On the road: AAS January 2013 meeting — supernovae and dark energy

Posted by Liz Kruesi
on Thursday, January 10, 2013

It’s the end of the third full day, and my last, at the American Astronomical Society meeting. In addition to attending press conferences about exploding massive stars and cosmology, I spent time checking out some of the poster presentations and attending science sessions about imaging exoplanets and also stellar astrophysics projects from the Kepler mission (it doesn’t just detect worlds around other stars).

The first press conference grouped recent supernovae discoveries with the quest to understand dark energy — the mysterious something that’s speeding up cosmic expansion. Jon Mauerhan of the University of Arizona’s Steward Observatory announced his team’s observations of Supernova 2009ip. This star increased dramatically in brightness in 2009, which led to astronomers thinking it was a supernova and thus designating it as such. The object, however, faded after about 10 days — much shorter than typical supernovae do. Observations of its radiation spectrum also indicated that SN 2009ip was a supernova imposter. Astronomers actually classified it as what’s called a “luminous blue variable.”

The Dark Energy Camera viewed the Small Magellanic Cloud when it first opened its eye. The camera captures an area about 20 times the Full Moon. // photo by Dark Energy Survey Collaboration
Mauerhan and colleagues looked at archives of the region around SN 2009ip and saw that the star’s brightness varied over the past 10 years. In 2010, the star underwent another outburst. Two years later, July 24, 2012, it had yet another flare-up, but this one didn’t fade away. Instead, it brightened dramatically on September 22 — by about 100 times in visible radiation and 1,000 times in ultraviolet. This sudden increase in luminosity resulted from fast stellar material (that was released in July) slamming into the previously shed gaseous shells from the prior years’ outburst. As the gas collided, it lit up. The team concluded that the 2012 burst was, in fact, a supernova explosion. However, the scientists aren’t sure why the star underwent the smaller blasts and variable brightness over the past decade.

After this supernova announcement, David Rubin of the University of California, Berkeley, described his team’s study of the best-measured most-distant type Ia supernova. Scientists are working to thoroughly understand this class of exploding star because it’s been used to determine distance measurements. In the late 1990s, observations of these objects led scientists to the discovery that the universe’s expansion is actually speeding up. To better understand the cosmic acceleration, cosmologists need to find more of these supernovae at even-farther distances. Rubin’s team has studied a type Ia blast dating from nearly 10 billion years ago.

Josh Frieman of Fermi National Accelerator Laboratory outside of Chicago then described the Dark Energy Survey (DES). This project will study the southern skies for 525 nights over the next five years from the 4-meter Blanco Telescope at Cerro Tololo Inter-American Observatory in Chile. The Dark Energy Camera, built at Fermilab, has undergone extensive testing over the past few months and should be complete in mid-February, says Frieman. Then, members of the astronomy community will be able to observe using the camera  September through February, when DES will run. Over the next five years, the survey will run on the telescope over those same months. The plan is to study dark energy via four different techniques, and narrow the options for what this something is.

The DES team expects to have the first results in late 2015.

So my last day at AAS leaves me with a list of projects to keep an eye on —- from DES to the NASA Wide-Field Infrared Survey Telescope to the Kepler spacecraft. It's been a busy past few days at the biggest astronomy meeting of the year. I'm leaving with a number of ideas for future articles to include in the magazine and many great science contacts. So long, Long Beach.

Check out my Monday and Tuesday recaps for more about the meeting.

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