What happens when distant worlds collide

Eric Mamajek: In astronomy, we still have mysteries. We still have objects we run into that we don’t quite understand what they are, or how they formed, or how they’re evolving.

That’s astronomer Eric Mamajek of the Harvard-Smithsonian Center for Astrophysics, talking about what might be a possible collision between two distant planets.

Eric Mamajek: We’re not actually seeing the impact. We think what we’re seeing is the long-lived period afterwards where the object cools down.

This object is known as 2M1207B. It’s 170 light years from Earth and appears nearly twice as hot as expected for its age. EarthSky asked Mamajek the obvious question: how hot is it?

Eric Mamajek: Well, if you were on the planet, you’d be instantly vaporized. The objects we’re envisioning that could have produced this were gas giant planets. So something like a Saturn, and something like a Uranus and Neptune.

In other words, imagine if the planets Saturn and Neptune were to crash into each other. It sounds far out, but Mamajek said Earth’s moon formed after Earth collided with a body half the size of Mars.

Eric Mamajek: Since we can’t go back in time to our own solar system, we would like to observe other planetary systems to see if we can see glimpses of these processes going on on other stars. So it’d be wonderful if we could actually get visual confirmation that protoplanets are colliding and combining and accreting and forming into bigger planets. The signature of this we may be able to see around other stars. This may be the first object where that’s true.

Our thanks to:
Eric Mamajek
Harvard-Smithsonian Center for Astrophysics

September 10, 2008

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