Astronomers Found the Closest Supernova in a Decade

It’s not easy to get your head around cosmic distances. To say that something is 12 million light years away is basically unfathomable given our Earthly reference points for area. But astronomers do this all the time, not just discuss objects on this absolutely massive scale but also determine just how massively far away an object is.

They do this using supernovae as “standard candles” to help determine distances on a comic scale. Standard candles are objects that emit known amount of light, and because their brightness is known, astronomers can estimate their distance from the Earth by measuring the strength of their light. A common analogy is street lamps: If you’re standing in a street lined with street lamps, the inverse square law dictates that the second lamp will be one-quarter as bright as the first. The third will be one-ninth as bright as the first.

Now researchers at Texas Tech University have just found the eight-day old remnants of a new supernova in the M82 galaxy that will serve as a new and improved standard candle. The team discovered the closest Ia-type supernova, the kind used to gauge cosmic distance‚ that’s been found in a decade.

In our local galactic neighborhood, astronomers use Cephid variable stars as standard candles, young stars that pulse at regular intervals. But beyond our galaxy, astronomers can’t pick out individual stars to use as standard candles, so they turn to a different regular feature: incredibly bright stellar explosions or supernovae.

Which is why finding the closest type Ia supernova in a generation is significant. It’s location is, too; it’s close to Earth, meaning it will help astronomers and astrophysicists gain a better understanding of this particular type of supernova and also help them better estimate cosmic distances.

The key technology behind this discovery was a special spectroscopic camera called FLOYDS, developed by David Sands, an assistant professor in the Department of Physics at Texas Tech University.

Researchers used Sand’s camera in Hawaii to observe this supernova as well as a host of others. In the last six months, they have confirmed the existence of 30 different supernovae under the Intermediate Palomar Transient Factory project, a collaborative project between the California Institute of Technology, the Los Alamos National Laboratory, the University of Wisconsin and several other institutions. The project, which carries out automated surveys of the night sky, is dedicated to finding brief but bright supernova events.

“These type Ia supernovae are very important to astronomers in general,” Sand said, adding that they allow astronomers to “measure distances to within about 10 percent or so. These supernovae are very uniform, and the explosions emit the same intrinsic amount of light.”

Ultimately, having a better grasp of the size of the Universe will help scientists understand and explain the history of its expansion. And the goal isn’t just to find more standard candles; astronomers can also use the information gathered from this survey to understand what certain types of stars yield certain types of supernovae.

Sand thinks that Ia supernovae may begin as a carbon/oxygen white dwarf star feeding off its neighbor. Once the white dwarf star accretes enough material that it’s about 1.4 times the size of our Sun compressed into a sphere the size of the Earth, it becomes unstable and explodes into a supernova. But others disagree. Ariel Goobar from the Oskar Klein Center at Stockholm University studied pre-explosion images of M82, and believes the lack of pre-explosion detection suggests this supernova originated when two objects merged, like two white dwarf stars.

“Until very recently, the leading model for standard candle supernovae was thought to include a companion star from which material was stripped by the white dwarf until the accumulated mass could no longer be sustained by the outwards pressure, leading to a runaway thermonuclear explosion,” Goobar said. “The observations of this supernova are challenging for this theoretical picture.”

Supernovae serve yet another purpose in the astronomical world. They have also been used to show that the Universe is expanding through the acceleration phenomenon of dark energy.

“If we can judge distances better than the plus-or-minus 10 percent or so, I think this will lead to uncovering the details of dark energy we still need to understand,” Sand said. “We didn’t even know about dark energy until a few years ago. It’s almost like the universe is going to fly apart. Right now, there’s no good physical model or explanation for dark energy.”

So even though the process behind supernovae still isn’t fully understood, we know the explosions make for perfect standard candles, giving us a sense of the scale of the Universe even if we can’t fully grasp it.