Asteroid Smashup Observed By Spitzer Could Result In Planet Formation

Chuck Bednar for – Your Universe Online
An eruption of dust around a young solar-analog star discovered using the Spitzer Space Telescope could be the type of massive collision between asteroids that ultimately result in the formation of planets, astronomers report in Thursday’s online edition of the journal Science.
Scientists began tracking the star in question, identified as NGC 2547-ID8, after it first surged with a large amount of fresh dust between August 2012 and January 2013. While Spitzer has been used to observe the aftermath of suspected asteroid smashups before, NASA officials explained that this new research marks the first time scientists have successfully collected data both before and after planetary system collisions.
In their study, lead author and University of Arizona graduate student Huan Meng and his colleagues said that they detected “a debris-producing impact in the terrestrial planet zone” as it happened around the 35 million year old star. They went on to explain that there was a “substantial brightening of the debris disk at a wavelength of 3 to 5 micrometers,” which was followed by decay over the course of a year with “quasi-periodic” disk flux modulations.
Meng and experts from the California Institute of Technology (Caltech), the University of Tokyo and several other institutions explained that this type of behavior was “consistent with the occurrence of a violent impact that produced vapor out of which a thick cloud of silicate spherules condensed that were then ground into dust by collisions,” and suggest that their observations offer a sneak-peak into the process of forming rocky planets such as Earth.
Rocky planets, the US space agency explains, start out as dusty material that orbit young stars. This material clumps together, forming asteroids that eventually collide with one another. In many cases, those asteroids are destroyed, but in some instances they actually grow over time and become proto-planets. After approximately 100 million years, they mature into full-grown terrestrial planets, similar to how our moon is believed to have formed as the result of a giant impact between proto-Earth and another object roughly the same size as Mars.
As part of their research, the astronomers focused Spitzer’s heat-seeking infrared instruments on NGC 2547-ID8, which is a star that lies roughly 1,200 light-years away in the Vela constellation and is roughly 35 million years old. While previous observations had recorded variations in the amount of dust around the star, suggesting the presence of ongoing asteroid collisions, Meng’s team was hoping to view an even larger, potentially planet-forming impact.
“Beginning in May 2012, the telescope began watching the star, sometimes daily,” NASA said. “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,” co-author Kate Su, also of the University of Arizona, said in a statement. “Spitzer is the best telescope for monitoring stars regularly and precisely for small changes in infrared light over months and even years.”
Currently, there is an extremely thick cloud of dusty debris orbiting NGC 2547-ID8 in the zone where rocky planets typically form, and the scientists observations indicate that the infrared signal from this cloud changes based on how much of it is visible from Earth. When it is facing us, they said that more of its surface area is exposed and the signal becomes stronger, but when the head or tail is visible, 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,” NASA explained, with co-author George Rieke noting that he and his colleagues had “a unique chance” to study the process of rocky planet formation taking place in near-real time.
“The team is continuing to keep an eye on the star with Spitzer,” the US space agency added. “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.”
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