photon sphere of a black hole, half of the sky would appear completely black, half of the sky would appear unusually bright, and the back of your head would appear across the middle. The above computer-animated video depicts this view from the photon sphere. The reason that the lower region, as shown, appears black is because all light paths from this dark region comes up from the black hole -- which classically emits no light. The upper half of the sky now appears unusually bright, blueshifted, and shows increasingly many complete sky images increasingly close to the dark-light divide across the middle. That dark-light divide is the photon sphere -- your location -- and since photons can do circles there, light from the back of your head can circle the black hole and come to your eye. No place on the sky is hidden from you -- stars that would normally pass behind the black hole now appear to zip quickly around an Einstein ring, a ring that appears above as a horizontal line about a quarter of the way down from the video top. The above video is part of a sequence of videos visually exploring the space near a black hole's event horizon. (Disclosure: Video creator Robert Nemiroff is an editor for APOD.)
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NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture Of the Day
Publications with keywords: black hole
Publications with words: black hole
- GW190521: Unexpected Black Holes Collide
- APOD: 2020 August 25 Á Visualization: A Black Hole Accretion Disk
- A Black Hole Disrupts a Passing Star
- An Extreme Black Hole Outburst
- Black Hole Safety Video
- Unusual Signal Suggests Neutron Star Destroyed by Black Hole
- Animation: Spiral Disk around a Black Hole