Ephemeris: 06/24/2024 – Waiting for a bright nova*

This is Ephemeris for Monday, June 24th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32, and it will rise tomorrow at 5:58. The Moon, 3 days past full, will rise at 12:09 tomorrow morning.

The small constellation of Corona Borealis, or Northern Crown appears about a third of the way between the bright star Arcturus, high in the south and the star Vega in the east. It is a small semicircle of stars with the brighter star called Alphecca near the center of the arc of stars. Sometime this year, we hope, another bright star will appear there. A nova of a dim star brightening about 1,600 times normal near that circle of stars. It has done it before. It has the designation of T Coronae Borealis (T CrB for short), and is a recurrent nova of a white dwarf star that suffers an explosion about once every 80 years. So this year we need to be looking out for that stellar explosion, which will be bright for only a few days, so one must be vigilant to spot it.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

* The word ‘nova’ comes from the Latin Nova Stella, meaning New Star.

Addendum

Putting Corona Borealis in context with the Big Dipper, to the upper right, looking overhead while facing south, at 11 pm in late June. Created using Stellarium and GIMP.

This animated GIF shows the constellations of Hercules, Corona Borealis and Boötes from left to right. Flashing on and off is T Coronae Borealis (T CrB). It is shown at its approximate maximum brightness, about the same as Alphecca (spelled Alphekka here). Created using Stellarium and GIMP.

Light curve for Nova Cygni 1975 (V1500 Cyg) which burst forth in the constellation of Cygnus the Swan in August of 1975, just two months after the beginning of the Ephemeris program. There hasn’t been a brighter one since. Notice the initial sharp rise and initial decline. Magnitudes (Mag on the vertical axis) work like golf scores or prizes, the brighter the star the lower the magnitude number. The dimmest star visible to the naked eye is about 6th magnitude. You can blame Hipparchus for that numbering scheme.

NASA has post about T CrB here: https://www.nasa.gov/centers-and-facilities/marshall/nasa-global-astronomers-await-rare-nova-explosion/