“So the universe is not quite as you thought it was. You’d better rearrange your beliefs, then. Because you certainly can’t rearrange the universe.”
— Isaac Asimov
When you hear something about bizarre or unusual stars, it's generally about neutron stars or pulsars, but the universe is a big place, filled with interesting objects. As such, it has a tendency to shoot down prevailing notions about the rules of nature itself, as the Asimov quote above says, reminding us that we don't know as much as we think we know. This special kind of star is a great example of that.
A flare star recently caught the eye of astronomers, who noted something interesting. Using the SCORPIO camera (owned by the Byurakan Astrophysical Observatory), they witnessed a dim star become exponentially brighter, until it became 15 times brighter than normal, exceeding its temperature *seven* times over in less than 160 seconds.
Interestingly, this phenomenon has been noted before. Many stars, like our sun, are variable stars: Stars like this tend to increase and decrease in luminosity over time. Some of these changes in brightness are so reliable, they help us discern the true distance separating objects in space. However, this instance is a little unusual.
The star in question, known as WX UMa, is located a mere 15.6 light-years from Earth in the Ursa Major constellation. It belongs to the M spectral class of stars, which are generally dim main-sequence stars that have temperatures that usually hang around 2,800 kelvin (K).
Its companion, on the other hand, shines almost one hundred times brighter than WX UMa most of the time. That is, unless the star goes into flare mode, when its luminosity unpredictably surges, temporarily transforming the star from an M-type to a class-B, with temperatures coming in between 10,000 to 33,000 K. For instance, some of the hottest and most luminous stars in our local universe are class-B stars (such as Rigel and Beta CMa) which tend to be massive, metal-poor stars that only live hundreds of millions of years before going supernova.
Last year, when the Byurakan team members were studying the star, after only a few minutes of observation, they saw the star return to normal... the flare left gone just as quickly as it came. As for the source of the flares, they are thought to occur as a result of plasma instability. Said instabilities mess with the magnetic field, causing turbulence in the stars' structure. After this turbulence, a process called 'magnetic reconnection' occurs, which sees energy from the magnetic field transform into kinetic energy, helping the star to stabilize again (somewhat akin to electric discharge). Ultimately, the kinetic energy held by the plasma transforms into thermal energy used in the upper layer of the atmosphere and corona, allowing astronomers to detect rapid changes in the electromagnetic spectrum.
According to Vakhtang Tamazian, professor at the University of Santiago de Compostela:
“Photometric and spectroscopic monitoring of this kind of flare stars is very relevant because it provides us with information about the changing states and physical processes, which are in turn key to studying the formation and evolution of stars.”
[Sourced From ScienceDaily]
Read the entire study at Astrophysics: "Spectral observations of flare stars in the neighborhood of the sun.