Sunday, May 28, 2017

Citizen Astronomers on the Hunt for Exploding Stars

Artist's impression of a Type Ia supernova. Credit: ESA

Now anyone can help untangle one of the greatest mysteries of our universe. The Australian National University (ANU) is encouraging citizen astronomers to join the search for supernovae – powerful stellar explosions occurring during the last evolutionary stages of a massive star's life. These violent events could deliver invaluable information about the expansion of the universe.

The hunt for supernovae is available on Zoouniverse.org. The site allows citizen scientists to analyze images provided by the SkyMapper Transient Survey. This survey is searching and studying supernovae and other transient objects using the SkyMapper 1.3 m telescope at the ANU Siding Spring Observatory in Australia.

Astronomers are specially interested in finding new Type Ia supernovae, which serve as great tools to measure cosmological distances. The distance is measured by calculating how much the light from the exploding star fades. Type Ia supernovae occur when a white dwarf star that accretes mass from a close companion collapses catastrophically until it reaches a critical limit at about 1.4 the mass of our sun. 

“The SkyMapper Transient Survey is searching for supernovae in the whole southern sky. We are the only survey looking in this hemisphere at these distances for Type Ia supernovae. These supernovae are important because they allow us to measure the expansion of the universe and therefore the effect of dark energy. The more supernovae we find at low redshift, the better the measurement of the expansion of the universe will be and that is what we are working on,” Anais Möller of the ANU Research School of Astronomy and Astrophysics (RSAA) told Astrowatch.net.

Zoouniverse.org offers volunteers a real treasure trove of images in which potential stellar explosions are waiting to be detected. In order to find a supernova, citizen scientists should look for differences and mark up those differences for the researchers, which could perform follow-up studies. Moreover, the first people who identify an object that turns out to be a supernova will be publicly recognized by the International Astronomical Union (IAU) as co-discoverers.

Currently, there are nearly 1,400 images on the site available for everyone who wants to join the search. The number of participating volunteers and classified pictures is constantly growing. So far, there are almost 1,000 citizen scientists in the project, which have already investigated over 49,000 images.

“We launched last week and in the first 24 hours of the project we obtained more than 30,000 classifications. Over 1,000 images have been classified and we are monitoring more than 20 possible or confirmed transients,” Möller revealed.

She added that time is essential when it comes to supernova studies. Therefore, as soon as Möller and her colleagues get the classifications they confirm the discovery of a transient and report it to the Transient Name Server. If it is a candidate they will send it off to get a spectrum of the object, which will tell them what kind of transient it is.

“The fastest we can find a supernova, the better we can understand them. This is crucial in supernovae studies because they shine only for a couple of weeks and then fade away. The contribution of citizen scientists is key for achieving this,” Möller told Astrowatch.net.

The project has already yielded a significant discovery recently. On May 25, ANU reported that citizen astronomers helped find a stellar explosion, which took place 970 million years ago, predating the dinosaurs' time on Earth.

The left image is the “new image” from a couple of nights ago while the middle one is the “reference” image taken a couple of years ago, the right image is the difference between “new” and “reference”. Credit: ANU
The left image is the “new image” from a couple of nights ago while the middle one is the “reference” image taken a couple of years ago, the right image is the difference between “new” and “reference”. Credit: ANU

"The supernova is about 970 million light years away, meaning that it exploded before the dinosaurs were even on the Earth," said Brad Tucker of RSAA.

Alan Craggs from Scotland and Elisabeth Baeten from Belgium are volunteers who identified the explosion, therefore they will be recognized as co-discoverers.

Tucker noted that besides this discovery, seven more potential supernovae have been reported to the Transient Name Server. Furthermore, the team is currently tracking 18 other possible exploding stars.

Given the fact that the first results of the hunt for supernovae are promising, the scientists hope for more detections that could improve our understanding of the universe and its expansion. Future results could also shed new light on the nature of supernovae and their evolution.

“There are many types of supernovae, some better known than others. Some we know how they are produced, some we don’t know this but know some of its properties. For example, we know that type Ia supernovae have almost the same intrinsic luminosity (their brightness is very similar when they explode). But we don’t know yet what are their ‘progenitors’, a white dwarf that accretes matter from a companion star that can be another white dwarf (double degenerate scenario) or a main sequence star like the sun or a red giant (single degenerate scenario)? We use them extensively but there are still a lot of questions to answer!” Möller concluded.

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