A team of astronomers studying "ultracool" dwarf stars, generally believed to be little more than husks of matter, have found a surprising little anomaly in the Boötes constellation, about 35 light-years away.
Instead of a simple, cool shell, they found a star with a complicated magnetic field, and a rotating spot of hot hydrogen they liken to a lighthouse beam – this little dwarf's way of saying to the universe, "I'm not dead! I think I'll go for a walk..."
This type of star, called an M-type dwarf, has a mass of only about 8 percent to 10 percent of our Sun, and typically has a surface temperature of under 3860 degrees Fahrenheit (2127 degrees Celsius). By contrast, the Sun produces an average surface temperature of about 10340 degrees Fahrenheit (5727 Celsius).
With little heat, and only relatively simple processes going on inside,
M-type dwarf stars have been predicted to have simple magnetic fields as well, more like the Earth than the Sun.
Instead, this dwarf has a complex and active magnetic field, creating sparking flares that last up to a minute, the researchers say. They also watched a strange hot spot, composed of hydrogen-alpha
emission, rotate with the star's two-hour spin.
"Theory has always said that as we look at cooler and cooler stars, the coolest will be essentially dead," said Edo Berger, a
Carnegie-Princeton postdoctoral fellow involved with the research, in a statement. “It turns out that stars like (this one) have very complex magnetic activity around them, activity more like our Sun than that of a star that is barely functional."
What's going on here? Berger and his colleagues don't know yet. There might be a hidden companion star that's triggering the magnetic activity and hot spots. Or there might be more going on under the surface than scientists know or expected. (Dr. Evil's new laboratory, maybe?)
Either way, researchers will be looking into this little spark plug for some time.
Odd Little Star has Magnetic Personality [Gemini Observatory release]
(Image: A somewhat whimsical artist's conception of the "I'm not dead" dwarf. Credit: Gemini Observatory/ Dana Berry, SkyWorks Digital
Animation)
