In our Milky Way galaxy there is a double star system that behaves in an unusual way. This system, called AG Dragon, consists of two stars: a relatively cold giant and a hotter white dwarf – the remnants of a burnt star of small or medium size. These objects are located at a distance of 16,000 light years from Earth. Such a long distance makes it difficult to observe the stars of the system in detail, but scientists have long known some of its features.
These two stars are likely to interact with each other, and at the same time material flows from the surface of a larger, cold star to the surface of a compact, hot dwarf. Since the 1890s. This system demonstrates outbursts of activity with a period from 9 to 15 years – passing through an active period of several years in duration, during which the stars become brighter at certain wavelengths every year. Currently, the stars are in the active phase, and flashes on them were observed in April 2016, May 2017 and April 2018.
However, the current period of activity of these stars was very unusual, the researchers report. In the past, the active phase of this system included a couple of “cold” flashes, during which the temperature of the white dwarf fell, and the following hot flashes, during which the temperature of the star increased. Cold flashes were always brighter than hot.
The cause of cold flashes, researchers believe the expansion of the white dwarf, accompanied by its cooling. The cause of hot flashes is still unclear.
However, the current cycle is unusual. It began only 7 years after the last small flash and consists only of bright, hot flashes.
A possible explanation for the origin of the flares observed on this star pair may be that the white dwarf’s gravity captures the material of the larger star and forms an unstable accretion disk, which “explodes” from time to time when receiving too large portions of the material, the authors note. The cause of the recent anomalous outbursts of a double star at this stage of the study is difficult for scientists to name.
Two stars in our galaxy behaves mysteriously
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