Binary stars are racing through the galaxy at high speed, moving back and forth between the galactic center and the halo every 400 million years.

This is an artist's impression of the binary star VVV 1256-62AB, located about 246 light-years away. VVV 1256-62AB consists of a white dwarf star VVV 1256-62A in the background left and a subdwarf star VVV 1256-62B in the foreground right. They are separated by about 1,400 AU and orbit each other every 60,000 years.

The stars in the Milky Way galaxy move in their own orbits, but this binary star's orbit is unique. According to a research team led by Zinghua Zhang of Nanjing University, the Milky Way approaches its center by only about 3,000 light-years every 400 million years, but its farthest distance is about 100,000 light-years.(*A low-density region surrounding a spherical galaxy)It is currently moving away from the center at a speed of 406 km/s.

[▲ فيديو يوضح حركة النجم الثنائي “VVV 1256-62AB” على مدى الـ 2 مليار سنة الماضية (سماوي) والـ 2 مليار سنة القادمة (حمراء). يشير النجم إلى الموقع الحالي للشمس.]
(Credit: Roberto Rady, Zhenghua Zhang, MNRAS)

Furthermore, while the surface temperature of a newborn white dwarf is 100,000 degrees Celsius, the surface temperature of VVV 1256-62A has dropped to about 4,160 degrees Celsius, which is lower than that of the Sun. The binary star is very old, about 10.5 billion years old, and it is estimated that about 8.5 billion years have passed since VVV 1256-62A became a white dwarf.

Studying VVV 1256-62AB is expected to provide further insight into the Milky Way as a whole and test models of stellar evolution.

source

• Nanjing University – 'Waltz' in the Milky Way: First Ultra-Cool Dwarf Accompanied by White Dwarf – Nanjing University
• European Space Agency – Gaia discovers an interesting duo in the Milky Way's halo: an ultra-cool subdwarf with a companion white dwarf
• Zhang et al. – Very low-mass primitive stars and brown dwarfs – VIII. The first L-age brown dwarf, a large-scale companion to a halo white dwarf (Monthly Notices of the Royal Astronomical Society)

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