This artist’s concept shows the immediate aftermath
of a large asteroid impact around NGC 2547-ID8, a 35-million-year-old sun-like
star. NASA's Spitzer Space Telescope witnessed a giant surge in dust around the
star, likely the result of two asteroids colliding.
Image Credit:
NASA/JPL-Caltech
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Astronomers were surprised to see these data from
NASA's Spitzer Space Telescope in January 2013, showing a huge eruption of dust
around a star called NGC 2547-ID8. In this plot, infrared brightness is
represented on the vertical axis, and time on the horizontal
axis.
Image Credit:
NASA/JPL-Caltech/University of
Arizona
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NASA's Spitzer Space Telescope has spotted an eruption of dust around a young
star, possibly the result of a smashup between large asteroids. This type of
collision can eventually lead to the formation of planets.
Scientists had been regularly tracking the star, called NGC 2547-ID8, when it
surged with a huge amount of fresh dust between August 2012 and January
2013.
"We think two big asteroids crashed into each other, creating a huge cloud of
grains the size of very fine sand, which are now smashing themselves into
smithereens and slowly leaking away from the star," said lead author and
graduate student Huan Meng of the University of Arizona, Tucson.
While dusty aftermaths of suspected asteroid collisions have been observed by
Spitzer before, this is the first time scientists have collected data before and
after a planetary system smashup. The viewing offers a glimpse into the violent
process of making rocky planets like ours.
Rocky planets begin life as dusty material circling around young stars. The
material clumps together to form asteroids that ram into each other. Although
the asteroids often are destroyed, some grow over time and transform into
proto-planets. After about 100 million years, the objects mature into
full-grown, terrestrial planets. Our moon is thought to have formed from a giant
impact between proto-Earth and a Mars-size object.
In the new study, Spitzer set its heat-seeking infrared eyes on the dusty
star NGC 2547-ID8, which is about 35 million years old and lies 1,200
light-years away in the Vela constellation. Previous observations had already
recorded variations in the amount of dust around the star, hinting at possible
ongoing asteroid collisions. In hope of witnessing an even larger impact, which
is a key step in the birth of a terrestrial planet, the astronomers turned to
Spitzer to observe the star regularly. Beginning in May 2012, the telescope
began watching the star, sometimes daily.
A dramatic change in the star came during a time when Spitzer had to point
away from NGC 2547-ID8 because our sun was in the way. When Spitzer started
observing the star again five months later, the team was shocked by the data
they received.
"We not only witnessed what appears to be the wreckage of a huge smashup, but
have been able to track how it is changing -- the signal is fading as the cloud
destroys itself by grinding its grains down so they escape from the star," said
Kate Su of the University of Arizona and co-author on the study. "Spitzer is the
best telescope for monitoring stars regularly and precisely for small changes in
infrared light over months and even years."
A very thick cloud of dusty debris now orbits the star in the zone where
rocky planets form. As the scientists observe the star system, the infrared
signal from this cloud varies based on what is visible from Earth. For example,
when the elongated cloud is facing us, more of its surface area is exposed and
the signal is greater. When the head or the tail of the cloud is in view, less
infrared light is observed. By studying the infrared oscillations, the team is
gathering first-of-its-kind data on the detailed process and outcome of
collisions that create rocky planets like Earth.
"We are watching rocky planet formation happen right in front of us," said
George Rieke, a University of Arizona co-author of the new study. "This is a
unique chance to study this process in near real-time."
The team is continuing to keep an eye on the star with Spitzer. They will see
how long the elevated dust levels persist, which will help them calculate how
often such events happen around this and other stars, and they might see another
smashup while Spitzer looks on.
The results of this study are posted online Thursday in the journal
Science.
NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, manages the
Spitzer Space Telescope mission for NASA's Science Mission Directorate in
Washington. Science operations are conducted at the Spitzer Science Center at
the California Institute of Technology in Pasadena. Spacecraft operations are
based at Lockheed Martin Space Systems Company in Littleton, Colorado. Data are
archived at the Infrared Science Archive housed at the Infrared Processing and
Analysis Center at Caltech. Caltech manages JPL for NASA.
For more information about Spitzer, visit:
NASA
Guillermo Gonalo Sánchez Achutegui
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