Milky Way’s smallest black holes ‘don’t exist’

Monday, November 22, 2010

LONDON - A new study has revealed that black holes a few times the mass of the sun may not exist to begin with.

Stars that are eight or more times the mass of the sun explode as supernovae at the end of their lives. If the core left behind weighs less than two or three suns, it will turn into a neutron star. If it weighs more, it will become a black hole.

But there is a glaring lack of black holes observed at the lightest end of the spectrum, said Feryal Ozel of the University of Arizona in Tucson, reports New Scientist.

Ozel and colleagues studied 16 systems in the Milky Way that contain a black hole and a stellar partner, and found that none of these black holes had a mass between two and five times that of the sun.

This can’t be explained by simple observational constraints, said the team.

“These black holes really seem not to exist,” said Ozel.

If the results are confirmed, they could give new insights into how stars collapse and explode, said Chris Fryer of the Los Alamos National Laboratory in New Mexico.

Larger stars are thought to explode with less energy than smaller ones, said Fryer. That means lower-mass stars that go on to form neutron stars would blast more of their outer layers away than higher-mass stars that become black holes.

The extra material the higher-mass stars hold onto could then fall into the black holes, bulking them up. This could explain the dearth of the puniest black holes, he said.

The findings would appear in the Astrophysical Journal. (ANI)

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