I have seen some incredible things with my own eyes. First, of course, there is the stunning view of the dark starry sky, then there is the incredible view of the Andromeda Galaxy, 2.5 million light years away. Of course, planets can also be seen moving slowly across the sky, but it’s a bit unusual to see something that reminds us of changes in space. We have an opportunity in just a few weeks. The star T Corona Borealis (T CrB) brightens about 1,500 times, so it can be seen with the naked eye. But don’t miss it and you’ll have to wait another 80 years!
It’s always exciting to see something new in the sky. It doesn’t happen that often, but when it does, it’s definitely an opportunity to get out and enjoy the show. The event is nova, which means new in Latin. In astronomy, we talk about a nova as a number of different phenomena that herald the appearance of something new that is visible in the sky. A supernova is a well-known example of a colossal stellar explosion.
In the case of TCrB, this refers to a binary star system where a white dwarf (the remnants of a star like the Sun) orbits another star. I should qualify that statement, they both orbit a common center of gravity. At 3,000 light-years away, it’s one of the closest of its kind, so when it explodes, we’ll see it without binoculars or binoculars, just “Mark-1 eyeballs.”
The process that leads to the sudden brightening is really quite fascinating. A white dwarf has a much higher gravitational pull compared to its companion. As a result, it pulls material away from its stellar neighbor in a process known as accretion. Over time—and in the case of T CrB it takes about 80 years—hydrogen accumulates on the white dwarf. The hydrogen layer is heated by the white dwarf, causing it to heat up to critically high temperatures, high enough to initiate hydrogen fusion. The hydrogen layer detonates and is ejected from the white dwarf in a brightly glowing, hot shell. Here on Earth, we see it as a sudden brightening of a previously rather inconspicuous star that would normally require a telescope to see.
Novas are generally quite unpredictable, usually occurring once and often leading to the death of a star, but in this case it happens every 80 years. We call this event a recurring nova. Its outburst was first seen in 1866 by an astronomer named John Birmingham, who, amusingly, was from Ireland and not Birmingham. It was seen again in 1946 when there was a decrease in brightness before the explosion, and it is this decrease in brightness that has just been observed during the last few months.
All of this points to another nova event coming up, maybe in a month or two, so if you like me you want to see it once in a lifetime, then it’s time to put on your coat and get out there. Unfortunately, since we don’t know exactly when it will occur, the best approach is to simply familiarize yourself with the skies in the region of the Corona Borealis constellation.
Fortunately, Corona Borealis is in a relatively “quiet” part of the sky with not very bright stars. To find it from where you are, use a smart phone app to find Vega in Lyra and Arcturus in Bootes, Corona Borealis is roughly between the two and looks a bit like a half circle of stars. Get to know this part of the sky and get to know the stars visible to the naked eye. Keep an eye on the following weeks and months (and, of course, watch Universe Today) and at some point soon you’ll see a “new” star appear just beyond the semicircle.
Good luck and clear skies.
Source: Keep your eyes on the sky for a new star as a ‘once-in-a-lifetime’ cosmic explosion appears