Maybe ET’s Calling, But We Have the Wrong Phone

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To date, SETI (Search for ExtraTerrestrial Intelligence) has focused on ETs who ‘phone home’ using the radio part of the electromagnetic spectrum, and even a very small region within that.

But what if ET’s phone doesn’t use radio waves? Sure the xkcd comic, is funny, but maybe it points to a deep flaw in our attempts to contact, or hear from, an ETI?

When Giuseppe Cocconi and Philip Morrison suggested the possibility of interstellar communication via electromagnetic waves in a 1959 paper in Nature, only radio was feasible, as we then had the ability to detect only artificial radio signals, if produced by ETIs with 1959 human technology. Since then we’ve developed the ability to detect a laser signal, brighter than the Sun (if only for a nanosecond) if it came from a source several light-years away … but lasers weren’t invented then.

What might ET’s equivalent of ants’ pheromones be?

Back in 1959 if you’d said that the Earth would, within a mere half century, started to go ‘radio quiet’, not many people would have taken you seriously. Yet that’s exactly what’s happened! Free to air (FTA) broadcasting, especially for TV, is being replaced by TV delivered over coaxial cable, optical fibers, or even the phone company’s twisted copper pairs. And where it’s continuing, as in satellite TV broadcasting, its power has dropped (today’s digital formats are more efficient than the old analog ones). Military radars, the brightest source of artificial radio waves by far, no longer broadcast in a single channel, but hop, rapidly, from frequency to frequency, to avoid jamming.

“Our improving technology is causing the Earth to become less visible,” says astronomer Frank Drake, SETI’s paterfamilias. “If we are the model for the universe, that is bad news.”

In the past half century SETI researchers have expanded the scope of their searches. Not only are far more radio channels being examined, but artificial signals in the optical are being sought too. How to decide which of the billions or trillions of possible radio channels to search? For example, the Allen Telescope Array will, when built, monitor a billion channels between 0.5 and 11 GHz – but that’s a trivial fraction of the entire radio waveband. Some ideas, however, seem cute; for example, the SETI Institute’s Gerald Harp has proposed searching at 4.462336275 gigahertz, in what’s called the PiHI range, because it’s the hydrogen atom’s emission frequency times pi. More seriously, Harvard University’s Paul Horowitz says optical SETI programs should really look at infrared frequencies “Stars are darker in the infrared and lasers are brighter and the smog goes away,” Horowitz says. Infrared allows astronomers to see into the galactic center, where dust scatters visible light.

There’s something rather ironic about SETI today; on the one hand, we recognize that our initial hopes were far too high, being based on overly simplistic assumptions; on the other, the tremendous progress in finding exoplanets has given us greater and greater certainty that Earth-like planets not only exist, but are, very likely, common. “All of astronomy has come to embrace this idea that there must be life out there,” says Harp.

So how to address the fact that we simply do not know what sorts of technologies a civilization like ours may have, a century or a millennium from now? After all, as Drake says “We are very conservative at SETI, we assume in our searches the existence of only things we ourselves have and know how to make.” Other scientists, and SETI enthusiasts, have proposed hunting in different electromagnetic realms, like gamma rays. Spacecraft that rely on nuclear fusion or antimatter-matter annihilation as a power source might produce such rays. But standard SETI strategy does not embrace such “speculative” scenarios.

SETI researchers, some say, should also contemplate what technologies supersmart aliens might possess and seek out the corresponding signals. In a 2008 arXiv paper, “Galactic Neutrino Communication“, John Learned of the University of Hawaii at Manoa suggested that ET could be sending beams of neutrinos Earth’s way. Energy requirements for such a beam make that scenario seem implausible, but not necessarily impossible. Detectors currently under construction, such as IceCube at the South Pole, could spot unexpected stray neutrinos. If a few with the same energy came from the same direction, astronomers would know something screwy was up.

In another paper, “The Cepheid Galactic Internet“, Learned suggests that ET could send a signal using a neutrino beam to deliver energy to a Cepheid variable. A Cepheid “blows up and comes crashing back down,” he says. “And the energy builds up and it blows again, like a geyser.” ET could leverage a Cepheid’s inherent instability by delivering a boost of energy that messes with the star’s schedule. Looking through existing data could reveal whether such meddling has occurred. “All that is needed is people analyzing for other reasons to do their analyses in another way,” Learned says.

Drake and most others agree that SETI’s approach should be multidirectional – let a thousand alien hunters bloom. The only ideas that don’t do anybody any good, Horowitz says, are the ones for which there is no conceivable way to look. “I’d like to keep an open mind,” he says, “but not so much that my brain falls out.”

Physicist Paul Davies of Arizona State University in Tempe, however, suggests that researchers don’t need to know what to look for. Find the fishy thing first, and then argue about its origin, he says.

As Davies has argued, maybe discovering ET does indeed depend on a thought revolution. Fifty years of signal-less searching suggests that the problem could lie not with the aliens among the stars, but with ourselves.

Maybe the sentient ants should not give up, just yet.

Sources: Science News. Cocconi and Morrison’s 1959 Nature paper (copyright Nature)

Universe Puzzle No. 13

How did you do in last week’s Universe Puzzle? Did you figure out an answer, but didn’t write up your reasons why it was the best?

Do you enjoy these puzzles? What do you particularly like? Dislike? Would like to see changed? Would like to see more of? Let me know please!

Once again, this week’s puzzle requires you to cudgel your brains a bit and do some lateral thinking (five minutes spent googling likely won’t be enough). But, as with all Universe Puzzles, this is a puzzle on a “Universal” topic – astronomy and astronomers; space, satellites, missions, and astronauts; planets, moons, telescopes, and so on.

Say you’re at a friend’s place for a party. They’re playing some 60’s rock music, and a catchy song comes round. You wonder who the band is, and someone says “it’s the most famous 60’s band that you’ve never heard of!” (perhaps it’s Herman’s Hermits).

Well, this week’s Universe Puzzle is:

Who is the most famous astronaut you’ve never heard of?

And for ‘astronaut’ let’s include cosmonauts, taikonauts, and so on.

Be sure to explain your pick.

Update: answer posted below.

There certainly is not just one best answer!

You, dear commenters, are the judges: which of the answers below do you think is the best?

Universe Puzzle will be taking a bit of break, so there won’t be one next week. However, I really would appreciate your feedback: which of the 13 puzzles so far did you most like? which did you least like? what sort of puzzles would you like to see in future?

Universe Puzzle No. 12

How did you do in last week’s Universe Puzzle? Did you easily find out where the green valley is, but have no clue as to why it’s called a ‘valley’?

Do you enjoy these puzzles? What do you particularly like? Dislike? Would like to see changed? Would like to see more of? Let me know please!

Once again, this week’s puzzle requires you to cudgel your brains a bit and do some lateral thinking (five minutes spent googling likely won’t be enough). But, as with all Universe Puzzles, this is a puzzle on a “Universal” topic – astronomy and astronomers; space, satellites, missions, and astronauts; planets, moons, telescopes, and so on.

Which is the “odd one out”? And why?
α, β, γ, μ, ν, and τ.

In case the Greek symbols don’t display properly, these are (lower case, or small) alpha, beta, gamma, mu, nu, and tau.

UPDATE: Answer has been posted below.

There are, of course, many answers. For example, τ (tau) is alone, because neither of its two neighbors in the Greek alphabet are in the list. But that’s not a particularly good answer, and this week’s puzzle asks for the best answer (which may be τ (tau)!), so the explanation of your choice is what counts.

I think Hon. Salacious B. Crumb’s answer is very good (“tau is the odd one out. The rest are al rings of the planet Uranus by increasing radius from the planet’s disk. alpha, beta, gamma are inner rings, nu and mu are the outmost rings.“)

I also like Navneeth’s (“alpha, because it’s a composite “particle” while the others are truly elementary (as far as we know)“) – gopher65 gave much the same answer, iantresman’s (“alpha particles are the only non-fermions. Neutrinos (nu) are the only ones to come in different flavours“), and the several of you who picked gamma because the photon is massless (though I think iantresman’s “it’s the only gauge boson” is a better reason for choosing it; you could also say it’s the only force carrier particle).

Star designations? If someone had come up with a good answer along those lines, they’d’ve got my vote; but, as far as I know there is nothing “odd” about any of these Greek letters.

My own answer was the tau … it’s the only particle as yet undetected, directly, by any spacecraft or Earth-based facility, originating out in space (Fermi detects gammas; plenty of instruments on spacecraft detect alpha particles, electrons, and muons; and neutrinos from the Sun and SN1987A have been detected; but no taus!)

Check back next week for another Universe Puzzle!

Universe Puzzle No. 11

How did you do in last week’s Universe Puzzle?

Do you enjoy these puzzles? What do you particularly like? Dislike? Would like to see changed? Would like to see more of? Let me know please!

Once again, this week’s puzzle requires you to cudgel your brains a bit and do some lateral thinking (five minutes spent googling likely won’t be enough). But, as with all Universe Puzzles, this is a puzzle on a “Universal” topic – astronomy and astronomers; space, satellites, missions, and astronauts; planets, moons, telescopes, and so on.

Where is the green valley? What are the hills/mountain range(s)/ridges which border it? How did it get its name?

UPDATE: Answer has been posted below.

The green valley I had in mind is indeed the region in a color-magnitude diagram of galaxies, between the red sequence and blue cloud. In this case five minutes spent googling would have given you this answer (so not really a Universe Puzzle).

It got its name because, first, between red and blue comes green, and second because one way of representing the number of galaxies per unit area in a chart (or graph) of their color vs luminosity is to draw contours (if the chart is representing hundreds of thousands of galaxies then plotting them all as points becomes visually bland, shall we say). And what does a chart with contour lines on it remind you of? A topographic map! So the red sequence and blue cloud would be ridges or mountains, and in between would be a …. valley.

At the time I accessed it, the Wikipedia entry is a good summary (with Wikipedia you have to be very careful that the contents of an entry haven’t changed!)

Check back next week for another Universe Puzzle!

GOODS, Under Astronomers’ AEGIS, Produce GEMS

No, not really (but I got all three key words into the title in a way that sorta makes sense).

Astronomers, like most scientists, just love acronyms; unfortunately, like most acronyms, on their own the ones astronomers use make no sense to non-astronomers.

And sometimes not even when written in full:
GOODS = Great Observatories Origins Deep Survey; OK that’s vaguely comprehensible (but what ‘origins’ is it about?)
AEGIS = All-wavelength Extended Groth strip International Survey; hmm, what’s a ‘Groth’?
GEMS = Galaxy Evolution from Morphology and SEDs; is Morphology the study of Morpheus’ behavior? And did you guess that the ‘S’ stood for ‘SEDs’ (not ‘Survey’)?

But, given that these all involve a ginormous amount of the ‘telescope time’ of the world’s truly great observatories, to produce such visually stunning images as the one below (NOT!), why do astronomers do it?

GEMS tile#58 (MPIfA)


Astronomy has made tremendous progress in the last century, when it comes to understanding the nature of the universe in which we live.

As late as the 1920s there was still debate about the (mostly faint) fuzzy patches that seemed to be everywhere in the sky; were the spiral-shaped ones separate ‘island universes’, or just funny blobs of gas and dust like the Orion nebula (‘galaxy’ hadn’t been invented then)?

Today we have a powerful, coherent account of everything we see in the night sky, no matter whether we use x-ray eyes, night vision (infrared), or radio telescopes, an account that incorporates the two fundamental theories of modern physics, general relativity and quantum theory. We say that all the stars, emission and absorption nebulae, planets, galaxies, supermassive black holes (SMBHs), gas and plasma clouds, etc formed, directly or indirectly, from a nearly uniform, tenuous sea of hydrogen and helium gas about 13.4 billion years ago (well, maybe the SMBHs didn’t). This is the ‘concordance LCDM cosmological model’, known popularly as ‘the Big Bang Theory’.

But how? How did the first stars form? How did they come together to form galaxies? Why did some galaxies’ nuclei ‘light up’ to form quasars (and others didn’t)? How did the galaxies come to have the shapes we see? … and a thousand other questions, questions which astronomers hope to answer, with projects like GOODS, AEGIS, and GEMS.

The basic idea is simple: pick a random, representative patch of sky and stare at it, for a very, very long time. And do so with every kind of eye you have (but most especially the very sharp ones).

By staring across as much of the electromagnetic spectrum as possible, you can make a chart (or graph) of the amount of energy is coming to us from each part of that spectrum, for each of the separate objects you see; this is called the spectral energy distribution, or SED for short.

By breaking the light of each object into its rainbow of colors – taking a spectrum, using a spectrograph – you can find the tell-tale lines of various elements (and from this work out a great deal about the physical conditions of the material which emitted, or absorbed, the light); “light” here is shorthand for electromagnetic radiation, though mostly ultraviolet, visible light (which astronomers call ‘optical’), and infrared (near, mid, and far).

By taking really, really sharp images of the objects you can classify, categorize, and count them by their shape, morphology in astronomer-speak.

And because the Hubble relationship gives you an object’s distance once you know its redshift, and as distance = time, sorting everything by redshift gives you a picture of how things have changed over time, ‘evolution’ as astronomers say (not to be confused with the evolution Darwin made famous, which is a very different thing).

GOODS

The great observatories are Chandra, XMM-Newton, Hubble, Spitzer, and Herschel (space-based), ESO-VLT (European Southern Observatory Very Large Telescope), Keck, Gemini, Subaru, APEX (Atacama Pathfinder Experiment), JCMT (James Clerk Maxwell Telescope), and the VLA. Some of the observing commitments are impressive, for example over 2 million seconds using the ISAAC instrument (doubly impressive considering that ground-based facilities, unlike space-based ones, can only observe the sky at night, and only when there is no Moon).

There are two GOODS fields, called GOODS-North and GOODS-South. Each is a mere 150 square arcminutes in size, which is tiny, tiny, tiny (you need five fields this size to completely cover the Moon)! Of course, some of the observations extend beyond the two core 150 square arcminutes fields, but every observatory covered every square arcsecond of either field (or, for space-based observatories, both).

GOODS-N ACS fields (GOODS/STScI)

GOODS-N is centered on the Hubble Deep Field (North is understood; this is the first HDF), at 12h 36m 49.4000s +62d 12′ 58.000″ J2000.
GOODS-S ACS fields (GOODS/STScI)

GOODS-S is centered on the Chandra Deep Field-South (CDFS), at 3h 32m 28.0s -27d 48′ 30″ J2000.

The Hubble observations were taken using the ACS (Advanced Camera for Surveys), in four wavebands (bandpasses, filters), which are approximately the astronomers’ B, V, i, and z.

Extended Groth Strip fields (AEGIS)

AEGIS

The ‘Groth’ refers to Edward J. Groth who is currently at the Physics Department of Princeton University. In 1995 he presented a ‘poster paper’ at the 185th meeting of the American Astronomical Society entitled “A Survey with the HST“. The Groth strip is the 28 pointings of the Hubble’s WFPC2 camera in 1994, centered on 14h 17m +52d 30′. The Extended Groth Strip (EGS) is considerably bigger than the GOODS fields, combined. The observatories which have covered the EGS include Chandra, GALEX, the Hubble (both NICMOS and ACS, in addition to WFPC2), CFHT, MMT, Subaru, Palomar, Spitzer, JCMT, and the VLA. The total area covered is 0.5 to 1 square degree, though the Hubble observations cover only ~0.2 square degrees (and only 0.0128 for the NICMOS ones). Only two filters were used for the ACS observations (approximately V and I).

I guess you, dear reader, can work out why this is called an ‘All wavelength’ and ‘International Survey’, can’t you?

GEMS' ACS fields (MPIfA)

GEMS

GEMS is centered on the CDFS (Chandra Deep Field-South, remember?), but covers a much bigger area than GOODS-S, 900 square arcminutes (the largest contiguous field so far imaged by the Hubble at the time, circa 2004; the COSMOS field is certainly larger, but most of it is monochromatic – I band only – so the GEMS field is the largest contiguous color one, to date). It is a mosaic of 81 ACS pointings, using two filters (approximately V and z).

Its SEDs component comes largely from the results of a previous large project covering the same area, called COMBO-17 (Classifying Objects by Medium-Band Observations – a spectrophotometric 17-band survey).

Sources: GOODS (STScI), GOODS (ESO), AEGIS, GEMS, ADS
Special thanks to reader nedwright for catching the error re GEMS (and thanks to to readers who have emailed me with your comments and suggestions; much appreciated)

Hubble, Renewed, Reinvigorated, Raring to Go


Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today has featured highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the last two years, to April 2010.

The stakes for the fifth, and final, Hubble servicing mission couldn’t have been higher; not only were two new instruments to be installed (a relatively straight-forward task), not only was much of key infrastructure to be replaced (batteries, fine-guidance sensors, thermal blankets), but intricate repairs had to be performed on the two most complicated instruments (ACS and STIS), something not in the design, something difficult enough in a well-appointed lab on Earth much less done by astronauts in bulky space suits. The servicing mission was postponed, as it became clear that the work to be done was more extensive; but in May 2009 STS-125, involving five full days of space walks and 11 days in space, met all the objectives.

And a little under four months later, after extensive testing and calibration, the Hubble was back in the astronomy business.

This image is the Hubble Ultra-Deep Field (HUDF), as seen by WFC3 in the infrared (now that Hubble Zoo is live, you will have a chance to analyze fields like this yourself!)
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MACS J0025.4-1222 (NASA, ESA, CXC, M. Bradac (UC, Santa Barbara), S. Allen (Stanford) Click for zoomable

MACS J0025.4-1222 is not as well known as the Bullet Cluster, but perhaps it should be. One of the really big, open questions in astronomy today is the nature of dark matter; observations of the Bullet Cluster point to dark matter being a form of matter that does not interact with normal (baryonic) matter, except gravitationally. But perhaps the Bullet Cluster is just an anomaly, or perhaps we don’t really understand what’s going on? In astronomy, as in all science, independent verification is key, and what better way to provide that, for dark matter, than to observe another interacting cluster? “Revealing the Properties of Dark Matter in the Merging Cluster MACS J0025.4-1222” is the paper to read, and Hubble’s ACS provided many of the key observations.
Fomalhaut's exoplanet (NASA, ESA, P. Kalas (UC, Berkeley))

A direct image of an exoplanet, and an estimate of its orbit; the coronagraph on ACS blocked out most of the light of Fomalhaut so its planet – Fomalhaut b – could be seen.

Arp194 (NASA, ESA, Hubble Heritage Team (STScI/AURA)) Click for zoomable image

WFPC2 was removed during SM4 (and replaced by WFC3); this was Hubble’s workhorse camera for some 16 years, the camera which just kept on working. It is fitting then that one of its last images is of Arp 194, dubbed ‘the fountain of youth’.

Happy Birthday Hubble!

Previous articles:
Hubble’s Late Teen Years: It Was the Best of Times, It Was the Worst of Times
Hubble Turns Sixteen, and Just Keeps on Working
Hubble Enters its Teen Years, More Powerful, More Ambitious
Hubble’s 20th: At Least as Good as Any Human Photographer
Hubble’s 10th Birthday Gift: Measurement of the Hubble Constant
Hubble at 8: So Many Discoveries, So Quickly
Hubble’s 20 Years: Now We Are Six
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today

Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System

Click on Hubble: Galaxy Zoo Now Includes HST Images

The Hubble Space Telescope is 20 years old on Saturday and, to mark this anniversary, all the world’s space and astronomy fans have a chance to become part of the Hubble team.

As part of the birthday celebrations NASA’s Space Telescope Science Institute and the online astronomy project Galaxy Zoo are making some 200,000 Hubble images of galaxies available to the public at Galaxy Zoo (www.galaxyzoo.org). They hope that volunteers looking for their own favorite galaxies will join forces to give the venerable telescope a present – classifications of each galaxy which will help astronomers understand how the Universe we see around us formed.

But there’s more to it than that; remember Hanny and the Voorwerp? The Green Peas? Mitch’s mysterious star? For every unexpected Galaxy Zoo discovery there are likely a dozen Hubble Zoo ones.

“The large surveys that Hubble has completed allow us to trace the Universe’s evolution better than ever before,” said University of Nottingham astronomer and Galaxy Zoo team member Dr. Steven Bamford. “The vast majority of these galaxies will never have been viewed by anyone, and yet we need human intuition to make the most of what they are telling us”.

More than 250,000 people have already contributed to Galaxy Zoo since its launch in 2007, but so far they have been looking only at the ‘local’ Universe, up to a hundred million or so light-years away. The galaxies in HubbleZoo are from some of the big surveys, such as GOODS, and the images were processed by the Galaxy Zoo team alongside Roger Griffith at JPL and the Space Telescope Science Institute (see this article, from my Universe Today series on the Hubble, for more details on GOODS).

“Hubble will enable us to look back in time, to the era when many of the galaxies we see today were forming,” said Dr. Chris Lintott of Oxford University, Galaxy Zoo principal investigator. “As a kid I always wanted a time machine for my birthday, but this is the next best thing!”

“We never dreamt that people would find so many fascinating objects in the original Galaxy Zoo,” said Yale University astronomer Dr. Kevin Schawinski. “Who knows what’s hiding in the Hubble images?” Lintott added: “As we recovered from the launch of the original Galaxy Zoo, we knew we’d want to have a look at Hubble. Now we realize the images are better and the galaxies weirder than we ever thought they would be.”

And how will you, dear zooite-to-be, contribute, and find a hidden gem among the Hubble galaxies? Once you log in, you will asked to answer simple questions about what you are seeing, for example, identifying the number of spiral arms visible, or spotting galaxies in the process of merging. And if you spot something odd, you can bring it to the attention of other zooites, and the Zoo astronomers.

Arp147 (Credit: NASA, ESA, and M. Livio (STScI))

“Every galaxy is special in its own way,” said Stuart Lynn of Oxford University, Galaxy Zoo team member, “but some are worthy of individual attention. Anyone combing through the data using our site could make a spectacular discovery, and that would be the best birthday present of all.”

Galaxy SDSS J100213.52+020645.9 (SDSS)

Galaxy SDSS J100213.52+020645.9 (Hubble)

Sources: NASA, HubbleSite, Oxford University, Galaxy Zoo Forum The two images above, of a galaxy called SDSS J100213.52+020645.9, highlight the sharpness and depth of the Hubble’s images (the SDSS telescope and the Hubble have primary mirrors of approximately the same diameter).

Hubble’s Late Teen Years: It Was the Best of Times, It Was the Worst of Times

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Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today will feature highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the period April 2006 to April 2008.

The image of the Antennae galaxies, above, released on October, 17 2006, is bitter-sweet. On the one hand it’s a stunning image, even more spectacular than the one taken nine years earlier with WFPC2; on the other the star instrument which took it, Advanced Camera for Surveys (ACS), failed first in July 2006, and again in January 2007. On top of that, one by one the Hubble’s gyroscopes started to fail, and its batteries too. In October 2006 the new NASA Administrator, Mike Griffin, had given the go-ahead for one last Space Shuttle mission to the Hubble, for a final servicing. With failure following failure, the servicing mission become more and more complex, and it was hard to maintain optimism in the future of Hubble.

The ACS’ failure came after it had completed its part of the Cosmic Evolution Survey (COSMOS), which was a coordinated project involving many of the world’s leading observatories, both on the ground and in space (a bit like GOODS, which I covered in yesterday’s article). Among the successes of COSMOS was this 3D map of the distribution of dark matter.

3D Dark Matter distribution (Credit: NASA, ESA and R. Massey (Caltech)) Click for zoomable image


(NASA)

The way the Hubble keeps its gaze steady, during the sometimes quite long exposures of some of its instruments, is a marvel of modern engineering. Central to this intricate system is a set of sensors, called the Fine Guidance Sensors (FGS), which were designed to do science too, specifically astrometry.

The sensors aim the telescope by locking onto guide stars and measure the position of the telescope relative to the object being viewed. Adjustments based on these constant, minute measurements keep Hubble pointed precisely in the right direction.

R136 in 30 Dor (Credit: NASA , John Trauger (JPL), James Westphal (CIT))

One of most interesting results from the FGS is the finding that the main star in the R136 cluster in the 30 Doradus nebula (better known as the Tarantula Nebula in the Large Magellanic Cloud) – R136a – is actually a triple (“Hubble Space Telescope Fine Guidance Sensor interferometric observations of the core of 30 Doradus“). Once upon a time the entire cluster was thought to be a single star, the most massive one ever seen; today R136a1 weighs in at ‘merely’ some 30 to 80 sols.
Comet Holmes (Hubble image credit: NASA, ESA, H. Weaver (JHU Applied Physics Laboratory); ground-based image credit: A. Dyer, Alberta, Canada)

Comet Holmes is certainly one of the most memorable comets of recent times, not so much for its spectacular tail, but for its odd behavior; Hubble observed it several times Finally, Hubble’s View of Comet Holmes is the Universe Today story on this.
CHXR 73 (Credit: NASA, ESA, K. Luhman (Pennsylvania State University))

One of the most difficult challenges astronomers face, in doing science, is understanding and accounting for biases. For example, how could you tell, just by examining the approximately 6,000 stars you can see with your unaided vision, that none of them are examples of the most common kind of star! The nearest, brightest red dwarfs are far too faint to see without a telescope (do you know what their names are?), and it’s no easy matter to even find these stars. And what about stars that are fainter still, stars that aren’t quite stars, brown dwarfs? The first, certain, brown dwarf was not discovered until 1995, but since then our understanding of them has improved dramatically, and Hubble’s ACS has helped greatly in that understanding (see the Universe Today article on CHXR 73: Giant Planet or Failed Star?).
Supernova remnant Cas A (Credit: NASA, ESA, Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration) Click for zoomable image

Cassiopeia A, or Cas A, is undoubtedly a supernova remnant. And it also results from a rather recent supernova; but which? There’s some uncertainty, but it seems it was seen, by the astronomer Flamsteed, in 1680. The ACS image above is the most detailed optical images of Cas A; Hubble’s View of Supernova Remnant Cassiopeia A.
Einstein double ring (Credit: NASA, ESA, R. Gavazzi, T. Treu (UCLA, Santa Barbara), SLACS team)

With a galaxy (or cluster) positioned just so in front of a more distant galaxy (or quasar), gravitational lensing will produce an Einstein ring (or a partial ring). Several such rings had been observed prior to 2008, but the one ACS snapped – of SDSSJ0946+1006 – turned out to be a double; three galaxies lined up one behind the other (the right hand image is a highly processed version of the left hand one, with the light of the massive, foreground elliptical galaxy removed). Hubble Sees a Double Einstein Ring.

Tomorrow: 2008 and 2009

Previous articles:
Hubble Turns Sixteen, and Just Keeps on Working
Hubble Enters its Teen Years, More Powerful, More Ambitious
Hubble’s 20th: At Least as Good as Any Human Photographer
Hubble’s 10th Birthday Gift: Measurement of the Hubble Constant
Hubble at 8: So Many Discoveries, So Quickly
Hubble’s 20 Years: Now We Are Six
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today

Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System

Hubble Turns Sixteen, and Just Keeps on Working

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Note: To celebrate the 20th anniversary of the Hubble Space Telescope, for ten days, Universe Today will feature highlights from two year slices of the life of the Hubble, focusing on its achievements as an astronomical observatory. Today’s article looks at the period April 2004 to April 2006.

First, in 1995, there was the Hubble Deep Field (HDF). Then, in 1998, the Hubble Deep Field South (HDF-S). With the new Advanced Camera for Surveys (ACS) aboard, and the Near Infrared Camera and Multi-object Spectrometer (NICMOS) continuing to work well, the Hubble took a new, even deeper, image. And what was it called? Why, the Hubble Ultra-Deep Field (HUDF) of course! The total exposure was approximately a million seconds, and the observations were made in late 2003 and early 2004 (Earliest Star Forming Galaxies Found is Universe Today’s first story on it). Hundreds of scientific papers have been published using data from these observations (and others; a lot of time on major ground-based telescopes has also been devoted to these fields).

In its more than a decade of operation, the Hubble’s main astronomical instruments worked well. Sure, they needed various repairs and were upgraded in one way or another during the four servicing missions to date (remember that 3 was split into two, 3A and 3B), but none failed completely. Well, in August 2004 STIS (the Space Telescope Imaging Spectrograph) did.This intensified the gloom created earlier in the year when NASA Director announced that there would be no more Space Shuttle missions to the Hubble, and his announcements about possible robotic missions left space and astronomy fans cold.

In April 2006, Hubble turned 16; would you have chosen M82 as a ‘sweet sixteen’ snap to put in your album? Universe Today did!

M82 (Credit: NASA, ESA and the Hubble Heritage TeamSTScI/AURA). Acknowledgment: J. Gallagher (University of Wisconsin), M. Mountain (STScI), P. Puxley (NSF)) Click for a zoomable image


GOODS (South; Credit: GOODS team)

One of the biggest challenges in astronomy today is working out how galaxies formed and evolved. In turn this involves understanding the role of star formation (and its rates), how supermassive black holes accrete matter and create jets, and how dark matter structures form. One powerful way to get at least some answers to the many questions is to point the world’s most powerful telescopes at the same, small, patch of sky for a very long time. Choosing the patch of sky to stare at isn’t easy; for example, ideally you want a ‘hole’ in the Milky Way’s hydrogen, to let you see as clearly as possible in the soft x-ray part of the electromagnetic spectrum. The GOODS team, comprising dozens of astronomers from many institutions, chose two fields, one in the north (centered on the Hubble Deep Field) and one in the south (centered on the Chandra Deep Field-South). The image above gives an idea of what one project involved; the red dots are objects whose spectra were taken (by a spectrograph called VIMOS, on one of the European Southern Observatory’s Very Large Telescopes), overlaid on an image from a ground-based telescope; the contours are the Chandra 2Ms (yes, that’s 2 million seconds) region, and the Hubble ACS GOODS-S field. Over 400 GOODS papers have been published so far, with all sorts of interesting results established. For more information, visit the STScI GOODS website and the ESO one; to get you started, “The Great Observatories Origins Deep Survey: Initial Results from Optical and Near-Infrared Imaging“.
ESA/ESO/NASA Photoshop FITS Liberator screenshot

I mentioned earlier – Hubble’s 20th: At Least as Good as Any Human Photographer – that astronomers have their own file format, called FITS, for astronomical data, whether images, spectra, or whatever. Well, FITS is not exactly user friendly (unless you’re an astronomer), so to make the data more accessible, a joint team from the European Space Agency, the European Southern Observatory, and NASA produced the ESA/ESO/NASA Photoshop FITS Liberator, a free plug-in. Why not give it a try?
Aurorae on Saturn (Credit: NASA, ESA, J. Clarke (Boston University, USA), Z. Levay (STScI)) Click for a zoomable image

Even though various space probes visit various planets (and their moons), and undertake intensive research of them, good science is still done from afar. Hubble’s studies of Saturn’s aurorae are a good example (Universe Today’s coverage here).
Crab Nebula (Credit:NASA, ESA and Allison Loll/Jeff Hester (Arizona State University). Acknowledgement: Davide De Martin (ESA/Hubble)) Click for a zoomable image

Hubble had taken many images of the Crab Nebula before (see Hubble at 8: So Many Discoveries, So Quickly for example), but the above was a first, in many ways. It was taken by WFPC2, and is actually 24 separate images; it is the highest resolution image of the Crab, to date (Giant Hubble Mosaic of the Crab Nebula is the Universe Today title).
Orion Nebula (Credit: NASA, ESA, M. Robberto ( Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team) Click for a zoomable image

The Orion nebula is the closest ‘star factory’, so receives intense scrutiny by astronomers. Hubble pointed all its imaging instruments at it, in 2005, for over 100 orbits. This image is an ACS mosaic (do you know what the other imaging instruments were, then? Best Orion Nebula Image Ever Taken has the answer).
SDSS J1004+4112 as gravitational lens (Credit: European Space Agency, NASA, Keren Sharon (Tel-Aviv University) and Eran Ofek (CalTech)) Click for a zoomable image

The theory of general relativity predicts gravitational lensing, and this prediction was confirmed in 1919 (do you know how?). When a point source, such as a quasar, is lensed by a foreground object such as a galaxy cluster, the resulting image will have quite specific properties; for example, only an odd number of images, but one image is usually very weak and embedded deep within the light of the lensing object itself. Four images produced by SDSS J1004+4112 (the foreground cluster) had been detected before, but Hubble found the fifth (the blue circles are the quasar, the red a lensed galaxy, the yellow a supernova). Hubble’s Best Gravitational Lens is the Universe Today article on this discovery.

Tomorrow: 2006 and 2007.

Previous articles:

Hubble Enters its Teen Years, More Powerful, More Ambitious
Hubble’s 20th: At Least as Good as Any Human Photographer
Hubble’s 10th Birthday Gift: Measurement of the Hubble Constant
Hubble at 8: So Many Discoveries, So Quickly
Hubble’s 20 Years: Now We Are Six
Hubble’s 20 Years: Time for 20/20 Vision
Hubble: It Was Twenty Years Ago Today

Sources: HubbleSite, European Homepage for the NASA/ESA Hubble Space Telescope, The SAO/NASA Astrophysics Data System