T Coronae Borealis: The "Blaze Star"

For stargazers and astronomers alike, 2024 offers a rare celestial event that occurs only once every 80 years. A star system known as T Coronae Borealis, or the “Blaze Star,” is primed to explode in a recurrent nova. This event will be bright enough to see with the naked eye, offering a unique opportunity to witness the dynamic nature of our universe from your own backyard.

Understanding the "Blaze Star" Phenomenon

T Coronae Borealis (T CrB) is not a single star. It is a binary system located approximately 3,000 light-years from Earth. The system consists of two stars locked in a dangerous gravitational dance:

  • A White Dwarf: A dense, dead remnant of a star roughly the size of Earth but with the mass of the Sun.
  • A Red Giant: A dying star that is bloating and shedding its outer layers.

The mechanics of this explosion are distinct from a supernova, which marks the death of a star. In this case, the red giant is constantly dumping hydrogen gas onto the surface of the white dwarf. As this material accumulates, the pressure and heat rise to critical levels. Eventually, this triggers a thermonuclear runaway reaction on the surface of the white dwarf.

This reaction causes the “nova,” a massive burst of light that travels across the galaxy. Because the stars survive the explosion, the process resets and begins again. This cycle repeats roughly every 80 years, which is why T CrB is classified as a “recurrent nova.”

Historical Context and Prediction

The predictability of T Coronae Borealis is what makes this event so exciting for NASA and the American Association of Variable Star Observers (AAVSO). We have concrete records of its previous major eruptions:

  1. The 1866 Eruption: This was the first time the star was scientifically identified as a variable star.
  2. The 1946 Eruption: This event confirmed the recurring nature of the system.

In both historic instances, the star displayed a specific behavior before blowing its top. About a year prior to the eruption, the star’s brightness dimmed noticeably. In early 2023, astronomers observed this exact “pre-eruption dip” in T CrB. Based on the timing of the 1946 event, the data suggests the next explosion is imminent and could occur before the end of 2024.

How to Locate T Coronae Borealis

You do not need expensive equipment to see this event at its peak. When the nova occurs, T CrB will jump from a magnitude of +10 (invisible to the naked eye) to a magnitude of +2 or +3. This is roughly the same brightness as Polaris (the North Star).

To find it, you need to locate the constellation Corona Borealis, also known as the Northern Crown. Follow these steps:

  1. Find the Big Dipper: Use the handle of the Big Dipper to “arc to Arcturus.” Arcturus is a very bright orange star in the constellation Boötes.
  2. Locate Vega: Look for Vega, the brightest star in the constellation Lyra.
  3. Look Between Them: Corona Borealis lies along an imaginary line between Arcturus and Vega. It appears as a small, distinct semi-circle or “C” shape of stars.

Currently, this semi-circle looks incomplete to the naked eye. When the nova erupts, a “new” bright star will appear in the constellation, temporarily completing the crown shape.

What to Expect During the Event

Speed is a factor here. Unlike comets that hang in the sky for weeks, the peak brightness of a recurrent nova is fleeting.

  • The Rise: The star will brighten rapidly, reaching peak visibility within hours of the eruption starting.
  • Peak Visibility: T CrB will likely remain visible to the naked eye for slightly less than a week.
  • The Fade: After a few days, it will dim effectively becoming visible only with binoculars.
  • Return to Normal: After a few weeks, it will fade back to its standard magnitude of +10, requiring a telescope to see.

Because the window is short, astronomers advise checking the sky nightly or setting up alerts from astronomy apps like Stellarium, SkyView, or Star Walk 2. NASA’s Marshall Space Flight Center also provides updates via their social media channels.

The Science of Viewing

While the explosion is violent, viewing it is safe. The system is too far away to affect Earth physically. The light you will see actually left the star system 3,000 years ago, during the Iron Age, and is only just reaching us now.

Spectroscopy (analyzing the light spectrum) during the eruption will tell scientists more about how material moves between the red giant and the white dwarf. This data helps refine our understanding of stellar evolution and the accumulation of matter in binary systems.

Frequently Asked Questions

When exactly will the explosion happen? Astronomers cannot give an exact date. Based on the “dip” observed in 2023, the window is open now through late 2024. It is a waiting game.

Do I need a telescope to see it? No. At its peak brightness, it will be as bright as the North Star. You will be able to see it from most locations, even those with moderate light pollution. However, a pair of standard 10x50 binoculars will provide a much better view as it begins to fade.

Where in the sky should I look? Look for the constellation Corona Borealis. It is a small C-shaped curve of stars located between the bright stars Arcturus and Vega.

Has this star exploded before? Yes. T Coronae Borealis is a recurrent nova. Major eruptions were recorded in 1866 and 1946. This 80-year cycle makes it one of only ten known recurrent novae in our galaxy.

Is this a supernova? No. A supernova destroys the star. A nova is a surface explosion on a white dwarf. The star system survives this event and will likely explode again in roughly 80 years.