Explosion on a star the size of Jupiter 10 times more powerful than ever under the sun

A stellar flare ten times more powerful than anything we see on our sun comes from an ultra-cold star of the same size as Jupiter.

The star is the coolest and the smallest to emit a rare super-white light, and by some definitions it may be too small to be considered a star.

The discovery, funded by the Science and Technology Facilities Council, is published in the Monthly Notices of the Royal Astronomical Society: Letters today's version of the disc (April 17) and highlights the question of how small a star can be and displays an ever-increasing activity in its atmosphere. Flares are thought to be caused by a sudden release of magnetic energy generated inside the star. The charged particles thus heat the plasma on the stellar surface, which releases large amounts of optical, UV and X-rays.

Lead author, James Jackman, Ph.D. student at the Department of Physics at the University of Warwick, said: "The activity of low-mass stars decreases as you head to lower and lower masses and we expect the chromosphere (a region of the star that supports flares) to become cooler or weaker. "The fact that we have observed this star of incredibly low mass, where the chromosphere should be almost at its lowest point, but we have a white light that indicates that a strong magnetic activity can still persist up to this level.

"It's just on the boundary between being a star and a brown dwarf, a subellar object of very low mass, any lower mass and it would certainly be a brown dwarf." By pushing this limit, we can see if these types of torches are limited to stars and if so, when does this activity stop? This result makes us a long way to answer these questions. "

The dwarf star L located at 250 light-years, named ULAS J224940.13-011236.9, represents only one-tenth of the radius of our own sun, almost the same size as Jupiter in our solar system. It was too weak for most telescopes to observe until the researchers, led by the University of Warwick, noticed the gigantic stellar explosion of its chromosphere at one time. optical survey of surrounding stars.

Using the Next Generation Transit Survey (NGTS) facility of the European Southern Observatory's Paranal Observatory, with additional data from Two Micron All Sky Survey (2MASS) surveys and Wide-field Infrared Survey Explorer (WISE), 146 nights.

The flare occurred on the night of August 13, 2017 and released an energy equivalent to 80 billion megatonnes of TNT, ten times more than the Carrington event in 1859, the largest energy event. observed on our sun. Solar flares occur regularly on our Sun, but if the Sun were superimposed like this star, Earth's communication and energy systems would be in danger of breaking down.

This is one of the largest eruptions ever seen on a L dwarf star, giving the star an appearance 10,000 times brighter than normal.

James adds: "According to other polls, we knew that this type of star existed and from previous work, this type of star could display incredible splinters. However, the resting star was too weak for our telescopes to see normally – we would not get enough light for the star to appear over the background above the sky. background of the sky. It is only when it ignites that it becomes bright enough that we can detect it with our telescopes. "

James Ph.D. Professor Peter Wheatley, Supervisor, said: "Our twelve NGTS telescopes are typically used to search planets around bright stars, so it's interesting that we can also use them to find giant explosions on Tiny and weak stars.It is especially nice to detect these outbreaks can help us understand the origin of life on the planets. "

The dwarves are among the lowest mass objects that could still be considered a star, lying in the transition region between stars and brown dwarves. Brown dwarfs are not massive enough to melt helium hydrogen as the stars do. Dwarves are also very cool compared to the most common main sequence stars, such as red dwarfs, and emit radiation mainly in the infrared, which can affect their ability to support the creation of life.

James adds, "The hottest stars will emit more in the optical spectrum, especially to the UV, because this star is cooler, about 2000 Kelvin, and most of its light is directed towards the infrared, it emits a burst of UV radiation that you would not normally see.

"To get chemical reactions on all the planets in orbit and to form the amino acids that are the basis of life, you would need a certain level of UV radiation.These stars do not normally have it because they emit mainly in But if they produce a big rocket like this, it could trigger some reactions. "

Professor Wheatley added, "It is amazing that such a star can produce such a powerful explosion, and this discovery will force us to think again about how small stars can store energy in magnetic fields. now look for giant star eruptions and push the boundaries of our understanding of stellar activity ".