Synopsis: Tidal Disruption of a Star

Theorists suggest that the weeks-long flare measured last year from a distant galaxy was probably beamed by a jet of material aligned with the rotational axis of a mammoth black hole.
Synopsis figure
NASA/Goddard Space Flight Center/Swift

The cores of most galaxies are thought to harbor black holes with masses of a million or more suns. But many remain unseen until an unlucky star passes too close and is pulled apart by tidal forces. The stellar debris gathers into a disk and spirals towards the black hole in the center. As it does, it may form a jet of material that beams high-energy light like a flashlight. Last spring, the Swift satellite measured a flare of x rays and gamma rays from a distant galaxy that has the hallmarks of such a jet that happens to point right at us.

Long-lived jets may explain many bright astronomical objects, such as quasars, but astrophysicists still have much to learn about how the jets form. In Physical Review Letters, Nicholas Stone and Abraham Loeb, both at Harvard University, argue that last year’s flare gives an important clue. The tidal disruption should have quickly formed a disk in the plane of the original star’s motion, which in general will not be perpendicular to the black hole’s rotation axis. Stone and Loeb calculate that the dragging of the relativistic frame by the mass of the rotating black hole will cause the disk to precess like a wobbling top. If the jet direction were determined by the disk, it would have quickly pointed away from us. Instead, the flare lasted more than two weeks, suggesting that the jet was directed along the unchanging axis of rotation for the black hole. – Don Monroe


Features

More Features »

Announcements

More Announcements »

Subject Areas

Astrophysics

Previous Synopsis

Next Synopsis

Astrophysics

And Then There Was One

Read More »

Related Articles

Viewpoint: New Clues as to Why Boyajian’s Star is Dimming
Statistical Physics

Viewpoint: New Clues as to Why Boyajian’s Star is Dimming

A statistical analysis links a star’s mysterious brightness fluctuations to internal nonequilibrium phenomena, rather than structures orbiting around the star. Read More »

Viewpoint: Searching for Baby Planets in a Star’s Dusty Rings
Astrophysics

Viewpoint: Searching for Baby Planets in a Star’s Dusty Rings

Images of gaps in the dust and gas around a young star provide the best evidence to date that these gaps host newly formed planets. Read More »

Synopsis: Sharper Vision for Infrared Telescopes
Optics

Synopsis: Sharper Vision for Infrared Telescopes

Converting infrared light to visible light might boost the sensitivity of infrared telescope arrays. Read More »

More Articles