The Deepest Photo Ever Taken 218
Astroturtle writes "Astronomers using the Hubble Space Telescope's powerful new Advanced Camera for Surveys (ACS) have taken the deepest visible-light image ever made of the sky. The 3.5-day (84-hour) exposure captures stars as faint as 31st magnitude, according to Tom M. Brown (Space Telescope Science Institute), who headed the eight-person team that took the picture."
article (Score:3, Informative)
The 3.5-day (84-hour) exposure captures stars as faint as 31st magnitude, according to Tom M. Brown (Space Telescope Science Institute), who headed the eight-person team that took the picture. This is a little more than 1 magnitude (2.5 times) fainter than the epochal Hubble Deep Fields, which were made with the Hubble's Wide Field and Planetary Camera 2. It is 6 billion times fainter than what can be seen with the naked eye.
Brown and his colleagues chose to point at a spot 1 southeast of M31, the Great Andromeda Galaxy, in order to get a census of faint stars populating M31's outer halo. The full ACS image is about 3.1 arcminutes square, the size of a sand grain held at arm's length against the sky. The ACS magnifies this small field into a vast panorama of some 300,000 stars and thousands of faint background galaxies. At M31's distance of 2.5 million light-years, the faintest of the stars are slightly less luminous than our Sun. A large fraction of the most distant galaxies appear patchy and irregular, testimony to the collisions and mergers in the early universe that built up the familiar galaxies we see closer around us today.
Most of the stars in the image indeed proved to be in M31's halo, judging from their colors and brightnesses. Moreover, they show a surprisingly wide range of estimated ages -- from 6 to 13 billion years, compared to 11 to 13 billion years for our Milky Way's halo stars. Perhaps M31 has captured and torn apart younger dwarf galaxies than our Milky Way has done. Or perhaps M31 underwent a massive, disruptive merger with a single large galaxy billions of years ago; in this scenario some of M31's younger disk stars could have been flung into its halo. Or maybe some combination of these events triggered waves of star formation in regions that ended up in M31's outer fringes.
The image was made in two colors: near-infrared and "visual" (a band spanning the part of the spectrum running from yellow through green). The renditions displayed here were crafted to resemble true-color views by interpolating from these two colors. These vignettes each show only about 1 percent of the ACS image. The full image is available from the Hubble Telescope's press site at various qualities and sizes (up to 128 megabytes), along with more highlights and a finder chart showing its relation to M31.
Plans are afoot for an even deeper "Ultra-Deep Field," which will use ACS for longer exposures in four colors and go slightly fainter still.
Re:Details on the exposure techniques? (Score:3, Informative)
Shameless karma whoring: (Score:5, Informative)
http://imgsrc.hubblesite.org/hu/db/2003/15/images
hubblesite.org news release (Score:5, Informative)
Re:Details on the exposure techniques? (Score:5, Informative)
When Hubble needs to move to a new target, engineers on Earth radio a signal to the HST flight computer. The flight computer then activates the Reaction Wheels.
Reaction wheels are heavy fly wheels that spin. As they spin, the momentum from their motion causes the telescope to move. There are four Reaction Wheels. By spinning each one at a certain speed and in a certain direction, engineers can point the telescop e anywhere they want.
hubblesite.org (Score:5, Informative)
Hubblesite.org [hubblesite.org]
Re:3.5 Day Exposure? (Score:5, Informative)
As far as color and reciprocity, Hubble color shots are not always as the eye sees them. The famous "pillars of creation" shot for example, presented the light from oxygen ionization in one color, the light from sulfur ionization in another color, the light from hydogren ionization in another color.
Re:It would be interesting to know... (Score:3, Informative)
There are a few different ways of measuring magnitude (apparent, bolometric, etc). Bolometric is essentially the integral over all wavelengths. I'm guessing they didn't do a real bolometric measurement, but I could be wrong.
Anyway, the relationship between intensity (I) and apparent magnitude (m) is Intensity is in units of power/area, such as W/m^2 or ergs/cm^2 (cgs units are oddly popular in astronomy).
If they did do a bolometric measurement, you can pretty easily manipulate this relationship to reflect that.
Now, from the power, knowing the wavelength(s), and using the fact that the energy per photon is the frequency times Planck's constant... and thus you can find the number of photons per unit time per unit area. Which, when coupled with the known exposure time, will give you the total number of photons.
exposure time misleading (Score:5, Informative)
For those who are interested, the original hubble press release is located here [hubblesite.org].
The site includes the image in a variety of different formats, including a 123 MB tiff file.
Re:3.5 Day Exposure? (Score:5, Informative)
Actually, rotates, not moves (Score:5, Informative)
As they spin, the momentum from their motion causes the telescope to move.
Well, it's techincally a litter different than that. The wheels don't actually cause hubble to translate within a plane. Instead they rotate hubble. By turning the spinning wheels, a torque is exerted on hubble, causing it to rotate.
neurostarIt's due to the way telescopes are built. (Score:5, Informative)
(Astronomers understand the diffraction issues very well... it's usually not a problem; it just looks weird.)
- A friendly neighborhood astrophysicist
Re:Details on the exposure techniques? (Score:5, Informative)
(*) except for a small patch of sky called the CVZ: continuously visible zone
BTW, if you're keeping score at home, 30th magnitude is 1 trillion times fainter than the human eye can see!
[*shameless plug* Tom Brown is using my thesis code to analyze these data
Re:It would be interesting to know... (Score:5, Informative)
the deepest photo that will *ever* be taken (Score:4, Informative)
For an interesting article, see:
http://www.sciam.com/article.cfm?colID=1&articl
On parallel universes. Very interesting reading. If you're at a university, you will be able to browse the site's archives and access the nice PDF version of the article (which has the pictures supersized to full-page size).
Re:What's up with the points? (Score:2, Informative)
Re:Streaks (Score:5, Informative)
The big bright cluster is actually a member of Andromedae (M31). Very impressive! The appearance of fuzziness is because the CCD oversamples the resolution of the telescope - which is necessary for good photometry - if you want it "sharp" then just bin the pixels by 2x2 or 3x3 or whatever looks best!
Mirror of full JPG (Score:5, Informative)
http://wuarchive.wustl.edu/users/tom/mirrors/hu
is a mirror of the full JPEG - about 5M. Enjoy.
Comment removed (Score:5, Informative)
122.75 MB TIFF and More! (Score:3, Informative)
-Lucas
Re:All in all... (Score:3, Informative)
Not Several Millions, we're talking Billions...
According to http://hubble.nasa.gov/faq.html [nasa.gov] it cost $1.5 billion Plus another $230-250 million each year for maintenence. Estimated costs to fix the lens problem on the telescope were $20 million. Since the Hubble was launched in 1990 and is planned to operate until 2010, that's $230M per year for 20 years = $4.6 Billion + the $1.5 Billion initial cost. That's a total cost of operation equal to $6.1 Billion (low estimate that doesn't include the cost of engineering and scientific knowledge needed for this to happen).
In my opinion, the information it sends back is priceless to humanity, and well worth whatever cost it takes.
Re:the deepest photo that will *ever* be taken (Score:5, Informative)
Here's your deepest image then:
http://map.gsfc.nasa.gov/m_ig/020598/02059
That's from the recent WMAP mission, which mapped the cosmic microwave background in exquisite detail, pinpointing the age of the Universe (and many other cosmological parameters) to high precision. You're looking at an all-sky image of the Universe as it looked when it was 100,000 years old, and became transparent for the first time. IOW, you are literally seeing the fires of creation.
MOD PARENT DOWN. (Score:2, Informative)
He doesn't deserve positive karma until he learns some respect. When he learns to treat people of all colors as he wishes to be treated himself, then perhaps he can contribute to the discussion in a worthwhile manner.
What goes around, comes around. Paranoid delusions about people of other races (sexes / political and religious beliefs) are so 1700's and have no place in an advanced civilisation.
Re:The imag is not blurred; thats whats interestin (Score:3, Informative)
[TMB]
Re:It would be interesting to know... (Score:1, Informative)
"Traits come in groups. More than one trait is needed to clearly identify a taxonomic class. Niggers have dirty skin, pubic hair on their heads, broad and flat noses, etc. Why can't being a lowlife, useless, stupid, lazy, criminal shitmonkey be considered part of such a group of common traits? Just because some things are negative we shouldn't consider them??
As for the nature vs. nurture issue, we'll put that aside for this discussion (it's well outside the scope anyway). Suffice it to say that, if a nigger raises a nigglet, the point becomes moot.
"Anti-racists" deny the facts of reality because they wish the world followed their ideal. I live in reality. In reality niggers/spics/kikes/chinks/dotheads/etcetera lower the quality of life for everyone. For that they should fucking die.
How can someone be so fucking stupid and not realize that THEY are the ones lowering the quality of life for everyone? Whenever I've been ripped off in my life, it was a white man. I'm not that old okay, 38, but still I think stupid fucks like that guy and their sympathizers should get fucking locked up or at least sterilized. They make me ashamed of being white.
It's just a game, yeah right. You do realize that kids love FPS games, huh? I'm against censorship, but at least we shouldn't treat it like any random game?! FUCKING BRAINLESS FOOL.
Re:Details on the exposure techniques? (Score:4, Informative)
If only one star is available, guiding is still possible, but the field may slowly rotate, since one star only provides one of the two needed pointing constraints (of position and orientation).
A big project in preparation for Hubble was the creation of the Hubble Guide Star catalog, exactly for this purpose -- to make sure that given what people would want to observe, there would always be enough guide stars within an acceptable distance!
for more information, see here [stsci.edu] if you're interested! If you're ambitious, you can even read the instrument handbooks for yourself: here [stsci.edu]
Comment removed (Score:3, Informative)
Re:What's up with the points? (Score:2, Informative)
No quantum mechanics, just plain ol' classical optics. Those are diffraction patterns. Crosses are the Fourier transform of a square, so I assume their aperature stop is a square.
-JS