The star system 3,000 light-years from Earth will soon become visible to the naked eye in the night sky. For most of us, it will be the first and last opportunity to see this nova, as it explodes approximately every 80 years.
The reappearance of T Coronae Borealis
Also known as T CrB, it is a “new” option. This “nova” is a cataclysmic nuclear explosion in a star, caused by the accretion of hydrogen to the surface of a white dwarf, leading to ignition and initiating nuclear fusion. Novas should not be confused with supernovae or red luminous novae.
This one that we will now witness, was discovered during its occurrence in 1866. It rekindled again in 1946, when we saw it for the last time without the help of a telescope.
Due to its recent activity, astronomers believe that will do it again this year, somewhere between now and September. Once peak brightness is reached, it will be visible to the naked eye for several days (and up to a week with binoculars) before dimming again for another 80 years.
T CrB is a binary star system consisting of a red giant and a white dwarf that orbit around each other at close range. Although smaller, the white dwarf is extremely dense and hot, meaning it attracts material from the red giant's outer layers, mainly hydrogen.
As mentioned, as the accretion disk (the material that accumulates around the white dwarf) grows, the pressure and temperature increase, triggering an explosive thermonuclear reaction. This reaction releases an enormous amount of energy in a short space of time, causing a sudden glow in the cosmos.
From our perspective, the event is similar to a new star that temporarily appears in the sky, reason why we call it a new. As reinforced above, we cannot confuse it with a supernova, as this is a much more energetic explosion, in which a star collapses.
How can we see it in the night sky?
AT CrB is normally magnitude +10, which is too faint to be seen with the naked eye, but its light will reach us at magnitude +2 during the explosion, a brightness similar to that of the polar star.
The apparent magnitude is a logarithmic scale, and decreases as the star's brightness increases. The brightest white star, Sirius, has a value of -1.5.
To find the nova in the night sky, you'll have to look at Corona Borealis, a small arc-shaped constellation near Hercules and Boia. You can find it with a stargazing app, such as SkyView Lite: which is available for Android and iOS.
T CrB is just one of five new and recurring ones in our galaxyalong with RS Ophiuchi, V1500 Cygni, V838 Monocerotis and V339 Del, discovered in 2013.
