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NASA Astronomy Picture of the Day

🌌 NASA Astronomy Picture of the Day

Black Holes Signature From Advective Disks Research Credit:

Date: 1997-01-15

Black Holes Signature From Advective Disks
Research Credit:

View HD Image

Explanation:

What does a black hole look like? If alone,
a black hole
would indeed appear
quite black, but many black hole candidates are part of binary star systems.
So how does a black hole binary system
look different from a neutron star binary system?
The above drawings indicate it
is difficult to tell! Recent theoretical work,
however, has provided a new way to tell them apart: advective accretion flows (ADAFs).
A black hole system so equipped
would appear much darker than a similar neutron star
system. The difference is caused by the hot gas from the ADAF disk
falling through the event horizon
of the black hole and disappearing - gas that would have emitted
much light were the central object only a neutron star. Recent observations
of the soft X-ray transient
V404 Cyg
has yielded a spectrum
much like an ADAF onto a black hole
- and perhaps brighter than allowable from an ADAF onto a neutron
star.