In the News this month... insights into the first starbursts
Exactly how galaxies form has been a topic of debate for some time – it is not clear whether stars began forming everywhere at once, or just in clumps around the disk, but research published in Nature during February has found evidence that star forming regions in young galaxies are small, but forming stars at astonishingly high rates.
A team of astronomers led by Fabian Walter at the Max Planck Institute for Astronomy studied a distant galaxy 12.8 billion light years away to investigate early stages of galactic evolution less than a billion years after the Big Bang. The galaxy, a quasar known as J1148+2551 located in Ursa Major, is one of the most distant known and provides a view of star formation in the early universe.
A radio image of the distant quasar J1148+5251 made using the VLA CREDIT: NRAO/AUI/NSF
The team used the IRAM interferometer, a radio telescope located on the Plateau de Bure in the French Alps, to search for the highly redshifted signal of ionised carbon, a reliable signal of ongoing star formation. What they found was that the star formation was concentrated in a region at the centre of the galaxy with a radius of about 750 parsecs and apparently forming around 1000 solar-mass stars per square kiloparsec each year.
This is similar to the rate of star formation seen in active galaxies much closer to the Milky Way, forming stars much more recently but over a much smaller area. One nearby example is the galaxy known as Arp220 which is forming stars at a similar rate but in an area only 100 parsecs in radius, and in our own Milky Way the rate of star formation is an estimated mere one solar mass per year. Some regions within our Galaxy are as active as the centre of J1148+5251, but on a much smaller scale, such as the core of the Orion nebula. Stars form when clouds of gas collapse under gravity. As the cloud collapses, the temperature and pressure increase until a limit is reached where the collapse is halted and stars stop forming. This limit has been reached in the core of the Orion nebula and in the centre of J1148+5251 and according to Walter, J1148 is like a hundred million Orion nebula-type regions combined. This result is important in studies of galaxy formation, suggesting that galaxies form from the centre. In the early stages of a galaxy the core forms stars at a spectacular rate and grows in size over time as young galaxies collide and merge.
Observations such as these are tricky. The signature of ionised carbon is radiation in the infra-red part of the spectrum, but the huge distance to these very early galaxies causes a cosmological redshift which stretches the wavelength of the radiation as it travels to us here on Earth, shifting it to the radio part of the spectrum where it is harder to resolve fine details. At a distance of almost 13 billion light years, the core of J1148 is about the size of a one Euro coin at a distance of 18 kilometres. Observations of this sort are a key aim of ALMA, the Atacama Large Millimetre Array, currently under construction high in the Chilean Andes.
Launched on the 11th of June 2008, the Fermi gamma ray space telescope searches for these events using sensitive instruments, as well as surveying the sky to investigate the high energy emission from other interesting objects such as active galaxies, pulsars and solar flares, as well as unidentified sources of high energy gamma rays. Since it's launch, Fermi has triggered follow-up observations of 58 GRBs detected with the Large Area Telescope, another science instrument on board the satellite.
Located in the southern constellation of Carina, the burst of September 16th, given the designation GRB 080916C, was quickly observed with other telescopes on the ground - a team using the the 2.2-metre telescope at La Silla in Chile calculated that the object was at a redshift of 4.35, a distance of 12.2 billion light years. Analysis of the results, published in Science Express on 19th February, show that this burst is the most energetic observed to date, releasing more than twice the estimated energy as the previous record holder. Knowing both the distance and the brightness of a burst means that the energy of the explosion can be estimated. Although GRB's emit their energy in very narrow jets, estimates of their energies are usually based on how much energy would have been involved if energy was emitted equally in all directions, a quantity known as isotropic energy. In this case, the isotropic energy of the burst was almost 9000 times the power of a single regular supernova explosion, and the gas emitting the initial gamma ray flash must have been travelling at almost the speed of light.
Credit: NASA/DOE/Fermi LAT Collaboration
As well as being record breaking, this burst displayed another unusual characteristic – a five second time delay between the arrival of the highest and lowest energy photons. Such a delay has been seen only in one previous burst and the explanation is not yet certain. One idea is that the delay is caused by the nature of the material surrounding the explosion, the low and high energy gamma rays could be coming from different parts of the jet or created through different mechanisms, according to Peter Michelson, the principle investigator for Fermi's Large Area Telescope. Another suggestion comes from the speculative idea of quantum gravity – if correct, then at its smallest scales space is not smooth but turbulent, and this turbulence would have stronger effects on higher energy photons, slowing them down slightly compared to other photons. This effect would be very small and only visible over huge distances – such as that to a distant GRB.
Further observations of other GRBs at different distances should be able to distinguish between the two ideas. If the environment around the GRB is causing the time delay then the signal should be similar for GRBs at any distance. However, if quantum gravity is correct then the time delay should be more pronounced for more distant GRBs. Fermi is designed to operate for at least five years, and should collect a large sample of GRB events over that time.
So, through my involvement with Scouts I've been able to advertise the International Year of Astronomy to kids all around WA. The (now ex-) Chief Commissioner, Sue Mitchell, gave me a grant to purchase 2000 IYA-branded planispheres which I've been sending out to Scout Troops around the state, and last week the new Chief, Peter Walton, asked if I'd write something for the monthly Branch newsletter for February. Here is what I wrote.
"2009 is the International Year of Astronomy, celebrating 400 years since the invention of the telescope and Galileo's first observations of the heavens. Astronomy is one of the oldest sciences going back thousands of years in human history, but Galileo's observations changed our view of the Universe forever. Astronomy has come a long way in the last 400 years with many exciting discoveries, many new technologies and even giant telescopes in space. During this year of celebration there are many exciting astronomy-themed events happening all around the state, many of them are suitable for Scouts. Scouts also has planispheres available for Scout groups - these are handy card gadgets which show you the sky on any night of the year and are a great way to get started observing the stars.
Right now there is a comet visible in the skies after sunset. Comet Lulin is currently in the constellation Virgo and may be visible with the naked eye if you are lucky enough to live somewhere with no light pollution (it will look like a small fuzzy patch). It should be an easy object to find with binoculars however, even from the middle of Perth! Comet Lulin should be visible throughout March, although it will fade as the month goes on and it moves further from the Sun. There are planets to see as well (you can tell a planet from a star because planets don't twinkle). Venus will be easy to spot low in the West after sunset during the fist half of March, and Saturn will be visible in the East in the evenings, by the end of March it will be visible all night. With binoculars you may be able to spot Saturn's rings and one or two of it's moons. Full Moon occurs on March 11th and is always a spectacular object with binoculars. The best time to look is a couple of days either side of Full Moon when the edge of the shadow picks out many spectacular craters and mountains."
That should go out in the newsletter at the start of March.
There was another development this week. The WA Scouts Adventurous Activities team owns a portable climbing wall and it's time for a re-paint, and Sue had the great idea of using an astronomy theme! So they're going to paint it a dark blue, stick on some stars in the shape of a few constellations (with a few suggestions from me) and put a big copy of the IYA logo at the top! It should look awesome.
There are several events shaping up for the 100 Hours of Astronomy weekend as well, but that's another story.
Ben Goldacre - comment on sensationalism in the media
Ben Goldacre is the author of Bad Science, one of the books that's been on my "Books I really want to read" list for ages. I used to enjoy his column in the Guardian and still enjoy his blog, well worth a read. Here's an interview he did recently with Conrad on the problem of sensationalised science reporting in mainstream media. It's well worth a look.
The elephant in the room: overpopulation in the environment debate
Since I was a kid I've been a bit of an environmentalist. I remember asking the headteacher at my primary school if we could have an environmental officer who, like the road safety officer, would be a child at the school who would stand up in assembly every now and then and tell everyone something important or useful. It turned out that the road safety officer was a Council funded initiative, so a few of us started our own environment club instead - the Environmentally Green Group (EGG). We had regular meetings, a small garden, even membership cards. It's something that's stayed with me as I've grown up.
Last week, John Feeney wrote a piece for the BBC's Green Room about a topic that I first encountered at the start of my GCSE history course: population statistics and the problem of overpopulation. It's a topic that is often totally avoided in debates about the environment, and it does have something of an uncomfortable history. Malthus wrote a famous piece on population, first published in 1798 which influenced British politics and the poor reforms, and Darwin's ideas on evolution and survival of the fittest. (Incidentally, I'm reading On the Origin of Species at the moment, I'd highly recommend it.)
In any environmental system, the available resources can only support a certain size of population. The problem the human race has is the same: our planet (which is a closed system) can only support a finite number of people, Thanks to the agricultural revolution and the continued development of techniques, chemicals and technology ever since, a given patch of ground has become capable of supporting more and more people, which is good since the population has been increasing at quite a rate thanks to the industrial revolution, developments in medicine and general healthcare, and so on. But, at some point, the population will pass the point at which there isn't enough available land to support it. Has this already happened? According to Feeney, there is a growing number of experts who say that yes, we have.
So what can we do about it? Let's get this clear: this does not have to mean population control. We can learn a lot from the negative historical examples. Education can go a long way. As Feeney points out in his article, which is the greater threat? That humane ways to attempt to slow population growth might be abused, or that we carry on as we are and end up with an ecological catastrophe which causes devastation and results in the deaths of millions? We are heading for a crash, and it will be devastrating. We need to do something about it, and simply reducing our current overconsumption in the West just won't avert a disaster. If we don't do it ourselves, nature will do it for us.
There's an ongoing effort to get the problem into the media spotlight during February via the Global Population Speak Out. The idea is to get as many people as possible to talk publicly about the issue. Many of those involved are experts in environmental issues or social policy, politicians or other public figures, activists and science writers. It's not much, but this is my effort. Think about it.
A telescope on the Moon? CREDIT: NASA / USGS / LPI / ASU / Google / Megan
The idea of building a telescope on the Moon has been around for a while. There are many early references to papers and conference contributions on the topic by (amongst others) Stanisław Gorgolewski, a man who is, I suspect, well-known to anyone who has visited the radio telescope at Toruń. One of his more recent conference abstracts discusses the idea from a modern perspective including using lunar telescopes for SETI searches.
It's a topic that does seem to keep coming back. A paper on this subject caught my eye while I was browsing the daily update of papers on astro-ph arXiv on Wednesday. Written by Sebastian Jester (MPIA Heidelberg) and Heino Falcke (ASTRON / Radboud Universiteit Nijmegen), the paper describes (in some detail) how radio telescopes on the Moon could be useful for a whole range of experiments, from searching for extra-terrestrial intelligence to trying to detect the signiture of the epoch of reionisation in the early universe.
Why the Moon? Well, two obvious advantages are that a) there are no people there, and b) there is no atmosphere. No people means no mobile phones, pagers, or other radio noisy devices to interfere with sensitive observations. This is why most new radio telescopes such as the MWA are being built in remote places like the Murchison here in Western Australia. What about the atmosphere? Well, one advantage of radio astronomy is that usually you don't have to worry too much about the atmosphere. This doesn't apply at very low frequencies, however, where the ionosphere starts to cause real problems below about 50 MHz, so it seems logical to build a very low frequency telescope somewhere with no atmosphere.
One reason for renewed interest in lunar telescopes seems to be the interest in finding the signature of the epoch of reionization by observing redshifted neutral hydrogen. This is an important spectral line in radio astronomy, occuring at a frequency of 1.4GHz (a wavelength of 21cm) in the local universe. The further out into space you look, the further back in time you are looking, and the faster stuff is moving away from you. Due to the Doppler effect, the faster it's moving away, the more red-shifted the emission becomes and that 1.4GHz spectral line gets shifted to lower and lower frequencies. The reionization signature comes from a time in the history of the universe when the neutral gas that filled most of the universe was first ionized by the high energy uv radiation from the first stars at a redshift high enough that the 1.4GHz emission from hydrogen gets shifted down to somewhere below a few hundred MHz.
These kinds of experiments use dipole arrays like the MWA to observe the sky. This has advantages for working on the Moon. Unlike with optical telescopes, there are no sensitive, easily scratched optics to worry about - that lunar dust would cause all sorts of problems for an optical mirror. These arrays also have no moving parts, the beams are steered electronically, so there are no mechanical problems to worry about meaning easy deployment and minimal maintenance. We know how to build electronics that can survive in the extreme environments both in space and on the Moon, as well as survive the stress of launch, because we've been doing it for fifty years.
So, while an Arecibo on the Moon is somewhat fanciful, it is not inconceivable that we could have a radio telescope up there at some point.
Experiments with my new toy - a Fuji Finepix S1000. I got home this evening to see the Moon rising over the building opposite, so I thought I'd get out the tripod, have a play with the settings in manual mode and see just what it is capable of.
Evening sky with the new camera. Left: no zoom. Centre: maximum optical zoom. Right: maximum digital zoom. These pictures have been shrunk quite a bit so that they don't make the page take ages to load on slow connections. CREDIT: Megan
OK, so the focus isn't quite right, that's my fault, not the camera's. The second two pictures were taken a bit later than the first one to see how good the contrast is. I have to say, I'm impressed. I've been using my Grandad's old film SLR for years and I love it. This isn't a replacement for the SLR, but it's heaps better than my knackered old compact camera that I've been using since the summer of 2003! One day I'll give in and get a digital SLR, but not just yet.
There's a comet around at the moment which is at about magnitude 6, visible to the naked eye under dark skies, but an easy target with binoculars. Comet Lulin is in the constellation of Libra and is still getting brighter, so it may be worth watching. Of course, comet predictions are notoriously unpredictable, but it is still worth having a look out for it as it isn't going to be back in our neighbourbood for quite a while - it has an orbital period of more than 28,000,000 years! It is thought that the comet will be at it's brightest around the end of February when it will be close to the planet Saturn. At the moment it's not at a good altitude here in Perth until about 1am, so I'll be having a look at the weekend.
Incidentally, when I took out the rubbish the other night, I noticed that Orion was high and bright in the sky overhead. He's upside down of course, standing on his head compared to what I'm used to. I'm also used to thinking of it as a winter constellation, but it's the middle of summer and he's dominating the sky. Seems very odd!
There's now an Astronomy 2009 toolbar available for both Firefox and Internet Explorer. It's pretty cool, but something of a distraction when you're trying to get on with some proper work! Check it out.
This evening I went to a meeting about the Australia Day events that I helped out with last week. The whole day was a fantastic success and the feedback from the visitors was superb, everyone had a fantastic time by the sounds of it. From 2pm when we opened until the fireworks at 9pm, an estimated 5000 people visited the Family Zone including more than 1000 children who got to play on bouncy castles, trampolines, crazy bikes, and lots of other fun stuff. The eclipse viewing was a big success with over 700 people seeing the partial eclipse safely. Awesome. I'll be going back to help next year, even though there will be no eclipse!
Ever wanted to build your own telescope but don't know where to start? Well fear not! You too can build your own telescope in an afternoon! Not just any telescope either: a mm-wave dish, complete with a transporter to get it up the mountain. Interested? Here are the plans for building your own ALMA antenna. Thanks to Rob at Jodrell for the link.
Don't fancy that? How about a model of a NASA Deep Space Network antenna? Or Hubble? The James-Webb telescope? Spitzer? The Nobeyama Radio Observatory also have a stack of models to build, including VERA, Subaru, VSOP and Solar-B (the text is in Japanese, but if you're an experienced modeller you can figure it out pretty easily).
I spent a lot of time building cardboard models of stuff when I was younger. There was one of those weekly magazines that built up into a science encyclopedia and each issue came with a model. I built a space shuttle, a windmill, a submarine (complete with torpedo tubes, and torpedoes!), a Formula One car, a motorbike, a catamaran (which I varnished so it floated in the bath), a glider, a sundial and plenty of others.
I've created a few of my own models too, over the years. A couple of years ago I turned a Xerox box into a Tardis, and (by request) turned another one into a wheel clamp for a prank, I ended up with a reputation for being able to "make anything out of a Xerox box". I even started working on a cardboard model of the Lovell telescope (not involving boxes!) , but I never had time to finish it...
The rebuilt fully functional MkV model - Alastair, Mark and I spent three months re-building this in our spare timeCREDIT: Mike Peel
If you're feeling really ambitious, you can always try something more complex. Together with Alastair Gunn (Jodrell's VLBI guru) and Mark Roberts (one of the telescope controllers), I spent three months rebuilding a model of the MkV telescope - the telescope that never was. It was designed by Bernard Lovell and Charles Husband and would have been 400 feet across if it had been built. The propsed site was at Meifod in Wales, in a natural valley which would have sheilded the telescope from a lot of the wind - a major problem with large telescopes.
The model had been constructed years ago to demonstrate the concept to funders, but had fallen into disrepair when the project was cancelled. It had been rebuilt before, but then left to rot in a warehouse on the Wirral for many years. When we got hold of it it was in a pretty sorry state and many weekends were spent with a soldering iron trying to fix the main structure. The electricians even got the ancient drive system going, so we could even drive it. There were suggestions about putting a 30 GHz receiver on it and slaving it to the Lovell, but somehow I don't think the surface accuracy would have been good enough!