions of oxygen isotopes are identical for Earth rocks and moon rocks. (Isotopes are different forms of an element that vary only in the mass of their atoms.) Originally this was taken to mean that the moon and Earth came from the same source — neatly supporting the impact hypothesis — until the computer simulations showed that most of the moon must be derived from Theia, not Earth. But Theia must have had a different proportion of oxygen isotopes to the proto-Earth.

This paradox is resolved by recent calculations. These show that the collision between Theia and proto-Earth was so violent that both bodies were extensively melted or vaporized and thoroughly mixed before Earth and moon condensed after just 1000 years. This eliminated variations in the proportions of oxygen isotopes.

This is exciting research as it implies that moon rocks may resemble the rocks of early Earth. Ironically we can't find rocks from Earth's earliest times here because plate tectonics and weathering has destroyed such ancient material. It seems that to learn about early Earth we should look to the moon.

A recently discovered asteroid, which passed close to the Earth in November, may strike Mars on 30 January 2008. Asteroid 2007 WD5 will pass very close to Mars at the end of the month. Astronomers had originally estimated a 1 in 75 chance that it would hit the planet. Recent observations have increased this to a 1 in 28 chance of an impact. As more observations are made, we may see that the most likely path of the asteroid will pass by Mars completely.

2007 WD5 was discovered on 20 November 2007 by the Catalina Sky Survey in Tucson, Arizona. It had passed within 7.5 million km of the Earth on 1 November 2007 and is moving away from the Earth towards Mars. Its orbit could bring it back to the Earth, years or decades from now, but there is no apparent risk of an impact with our planet.

If the asteroid were to strike Mars, it would produce an explosion equivalent to about 3 megatons of TNT. It would not be the first impact that we have seen in our solar system. In 1994, the fragments of Comet Shoemaker-Levy 9 struck Jupiter over several days, producing a series of explosions that were visible through small telescopes.

A 250m-diameter (600ft) asteroid passed by the Earth this morning (29 January, closest approach at 0833 GMT). The asteroid, 2007 TU24, came as close as 538,000km (334,000 miles), just beyond the Moon's orbit.

NASA estimates that there are around 7000 near-Earth asteroids as large as 2007 TU24, and a similar object can be expected to pass this close to Earth about every five years or so. However, Earth impacts for an object this size only occur every 37,000 years on average.

According to NASA's Near Earth Objects (NEOs) fact sheet, 'There are no known NEOs on a collision course with the Earth. There is a possibility that an as yet undiscovered large NEO may hit the Earth, but the probability of this happening over the next 100 years is extremely small.'

An asteroid is considered potentially hazardous if it is larger than 100m, and is expected to pass the Earth within 20 times the Earth-Moon separation. The Earth-Moon distance is about 0.0026 AU (1 AU = 149.6 million km).

It's hoped that detailed observations of 2007 TU24 will reveal how the asteroid is composed - i.e. whether it is a single solid object or a loose collection of rubble, information which could help plan our defence against future hazardous asteroids.

As mentioned in a recent post, the considerably smaller asteroid 2008 AF3 (27-metre diameter) passed by the Earth as close as the Moon just over two weeks ago. A 600m-wide asteroid, 2004 XP14, flew past the Earth at roughly the same distance just over six months ago.

Artist's impression of rings around Rhea
Credit: NASA/JPL

The Cassini spacecraft has detected what may be evidence for rings around Rhea, Saturn's second largest moon. This is the first time that rings have been found around a planet's moon. The discovery is the result of work by a team led by Cassini scientist Geraint Jones, of University College London, and is reported in the 7 March issue of the journal Science.

Rhea is roughly 1500 km in diameter and appears to be surrounded by at least one ring and a broad dusty disc extending up to 5900 km from the moon. The evidence for rings came from measurements made by Cassini's Magnetospheric Imaging Instrument (MIMI). MIMI measured distinctive drops in the flow of electrons around Rhea. Interestingly, the drops occur symmetrically on either side of Rhea, suggesting the presence of rings circling the moon. The material making up the rings probably ranges in size from small pebbles up to boulders, and could be the remnant of a collision with an asteroid or comet in Rhea's distant past.

“Seeing almost the same signatures on either side of Rhea was the clincher. After ruling out many other possibilities, we said these are most likely rings. No one was expecting rings around a moon”
Geraint Jones, University College London

Promethei Planum, near the south pole of Mars
Credit: ESA/ DLR/ FU Berlin (G. Neukum)

The European Space Agency (ESA) released a beautiful photo from the Mars Express spacecraft today. The photo above shows Promethei Planum, a region near the south pole of Mars which is covered by up to 3500m of ice during the Martian winter.

On the left of the photo, we can see a broad sheet of ice, which is an extension of the south polar ice cap. The steep flanks clearly show white, clean ice. The thickness of the ice is between 900 and 1100m. To the right of the ice sheet are structures that may have been created by basaltic lava flow from a volcano. The dark dunes towards the bottom of the image are most likely made up of dust originating from this lava flow or volcanic ash. Finally, the far right (or northern) side of the photo contains an impact crater, which is approximately 100 km wide and 800 m deep. The crater’s interior is partly covered in ice.

More photos are available from the ESA Mars Express web site.

The Cassini spacecraft performed a close flyby of Saturn's moon Enceladus on Wednesday, passing within 50km of the surface at closest approach. Scientists are particularly interested to learn more about the icy plumes, rising from the south pole of Enceladus, that were discovered by Cassini in 2005. The spacecraft passed 200km above the south polar region this week – hopefully close enough to pass through the plumes and tell us more about these strange icy geysers. You can learn more about Enceladus in the following video from the Cassini web site, and read about the flyby in detail on the flyby blog. There is also a section of the Cassini web site where you can browse the raw images from the flyby.

This week is the annual Royal Astronomy Society's NAM week - the UK's National Astronomy Meeting.

It is an opportunity for astronomers to showcase the latest astronomical research being carried out all around the UK. In 2007 it was been held at the University of Central Lancashire, in 2006 at the University of Leicester, and in 2005 at the University of Birmingham.

This year, we are at the historical Queen's University Belfast, with an attendance of over 600 astronomers from all around the UK, from the students studying to get their doctorates to their professors. There are so many talks on such a wide variety of subjects that there are six different lectures running simultaneously!

I hope to post my highlights of the meeting over the next few days...

The Astronomy Education and Outreach session at this weeks NAM revealed lots of exciting events to look forward to over the next few years!

Iwan Williams (University of London) began the session by being happy that a small number of students were now beginning to get low grades in GCSE astronomy...! (The majority of GCSE students are 14-16 year old school children)

But why was Iwan happy about this? Well, it proves that a huge cross-section of school children with a wide range of abilities now have the chance to do GCSE astronomy in 'normal' schools, and not just the very best students in private schools. Some 1400 students did the GCSE Astronomy exams in the UK this year, up from 1200 students in the previous year.

Jacquie Milligan (Glenlola Collegiate Girls School) introduced us to how the Faulkes Telescopes are being used in her science lessons, even though she is a biologist. But rather than tell us herself how the project went, Jacquie's students came along and told us what they did for themselves! When two young schoolgirls speak so confidently about their work in front of an audience of experienced research astronomers, it gives great confidence in the future of UK science.

Paul Roche (Cardiff University) told us how big an asteroid was required to remove Aberystwyth from the map whilst leaving Snowdonia intact - by using an asteroid impact simulator! You can do the same for yourself at the Down2Earth website. And when the Deep Imact mission blasted a crater in an asteroid in 2004, school children were the first to take images of the event using the Faulkes Telescope. Paul also recommended using Google Earth to study asteroid impacts on the Earth. Can you find any? Meteor crater in Arizona is a good place to start looking...

There is so much going on here at NAM about astronomy outreach that I have had to spread the news over two posts!

Lars Christensen indicated some of the many world-wide events that will be taking place to celebrate the International Year of Astronomy in 2009, while Steve Owen highlighted some of the UK plans. Events include the 100 hours of astronomy on April the 2nd-5th 2009, the cosmic diary blog, and the spring and autumn moon watches.

Douglas Pierce-Price highlighted the involvement of the European Southern Observatory, and asked everyone to vote for their favourite picture at the Catch a Star competition website. Douglas also announced that the astronomer's hotel at the European Southern Observatory at Paranal in Chile (below) will feature in the next James Bond film - as the baddies lair!

To end the session, Rita Tojeiro highlighted the fun that was had in Scotland, during the Dark Sky Scotland series of events. Over 5000 people attended 35 events - even the occasional bad weather did not dampen the enthusiasm of visitors! Rob Hill finished the session encouraging people to attend the 2009 European Conference on Light Pollution, to be held in Armagh, Northern Ireland.

And finally, it was a announced that a gallery of images will be on display in Liverpool in June 2008 titled From Earth to the Universe.

12 years ago, we didn't even know planets could exist around distant stars. Today, we know of almost 300 of them!

The exosolar planet session here at this year's NAM began with the announcement by Rachael Smith (Institute of Astronomy, University of Cambridge) of the astonishing discovery of two asteroid belts orbiting the star eta Tel.

Such a system may sound familiar to you... that is because we have two asteroid belts in our own solar system! In our solar system, one is between the orbits of Mars and Jupiter (the asteroid belt) and one is at the very edge of our solar system (the Kuiper-Edgeworth belt, of which Pluto appears to be the closest and largest member).

However, eta Tel is a very young system, only 12 million years old (our solar sytem is 4,500 million years old), and so eta Tel reminds us of how our solar system must have looked long ago, before Jupiter and Saturn formed. In fact, the asteroid belts in eta Tel may began to stick together to form two large planets in the future.

Artist's impression of newly discovered planets around the star Ogle-2006-BLG-109 (Credit: KASI/CBNU/ARCSEC)

Following on with the same theme, Martin Dominik (University of St Andrews) described a system called Ogle-2006-BLG-109, which contained two Jupiter-sized planets at 2.3 & 4.6 times the Sun-Earth separation - again, very similar to the planets Jupiter & Saturn in our solar system. In total, astronomers now know of 26 multiple planet systems, and 4 of these planets are in habitable zones - the location around a star that is neither too hot or too cold for life.

Astronomer Elain Simpson of the Queen's University Belfast announced the discovery of 5 more planets using SuperWASP, with 2 more suspect planets. Elain initially discovered 44 possible planets, and by observing each and every one in more detail using the Nordic Optical Telescope, she discovered the 5 planets. All these planets are hot Jupiters - large planets, very close to their parent star.

It makes us all wonder when the first Earth-like planet will be found - This year? There is a European Space Agency mission being planned called Darwin which has the aim of finding traces of water, ozone & carbon dioxide around some of these distant planets, helping us to identify Earth-like planets in the very near future.

One of the newest topic in astronomy presented at this year's NAM was the atmosphere's in exosolar planets session. I find it staggering that astronomers can now study the atmospheric composition of planets orbiting distant stars!

The ultimate aim is to find an atmosphere around a planet that could sustain life. That has not been found yet, but it is only a matter of time...

There are two ways to study the atmosphere of a distant exoplanet. If the planet ever passes in front of the parent star, some starlight is blocked by the planet itself, but some of the star-light is absorbed by the planet's atmosphere - and by looking at what wavelength's of starlight is absorbed by the planet's atmosphere, you can work out what chemicals are present in the planet's atmosphere. Also, when the planet moves around to the far side of the star, it can reflect starlight in our direction, and by looking at that reflected starlight astronomers can work our what chemicals are doing the reflection.

Doing this in reality is incredibly difficult, due to the parent star being so bright, and the planets being so small and faint.

An artist depicts the extrasolar planet, TrES-1, and its host star. Courtesy Jeffrey Hall and Lowell Observatory.

The highlight of the session was the research done by Tommi Koskinen at the University College London, on a planet called HD17156b. This planet was actually discovered by amateur astronomers! It is very impressive what new science can be achieved by experienced amateur astronomers. In this example, the planet moved in front of its parent star, hiding 0.6% of the light coming from the star - and this is enough for skilled amateur astronomers to detect the planet.

While amateurs monitor the entire sky, professionals scrutinise individual objects, and this is exact what Tommi and his colleagues have done. They discovered that the orbit of the planet around the parent star is very elliptical (strongly oval shaped), and so the temperature of the planet can vary by a staggering 1000^oC depending on where it is in its orbit. They also discovered that when the planet is close to the star it rotates at the same rate at which it orbits, but when it is further away from the star it rotates quicker.

Prof. Mark Bailey's (Armagh Observatory) public lecture at NAM 2008 celebrated the 100th anniversary of the Tunguska event, when a large meteoroid exploded 5 miles above a remote region of Siberia.

The eyewitness reports of the event are, quite frankly, terrifying.

The event was even observed from Northern Ireland, some 3,500 miles away from Tunguska. The astronomer working at the Armagh Observatory that night noted a "nocturnal glow" in the log book (even though the Moon was not present), which was bright enough to read a newspaper and play cricket, even after midnight!

Fortunately, a Tunguska type event is only expected to occur, on average, once every century. And a meteor crater type impact is only expected once per million years.

But it is really difficult to estimate precisely how frequently such events occur. If you were to ask an astronomer in 1993 what the chance was of a large comet hitting Jupiter, they would have said maybe once every 100 million years... but just a year later, Comet Shoemaker-Levy 9 did hit Jupiter.

And astronomers are discovering new Near-Earth Objects (asteroids with orbits that come relatively close to the earth) all the time, as the graph below shows (courtesy NASA/JPL).

But, while such events may scare us, Mark pointed out that our entire existence was dependent on the impact that wiped out the dinosaurs. If that collision had not have happened, we would not be here today.

The asteroid that wiped out the dinosaurs originated in the outer solar system, where a chance gravitational tug from another asteroid set it on a collision course with Earth. If that tug had been slightly different by a minuscule amount, the asteroid would have missed Earth, the dinosaurs would have continued their reign, and tiny mammals (from which we evolved) would never have got started - and so humans would not be here today.

Prof. Bailey then began to discuss the financial implications of ignoring the asteroid threat. If the Tunguska impact was centred on London, it would have destroyed everything within the M25, killing millions. If it hit anywhere else in the UK, it would have still killed tens of thousands. If we are lucky, and such an asteroid strikes land just once every ten attempts, that is still a major town disappearing every thousand years.

But the real risk is from the small, more frequent asteroids. We expect a 10m meteoroid to hit every year, causing a 100m crater. Maybe only 1 in ten would hit a populated area - but considering the average density of England, that once-a-decade strike could still kill 12 people.

Mark argued that this represents an intolerable risk, and using economic reasoning suggested that significant investment is required in order to research the threat posed.

Today, almost a hundred years after the event, little can be seen of the aftermath in Tunguska. Only a few felled trees remain visible, and even the small rise at the epicentre (upon which a totem pole to the Siberian fire god Agby stands) will be flat in a decade. One member of the audience suggested that, even though the fallen trees have almost disappeared, new growth may follow the lines of fertiliser provided by the fallen trees, providing at least some evidence to what happened nearly a century ago.

This years National Astronomy Meeting at the Queen's University Belfast came to a close on Friday, after 4 days of talks on the latest breakthroughs in UK astronomical research.

There were so many excellent talks this year, that it was impossible to keep up blogging about them! So expect a few more blogs to appear from me over the next week.

Many press articles were released during the week, including...

• World's largest digital camera to change view of the Universe
• Witnessing the formation of distant galaxies
• Quasars quash star formation in Active Galactic Nuclei
• Science and art of Hubble Space Telescope on show at Queen's
• Astronomers find embryonic planet
• The source of the solar wind
• The sun's magnetic fountains
• "Focused" solar explosions get hotter
• Stereo snaps first footage of a solar tsunami
• Flames leave astronomers in a spin
• The evolution of venus: first too fast, then too slow
• Planet finder catches a comet
• Catching a shooting star on Mars
• Chance of finding earthlike planets on the 'RISE' as UK astronomers deploy new camera
• Do dwarf galaxies favour Mond over dark matter?
• Revealing the multi-wavelength sky with AstroGrid
• Newborn Brown Dwarfs Stir up the Neighbourhood
• The (Super)Wasp factory finds 10 new planets in the last 6 months
• GCSE astronomy: A rising star for schoolchildren
• Magnetic substorms from ground and space
• Medical X-ray technique unveils the Sun's corona
• Two supernova factories found in the Milky Way
• Old galaxies stick together in the young universe
• Stars burst into life in the early universe

At the end of the meeting, it was announced that next year's National Astronomy Meeting is to be held at the University of Hertfordshire. Many of us are looking forward to it already!

Cosmic visions is a European Space Agency initiative to plan missions to be launched between 2015-2025. And there is no shortage of ideas!

Missions include:

• XEUS - the next generation X-ray telescope, designed to look at the hottest and most violent regions of space
• LISA - a mission to detect and measure gravity waves, emitted when massive objects violently collide
• SPICA - a mission to explore how stars and planets form
• PLATO aims to search for planets orbiting distant stars
• TANDEM will scrutinise Saturn's moons Titan (an Earth-like organic-rich world) and Enceladus.
• LAPLACE would explore Jupiter's moon Europa - and world covered in ice but with a water ocean beneath the surface
• MARCO-POLO is a mission to return a sample from a near-Earth asteroid, which could be key if we ever need to deflect an asteroid in the future
• CROSS-SCALE plans to study astrophysical plasma's in all regions of space.
• SPACE - a mission to study how the Universe evolved in infrared wavelengths
• DUNE - designed to study dark matter and dark energy in the universe

Not all these missions will become reality.

Which ones would you choose?

The above banners have been taken from the ESA website.

May is a great month for viewing planets!

The five major planets in our solar system are all easily visible to the unaided eye, which is why they have been known about since antiquity. If you have never seen a planet before, this is a good month to start looking for them. The only planet that cannot be seen this month is Venus, which is too close to the blindingly bright Sun to spot.

The sun sets at 20:45 BST mid-month, with nautical twilight (when the Sun falls to 12 degrees below the horizon) ending at 22:24 BST - although it does not get astronomically dark until 23:52 BST.

Even though it is still twilight at 21:45 BST, this is the best time to look for the planet Mercury.

Because Mercury is the closest planet to the Sun, orbiting the Sun in just 88 days, it is always pretty close to the Sun in the night sky. But, every 3 months there are a brief few days when Mercury gets to the extreme of its orbit - this is the time to spot it in the evening sky after sunset.

Look low in the bright north-western sky to find Mercury, the best times being between the 5th and 10th of May, about 45 minutes after sunset - that is the time when the sky is dark enough to see Mercury, and Mercury has another hour yet before it follows the Sun below our horizon.

The ideal date to look is on the 6th of May, when Mercury is just to the left of the beautifully young crescent Moon. Having a flat clear horizon also helps, so gazing out to sea looking west is the best way to spot the planet.

Mars is visible towards the west throughout the evening, easily recognisable thanks to its red colour. The Moon acts as a useful guide on the 10th of May, when it is just to the left of Mars.

Saturn is visible until the early morning, always in the western sky. Through even the smallest telescope, you can see the rings that surround this majestic planet. On the 12th, the Moon moves into position just below the planet.

And finally, at around midnight, the planet Jupiter is rising in the east, with the Moon beside it on the 24th and 25th.

The NASA Phoenix mission to Mars has landed on the surface of Mars intact!

Previous missions have shown large amounts of subsurface water ice in the northern arctic plain. The Phoenix lander targets this region and will use a robotic arm to dig through the protective top soil layer to the water ice below and ultimately, to bring both soil and water ice to the lander platform for sophisticated scientific analysis.

Controllers were able to receive data for a minute after the landing, enough data to confirm that the lander was tilted by just one quarter of a degree!

"In my dreams, it couldn't have gone as perfectly as it went tonight," says Barry Goldstein, the Phoenix project manager. "I'm in shock. We had all the signals. Everything."

"It's in a nice flat place, very safe and happy," says Peter Smith, the Phoenix principal investigator.

An animation showing the landing is available here, and the first image back will be available on APOD.

The main activity of the mission controllers immediately after launch was phoning and texting friends and family, updating them on their success!

The lander meanwhile will wait for 20 minutes for the dust to settle, before opening its solar panels. The Mars Odyssey spacecraft will next fly over the landing site in about 2 hours time, and it will be then (around 02:00 GMT) that the first pictures from the surface of Mars may be sent back to Earth.

The first photographs from Mars Phoenix are now available at:

• BBC News
• NASA Phoenix
• University of Arizona

The decent of the Mars Phoenix lander (and its parachute) was captured by the Mars Reconnaissance Orbiter HiRISE camera... And what an amazing photograph.

Note that, although it looks like the Phoenix is landing inside the crater, it is actually about 20km in front of the crater.

The Space Shuttle Discovery launched yesterday towards the International Space Station, with not only the Japanese module of the Space Station, but also spare parts for their toilet! (see the full story on the BBC News).

We can actually see the International Space Station fly overhead - it is very bright indeed. And tonight (the 1st of June), for one night only, we can actually see the Space Shuttle Discovery fly over Europe just a minute after the station, as it plays catch-up! To find out when and where to look, see SpaceWeather.com.

Some lucky observers in the UK managed to see both the Space Shuttle and it's separated external fuel tank last night - see this link. Unfortunately, it was cloudy here in Greenwich last night.

For up-to-the-minute updates on the latest mission to the Space Station, see Spaceflightnow.com.

It is always worth admiring the night sky, since you may never know what you will see. If you are lucky, you might just see a fireball burning through the night sky!

Which is exactly what happened to observers in western Canada just a few days ago, as reported by Andy Barlett via SpaceWeather.com (as shown in his image, right).

And better still, it has been caught on video...

See also:

• Andy Barlett's video available as an AVI movie from at SpaceWeather.com, or as a YouTube video;
• Or the view from a police car (shown above);
• From a car park CCTV camera;
• Or from a fisheye lens;

Although such bright meteors are rare, I did see a fireball of a similar brightness myself, in December 1994. So it is always worth looking!

The Meridian laser marks the route of the Greenwich Meridian by night in a northerly direction from the Observatory at Greenwich.

People often ask us: from how far away it can be seen? Not surprisingly, the answer to this is highly dependent on the weather and the atmospheric conditions at the time. But under good conditions it's a lot further than you might imagine. The furthest at which it has been reliably sighted with the naked eye is at a distance of 36.7 miles from Periwinkle Hill a couple of miles to the south of Royston.

In order to see the beam when more than a few miles away from the Observatory, you need to be standing directly beneath it (and definitely no more than a few hundred yards or so to either side), and looking south, back along the beam towards Greenwich. There are a number of elevated sites in Cambridgeshire to the north of Royston with good horizons to the south. My good friend and former colleague Robin Catchpole visited one such a site at Lolworth (a small village just to the south of the busy A14) at the end of last year. Although not visible to the naked eye, Robin was able to see the beam with his binoculars and photograph it with his compact digital camera. During the first weekend in January, when much of southern England was enjoying clear days and frosty nights, I joined Robin on the Saturday evening to go laser hunting slightly further to the north in the village of Bluntisham at a distance of 60.5 miles. Once again, the laser was visible but once again, only though binoculars ... and here's the picture that Robin took to prove it.

At this sort of distance from the Observatory, the visibility of the beam is highly dependent on the state of the atmosphere at all points along its route and unfortunately for us, within just a few minutes of our arrival the beam disappeared from view. Under exceptional conditions, I would hazard, that it would be possible to see it from as far north as Bluntisham with the naked eye.

If you want to go laser hunting yourself, you will need either a suitable Ordnance Survey (OS) map and or a GPS. Because of the way the maps are constructed, the Meridian doesn't run vertically up the page. Instead it curves slightly from right to left. Although most OS maps do not specifically mark the Meridian, it is possible to determine more or less where it runs by making use of the graticules (the small blue crosses) that are generally marked every 5' of latitude and longitude on the Landranger maps - the ones with the purple covers. What you will need to do, is look along the top edge of the map where the longitude scale is marked until you find 0^o and then look down the page for the corresponding graticules. What you may also find useful (especially if you need to use binoculars), is a magnetic compass to help orientate yourself in approximately the right direction. The Periwinkle Hill site can be located fairly easily even if you don't have an OS map or GPS as the beam passes almost directly over the transmitting tower that is located there.

From time to time, we have to check and adjust the alignment of the Meridian laser. Rather conveniently, back in 1824, the sixth Astronomer Royal John Pond had an Obelisk erected at Pole Hill some 11 miles from the Observatory on the then Greenwich Meridian.

Its purpose was to provide an additional alignment check for the Transit Telescope that was then in use. Having initially adjusted the telescope to the Meridian from observations of the circumpolar stars, Pond lowered it to the horizon to determine exactly where the obelisk should be built. By this means, he was able to position it with an accuracy of about ± four inches. The Meridian defined by this particular telescope is known as the Bradley Meridian and is the Meridian used (for historic reasons) by the Ordnance Survey (OS) on its maps. It predates the current Greenwich Meridian, which runs about six metres further to the east at Greenwich and is defined by the Airy Transit Circle (ATC) of 1850. An OS trig point was erected adjacent to the Pond Obelisk and very close to present Meridian in the 1930s, and this is where I will be heading later this month.

From there I will be able to talk with my colleagues back at Greenwich and tell them in which direction (east or west) they need to move the beam. The beam will also be adjusted vertically so that it just grazes or clears the tops of the trees, thereby ensuring maximum visibility for those places further to the north. So if early one winter's evening, you think that you can see the beam moving around a bit, your eyes probably won't be deceiving you ... it will simply be us doing one of the regular adjustments that are sometimes needed!

For those who want a bit of info about the laser itself, it's a Millennia VS Diode-Pumped, cw Visible Laser. It has a wavelength of 532 nm and an output power > 5W. The laser unit is located beneath the Airy Transit Circle and 'fired' along the Meridian from above via a fibre optic as can be seen in the picture above.

We took advantage of the change in the weather yesterday afternoon to check the alignment of the Meridian laser (see Monday's posting). Arriving in Chingford at around 17.00, we had completed our adjustments by 17.30. The picture below was taken about ten minutes later.

With next Monday's new moon, comes not only Chinese New Year, but also an annular eclipse of the Sun. Annular eclipses are more common than total eclipses, but fewer people are aware of their existence. Both occur when the Moon passes directly in front of the Sun. But in the case of an annular eclipse, the disc of the Moon is not large enough to cover the Sun completely. The last annular eclipses to be visible from Britain were on 31 May 2003 and 8 April 1921. The next is not due until 23 July 2093. None of next Monday's eclipse will be visible from Britain and it will probably be seen by relatively few people - not least, because most of its path is over the ocean. The picture below was taken in Spain by Darren Baskill during the annular eclipse on 3 October 2005.

With speculation about life on Mars making the news once again, it seems timely to look back and see what was being written on the subject 50 years ago. Back in 1959, the space age was very much in its infancy and America had only recently entered the space race with the launch of Explorer 1 in January 1958. The select committee on astronautics and space exploration was set up a few weeks later on 5 March during the 85th congress. A flurry of reports were soon being tabled, including the special staff report: Space Handbook: Astronautics and its Applications, which was submitted on 29 December and published in 1959. The extract below shows the state of 'official' thinking about life on Mars at that time.

'Bleak and desert like as Mars appears to be, with no free oxygen and little, if any, water, there is rather good evidence that some indigenous life forms may exist.

The seasonal color changes, from green in spring to brown in autumn, suggest vegetation. Recently Sinton has found spectroscopic evidence that organic molecules may be responsible for the Martian dark areas. The objections raised concerning differences between the color and infrared reflectivities of terrestrial organic matter and those of the dark areas on Mars have been successfully met by the excellent work of Prof. G.A. Tikhov and his colleagues of the new Soviet Institute of Astrobiology. Tikhov has shown that arctic plants differ in infrared reflection from temperate and tropical plants, and an extrapolation to Martian conditions leads to the conclusion that the dark areas are really Martian vegetable life'

This picture of Mars was taken by Tony Sizer through our 28-inch refractor back in November 2005.

Although Mars will not be visible in the evening sky until much later this year, Invaders of Mars is showing daily in our planetarium until 17 May.

Back on New Year's Eve you may recall, an extra second, known as a leap second, was added to the day to compensate for our slowing Earth. Leap seconds are added when necessary at the end of either June or December. The International Earth Rotation and Reference Systems Service (IERS) has since announced that there will be no positive leap second added this June.

Since the system of adding leap seconds was introduced back in 1972, a total of 24 leap seconds have been added. The three most recent being at the end of December 1998, 2005 and 2008.

The Earth's rotation is monitored by a variety of means, including satellite laser ranging (SLR). The British facility is located in the old solar dome at Herstmonceux and is operated by NERC (Natural Environment Research Council).

In a nutshell, a laser beam is fired at a satellite to which a retro-reflector has been attached. By measuring the time it takes for the beam to return, it is possible to measure where the base station is relative to the satellite and therefore detect fluctuations in the Earth's rotation as well as tidal movements of the land (due to the pull of the Moon). Interestingly, the solar building was not only the first of the new domes at Herstmonceux to become operational following the move from Greenwich; it is the only one where active research is still carried out.

In 1939, Harold Spencer Jones, our tenth Astronomer Royal wrote a paper titled: Is there life in other worlds? Spencer Jones was not only well regarded and honoured by his peers, he was also a great populariser of astronomy. So it is perhaps no surprise that in 1940, he published a popular book under the title: Life on other worlds. It gives 'a balanced popular survey of current astronomical knowledge and speculation' at that time and was described by the novelist HG Wells as a 'charmingly lucid book'.

So what did Spencer Jones have to say in his chapter Mars - the planet of spent life? He started with some of the practicalities of observing Mars and obtaining images, before going on to look at the work of Schiaparelli and the later work of Lowell. Schiaparelli was the first to observe the so called Martian Canals, whilst it was Lowell who worked up the theory that they had been created by intelligent life. Discarding the evidence on which Lowell based his conclusions, Spencer Jones went on to say that 'it is almost certain that there is some sort of vegetation on Mars'. Spencer Jones' popular books all went through many editions. If you are one of those who likes to browse through a physical rather than an electronic book, there are cheap second-hand copies available on the internet.

In the news this week you may have read that the Monument near London Bridge has just reopened after restoration work. This large column was erected next to the Thames as a memorial to the Great Fire of London of 1666, and was completed in 1677. But what is not so well known is that its designers, Christopher Wren and Robert Hooke, intended it to be used as a telescope.

The Monument was designed as a type of telescope known as a zenith telescope, used to observe stars that pass directly overhead. Wren and Hooke hoped that by looking at one star in particular they might be able to detect stellar parallax - a change in the position of an observed object caused by a change in the observer's position. This was something that should be observed if the Earth was moving around the Sun, but astronomers had not yet been able to detect it. In fact, it was only in the nineteenth century that stellar parallax was finally observed.

Here, the whole structure was the telescope. The observer sat in a room in the basement and looked up through the 'tube' created by the spiral staircase. The flaming urn on top had a hinged lid that opened for viewing. Sadly, it didn't prove to be up to the job because it expanded and contracted in different temperatures and swayed in the wind. Try not to think about that if you go up it!

I'll be blogging about telescopes regularly throughout the International Year of Astronomy 2009, revealing some of the stories behind real and imaginary instruments from the National Maritime Museum collections and elsewhere.

The Monument, from John Stow, A survey of the cities of London and Westminster

This is an exciting day for astronomy as the Space Shuttle Atlantis and its crew of seven astronauts prepare to launch into orbit and rendezvous with the Hubble Space Telescope. Hubble has been in orbit for 19 years now, sending back a constant stream of images and data which have revolutionized almost every field of astronomy. But almost two decades in space have taken their toll and the telescope is in desperate need of refurbishment.

Having matched orbits with Hubble 560km above the Earth, Atlantis will grasp the bus-sized telescope with its robotic arm and pull it into the shuttle's cargo bay where the astronauts can carry out their repairs and upgrades. This will be no easy task and will require no less than five gruelling spacewalks - uncomfortable hours spent in the confines of a spacesuit trying to manoeuvre phone-booth sized pieces of equipment into position and perform precision tasks whilst wearing thick protective gloves.

The shuttle crew have been in intensive training for this mission for months but even so the trip is not without personal risk. Since the tragic loss of the shuttle Columbia in 2003 NASA has only allowed its shuttles to venture into orbits from which they could reach the International Space Station in an emergency. Hubble is 200km higher than the ISS and the shuttle doesn't carry enough fuel to reach it should anything go wrong but, in recognition of Hubble's scientific importance, NASA have waived this rule for the current mission. Instead Atlantis' sister craft Endeavour will be waiting on the launch pad in case a rescue mission is needed.

If all goes well, Hubble will have two brand new state-of-the-art instruments fitted, bringing it bang up to date with 21^st Century technology and expanding its science capabilities enormously. The Atlantis crew will also repair three malfunctioning instruments and replace other old and failing equipment. The refurbished Hubble should enjoy a healthy old age lasting well into the next decade and keeping astronomers busy until the launch of its successor, the James Webb Space Telescope, in 2013.

Today (9 October 2009) two unmanned NASA spacecraft will impact the Cabeus crater in the lunar South Pole, in the final stage of the LCROSS mission (Lunar Crater Observation and Sensing Satellite).

The first spacecraft, the 2200kg Centaur rocket stage, will hit the Moon at about 4800 km/h or twice the speed of a bullet, throwing up debris plumes to an expected height of 10km above the lunar surface, visible from Earth-based telescopes 10-12" and larger.

The smaller 'shepherding spacecraft' will follow, descending through the debris plume to impact 4 minutes later. As it travels through the plume, onboard spectrometers will monitor the chemical components of the debris, looking for water, hydroxyl compunds, salts, clays and organic molecules, and relay this information back to Earth before impact.

Projected first impact is currently 12:31 BST.

You can watch the impact live online on NASA TV.

Image: Artist's rendering of the LCROSS spacecraft and Centaur separation (NASA).

NASA's infra-red Spitzer Space Telescope has identified a vast, diffuse and all-but invisible new ring around Saturn, tilted at 27º from the main ring plane. The discovery was announced on 6 October 2009.

The huge disk of material starts about 6 million km away from the planet and extends at least another 12 million km outward, with a vertical thickness of about 2.5 million km. However, despite its size the ring is very tenuous, composed of highly diffuse ice and dust particles. This material is thought to have come from Phoebe, one of Saturn's most distant moons, as a result of small impacts on the moon's surface. This material may also solve the long-standing puzzle of the two-tone moon Iapetus, light on one side and dark on the other. It's thought that the dark face is caused by dust from the ring moving inwards towards Saturn and impacting the moon on one side.

Image: Artist's impression of new giant ring around Saturn (infrared view) (NASA)

View beautiful images of Saturn's other rings from the Cassini-Huygens mission, recently on display at the Royal Observatory, Greenwich.

On Friday (5 Feb 2010) NASA released the most detailed images yet taken of Pluto. The photographs from the Hubble Space Telescope (HST) show the dwarf planet's icy, mottled surface undergoing seasonal changes - the surface has become much redder and the illuminated northern hemisphere is getting brighter. The changes are probably due to surface ice sublimating to gas on the sunlit pole and then freezing again on the opposite pole as Pluto moves into the next phase of its 248-year seasonal cycle. Read the full story on NASA's website.

Image: NASA / HST

Read the ROG's Pluto fact file

NASA announced on 3 February that it is extending the international Cassini-Huygens mission to explore Saturn and its moons to 2017, with a budget of $60 million per year.

This is the second extension to the mission which was originally launched in October 1997. Dubbed the Cassini Solstice Mission, this seven-year extension will allow scientists to study seasonal and other long-term weather changes to the ringed planet and its moons as it moves from winter to summer. It also will allow continued observations of Saturn's rings and magnetosphere.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency (ESA) and the Italian Space Agency. JPL manages the project for NASA's Science Mission Directorate in Washington. The Cassini orbiter was designed, developed and assembled at JPL.

Read the full story on NASA's JPL website. Further Cassini information is available at www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

Image: Looking down on Saturn's northern hemisphere, Cassini uses false-colour imaging to reveal different layers of cloud. PIA09212. © NASA/JPL/University of Arizona. View the ROG's online gallery of Cassini-Huygens images, Visions of Saturn.

NASA's Solar Dynamics Observatory (SDO) is currently scheduled for launch tomorrow (10 February 2010) from the Kennedy Space Center in Cape Canaveral.

NB launch actually took place on Thursday 11 February, 10:23 EST (15:23 GMT).

SDO is a powerful solar observatory which will look deep into the Sun and record images at 10 times higher resolution than HDTV. It is the first mission to be launched for NASA's Living With a Star (LWS) Program, designed to understand the causes of solar variability and its impacts on Earth. It is hoped that it will reveal how solar storms erupt, help us understand the Sun's influence on Earth and Near-Earth space and also help scientists build effective models for space weather forecasting.

The SDO spacecraft will orbit the Earth at a distance of about 22,300 miles, relaying its readings instantly to a ground station in New Mexico.

Image: Artist's impression of SDO (NASA)

Spring - perhaps the most eagerly-awaited of seasons, when days start to lengthen, temperatures to rise, weather to improve and all of nature to burst into bud and blossom as earth throws off the cold grip of winter. The vernal season has inspired music from Vivaldi to Elvis Presley ('Spring Fever') and poetry including Robert Burns's hilariously bawdy 'Ode to Spring' (1794).

But when does spring actually start, in the northern hemisphere at least? Is it the first day of March, or the date of the vernal equinox around 20/21 March, or even sometime in early February with the equinox marking the middle of the season not its start? It all depends very much on who you ask, and on your definition of spring.

There are three main different ways of defining spring - astronomical, meteorological and phenological.

Astronomically, the four seasons centre around the equinoxes and solstices. However, there is disagreement between those who see the equinox/solstice as the start of the season and those who hold that it represents the middle of the season. (For example, the summer solstice is when the sun is at its highest and solar radiation received by the earth's surface is greatest, so some argue that logically this must mark the mid-point of summer not its start.) The East Asian and Celtic calendars certainly see the vernal equinox as mid-spring, with the season starting in early February. However, the popular view of the 20/21 March spring equinox as the start of the season is likely to persist, at least in the UK.

By contrast, meteorologists tend to divide seasons into periods of three whole months based on average monthly temperatures, with summer as the warmest and winter as the coldest. On this basis, for most of the northern hemisphere the spring months are usually March, April and May, and so by this definition spring starts on 1 March.

The third way of defining spring is to use what are known as phenological indicators. These cover a range of ecological/biological signs such as the appearance of the first daffodils, crocuses and hyacinths, the budding of trees, the nesting of birds and the emergence of animals from winter hibernation. These events of course are greatly influenced by weather and climate, and so changing climate could cause spring to start earlier than the standard astronomical or meteorological definitions.

So when does spring start? You can decide. Looking out of the window today, I'd be cautiously inclined to agree with the meteorologists that it's already here.

Images: Equinoxes by Greg Smye-Rumsby; Daffodils in the grounds of the National Maritime Museum, Royal Observatory in background.

Then this coming Sunday residents of the UK will lose an hour's sleep to gain an extra hour's daylight in the evenings. Longer evenings are not of course good news for everyone - amateur astronomers will have to stay up later and later to get the darkness needed for observing.

So at 1.00 am GMT on Sunday 28 March clocks in the UK officially move forward by an hour as civil time changes from Coordinated Universal Time (almost identical to Greenwich Mean Time) to British Summer Time or BST.

Which means that though it's definitely now spring, as of next week we'll be in British Summer Time, which this year lasts until 31 October when by most counts we'll be in mid-autumn... it's no wonder we get confused about the seasons.

In search of a bit more clarity, why not listen in to David Rooney discovering more about British Summer Time or have a look at our Spring Forward: 100 Years of British Summer Time page?

The Royal Observatory (ROG) has won an international award for its Solar Stormwatch website, www.solarstormwatch.com.

The website picked up the award in the Innovative or Experimental category at the 2010 Best of the Web Awards, presented at the international Museums and the Web conference held in Denver, USA late last week. 

Solar Stormwatch was built in-house by the ROG's Digital Media team working in close collaboration with The Rutherford Appleton Laboratory and Galaxy Zoo (Oxford University). It provides tools and tutorials that actively encourage the general public to help scientists analyse data from NASA's STEREO mission, which was launched in 2006 to conduct 3D studies of the Sun.

The principal aim of the website and resulting research is to help spot and track solar storms across space and to create a user-generated space weather forecast. Best of the Web judges commented that the Museum's Solar Stormwatch made 'excellent use of crowd-sourcing to advance scientific discovery' and that it not only connects users, but engages them to do something of real value.

Solar Stormwatch is the latest in the line of solar science research projects to come out of the Royal Observatory, stretching back to the very first Astronomer Royal John Flamsteed (1646-1719). Flamsteed set up a solar observatory at Greenwich and his observations were later studied by Royal Observatory employee Edward Walter Maunder (1851-1928), who showed that there had been an exceptionally low occurrence of sunspots between 1645 and 1715, a period now known as the Maunder Minimum.

Museums and the Web is an annual conference usually staged in the US and attracting over 400 delegates from 20 or more countries. The conference is recognised across the cultural sector as the pre-eminent forum for the discussion, debate and presentation of the latest ideas and research from cultural institutions using the web.

The Best of the Web awards have been presented at the conference since 1997, and are awarded in recognition of outstanding achievement in heritage website design, research and delivery. This year, 87 sites were nominated from a range of cultural heritage institutions worldwide. A full listing of this year's Best of the Web winners is available at http://conference.archimuse.com/forum/congratulations_mw2010_best_web_winners.

Related posts

Join the hunt for solar storms

On 29 September 2010 a team of astronomers announced the discovery of an Earth-sized exoplanet Gliese 581g in the habitable ('Goldilocks') zone of a nearby red dwarf star. The planet has a mass three to four times that of the Earth, which suggests that it is probably a rocky planet with enough gravity to hold on to an atmosphere. Altogether the findings could make Gliese 581g the most Earth-like exoplanet yet found, and the strongest contender so far for a potentially habitable planet - one that could sustain life.

Gliese 581g is tidally locked to its host star, with one side always facing the star in perpetual daylight. The most habitable zone on the planet would be the 'terminator' - the line between shadow (night) and light (day).

The host star, Gliese 581, is located 20.5 light years from Earth in the constellation Libra. Among the six planets so far discovered orbiting the star, two others (planets c and d) lie at the edges of the habitable zone, and some astronomers still think planet d may be habitable if it has a thick enough atmosphere.

The new findings have been made by the Lick-Carnegie Exoplanet Survey, led by Steven Vogt (University of California, Santa Cruz) and Paul Butler (Carnegie Institute, Washington). They are based on 11 years of observations of Gliese 581 at the W.M. Keck Observatory in Hawaii, made using the HIRES spectrometer on the Keck I Telescope. This allows precise measurements of a star's radial velocity, which can reveal the presence of orbiting planets whose gravitational pull causes periodic changes in the host star's radial velocity.

The team's findings are to be published in The Astrophysical Journal and have been posted online at arXiv.org.

Steven Vogt believes that the surprising speed with which they have been able to find a nearby star system with a potentially habitable planet means that there could be 'tens of billions of these systems in our galaxy'.

Find out more

• Newly Discovered Planet May Be First Truly Habitable Exoplanet (Science Daily)
• Gliese 581 g (Wikipedia)

Life, but as we know it? Sci-Fi-London Oktoberfest

If you're interested in the possibility of life on other planets, join us on 14 October when the Royal Observatory, Greenwich teams up with Sci-Fi-London for a special night investigating extraterrestrial life in science, fiction and comedy. All ticket holders will see our exclusive new planetarium show Astrobiology and will also have the chance to sign up for a range of other activities on a first-come first-served basis including a preview screening of Gareth Edwards' new sci-fi movie Monsters, an adventure game around the Observatory, telescope viewing and a lighthearted tour of the Observatory's meteorite collection. Find out more

Cost: £15
Book online or call 020 8312 6608.

Astrobiology: the hunt for alien life (5-week course)

If you want to study life beyond Earth in more detail, why not sign up for this short course with Dr Lewis Dartnell. 'Astrobiology' is a brand new field of science, encompassing research into the origins and limits of life on our own planet, and where life might exist beyond the Earth. But what actually is 'life' and how did it emerge on our own world? And where else might provide conditions suitable for life, either in our own solar system or among the exoplanets so far discovered?

Cost: £50
Book online or call 020 8312 6608.

On 20 October 2010, Comet Hartley 2 (103P/Hartley) will pass within about 11 million miles (0.12 AU) of the Earth. This will be its closest approach since it was discovered in 1986, and one of the closest approaches of any comet in the last few hundred years. At this time, the comet should be visible in the constellation Auriga.

Image: Hartley 2 in Cassiopeia, 28 Sep 2010 (crop). Credit: NASA/MSFC/Bill Cooke, NASA's Meteoroid Environment Office.

Astrophotography opportunity

There will be a great opportunity for astrophotographers between 7-9 October as the comet passes close to the beautiful Double Cluster in Perseus. It is then expected to pass near the open cluster NGC 1528, also in Perseus, by 14 October. Don't forget to enter your photographs of the comet in the 2011 Astronomy Photographer of the Year competition which opens in January.

Viewing Hartley 2

Meanwhile over the next few days Hartley 2 should become increasingly visible with the aid of binoculars or a small telescope, and possibly even to the naked eye.

The comet is diffuse (its light is spread out over a wide area) so to see it you need a dark sky location free of city lights. The technique of averted vision - looking slightly to one side rather than straight on - is also helpful in locating faint objects. The comet will probably appear as a grey smudge of light or as a faint, fuzzy star. Heavens-Above.com has a useful locator chart.

After 10 October the Moon will start to make it harder to see the comet, so until 20 October best viewing time will be after moonset.

EPOXI mission

On 28 October, the comet will reach perihelion (closest approach to the Sun). Finally, on 4 November, NASA's EPOXI mission (previously Deep Impact) will fly by the comet, with a closest approach of 435 miles.

It's estimated that Hartley 2 will next come to perihelion in 2017, around 20 April.

21 October 2010 - Astronomers have confirmed the discovery of the most distant astronomical object yet known - the galaxy UDFy-38135539, over 13 billion light years from Earth.

This also makes it the furthest back in time scientists have been able to see, to the early Universe just 600 million years after the Big Bang during what's known as the epoch of re-ionisation. During this period the fierce UV light from the first populations of stars would have stripped electrons from the opaque hydrogen fog which filled much of the young cosmos, gradually making the universe transparent.

However, it appears that the light from UDFy-38135539 would not have been strong enough on its own to clear the hydrogen fog surrounding it, which indicates that there must be other fainter, less massive galaxies in its neighbourhood which helped clear the fog.

UDFy-38135539 was spotted in the area of space known as the Hubble Ultra Deep Field, a small region of space in the constellation Fornax. The galaxy was one of a number of interesting candidates for study found in a 48-hour exposure image acquired with Hubble's new Wide Field Camera 3 in 2009. Astronomers used the SINFONI spectrograph instrument attached to the Very Large Telescope (VLT) on Mount Paranal to measure the exact distance to UDFy-38135539. The spectrograph is able to determine the redshift of the light from the galaxy - the extent to which it has been stretched by the expansion of the Universe.

The findings were published today in the journal Nature. The lead author of the paper is Matt Lehnert of the Observatoire de Paris.

Hayabusa probe brought back asteroid dust from Itokawa

16 November 2010 - After five months of testing, Japanese scientists have confirmed that particles brought back by the Hayabusa probe in June this year are indeed from the 300 million km-distant asteroid 25143 Itokawa. This is the first time asteroid samples have been brought back to Earth, and only the fourth set of extra-terrestrial samples returned by spacecraft.

The Hayabusa space probe spent three weeks in orbit round the 500m-long asteroid in 2005. Although the craft failed to fire a pellet into the asteroid's surface as planned, it did seemingly manage to disturb the asteroid's surface enough to stir up dust which was captured by Hayabusa - about 1500 particles in all. Numerous tests carried out by JAXA (the Japanese space agency) have identified minerals including olivine, pyroxene, plagioclase and troilite.

The Royal Observatory, Greenwich will be showing a Hayabusa planetarium show next year as part of our forthcoming 'Impact' season.

Read more about asteroids in our fact file.

Youngest 'nearby' black hole

Astronomers in the US believe they have found a 50 million-year-old 'baby' black hole in the relatively nearby M100 galaxy (still 47 billion, billion miles from Earth).

Supernova remnant SN 1979C is the product of a blast observed just 30 years ago, and has been investigated by several telescopes including most recently NASA's Chandra X-ray Observatory. All of these show that it is a bright source of X-rays which have remained steady for 15 years, strongly suggesting that it is a black hole. It probably formed when a star 20 times more massive than the Sun collapsed in on itself at the end of its life.

However, it is also possible that the source of the X-rays could be a young, fast-spinning neutron star with a strong wind of high-energy particles.

Read more about black holes in our fact file.

And finally... Tycho Brahe exhumed (again)

From dying stars to dead star-gazers - the body of the 16th-century Danish astronomer Tycho Brahe is being exhumed in Prague in an another attempt to determine the cause of his death.

The court mathematician, alchemist and astronomer who catalogued over 1000 stars led a colourful life, including a duel in which he lost his nose. It's thought by some that high levels of mercury found in a previous exhumation may have resulted from deliberate poisoning, and suspicion has pointed to his assistant Johannes Kepler or to the Danish king Christian IV with whose mother Brahe allegedly had an affair.

Scientists also hope to determine the kind of metal Brahe's nose prosthesis was made from.

Read more about Tycho Brahe and his star maps in our fact file.

19 Novmber 2010 - Over the past 15 years scientists have found nearly 500 planets outside our solar system, but till now all of these have been within our galaxy - the sheer distances involved preclude detection of planets outside the Milky Way. But now astronomers have identified a planet orbiting a star that originally belonged to a separate dwarf galaxy, one which was swallowed up by the Milky Way some 6 to 9 billion years ago.

The new-found planet HIP13044b is about 2000 light years from Earth, is at least 1.25 times more massive than Jupiter, and orbits close to its star with an orbital period (year) of just 16.2 days. Researchers say the planet would have been formed in its solar system's early days, prior to incorporation into the Milky Way.

The planet's star HIP13044 (appearing in the southern constellation Fornax) has passed its red giant phase and is nearing the end of its life, so it offers an intriguing glimpse into what the last years of our own Solar System may look like. The star is rotating relatively fast, which may be a result of swallowing its nearest planets during the red giant phase. One remaining puzzle is that the star does not appear to contain the heavy elements which are usually thought to be needed for planet formation.

Researchers discovered the planet using the 'radial velocity method', using a telescope-connected spectrograph at the ESO's La Silla facility to detect the small wobbles in a star caused by an orbiting planet's gravitational pull.

26 November 2010 - NASA's Cassini probe has scooped oxygen from the atmosphere of Saturn's second largest moon, the icy Rhea. This is the first time the gas has been directly seen in the atmosphere of another world, though scientists have previously used telescopes to detect oxygen on other moons and planets, including Jupiter's moons Europa and Ganymede.

In a flyby in March, Cassini's instruments found an extremely thin atmosphere - or strictly exosphere - with tiny concentrations of oxygen and carbon dioxide. At a peak density of around 20 billion molecules per cubic metre, the density of oxygen in Rhea's exosphere is about 5 million million times lower than that found in Earth's atmosphere.

Rhea's exosphere is maintained by a constant stream of high-energy particles bombarding the moon's icy surface, breaking water molecules and forming oxygen. The carbon dioxide may also be produced by particle impacts, or could come from dry ice trapped within the moon or from carbon-rich meteor deposits.

Team leader Dr Ben Teolis believes that there could be billions of similar exospheres throughout the galaxy. One strong candidate is Saturn's moons Tethys, which Cassini is due to fly by in December 2011.

The Cassini mission is a joint project of NASA, the European Space Agency (ESA) and the Italian Space Agency (ASI). Cassini arrived at Saturn in 2004 after a seven-year voyage across billions of kilometres of space, and its mission has been extended until 2017 when it will destroy itself by plunging into Saturn's atmosphere.

See a selection of beautiful images from the Cassini-Huygens mission in our Visions of Saturn pages.

Three recent discoveries with implications for the search for other Earth-like planets and for life in the Universe.

Red dwarfs increase possibility of other Earths

The universe may contain three times more stars than has been previously thought. New observations using the Keck telescope in Hawaii showed that galaxies older than ours may contain 20 times as many red dwarfs, which are older and less bright than the Sun.

This also greatly increases the estimated number of planets in the universe and therefore the likelihood of other 'Earth-like' worlds. Red dwarfs tend to be at least 10 billion years old, allowing plenty of time for complex life to evolve on planets in their system.

The discovery, led by a team from Yale University, also reduces the amount of 'dark matter' needed to explain the 'missing mass' of the universe.

First known atmosphere round 'Super-Earth' exoplanet measured

Scientists at the Harvard-Smithsonian University Centre for Astrophysics have been able to measure the atmosphere of a 'Super-Earth' exoplanet for the first time. The planet - GJ1214b - is 40 light years distant, is about three times the size of Earth and seven times the mass, and is the first of its kind around which an atmosphere has been detected. Measurements using the 'transit method' seem to show that it does not have a hydrogen or helium atmosphere, but further work will be needed to determine whether it has a thinner and steamier atmosphere or a thicker, cloudier one.

See related post New exoplanet may be habitable (1 Oct 2010)

'Extremophile' bacteria break the mould for life

Up till now, it's been thought that all life on Earth must contain the six elements carbon, oxygen, hydrogen, nitrogen, sulphur and phosphorus. But an Arizona State University and NASA team have found a bacterium in a California lake that is able to substitute the usually-poisonous element arsenic for phosphorus.

The discovery of a separate 'tree of life' would have major implications in the hunt for alien life in the Universe. However, the researchers found that the bacterium still thrives best in a phosphorus environment, meaning that it is probably simply an unusual branch of the known tree of life rather than a member of an entirely different one.

The initiative, launched in February by the Royal Observatory, Greenwich (ROG), in partnership with the STFC Rutherford Appleton Laboratory and the Zooniverse Citizen Science Project, makes it possible for anyone with internet access to get involved in the latest solar research by helping to spot and track storms as they erupt from the Sun. These collective measurements enable scientists to forecast the arrival of storms far enough in advance to issue effective pre-emptive warnings for the first time.

Solar storms, power grids and aurora

The latest storm identified by the project is predicted to hit Earth at 07.32 GMT on Monday 13 December. Solar storms have the potential to interfere with communication satellites, upset GPS navigation systems and also pose a health risk to astronauts on the International Space Station. In severe cases they can even knock out entire power grids causing widespread disruption here on Earth.

On a gentler note, the particles making up a solar storm can produce beautiful displays of the Northern and Southern Lights as they collide with the Earth's upper atmosphere. Scientists are not overly concerned about the effects of the current storm, but the early warning provided by Solar Stormwatch will allow precautionary measures to be put in place.

Predicting storms

Dr Marek Kukula, Public Astronomer at the ROG, says, 'Solar Stormwatch is special in that it harnesses public interest in astronomy to provide data that is invaluable to scientists. The more people that take part in "stormwatching" the more we will learn, and the fact that the volunteers' work has now enabled us to predict when a storm will hit the Earth is a significant milestone, not just for the project, but for science as a whole'.

Solar Stormwatch is the latest chapter in a long history of solar research at the Royal Observatory, Greenwich, dating back to the 1870s when the Observatory housed a photoheliograph - a telescope that took daily photos of the Sun to track sunspots. Visitors to the Royal Observatory today can see this telescope housed in the Altazimuth Pavilion.

Take part

Join the hunt for solar storms at the Solar Stormwatch website. Help scientists spot explosions on the Sun and track them across space to Earth.

Image: Composite image of a coronal mass ejection taken by the SOHO spacecraft, 2002 © SOHO, NASA and ESA

21 December 2010 - UK viewers will be able to catch the start of a total lunar eclipse this morning, the first for three years, with totality starting at 07.41 GMT and lasting a little over an hour. Within the UK, Scotland and Northern Ireland will get the best views.

Lunar eclipses occur when the Moon passes through the Earth's shadow. During eclipse, the Moon may turn blood red or pink, with indirect sunlight giving the Moon a ghostly hue. Find out more in our eclipses fact file.

The last time a total lunar eclipse occurred on the winter solstice was in 1638, and the next time will be in 2094.

The Royal Observatory, Greenwich is famously the home of the Prime Meridian of the World (0° Longitude) where each day and year officially begins, and of Greenwich Mean Time (GMT), as well as of the celebrated Harrison timekeepers.

Now the Royal Observatory is also home to OMEGA's London 2012 Countdown Clock. Installed on the Prime Meridian Line by OMEGA, the Official Timekeeper of the Games, the clock will tick away the seconds, minutes, hours and days until the start of the London 2012 Olympic Games - some of which will be hosted in Greenwich Park.

The clock was unveiled yesterday (27 July 2011) in time to celebrate 'One Year to Go' to the start of the Games.

Solar flare seen by ESA/NASA SOHO satellite
on 23 January, shortly after a large solar flare
occurred at 03:59 GMT. Credits: ESA/NASA

25 January 2012 - A stronger-than-average solar flare at 03:59 GMT on Monday set off a coronal mass ejection travelling at 1400 km/s and reaching Earth yesterday afternoon. Its effects are likely to continue throughout today (Wednesday 25 Jan).

Solar flares are enormous explosions caused by the sudden release of energy from the magnetic fields of sunspots - temporary areas of intense magnetic activity in the Sun's atmosphere (corona). Solar flares in turn can result in coronal mass ejections (CMEs) - huge clouds of high-energy particles blasted into space by a solar flare. These clouds of material can strike the Earth causing geomagnetic storms and triggering a range of phenomena. Some of these are beautiful like the aurora, but others can be disastrous - disrupting satellites and communications systems.

Monday's solar flare triggered the strongest stream of protons seen since 2005. However, scientists predict that the current CME will only cause a minor geomagnetic storm without any visible effects on the ground nor any serious effects on satellites, phone networks or power grids.

Get involved - You can help spot and track solar storms at Solar Stormwatch, a joint web project of the Royal Observatory Greenwich, Zooniverse and Rutherford Appleton Laboratory. If you get involved your work will help give astronauts an early warning if dangerous solar radiation is headed their way - and you could make a new scientific discovery.

27 January - A small asteroid will pass within about 60,000km (roughly 37,000miles) of the Earth this afternoon, reaching its closest at about 16.00 GMT. This is one of the closest asteroid approaches ever recorded, but it poses no threat to Earth or to our geostationary satellites (which orbit at a distance of around 20,000km).

The asteroid has been named 2012 BX34 and is estimated to be about 11m (36ft) in diameter. Though it won't be visible to the naked eye, keen amateur astronomers still have a good chance of sighting it.

Fortunately it's very rare for large asteroids to strike the Earth - perhaps 60 objects greater than 5 km across have done so in the last 600 million years (or an average of about one every 10 million years). One of the most famous was of course the 10km-wide asteroid that may have led to the extinction of the dinosaurs 65 million years ago.

Smaller objects hit our planet more frequently - about 500 football-sized rocks strike the Earth each year.

Find out more about asteroids:

• Astronomy FAQs - will an asteroid hit the Earth?
  
• Fact file - The Minor Planets
  
• Fact file - Near-Earth Asteroids
  
• Impact: Collisions and Catastrophes (past exhibition)