Archive for Hubble Space Telescope

Cosmology Webcasts Coming Up…

Posted in The Universe and Stuff with tags , , , , on September 29, 2012 by telescoper

Courtesy of freelance science writer Bruce Lieberman, whom I met briefly at the recent “Origin of the Expansion of the Universe” meeting in Flagstaff, AZ,  here’s a plug for two live webcasts on topical topics that are coming up in the next couple of weeks. On behalf of the Kavli Foundation, Bruce will be interviewing astronomers about the new Hubble XDF image (Oct. 4) and the new Dark Energy Survey camera, which just saw First Light (Oct. 11).

Live Q&A and Webcast: What Does Hubble’s Deepest Image of the Universe Reveal?

Click on the above heading for  direct link to webcast.

October 4, 11-11:30 am PDT (18-18:30 GMT; 19-19:30 BST)

Using data from the Hubble Space Telescope, a multi-national team of astronomers recently released our deepest-ever image of the
universe. Pascal Oesch, a Hubble Fellow at the University of California at Santa Cruz, and Michele Trenti, a researcher at the Kavli Institute for Cosmology, Cambridge at the University of Cambridge in the U.K., answer your questions about how the image was created and what it reveals about the early universe.

Viewers may submit questions to the two Hubble researchers via Twitter using #KavliAstro or email to info@kavlifoundation.org.

Live Q&A and Webcast: Can a New Camera Unravel the Nature of Dark Energy?

Click on the above heading for  direct link to webcast.

October 11, 9-9:30 am PDT (16-16:30 GMT; 17-17:30 BST)

Scientists have great expectations for the newly operational Dark Energy Camera, which may significantly advance our understanding of the mysterious force expanding the universe at an ever accelerating rate. Fermilab scientists Brenna Flaugher, project manager for the Dark Energy Camera, and Joshua Frieman, director of the Dark Energy Survey, answer your questions about the camera and what it’s expected to reveal.

Viewers may submit questions via Twitter using #KavliAstro or email to info@kavlifoundation.org.

Extremely Deep Space

Posted in The Universe and Stuff with tags , , , on September 27, 2012 by telescoper

There’s been a lot of media coverage of this image, taken using the Hubble Space Telescope using an exposure time of 2 million seconds (aproximately 23 days), including a nice feature article on the BBC Website to which I refer you for more explanation, so I’ll keep this post brief. Suffice to say that the Hubble eXtreme Deep Field (XDF) is the deepest image of the sky ever obtained and it reveals the faintest and most distant galaxies ever seen, showing some galaxies as they were over 13 billion years ago. It’s also very very pretty…

And if the overwhelming scale of the Universe revealed by this picture makes you feel worthless and insignificant, just remember that things could have been much worse. You might have been Nick Clegg.

Heart of Darkness

Posted in Astrohype, The Universe and Stuff with tags , , , , , on March 6, 2012 by telescoper

Now here’s a funny thing. I’ve been struggling to keep up with matters astronomical recently owing to pressure of other things, but I could resist a quick post today about an interesting object, a galaxy cluster called Abell 520. New observations of this complex system – which appears to involve a collision between two smaller clusters, hence its nickname “The Train Wreck Cluster” – have led to a flurry of interest all over the internet, because the dark matter in the cluster isn’t behaving entirely as expected. Here is the abstract of the paper (by Jee et al., now published in the Astrophysical Journal):

We present a Hubble Space Telescope/Wide Field Planetary Camera 2 weak-lensing study of A520, where a previous analysis of ground-based data suggested the presence of a dark mass concentration. We map the complex mass structure in much greater detail leveraging more than a factor of three increase in the number density of source galaxies available for lensing analysis. The “dark core” that is coincident with the X-ray gas peak, but not with any stellar luminosity peak is now detected with more than 10 sigma significance. The ~1.5 Mpc filamentary structure elongated in the NE-SW direction is also clearly visible. Taken at face value, the comparison among the centroids of dark matter, intracluster medium, and galaxy luminosity is at odds with what has been observed in other merging clusters with a similar geometric configuration. To date, the most remarkable counter-example might be the Bullet Cluster, which shows a distinct bow-shock feature as in A520, but no significant weak-lensing mass concentration around the X-ray gas. With the most up-to-date data, we consider several possible explanations that might lead to the detection of this peculiar feature in A520. However, we conclude that none of these scenarios can be singled out yet as the definite explanation for this puzzle.

Here’s a pretty picture in which the dark matter distribution (inferred from gravitational lensing measurements) is depicted by the bluey-green colours and which seems to be more concentrated in the middle of the picture than the galaxies, although the whole thing is clearly in a rather disturbed state:

Credit: NASA, ESA, CFHT, CXO, M.J. Jee (University of California, Davis), and A. Mahdavi (San Francisco State University)

The three main components of a galaxy cluster are: (i) its member galaxies; (ii) an extended distribution of hot X-ray emitting gas and (iii) a dark matter halo. In a nutshell, the main finding of this study is that the dark matter seems to be stuck in the middle of the cluster with the X-ray gas, while the  visible galaxies seem to be sloshing about all over the place.

No doubt there will be people jumping to the conclusion that this cluster proves that the theory of dark matter is all wrong, but I think that it simply demonstrates that this is a complicated object and we don’t really understand what’s going on. The paper gives a long list of possible explanations, but there’s no way of knowing at the moment which (if any) is correct.

The Universe is like that. Most of it is a complete mess.

JWST: Too Big to Fail?

Posted in Finance, Science Politics, The Universe and Stuff with tags , , , , , on July 7, 2011 by telescoper

News emerged last night that the US Government may be about to cancel the  James Webb Space Telescope, which is intended to be the successor to the Hubble Space Telescope. I’m slow out of the blocks on this one, as I had an early night last night, but there’s already extensive reaction to the JWST crisis around the blogosphere: see, for example, Andy Lawrence, Sarah Kendrew, and Amanda Bauer; I’m sure there are many more articles elsewhere.

The US House Appropriations Committee has released its Science Appropriations Bill for the Fiscal Year 2012, which will be voted on tomorrow. Among other announcements (of big cuts to NASA’s budget) listed in the accompanying press release we find

The bill also terminates funding for the James Webb Space Telescope, which is billions of dollars over budget and plagued by poor management.

It is undoubtedly the case that JWST is way over budget and very late. Initial estimates put the cost of the at $1.6 billion and that it would be launched this year (2011). Now it can’t launch until at least 2018,  and probably won’t fly until as late as 2020, with an estimated final price tag of $6.8 billion. I couldn’t possibly comment on whether that is due to poor management or just that it’s an incredibly challenging project.

There’s a very informative piece on the Nature News Blog that explains that this is an early stage of the passage of the bill and that there’s a long way to go before JWST is definitely axed, but it is a worrying time for all those involved in it. There are serious implications for the European Space Agency, which is also involved in JWST, to STFC, which supports UK activity in related projects, and indeed for many groups of astronomers around the world who are currently engaged in building and testing instruments.

One of the arguments against cancelling JWST now is that all the money that has been spent on it so far would have been wasted, in other words that it’s “too big to fail”, which is an argument that obviously can’t be sustained indefinitely. It may be now it’s so far over budget that it’s become a political liability to NASA, i.e. it’s too big to succeed. It’s too early to say that JWST is doomed – this draft budget is partly a political shot across the bows of the President by the Republicans in the House – but it does that the politicians are prepared to think what has previously been unthinkable.

UPDATE: A statement has been issued by the American Astronomical Association.

 

Space: The Final Frontier?

Posted in The Universe and Stuff with tags , , , , , , , on July 9, 2010 by telescoper

I found this on my laptop just now. Apparently I wrote it in 2003, but I can’t remember what it was for. Still, when you’ve got a hungry blog to feed, who cares about a little recycling?

It seems to be part of our nature for we humans to feel the urge  to understand our relationship to the Universe. In ancient times, attempts to cope with the vastness and complexity of the world were usually in terms of myth or legend, but even the most primitive civilizations knew the value of careful observation. Astronomy, the science of the heavens, began with attempts to understand the regular motions of the Sun, planets and stars across the sky. Astronomy also aided the first human explorations of own Earth, providing accurate clocks and navigation aids. But during this age the heavens remained remote and inaccessible, their nature far from understood, and the idea that they themselves could some day be explored was unthinkable. Difficult frontiers may have been crossed on Earth, but that of space seemed impassable.

The invention of the telescope ushered in a new era of cosmic discovery, during which we learned for the first time precisely how distant the heavenly bodies were and what they were made of.  Galileo saw that Jupiter had moons going around it, just like the Earth. Why, then, should the Earth be thought of as the centre of the Universe? The later discovery, made in the 19th Century using spectroscopy, that the Sun and planets were even made of the same type of material as commonly found on Earth made it entirely reasonable to speculate that there could be other worlds just like our own. Was there any theoretical reason why we might not be able to visit them?

No theoretical reason, perhaps, but certainly practical ones. For a start, there’s the small matter of getting “up there”. Powered flying machines came on the scene about one hundred years ago, but conventional aircraft simply can’t travel fast enough to escape the pull of Earth’s gravity. This problem was eventually solved by adapting technology developed during World War II to produce rockets of increasingly large size and thrusting power. Cold-war rivalry between the USA and the USSR led to the space race of the 1960s culminating in the Apollo missions to the Moon in the late 60s and early 70s. These missions were enormously expensive and have never been repeated, although both NASA and the European Space Agency are currently attempting to gather sufficient funds to (eventually) send manned missions to Mars.

But manned spaceflights have been responsible for only a small fraction of the scientific exploration of space. Robotic probes have been dispatched all over the Solar System. Some have failed, but at tiny fraction of the cost of manned missions. Landings have been made on the solid surfaces of Venus, Mars and Titan and probes have flown past the beautiful gas giants Jupiter, Saturn, Uranus and Neptune taking beautiful images of these bizarre frozen worlds.

Space is also a superb vantage point for astronomical observation. Above the Earth’s atmosphere there is no twinkling of star images, so even a relatively small telescope like the Hubble Space Telescope (HST) can resolve details that are blurred when seen from the ground. Telescopes in space can also view the entire sky, which is not possible from a point on the Earth’s surface. From space we can see different kinds of light that do not reach the ground: from gamma rays and X-rays produced by very energetic objects such as black holes, down to the microwave background which bathes the Universe in a faint afterglow of its creation in the Big Bang. Recently the Wilkinson Microwave Anisotropy Probe (WMAP) charted the properties of this cosmic radiation across the entire sky, yielding precise measurements of the size and age of the Universe. Planck and Herschel are pushing back the cosmic frontier as I write, and many more missions are planned for the future.

Over the last decade, the use of dedicated space observatories, such as HST and WMAP, in tandem with conventional terrestrial facilities, has led to a revolution in our understanding of how the Universe works. We are now convinced that the Universe began with a Big Bang, about 14 billion years ago. We know that our galaxy, the Milky Way, is just one of billions of similar objects that condensed out of the cosmic fireball as it expanded and cooled. We know that most galaxies have a black hole in their centre which gobbles up everything falling into it, even light. We know that the Universe contains a great deal of mysterious dark matter and that empty space is filled with a form of dark energy, known in the trade as the cosmological constant. We know that our own star the Sun is a few billion years old and that the planets formed from a disk of dusty debris that accompanied the infant star during its birth. We also know that planets are by no means rare: nearly two hundred exoplanets (that is, planets outside our Solar System) have so far been discovered. Most of these are giants, some even larger than Jupiter which is itself about 300 times more massive than Earth, but this may simply because big objects are easier to find than small ones.

But there is still a lot we still don’t know, especially about the details. The formation of stars and planets is a process so complicated that it makes weather forecasting look simple. We simply have no way of knowing what determines how many stars have solid planets, how many have gas giants, how many have both and how many have neither. In order to support life, a planet must be in an orbit which is neither too close to its parent star (where it would be too hot for life to exist) nor too far aware (where it would be too cold). We also know very little about how life evolves from simple molecules or how robust it is to the extreme environments that might be found elsewhere in our Universe. It is safe to say that we have no absolutely idea how common life is within our own Galaxy or the Universe at large.

Within the next century it seems likely that we will whether there is life elsewhere in our Solar System. We will probably also be able to figure out how many earth-like exoplanets there are “out there”. But the unimaginable distances between stars in our galaxy make it very unlikely that crude rocket technology will ever enable us to physically explore anything beyond our own backyard for the foreseeable future.

So will space forever remain the final frontier? Will we ever explore our Galaxy in person, rather than through remote observation? The answer to these questions is that we don’t know for sure, but the laws of nature may have legal loopholes (called “wormholes”) that just might allow us to travel faster than light if we ever figure out how to exploit them. If we can do it then we could travel across our Galaxy in hours rather than aeons. This will require a revolution in our understanding not just of space, but also of time. The scientific advances of the past few years would have been unimaginable only a century ago, so who is to say that it will never happen?

Ten Facts about Space Exploration

  1. The human exploration of space began on October 4th 1957 when the Soviet Union launched Sputnik the first man-made satellite. The first man in space was also a Russian, Yuri Gagarin, who completed one orbit of the Earth in the Vostok spacecraft in 1961. Apparently he was violently sick during the entire flight.
  2. The first man to set foot on the Moon was Neil Armstrong, on July 20th 1969. As he descended to the lunar surface, he said “That’s one small step for a man, one giant leap for mankind.”
  3. In all, six manned missions landed on the Moon (Apollo 11, 12, 14, 15, 16 and 17; Apollo 13 aborted its landing and returned to Earth after an explosion seriously damaged the spacecraft). Apollo 17 landed on December 14th 1972, since when no human has set foot on the lunar surface.
  4. The first reusable space vehicle was the Space Shuttle, four of which were originally built. Columbia was the first, launched in 1981, followed by Challenger in 1983, Discovery in 1984 and Atlantis in 1985.  Challenger was destroyed by an explosion shortly after takeoff in 1992, and was replaced by Endeavour. Columbia disintegrated over Texas while attempting to land in 2003.
  5. Viking 1 and Viking 2 missions landed on surface of Mars in 1976; they sent back detailed information about the Martian soil. Tests for the presence of life proved inconclusive, but there is strong evidence that Mars once had running water on its surface.
  6. The outer planets (Jupiter, Saturn, Uranus and Neptune) have been studied by numerous fly-by probes, starting with Pioneer 10 (1973) and Pioneer 11 (1974) . Voyager 1 and Voyager 2 flew past Jupiter in 1979;  Voyager 2 went on to visit Uranus (1986)  and Neptune (1989) after receiving a gravity assist from a close approach to Jupiter. These missions revealed, among other things, that all these planets have spectacular ring systems – not just Saturn. More recently, in 2004, the Cassini spacecraft launched the Huygens probe into the atmosphere of Titan. It survived the descent and sent back amazing images of the surface of Saturn’s largest moon.
  7. Sending a vehicle into deep space requires enough energy to escape the gravitational pull of the Earth. This means exceeding the escape velocity of our planet, which is about 11 kilometres per second (nearly 40,000 kilometres per hour). Even travelling at this speed, a spacecraft will take many months to reach Mars, and years to escape the Solar System.
  8. The nearest star to our Sun is Proxima Centauri, about 4.5 light years away. This means that, even travelling at the speed of light (300,000 kilometres per second) which is as fast as anything can do according to known physics, a spacecraft would take 4.5 years to get there. At the Earth’s escape velocity (11 kilometres per second), it would take over a hundred thousand years.
  9. Our Sun orbits within our own galaxy – the Milky Way – at a distance of about 30,000 light years from the centre at a speed of about 200 kilometres per second, taking about a billion years to go around. The Milky Way contains about a hundred billion stars.
  10. The observable Universe has a radius of about 14 billion light years, and it contains about as many galaxies as there are stars in the Milky Way. If every star in every galaxy has just one planet then there are approximately ten thousand million million million other places where life could exist.

New light through a gravitational lens

Posted in The Universe and Stuff with tags , , , , on July 1, 2010 by telescoper

New data from the European Space Agency’s Herschel Space Observatory have just been released that shed new light on a well-known gravitational lens system involving the cluster Abell 2218. You can get more details and higher-resolution pictures from the STFC press release or from the dedicated Herschel Outreach Website, but I couldn’t resist putting this nice picture up.

Image Credit: ESA/SPIRE and HERMES Consortia

This triptych shows the region of sky around the massive galaxy cluster Abell 2218, as seen by the SPIRE instrument on Herschel and by the Hubble Space Telescope. On the far left, we have images at the three SPIRE wavelength bands (in the far-infrared part of the spectrum), while the centre image is a false-colour composite. The centre of the galaxy cluster is shown as a white cross-hair, while the large orange-yellow blob just below it is a much more distant galaxy.

On the far right you can see an optical image of the same cluster taken using the Hubble Space Telescope. Working at much shorter, optical wavelengths, the resolution here is much higher. This makes it possible to see the complicated pattern of  arcs caused by the distortion of light as it travels through the gravitational field of the cluster from background sources to the observer. The cluster acts as a gigantic optical system that produces magnified but warped images of very distant galaxies that lie behind it. It’s not designed to act as proper lens, of course, so the images it produces are deformed versions of the original, but they yield sufficient clues to work out the optical properties of the gravitational lens.

Clusters like this tend to contain lots of elliptical galaxies which are not bright in the SPIRE wavebands, so what we see with Herschel is very different from the Hubble view. What Herschel has  done in this particular case is  to reveal that this  gravitational lens produces at least one bright image in the far-infrared part of the spectrum. This is produced by a very distant galaxy which we probably would not have been able to see at all, even with Herschel, had it not been located fortuitously close to a perfect alignment with the optical axis of the Abell 2218 system. Although the image we see is distorted we can still learn a lot about the source that produced using the new data.

(Guest Post) Letter from America

Posted in Science Politics, The Universe and Stuff with tags , , , , , , , , on January 10, 2010 by telescoper

Synchronicity can be a wonderful thing. Yesterday I mentioned the meeting of the Royal Astronomical Society that took place on January 10th 1930. The importance of this event was that it prompted Lemaître to write to Eddington pointing out that he had already (in 1927) worked out a solution of Einstein’s equations describing an expanding space-time; eventually this led to the widespread acceptance of the idea that Hubble‘s observational measurements of redshifts and distances of extragalactic nebulae were evidence that the Universe was expanding. 

Meanwhile, triggered by a recent article in Physics World, I have been having an entertaining electronic exchange with Bob Kirshner concerning a much more recent development about the expanding universe, namely that its expansion is accelerating. Since he’s one of the top experts on this, I thought “What better time  to have my first ever guest post?” and asked Bob if he would like to write something about that. He accepted the invitation, and here is his piece. 

 -0-

Twenty-first century astrophysicists (like Telescoper) are the wrong people to ask to cast your horoscope or maximize your feng-shui.  But even people who spend time in warm, well-lighted buildings staring at computer screens notice the changing seasons.  (This refers to conditions before the recent budget exercise.)  

For me, the pivot of the year comes right after the solstice, while the Christmas wrapping paper is still in the trash can.  Our house in Maine has a window facing south of east.  When the winter sun rises as far south as it ever does, a clear morning lets a blast of light come in one side, straight down the hallway and out the bathroom window. Househenge!  What does it mean? 

It means it is time for the American Astronomical Society’s big meeting.  This rotates its location from Washington DC, this year’s site, to other more-or-less tolerable climates.  Our tribe can mark the passage of the seasons and of the decades by this rhythm.  Never mind all that highfalutin’ stuff about the earth going around the Sun.  Remember that AAS in Austin? What year was that? 

In January of 1998, the cycle of the seasons and of available convention centers of suitable size put the AAS in Washington.  It was an exciting time for me, because we were hot on the trail of the accelerating universe.  We had some great new data from the Hubble Space Telescope (HST), a paper in the press, and Peter Garnavich, my postdoc, was going to give a talk and be part of a press briefing.  This was a big deal and we prepared carefully.  

Adam Riess, who had been my graduate student, was then a Miller Fellow at Berkeley doing the calibration and analysis on our data.  Adam’s notebooks were beginning to show troubling hints of cosmic acceleration.  I thought it would go away. Brian Schmidt, who had also been my student, was then in Australia,  calling the shots on this project.  He didn’t want to get out on a  limb over unpublished hints.  The idea of a cosmological constant was already making him sick to his stomach.  We agreed that in January of 1998, Peter got to say that the supernova data showed the universe was not decelerating very much and would expand forever.  That’s it.  Nothing about acceleration. 

Saul Perlmutter’s Supernova Cosmology Project also prepared a careful press release that reported a low density and predicted eternal cosmic expansion.  A report the next day in the New York Times was pretty tame, except for Ruth Daly speculating on the possibility of a low-density universe coming out of inflation models. Saul was quoted as saying, “I never underestimate the power of a theorist to come up with a new model.”  I have gathered up all the clippings I could find about who said what in Washington. (We used to call them “clippings”.) 

While a few reporters sniffed out the hints of cosmic acceleration in the raw data, in January 1998 nobody was claiming this was a solid result.  The paper from our team with the title Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant didn’t get submitted until March 13, 1998.  The comparable paper from the SCP was submitted September 8, 1998.  These are fine dates in the history of cosmology, but they are not in January.  It’s not for me to say when savants like the Telescoper were convinced we live in an accelerating universe, but I am pretty sure it wasn’t in January 1998.

In January 2009, the sun was once again shining right through our house.  It illuminated the American Physical Society newsletter kept in the upstairs bathroom. One of the features is This Month in Physics History.  If you want to find out about Bubble Chamber progress in January 1955, this is the place. Flipping through the January 2009 issue I was gobsmacked (American slang for “blown away”) to learn we were supposed to celebrate the anniversary of the discovery of cosmic acceleration.  Say what?  In January?  Because of the press releases that said the universe was not going to turn around? 

Being a dutiful type, a Fellow of the APS, and the oldest of the High-Z Team, I thought it was my job to help improve the accuracy of this journal. I wrote them a cheerful (on the third draft) letter explaining that this wasn’t precisely right, and, if they liked real publications as evidence for scientific progress, they might want to wait until March.  A volley of letters ensued, but not at internet speed.  The editor of APS News decided he had had enough education and closed the discussion in July.  The letters column moved on to less controversial matters concerning science and religion and nuclear reactors. 

The rising point of the sun came north, and then marched south again.    Just after the solstice, a beam of light flashed right though our   happy home. 2010!  Google alerts flashed the news.  More brouhahah about the discovery of cosmic acceleration.   Now in Physics World. I am depicted as a surly bull terrier in a crimson tenured chair, clinging desperately to self-aggrandizing notions that actual  publications in real journals are a way to see the order of events.  The philosopher, Robert P. Crease, who wrote this meditation, says he loves priority disputes.  He is making a serious point, that “Eureka!” is not exactly at one moment when you have an international collaboration, improving data sets, and the powerful tools of Bayesian inference at your command. 

But, even in the world of preprint servers, press releases, and blogs without restraint (I am talking about other blogs!), a higher standard of evidence is demanded for a real paper in a real journal.   A page in a notebook, an email, a group meeting, a comment after a colloquium or even an abstract in the AAS Bulletin (whipped up an hour before the deadline and months before the actual talk) is not quite what we mean by “having a result”.  I’m not saying that referees are always helpful, but they make the author anticipate a skeptical reader, so you really want to present a well-crafted  case.

If that’s not so, I would like to have my lifetime’s page charges refunded forthwith: that’s 250 papers x 10 pages/paper/ x $100/ApJ page = $250 000. Send the  check to my office.

So, Telescoper, how is your house aligned?  And why do the Brits put the drains on the outside when you live in such a cold climate?

The Hubble Ultra Deep Field in Three Dimensions

Posted in The Universe and Stuff with tags , , , on January 4, 2010 by telescoper

I came across this video about the Hubble Ultra Deep Field (which I have blogged about before) and thought you might enjoy it. I think it’s fairly self-explanatory too!

Back Early…

Posted in The Universe and Stuff with tags , , , , , on September 11, 2009 by telescoper

As a very quick postscript to my previous post about the amazing performance of Hubble’s spanking new camera, let me just draw attention to a fresh paper on the ArXiv by Rychard Bouwens and collaborators, which discusses the detection of galaxies with redshifts around 8 in the Hubble Ultra Deep Field (shown below in an earlier image) using WFC3/IR observations that reveal galaxies fainter than the previous detection limits.

Amazing. I remember the days when a redshift z=0.5 was a big deal!

To put this in context and to give some idea of its importance, remember that the redshift z is defined in such a way that 1+z is the factor by which the wavelength of light is stretched out by the expansion of the Universe. Thus, a photon from a galaxy at redshift 8 started out on its journey towards us (or, rather, the Hubble Space Telescope) when the Universe was compressed in all directions relative to its present size by a factor of 9. The average density of stuff then was a factor 93=729 larger, so the Universe was a much more crowded place then compared to what it’s like now.

Translating the redshift into a time is trickier because it requires us to know how the expansion rate of the Universe varies with cosmic epoch. The requires solving the equations of a cosmological model or, more realistically for a Friday afternoon, plugging the numbers into Ned Wright’s famous cosmology calculator.

Using the best-estimate parameters for the current concordance cosmology reveals that at redshift 8, the Universe was only about 0.65 billion years old (i.e. light from the distant galaxies seen by HST set out only 650 million years after the Big Bang). Since the current age of the Universe is about 13.7 billion years (according to the same model), this means that the light Hubble detected set out on its journey towards us an astonishing 13 billion years ago.

More importantly for theories of galaxy formation and evolution, this means that at least some galaxies must have formed very early on, relatively speaking, in the first 5% of the time the Universe has been around for until now.

These observations are by no means certain as the redshifts have been determined only approximately using photometric techniques rather than the more accurate spectroscopic methods, but if they’re correct they could be extremely important.

At the very least they provide even stronger motivation for getting on with the next-generation space telescope, JWST.

Hubble Flash

Posted in The Universe and Stuff with tags , , , , , on September 9, 2009 by telescoper

Just a quick post to point out that brand new “Early Release” images have just appeared following the recent refurbishment of the Hubble Space Telescope.

You can read the accompanying press release here, so I’ll just post this brief description:

These four images are among the first observations made by the new Wide Field Camera 3 aboard the upgraded NASA Hubble Space Telescope.

The image at top left shows NGC 6302, a butterfly-shaped nebula surrounding a dying star. At top right is a picture of a clash among members of a galactic grouping called Stephan’s Quintet. The image at bottom left gives viewers a panoramic portrait of a colorful assortment of 100,000 stars residing in the crowded core of Omega Centauri, a giant globular cluster. At bottom right, an eerie pillar of star birth in the Carina Nebula rises from a sea of greenish-colored clouds.

My own favourite has to be Stephan’s Quintet, but they all look pretty fantastic.

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