January Night Sky
Sky events for this month & objects for observation can be found here.
Courtesy of Orion Telescopes & Binoculars
Click to enlarge. A larger printable version of this chart can also be found here.
ORION NOT QUITE THE SAME
The circled-dot star chart symbol for Betelgeuse indicates Alpha Orionis is a "variable star" with known changes in brightness.
The constellation Orion is one of the most widely known and beloved in the sky, and most prominent during the long northern hemisphere winter evenings.
Alpha Orionis – the shoulder of the constellation Orion the Hunter – is one of the easiest to recognize stars in the night sky, and has a distinctively orange-red tint. Commonly known as Betelgeuse – it’s also called a Red Supergiant and one of the largest stars we know, with a radius which would extend out beyond the distance of Mars’ orbit from our Sun. In recent weeks, this bright star has become noticeably fainter.
Could this be a sign that Betelgeuse is about to explode as a supernova? Astronomers say probably not. Betelgeuse is a well-known semiregular variable star, and its changes in brightness have been monitored for years by amateur and professional astronomers working with the American Association of Variable Star Observers (AAVSO). We therefore know that there are multiple cycles for Betelgeuse’s rising and falling brightness. When the minimums of all the cycles become momentarily synchronized the star could look unusually faint, as it currently does. But the fact remains Betelgeuse is now dimmer than it has been anytime in the recent past.
As seen in the left picture, Betelgeuse (arrow right pane) usually rivals Rigel (arrow left pane). The right picture on Dec 22, 2019 by Bob King shows how unusually dim Betelgeuse has become.
And of course in this day and age things often are sensationalized, which has caused some speculation that Betelgeuse could be about to go supernova. However, Astronomers say this is unlikely any time in the next 100,000 years. What are some other possibilities for Betelgeuse’s strange and dramatic dip in brightness? Astronomers suggest that the change in brightness could be due to the changes in the layers of gases expelled by and surrounding the star.
What would happen if Betelgeuse were to explode? While Betelgeuse isn’t among our closest stellar neighbors, it is normally one of the brightest stars in Earth’s sky. The reason is that Betelgeuse is a supergiant star, and it is by nature very brilliant – 90,000 to 150,000 times more luminous than the Sun. Such luminosity comes at a price. Betelgeuse’s tremendous energy output requires that its fuel be expended relatively quickly, and in fact Betelgeuse is now near the end of its lifetime. Sometime in the future it will essentially run out of fuel, collapse under its own weight, and then rebound in a spectacular supernova explosion. When this happens, Betelgeuse will brighten immensely for a few weeks or months, perhaps to be as bright as the full moon and even visible in broad daylight. While Betelgeuse is “nearby” in relative terms, it’s still some 720 light-years from Earth, and there would be little if any direct effect on the Earth.
So while Betelgeuse has become noticeably fainter in recent months, does that mean it’s about to explode? Probably not… But it is nice to speculate about what that would actually look like!
