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Deep Universe

31 Jan 2011, 05:00 UTC
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Close-Up of Galaxies from the Hubble Ultra Deep Field Image.

In order to observe the most distant objects in the universe, one needs two things: very fine resolution and very long exposures. As a space telescope, Hubble provides the detailed view. However, getting several days worth of exposure for a single observation on this valuable resource is an extremely tall order, since there are many more requests from astronomers to use Hubble than there are hours available to use it. Nevertheless, Hubble has done a few deep images looking across the universe, and unveiled some dramatic findings. To call these observations mind-bending is an understatement, as one has to traverse several deep concepts about space and time before even grasping the nature of the results. Join us for a scientific story that takes place a long, long time ago in galaxies far, far away.

Hubble press releases:

Hubble's Deepest View of the Universe Unveils Bewildering Galaxies across Billions of Years
Hubble's Deepest View Ever of the Universe Unveils Earliest Galaxies
Hubble Approaches the Final Frontier: The Dawn of Galaxies
Hubble Reaches the "Undiscovered Country" of Primeval Galaxies
In Deep Galaxy Surveys, Astronomers Get a Boost Ñ from Gravity


In the show description above, I paraphrase "a long, long time ago in a galaxy far, far away," which is, of course, from the opening of the movie "Star Wars." It serves as a nice touchstone for the public that is, coincidentally, scientifically accurate. If a galaxy is far, far away, then any news we have about it could only be from long, long ago. In fact, given the large spiral galaxy shown in one of the ending shots of "The Empire Strikes Back" (a shot that is definitely NOT scientifically accurate), the adventures of Luke, Han, and Leia must have taken place at least several million years ago. But I doubt George Lucas knew his opening line was scientifically correct. After all, he didn't know that a "parsec" is a unit of distance, not time.

The initial press release for the Hubble Deep Field (HDF) in January 1996 states that the image contains "at least 1,500 galaxies." This number was the result of rather quick image processing and analysis, as the observations had only been completed about two weeks prior. Later, improved study revealed the number of objects in the HDF to be closer to 3,000. Why the rush? The American Astronomical Society (AAS) holds their winter meeting — one of the best events at which to publicize a major result — each January. Also, the HDF data was shared immediately with the entire astronomical community, and the AAS meeting was the perfect time to get the word out.

The concept of "out in space equals back in time" is a fundamental part of thinking like an astronomer. It can, however, lead to some confusion in dating events like supernova explosions. Supernova 1987A was observed on Earth in 1987, but, since the explosion took place in the Large Magellanic Cloud (LMC), the event really occurred about 170,000 years earlier. One tries to be careful to differentiate between the date it was observed and the date it exploded, but it is easy to slip. Just think, if supernovae occur about once a century, there are about 1700 stellar explosions that have already occurred in the LMC, but which we have yet to see. Going further, most of the major astronomical discoveries of the rest of our lives have already happened, and astronomers are just waiting for the light from those distant objects to reach us. That's thinking in terms of space-time.

Here at STScI, we produced an IMAX short film called "Hubble: Galaxies Across Space and Time."

The film explores the Great Observatories Origins Deep Survey (GOODS) and highlights the changes in galaxy shapes with distance, and therefore time. The film features a journey into the GOODS image with all the galaxies placed at their correct relative distances based upon their measured redshifts. One thing to note is that the distances in the film are compressed by a factor of several hundred to make a better film shot, but otherwise the visuals are all Hubble data. We created a similar journey into the Hubble Ultra Deep Field for the IMAX film "Hubble 3D."

Image Notes

Milky Way Panorama
Credit & Copyright: A. Mellinger

Stars of the Big Dipper
Credit & Copyright: A. Fujii/DMI

Hubble Deep Field
Credit: R. Williams (STScI), the Hubble Deep Field Team, and NASA

Astronaut Buzz Aldrin and Flag on Moon, Apollo 11
Credit: NASA

Sunset at the De Tian waterfall, Da Xing, Guang Xi, China
Credit: Wikimedia Commons user SEVEN

Neptune from Voyager 2
Credit: NASA/JPL-Caltech

Alpha, Beta, and Proxima Centauri
Credit & Copyright: Noel Cramer

Large Magellanic Cloud
Credit & Copyright: David Malin, Australian Astronomical Observatory

Andromeda Galax
Credit: Bill Schoening, Vanessa Harvey/REU program/NOAO/AURA/NSF

Virgo Cluster Region from the Digitized Sky Survey
Credit: NASA, ESA, and the Ditigized Sky Survey
Acknowledgment: Z. Levay (STScI) and D. De Martin (for ESA/Hubble)

Star Field Centered on Fornax
Credit & Copyright: A. Fujii/DMI

Hubble Ultra Deep Field
Credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team

Details from the Hubble Ultra Deep Field
Credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team

Evolution of Spiral Galaxies in GOODS
Credit: NASA, ESA, F. Summers and Z. Levay (STScI)

"Tadpole" Galaxies from the Hubble Ultra Deep Field
Credit: NASA, A. Straughn, S. Cohen, and R. Windhorst (Arizona State University), and the HUDF team (STScI)

Redshift Wavelength Stretch
Credit: F. Summers (STScI)

Redshift Animation
Credit: C. Godfrey (STScI)

Hubble Ultra Deep Field in Infrared Light
Credit: NASA, ESA, G. Illingworth and R. Bouwens (University of California, Santa Cruz), and the HUDF09 Team

Detail of Infrared HUDF
Credit: NASA, ESA, G. Illingworth and R. Bouwens (University of California, Santa Cruz), and the HUDF09 Team

Distant Galaxy Candidates in Infrared HUDF
Credit: NASA, ESA, S. Wyithe (University of Melbourne), H. Yan (Ohio State University), R. Windhorst (Arizona State University), and S. Mao (Jodrell Bank Center for Astrophysics, and National Astronomical Observatories of China)
Acknowledgment: G. Illingworth and R. Bouwens (University of California, Santa Cruz), and the HUDF09 Team

Artist's Depiction of James Webb Space Telescope
Credit: NASA

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