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Hubble Catches Up With Distant Supernovae


These snapshots, taken by NASA’s Hubble Space Telescope, reveal five supernovae, or exploding stars, and their host galaxies.

These snapshots, taken by NASA's Hubble Space Telescope, reveal five supernovae, or exploding stars, and their host galaxies.
Click image to enlarge

The arrows in the top row of images point to the supernovae. The bottom row shows the host galaxies before or after the stars exploded. The supernovae exploded between 3.5 and 10 billion years ago.

Astronomers used the supernovae to measure the expansion rate of the universe and determine how the expansion rate is affected by the repulsive push of dark energy, a mysterious energy force that pervades space. Supernovae provide reliable measurements because their intrinsic brightness is well understood. They are therefore reliable distance markers, allowing astronomers to determine how far away they are from Earth.

Pinpointing supernovae in the faraway universe is similar to watching fireflies in your back yard. All fireflies glow with about the same brightness. So, you can judge how the fireflies are distributed in your back yard by noting their comparative faintness or brightness, depending on their distance from you.

Only Hubble can measure these supernovae because they are too distant, and therefore too faint, to be studied by the largest ground-based telescopes.

These Hubble observations show for the first time that dark energy has been a present force for most of the universe's history. A spectral analysis also shows that the supernovae used to measure the universe’s expansion rate today look remarkably similar to those that exploded nine billion years ago and are just now seen by Hubble.

These latest results are based on an analysis of the 24 most distant known supernovae, most of them discovered within the last three years by the Higher-z SN Search Team. The images were taken between 2003 and 2005 with Hubble’s Advanced Camera for Surveys. + Click for high resolution tif image (1.5 Mb)

Credit: NASA, ESA, and A. Riess (Space Telescope Science Insitute)

Graphic illustrating the cosmic forces in play.
Click image to enlarge

The graphic above serves to illustrate the "cosmic tug of war" that has been going on since the beginning of the universe.

NASA will host a media teleconference with Hubble Space Telescope astronomers at 1 p.m. EST Thursday, Nov. 16, to announce the discovery that dark energy has been an ever-present constituent of space for most of the universe's history.

Reporters must call Ray Villard at the Space Telescope Science Institute Press Office, Baltimore, at: 410-338-4514 ( or Cheryl Gundy at 410-338-4707 for participation information.

Briefing participants:

- Adam Riess, astrophysicist, Space Telescope Science Institute and Johns Hopkins University, Baltimore
- Mario Livio, senior astrophysicist, Space Telescope Science Institute
- Louis-Gregory Strolger, astronomer, Western Kentucky University, Bowling Green, Ky.
- Sean Carroll, senior research associate, California Institute of Technology, Pasadena, Calif.
Audio of the event will be available on the Internet at: + NASA Newsaudio

For NASA TV streaming video, schedule and downlink information, visit: + NASA TV

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NASA Official: Brian Dunbar
Last Updated: November 16, 2006
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