Astronomers have discovered a rare, ultra-luminous supernova whose intrinsic brightness, at peak luminosity, was 100 billion times that of the Sun. This special type of stellar explosion, called a self-interacting supernova or super-luminous supernova, results from exploded material interacting with previously puffed-off layers from the star. The type of progenitor star whose fate it is to end this way is called a luminous blue variable. A well-known example in our own galaxy is Eta Carinae, pictured below.

Luminous blue variable star, Eta Carinae, could end its life as a super-luminous supernova

Measured to be about 3.7 billion light-years away, the extreme brightness of the newly discovered supernova allowed astronomers to detect it using a relatively small robotic telescope that’s part of the ROTSE Supernova Verification Project (RSVP). So far, RSVP has found five of the 12 known supernovae of this type. To give you some idea how rare these objects are, consider how supernovae are named. This particular object is called SN 2008am. The numbers tell us the year it was discovered, while the letters tell us the order in which it was discovered. The first supernova detected in 2008 was called 2008a, the second 2008b, and so on. This makes SN 2008am the 39th supernova discovered that year. I don’t know the total number of supernovae that were discovered in 2008, but the RSVP website indicates an object named SN 2008io, which means there were at least 249. (All of those are in other galaxies, by the way — we haven’t observed a supernova in our own galaxy for about three hundred and fifty years.) So, 12 super-luminous supernovae out of hundreds of all types observed annually makes these particular objects rare indeed.

Continue reading →

Artist's conception of material from a nearby star forming a plasma disk around black hole Cygnus X-1. Credit: ESA

Astrophysicists have observed what appears to be direct evidence of strong magnetic fields around a black hole, supporting a popular theory about the production of plasma-and-radiation jets observed to emanate from these mysterious objects. The evidence comes from seven years of data showing high-energy polarized light radiated from a region near the event horizon of Cygnus X-1, the first black hole ever observed.

Polarized light is light that vibrates in a specific pattern, and it can be a signature of radiation from charged particles that are sped up in a magnetic field. The magnetic field is a product of super-hot plasma — material torn from a nearby star — that’s smeared into a disk around the black hole. The twisting of the magnetic field lines as the black hole rotates is believed to be the mechanism for producing jets.

Cygnus X-1 was discovered as a mysterious X-ray source in the 1960s, but it was many years later when astrophysicists reached consensus that it was a black hole¹. The discovery and speculation as to its nature inspired the prog-rock band, Rush, to write a song about Cygnus X-1 in the late 1970s, complete with some of the best rock-song lyrics of all time:

Continue reading →

Astronomers have discovered the coldest-ever failed star with a surface temperature of 100^o C. To give you some perspective, consider: 1) the hardiest Finns can easily withstand 120^o C saunas; and 2) our Sun, a relatively mediocre star, has a surface temperature of almost 5,500^o C.

This lukewarm object, called CFBDSIR J1458+1013B, appears to be a brown dwarf, a class of objects somewhere between star and super-planet. The distinction between star and brown dwarf is clear — a star is only a star if it undergoes nuclear fusion in its core — but the distinction between brown dwarf and super-planet isn’t as clear.  Brown dwarfs are all about the same size as Jupiter, but they pack a lot of mass into that space — at the high end of the range, they can be 90 times the mass of Jupiter — and unlike planets, they sometimes emit X-rays. CFBDSIR J1458+1013B is at the lower end of the range with a mass of about 6-15 Jupiter-masses. With its super-cool surface temperature, astronomers speculate that it could even have water clouds in its atmosphere.

Continue reading →

It appears a close binary system — a pair of stars orbiting so close they were touching — has finally merged into a single stellar object, producing an enormous flash of light in the process. The pair, called V1309 Sco, was observed by astronomers to briefly reach a luminosity 10,000 times greater than normal (30,000 times more luminous than the Sun) before settling back down to its normal brightness. Astronomers believe the unusual flash corresponded to the moment when the two stars merged — the first time such an event has been directly observed.

It is not known how common such close pairs are, but multiple-star systems of larger separation are quite common. This vid features animation (apparently using real data) showing the orbits of several known binary star systems.

Continue reading →