Hubble telescope spots death of a white dwarf 10 billion years ago

Hubble Space Telescope image of a supernova more than 10 billion light-years away. This explosion, known as a white dwarf or type Ia supernova, is the most distant of its kind yet seen.

NASA, ESA, A. Riess (STScI and JHU), and D. Jones and S. Rodney (JHU)

When a white dwarf explodes as a type Ia supernova, its death is so bright that its light can be detected across the Universe. A new observation using the Hubble Space Telescope identified the farthest type Ia supernova yet seen, at a distance of greater than 10 billion light-years. In the tradition of supernova surveys, this event was nicknamed for Woodrow Wilson, 28th President of the United States. The previous record-holder, Supernova Mingus, was about 350 million light-years closer to Earth.

White dwarfs are the remains of stars similar in mass to the Sun. Since such a star would have to live out its entire life to form a white dwarf, there are limits to how early in the Universe's history a type Ia supernova can explode. Only 8 white dwarf supernovas have been identified farther than 9 billion light-years away. (Some core-collapse supernovas, which are the explosions of very massive stars, have been seen farther than Supernova Wilson.) Since all such explosions happen in a similar way, cosmologists use them to measure the expansion rate of the Universe.

Astronomers found this violent event by comparing the light from several separate long exposures of the same patch of the sky, known as CANDELS (the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey). Bright as it was, the distance was so great that Supernova Wilson appeared as an enhancement of the luminosity of its host galaxy. The researchers subtracted the light of the galaxy without the supernova from the combined supernova-galaxy combination, then analyzed the residual light to identify it as type Ia.