Homing in on Cosmic Explosions

For decades, astronomers pondered the source of one of the most energetic and mysterious events in the universe, gamma-ray bursts (GRB). In a few seconds, GRBs can emit more energy than the Sun over its entire 10-billion-year life. It wasn’t until Hubble began observing the visible source of these events that astronomers began to better understand their origins.

Gamma-Ray Burst 990123
NASA
Gamma-Ray Bursts
In 1997, astronomers employed Hubble's high resolution and sensitivity to hunt down a rapidly dimming fireball in the region of space that had produced a GRB. The explosive remnant rapidly faded, and ground-based observatories could no longer see it. Hubble observations allowed astronomers to continue following the fading source, and clearly showed that it had two components: a point-like object and an extended feature.
Gamma-Ray Bburst 970228
NASA, K. Sahu, M. Livio, L. Petro, D. Macchetto, and STScI
Soon after the GRB 990123 observations, Hubble’s Wide Field and Planetary Camera 2 captured the first visible light image that associates a gamma-ray burst source with a potential host galaxy. The bright source was not near the center of the galaxy – which might have suggested it came from a black hole at the galaxy’s heart – but on the outskirts.
Gamma-Ray Burst 130603B
NASA, ESA, N. Tanvir (University of Leicester), A. Fruchter (STScI), and A. Levan (University of Warwick)
Kilonovae
On June 13, 2013, Hubble observed a rapidly fading fireball produced in the aftermath of GRB 130603B, whose initial blast lasted only one-tenth of a second. The Hubble observation revealed a new kind of stellar blast called a kilonova, an explosion that astronomers predicted would accompany short-duration GRBs. This kilonova provided strong evidence that short-duration gamma-ray bursts are the result of a merger of two small, super-dense stellar objects, such as a pair of neutron stars or a neutron star and a black hole.
Kilonova in NGC 4993
NASA and ESA Acknowledgment: A. Levan (U. Warwick), N. Tanvir (U. Leicester), and A. Fruchter and O. Fox (STScI)
Then, in August 2017, Hubble was part of a team of observatories that detected the first combined gravitational wave and gamma radiation signal from a binary neutron star merger. Seventy observatories around the globe observed the merger’s aftermath. Hubble’s precise measurements allowed astronomers to pinpoint the explosion site and revealed the speed of a jet moving at least 99.97% the speed of light.
Gamma-Ray Burst 080319B
NASA, ESA, N. Tanvir (University of Leicester), and A. Fruchter (STScI)
Today, thanks in large part to Hubble observations, astronomers categorize GRBs into two types: Long GRBs (where the initial burst lasts two seconds or longer) and Short GRBs (where the burst lasts less than two seconds). Short bursts are associated with the collision of either two neutron stars or a neutron star and a black hole. Long bursts stem from the explosive, supernova deaths of massive stars.
SN1987a (August 1990)
NASA, ESA, and STScI
Supernovae
Hubble’s observations of supernovae have also played a key role in our understanding of these explosive star deaths. Its first observations of a supernova came just four months after its launch, when Hubble’s Faint Object Camera resolved an elliptical ring of material around the remnants of Supernova 1987A (SN1987A).
SN1987a Ring Brightening (images taken from 1994 to 2016)
NASA, ESA, Robert P. Kirshner (CfA, Moore Foundation), Peter Challis (CfA)
SN 1987A was the brightest exploding star astronomers saw in 400 years. Hubble’s sensitivity, resolution, and longevity allow it to keep track of SN1987a’s evolution, collecting 7,000 data sets for some 250 scientific proposals as of July 2024. This data revealed rings in different planes in 1994. The bright central ring is about one light-year across and existed when the star exploded. The star likely shed the ring thousands of years before it went supernova. Ultraviolet radiation from the exploding star caused it to glow in early Hubble images. As the gas cooled, the ring faded until the blast’s shock wave reached the ring causing it to brighten again.
Composite Image of NGC 2146 and SN 2018zd (bright spot on the right)
NASA, J. DePasquale (STScI), and Las Cumbres Observatory
Astronomers found evidence of a hypothesized electron-capture supernova by comparing a Hubble image of the supernova, called SN 2018zd, with earlier Hubble images of the same area of sky. This allowed them to identify the supernova’s progenitor star in the galaxy NGC 2146. Stars between eight and 10 times the mass of the Sun theoretically should explode in a different way. Their immense internal pressure would force electrons to fuse with atomic nuclei, causing a sudden drop in electron pressure that triggers the collapse and subsequent explosion of the star’s surrounding layers.
SN 2020fqv in NGC 4568
NASA, ESA, Ryan Foley (UC Santa Cruz) Image; Image Processing: Joseph DePasquale (STScI)
In April 2020, astronomers discovered a supernova inside the interacting Butterfly galaxies (NGC 4568). They quickly trained Hubble on the aftermath and got a ringside view of the supernova in the very earliest stage of exploding. Hubble viewed a region very close to the supernova, examining material ejected by the star in the last year of its life. These observations may provide astronomers with an early warning system for other stars on the brink of an explosive death.

Learn More

The Host Galaxies of Gamma-ray Bursts
This is a sampling of the host galaxies of long-duration gamma-ray bursts taken by NASA's Hubble Space Telescope.
Hubble Tracks the Fading Optical Counterpart of a Gamma-Ray Burst
Explore hands-on activities, interactive, lesson plans, educator guides, and other downloadable content about this topic.
Gamma-Ray Bursts: Hubble Data Offer New Clues and Puzzles
This Hubble image is the first visible-light view ever taken that links a gamma-ray burst with a potential host galaxy.
Hubble Finds 'Smoking Gun' After Gamma-Ray Blast
Gamma-ray bursts are mysterious flashes of intense high-energy radiation that appear from random directions in space.
NASA Missions Catch First Light from a Gravitational-Wave Event
Hubble photographed the glow from a titanic collision, shining within the galaxy NGC 4993 at a distance of 130 million light-years. Hubble also obtained an infrared spectrum that may yield signs of exotic, radioactive elements.
Hubble Pinpoints Record-Breaking Explosion
Peering across 7.5 billion light-years and halfway back to the big bang, Hubble photographed the fading optical counterpart of a powerful gamma-ray burst that holds the record for being the intrinsically brightest naked-eye object ever seen from Earth.
Hubble Resolves Gaseous Ring Around Supernova 1987a
Hubble resolved, to an unprecedented detail of 0.1 arcsecond, a mysterious elliptical ring of material around the remnants of Supernova 1987A.
The Dawn of a New Era for Supernova 1987A
Hubble has repeatedly observed SN 1987A since 1990, accumulating hundreds of images.
Theoretical Electron-Capture Supernova Discovered
An exploding star observed in 2018 is the first that fits all six criteria for a hypothesized type of supernova called an electron-capture supernova.
Hubble Gives Early View of a Doomed Star's Destruction
Sometimes, you're just in the right place at the right time! A nearby star went supernova while scientists were already observing it. Astronomers quickly trained Hubble on the aftermath.