Tonight's Sky
Sun
Sun
Moon
Moon
Mercury
Mercury
Venus
Venus
Mars
Mars
Jupiter
Jupiter
Saturn
Saturn

Tonight's Sky — Change location

OR

Searching...

Tonight's Sky — Select location

Tonight's Sky — Enter coordinates

° '
° '

I was taught that the gravity of a black hole is so great that nothing, not even light, can escape. But I frequently see pictures of dual energy jets emanating from a black hole. How is this possible?

Eric Peters, Anderson, Indiana
January 2010 black hole jets
Gravity is so strong at and within the event horizon of a black hole that nothing, not even light, can escape. Just beyond the event horizon, however, the gravity, while hugely strong, is not overwhelming. That is the site of interesting, energetic, and observable commotion. As matter flows toward the black hole, often in a swirling disk of matter called an accretion disk, energy can be released. The jets arise from the highly energetic region just beyond the edge of the black hole, not from the black hole itself.

Within a particular orbit, called the "innermost stable circular orbit" (ISCO), matter tends to plunge toward the event horizon and radiate little, even though it is not yet "over the horizon." The ISCO is a few times larger than the event horizon. At the ISCO, matter orbits at nearly the speed of light, creating heat and generating huge magnetic fields. Observations, basic physics, and sophisticated models show that this combination probably gives rise to the jets observed from both stellar-mass black holes in binary star systems (where the companion star provides the mass to power the process) and supermassive black holes in galactic centers (where galactic gas and stars power the process). — J. Craig Wheeler, University of Texas at Austin



0

JOIN THE DISCUSSION

Read and share your comments on this article
Comment on this article
Want to leave a comment?
Only registered members of Astronomy.com are allowed to comment on this article. Registration is FREE and only takes a couple minutes.

Login or Register now.
0 comments
ADVERTISEMENT

FREE EMAIL NEWSLETTER

Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter. View our Privacy Policy.

ADVERTISEMENT
ADVERTISEMENT
Apollo_RightRail

Click here to receive a FREE e-Guide exclusively from Astronomy magazine.

Find us on Facebook