Brown dwarfs are often referred to as “failed stars”; however, astronomers have discovered a 23-million-year-old dwarf that flashes brighter than the Sun’s most powerful flares. The research team from the University of Delaware, led by John Gizis, a professor in the Department of Physics and Astronomy, discovered the “ultra-cool” brown dwarf known as 2MASS 0335+23.
The brown dwarf has a temperature of only 4400°F, and can generate flares stronger than the Sun’s, Gizis explained in a statement:
“This brown dwarf is very young by star standards — only 23 million years old.
“It has lots of flares that are as hot as or hotter than the flares coming off full-fledged stars. This shows that the warmer brown dwarfs can generate flares from magnetic field energy just like stars.
“Our work shows, however, that colder brown dwarfs cannot generate flares even though they also have magnetic fields.”
Brown dwarfs begin life the same way as stars (from collapsing clouds of gas and dust). However, they don’t get large and hot enough for hydrogen and helium to fuse at their core. This process generates the nuclear reactions needed to keep a star burning bright for millions and billions of years.
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The astronomers studied thousands of images from the NASA’s Kepler space telescope, searching for any changes in the dwarf brightness. What the researchers found was the brown dwarf would become twice as bright for two to four minutes. This continued a dozen times over a 3-month period. Gizis explained that:
“These flares are very powerful — stronger than the sun’s. They show what the sun could do when it was younger. It’s like its acne is going away.”
The brown dwarf is part of the Beta Pictoris moving group, which is a group of stars that were born at the same time, and are all moving parallel in space around 63 light years away. The group originally came from the same part of an interstellar cloud, which was a combination of dust, gas, and space plasma.
As the cloud collapsed, the brown dwarfs became scattered like seeds in the wind. By studying the most unusual and extreme stars like brown dwarfs, Gizis hopes to learn more about ordinary ones. One of the most unique features of brown dwarfs is they do a complete spin every five hours, making for a very short day. Gizis said:
“In some respects, brown dwarfs are a lot like planets, especially Jupiter, the gas giant in our solar system.
“They end up being a similar size because they are failed stars, and they get colder and colder with time like a planet does. They also have clouds on them. With Kepler, you can see what the clouds do for several months. You can see how much change occurs — that’s the type of thing we’re trying to figure out.”
The team is also searching for evidence of clouds and planets. They do this by looking for changes in brightness due to a planet moving in front of a brown dwarf or star. Flares can also have an impact on planets.
As a sun blasts out a massive X-class solar flare, it can release the energy equivalent to a billion hydrogen bombs all exploding at the same time. Earth has felt the effect of such outbursts, affecting satellites and communications systems, as well as electrical power grids. Gizis said:
“We think there are probably planets around brown dwarfs, so the flares generated by brown dwarfs could be a problem for them.
“But as to whether such a planet might be a habitable one like Earth — it’s a long shot.
“It would be more like Mercury, which is pretty much fried. There’s some debate about that. I guess we’ll find out.”