National Astronomical Observatory of Japan

Subaru Telescope Captures 1800 Exploding Stars

| Science

Some supernovae discovered in this study. There are three images for each supernova: before it exploded (left), after it exploded (middle), and the supernova itself (difference between the first two images). Original size (443KB)

Astronomers using the Subaru Telescope identified about 1800 new supernovae in the distant Universe, including 58 Type Ia supernovae over 8 billion light-years away. These findings will help elucidate the expansion of the Universe.

A supernova is a powerful explosion at the end of the life of a massive star. The star often becomes as bright as its host galaxy, shining one billion times brighter than the Sun for one to six months before dimming down. Type Ia supernovae are particularly useful because their consistent maximum brightness allows researchers to calculate how far the star is from Earth. This is particularly useful for researchers who want to measure the expansion of the Universe.

But supernovae are rare events. To spot as many supernovae as possible, a team led by Professor Naoki Yasuda of the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) used the Subaru Telescope equipped with Hyper Suprime-Cam, an 870 mega-pixel digital camera, to capture sharp stellar images over a very wide area of the night sky. By taking repeated images of the same area of the night sky over a six month period, the researchers could identify new supernovae by looking for stars that suddenly appeared brighter before gradually fading out.

The team identified about 400 Type Ia supernovae. Fifty-eight of these Type Ia supernovae are located more than 8 billion light-years away from Earth. In comparison, the Hubble Space Telescope took about 10 years to discover a total of 50 supernovae located more than 8 billion light-years away.

“The Subaru Telescope and Hyper Suprime-Cam have already helped researchers create a 3D map of dark matter, and observation of primordial black holes, but now this result proves that this instrument has a very high capability finding supernovae very, very far away from Earth.” said Yasuda.

Next, researchers will use the data to calculate the expansion of the Universe more accurately and study how dark energy’s effect on that expansion has changed over time.

These findings were published as “The Hyper Suprime-Cam SSP Transient Survey in COSMOS: Overview” in the Publications of the Astronomical Society of Japan on May 30, 2019.

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