Circling the Black Hole
The first frame shows a background sky highly distorted by the black hole in the center. The gravity of the black hole is so great that it actually deflects the background starlight. Large light bending effects cause the background sky to appear to move in unusual ways as you circle the black hole. Light paths […] The post Circling the Black Hole appeared first on NASA Science .
The first frame of today's Astronomy Picture of the Day showcases a background sky heavily distorted by a black hole at its center. Due to the black hole's immense gravity, it deflects the background starlight, causing large light bending effects that make the distant sky appear to move in unusual ways as the viewer circles the black hole.
Remarkably, even stars hidden behind the black hole can reach the observer, as the light paths are so curved that no part of the sky remains eclipsed. Meanwhile, light from distant stars falling towards the black hole appears blueshifted. The intense light bending also causes stars on the opposite side of the black hole to appear greatly magnified, revealing normally invisible stars.
As one watches closely, an invisible circular ring surrounds the black hole on either side of which stars rotate in the opposite direction. This ring is known as the Einstein ring, and stars do not cross through it. Stars approaching the exact opposite side of the black hole from the observer are seen with two bright images – one just outside the Einstein ring and another 180 degrees around the face of the black hole, just inside it.
These images appear to move at the highest angular speed. The post "Circling the Black Hole" from NASA Science is the first of its kind in the APOD archive.
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