Astronomers have discovered the fastest nova to date, and it is constantly wobbling.

The strange nova might provide details about how star explosions fill our solar system and the cosmos at large.
In an intermediate polar system, like the one seen in this artist’s illustration, matter taken from a companion star flows into an accretion disc around a white dwarf. However, the white dwarf’s magnetic field affects that substance, causing oscillations in the system’s light emissions.

A distant cosmic object just had an intense eruption on June 12, 2021. The ordinarily inconspicuous white dwarf star, which is stealing material from its nearby partner, achieved a maximum brightness of around magnitude 6.2, or 10,000 times brighter than it had been. In fact, for a minute the star was so brilliant that it could be seen with the naked eye.

The nova, or new star, fell to one-sixth of its maximum brightness in just one day. It is unprecedented for a classical nova event like this to see such a quick fall.

“It was only about one day, and the previous fastest nova was one we studied back in 1991, V838 Herculis, which declined in about two or three days,” said Sumner Starrfield, an astrophysicist at Arizona State University who led the new study, in a press release.

On June 14, at the 240th American Astronomical Society meeting, Starrfield spoke to the media about the record-breaking nova, known as V1674 Herculis. The American Astronomical Society’s Research Notes has approved a report describing the quick nova as well as some of the star’s other unusual features, such as the way its light is released pulses like the sound of a ringing bell.

What exactly is a nova?

A star that suddenly begins to glow in the night sky is referred to as a nova, which is derived from the Latin word for “new.” Novae come in a variety of shapes, including classical, kilonovae, supernovae, and hypernovae.

The most benign of these stellar explosions are called classical novae. They develop when a companion star that is otherwise healthy absorbs material from a white dwarf, which is the dense, fuel-depleted corpse of a once-shining star. The surface of the white dwarf gradually fills with this plundered material, which is mainly hydrogen.

The enormous surface gravity and high temperature of the white dwarf ultimately trigger a runaway thermonuclear reaction in the shell of accumulating material. A classical nova can quickly release 10,000–100,000 times more energy than our Sun produces in a year, but not becoming nearly as strong as a supernova. On the other side, a brilliant nova often takes many weeks or more to fade, not just a day.

V1674 Herculis: Quick and erratic

The nova V1674 Herculis displays a persistent “wobble” in the light it releases in both visible and X-ray wavelengths in addition to a sharp reduction in brightness.

This strange stellar ringing apparently isn’t dependent on brightness, either. “The most unusual thing is that this oscillation was seen before the outburst, but it was also evident when the nova was some 10 magnitudes [100,000 times] brighter,” said Mark Wagner, a research scientist at The Ohio State University and co-author of the new study, in a press release. “A mystery that people are trying to wrestle with is what’s driving this periodicity that you would see it over that range of brightness in the system.”“As best we can tell, because of the 500-second oscillation, [this nova is] an ‘intermediate polar,’ where the gas is flowing from the secondary into an accretion disk,” Starrfield said during his presentation at AAS. “But because of the strong magnetic field of the white dwarf, it comes down on the poles.”

The scientists found that V1674 Herculis ejects particles in addition to oscillations. Additionally, it appears that the material’s form changes in response to the white dwarf’s location.

Understanding what drives V1674 Herculis is necessary to comprehend the role that novae play in enhancing space with a variety of materials.

“We’re always trying to figure out how the solar system formed, where the chemical elements in the solar system came from,” Starrfield said in a press release. “One of the things that we’re going to learn from this nova is, for example, how much lithium was produced by this explosion. We’re fairly sure now that a significant fraction of the lithium that we have on the Earth was produced by these kinds of explosions.”

Going ahead, according to Starrfield, his team intends to use the Large Binocular Telescope in Arizona to examine the gases released by the nova during its outburst in an effort to determine how the explosion took place.

Reference(s): eurekalert, American Astronomical Society.

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