Binary Star V Sagittae Will Explode In 2083, Researchers Predict

Binary star system V Sagittae (V Sge) is a rather unusual binary in the constellation Sagitta. Should astronomers’ prediction prove accurate and it does explode into a very bright nova in 2083, it will become one of the brightest stars in the night sky.

Unusual Binary

V Sge is a star system in a class called Cataclysmic Variables (CV), which consists of an ordinary star in orbit around a white dwarf star, with the normal star’s mass slowly falling into the white dwarf. V Sge is considered to be the most extreme among CVs, however, because it is a hundred times more luminous than other CVs, and its stellar wind can compare to that of massive stars' before their death. It is also rather unique because unlike the other CVs wherein the white dwarf is larger than its companion star, the companion star in V Sge is 3.9 times larger than the white dwarf.

Although V Sge was discovered in 1904, Harvard College Observatory actually provides a detailed history of V Sge from before its discovery thanks to now archived photos dating back to 1890. Through routine measures of those photos, astronomers recently found another interesting thing about V Sge, in that it has actually been brightening by a factor of 10X from 1890 until 2019.

Nova Explosion In 2083

According to the astronomers who presented their findings at the 235^th American Astronomical Society meeting in Hawaii, this is likely because the companion star is significantly more massive than the white dwarf that the system is in-spiraling rapidly, thereby forcing the mass transfer to rise exponentially.

“Previously, astronomers have studied V Sge, realizing that it is an unusual system with extreme properties,” astronomer Juhan Frank said. “However, no one had realized that the binary orbit was in-spiraling very fast.”

Based on their calculations, the astronomers predict the binary's final merger to happen between 2067 and 2099, or somewhere around 2083. During these final days of V Sgt's life, the entire mass of the companion star will fall into the white dwarf, causing a supermassive wind that will make it appear as bright as Sirius, the brightest star visible in the night sky, or even Venus.

The peak brightness of the explosive merger event will occur in a span of over one month, after which the binary will become just a single star with a white dwarf core.

For now, V Sge is barely visible in the night sky. The last time that a so-called “guest” star appeared brighter was in 1604 with the Kepler Supernova.

“Now people the world over can know that they will see a wondrous guest star shining as the brightest in the sky for a month or so, being pointed at by the Arrow just below Cygnus, the Swan,” Professor Emeritus Bradley E. Schaefer of Louisiana State University said.