BATON ROUGE – Louisiana State University Astronomers have estimated approximately when one of the Milky Way's most unique stars will enhance in brightness and explode, to become the galaxy's brightest star.

Brad Schaefer announced V Sagittae "merger burst" at the Super Bowl of Astronomy #AAS235 @AAS_Press Read more https://t.co/CI7Bf4uftP @LSUResearch @lsuscience @LSUNews @astrotapBR @dcastelvecchi #YourQuestionNext pic.twitter.com/pw7KVDzpWV

— LSU Phys & Astro (@LSUphysastro) January 6, 2020

The star is known as V Sagittae V Sge, and finds its home in the constellation Sagitta. 

At the moment, V Sge is barely visible, even in mid-sized telescopes. 

But LSU experts say this will likely change sometime between the years 2069 and 2099 when the star will explode and become as radiant as Sirius, the brightest star visible in the night sky. 

During this erruption, V Sge will become the most luminous star in the Milky Way.

This prediction was presented for the first time at the 235th American Astronomical Society meeting in Honolulu, by astronomers Bradley E. Schaefer, Juhan Frank and Manos Chatzopoulos, with the LSU Department of Physics & Astronomy.

“We now have a strong prediction for the future of V Sge,” Schaefer said. “Over the next few decades, the star will brighten rapidly. Around the year 2083, its accretion rate will rise catastrophically, spilling mass at incredibly high rates onto the white dwarf, with this material blazing away. In the final days of this death-spiral, all of the mass from the companion star will fall onto the white dwarf, creating a super-massive wind from the merging star, appearing as bright as Sirius, possibly even as bright as Venus.”

One of the factors that makes V Sge 'special' is its mass, which is about 100 times more luminous than other stars of its type. Adding the to star's unique nature are its impressive stellar winds, which are a result of its mass. 

V Sge also has an important neighbor, a white dwarf star that it orbits. Typically, stars that orbit white dwarfs have less mass than their powerful neighbors. But in this case, V Sge is the more massive of the two and this means V Sge's mass is slowly falling onto the white dwarf.  

“In all other known CVs the white dwarf is more massive than the orbiting normal star, so V Sge is utterly unique,” said Schaefer.

Experts recently realized that V Sge has been systematically brightening by a factor of 10X, 2.5 magnitudes, from the early 1890s up until the last decade. 

This unprecedented behavior was confirmed with archival data collected from the database of the American Association of Variable Star Observers, AAVSO, showing V Sge brightening by nearly a factor of 10X, 2.4 magnitudes, from 1907 until the last few years.

“V Sge is exponentially gaining luminosity with a doubling time scale of 89 years,” said Frank. “This brightening can only result with the rate of mass falling off the normal companion star increasing exponentially, ultimately because the binary orbit is in-spiraling rapidly.”

Schaefer says sometime during the aforementioned years, most likely in 2083, V Sge will appear startlingly bright in the night sky.

He says this event will be substantially brighter than the all-time brightest known nova (at -0.5), which occurred just over a century ago.

The last time any 'guest star' appeared brighter was Kepler's Supernova in the year 1604.