White Dwarf Star Magnifies Another Star’s Brightness: Einstein Thought It Couldn’t Be Observed
Telescope Gives Astronomers Ability To Observe Cosmic Magnifying Glass
Astronomers recently observed a white dwarf acting as a magnifying glass, giving them a unique view of the sun-like star it is orbiting. This 'self-lensing' phenomenon was predicted over 40 years ago by Swiss astronomer André Maeder, but hasn't been discovered until now.
Ethan Kruse and Eric Agol are the physicists from the University of Washington in Seattle Using data that used data from NASA's Kepler spacecraft, and saw the large star's brightness increase by 0.1 percent every 88 days. The increase occurred when the white dwarf passed in front of the star and lasted for 5 hours from earth's perspective. Kruse and Agol published their findings in Science.
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"It was not till Kepler was launched that we had a telescope capable of finding such tiny changes," says Kruse.
White dwarves, such as the one that was recently observed, are made from the remnants of stars and lock into mutual orbit with a sun-like star. With normal orbiting, the white dwarf with periodically eclipse between the sun-like star and the earth, which gave Kruse and Agol the ability to observe the magnifying episodes. The gravitational lensing magnifies the star's light ever so slightly, but enough to cause a noticeable difference and will allow researchers to better understand the behavior of white dwarfs.
The self-lensing that occurs when a foreground star magnifies a background star as it passes in front, magnifies light only momentarily and in such miniscule increments it's difficult to spot. The white dwarf makes it easier for researchers to observe because it has the same mass of a star but is compressed to roughly the same size as planet Earth.
The idea of gravitational lensing was first predicted by Albert Einstein in 1915, however he believed it would not be possible to actually observe the lens effect, according to Einstein-Online. In fact, when he was asked to publish the theory in Science magazine, he had declined at first, stating that the phenomenon was unobservable.
Finally physicists have caught a glimpse of 0.1 percent brightness increase, and have named the binary system KOI-3278. KOI stands for "Kepler Object of Interest" because the Kepler telescope gave them the power to observe such small increments of change. The star that the white dwarf magnifies is a yellow star has almost the same mass as the sun, making it nearly identical. Eventually the star will burn out and leave another white dwarf behind, but the Kepler's job is not done. Astronomers believe the Kepler telescope will be able to observe many more models of white dwarf gravitational lensing, which will lead to a better understanding of past and future binary systems.
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