NASA was watching another dying star when a new one in the same galaxy exploded
Pastor Dale Morgan
NASA was watching another dying star when a new one in the same galaxy
exploded*
* Story Highlights
* NASA was watching another dying star when a new one in the same
galaxy exploded
* Researcher: "A star exploded right before my eyes"
* Less than 1 percent of the stars in the universe will die in a
supernova
* Chances of simultaneous supernovae so close to each other around 1
in 10,000
WASHINGTON (AP) -- In a stroke of cosmic luck, astronomers for the first
time witnessed the start of one of the universe's most fiery events: the
end of a star's life as it exploded into a supernova.
Astronomers were observing SN 2007uy when they saw that SN 2008D had
begun to explode.
On January 9, astronomers used a NASA X-ray satellite to spy on a star
already well into its death throes, when another star in the same galaxy
started to explode. The outburst was 100 billion times brighter than
Earth's sun.
The scientists were able to get several ground-based telescopes to join
in the early viewing and the first results were published in Thursday's
issue of the journal Nature.
"A star exploded right before my eyes," lead author Alicia Soderberg, an
astrophysics researcher at Princeton University, said Wednesday in a
teleconference.
She likened it to "winning the astronomy lottery. We caught the whole
thing from start-to-finish on tape."
Another scientist, University of California at Berkeley astronomy
professor Alex Filippenko, called it a "very special moment because this
is the birth, in a sense, of the death of a star."
And what a death blast it is.
"As much energy is released in one second by the death of a star as by
all of the other stars you can see in the visible universe," Filippenko
said.
Less than 1 percent of the stars in the universe will die this way, in a
supernova, said Filippenko, who has written a separate paper awaiting
publication. Most stars, including our sun, will get stronger and then
slowly fade into white dwarfs, what Filippenko likes to call "retired
stars," which produce little energy.
The first explosion of this supernova can only be seen in the X-ray wave
length. It was spotted by NASA's Swift satellite, which looks at X-rays,
and happened to be focused on the right region, Soderberg said.
The blast was so bright it flooded the satellite's instrument, giving it
a picture akin to "pointing your digital camera at the sun," she said.
Soderberg said that by seeing it live in X-rays, astronomers on Earth
learned of the supernova about a month before they normally would.
The chances of two simultaneous supernovae explosions so close to each
other is maybe 1 in 10,000, Soderberg said. The odds of looking at them
at the right time with the right telescope are, well, astronomical.
Add to that the serendipity of the Berkeley team viewing the same region
with an optical light telescope. It took pictures of the star about
three hours before it exploded.
This new glimpse of a supernova seems to confirm decades-old theories on
how stars explode and die, not providing many surprises, scientists
said. That makes the findings "a cool thing," but not one that
fundamentally changes astrophysics, said University of California, Santa
Cruz astrophysicist Stan Woosley, who wasn't part of the research.
The galaxy with the dual explosions is a run-of-the-mill cluster of
stars, not too close and not too far from the Milky Way in cosmic terms,
Soderberg said.
The galaxy, NGC2770, is about 100 million light years away. One light
year is 5.9 trillion miles.
The star that exploded was only about 10 million years old. It was the
same size in diameter as the sun, but about 10 to 20 times more dense.
"The big stars live fast and die young," said Harvard astronomy
professor Robert Kirshner. "We don't know if they leave a beautiful corpse."
The death of this star went through stages, with the core getting
heavier in successive nuclear reactions and atomic particles being shed
out toward the cosmos, Filippenko said. It started out in its normal
life with hydrogen being converted to helium, which is what is happening
in our sun.
The helium then converts to oxygen and carbon, and into heavier and
heavier elements until it turns into iron.
That's when the star core becomes so heavy it collapses in on itself,
and the supernova starts with a shock wave of particles piercing through
the shell of the star, which is what the Soderberg team captured on x-rays.
People at home can simulate how this shockwave works, Filippenko said.
Take a basketball and a tennis ball, get about five feet above the
ground and rest the tennis ball on top of the basketball. Drop them
together and the tennis ball will soar on the bounce. The basketball is
the collapsing core and the tennis ball is the shockwave that was seen
by astronomers, he said.