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 1992 to April 1994.
“And we have liftoff, liftoff of the Space Shuttle Endeavor, on an ambitious mission to service the Hubble Space Telescope”
Without a doubt, Servicing Mission 1 in early December 1993 was the high point of the Hubble Space Telescope’s third and fourth years in space.
For starters, it successfully replaced the high speed photometer instrument with COSTAR (Corrective Optics Space Telescope Axial Replacement), which, as its name implies, corrected for the mis-figured primary mirror and so permitted the three instruments not replaced to make the high quality images intended (they were the Faint Object Camera, the Faint Object Spectrograph, and the Goddard High Resolution Spectrograph).
It also replaced the WF/PC (Wide Field Planetary Camera) with an upgraded WF/PC (called WFPC2), and made several other repairs and replacements which considerably improved the Hubble’s performance and robustness.
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John Bahcall
Well before the Hubble was launched much of its observing time was pre-allocated, especially to two Hubble Key Projects, “on the Extragalactic Distance Scale”, and the “Quasar Absorption Line” Key Project. The former is well-known (and I’ll cover it in a later Hubble 20th birthday article); the latter hardly known at all outside the astrophysics community. It was the brainchild of the remarkable John Bahcall, and much of the Hubble’s time in its first four years was devoted to it. There are 13 main papers on its results, with hundreds more based on them. In a word, this project revolutionized our understanding of the space between galaxies and galaxy clusters, all the way from just beyond the Milky Way to billions of light-years distant. The lucky 16 amateurs (Credit: NASA/STScI)
It wasn’t only professional astronomers who used the Hubble in these two years; 16 amateurs did too! Do you know what they found? If you had the chance, what would you use the Hubble to observe? Comet Shoemaker-Levy 9 (Credit: Dr H.A. Weaver, T.E. Smith; STScI/NASA)
Perhaps the most captivating images the Hubble took in these two years are the ones of Comet Shoemaker-Levy 9 on its way to a collision with Jupiter (I’ll cover the collision itself tomorrow). Do you remember, back then, that asteroid and comet threats to life on Earth just became a whole lot more believable? eta Carinae (Credit: J.Hester/Arizona State University/NASA)
3C273's jet (Credit: R.C. Thomson&C.D. Mackay, IoA, Cambridge, UK; A.E. Wright, ATNF)
Hubble sent back images of many more objects in these two years, including a much better one of eta Carinae (compare this one with the one in yesterday’s article) and the optical jet of the iconic quasar 3C273.
The date was 24 April, 1990; “Liftoff of the Space Shuttle Discovery, with the Hubble Space Telescope, our window on the universe”.
Over the next ten days I’ll be reviewing these twenty years, starting with the first two today; I hope you will enjoy the show.
Of course, the Hubble’s history goes back many years before 1990; astrophysicist Lyman Spitzer is credited with the first paper proposing a space-based optical observatory, in 1946! He spent a good half century working on the idea (Trivia fact: Spitzer really knew his plasma physics; among other things he founded the Princeton Plasma Physics Laboratory, in 1951; the PPPL is home to some exciting magnetic reconnection experiments). Not so well-known, in the US at least, is that European involvement in the Hubble – via the European Space Agency (ESA) – dates from 1975, 15 years before its launch (Trivia fact: ESA’s Space Telescope European Coordinating Facility (ST-ECF) issued its first newsletter in March 1985). HST WF/PC first light image (Credit: NASA/ESA/STScI)
For all the brilliant engineering, the best money could buy, the Hubble’s primary mirror was ground to exquisite precision and accuracy … but precisely and accurately wrong; the “presence of significant spherical aberration” was announced by NASA at the end of June, 1990. (Trivia fact: the cause of the mis-grinding was a field lens in the reflective null corrector used to test the figure of the primary mirror; it was “mis-located by about 1.3mm” Did heads roll as a result?)
However, because the primary mirror was ground so precisely and accurately, if wrongly, images sent back from the Hubble could be processed to largely remove the unintended blur, and so after a half year or so of rather intense work, the scientific show did go on. Supernova 1987A (Credit: NASA, ESA, STScI)
And what a show it was! Saturn's North Polar Hood (Credit: NASA, ESA, STScI)
Take a trip down memory lane, check out Hubble’s image of Saturn’s North Polar Hood; it’s zoomable!
But a faulty mirror and image processing are not quite the real thing; sometimes there are image processing artifacts, as this 1991 image of a nearby supernova-to-be shows: Eta Carinae (Credit: NASA, ESA)
Of course it wasn’t only pretty pictures that the Hubble returned to Earth; a great many papers based on the astronomical data from the Hubble were published in its first two years of operation, covering a wide range of topics (perhaps I’ll base a future Universe Puzzle on this, maybe ‘what was the first such paper?’). And it wasn’t only images; the Hubble carried an instrument called the Faint Object Spectrograph, which worked in a part of the electromagnetic spectrum accessible only from space, the far ultraviolet (click on this link to read about limits on He I emission, the He I Gunn-Peterson effect, and Ly-alpha absorption spectrum “at z roughly 0.5”).
What’s your favorite from the first two years? 3C 273, 2003 HST image (Credit: NASA/J.Bahcall(IAS))
Mine’s The Ultraviolet Absorption Spectrum of 3C 273; not only is about the iconic quasar 3C 273, not only is it a classic John Bahcall paper (he writes so well!), not only does it illustrate well the scientific power of spectroscopy, but shines a light on composition of the intracluster medium.
Tomorrow: 1992 and 1993, including COSTAR and the first servicing mission.
M 66. Image credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgement: Davide De Martin and Robert Gendler
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This isn’t your basic spiral galaxy, but perhaps it used to be! Hubble’s Advanced Camera for Surveys has captured this beautiful view of the biggest child of the Leo Triplet, M66. Its asymmetric spiral arms and an apparently displaced core was mostly likely caused by the gravitational pull of the other two members of the trio. Talk about sibling rivalry!
M66, is located at a distance of about 35 million light-years in the constellation of Leo. Together with Messier 65 and NGC 3628, Messier 66 is one third of the Leo Triplet, a trio of interacting spiral galaxies, part of the larger Messier 66 group. While M66 is the biggest — it is about 100,000 light-years across — the gravitational influence from the two neighboring galaxies have distorted the one orderly spiral arms, making them appear to rise above the central core.
The striking dust lanes and bright star clusters along the spiral arm — pictured in the blue and pinkish regions of the image — are key tools for astronomers since they are used as indicators of how the parent galaxies assembled over time.
Messier 66 boasts a remarkable record of supernovae explosions. The spiral galaxy has hosted three supernovae since 1989, the latest one occurring in 2009. A supernova is a stellar explosion that may momentarily outshine its entire host galaxy. It then fades away over a period lasting several weeks or months. During its very short life the supernova radiates as much energy as the Sun would radiate over a period of about 10 billion years.
The green "blob" is Hanny's Voorwerp. Credit: Dan Herbert, Peter Smith, Matt Jarvis, Galaxy Zoo Team, Isaac Newton Telescope
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The green “blob” is Hanny’s Voorwerp. Credit: Dan Herbert, Peter Smith, Matt Jarvis, Galaxy Zoo Team, Isaac Newton Telescope
A storybook astronomy mystery is now part of the most famous telescope in history. A team of astronomers secured time on the Hubble Space Telescope to observe Hanny’s Voorwerp, the unusual object found by Dutch teacher Hanny Van Arkel while she was scanning through images for the Galaxy Zoo project. Hubble will be trained on the Voorwerp during three separate observing sessions, the first of which occurred on April 4, 2010. “The WFC3 (Wide Field Camera 3) images were obtained (Sunday),” said Principal Investigator Bill Keel from the University of Alabama in an email to Universe Today “and I was able to pull the calibrated files over last night for a quick look. Combining pairs of offset images to reject cosmic rays optimally will take some further work, but we’re happy to start working with the data and see what emerges at each step.”
The Voorwerp (also known by the much less endearing name of SDSS J094103.80+344334.2) created a sensation among amateur, armchair and professional astronomers alike, almost immediately after Van Arkel saw the object in 2007 and posted a question on the Galaxy Zoo forum, asking “What is this?” All this took place just a month after the Galaxy Zoo project opened up their online citizen science shop, and the rest is history. But in case you haven’t heard the story yet, a quick rundown is that ‘voorwerp’ means ‘object’ in Dutch – and as of yet, no one has determined exactly what Hanny’s Voorwerp is.
The working hypothesis, according to the Galaxy Zoo team, is that Hanny’s Voorwerp might be a “light echo” of an event that occurred millions of years ago. The object itself consists of dust and gas which perhaps was illuminated by a quasar outburst within the nearby galaxy IC 2497 (see the images). The outburst has faded within the last 100,000 years but the light reached the dust and gas in time for our telescopes to see the effect. Hanny's Voorwerp. Credit: Matt Jarvis, William Herschel Telescope.
The Galaxy Zoo images come from observations done by the Sloan Digital Sky Survey. In evidence of the interest in this object, since 2007 Hanny’s Voorwerp has also been imaged by the Swift gamma-ray satellite, the Suzaku X-ray telescope, the Westerbork Synthesis Radio Telescope (WSRT), the Issac Newton Telescope and the William Herschel Telescope, to name a few.
But now, the most famous telescope of all – with its new and updated instruments – will take a gander to see if the mysteries of the Voorwerp can be solved.
The team – which includes Keel, and fellow Galaxy “Zookeepers” Chris Lintott, Kevin Schawinski, Vardha Nicola Bennert, Daniel Thomas, and Hanny Van Arkel herself – submitted a proposal to the Space Telescope Science Institute back in 2008 and were among the proud and few from close to 1000 proposals submitted to be granted observing time on Hubble.
During the three observing sessions, three different Hubble instruments will be used.
“The observations use three instruments and would naturally be broken into three target visits,” said Keel, “some constrained to be at different times because of the required orientations on the sky –for example, to have both Hanny’s Voorwerp and IC 2497 in the narrow field of view of ACS (Advanced Camera for Surveys) with the monochromatic ramp filters.”
“The next observations will probably be the most visually striking,” Keel continued. “Two orbits’ worth of ACS images in narrow bands including [O III] an H-alpha emission, and are scheduled for April 12. The final visit in the program has 2 orbits of STIS (Space Telescope Imaging Spectrograph) spectroscopy around the nucleus of IC2497, and should be coming up by mid-June.”
The April 4 observations included three orbits of data from the WFC3.
So, even though the first images have now been seen, the team won’t be able to share their findings until all the observations have occurred and the data has been analyzed.
Hanny Van Arkel. Image courtesy of Hanny.
“I indeed can’t say much more than that we got the first data in our mailboxes,” Van Arkel said in an email to Universe Today. “The team is still working on it and until they’ve worked it out, I won’t even understand enough of it myself to explain anything on the matter. It is exciting however that the investigations have started and it’s nice to see how many curious people are sending me messages about it and ‘retweeting’ my quotes on Twitter. After almost two years, I’m very much looking forward to the outcome of all of this!”
Van Arkel isn’t the only one excited.
“Through a combination of geometry and weather,” Keel shared,”I saw HST sail by to our south less than two orbits after it finished this first data set. So I waved in what was probably a most unprofessional manner.”
And the rest of us will be waiting – and waving – until Hubble can tell us more about Hanny’s Voorwerp.
This Hubble Space Telescope image of young brown dwarf 2M J044144 show it has a companion object at the 8 o'clock position that is estimated to be 5-10 times the mass of Jupiter.Credit: NASA, ESA, and K. Todorov and K. Luhman (Penn State University)
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Big planet or companion brown dwarf? Using the Hubble Space Telescope and the Gemini Observatory, astronomers have discovered an unusual object orbiting a brown dwarf, and its discovery could fuel additional debate about what exactly constitutes a planet. The object circles a nearby brown dwarf in the Taurus star-forming region with an orbit approximately 3.6 billion kilometers (2.25 billion miles) out, about the same as Saturn from our sun. The astronomers say it is the right size for a planet, but they believe the object formed in less than 1 million years — the approximate age of the brown dwarf — and much faster than the predicted time it takes to build planets according to conventional theories.
Kamen Todorov of Penn State University and his team conducted a survey of 32 young brown dwarfs in the Taurus region.
The object orbits the brown dwarf 2M J044144 and is about 5-10 times the mass of Jupiter. Brown dwarfs are objects that typically are tens of times the mass of Jupiter and are too small to sustain nuclear fusion to shine as stars do. Artist's conception of the binary system 2M J044144. Science Credit: NASA, ESA, and K. Todorov and K. Luman (Penn State University) Artwork Credit: Gemini Observatory, courtesy of L. Cook
While there has been a lot of discussion in the context of the Pluto debate over how small an object can be and still be called a planet, this new observation addresses the question at the other end of the size spectrum: How small can an object be and still be a brown dwarf rather than a planet? This new companion is within the range of masses observed for planets around stars, but again, the astronomers aren’t sure if it is a planet or a companion brown dwarf star.
The answer is strongly connected to the mechanism by which the companion most likely formed.
The Hubble new release offers these three possible scenarios for how the object may have formed:
Dust in a circumstellar disk slowly agglomerates to form a rocky planet 10 times larger than Earth, which then accumulates a large gaseous envelope; a lump of gas in the disk quickly collapses to form an object the size of a gas giant planet; or, rather than forming in a disk, a companion forms directly from the collapse of the vast cloud of gas and dust in the same manner as a star (or brown dwarf).
If the last scenario is correct, then this discovery demonstrates that planetary-mass bodies can be made through the same mechanism that builds stars. This is the likely solution because the companion is too young to have formed by the first scenario, which is very slow. The second mechanism occurs rapidly, but the disk around the central brown dwarf probably did not contain enough material to make an object with a mass of 5-10 Jupiter masses.
“The most interesting implication of this result is that it shows that the process that makes binary stars extends all the way down to planetary masses. So it appears that nature is able to make planetary-mass companions through two very different mechanisms,” said team member Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Penn State University.
If the mystery companion formed through cloud collapse and fragmentation, as stellar binary systems do, then it is not a planet by definition because planets build up inside disks.
The mass of the companion is estimated by comparing its brightness to the luminosities predicted by theoretical evolutionary models for objects at various masses for an age of 1 million years.
Further supporting evidence comes from the presence of a very nearby binary system that contains a small red star and a brown dwarf. Luhman thinks that all four objects may have formed in the same cloud collapse, making this in actuality a quadruple system.
“The configuration closely resembles quadruple star systems, suggesting that all of its components formed like stars,” he said.
The team’s research is being published in an upcoming issue of The Astrophysical Journal.
This image shows a smoothed reconstruction of the total (mostly dark) matter distribution in the COSMOS field, created from data taken by the NASA/ESA Hubble Space Telescope and ground-based telescopes.Credit: NASA, ESA, P. Simon (University of Bonn) and T. Schrabback (Leiden Observatory)
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Need more evidence that the expansion of the Universe is accelerating? Just look to the Hubble Space Telescope. An international team of astronomers has indeed confirmed that the expansion of the universe is accelerating. The team, led by Tim Schrabback of the Leiden Observatory, conducted an intensive study of over 446,000 galaxies within the COSMOS (Cosmological Evolution Survey) field, the result of the largest survey ever conducted with Hubble. In making the COSMOS survey, Hubble photographed 575 slightly overlapping views of the same part of the Universe using the Advanced Camera for Surveys (ACS) onboard the orbiting telescope. It took nearly 1,000 hours of observations.
In addition to the Hubble data, researchers used redshift data from ground-based telescopes to assign distances to 194,000 of the galaxies surveyed (out to a redshift of 5). “The sheer number of galaxies included in this type of analysis is unprecedented, but more important is the wealth of information we could obtain about the invisible structures in the Universe from this exceptional dataset,” said co-author Patrick Simon from Edinburgh University.
In particular, the astronomers could “weigh” the large-scale matter distribution in space over large distances. To do this, they made use of the fact that this information is encoded in the distorted shapes of distant galaxies, a phenomenon referred to as weak gravitational lensing. Using complex algorithms, the team led by Schrabback has improved the standard method and obtained galaxy shape measurements to an unprecedented precision. The results of the study will be published in an upcoming issue of Astronomy and Astrophysics.
The meticulousness and scale of this study enables an independent confirmation that the expansion of the Universe is accelerated by an additional, mysterious component named dark energy. A handful of other such independent confirmations exist. Scientists need to know how the formation of clumps of matter evolved in the history of the Universe to determine how the gravitational force, which holds matter together, and dark energy, which pulls it apart by accelerating the expansion of the Universe, have affected them. “Dark energy affects our measurements for two reasons. First, when it is present, galaxy clusters grow more slowly, and secondly, it changes the way the Universe expands, leading to more distant — and more efficiently lensed — galaxies. Our analysis is sensitive to both effects,” says co-author Benjamin Joachimi from the University of Bonn. “Our study also provides an additional confirmation for Einstein’s theory of general relativity, which predicts how the lensing signal depends on redshift,” adds co-investigator Martin Kilbinger from the Institut d’Astrophysique de Paris and the Excellence Cluster Universe.
The large number of galaxies included in this study, along with information on their redshifts is leading to a clearer map of how, exactly, part of the Universe is laid out; it helps us see its galactic inhabitants and how they are distributed. “With more accurate information about the distances to the galaxies, we can measure the distribution of the matter between them and us more accurately,” notes co-investigator Jan Hartlap from the University of Bonn. “Before, most of the studies were done in 2D, like taking a chest X-ray. Our study is more like a 3D reconstruction of the skeleton from a CT scan. On top of that, we are able to watch the skeleton of dark matter mature from the Universe’s youth to the present,” comments William High from Harvard University, another co-author.
The astronomers specifically chose the COSMOS survey because it is thought to be a representative sample of the Universe. With thorough studies such as the one led by Schrabback, astronomers will one day be able to apply their technique to wider areas of the sky, forming a clearer picture of what is truly out there.
Paper: Schrabback et al., ‘Evidence for the accelerated expansion of the Universe from weak lensing tomography with COSMOS’, Astronomy and Astrophysics, March 2010,
I have seen the new Hubble 3-D IMAX movie twice now, and both times I was overcome with tears by the end of the film. It wasn’t that the story of Hubble itself was overwhelming; no, that story I already knew by heart. It wasn’t that the account of the servicing mission to save Hubble was especially dramatic; actually, I think watching the five EVAs live on NASA TV in May 2009 was more heart-pounding. And it wasn’t that the cinematography was overly stunning or that there were non-stop 3-D effects.
What this film does is portray the immensity and gloriousness of our universe, and that we are currently, serendipitously, living during an amazing era of discovery, one that humanity has never known before. Some of these discoveries we are only able to make because of this marvelous telescope and the people who laid their lives on the line to fix it and make it better. It also shows — almost subtly – that we are inexorably connected to the Universe around us, joined like the intertwining web of 3-D galaxies shown near the movie’s final scenes. We are witnessing – and are a part of – history.
The movie chronicles the 20-year life of Hubble, and focuses on the STS-125 servicing mission, the final mission to Hubble. There ARE wonderful 3-D views of Hubble itself, anchored to shuttle Atlantis’ payload bay, where the telescope appears to come out into the audience and into your lap. This includes stunning views of planet Earth spinning overhead. “This is a gift we astronauts have been given,” astronaut Mike Massimino says of the vistas that can only be seen from space.
And viewers get to experience not one, but two shuttle launches captured in the so-close-up-you-can-feel-it shots which can only be experienced in IMAX. But much of the footage from on-orbit detailing the EVAs and action inside the shuttle were shot with the regular, albeit high-tech cameras that normally NASA flies on missions, including the small “lipstick” cameras on the helmets of the spacewalkers, and some was able to be rendered in grainy, but effective 3-D. The only genuine IMAX 3-D camera on board the mission was bolted to the shuttle’s cargo bay and it carried only 5,400 feet of film – which translates into just 8 minutes of IMAX 3-D footage. Here’s an article about a 3 D Solar System
Endearing are the behind-the-scenes looks at the STS-125 mission. Astronauts joking with each other on orbit – Commander Scott Altman sticking gum under the shuttle’s “dashboard,” Massimino describing how suiting up for an EVA is like putting on a snowsuit as a child. “You need your Mom,” he says.
In both showings I attended, the scene that got the most audible reaction from the audience was Drew Feustal making a chicken salad tortilla wrap. But, hey, we all have to eat, and for those who have never seen food preparation or astronauts eating in space before, it holds a certain level of fundamental fascination.
Additionally we get to hear what is going through the minds of the astronauts on launch day. Mike Good recalls how his grandfather opened up the Universe by showing him views through a telescope. Megan McArthur glows with excitement. John Grunsfeld meticulously goes through in his mind all the tasks that lie before him and the crew.
The film quickly moves through the EVAs, highlighting anxious moments of the mission — stuck bolts, the handrail that Massimino had to rip off of Hubble, the tension of undertaking the meticulous repairs on a one-of-a-kind iconic telescope, all while wearing a bulky spacesuit. But within a 43 minute film, these situations are dealt with quickly, — and honestly, — the movie doesn’t give real justice to how tense some of these situations really were.
A vast canyon of dust and gas in the Orion Nebula from a 3-D computer model based on observations by NASA's Hubble Space Telescope. Credit: NASA, G. Bacon, L. Frattare, Z. Levay, and F. Summers (STScI/AURA)
But most mesmerizing in the film are 3-D visualizations of actual Hubble data. For this film, regular 2-D Hubble images were converted into 3-D environments, giving the audience the impression they are traveling through space and time.
Viewers get to experience an exhilarating ride through the Orion Nebula, swooping through a giant canyon of gas and dust, and witness star-forming regions that include dusty tadpole-shaped objects that are fledgling solar systems, likely a vision of how our own solar system once looked.
Later we travel to the distant Virgo Cluster and emerge on the other side of a black hole, and then travel back in time to witness early misshapen galaxies. Returning to more recent views that include new images from the Wide Field Camera 3 that was installed on STS-125, we see an ocean of stars in multiple wavelengths. Upon pulling away from the stars, we see 3-D galaxies interwoven like a web.
It’s these mind-numbing visions that produce a child-like sense of awe and wonder – and in my case, tears. The film is a testament to how Hubble has allowed us to see the wonders of our Universe.
I asked for reactions from the members of the audience following the premier showing of Hubble 3-D at the Kennedy Space Center IMAX, and while many commented on the amazing graphics, they also observed how small they felt in comparison to the rest of the Universe, but yet, incredibly an integral part of all that is.
The graphics were created by image processing specialists at Hubble’s Space Telescope Science Institute,– familiar names to those of us that follow Hubble : Frank Summers, Zolt Levay, Lisa Frattare, and Greg Bacon. They worked with the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign (more about them in a subsequent, upcoming article on Universe Today), and the Spitzer Science Center at the California Institute of Technology.
Hubble 3-D was directed by Toni Myers, who has been at the helm of all the space-themed IMAX movies, and narrated by Leonardo DiCaprio.
Go see the movie if you have the chance, and bring anyone who may not normally follow space exploration or astronomy. Their view of the Universe will never be the same.
For more info see the official Hubble 3-D IMAX website. Official trailer below.
This Hubble Space Telescope picture shows three rings of glowing gas encircling the site of Supernova 1987A, a star which exploded in February 1987. Credit: Dr. Christopher Burrows, ESA/STScI and NASA
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An ambitious new project using the Hubble Space Telescope will allow astronomers to peer deep into the universe in five directions to document the early history of star formation and galaxy evolution. Using an unprecedented amount of time of the famed space telescope, the Hubble Multi-Cycle Treasury Program will image more than 250,000 distant galaxies to provide the first comprehensive view of the structure and assembly of galaxies over the first third of cosmic time. “This is an effort to make the best use of Hubble while it is at the apex of its capabilities, providing major legacy data sets for the ages,” said Sandra Faber, project leader from the University of California, Santa Cruz.
Other goals of the project are to look for crucial data on the earliest stages in the formation of supermassive black holes and find distant supernovae important for understanding dark energy and the accelerating expansion of the universe.
The effort relies on Hubble’s powerful new infrared camera, the Wide Field Camera 3 (WFC3), as well as the telescope’s Advanced Camera for Surveys (ACS). The proposal, which brings together a large international team of collaborators, was awarded a record 902 orbits of observing time as one of three large-scale projects chosen for the Hubble Multi-Cycle Treasury Program. The observing time, totaling about three and a half months, will be spread out over the next two to three years.
Hubble allows astronomers to see back in time as it gathers light that has traveled for billions of years across the universe. The new survey is designed to observe galaxies at distances that correspond to “look-back times” from nearly 13 billion years ago (about 600,000 years after the Big Bang) up to about 9 billion years ago. Astronomers express these distances in terms of redshift (“z”), a measure of how the expansion of the universe shifts the light from an object to longer wavelengths. The redshift increases with distance, and this study will look at objects at distances from about z=1.5 to z=8.
“We want to look very deep, very far back in time, and see what galaxies and black holes were doing back then,” Faber said. “It’s important to observe in different regions, because the universe is very clumpy, and to have a large enough sample to count things, so we can see how many of one kind of object versus another kind there were at different times.”
Faber and her fellow astronomers expect the first data from their observations to be available by the end of the year. Data from this project will be made available to the entire astronomy community with no proprietary period for Faber’s team to conduct their own analysis. The likely result will be a race among teams of scientists to publish the first results from this new treasure trove of data. But Faber said the project will yield such rich data it will keep astronomers busy for years to come.
“We’re very excited, not only about the 900 orbits, but also about what this new camera can do. It’s just amazing what it sees,” Faber said. “This project is the biggest event in my career, the culmination of three decades of work using big telescopes to study galaxy evolution.”
Additional information about the project is available on the Cosmology Survey Multi-Cycle Treasury Program web site at http://csmct.ucolick.org/.
Hickson 31 (Credit: NASA, ESA, and S. Gallagher (The University of Western Ontario), and J. English (University of Manitoba))
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Have you heard of ‘living fossils’? The coelacanth, the ginko tree, the platypus, and several others are species alive today which seem to be the same as those found as fossils, in rocks up to hundreds of millions of years old.
Now combined results from the Hubble Space Telescope, Spitzer, Galaxy Evolution Explorer (GALEX), and Swift show that there are ‘living galaxy fossils’ in our own backyard!
Hubble: red, yellow-green, and blue; Spitzer: orange; GALEX: purple
Hickson Compact Group 31 is one of 100 compact galaxy groups catalogued by Canadian astronomer Paul Hickson; the recent study of them – led by Sarah Gallagher of The University of Western Ontario in London, Ontario – shows that the four dwarf galaxies in it are in the process of coming together (or ‘merging’ as astronomers say).
Such encounters between dwarf galaxies are normally seen billions of light-years away and therefore occurred billions of years ago. But these galaxies are relatively nearby, only 166 million light-years away.
New images of this foursome by NASA’s Hubble Space Telescope offer a window into the universe’s formative years when the buildup of large galaxies from smaller building blocks was common.
Astronomers have known for decades that these dwarf galaxies are gravitationally tugging on each other. Their classical spiral shapes have been stretched like taffy, pulling out long streamers of gas and dust. The brightest object in the Hubble image is actually two colliding galaxies. The entire system is aglow with a firestorm of star birth, triggered when hydrogen gas is compressed by the close encounters between the galaxies and collapses to form stars.
The Hubble observations have added important clues to the story of this interacting group, allowing astronomers to determine when the encounter began and to predict a future merger.
“We found the oldest stars in a few ancient globular star clusters that date back to about 10 billion years ago. Therefore, we know the system has been around for a while,” says Gallagher; “most other dwarf galaxies like these interacted billions of years ago, but these galaxies are just coming together for the first time. This encounter has been going on for at most a few hundred million years, the blink of an eye in cosmic history. It is an extremely rare local example of what we think was a quite common event in the distant universe.”
In other words, a living fossil.
Everywhere the astronomers looked in this group they found batches of infant star clusters and regions brimming with star birth. The entire system is rich in hydrogen gas, the stuff of which stars are made. Gallagher and her team used Hubble’s Advanced Camera for Surveys to resolve the youngest and brightest of those clusters, which allowed them to calculate the clusters’ ages, trace the star-formation history, and determine that the galaxies are undergoing the final stages of galaxy assembly.
The analysis was bolstered by infrared data from NASA’s Spitzer Space Telescope and ultraviolet observations from the Galaxy Evolution Explorer (GALEX) and NASA’s Swift satellite. Those data helped the astronomers measure the total amount of star formation in the system. “Hubble has the sharpness to resolve individual star clusters, which allowed us to age-date the clusters,” Gallagher adds.
Hubble reveals that the brightest clusters, hefty groups each holding at least 100,000 stars, are less than 10 million years old. The stars are feeding off of plenty of gas. A measurement of the gas content shows that very little has been used up – further proof that the “galactic fireworks” seen in the images are a recent event. The group has about five times as much hydrogen gas as our Milky Way Galaxy.
“This is a clear example of a group of galaxies on their way toward a merger because there is so much gas that is going to mix everything up,” Gallagher says. “The galaxies are relatively small, comparable in size to the Large Magellanic Cloud, a satellite galaxy of our Milky Way. Their velocities, measured from previous studies, show that they are moving very slowly relative to each other, just 134,000 miles an hour (60 kilometers a second). So it’s hard to imagine how this system wouldn’t wind up as a single elliptical galaxy in another billion years.”
Adds team member Pat Durrell of Youngstown State University: “The four small galaxies are extremely close together, within 75,000 light-years of each other – we could fit them all within our Milky Way.”
Why did the galaxies wait so long to interact? Perhaps, says Gallagher, because the system resides in a lower-density region of the universe, the equivalent of a rural village. Getting together took billions of years longer than it did for galaxies in denser areas.
Hubble's view of Saturn with a double view of its fluttering aurorae. Credit: NASA, ESA and Jonathan Nichols (University of Leicester)
In January and March 2009, researchers using Hubble took advantage of a rare opportunity to record Saturn when its rings are edge-on, resulting in a unique look featuring both of the giant planet’s poles. And Saturn cooperated by providing an incredible double light show with Saturn’s own northern and southern lights. Since Saturn is only in this position every 15 years or so, this favorable orientation has allowed a sustained study of the two beautiful and dynamic aurorae.
Since it takes Saturn almost thirty years to orbit the Sun, the opportunity to image both of its poles occurs only twice in that period. Hubble has been snapping pictures of the planet at different angles since the beginning of the mission in 1990, but 2009 brought a unique chance for Hubble to image Saturn with the rings edge-on and both poles in view. At the same time Saturn was approaching its equinox so both poles were equally illuminated by the Sun’s rays.
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These recent observations go well beyond just a still image and have allowed researchers to monitor the behavior of both Saturn’s poles in the same shot over a sustained period of time. The movie they created from the data, collected over several days during January and March 2009, has aided astronomers studying both Saturn’s northern and southern aurorae. Given the rarity of such an event, this new footage will likely be the last and best equinox movie that Hubble captures of our planetary neighbor.
Despite its remoteness, the Sun’s influence is still felt by Saturn. The Sun constantly emits particles that reach all the planets of the Solar System as the solar wind. When this electrically charged stream gets close to a planet with a magnetic field, like Saturn or the Earth, the field traps the particles, bouncing them back and forth between its two poles. A natural consequence of the shape of the planet’s magnetic field, a series of invisible “traffic lanes” exist between the two poles along which the electrically charged particles are confined as they oscillate between the poles. The magnetic field is stronger at the poles and the particles tend to concentrate there, where they interact with atoms in the upper layers of the atmosphere, creating aurorae, the familiar glow that the inhabitants of the Earth’s polar regions know as the northern and southern lights.
At first glance the light show of Saturn’s aurorae appears symmetric at the two poles. However, analysing the new data in greater detail, astronomers have discovered some subtle differences between the northern and southern aurorae, which reveal important information about Saturn’s magnetic field. The northern auroral oval is slightly smaller and more intense than the southern one, implying that Saturn’s magnetic field is not equally distributed across the planet; it is slightly uneven and stronger in the north than the south. As a result, the electrically charged particles in the north are accelerated to higher energies as they are fired toward the atmosphere than those in the south. This confirms a previous result obtained by the space probe Cassini, in orbit around the ringed planet since 2004.
Source: ESA
