SN 2014J boasts some unusual characteristics, experts say

Feb 28, 2014 19:01 GMT  ·  By

A team of investigators at the University of California in Berkeley (UCB), led by astronomer Alex Filippenko, has recently discovered that the latest observed supernova, dubbed SN 2014J, boasts some unusual characteristics that may throw our theories about Type Ia supernovae down the drain. 

The massive explosion occurred in the nearby galaxy Messier 82 (M82), which is located in the Big Dipper, some 11.4 million light-years away. It is the closest event of this type recorded in 27 years, since the explosion of SN1987A. However, the latter was a Type II supernova, so SN 2014J is the closest Type Ia supernova in about 77 years.

Unlike a Type II supernova, which occurs when a massive star reaches the end of its main sequence and explodes violently – collapsing into a black hole or a neutron star – Type Ia supernovae occur in binary systems that feature a white dwarf. These are stars that were once about the size of the Sun, but which have exhausted their hydrogen supply and are now fusing helium into heavier elements.

Also unlike Type II supernovae, Type Ia explosions are used as so-called astronomical yardsticks to measure distances in the Universe. Filippenko says that he and his group came across a chance image of SN 2014J in data from the Katzman Automatic Imaging Telescope (KAIT), at Lick Observatory near San Jose, California.

Apparently, the telescope snapped an automatic image of M82 just 37 hours after the explosion had occurred, on January 14. The astronomer combined this photo with another collected by a Japanese amateur astronomer, and realized that several inconsistencies existed between theoretical predictions of what happens during Type Ia supernova explosions and what was actually being observed.

For starters, the blast brightened a lot faster than it should have. Even more interestingly, the event displayed the same rapid brightening pattern as SN 2013dy, a supernova blast KAIT identified in 2013.

“Now, two of the three most recent and best-observed Type Ia supernovae are weird, giving us new clues to how stars explode,” the astronomer says. The third comet he is referring to is SN 2011fe, obviously discovered in 2011, which followed the “normal” theoretical predictions for such an event.

“This may be teaching us something general about Type Ia supernovae that theorists need to understand. Maybe what we think of as ‘normal’ behavior for these supernovae is actually unusual, and this weird behavior is the new normal,” Filippenko explains.

Any change in our understanding of how Type Ia supernovae explode would have significant implications on how astronomers measure distances in space. By extension, a different theory of such events could change the way we interpret the Universe as expanding at an ever-accelerating rate.

In the early 1990s, astronomers including a team led by Filippenko determined that Type Ia supernovae explode at the same brightness regardless of where they are in the Universe. This is why they are now called standard candles and are used as fixed points in space with respect to which distances are measured.

The fact that the Universe expands was calculated based on measurements of the changes in distance that occur between multiple standard candles over decades of observations. If the theoretical background for this is wrong, then everything built on top could be wrong as well.

This is why early detections of Type Ia supernova are very important, the UCB astronomer explains.

“Very, very early observations give us the most stringent constraints on what the star’s behavior really is in the first stages of the explosion, rather than just relying on theoretical speculation or extrapolating back from observations at later times, which is like observing adolescents to understand early childhood,” Filippenko concludes.