Almost exactly one year ago, Seiji Ueda, an amateur astronomer in Japan, made a record-breaking discovery.
Using computer software to compare current images of space against older records, he discovered something new.
And really, really, bright.
Within hours, scientists and researchers Sumner Starrfield, Charles “Chick” Woodward and Mark Wagner had been alerted to the June 12 find: nova V1674 Hercules.
This was no ordinary nova, that much was certain.
“What we saw, and what many people saw, including amateurs, was that a new star appeared where seemingly there wasn’t one before. This was in the constellation Hercules,” Wagner said.
Classical novae are a consequence of how some close binary stars evolve. During their outbursts, they eject matter from the surface of a small white dwarf star at high speeds where it’s viewed as a fast and large increase in the brightness of the star.
“It’s the third-largest explosion that happens in a galaxy,” he added. “It’s also the largest hydrogen bomb in the universe,” Wagner said.
“How stars evolve during their lifetime is dependent upon their mass,” he continued. Stars like the sun consume hydrogen as fuel and convert it into helium. Eventually the star swells to become a red giant star and ultimately leaves behind a dense core of carbon and oxygen roughly the size of our Earth, called a white dwarf star. Novae are caused by the white dwarf acquiring or accreting material from a nearby companion star until the consumption of the material on the surface explodes and sends matter shooting into space.
Setting a record
Nova V1674’s record-breaking speed had nothing to do with how fast the star was spinning in space, but on how quickly the light of the explosion faded. Along with other scientists, Starrfield, Woodward and Wagner feel this particular event may be able to help scientists learn more about how our own solar system came into being. Despite sounding like tetchy characters from “Lord of the Rings,” white dwarfs play a critical role in space, collecting and altering matter before surrounding itself with its new material, according to a blog post found on the official website of the Large Binocular Telescope.
“The materials ejected by novae will eventually form new stellar systems,” the post continues, which is essentially how the solar system was formed. Information about novas can help us understand the inception of such systems, and the chemical elements produced by novae exploding.
Wagner is with the Large Binocular Telescope Observatory, but an “in-kind contributor” for The Ohio State University, which is a partner in the telescope. He lives in Tucson and works closely with Starrfield, an astrophysicist at Arizona State University’s School of Earth and Space Exploration, and Woodward, a University of Minnesota professor at the School of Physics and Astronomy. Wagner and Starrfield met at ASU in the 1980s and have collaborated ever since. All three co-authored a report published June 14 confirming that nova V1674 Hercules is indeed the fastest nova ever recorded and likely occurring on a quite massive white dwarf star.
“We used a variety of telescopes in Arizona to study it early on,” Wagner said, citing Kitt Peak National Observatory in Tucson and Fred Lawrence Whipple Observatory in Amado.
Now the team is using the world’s largest telescope, located atop Mount Graham, to study the binary star, essentially the remnants of the explosion. The Large Binocular Telescope, affectionately dubbed the LBT, uses large mirrors to collect light and create an image.
Large, as in 27-feet across, Wagner added.
He would know, being involved in the inception of the Mount Graham International Observatory, located six miles south of Safford. Wagner arrived in Arizona in 1998, and was responsible to help procure the original set of instruments for the telescope. Located at 10,700 feet above sea level, the mountain rises above a good part of the atmosphere, he noted, and is a good location to capture high quality images of the galaxy.
“We started observing the nova with the LBT in September last year,” Wagner said.
“It takes about 3.7 hours for the two stars to go around each other, so if you want to study that in detail, you need to observe the star at short intervals. So at the LBT, we were running exposures every two minutes,” he added.
The remains of the white dwarf star are faint. The difference in brightness between the height of the explosion to now is about a factor of 10,000, he said.
But it’s what’s happening around it that’s fascinating, particularly, a strange wobble that’s happening every 501 seconds, roughly every eight minutes.
This very small wobble, or oscillation, is essentially a flicker of light that’s pulsing with incredible regularity: It could even be observed at the height of the outburst, which generally overpowers any nuances.
Wagner hypothesizes that a magnetic tension between the two stars may have the potential to trigger the flicker.
“That’s what we were actually trying to measure with the LBT,” he said. “The two stars going around each other.”
“The origin of the system and how it evolved is one of the key questions we would like to try to answer with the observations we’re doing now and with any future observations,” he said. “What we’re trying to do right now with the LBT is to try to understand the geometry of this system.”
While the recent report cited some discoveries about the binary star, “In many ways, it’s just the first chapter of a book we’re trying to write,” Wagner said.
But the discovery was so thrilling the cohort agreed to release preliminary gatherings.
“We may have a lot more information in six to eight months,” he said, when the group will bring their latest to the annual AAS conference in Seattle in January 2023.
“We were just getting started when this thing took off. This took off as fast as the nova did,” he said.