The one-of-a-kind nova could show how stellar explosions seed the solar system and the rest of the universe.
In this artist’s picture of an intermediate polar system, stolen material from a companion star flows into an accretion disk that circles a white dwarf. But the magnetic field of the white dwarf stirs up this material, which changes the way the system’s light shines.
On June 12, 2021, just over a year ago, a faraway object in space erupted with a lot of energy. The normally unnoticeable star, which was a white dwarf sucking matter from a nearby companion, got as bright as magnitude 6.2, which is about 10,000 times brighter than it was before. In fact, the star got so bright that for a short time, you could see it with your own eyes.
But in just one day, the new star, or nova, dimmed to only one-sixth as bright as it was at its brightest. And for a classical nova event like this one, this is the first time that the light has dropped so quickly.
In a press release, Sumner Starrfield, an astrophysicist at Arizona State University who led the new study, said, “It was only about a day, and the previous fastest nova was one we studied in 1991 called V838 Herculis. It faded in about two or three days.”
Starrfield talked about the V1674 Herculis nova, which broke a record, at a press conference at the 240th meeting of the American Astronomical Society on June 14. Research Notes of the American Astronomical Society has agreed to publish a paper about the fast nova and other strange things about the star, such as the fact that its light pulses like the sound of a ringing bell.
Describe a nova.
Nova is Latin for “new,” and it’s used to describe a star that suddenly gets brighter in the night sky. But there are many different kinds of novae, from classical novae to kilonovae to supernovae to hypernovae.
Classical novae are the least powerful of these explosions of stars. They happen when a white dwarf, the dense, empty shell of a star that used to shine, steals material from a companion star that is still going strong. The stolen stuff, which is mostly hydrogen, piles up on the surface of the white dwarf.
Due to the white dwarf’s high surface gravity and temperature, the shell of accumulated matter eventually goes through a thermonuclear reaction that gets out of control. Even though a classical nova is not nearly as powerful as a supernova, it can still release 10,000 to 100,000 times more energy in a short amount of time than the Sun does in a whole year. But a bright nova usually doesn’t go away for a few weeks or longer, not just a day.
V1674 Herculis: Quick and up and down
V1674 Herculis has a light that keeps “wobbling” in both visible and X-ray wavelengths. This is in addition to the fact that the nova’s brightness is going down at a very fast rate.
This strange ringing of stars doesn’t seem to depend on how bright they are, either. Mark Wagner, a research scientist at The Ohio State University and co-author of the new study, said in a press release, “The most unusual thing is that this oscillation was seen before the outburst, but it was also clear when the nova was about 10 magnitudes [100,000 times] brighter.” “People are trying to figure out what’s causing this periodicity to show up in the system over such a wide range of brightness.”
“As far as we can tell, this nova is a “intermediate polar,” which means that gas is flowing from the secondary into an accretion disk,” Starrfield said during his talk at AAS. “But because the white dwarf has a strong magnetic field, it falls toward the poles.”
The researchers also found that V1674 Herculis’ ejects material, which is different from the oscillations. And the shape of that matter seems to depend on where the white dwarf is when it moves.
Learning exactly what makes V1674 Herculis work is important for understanding how novae add new elements to space.
In a press release, Starrfield said, “We are always trying to figure out how the solar system came to be and where its chemical elements came from.” “One thing we’ll learn from this nova is, for example, how much lithium was made by this explosion. We’re pretty sure now that a lot of the lithium on Earth came from these kinds of explosions.
Starrfield says that in the future, his team plans to use the Large Binocular Telescope in Arizona to study the gases that the nova released when it exploded. This will help them figure out exactly how the explosion happened.