By Ken Croswell
A newborn star whizzing past another stellar youngster triggered a cosmic flare-up that began nearly a century ago and is still going strong today, researchers say.
In late 1936, a dim star in the constellation Orion started to erupt in our sky and soon shone over 100 times as brightly as it had before. Only telescopes could detect the star prior to the outburst, but afterward, the star was so bright it was visible through binoculars. The star even lit up part of the previously dark interstellar cloud called Barnard 35 that presumably gave the star birth (SN: 1/10/76).
Amazingly, the star, now named FU Orionis, is still shining almost as brightly today, 85 years later. That means the star wasn’t a nova, a stellar explosion that quickly fades from view (SN: 2/12/21). But the exact cause of the long-lasting flare-up has been a mystery.
Now, computer simulations may offer a clue to what’s kept the celestial beacon shining so brightly. Located about 1,330 light-years from Earth, FU Orionis is actually a double star, consisting of two separate stars that probably orbit each other. One is about as massive as the sun, while the other is only 30 percent to 60 percent as massive. Because the stars are so young, each has a disk of gas and dust revolving around it. It’s the lesser star’s passage through the other star’s disk that triggered and sustains the great flare-up, the simulations suggest.