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What would occur if one of the stars in a binary star system,went supernova?

Date: Tue Sep 22 19:41:58 1998
Posted by Mark Hosang
Grade level: other
School: Braintree High School
City: Braintree State/Province: Mass.
Country: USA

Message:

If one of the stars goes supernova, and the other has a higher density. Would the star with the greater density become the core of the supernova, be propelled into space from the explosion, or would it be absorbed?

Also would the supernova star continue to follow it orignal orbit, or would it become the center of the system, just revolving?


When most people think of a supernova (SN), they picture a single massive star exploding. But there are two main types of supernovae; the other type is a much older star that was once like the Sun, but has used up all its nuclear fuel. The remaining star is called a white dwarf, because it is usually hot and very small. If this white dwarf is a member of a binary system, it is possible, if the circumstances are just right, for that dwarf to actually strip matter off its companion. If enough matter gets piled up on top of the white dwarf, it can explode catastrophically, tearing itself to bits in an enormous explosion. So that kind of SN needs to be in a binary system! The first type can be a binary, but it isn't necessary. In both cases, you sometimes get a remnant left over, a neutron star or a black hole. These mass far less than the original star.

What happens next depends mostly on how much mass is lost from the star that blew up. The way the physics works, if the supernova expels more than half the total mass of both stars combined, the two stars will fly apart. For example, let's say the star that blows up masses 10 times the Sun's mass, and the companion masses twice the Sun. The total mass of the system is then 12 solar masses. If the star that explodes loses more than 6 solar masses, the two stars will fly apart. Anything less and they stay together, though the orbits get pretty disturbed, as you can imagine.

It may be possible for the violent event to disrupt the companion star, but only if it is very close. The exact details of such a system are pretty hard to work out. In all the supernova events we have seen, no one has ever directly seen a companion star to the star that exploded. We think that they exist, because most stars in the Galaxy are actually part of multiple systems, and from the shape of the exotic expanding debris clouds from supernova we infer the existence of a companion. Also, we have detected black holes and neutron stars that orbit "normal" stars; and since we know black holes and neutron stars form in supernova events, the other star must have been there when it happened. But we have never directly seen one to the best of my knowledge.

If you'd like to know more about supernovae, I have info on my own web page that can get you started.



©2008 Phil Plait. All Rights Reserved.

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