I’ve seen some pretty incredible things using my eyes.. First off of course, is the stunning sight of a dark star filled sky, then there is the incredible sight of the Andromeda Galaxy 2.5 million light years away. Planets too can of course be seen as they slowly move across the sky but it’s a little more unusual to see something that reminds us the Universe changes. Well, we have an opportunity in just a few weeks time. The star T Corona Borealis (T CrB) will brighten about 1,500 times so it can be seen with the unaided eye. Miss it though and you will have to wait another 80 years!
It’s always exciting to see something new in the sky. It doesn’t happen all that often but when it does, well it’s definitely an opportunity to get out and enjoy the show. The event is a nova which translates from Latin meaning new. In astronomy, we talk of nova as a number of different phenomena which herald the appearance of something new which is visible in the sky. A supernova is a well known example marking a colossal stellar explosion.
In the case of TCrB it refers to a binary star system where a white dwarf star (the remains of a star like the Sun) is in orbit around another star. I should clarify that statement, they both orbit around a common centre of gravity. At a distance of 3,000 light years, it is one of the closest of its type and so when it goes into outburst, we will get to see it without any telescope or binoculars, just the ‘Mark-1 eyeball.’
The process that leads to the sudden brightening is really quite fascinating. The white dwarf star is a much higher pull of gravity compared to its companion. As a result, it drags material from its stellar neighbour in a process known as accretion. Over time – and in the case of T CrB it takes about 80 years – hydrogen builds up on the white dwarf. The layer of hydrogen is heated up by the white dwarf causing it to heat to critically high temperatures, high enough to initiate hydrogen fusion. The layer of hydrogen detonates and gets ejected from the white dwarf in a brightly glowing, hot shell. Here on Earth, we see this as a sudden brightening of a previously rather inconspicuous star that would ordinarily need a telescope to see.
Nova are generally quite unpredictable, usually occurring once and often leading to the death of a star but in this case, it occurs every 80 years. We call this event a recurrent nova. Its outburst was first seen in 1866 by an astronomer called John Birmingham who, amusingly came from Ireland and not Birmingham. It was seen again in 1946 when there was a drop in brightness before the explosion and it is this drop in brightness that has just been observed over the last couple of months.
This all points to the next nova event being imminent, perhaps just a month or two away so, if you like me, are keen to see this once in a lifetime event then it’s time to get your coat on and get outside. Unfortunately, because we don’t know exactly when it is going to occur the best approach is to simply become familiar with the sky in the region of the constellation Corona Borealis.
Alphecca is the brightest star in a C-shaped pattern of stars: the constellation Corona Borealis. It’s near the bright star Arcturus on the sky’s dome. Credit: EarthSkyThankfully, Corona Borealis is in a fairly ‘quiet’ part of the sky with not too many bright stars. To find it from where you are then use an app on a smartphone to locate Vega in Lyra and Arcturus in Bootes, Corona Borealis is approximately between the two and looks somewhat like a semicircle of stars. Get to know that part of the sky and become familiar with the stars visible to the naked eye. Keep watching over the weeks and months ahead (and of course keep an eye on Universe Today) and at some point soon, you will see a ‘new’ star appear just outside the semicircle.
Good luck and clear skies.
Source : Keep your eyes on the sky for a new star as “once in a lifetime” cosmic explosion looms
