Can you find a ‘New Star’ in the Sky?

Illustration credit: NASA Goddard Space Flight Center

If you haven't already, soon you may see predictions of a star suddenly brightening in our night sky, a 'nova'. Discover how you can see it, what to expect, and what a nova is.

The star is called T Coronae Borealis (TCrB), in the constellation of Corona Borealis, the Northern Crown. This constellation is visible in the evening sky during spring through mid-autumn. Right now, TCrB is far too dim to see with the naked eye. Even under great conditions, it's possible, if difficult, to spot it with a good backyard telescope. But sometime between now and September 2024, astronomers predict it will, for just a few days, shine as brightly as estrella polar, also known as the North Star.

Regular readers of our monthly star chart will know that the North Star itself is far from the brightest star in the night sky. So, ignore any claims that this nova will 'light up the sky'. It's not going to be that bright, and unless you're looking for it, you won't notice it. Even if it's not the most brilliant sky event ever, it's a rare and unique sight you may just want to look for.

How to find TCrB

Download and print our star chart and get a red flashlight so you can read the chart without disrupting your night vision. Have some paper and a pencil handy so you make a sketch of the constellation and the stars around it.

Most of the stars we are looking for are faint - so make sure you're looking at a dark sky away from city light pollution and shield yourself from any nearby bright sources of light. It may take a little time for your eyes to adjust to the dark to see as many stars as possible.

Astronomers often use a technique called 'star-hopping' to find their way to specific objects in the night sky. Start with the Big Dipper, high in the northwest. Find the curved handle of the Dipper and follow that arc until you find the bright orange-yellow star Arcturus, which is the single bright star of the constellation Boötes the Herdsman.

Boötes may not look much like a herdsman, but he looks similar to an ice cream cone to our eyes.

Look off to the east of the ice cream cone for a little half-circle of stars. It looks like a scoop of ice cream that fell off the cone - that's Corona Borealis. Off the east end of that curve is where TCrB sits, waiting to brighten.

Keep an eye on websites like astronomy.com, skyandtelescope.com, o earthsky.org for news. Once you hear that the nova has begun, go back outside on a clear night and bring your previous sketch with you. Compare what you see with your sketch. This new star should be easy to find now that you've familiarized yourself with Corona Borealis.

Let's hope for good weather while the star is bright, because it may only last a few days, maybe a week, before it fades again.

What is a nova and how do we know it's about to shine?

Despite the similar name, don't confuse a nova with its more powerful cousin, the supernova. In a supernova, a giant star runs out of fuel, collapses, and then explodes in a violent burst of energy and light.

What happens in a nova? Imagine two stars in close orbit of each other. In this case there's a small, dense white dwarf star and a red giant star. As the red star loses matter from its outer layers, the white dwarf star collects it with its own gravity. Over time, the white dwarf steals more and more matter from the red giant, and it becomes hotter and hotter. Eventually, the white dwarf gets hot enough that a thermonuclear reaction starts, causing a sudden brightening of the star. Over time the white star cools off again, fading back to its normal brightness.

TCrB is a recurring nova, meaning the nova happens periodically over time. Its outbursts have been most recently seen in 1866 and in 1946, but it may have been spotted as early as the year 1217. Just before the 1946 eruption, astronomers noticed a slight decrease in brightness in the star. That same decrease in brightness is happening now, leading astronomers to think a nova is imminent.

Keep an eye out for news about the nova, and see if you can spot it!

Ready to learn more about astronomy? See Vision nocturna this month in the Sudekum Planetarium for an up-to-date record of everything visible in the night sky.