Astronomers from the University of Cambridge, along with an international team of colleagues and amateur scientists, have discovered the first ever known binary star system in which one of the stars is completely eclipsed by the other.
The discovery, which is detailed in Friday’s edition of the journal Monthly Notices of the Royal Astronomical Society, centers around a type of two-star system called a Cataclysmic Variable, in which one super dense white dwarf star is cannibalizing gas from its companion.
This particular system is located approximately 730 light years from Earth in the constellation Draco, and was discovered by the ESA’s Gaia satellite in August 2014. Named Gaia14aae, the system was first spotted when it suddenly and drastically increased in brightness over the course of a single day, Dr. Heather Campbell of the Cambridge Institute of Astronomy said.
“Gaia14aae was discovered by the Gaia satellite when it suddenly became 10 times brighter in August 2014,” Dr. Campbell told redOrbit via email. “We caught it with Gaia because one star is eating material off the other which causes occasional outbursts or transient events.”
“Additional observations of the system were made by the Center for Backyard Astrophysics (CBA), a collaboration of amateur and professional astronomers, who took many short images of the system,” she added. “The CBA noticed a regular dip in the brightness of Gaia14aae, every 47 minutes, which they attributed to an eclipse of the white dwarf by its companion.”
Discovery could improve understanding of Ia supernovae
Using spectroscopy from the William Herschel Telescope in the Canary Islands, Dr. Campbell’s team discovered that while Gaia14aae contains large amounts of helium, it lacked hydrogen, the most comment element in the universe. The absence of this element allowed them to classify the new system as a very rare type of system known as an AM Canum Venaticorum (AM CVn).
An AM CVn, she explained, is a kind of Cataclysmic Variable system in which both stars have lost all of their hydrogen. This discovery is “especially exciting” because “it is the first known AM CVn system where one star totally eclipses the other,” she told redOrbit. “This means we will be able to measure their sizes and masses to a higher accuracy than any similar system.”
The study authors also said that this new type of system could lead to a new way to study ultra-bright supernova explosions, which is one of the primary tools used to measure the expansion of the universe. Dr. Campbell explained that AM CVn systems “could hold the key to one of the greatest mysteries in modern astrophysics: what causes Ia supernova explosions?”
Type Ia supernovae occur in binary systems, and is essential in the field of astrophysics because their extreme brightness allows researchers to use them to measure the accelerated expansion of the Universe, she said. In the case of Gaia14aae, it’s not known whether the two stars will collide and cause a supernova explosion, or if the white dwarf will completely devour its companion star before that can happen. However, studying Gaia14aae will lead to new insight into how this type of supernovae explode, which is essential for more accurate measurements of dark energy.
“Gaia14aae was one of the first discoveries from the Gaia satellite, which will be searching for transient objects for the next four or more years,” Dr. Campbell concluded. “So watch this space for many more exciting discoveries. We announce all the new discoveries on our website so that other astronomers and the public can help us gain more information from the ground on the new discoveries to try to understand what they are.”
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Feature Image: This is an artist’s impression of Gaia14aae. (Credit: Marisa Grove/Institute of Astronomy)
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