Finding supernovae—stars that explode—is a tricky business; a supernova appears as a bright star for a short period of time, usually between hours and months. If we’re not looking in the right place at the right time, they’re easy to miss.
Studying the elements that are dispersed when stars explode helps us understand how new star systems are formed, and learn more about the conditions that make life–including ours–possible!
But there’s no warning for when or where a supernova will appear, so a lot of time they’re found after the fact, by astronomers who compare images of the same area of sky and look for objects that change in brightness over time.
In the past, data about supernovae have been pieced together from different astronomical surveys, because astronomers need frequent images of the same area of sky to catch a supernova in the act. But since each survey uses a different telescope and a different observing strategy, it can be challenging for scientists to get consistent and accurate data.
Not anymore! Rubin Observatory is a great instrument for finding supernovae because it will be scanning the whole Southern Hemisphere sky at more frequent intervals than any telescope in history.
Rubin Observatory will automatically send out an alert whenever a change is detected in one of its images, and it will take images of the same part of sky every few nights. So a star that has increased in brightness since the last time Rubin Observatory took an image of it will trigger an alert within 60 seconds! No other survey has done this before.
But not all alerts will come from supernovae--there are a lot of other reasons why objects might change in brightness too. So astronomers who study supernovae have computerized ways of filtering all these alerts to find the ones that are most likely to be supernovae, and that will help them narrow down the best candidates to follow up with using other telescopes.
On average, it takes about two weeks for the light from a supernova to reach its maximum brightness. The earlier astronomers find one, the longer they can study its evolution before it fades.
The data set generated by Rubin Observatory over 10 years is expected to contain information about 10 million supernovae. Compare that to the fact that only a few thousand supernovae have been observed to date, and you'll understand why astronomers who study supernovae are so excited about Rubin Observatory!
