Strange Quarks

T Corona Borealis — T CrB for short — is one of ten known recurrent novae. At a distance of around 3000 light years, it was first discovered as a nova eruption in 1866 by John Birmingham. Outbursts occur approximately once every 80 years. It may have been observed in 1217 and in 1787 as well.

T CrB is expected to explode again this year reaching naked eye visibility, around magnitude 2 or 3. The last outburst was in 1946. As always when we talk about astronomical objects, these events happened long ago, 3000 years ago in this case, with the evidence only expected to reach us this year due to the speed of light.

This is likely to be the brightest nova of a generation, certainly of the known recurrent novae. It will quickly rise from a visual band magnitude of 9 or 10 within a day or two to become visible to the naked for a few days, remaining a binocular object for a week or thereabouts, then returning to its pre-eruption magnitude within a month or so.

Exactly when it will brighten is uncertain and is discussed by nova expert Brad Schaefer and others in this AAVSO article, but the prediction is 2024.4 +/- 0.3, so May or June, but it could be earlier or later.

There was a pre-eruption dip in the light curve, 1.1 years before the 1946 outburst. A similar dip happened in March 2023 as shown in the last two years of T CrB observations in V and B bands, more prominent in the B band.

T CrB is located low in the north-eastern sky from Adelaide starting in the late evening. This Stellarium screenshot shows the circumstance for Apr 8 at midnight when T CrB is around 15 degrees above the horizon. Waiting an hour or two will help make observing easier with T CrB culminating at around 29 degrees above the horizon, but the region is viewable from around 11:30pm with a clear NE horizon.

This unprocessed, untracked image was taken with my DSLR (Canon 1100D, 100mm lens, f2.0, ISO 100, 10 secs) on Apr 7 at 2am, so it’s a little further rotated anti-clockwise than the Stellarium view above. The red arrow points to where T CrB will become visible and the green arrow points to alpha CrB (Alphecca). This shows the bright stars of the constellation of Corona Borealis.

Here is an AAVSO finder chart, with stars only down to magnitude 5. You’ll need to rotate it slightly clockwise to match the views above.

The comparison star marked 22 is the magnitude 2.2 star Alpheccca (alpha CrB). Izar and Arcturus (epsilon and alpha Bootis) do not appear in this finder chart, and are at upper left of the constellation Corona Borealis in this orientation. T CrB may approach Alpheccca in brightness.

I’ll be looking out for T CrB whenever I can stay up late enough or get up early enough until the outburst happens, using just the unaided eye in the first instance. Once visible in outburst, I’ll make estimates with 7×50 binoculars and time-permitting, DSLR images for subsequent photometry, submitting both to the AAVSO International Database.

Messages will also be posted on the AAVSO nova forum when the T CrB outburst happens.

This entry was posted on April 7, 2024 at 10:01 pm and is filed under Astronomy, Variable Stars, VStar. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.