For the first time, astronomers have directly observed the shockwave from a supernova explosion ripping through the surface of a dying star, revealing a surprisingly symmetrical event. Capturing this fleeting moment has long been challenging due to the rarity of observing supernovas early enough and with sufficient telescope power.
When supernova 2024ggi erupted in the spiral galaxy NGC 3621 on April 10, 2024, an international team led by Yi Yang from Tsinghua University in Beijing sprang into action. This relatively nearby supernova—located about 22 million light-years away in the constellation Hydra—presented a rare opportunity. Within 26 hours of its initial discovery by the ATLAS (Asteroid Terrestrial-impact Last Alert System) network, the team secured observing time on the Very Large Telescope (VLT) at the European Southern Observatory (ESO) in Chile.
This rapid response was crucial. The star involved was a massive red supergiant, between 12 and 15 times heavier than our sun. These stars eventually exhaust their nuclear fuel, leading to a core collapse that triggers an immense explosion—a supernova. However, due to the star’s enormous size (around 500 times wider than our sun), it took approximately a day for the shockwave generated by this implosion to break free from the star’s visible surface.
As astronomer Dietrich Baade from ESO explains, “The first VLT observations captured the phase during which matter accelerated by the explosion near the center of the star shot through the star’s surface.” This precious window of observation allowed the team to study both the geometry of the exploding star and its surrounding material simultaneously.
What they observed was a flattened shape resembling an olive or grape, propagating symmetrically outward even as it encountered a ring of circumstellar material ejected earlier by the dying star. This symmetry contradicts some prevailing theoretical models that predict neutrino absorption by the shockwave leading to highly asymmetrical explosions.
The team proposes that powerful magnetic fields might instead be responsible for any subsequent asymmetry observed in later stages of supernova development. The study’s findings will refine our understanding of stellar evolution and the mechanisms driving these catastrophic cosmic events.
By directly observing the shape and symmetry of this breakout shockwave, astronomers gain crucial insights into how massive stars ultimately meet their fiery ends.
