[Music throughout] Now and then, an obscure star briefly
flares up, brightening up to a million times. It’s an event
called a nova. The star V906 Carinae
erupted as a nova in 2018. Observations from
three satellites provide new insights into what happened.
NASA’s Fermi mission has seen 14 novae since 2010.
Before then, astronomers didn’t think novae could glow in gamma rays,
the highest-energy light. When a white dwarf pulls
material from a companion star, the gas forms a thickening layer
that eventually erupts in a thermonuclear fireball. A nova
is born. Led by a team from Michigan State University,
astronomers studied V906 Carinae using high-energy data from Fermi,
NASA’s NuSTAR X-ray telescope, and in
visible light from a Canadian satellite named BRITE-Toronto.
Shaped by the orbital motion of the stars, the explosion debris
first forms a thick expanding ring around the system.
Then, after 10 days or so, fast outflows — likely
driven by residual fusion on the white dwarf — strike the ring.
The resulting shockwaves produce gamma-ray and optical flares
that radiate away most of the nova’s energy. These
observations provide the first direct evidence that shock waves
can power most of a stellar explosion’s visible light.
Figuring out how they work in nearby novae will help us understand
more powerful events much deeper in the cosmos.
Explore: solar system & beyond. NASA