V838 Monocerotis. You might not remember the name, or even be able to pronounce it, but you’ve seen the pictures. The Hubble Space Telescope first captured images of this amazing star erupting material in 2002, and then photographed it again in subsequent years. A huge cloud of gas and dust, light-years across, is being illuminated before our eyes. But what caused the outburst that set off this explosion? One team of astronomers think we might be looking at the violent deaths of V838 Monocerotis’ planets as they’re consumed.
V838 Monocerotis was thought to be a fairly normal star, but then it flared up in 2002, briefly becoming one of the brightest stars in the galaxy; it blazed 600,000 times more brightly than our own Sun. As the flash of radiation expanded away from the central star, it illuminated a surrounding halo of material that had been ejected over the course of many years. Even more puzzling, V838 Monocerotis flared up three times in rapid succession.
Astronomers have been trying to puzzle out what could possibly make V838 Monocerotis blaze with such ferocity three separate times and then go quiet again. They’ve come up with a range of ideas. Perhaps a neutron star or white dwarf flared up, while inside a red giant star. Or maybe a binary pair of stars smashed together releasing a tremendous amount of energy.
But an international team of astronomers from the USA, Belgium and Israel report in a new paper that a “planet capture model” makes the most sense. In other words, the trio of blasts occurred as V838 Monocerotis consumed three Jupiter-sized planets.
At some point in the recent past, the first planet entered V838 Monocerotis’ outer envelope. Inside the star’s atmosphere, it was slowed down by the increased density of material, and began to quickly spiral inward. As it got closer to the stellar core, it experienced temperatures above 100,000 Kelvin.
Since Jupiter-class planets have large quantities of deuterium (stellar fuel), but never get massive enough to use it up through fusion, the planet could have delivered a jolt of fresh fuel to the stellar core, and caused the first massive explosion detected by astronomers.
As V838 Monocerotis flared up from consuming its first planet, its stellar envelope expanded, and it gobbling up the other two planets as well, leading to the additional flares.
The team of astronomers calculated that the amount of energy released by a star consuming three Jupiter-class planets nicely matches the observations made by Hubble and other observatories.