Posted on 03/09/2004 11:11:27 AM PST by alnitak
Hubble's deepest view ever unveils earliest galaxies
SPACE TELESCOPE SCIENCE INSTITUTE NEWS RELEASE
Posted: March 9, 2004
Astronomers at the Space Telescope Science Institute today unveiled the deepest portrait of the visible universe ever achieved by humankind. Called the Hubble Ultra Deep Field (HUDF), the million-second-long exposure reveals the first galaxies to emerge from the so-called "dark ages," the time shortly after the big bang when the first stars reheated the cold, dark universe. The new image should offer new insights into what types of objects reheated the universe long ago.
 This view of nearly 10,000 galaxies is the deepest visible-light image of the cosmos. Called the Hubble Ultra Deep Field, this galaxy-studded view represents a "deep" core sample of the universe, cutting across billions of light-years. Credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team Download a larger image here |
"Hubble takes us to within a stone's throw of the big bang itself," says Massimo Stiavelli of the Space Telescope Science Institute in Baltimore, Md., and the HUDF project lead. The combination of ACS and NICMOS images will be used to search for galaxies that existed between 400 and 800 million years (corresponding to a redshift range of 7 to 12) after the big bang. A key question for HUDF astronomers is whether the universe appears to be the same at this very early time as it did when the cosmos was between 1 and 2 billion years old.
The HUDF field contains an estimated 10,000 galaxies. In ground-based images, the patch of sky in which the galaxies reside (just one-tenth the diameter of the full Moon) is largely empty. Located in the constellation Fornax, the region is below the constellation Orion.
The final ACS image, assembled by Anton Koekemoer of the Space Telescope Science Institute, is studded with a wide range of galaxies of various sizes, shapes, and colors. In vibrant contrast to the image's rich harvest of classic spiral and elliptical galaxies, there is a zoo of oddball galaxies littering the field. Some look like toothpicks; others like links on a bracelet. A few appear to be interacting. Their strange shapes are a far cry from the majestic spiral and elliptical galaxies we see today. These oddball galaxies chronicle a period when the universe was more chaotic. Order and structure were just beginning to emerge.
 These close-up snapshots of galaxies in the Hubble Ultra Deep Field reveal the drama of galactic life. Credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team Download a larger image here |
The NICMOS sees even farther than the ACS. The NICMOS reveals the farthest galaxies ever seen, because the expanding universe has stretched their light into the near-infrared portion of the spectrum. "The NICMOS provides important additional scientific content to cosmological studies in the HUDF," says Rodger Thompson of the University of Arizona and the NICMOS Principal Investigator. The ACS uncovered galaxies that existed 800 million years after the big bang (at a redshift of 7). But the NICMOS may have spotted galaxies that lived just 400 million years after the birth of the cosmos (at a redshift of 12). Thompson must confirm the NICMOS discovery with follow-up research.
"The images will also help us prepare for the next step from NICMOS on the Hubble telescope to the James Webb Space Telescope (JWST)," Thompson explains. "The NICMOS images reach back to the distance and time that JWST is destined to explore at much greater sensitivity." In addition to distant galaxies, the longer infrared wavelengths are sensitive to galaxies that are intrinsically red, such as elliptical galaxies and galaxies that have red colors due to a high degree of dust absorption.
The entire HUDF also was observed with the advanced camera's "grism" spectrograph, a hybrid prism and diffraction grating. "The grism spectra have already yielded the identification of about a thousand objects. Included among them are some of the intensely faint and red points of light in the ACS image, prime candidates for distant galaxies," says Sangeeta Malhotra of the Space Telescope Science Institute and the Principal Investigator for the Ultra Deep Field's ACS grism follow-up study. "Based on those identifications, some of these objects are among the farthest and youngest galaxies ever seen. The grism spectra also distinguish among other types of very red objects, such as old and dusty red galaxies, quasars, and cool dwarf stars."
Galaxies evolved so quickly in the universe that their most important changes happened within a billion years of the big bang. "Where the HDFs showed galaxies when they were youngsters, the HUDF reveals them as toddlers, enmeshed in a period of rapid developmental changes," Stiavelli says.
 Illustration Credit: NASA and A. Feild (STScI) Download a larger image here |
Though ground-based telescopes have, to date, spied objects that existed just 500 million years after the big bang (at a redshift of 10), they need the help of a rare natural zoom lens in space, called a gravitational lens, to see them. However, the ACS can reveal typical galaxies at these great distances. Even much larger ground-based telescopes with adaptive optics cannot reproduce such a view. The ACS picture required a series of exposures taken over the course of 400 Hubble orbits around Earth. This is such a big chunk of the telescope's annual observing time that Institute Director Steven Beckwith used his own Director's Discretionary Time to provide the needed resources.
The HUDF observations began Sept. 24, 2003 and continued through Jan. 16, 2004. The telescope's ACS camera, the size of a phone booth, captured ancient photons of light that began traversing the universe even before Earth existed. Photons of light from the very faintest objects arrived at a trickle of one photon per minute, compared with millions of photons per minute from nearer galaxies.
Just like the previous HDFs, the new data are expected to galvanize the astronomical community and lead to dozens of research papers that will offer new insights into the birth and evolution of galaxies.
Questions & Answers
1. How faint are the farthest objects?
The Hubble observations detected objects as faint as 30th magnitude. The faintest objects the human eye can see are at sixth magnitude. Ground-based telescopes also can detect 30th-magnitude objects. Those objects, however, are so dim they are lost in the glare of brighter, nearby galaxies.
Searching for the faintest objects in the Ultra Deep Field is like trying to find a firefly on the Moon. Light from the farthest objects reached the Hubble telescope in trickles rather than gushers. The orbiting observatory collected one photon of light per minute from the dimmest objects. Normally, the telescope collects millions of photons per minute from nearby galaxies.
2. How many orbits did it take to make the observations?
It took 400 orbits to make the observations.
3. How many exposures were needed to make the observations?
The Hubble telescope's Advanced Camera for Surveys' wide-field camera snapped 800 exposures, which equals two exposures per orbit. The exposures were taken over four months, from Sept. 24, 2003 to Jan. 16, 2004.
4. How much viewing time was needed to make all the exposures?
The 800 exposures amounted to about 1 million seconds or 11.3 days of viewing time. The average exposure time was 21 minutes.
5. How many galaxies are in the image?
The image yields a rich harvest of about 10,000 galaxies.
6. How many colors (filters) were used to make the observations?
The colors used were blue, green, red, and near-infrared. The observations were taken in visible to near-infrared light.
7. If astronomers made the Hubble Ultra Deep Field observation over the entire sky, how long would it take?
The whole sky contains 12.7 million times more area than the Ultra Deep Field. To observe the entire sky would take almost 1 million years of uninterrupted observing.
8. How wide is the Ultra Deep Field's slice of the heavens?
The Hubble Ultra Deep Field is called a "pencil beam" survey because the observations encompass a narrow, yet "deep" piece of sky. Astronomers compare the Ultra Deep Field view to looking through an eight-foot-long soda straw.
The Ultra Deep Field's patch of sky is so tiny it would fit inside the largest impact basin that makes up the face on the Moon. Astronomers would need about 50 Ultra Deep Fields to cover the entire Moon.
9. How sharp is Hubble's resolution in pinpointing far-flung galaxies in the Ultra Deep Field?
Hubble's keen vision (0.085 arc seconds.) is equivalent to standing at the U.S. Capitol and seeing the date on a quarter a mile away at the Washington monument.
WOW i went there...i tink i drain bead now..i mean brain dead...
Well... Think about this. Take a really big magnifying glass. Look at a human hair or just the back of your hand. You will see lots of detail that you couldn't before. This doesn't mean the light hasn't reached you yet. It just means your eye wasn't adequate for seeing it in that detail.
Take this a bit further. Get a good pair of binos and look at something a few hundred meters away. You'll definitely see things that you couldn't see before but the light from that object was always there.
A telescope is just a 'light bucket'. It's designed to collect light. So is your eye. But the telescope's objective (its lens) is much bigger than the one in your eye- thus it can collect more light and you can see things with a telescope that your unaided eye could not. But the light was always there.
The light from those galaxies was there last year. Last century. We just didn't possess an instrument strong enough to view it. It's not like the 'first light' from that galaxy is 'just now' getting here. The light from that galaxy from last month is how that galaxy looked N Billion years ago minus one month.
The light was there before we had Hubble. We just didn't have the capability of seeing it.
You can go out on any given clear night and spot two or three planets, thus their light is plainly making it to Earth. But you won't see Saturn's rings without a scope- even though the light is available on any given evening.
Regards
When they reach the limits of the universe, what they will find are several billion socks and an equal amount of remote controls.
Well all of it. At any given time, when you look at the night heavens you are looking at objects that are different distances away from you.
We must remember though- all the light is getting to you at the same time.
Think about this. Let's say you live in St Louis. Now, you have a friend in every different major city in America. New York, LA, Atlanta etc. They all agree to get in their car and drive to your house. They will all leave at the same time. They will all drive at a constant speed of 40 MPH. They will all tell you what was playing on the television when they left.
They all leave at the same time. And when they eventually get to your house, they will all tell the same story about what was on the network news and so forth. But they will all get there at radically different times. For instance, the guy coming from Kansas City would tell you the news a long time before the guy from Anchorage. But they would all have the same story about the news because they all left at the same time.
Now, let's look at the experiment a different way. Again, your friends are going to drive to your house and tell you what was on the news. But this time, they are going to leave at different times- depending on their distance from you- in order that they might all arrive at the same time (picture Christmas Day- everybody wants to get there at 12 noon).
In other words. Your friends in Anchorage and LA will leave a lot sooner than your friends in Kansas City and Chicago in order that they arrive at the same time.
This time, when they all arrive, they will have different stories about what was on the news because they would have left at different times. For instance, the guy leaving from Anchorage might have news from two or three days earlier than the guy leaving from Atlanta. The only constant factor will be that you are receiving news that is all in the past. Some of the news will be older than other news but it will all already have happened although you might only be hearing it for the first time.
That's what you're facing when you look at the heavens. The light that gets here from Proxima Centauri (our closest star) gets here at the same time (from your perspective) as the light from the furthest galaxy. But they left at different times to get here at that instant. The light from Proxima Centauri is showing you what happened only 4 years ago. But other light that you can see at any given time when you look at the stars is showing you what happened thousands or millions or billions of years ago (depending upon how far away it is).
Just like those friends who left at different times in order to get to your house at the same instant and tell you what the news was at that moment, when we look at the heavens, we are viewing the 'news' that was current when that light left that object. And that news is different for each one because the distances we're dealing with are vast beyond imagination.
So, any particular part of the sky that you look at is revealing the news from different parts of the past because the objects you view in the sky are at radically differing distances.
I don't know if that's the simple terms you're looking for, but that's as simple as I know how to put. I hope that helps.
Here is the pic via The Dallas Morning News article ...Hubble images show deepest view of the universe
Hubble images show deepest view of the universe
Hubble images show deepest view of the universe06:06 PM CST on Tuesday, March 9, 2004
BALTIMORE – Astronomers unveiled the deepest-ever look into the distant reaches of the universe on Tuesday, revealing baby galaxies that lit up the cosmic darkness soon after the big bang.
Scientists hailed the two new long-exposure images, taken by the Hubble Space Telescope, as some of the most awe-inspiring science ever to come from the orbiting observatory. Hubble took a similar picture of a distant spot in the universe in 1995, but the new pictures reach farther back, to a time when the first stars and galaxies were beginning to light up after the universe was born, about 13.7 billion years ago.
NASANearly 10,000 galaxies are seen in this composite image made with the Hubble Space Telescope and released by NASA on Tuesday. Click to: See the large Hubble image | Send it as an e-card"This is Hubble's day," said a jubilant Sen. Barbara Mikulski of Maryland as she helped pull the curtain off a giant display showing at least 10,000 galaxies speckling the dark background of space.
But underlying the celebrations at the Space Telescope Science Institute in Baltimore, where the Hubble is run and where the new images were presented, was an undercurrent of frustration and sadness that NASA has canceled a scheduled shuttle trip to refurbish the telescope. Without a visit from astronauts, the Hubble could stop working as early as 2007.
For now, astronomers are gobbling up every morsel of Hubble science, including the new images, known as the Hubble Ultra Deep Field.
To create the images, the space telescope repeatedly looked at a spot in the constellation Fornax, for a total of 1 million seconds, over several months. The resulting pictures revealed the myriad galaxies, some no brighter than a firefly's glow would be at the distance of the moon.
Light left those galaxies more than 13 billion years ago, when the universe was less than 5 percent of its current age, said Steven Beckwith, director of the space telescope institute.
Astronomer Massimo Stiavelli, leader of one of the two imaging teams, compared the Ultra Deep Field's improvement to watching the amazing growth of an infant in the critical period between 2 months and 4 months of age.
"This is a crucial time for the universe – a kind of teething time for the universe," he said.
One of the new images comes from the telescope's Advanced Camera for Surveys, a phone-booth-sized 16-megapixel digital camera installed by visiting astronauts in 2002. Its sharp focus can make out details in the most distant galaxies.
The other image comes from the NICMOS instrument, which had run out of its needed coolant and stopped working until the astronauts installed a special refrigerator in 2002 to rejuvenate it. It works in near-infrared wavelengths, which allows it to photograph more distant – and thus older – cosmic objects than the advanced camera can but with slightly less clarity.
Astronomers won't see anything else like the Ultra Deep Field for a long time, said Dr. Beckwith. Hubble's successor, the James Webb Space Telescope, isn't scheduled for launch until 2011, and it will study the universe only in infrared wavelengths.
Hubble's life expectancy is now dictated mainly by its aging batteries, which were due to be replaced on the servicing mission in 2006, and its gyroscopes, which are needed to point the telescope properly. After both fail, NASA plans to fly an unmanned rocket that will attach itself to Hubble and guide it safely to a crash landing in the ocean.
NASA administrator Sean O'Keefe canceled the 2006 servicing mission to Hubble in January, after President Bush announced that the space shuttle, when it returns to flight, should focus on completing the International Space Station. Sen. Mikulski, whose district includes the space telescope institute, has asked Mr. O'Keefe to gather expert commentary on that decision, in hopes of reversing it.
Congressman Mark Udall of Colorado last week introduced a resolution in the House of Representatives urging that Mr. O'Keefe appoint an independent panel to examine all possible options for carrying out the servicing mission.
E-mail awitze@dallasnews.com
Online at: http://www.dallasnews.com/sharedcontent/dws/dn/latestnews/stories/030904dnnatuniverse.6c4b18b5.html
So "as many stars as there are grains of sand" isn't really that far off of an estimate.
Or better yet, the deficit, as a percent of total stars, is not significantly above historic levels.
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