Supernovae

At a glance

Key points

For weeks a single explosion can outshine its galaxy.

• One explosion can outshine a galaxy
• Webb found SN 1987A's neutron star
• Betelgeuse dimmed by two-thirds in 2019–20

SN 1987A

Neutrinos from the collapse reached Earth hours before the light. In 2024 Webb found ionised argon at the centre of the debris, the first direct evidence that a neutron star formed there.

Betelgeuse

The red supergiant's dramatic dimming was caused by a surface outburst that threw off material which cooled into dust. Its chances of exploding in our lifetime are small.

Standard candles

Thermonuclear supernovae peak at nearly the same brightness, which let astronomers discover in 1998 that cosmic expansion is accelerating.

How often

Estimates of the Milky Way's rate range from well under one to a few per century; a 2021 compilation of methods gives about 1.6 core-collapse supernovae per century. Yet the last one confirmed by naked-eye observers was Kepler's in 1604, because dust in the galactic disc hides most of our galaxy from view. The next core collapse nearby will announce itself first through neutrinos, which pass through the dust.

Catching them early

SN 2023ixf, spotted by the amateur astronomer Koichi Itagaki in May 2023 in the Pinwheel Galaxy (M101), about 21 million light-years away, was the closest supernova in five years and a core collapse bright enough for backyard telescopes. Since 30 June 2026 the Vera C. Rubin Observatory's ten-year survey has been revisiting each patch of the southern sky hundreds of times, sending out up to seven million alerts a night about anything that changes.

Missions

1. 1990–

   Hubble Space Telescope

   NASA / ESAActive

   Ultraviolet to near-infrared imaging from low Earth orbit.

   Mission page (opens in a new tab)

2. 2021–

   James Webb Space Telescope

   NASA / ESA / CSAActive

   Infrared observatory at Sun–Earth L2, about 1.5 million km from Earth.

   Mission page (opens in a new tab)

Related entries

• Crab NebulaM1 · the wreck of the supernova of 1054
• Neutron starsCity-sized stellar cores
• Large Magellanic CloudThe Milky Way's biggest satellite

Sources

1. NOIRLab noirlab2616: Rubin Observatory begins the LSST (opens in a new tab)
2. ESA: ESA/Webb weic2404 (opens in a new tab)
3. NASA Imagine the Universe: white dwarfs (opens in a new tab)
4. NASA Science: Hubble: Betelgeuse's dimming (opens in a new tab)
5. NASA JPL: NASA scientist finds Betelgeuse's companion (opens in a new tab)
6. ESA: ESA/Webb weic2330 (opens in a new tab)
7. Rozwadowska, Vissani & Cappellaro 2021, New Astronomy (arXiv) (opens in a new tab)
8. NASA Science: APOD: supernova in M101 (opens in a new tab)

Last reviewed 10 Oct 2026 against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.