NASA's Spitzer Finds Hints of Planet Birth Around Dead Star
NASA's Spitzer Space Telescope has uncovered new evidence that planets
might rise up out of a dead star's ashes.
The infrared telescope surveyed the scene around a pulsar, the remnant of
an exploded star, and found a surrounding disk made up of debris shot out
during the star's death throes. The dusty rubble in this disk might
ultimately stick together to form planets.
Image right: This artist's concept depicts a type of dead star called a pulsar and the surrounding disk of rubble discovered by NASA's Spitzer Space Telescope. Image credit: NASA/JPL-Caltech
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+ Related animation without audio (6.5Mb): This artist's animation depicts the explosive death of a massive star, followed by the creation of a disk made up of the star's ashes. + Full caption/high resolution for animation and image
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This is the first time scientists have detected planet-building materials
around a star that died in a fiery blast.
"We're amazed that the planet-formation process seems to be so universal,"
said Dr. Deepto Chakrabarty of the Massachusetts Institute of Technology in
Cambridge, principal investigator of the new research. "Pulsars emit a tremendous
amount of high energy radiation, yet within this harsh environment we have a disk
that looks a lot like those around young stars where planets are formed."
A paper on the Spitzer finding appears in the April 6 issue of Nature. Other authors
of the paper are lead author Zhongxiang Wang and co-author David Kaplan, both of
the Massachusetts Institute of Technology.
The finding also represents the missing piece in a puzzle that arose in 1992, when
Dr. Aleksander Wolszczan of Pennsylvania State University found three planets
circling a pulsar called PSR B1257+12. Those pulsar planets, two the size of Earth,
were the first planets of any type ever discovered outside our solar system. Astronomers
have since found indirect evidence the pulsar planets were born out of a dusty debris disk,
but nobody had directly detected this kind of disk until now.
The pulsar observed by Spitzer, named 4U 0142+61, is 13,000 light-years away in the
Cassiopeia constellation. It was once a large, bright star with a mass between 10 and
20 times that of our sun. The star probably survived for about 10 million years, until
it collapsed under its own weight about 100,000 years ago and blasted apart in a
Some of the debris, or "fallback," from that explosion eventually settled into a disk
orbiting the shrunken remains of the star, or pulsar. Spitzer was able to spot the warm
glow of the dusty disk with its heat-seeking infrared eyes. The disk orbits at a distance
of about 1 million miles and probably contains about 10 Earth-masses of material.
Pulsars are a class of supernova remnants, called neutron stars, which are incredibly
dense. They have masses about 1.4 times that of the sun squeezed into bodies only 10
miles wide. One teaspoon of a neutron star would weigh about 2 billion tons. Pulsar
4U 0142+61 is an X-ray pulsar, meaning that it spins and pulses with X-ray radiation.
Any planets around the stars that gave rise to pulsars would have been incinerated
when the stars blew up. The pulsar disk discovered by Spitzer might represent the
first step in the formation of a new, more exotic type of planetary system, similar
to the one found by Wolszczan in 1992.
"I find it very exciting to see direct evidence that the debris around a pulsar is
capable of forming itself into a disk. This might be the beginning of a second generation
of planets," Wolszczan said.
Pulsar planets would be bathed in intense radiation and would be quite different from
those in our solar system. "These planets must be among the least hospitable places in
the galaxy for the formation of life," said Dr. Charles Beichman, an astronomer at NASA's
Jet Propulsion Laboratory and the California Institute of Technology, both in Pasadena, Calif.
The Jet Propulsion Laboratory manages the Spitzer Space Telescope mission for NASA's
Science Mission Directorate, Washington. Science operations are conducted at the Spitzer
Science Center at Caltech. JPL is a division of Caltech. Spitzer's infrared array camera,
which made the pulsar observations, was built by NASA's Goddard Space Flight Center,
Greenbelt, Md. The instrument's principal investigator is Dr. Giovanni Fazio of the
Harvard-Smithsonian Center for Astrophysics.
For more information about Spitzer, visit:
Jet Propulsion Laboratory, Pasadena, Calif.
Erica Hupp/Grey Hautaluoma