Archive for Herschel

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.
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Dust

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

I was reading through a collection of poems by Rupert Brooke this lazy sunday afternoon and found this. I haven’t posted much poetry recently so thought I’d add it here. I’m sure my many friends who work on astrophysical dust will enjoy it, especially those involved with the European Space Agency’s  Herschel Space Observatory. Apparently they’re all “passionate about dust”. If that’s true I wonder if one of them might want to write a wikipedia entry on the subject, because for some reason there isn’t one…

When the white flame in us is gone,
And we that lost the world’s delight
Stiffen in darkness, left alone
To crumble in our separate night;

When your swift hair is quiet in death,
And through the lips corruption thrust
Has still’d the labour of my breath –
When we are dust, when we are dust !

Not dead, not undesirous yet,
Still sentient, still unsatisfied,
We’ll ride the air, and shine, and flit,
Around the places where we died,

And dance as dust before the sun,
And light of foot and unconfined,
Hurry from road to road, and run
About the errands of the wind.

And every mote, on earth or air,
Will speed and gleam, down later days,
And like a secret pilgrim fare
By eager and invisible ways,

Nor ever rest, nor ever lie,
Till, beyond thinking, out of view,
One mote of all the dust that’s I
Shall meet one atom that was you.

Then in some garden hush’d from wind,
Warm in a sunset’s afterglow,
The lovers in the flowers will find
A sweet and strange unquiet grow

Upon the peace; and, past desiring,
So high a beauty in the air,
And such a light, and such a quiring,
And such a radiant ecstasy there,

They’ll know not if it’s fire, or dew,
Or out of earth, or in the height,
Singing, or flame, or scent, or hue,
Or two that pass, in light, to light,

Out of the garden, higher, higher. . . .
But in that instant they shall learn
The shattering ecstasy of our fire,
And the weak passionless hearts will burn

And faint in that amazing glow,
Until the darkness close above;
And they will know – poor fools, they’ll know!
One moment, what it is to love.

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.

Among the Crachach

Posted in Education, Politics with tags , , , , on June 6, 2010 by telescoper

Catching up on the news by looking through my copy of last week’s Times Higher, I came across an account of a speech made by Welsh Assembly Minister Leighton Andrews about the Future of Higher Education in Wales. I mentioned this was coming up in an earlier post about the state of the Welsh university system, but wasn’t able to attend the lecture. Fortunately, however the text of the lecture is available for download here.

There is some discussion of positives  in the speech, including a specific enthusiastic mention of

the involvement of the School of Physics and Astronomy in the international consortium which built the Herschel Space Observatory.

I was pleased to see that, especially since much of the rest of it is extremely confrontational. Much of it focusses on the results of a recent study by accountants PriceWaterhouseCooper that revealed, among other things, that  52% of the funding provided by the Welsh Assembly Government for higher education goes on adminstration and support services, with only 48% to teaching and research. Mr Andrews suggests that about 20% of the overall budget could be saved by reducing duplication and introducing shared services across the sector.

I can’t comment on the accuracy of the actual figures in the report, but I wouldn’t be surprised if they were correct.  They might shock outsiders to the modern higher education system but most universities – not just those in Wales – seem to employ at least as many administrative staff and support staff as “front-line” teachers and researchers. I’m likewise sure that the Welsh Assembly employs many more such staff than there are Members…

Within academic Schools we need to employ staff to handle financial matters, student records, recruitment, admissions,  and general day-to-day administration. On top of that we have technical staff, to support both research and teaching laboratories as well as computing support staff. Add them all together and you definitely have a number comparable to the number of academic staff,  but  they don’t account for 52% of our salary bill because they are generally paid less than lecturers and professors. The mix in our School is no doubt related to the specific demands of physics and astronomy, but these staff all provide essential services and if they weren’t there, the academic staff would have to spend an even greater part of their time doing such things themselves.

As well as the staff working in individual Schools there are central administrative departments (in Cardiff they’re called “directorates”) which don’t employ academics at all. I have no idea what fraction of Cardiff’s budget goes on these things, but I suspect it’s  a big slice. My own anecdotal experience is that some of these are helpful and efficient while others specialise in creating meaningless bureaucratic tasks for academic staff to waste their time doing. I think such areas are where 20% savings might be achievable, but that would depend on the University having fewer and less complicated “initiatives” to respond to from the WAG.

The Times Higher story discusses the (not entirely favourable) reaction from various quarters to Mr Andrews speech, so I won’t go into it in any more detail here.

However, I was intrigued by one word I found in the following paragraph

 I was interested to learn recently that some members of university governing bodies have been appointed on the basis of a phone call. Who you know not what you know. It appears that HE governance in post devolution Wales has become the last resting place of the crachach.

Crachach? Being illiterate in the Welsh language this was a new one on me. However, I found an article on the BBC Website  that revealed all.

The term used to denote local gentry but 21st century crachach is the Taffia, the largely Welsh-speaking elite who dominate the arts, culture and media of Wales and to a lesser extent its political life.

It goes onto say

The Vale, Pontcanna and Whitchurch are crachach property hotspots while barn conversions in Llandeilo and cottages in Newport, Pembrokeshire, provide weekend retreats.

Hang on. Pontcanna? That’s where I live! I wonder if they let foreigners join the crachach, provided of course they learn the Welsh language? I note however that “arts culture and the media” is their remit, so science apparently doesn’t count. Perhaps I could start a scientific wing? Maybe those Welsh lessons will be useful after all. I’m told that the crachach always manage to get tickets for the big rugby matches…

On a more serious note, however, that part of Leighton Andrews’ speech stressed the importance of university governance. If he’s true to his word he should look into the Mark Brake affair. I think the taxpayers of Wales have a right to know what’s been going on.

Clustering in the Deep

Posted in Bad Statistics, The Universe and Stuff with tags , , , , , , on May 27, 2010 by telescoper

I couldn’t resist a quick lunchtime post about the results that have come out concerning the clustering of galaxies found by the HerMES collaboration using the Herschel Telescope. There’s quite a lengthy press release accompanying the new results, and there’s not much point in repeating the details here, so I’ll just show a wonderful image showing thousands of galaxies and their far-infrared colours.

Image Credit: European Space Agency, SPIRE and HERMES consortia

According to the press release, this looks “like grains of sand”. I wonder if whoever wrote the text was deliberately referring to Genesis 22:17?

.. they shall multiply as the stars of the heaven, and as the grains of sand upon the sea shore.

However, let me take issue a little with the following excerpt from said press release:

While at a first glance the galaxies look to be scattered randomly over the image, in fact they are not. A closer look will reveals that there are regions which have more galaxies in, and regions that have fewer.

A while ago I posted an item asking what “scattered randomly” is meant to mean. It included this picture

This is what a randomly-scattered set of points actually looks like. You’ll see that it also has some regions with more galaxies in them than others. Coincidentally, I showed the same  picture again this morning in one of my postgraduate lectures on statistics and a majority of the class – as I’m sure do many of you seeing it for the first time –  thought it showed a clustered pattern. Whatever “randomness” means precisely, the word certainly implies some sort of variation whereas the press release implies the opposite. I think a little re-wording might be in order.

What galaxy clustering statistics reveal is that the variation in density from place-to-place is greater than that expected in a random distribution like that shown. This has been known since the 1960s, so it’s not  the result that these sources are clustered that’s so important. In fact, The preliminary clustering results from the HerMES surveys – described in a little more detail in a short paper available on the arXIv – are especially  interesting because they show that some of the galaxies seen in this deep field are extremely bright (in the far-infrared), extremely distant, high-redshift objects which exhibit strong spatial correlations. The statistical form of this clustering provides very useful input for theorists trying to model the processes of galaxy formation and evolution.In particular, the brightest objects at high redshift have a propensity to appear preferentially in dense concentrations, making them even more strongly clustered than rank-and-file galaxies. This fact probably contains important information about the environmental factors responsible for driving their enormous luminosities.

The results are still preliminary, but we’re starting to see concrete evidence of the impact Herschel is going to have on extragalactic astrophysics.

Herschel’s First Year in Space

Posted in The Universe and Stuff with tags , , on May 14, 2010 by telescoper

Just about to journey to the RAS for the Annual General Meeting  and the last club dinner before the summer break, I’m reminded by a tweet from Chris North that it’s exactly a year since we gathered nervously, fortified by booze, to watch the launch of the far-infrared observatory Herschel, together with its sister spacecraft Planck.  I haven’t got time to write much about this because I’ve got a train to catch, but you can in any case find a nice retrospective of the Herschel’s first year in space here. I couldn’t resist, however, putting up the nice video that’s been put together by the European Space Agency to mark the anniversary.

It’s all  been going swimmingly on the Herschel front since the launch, and the first science papers have been making their way onto the ArXiv this week. Thankfully it’s not been quite the deluge that I’d feared, more of a steady stream. I’ve even had a chance to read a few of them.

The next major milestone coming up will be announcement of opportunity for open time access (OT1) which will  be released on 20th May with a deadline of 22nd July. I’m sure the huge success that Herschel has been so far will mean a lot of people putting in proposals. There is talk of putting in a proposal for a big cosmology survey – a sort of son of ATLAS and HERMES –  which will be good timing for me and my little team at Cardiff because our theoretical models are almost ready to rumble…

Anyway, here’s to at least another three years of Herschel, although I’ll have to wait until this evening to raise a glass!

Starchild

Posted in The Universe and Stuff with tags , , , on May 10, 2010 by telescoper

It’s been a busy day today,  so I’ve decided to be lazy and plunder the online stack of juicy Herschel images for a pretty picture to show. This one has done the rounds in the popular media recently, which is not surprising given how strange it looks.

Image Credits: ESA / PACS & SPIRE Consortium, Dr. Annie Zavagno, LAM, HOBYS Key Programme Consortia

This image shows a Galactic bubble (technically an HII emission region) called RCW 120 that contains an embryonic star that looks set to turn into one of the brightest stars in the Galaxy. It lies about 4300 light-years away. The star is not visible at these infrared avelengths but its radiation pressure pushes on the surrounding dust and gas. In the approximately 2.5 million years the star has existed, it has raised the density of matter in the bubble wall by so much that the material trapped there can now collapse to form new stars.

The bright knot to the right of the base of the bubble is an unexpectedly large, embryonic star, triggered into formation by the power of the central star. Herschel’s observations have shown that it already contains between 8-10 times the mass of our Sun. The star can only get bigger because it is surrounded by a cloud containing an additional 2000 solar masses.

Not all of that will fall onto the star, because even the largest stars in the Galaxy do not exceed 150 solar masses. But the question of what stops the matter falling onto the star is an astrophysical puzzle. According to theory, stars should stop forming at about 8 solar masses. At that mass they should become so hot that they shine powerfully at ultraviolet wavelengths exerting so much radiation pressure that it should push the surrounding matter away, much as the central star did to form this bubble in the first place. But this mass limit is must be exceeded sometimes, otherwise there would be no giant stars in the Galaxy. So astronomers would like to know how some stars can seem to defy physics and grow so large. Is this newly discovered stellar embryo destined to grow into a stellar monster? At the moment, nobody knows but further analysis of this Herschel image could give us invaluable clues.

It also reminds me a little bit of the Starchild from 2001: A Space Odyssey…