The shape of a star system located 3,000 light-years from Earth will soon be visible to the naked eye in the night sky. For most of us, this will be the first and last chance to see this nova, as it explodes approximately every 80 years.
The rediscovery of T Coronae Borealis. T CrB for friends, was discovered during its nova event in 1866. It exploded again in 1946, the last time we saw it without the aid of a telescope.
Given its recent activity, astronomers believe that will happen again this year, sometime between now and September. Once its brightness reaches its peak, 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.
Why does this happen? T CrB is a binary star system consisting of a red giant and a white dwarf orbiting each other at a short distance. Although the white dwarf is smaller, it is extremely dense and hot and therefore attracts material from the outermost layers of the red giant, mainly hydrogen.
As the accretion disk (the material accumulated around the white dwarf) grows, the pressure and temperature increase, triggering an explosive thermonuclear reaction. This reaction releases a huge amount of energy in a short period of time, causing a sudden glow in the cosmos.
From our perspective, this event resembles a new star temporarily appearing in the sky, which is why we call it a nova. A supernova, on the other hand, is a much more energetic explosion that causes a star to collapse.
How to see it in the night sky. T CrB is normally magnitude +10, too faint to be seen with the naked eye, but its light reaches us during a flare at magnitude +2, a brightness similar to that of the North Star. Apparent magnitude is a logarithmic scale and decreases with increasing star brightness. The brightest white star, Sirius, has a magnitude of -1.5.
To find a new moon in the night sky, you need to look toward Corona Borealis, a small arcuate constellation near Hercules and the Mountain Dog. You can find it using a stargazing app. T CrB is just one of five recurring novae in our galaxy, along with RS Ophiuchi, V1500 Cygni, V838 Monocerotis and V339 Del, discovered in 2013.
Image | NASA/Goddard Space Flight Center
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