Carnival of Space no. 43
The latest Carnival of Space (no.43!) is up and running (with a special Oscars® theme) over at Starts With A Bang. I promised not to cry…sniffle…
A step back in the right direction…
This is great news. Though as Johnathon Amos reports in his BBC online article we are going to have to wait a while to see what this means now for the STFC budget.
Odyssey’s end in sight for Ulysses
After just over seventeen years in space the Ulysses space probe looks as if its mission is drawing to a close. According to the European Space Agency Ulysses is beginning to show the signs of age, after nearly two decades touring the Solar System in orbit around its main interest – the Sun. The spacecraft is in a somewhat peculiar six year orbit around the Sun which takes it at one extreme flying right out to Jupiter and at the other extreme whirling over the Sun’s polar regions.
Ulysses has scrutinized the Sun in great detail over its seventeen or so years, telling us about the solar wind (the stream of charged particles emanating from the Sun), the Sun’s powerful magnetic field as well as how the Sun’s chromosphere and corona interact. One of Ulysses’ most interesting finds was that the solar wind at the poles of the Sun is emerging much faster than at the equator (with speeds of 750km/s and 350km/s respectively); and that the polar winds dominate about 2/3 of the heliosphere (the vast ‘shield’ around the Sun created by the solar wind). The probe, which was launched from the Space Shuttle’s cargo bay in 1990 has also studied Jupiter’s magnetic fields and the plasma environment around the giant planet.
So why is Ulysses dying after all these years? Well the probe itself is powered by the radioactive decay of a special isotope of plutonium. This decay slowly releases heat which the probe’s on-board technology converts into electricity. This in turn powers heaters, the science instruments and the communication antennae that are needed to send data back to Earth. However over time the radioactive isotope decay levels drop meaning that so to do the amounts of electricity produced.
This poses a problem for the craft because as it ventures out into space it needs its on-board heaters to keep the spacecraft at the right temperature. If they don’t and the craft’s temperature drops below 2°C then the probe’s fuel hydrazine (where have you heard that before) will freeze solid. It reminds me a bit of the lizards on David Attenborough’s incredible new BBC series ‘Life in Cold Blood’. They either need the Sun to warm them or find some heat of their own, otherwise they will freeze and die.
The scientists working with the Ulysses probe realised that if they didn’t do something the power levels would drop so much that the heaters and the science instruments would stop working – freezing the all important fuel. So in January they turned off the main transmitter that was sending data back to Earth in the hope that the re-routed power would go to the heaters and the science packages; keeping the hydrazine liquid. Unfortunately when they wanted to turn the transmitter back on to see if it had worked nothing happened. Now it seems Ulysses’ fuel will freeze as the probe cools in the vacuum of space to that crucial 2°C, bringing with it the end of an illustrious mission. Thankfully though there are many missions which are taking up Ulysses’ baton like SOHO, Stereo, Trace and Hinode. So solar science will be continuing into solar cycle 24, long after little Ulysses ends.
Above: An artist’s impression of the Ulysses probe
Credit: ESA
Carnival of Space no. 42
Chris is hosting the 42nd Carnival of Space over on his blog where you can read about moons, missiles and the ‘meatball’.
Hubble finds a COSMOS of gravitational lenses
Hubble Space Telescope scientists have recently announced that they have discovered 67 gravitational lenses lurking in images taken for a survey of galaxies. Hubble has spotted the gravitational lenses as part of the COSMOS survey into large scale structure of the Universe. The scientists have found some really cool lenses like the ‘Einstein Ring’ on the left. The results show that if the number of lenses seen by Hubble in this survey is typical of large sections of the sky then there could be hundreds of thousands of this type of gravitational lens across the whole night-sky!
This is one of the press releases that I worked on whilst in Germany last year. If you want to read the full story check it out on the ESA Hubble website here. As an aside it’s great to see Atlantis landed safely. Columbus is now installed on the International Space Station which is now looking incredible. The Columbus module is the one jutting out to the right hand side of the line of vertical modules in that image.
Above: This incredible ‘Einstein Ring’ captured by the Hubble Space Telescope is the product of a rare line-of-sight alignment of massive lensing galaxy, background galaxy and Hubble itself.
Credit: NASA, ESA, C. Faure (Zentrum für Astronomie, University of Heidelberg) and J.P. Kneib (Laboratoire d’Astrophysique de Marseille)
Save the skies…
…save the world. That’s the title of my new article in March’s issue of BBC Sky At Night magazine. In the article I discuss how the aims of astronomers and environmentalists have converged. I argue that if we can reduce our wastage of light, create more efficient lighting fixtures and get councils and local authorities to dim or at least reduce their lighting usage then we can not only save the night skies but reduce our carbon emissions. Hopefully in doing so we can be a little less harsh on our environment. If you are concerned that these sorts of measures may result in a wave of criminals and ne’er-do wells sweeping the streets then it’s worth reading the material on this page on the Campaign for Dark Skies’ website.
A night in the shadow of the Earth
Planetary positions
Lunar eclipses can only happen when the Sun, Moon and Earth are exactly aligned. The Earth must be between the Sun and the Moon so that the Moon is full i.e. opposite the Sun in the sky. The Moon’s orbit is slightly angled with respect to the plane of the Earth’s orbit. For this reason the Moon also has to be in a special position (where it is aligned with the plane of the Earth’s orbit) otherwise we would get lunar eclipses at every Full Moon!
Wrap up warm
The golden rule of observational astronomy is make yourself comfortable. Lunar eclipses last hours and it can get pretty chilly under clear crisp dark skies. Make sure you wear lots of layers and have a warm drink and some food to hand. The worst thing, I find, is having to cut short a great observing session because you can’t feel your fingers!
Know your umbra from your penumbra
The Earth’s shadow is made of two parts. The outer lighter part is called the penumbra. As the Moon moves into the penumbra you begin to see the edge of the Moon dim and eventually get ‘eaten away’- this is called the partial phase. The centre of the Earth’s shadow is called the umbra and it is much darker. When the Moon starts to enter the umbra it rapidly begins to disappear until it is completely immersed, usually going a deep red colour – this is the ‘total’ phase.
Why does it go red?
The Moon goes red for the same reason the sky is blue. The Earth’s atmosphere scatters blue light. So as sunlight passes through our atmosphere most of the blue wavelengths are scattered away leaving predominantly red light to get through. This goes out into space and lights the Moon in a deep red glow.
But hang on if the Moon is in shadow why is it bathed in red light?
The simple answer is that the Earth’s atmosphere refracts (or bends) light around it so that even though the Moon is in the Earth’s shadow the bent red light is directed towards the darkened Moon.
Look out for the blue fringe
I only found out about this during the lunar eclipse on 3rd March last year. As light passes through Earth’s lower atmosphere it is reddened but as light passes through Earth’s upper atmosphere the ozone gas there absorbs light at red wavelengths. This can sometimes result in a noticeable blue fringe around the edge of the eclipsed Moon. I saw it during last years eclipse and you can see a slight hint of it in my image above.
How dark is the Moon?
How dark the Moon is during the total phase of the eclipse generally depends on how much dust and pollution there is in Earth’s atmosphere. You can estimate the darkness of the Moon using the Danjon scale. On the five-point Danjon scale 0 is a total phase where you can hardly see the Moon at all whilst 4 is a total phase where the Moon goes a bright coppery red.
Set your alarms!
February’s eclipse comes at a fairly unsociable time. Mid-eclipse when the Moon is in the darkest part of the Earth’s shadow is at about 3:30 in the morning. If you want to watch the whole eclipse you will have to start watching at about 00:40 on the 21st when the Moon begins to enter the Earth’s shadow. The Moon enters the umbra at about quarter to two and leaves it at about ten past five. Finally the Moon returns to normal as it completely leaves the Earth’s shadow at about quarter past six!
Grab a friend
Eclipses are definitely a social event so why not grab a few friends to share in the experience; even if it is just sitting in darkness waiting for completely cloudy UK skies to clear! ;-)
Equipment
The great thing about lunar eclipses is that you don’t need any special equipment to observe them. If you want to, it’s useful to use a pair of binoculars to get a closer look but these are by no means a prerequisite.
Good luck and clear skies!
Above: The total lunar eclipse of 3rd March 2007; copyright Will Gater.
Carnival of Space no. 41
The new Carnival of Space is in town over on the New Frontiers blog.
A glimmer of hope for UK astronomy?
UK research astronomy, space science and physics is currently going through a pretty rough time. This is due to an anticipated £80m worth of cuts in the budget of the Science & Technologies Facilities Council (STFC) who fund much of the UK’s astronomy and physics research facilities both here and abroad. One repercussion (one of many) of the cuts was that the UK was forced to cancel its subscription to the Gemini Observatory (one of the finest research observatories in the Northern Hemisphere). Subsequently UK professional astronomers and postdoctoral researchers lost access to their use of the telescopes meaning many will not be able to carry out their vitally important astronomical research.
However there may be a chance to resolve the Gemini issue. Stuart is reporting that the Gemini Board and the UK STFC have announced that they are going to sit down and discuss the future of the UK’s involvement in Gemini whilst at the same time reinstating the observing time (for the first part of 2008 at the moment at least) that the UK astronomers had lost. I’m not a research astronomer but Chris is. He has a post on what this means to those who have spent time and effort in formulating the observing proposals that were initially cut. Finally – If you want great inside view and commentary on the academic side of astronomy then I recommend you have a browse of Prof. Andy Lawrence’s blog (the e-astronomer); he also has some really interesting posts on the funding cuts issue.
Galaxy eating monster reveals its secrets
A monster so huge it is capable of slowly devouring whole galaxies at a time. Sounds incredible doesn’t it? But that is what astronomers working on the Hubble Space Telescope think that the giant elliptical galaxy NGC 1132 is – a cosmic cannibal if you will. In this stunning new image from the NASA/ESA Hubble mission astronomers are seeing the vast hulk of a galaxy, 320 million light years distant, whose past is much darker than it might at first seem. That’s because whilst the stunning elliptical in Hubble’s new image looks serene and peaceful, it is in fact the aftermath of gravitational dance which saw the death of many smaller galaxies; and it all clinches on how astronomers think galaxies form.
One of the most popular current theories is that giant galaxies like NGC 1132 are made from the merger and assimilation of lots of smaller galaxies. Over time these vast elliptical giants like NGC 1132 emerge as enormous conglomerations of stars. Sounds all very vicious but in fact this galactic cannibalism is probably quite commonplace in the Universe if our theories of galaxy evolution are correct. Indeed Hubble scientists believe that our own Milky Way may have been partial to devouring the odd dwarf galaxy which strayed too close to it.
Yet the one question that we are bound to ask is how do we know? Well the answer comes from two main lines of evidence. The first is globular clusters. Galaxies like the Milky Way are home to globular clusters which reside above and below the disc of the galaxy. These are extremely ancient (and fairly compact) balls of stars and are useful tools for studying the evolution of stars. If you know where to look you can spot them through a small telescope on a clear night.
When Hubble scientists looked at NGC 1132 they noticed something interesting. A vast collection of globular clusters around the massive galaxy. They believe that what they are seeing are the globular clusters of NGC 1132′s victims – whole globular clusters that have been cast away as NGC 1132 merges with their parent galaxies. Since the stars in globulars are packed much more densely than the normal stars in the unfortunate galaxies their collective gravity holds the globular together. This means they can survive the huge gravitational disruptions involved in the merger and breakup of their parent galaxy.
The second piece of evidence comes from material we can’t see in this image – dark matter. Observations have shown that NGC 1132 is surrounded by a truly enormous cloud of dark matter. The dark matter cloud is thought to hold quantities of dark matter that are normally found residing in whole galaxy clusters of between ten and a few hundred galaxies – not one galaxy as seen with NGC 1132! NASA’s Chandra X-ray observatory was able to show that the galaxy is also surrounded by a glow from X-rays emitted from hot gas – about 120,000 light years in diameter – roughly the size of a galaxy cluster, giving yet more support to the idea that NGC 1132 is the result of the merging of one entire galaxy cluster.
If you want to find about more about this fascinating new result visit the Hubble website and whilst you’re there check out the latest Hubblecast.
Above: NGC 1132 from the HST
Image credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgment: M. West (ESO, Chile)
Astrofest 2008 & Sky At Night online
I’ve just got back from Astrofest 2008 in London. It was nice to meet up with old friends and colleagues and see the huge array of new telescopes and astronomy equipment, books etc. that are on offer this year. It was also great to see David Levy there too, one of the eminent comet discoverers of our time and a great writer as well.
If you haven’t already seen it then why not watch the most recent episode of The Sky At Night on BBC iPlayer? (it’s available there for 3 more days). It includes an interview about Mercury and NASA’s Messenger mission with Dr. Dave Rothery who you will have seen writing about Mercury in our February issue.
Book news (part I)
I achieved a milestone today in that I have finally got all the necessary image permissions for my book. The images are really cool and I can’t wait to submit my manuscript later in the year. Now I just have to finish the text…so it’s back to the word processor for me! In the mean time check out this incredible new image from Hubble and if you want to find out more about what’s going on in the image download the Hubblecast!
Successful lift-off for Space Shuttle Atlantis
The Space Shuttle Atlantis has finally lifted off from Cape Canaveral to begin its 11-day mission to the International Space Station (ISS). The launch of STS-122 has been delayed since December with fuel sensor malfunctions causing trouble for NASA. In the last few days weather worries looked as if they too might delay the launch yet again, so it is fantastic to see the shuttle riding a column of fire and smoke again! One of the main roles of STS-122 is to deliver Europe’s Columbus module to the ISS – a laboratory for doing research science on the space station built by the European Space Agency.
I had hoped to be at the Columbus mission control in Oberpfaffenhofen near Munich when I was in Germany for the original launch date in December. I was really disappointed at the delay of the launch then but now it’s great to see, some months later, Columbus finally take off into space. It’s Europe’s biggest contribution to the ISS and should see the research capabilities of the station blossom. The module will be attached to the station during the course of the mission (hopefully during the first of the three planned spacewalks). It will be interesting to see the science coming back from the ISS. If you want an idea of what research science might be possible in space Chris has an interesting post on his blog.
Image credit: NASA TV
Carnival of Space no. 40
The carnival is over on Orbiting Frog, why not take a look…
How did Mercury get so dense?
I’ve done several radio interviews in the past few weeks on the NASA Messenger mission to Mercury. One question that keeps popping up is – ‘How did Mercury get so dense?”. It’s a great question and one that is sometimes difficult to answer, fully, in a few seconds on air so I thought I would take some time to explore it in a post on the site.
Mercury is a tiny planet, some 4879km across, not much bigger than our own Moon. Its density of 5.3 grams for every cubic centimetre makes it the densest of all the terrestrial planets (those are Venus, Earth, Mercury and Mars) but also one of the most intriguing. The Mariner 10 probe which studied Mercury during the mid seventies mapped not quite half of the planet but it did give us an insight into a peculiar little world with some fascinating geology. Fascination that runs much deeper than the cratered, volcanic and battered surface that we see in the latest Messenger images. Measurements of Mercury’s density infer that much of the planet must be made of a iron-rich core that accounts for 60% of the planet’s mass and an incredible 75% of its radius! But why is it so dense? At the moment scientists just aren’t sure, which is just one reason why Messenger and other missions are going to be scrutinizing Mercury over the next few years. But we do have some ideas.
One theory argues that the bright, extremely hot young Sun played a role in vaporising away rocky material on the surface of Mercury as it was in the process of forming. This would mean that Mercury would be predominantly made of metallic material that had (by then) formed a substantial core; any elements and chemicals that could be easily vaporised and blown away would be notably absent or depleted in the Mercurial geology.
Another suggestion, according to NASA scientists, says that when the Sun and all the planets were forming in the solar nebula (the great cloud of dust and gas around the young Sun), tremendous amounts of gas could have had an important role in deciding what materials Mercury formed out of. To understand this let’s look at a simplified view. Rocky particles (silicates) in the solar nebula, when the planets were forming, were much lighter than their metallic counterparts. As such the gas around our star was able to whisk the lighter particles away and into the Sun, effectively sieving out the lighter silicates in the material from which Mercury went onto form. What was left was a metal rich cloud from which Mercury formed.
Lastly then and perhaps the most exciting idea is that Mercury was smashed into by a large body after its formation. This scenario requires Mercury to have already formed in much the same was as the normal terrestrial planets. The layers in Mercury’s internal structure would be fairly well defined by this stage rather than a mix of all sorts of material. It would have a metallic core with a rocky (silicate) crust and mantle (similar to the Earth’s structure). The theory says that a large body (like a rogue proto-planet) might have collided with the young Mercury blasting away its crust (and much of its mantle) leaving the mostly metallic material at its centre. (Think of it as smashing a boiled egg so that the shell and the white fly away leaving a little yellow core.)
So the answer to the question of ‘How did Mercury get so dense?’ is…we just don’t know yet. Nevertheless Messenger and the handful of other European and Japanese missions to Mercury will be more than equipped with their instruments to try and find out by studying Mercury’s magnetic field, its surface geology and composition.
To find more about the Messenger mission go to the NASA website.
Above: Mercury in colour imaged by Messenger
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
