Hubble view of the huge star formation region N11 in the Large Magellanic Cloud. Credit: NASA, ESA and Jesús Maíz Apellániz (Instituto de Astrofísica de Andalucía, Spain).
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Within the Large Magellenic Cloud is one of the most active star forming regions in our nearby Universe. This new Hubble image highlights N11 – also known as the Bean Nebula — a beautiful region of energetic star formation. The billowing pink clouds that look like cotton candy and bright bubbles of glowing gasses and are telltale signs that stars are being created. Click the image for a larger, hi-res version.
Beans, bubbles and candy aren’t the only terrestrial shapes to be found in this spectacular image from the Hubble Space Telescope.
If you zoom into upper left (click this link for a zoom video) you’ll find a rose: The Rose Nebula LHA 120-N 11A. Its rose-like petals of gas and dust are illuminated from within, thanks to the radiation from the massive hot stars at its centre. N11A is relatively compact and dense and is the site of the most recent burst of star development in the region.
If you live in the southern hemisphere, both the Large Magellanic Cloud and its small companion, the Small Magellanic Cloud, are easily seen with the unaided eye. That’s a sight I would someday love to see!
Detailed observations made by the NASA/ESA Hubble Space Telescope have led researchers to believe that the flash of light seen on Jupiter on 3 June was a meteor. Credit: NASA, ESA, M. H. Wong (University of California, Berkeley, USA), H. B. Hammel (Space Science Institute, Boulder, Colorado, USA), A. A. Simon-Miller (Goddard Space Flight Center, Greenbelt, Maryland, USA) and the Jupiter Impact Science Team.
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Jupiter has a few mysteries these days. Between an equatorial belt that has gone missing and an impact that didn’t leave a mark, astronomers decided they needed to put the Hubble Space Telescope on the case. New and detailed observations from the venerable space telescope have provided some insights into these two recent puzzling events.
At 22:31 (CEST) on June 3, 2010 Australian amateur astronomer Anthony Wesley saw a two-second-long flash of light on the disc of Jupiter, captured from a live video feed from his telescope. In the Philippines, amateur astronomer Chris Go confirmed that he had simultaneously recorded the transitory event on video. Wesley was also the discoverer of the now world-famous July 2009 impact.
Astronomers around the world suspected that something significant must have hit the giant planet to unleash a flash of energy bright enough to be seen here on Earth, about 770 million kilometers away. But they didn’t know how just how big it was or how deeply it had penetrated into the atmosphere. Over the past two weeks there have been ongoing searches for the “black-eye” pattern of a deep direct hit like those left by former impactors.
Astronomers turned Hubble’s Wide Field Camera 3 aboard the NASA/ESA Hubble Space Telescope on June 7, and found no sign of debris above Jupiter’s cloud tops. This means that the object didn’t descend beneath the clouds and explode as a fireball. If it had, then dark sooty blast debris would have been ejected and would have rained down onto the clouds.
Instead the flash is thought to have come from a giant meteor burning up high above Jupiter’s cloud tops, which did not plunge deep enough into the atmosphere to explode and leave behind any telltale cloud of debris, as seen in previous Jupiter collisions.
“The cloud tops and the impact site would have appeared dark in the ultraviolet and visible images due to debris from an explosion,” said team member Heidi Hammel of the Space Science Institute in Boulder, Colorado. “We can see no feature that has those distinguishing characteristics in the known vicinity of the impact, suggesting there was no major explosion and no ‘fireball’.”
Dark smudges marred Jupiter’s atmosphere when a series of fragments of Comet Shoemaker-Levy 9 hit Jupiter in July 1994, and a similar dark area formed in July 2009 when a suspected asteroid slammed into Jupiter. The latest intruder is estimated to be only a fraction of the size of these previous impactors and is thought to have been a meteor.
So, Wesley and Go were fortunate to have spotted the flash.
“Observations of these impacts provide a window on the past — onto the processes that shaped our Solar System in its early history,” said team member Leigh Fletcher of the University of Oxford, UK. “Comparing the two collisions — from 2009 and 2010 — will hopefully yield insights into the types of impact processes in the outer Solar System, and the physical and chemical response of Jupiter’s atmosphere to these amazing events.” These Hubble images of Jupiter taken 11 months apart show the Southern Equatorial Belt has disappeared. Credit: NASA, ESA, M. H. Wong (University of California, Berkeley, USA), H. B. Hammel (Space Science Institute, Boulder, Colorado, USA), A. A. Simon-Miller (Goddard Space Flight Center, Greenbelt, Maryland, USA) and the Jupiter Impact Science Team.
Since Hubble was now trained on Jupiter, astronomers used the opportunity to get a close-up look at changes in Jupiter’s atmosphere following the disappearance of the dark cloud feature known as the Southern Equatorial Belt several months ago.
In the Hubble view, a slightly higher altitude layer of white ammonia ice crystal clouds appears to obscure the deeper, darker belt clouds. “Weather forecast for Jupiter’s Southern Equatorial Belt: cloudy with a chance of ammonia,” Hammel said.
The team predicts that these ammonia clouds should clear out in a few months, as they have done in the past. The clearing of the ammonia cloud layer should begin with a number of dark spots like those seen by Hubble along the boundary of the south tropical zone.
“The Hubble images tell us these spots are holes resulting from localized downdrafts. We often see these types of holes when a change is about to occur,” said Amy Simon-Miller from Goddard Space Flight Center. .
“The Southern Equatorial Belt last faded in the early 1970s. We haven’t been able to study this phenomenon at this level of detail before,” Simon-Miller added. “The changes of the last few years are adding to an extraordinary database on dramatic cloud changes on Jupiter.”
If you think about it, spacecraft are kind of ethereal in that once they are launched into space, we don’t ever see them again. Australian artist Peter Hennessey has created life-size wooden sculptures of several different spacecraft, giving people the chance to see and touch these objects that are immediately recognizable but which we will never actually experience. Hennessey says he wanted to “reverse the virtualization of physical things” by creating life-size reproductions of the spacecraft such as the Voyager space probe, Apollo Lunar Rover, the Hubble Space Telescope, and more. From Hennessey’s website: “By ‘re-enacting’ space traveling, scientific and military objects in plywood, galvanized steel and canvas, the artist creates ‘stand-ins’ that allow the viewer to contemplate their physical, symbolic and historical resonances as well as the political processes that they represent.”
I just think they are really cool, and I’d love to see them – Hubble has to be huge! See below.
'My Hubble (the universe turned in on itself)' by artist Peter Hennessey.
“My Hubble (the universe turned in on itself) is now on display in Sydney Australia as part of “Biennale of sydney 2010.” This life size ‘re-enactment’ of the Hubble Space Telescope was constructed “with the aim of giving the viewer a physical experience of the object.” It is constructed from lasercut plywood and steel and simultaneously enacts the scale and detail
of the original. This is an interactive sculpture: visitors are encouraged to play with, modify and create their own mini universes on the ground, which are then reflected by the telescope into the heavens.
According to the Design Bloom website, when creating his work Hennessey looked at 7 different images of the Hubble, and rather than using 3D software to model individual parts as one might expect, he used adobe illustrator. Building the telescope took about 3 months – in which 6 weeks were dedicated to laser cutting individual parts and building them into sections and the rest of the time was dedicated to assembling it.
'My Lunar Rover' by artist Peter Hennessey.
With ‘My Moon Landing’ Hennessey’s wanted to explore the “physicality, presences and symbolic power of the inaccessible objects that derive from the space race.”
These NASA Hubble Space Telescope snapshots reveal an impact scar on Jupiter fading from view over several months between July 2009 and November 2009. Credit: NASA, ESA, M. H. Wong (University of California, Berkeley), H. B. Hammel (Space Science Institute, Boulder, Colo.), I. de Pater (University of California, Berkeley), and the Jupiter Impact Team
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When amateur astronomer Anthony Wesley from Australia saw a dark spot the size of the Pacific Ocean appear on Jupiter through his telescope on July 19, 2009, this started a flurry of astronomic activity, with other telescopes quickly slewing to take a look. It didn’t take long for other astronomers to confirm Jupiter had been hit by an object, either an asteroid or a comet. Of course, the world’s most famous telescope, Hubble, zeroed in on this unexpected activity on Jupiter, and luckily, the telescope had been recently updated with a new Wide Field Camera 3 and newly repaired Advanced Camera for Surveys. Astronomers have now released a series of images from Hubble which may show for the first time the immediate aftermath of an asteroid striking another planet.
Astronomers have witnessed this kind of cosmic event before, but from a comet. Similar scars had been left behind during the course of a week in July 1994, when more than 20 pieces of Comet P/Shoemaker-Levy 9 (SL9) plunged into Jupiter’s atmosphere. The 2009 impact occurred during the same week, 15 years later.
But comparing Hubble images of both collisions, astronomers say the culprit was likely an asteroid about 1,600 feet (500 meters) wide.
“This solitary event caught us by surprise, and we can only see the aftermath of the impact, but fortunately we do have the 1994 Hubble observations that captured the full range of impact phenomena, including the nature of the objects from pre-impact observations” says astronomer Heidi Hammel of the Space Science Institute in Boulder, Colo., leader of the Jupiter impact study.
The analysis revealed key differences between the two collisions (in 1994 and 2009), providing clues to the 2009 event. Astronomers saw a distinct halo around the 1994 impact sites in Hubble ultraviolet (UV) images, evidence of fine dust arising from a comet-fragment strike. The UV images also showed a strong contrast between impact-generated debris and Jupiter’s clouds.
Hubble ultraviolet images of the 2009 impact showed no halo and also revealed that the site’s contrast faded rapidly. Both clues suggest a lack of lightweight particles, providing circumstantial evidence for an impact by a solid asteroid rather than a dusty comet.
The elongated shape of the recent asteroid impact site also differs from the 1994 strike, indicating that the 2009 object descended from a shallower angle than the SL9 fragments. The 2009 body also came from a different direction than the SL9 pieces.
Team member Agustin Sanchez-Lavega of the University of the Basque Country in Bilbao, Spain, and colleagues performed an analysis of possible orbits that the 2009 impacting body could have taken to collide with Jupiter. Their work indicates the object probably came from the Hilda family of bodies, a secondary asteroid belt consisting of more than 1,100 asteroids orbiting near Jupiter.
The 2009 strike was equal to a few thousand standard nuclear bombs exploding, comparable to the blasts from the medium-sized fragments of SL9. The largest of those fragments created explosions that were many times more powerful than the world’s entire nuclear arsenal blowing up at once.
The recent impact underscores the important work performed by amateur astronomers. “This event beautifully illustrates how amateur and professional astronomers can work together,” said Hammel.
The Jupiter bombardments reveal that the solar system is a rambunctious place, where unpredictable events may occur more frequently than first thought. Jupiter impacts were expected to occur every few hundred to few thousand years. Although there are surveys to catalogue asteroids, many small bodies may still go unnoticed and show up anytime to wreak havoc.
The study by Hammel’s team appeared in the June 1 issue of The Astrophysical Journal Letters.
NGC 3603 and its massive compact central star cluster was taken with the Advanced Camera for Surveys (ACS) on the NASA/ESA Hubble Space Telescope. The region that was studied in detail to detect the motion of stars within the cluster is shown as a box. Credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration
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Using the Hubble Space Telescope, astronomers from the Max Planck Institute for Astronomy made two observations ten years apart of the giant nebula NGC 3603 and found a surprising amount of movement and unrest in one of the most massive young star clusters in the Milky Way. The comparison images reveal several hundred stars continued to move for about 1 million years after the star cluster’s formation, with stellar motion not having “settled down” as expected. This new finding is at odds with current models of how such clusters evolve, and may force astronomers to rethink how star clusters form and develop.
While ordinary star clusters disperse over time as the different stars go their own separate ways, it was thought that very massive and compact clusters were different, and that they formed massive aggregations of stars known as globular clusters, whose tightly-packed stars remain gravitationally bound to each other for billions of years.
Conventional thinking was that stars with lower mass should move faster, and those with higher mass should move more slowly. But a team led by Wolfgang Brander, making high precision observations, found the stars in NGC 3603 are still moving at rates that are independent of their mass.
They found that all of the stars move at about the same average speed of 4.5 km/s (corresponding to a change in apparent position of a mere 140 micro-arc seconds per year). The average speed does not appear to vary with mass at all.
The team observed more than 800 stars and were able to obtain sufficiently precise speed measurements for 234 cluster stars of different masses and surface temperatures. Partial view of the giant nebula (HII region) NGC 3603 with its central, 1 million year old compact starburst cluster. False-color image based on observations with the Wide Field/Planetary Camera 2 of the Hubble Space Telescope. The dominant green color signalizes light emitted as ionized hydrogen regains its missing electron ('recombination line H-alpha'). The field of view is about 160 arc seconds on each side. The image shape is due to the detector placement of the Wide Field/Planetary Camera. Credit: NASA/ESA/Wolfgang Brandner (MPIA), Boyke Rochau (MPIA) and Andrea Stolte (University of Cologne)
“Once our analysis was completed, we reached a precision of 27 millionths of an arc second per year,” said Boyke Rochau, the paper’s lead author. “Imagine you are in Bremen, observing an object that is located in Vienna. Now the object moves sideways by the breadth of a human hair. That’s a change in apparent position of about 27 millionths of an arc second.”
Apparently – and surprisingly – this very massive star cluster has not yet settled down. Instead, the stars’ velocities still reflect conditions from the time the cluster was formed, approximately one million years ago.
“For the first time, we have been able to measure precise stellar motions in such a compact young star cluster. This is key information for astronomers trying to understand how such clusters are formed, and how they evolve,” said team member Andrea Stolte from the University of Cologne.
Vexingly, the question of whether or not the massive young cluster in NGC 3603 will become a globular cluster remains open. Given the new results, it all depends on the speeds of the low-mass stars, which were too faint to allow for precise speed measurements with the Hubble Space Telescope. “To find out whether or not our star cluster will disperse, we will need to wait for the next generation of telescopes, such as the James Webb Space Telescope (JWST) or ESO’s European Extremely Large Telescope (E-ELT),” said Brandner.
The results have been published in the Letters section of the Astrophysical Journal. Read the paper here.
Epsilon Andromedae. Illustration Credit: NASA, ESA, and A. Feild (STScI) Science Credit: NASA, ESA, and B. McArthur, University of Texas at Austin, McDonald Observatory.
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Astronomers are finding that not only are there a wide range of different extrasolar planets, but there are different types of planetary systems, as well. “We’re not in Kansas anymore as far as solar systems go,” said Barbara McDonald from the University of Texas’ McDonald Observatory, at the American Astronomical Society meeting in Miami, Florida today. “The exciting thing is, we found another multi-planet system that is not at all like our own.”
A close look at the Upsilon Andromedae system with the Hubble Space Telescope, the Hobby-Eberly Telescope and other ground-based telescopes shows a whacky system where planets are out of tilt and have highly inclined orbits. The astronomers also found another planet, and also another star – this is likely a binary star system.
Even with Pluto’s inclined orbit, our solar system looks like an ocean of calm compared to Upsilon Andromedae. Comparison of solar systems. Credit: HubbleSite
McDonald said these surprising findings will impact theories of how multi-planet systems evolve, and it shows that some violent events can happen to disrupt planets’ orbits after a planetary system forms.
“The findings mean that future studies of exoplanetary systems will be more complicated,” she said. “Astronomers can no longer assume all planets orbit their parent star in a single plane.” says Barbara McArthur of The University of Texas at Austin’s McDonald Observatory.
Similar to our Sun in its properties, Upsilon Andromedae lies about 44 light-years away. It’s a little younger, more massive, and brighter than the Sun. For just over a decade, astronomers have known that three Jupiter-type planets orbit the yellow-white star Upsilon Andromedae.
But after over a thousand combined observations, McDonald and her team uncovered hints that a fourth planet, e, orbits the star much farther out. They were also able to determine the exact masses of two of the three previously known planets, Upsilon Andromedae c and d. Much more startling, though, is that not all planets orbit this star in the same plane. The orbits of planets c and d are inclined by 30 degrees with respect to each other. This research marks the first time that the “mutual inclination” of two planets orbiting another star has been measured.
“Most probably Upsilon Andromedae had the same formation process as our own solar system, although there could have been differences in the late formation that seeded this divergent evolution,” McArthur said. “The premise of planetary evolution so far has been that planetary systems form in the disk and remain relatively co-planar, like our own system, but now we have measured a significant angle between these planets that indicates this isn’t always the case.”
Until now the conventional wisdom has been that a big cloud of gas collapses down to form a star, and planets are a natural byproduct of leftover material that forms a disk. In our solar system, there’s a fossil of that creation event because all of the eight major planets orbit in nearly the same plane. The outermost dwarf planets like Pluto are in inclined orbits, but these have been modified by Neptune’s gravity and are not embedded deep inside the Sun’s gravitational field.
So what knocked the Upsilon Andromedae system around?
“Possibilities include interactions occurring from the inward migration of planets, the ejection of other planets from the system through planet-planet scattering, or disruption from the parent star’s binary companion star, Upsilon Andromedae B,” McArthur said.
Or, the companion star – a red dwarf less massive and much dimmer than the Sun — could be the culprit. is.
“We don’t have any idea what its orbit is,” said team member Fritz Benedict. “It could be very eccentric. Maybe it comes in very close every once in a while. It may take 10,000 years.” Such a close pass by the secondary star could gravitationally perturb the orbits of the planets.”
The two different types of data combined in this research were astrometry from the Hubble Space Telescope and radial velocity from ground-based telescopes.
Astrometry is the measurement of the positions and motions of celestial bodies. McArthur’s group used one of the Fine Guidance Sensors (FGSs) on the Hubble telescope for the task. The FGSs are so precise that they can measure the width of a quarter in Denver from the vantage point of Miami. It was this precision that was used to trace the star’s motion on the sky caused by its surrounding — and unseen — planets.
Radial velocity makes measurements of the star’s motion on the sky toward and away from Earth. These measurements were made over a period of 14 years using ground-based telescopes, including two at McDonald Observatory and others at Lick, Haute-Provence, and Whipple Observatories. The radial velocity provides a long baseline of foundation observations, which enabled the shorter duration, but more precise and complete, Hubble observations to better define the orbital motions.
The fact that the team determined the orbital inclinations of planets c and d allowed them to calculate the exact masses of the two planets. The new information told us that our view as to which planet is heavier has to be changed. Previous minimum masses for the planets given by radial velocity studies put the minimum mass for planet c at 2 Jupiters and for planet d at 4 Jupiters. The new, exact masses, found by astrometry are 14 Jupiters for planet c and 10 Jupiters for planet d.
“The Hubble data show that radial velocity isn’t the whole story,” Benedict said. “The fact that the planets actually flipped in mass was really cute.”
The fourth planet is so far out, that its signal does not reveal the curvature of its orbit.
The 14 years of radial velocity information compiled by the team uncovered hints that a fourth, long-period planet may orbit beyond the three now known. There are only hints about that planet because it’s so far out that the signal it creates does not yet reveal the curvature of an orbit. Another missing piece of the puzzle is the inclination of the innermost planet, b, which would require precision astrometry 1,000 times greater than Hubble’s, a goal attainable by a future space mission optimized for interferometry.
Artist's concept of the exoplanet WASP-12b -- a hot Jupiter being devoured by its parent star. Artwork Credit: NASA, ESA, and G. Bacon (STScI)
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We all like a hot meal, but this is really bizarre. Back in February, Jean wrote an article about WASP-12b, the hottest known planet in the Milky Way that is being ripped to shreds by its parent star. Shu-lin Li of the Department of Astronomy at the Peking University, Beijing, predicted that the star’s gravity would distort the planet’s surface and make the interior of the planet so hot that the atmosphere would expand out and co-mingle with the star. Shu-lin calculated the planet would one day be completely consumed. Now the Hubble Space Telescope has confirmed this prediction, and astronomers estimate the planet may only have another 10 million years left before it is completely devoured.
Using the Cosmic Origins Spectrograph (COS), and its sensitive ultraviolet instruments, astronomers saw that the star and the planet’s atmosphere share elements, passing them back and forth. “We see a huge cloud of material around the planet, which is escaping and will be captured by the star. We have identified chemical elements never before seen on planets outside our own solar system,” says team leader Carole Haswell of The Open University in Great Britain.
This effect of matter exchange between two stellar objects is commonly seen in close binary star systems, but this is the first time it has been seen so clearly for a planet.
The planet, called WASP-12b, is so close to its sunlike star that it completes an orbit in 1.1 days, and is heated to nearly 1,540 C (2,800 F) and stretched into a football shape by enormous tidal forces. The atmosphere has ballooned to nearly three times Jupiter’s radius and is spilling material onto the star. The planet is 40 percent more massive than Jupiter.
WASP-12 is a yellow dwarf star located approximately 600 light-years away in the winter constellation Auriga.
Haswell and her science team’s results were published in the May 10, 2010 issue of The Astrophysical Journal Letters.
30 Dor #016. Illustration Credit: NASA, ESA, and Z. Levay (STScI) Science Credit: NASA, ESA, C. Evans (Royal Observatory Edinburgh), N. Walborn (STScI), and ESO
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In an astronomical version of “Biggest Loser” meets “Survivor,” a heavy weight star has been kicked out of its stellar nursery. This huge runaway star is rushing away from its birthplace at more than 402,336 kilometers per hour (250,000 miles an hour), and it likely was ejected by a group of even larger sibling stars. The future outlook for this tough-luck star seemingly doesn’t improve: Paul Crowther of the University of Sheffield, a member of the team who made the observations of 30 Dor #016, said the wayward star will continue to streak across space and will eventually end its life in a titanic supernova explosion, likely leaving behind a remnant black hole. There’s a new reality series in there somewhere!
The star on the run is found 375 light-years from its suspected home, a giant star cluster called R136 in 30 Doradus, also called the Tarantula Nebula, about roughly 170,000 light-years from Earth. R136 contains several stars topping 100 solar masses each. 30 Dor #016 is 90 times more massive than our Sun.
Astronomers say runaway stars can be made in a couple of ways: a star may encounter one or two heavier siblings in a massive, dense cluster and get booted out through a stellar game of pinball. Or, a star may get a ‘kick’ from a supernova explosion in a binary system, with the more massive star exploding first.
“It is generally accepted, however, that R136 is sufficiently young, 1 million to 2 million years old, that the cluster’s most massive stars have not yet exploded as supernovae,” says COS team member Danny Lennon of the Space Telescope Science Institute. “This implies that the star must have been ejected through dynamical interaction.” 30 Dor with 30 Dor #16 in the inset. Image credits: : NASA, ESA, J. Walsh (ST-ECF), and ESO
The renegade star may not be the only runaway in the region. Two other extremely hot, massive stars have been spotted beyond the edges of 30 Doradus. Astronomers suspect that these stars, too, may have been ejected from their home. They plan to analyze the stars in detail to determine whether 30 Doradus might be unleashing a barrage of massive stellar runaways into the surrounding neighborhood.
The observations came from a team-effort using Hubble’s newly installed Cosmic Origins Spectrograph (COS) to take an image of the region in 2009, an optical image of the star taken by the Wide Field Planetary Camera 2 in 1995, and another spectroscopic study from the European Southern Observatory’s Very Large Telescope (VLT) at the Paranal Observatory. It was first observed in 2006 when a team led by Ian Howarth of University College London spotted it with the Anglo-Australian Telescope at Siding Spring Observatory.
COS’s ultraviolet spectroscopic observations showed that the wayward star is unleashing a fury of charged particles in one of the most powerful stellar winds known, a clear sign that it is extremely massive, perhaps as much as 90 times heavier than the Sun. The star, therefore, also must be very young, about 1 million to 2 million years old, because extremely massive stars live only a few million years.
The VLT observations revealed that the star’s velocity is constant and not a result of orbital motion in a binary system. Its velocity corresponds to an unusual motion relative to the star’s surroundings, evidence that it is a runaway star.
The study also confirmed that the light from the runaway is from a single massive star rather than the combined light of two lower-mass stars. In addition, the observation established that the star is about 10 times hotter than the Sun, a temperature that is consistent with a high-mass object.
“These results are of great interest because such dynamical processes in very dense, massive clusters have been predicted theoretically for some time, but this is the first direct observation of the process in such a region,” says Nolan Walborn of the Space Telescope Science Institute in Baltimore and a member of the COS team that observed the misfit star. “Less massive runaway stars from the much smaller Orion Nebula Cluster were first found over half a century ago, but this is the first potential confirmation of more recent predictions applying to the most massive young clusters.”
The research team, led by Chris Evans of the Royal Observatory Edinburgh, published the study’s results May 5 in the online edition of The Astrophysical Journal Letters.
The Hubble Space Telescope is one of the greatest technological achievements in our history, and for two decades has astonished us with dynamic images of our solar system and the world beyond. To celebrate this important twenty-year milestone, NASA looks back at the contributions of this extraordinary scientific tool, and the scientists who created it, in a documentary entitled “Hubble: Twenty Years of Discovery.” The movie is narrated by Brent Spiner, Data from Star Trek.
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).
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)
