Astronomers predict a new naked-eye star will emerge in the night sky in 2024. While it may be new to you and me, the fresh point of light is actually a recurrent nova, having been recorded in 1866 at mag=2 and in 1946 at mag=3. I encourage you to photograph that part of the sky now with a good cell phone camera, so when the nova comes again (soon) you'll be one of the few people with before-and-after photos of this sudden news story.
While astronomer Jim Kaler anticipated it reappearingin 2026 after another 80-year cycle, recent observations suggests we'll have a summer 2024 interloper instead, as explained in the opening story of this Space Bites by Fraser Cain.
The ancient star, named T Coronae Borealis, is actually a closely bound pair of stars, with the gravity of one massive white dwarf ripping off the outer layers of its less-dense yet larger companion star, a red giant star. Eventually a critical mass accretes around the white dwarf and it emits a mighty outburst. T Cor suddenly becomes 1,500 times brighter, approaching mag=2, about as bright as the north star Polaris. You can see it naked-eye. Within a few days or weeks it retreats back into the darkness.
For me the beauty of T Cor isn't so much the visibility of the star itself as the predictive nature of science. I recommend you learn to find the constellation Corona Borealis, then take some pictures with a newer cell phone camera. When T CrB blows, take some more photos of the same area. Revel in seeing it naked-eye, but also compare before and after to reveal the nova in photos.
On June 15, 2024, despite moonlight and wispy clouds, I took some twilight photos of the southwestern sky. I hope to take more when the sky is clear and darker. It's amazing how well a newer phone captures stars with a 3-second exposure. Hold still.
From the curved handle of the Big Dipper, "follow the arc to Arcturus," the bright yellowish star in the constellation Bootes. It looks like a kite with a short tail, or an ice cream cone. Next to Bootes is Corona Borealis, the northern crown. The bright central star Alphecca is also known as Gemma, the gem star in the crown. Keeping with the summer theme, you could consider Corona Borealis a cup into which you could put a scoop of ice cream.
Zoom in on the crown. Sure enough, even in twilight the camera picks up seven main stars.
When you hear in the news that a nova has appeared in the night sky, go back out and re-image Corona Borealis. Did you get it? Here's a zoomed star chart to help confirm.
Jim Kaler further describes T Coronae Borealis, including an extreme case of its mass exceeding a tipping point:
...The "recurrent nova" T Coronae Borealis...is one of only eight known. Normally of tenth magnitude, T CrB consists of a class M3 giant in a 227-day orbit with a massivewhite dwarf. Tidally distorted by its companion (and thus variable as it presents different-sized cross-sections with different temperatures to us), the giant feeds matter onto the white dwarf (at a rate close to a million times that of the solar wind). When the layer of fresh hydrogen is sufficiently great, the heat of compression causes the layer to blow up like a hydrogen bomb. Normalnovaeare made of lower mass white dwarfs that feed off low mass ordinary dwarfs, and after the new layer is thick enough, should pop off every few tens or hundreds of thousands of years. But T's white dwarf is so massive that the intervals between explosions are short. In 1866 the star hit magnitude 2, and in 1946 mag 3, taking but a few days to drop back to invisibility. Are we due for another blowup around 2026? Nobody really knows, but keep your eye on Epsilon. The event could be far grander. The accreted matter could push the white dwarf over the fabled 1.4 solar mass limit, beyond which the WHOLE STAR would collapse and blow up in a grand(Type Ia) supernovathat -- even at a distance of 2500 light years -- could become as bright as a crescent Moon!
