Scientists find 1,800 supernovae, may help measure the rate the universe expands

A supernova is an exploding star that reached the end of its life and is sometimes brighter than the Sun.

Scientists have discovered about 1,800 new supernovae or exploding stars, that may help measure how fast the universe is expanding.

The researchers from Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) and the University of Tokyo in Japan combined data from one of the world's most powerful digital cameras and a telescope capable of capturing a wider shot of the night sky compared to other big telescopes. The finding includes 58 Type Ia supernovae located eight billion light years away.

Supernova classed as Type Ia are useful because their constant 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.

A supernova is a name given to an exploding star that has reached the end of its life. The star often becomes as bright as its host galaxy, shining one billion times brighter than the Sun for any time between a month to six months before dimming down.

A false-colour composite of the Cassiopeia A supernova, with data from Spitzer, Hubble and Chandra telescopes. Image: NASA

Representational image. Image credit: NASA

In recent years, researchers began reporting a new type of supernovae five to ten times brighter than Type Ia supernovae. Named Super-Luminous Supernovae, many have been trying to learn more about these stars. Their unusual brightness enables researchers to spot stars in the farthest parts of the universe usually too faint to observe. Since distant universe means the early universe, studying this kind of star could reveal characteristics about the first, massive stars created after the Big Bang. However, supernovae are rare events, and there are only a handful of telescopes in the world capable of capturing sharp images of distant stars.

To maximise the chances of observing supernova researchers used the Subaru Telescope, which is capable of generating shape stellar images, and the Hyper Suprime-Cam, an 870-megapixel digital camera attached at its top, captures a very wide area of the night sky in one shot.

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.

As a result, the team identified five super-luminous supernovae and about 400 Type Ia supernovae. Fifty-eight of these Type Ia supernovae were located more than 8 billion light-years away from Earth.

In comparison, it took researchers using the Hubble Space Telescope about 10 years to discover a total of 50 supernovae located more than eight billion light years away from Earth.

"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 Naoki Yasuda, a professor at Kavli IPMU.

The next step will be to use the data to calculate a more accurate expansion of the Universe, and to study how dark energy has changed over time.

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