 Lone
Black Hole Passes in Front of Star
[Left]
Two images of a crowded starfield as seen through a ground-based
telescope show the subtle brightening of a star due to the effect
of gravitational microlensing, where an invisible but massive foreground
object passes in front of the star and amplifies its light. The
dark lensing object is estimated to be a six-solar-mass black hole
that is drifting alone among the stars.
Credit: NOAO, Cerro Tololo Inter-American Observatory
[Right]
A NASA Hubble Space Telescope image of the same field clearly resolves
the lensed star and yields its true brightness. The Hubble observation
was needed because the ground-based images do not tell how bright
the lensed star actually was before (or after) it was lensed. The
star fields where microlensing events are observed are so crowded
with stars that the lensed star images are often blended together
with images of unlensed stars. But with the Hubble images, astronomers
can identify the lensed star and determine its normal brightness.
The Hubble images were taken on June 15, 1999.
Credit: NASA
and Dave Bennett (University of Notre Dame, Indiana)
|
Lone
Black Hole Passes in Front of Star
