Records of 'new stars'
To ancient observers a supernova was a sudden "guest star." Chinese records from 1054, along with Japanese sources, describe a star bright enough to see in daylight for 23 days; its remains are today's Crab Nebula in Taurus. In 1572 Denmark's Tycho Brahe measured a new star in Cassiopeia so precisely that it undermined Aristotle's idea of an unchanging heaven, and the supernova Johannes Kepler watched in 1604 is still the last one seen with the naked eye in our galaxy. Fritz Zwicky and Walter Baade coined "supernova" around 1931 and in 1934 predicted that it leaves behind a neutron star.
Two ways to explode
A star more than about eight times the Sun's mass fuses elements up to iron in its core, then can no longer release energy; in under a second the core collapses and the outer layers rebound outward. This is a core-collapse supernova such as Type II, leaving a neutron star or a black hole. When SN 1987A went off in the Large Magellanic Cloud, Japan's Kamiokande detected 11 neutrinos, earning Masatoshi Koshiba a share of the 2002 Nobel Prize. A Type Ia, by contrast, is a white dwarf in a binary that pulls matter from its companion until it reaches the Chandrasekhar limit, about 1.4 solar masses, and detonates. Because their peak brightness is so consistent, they serve as "standard candles." Betelgeuse in Orion is a leading candidate for a future core-collapse event.
Measuring the cosmos, seeding life
In 1998 the teams of Adam Riess and Brian Schmidt and of Saul Perlmutter independently found that distant Type Ia supernovae were dimmer than expected, meaning cosmic expansion is speeding up rather than slowing. That introduced mysterious dark energy and won the trio the 2011 Nobel Prize in Physics, refining the expanding-universe picture that began with Hubble's law and the Big Bang. Much of the calcium, iron and oxygen in our bodies was also scattered by ancient supernovae, which is why Carl Sagan said "we are made of star-stuff."
FAQ
- Would a nearby supernova be dangerous?
- Studies suggest one within about 50 light-years could harm life, for instance by damaging the ozone layer, but no star that close is known to be a candidate. Betelgeuse, about 550–700 light-years away, is at a safe distance.
- When will Betelgeuse explode?
- "Soon" in astronomical terms, likely within roughly 100,000 years. Its dramatic dimming in 2019–2020 turned out to be a dust cloud, not a sign of imminent explosion.
Sources reviewed: 2026-10-26
References
- Baade, W., & Zwicky, F. (1934). On super-novae. PNAS, 20(5), 254–259.
- Riess, A. G., et al. (1998). Observational evidence from supernovae for an accelerating universe and a cosmological constant. Astronomical Journal, 116(3), 1009–1038.
- Perlmutter, S., et al. (1999). Measurements of Ω and Λ from 42 high-redshift supernovae. Astrophysical Journal, 517(2), 565–586.