|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. |
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)
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 ( firstname.lastname@example.org or Cheryl Gundy at 410-338-4707 email@example.com for participation information.
- 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