Where is the Blaze Star? Why the “new star” T Coronae Borealis has not yet lit up the night sky

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The highly anticipated “guest star” of the night sky has yet to deliver his big performance – but we have an update.

For a quick recap, astronomers and stargazers have been watching the constellation Corona Borealis recently, eagerly awaiting the once-in-a-lifetime reactivation of a long-dead star in an explosion powerful enough to briefly match the brightness of Polaris, the North Star. T Coronae Borealis – often called T Cor Bor or T CrB – is home to a white dwarf, a dense, burnt-out star siphoning material from its companion star, which is a massive red giant near the end of its life. This material spirals into an accretion disk around the white dwarf, where it slowly covers the star’s surface. Every 80 years or so, the white dwarf manages to accumulate enough mass to trigger a nuclear explosion, triggering an explosion which reinforces its generally weak magnitude from 10 to a bright 2.0 — this should look like a “new star” in the night sky for us.

Astronomers’ best predictions suggest that T CrB was poised to ignite by September. Yet two months later, this elusive system continues to show signs that an explosion is still imminent. So what gives?

“We know this has to happen,” astrophysicist Elizabeth Hays, who observes T CrB every day using NASA’s Fermi Gamma Ray Space Telescope, told Space.com in a recent interview. “We just can’t pin it down to the month.”

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The unpredictability stems in part from the limited number of historical records of T CrB explosions. Only two such flares have been definitively observed in recent history: on May 12, 1866, when a star’s explosion briefly eclipsed all stars in its constellation, reaching a magnitude of 2.0, and again on February 9, 1946, when it peaked at magnitude 3.0. These events appear to follow the star’s approximately 80-year cycle, suggesting the next explosion may not occur until 2026.

However, in February 2015, the system brightened in a manner reminiscent of its behavior in 1938, eight years before its 1946 eruption. This increase in brightness suggests that the T CrB explosion was accelerated until 2023. The system also underwent a “unique and mysterious” attenuation about a year before its 1946 explosion, as well as a similar decline. started in March last yearprompting astronomers to adjust their predictions to 2024. Yet the cause of this drop in brightness before the eruption remains unclear, making it only a chance predictor.

“We were really excited when it looked like the group was doing similar things,” Hays said. “Now we’re learning, ‘Oh, there’s another room we can’t see.'”

Additionally, the rate at which material from the red giant is drawn toward the white dwarf can fluctuate over the years, making it more difficult to put a date on the timeline for the explosion, Edward Sion, professor of astronomy And astrophysics at Villanova University in Pennsylvania, told Space.com.

The white dwarf and its red giant companion are also separated by only 0.5 AU, or half the average distance between them. Earth And the sunand this proximity introduces complexities to the accretion process that are not fully understood. “There is a lot of uncertainty about the actual average accretion rate,” Sion said.

Astronomers are take advantage of this waiting period to collect as much data as possible. The last time T CrB broke out there was no x-ray or gamma rays telescopes in spacetherefore there is no data from wavelengths other than optical to shed light on what happened before the explosion. Today, the Fermi Gamma Ray Telescope is just one of many ground- and space-based telescopes closely monitoring the system. from NASA James Webb Space Telescopewith Swift, INTEGRAL and ground system Very large painting in New Mexico, are all involved in this effort.

These telescopes will not only capture the moment of the explosion as it occurs, but also track its subsequent decay into the depths of space. Astronomers say this wealth of data will allow them to better predict future explosions and will ultimately benefit models of how stars work.

“This time is really the most important,” Hays said. “We’re getting the best data set we’ve ever had of what the nova looks like before it explodes.”

Currently, astronomers are reviewing the available data, looking for any hints of an impending explosion, but “one must be careful not to overinterpret,” Hays added. “Some of the things we’re seeing change don’t necessarily have anything to do with how quickly the explosion will start – maybe just the weather in the system.”

So for now, the wait continues. T CrB is usually so faint that it is only visible through telescopes, out of reach of the naked eye. Astronomers and avid stargazers are watching it closely, ready to both marvel and catalog its eruption into the brilliant nova it promises to become.