 |
| Discovering
a Supernova |
Using a search technique that enables
scientists to see violent explosions
of dying stars "on demand," Saul Perlmutter
of Lawrence Berkeley National Laboratory
led a team to the surprising discovery
that the expansion of the universe
is accelerating, and thus is likely
to continue doing so forever. The
discovery was based on the identification
and measurement during the 1990s of
the most distant supernovas ever observed.
Observations of rare type Ia supernovas—astronomical
"standard candles" that all have the
same intrinsic brightness—placed
them much farther away than would
be expected based on standard analyses
of their emitted light. By comparing
the distance to these exploding stars
with the distance of their home galaxies,
researchers calculated how fast the
universe was expanding at different
times in history. To ensure that supernovas
were seen during limited telescope
time, the team devised a strategy
of imaging patches of sky just after
a new moon, when the sky is dark,
and then again three weeks later when
supernovas show up as bright points
of light. The discovery was selected
by the journal Science as the top
breakthrough of 1998.
Scientific Impact:
This work overturned the common assumption
that the expansion of the universe
was slowing down because of gravity.
The results also provided strong evidence
of a mysterious, self-repelling property
of empty space—the cosmological
constant first proposed by Albert
Einstein—which may represent
much of the total mass-energy density
of the universe.
Social Impact: SOCIAL
IMPACT: These findings raise profound
questions about the ultimate fate
of the universe and the Earth, with
the promise of as-yet-unimagined impacts
on human society.
Reference: S. Perlmutter
et al. (1998), presentation at the
January 1998 Meeting of the American
Astronomical Society, Washington,
D.C., LBL Report Number LBL-42230;
referenced in B.A.A.S., Volume 29,
page 1351 (1997); astro-ph/9812473;
S. Perlmutter et al., Astrophysical
Journal, 517: 565-586 (1999);
astro-ph/9812133.
URL:
http://www.supernova.lbl.gov/
Technical Contact:
Dr. Saul Perlmutter, sperlmutter@lbl.gov
Press Contact: Jeff
Sherwood, DOE Office of Public Affairs,
202-586-5806
SC-Funding Office:
Office of High Energy and Nuclear
Physics |
