Image of the Day: Runaway Black Hole at Plane of the Milky Way




The ESA/NASA impression shows an oblique view of our Milky Way galaxy. The black-hole system GRO J1655-40 is streaking through space at a rate of 400 000 kilometres per hour – 4 times faster than the average velocity of the stars in the galactic neighborhood. The yellow star is our Sun. The black hole was formed in the disk at a distance greater than 3 kpc from the Galactic centre and must have been shot to such an eccentric orbit by the supernova explosion of the progenitor star. The runaway linear momentum and kinetic energy of this black hole binary are comparable to those of solitary neutron stars and millisecond pulsars. GRO J1655-40 is the first black hole for which there is evidence for a runaway motion imparted by a natal kick in a supernova explosion.

GRO J1655-40 is one of at least two galactic "microquasars" that may provide a link between the supermassive black holes generally believed to power extragalactic quasars and more local accreting black hole systems. For comparison, the Sun and other nearby stars have typical speeds on the order of 20 km/s relative to the average velocity of stars moving with the galactic disk's rotation in the solar neighborhood, which supports the idea that the black hole formed from the collapse of the core of a massive star. As the core collapsed, its outer layers exploded as a supernova leaving the remnant system moving through the galaxy with unusually high speed.

The Spitzer Space Telescope's infrared view of the plane of our Milky Way Galaxy below is made from more than 800,000 frames of data pieced together in an enormous mosaic of the galactic plane – the most detailed infrared picture of our galaxy ever made.




The Daily Galaxy via

Image credit: European Space Agency, NASA and Felix Mirabel (the French Atomic Energy Commission & the Institute for Astronomy and Space Physics/Conicet of Argentina)


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