These days we keep hearing about “fake news.” The term even applies to the universe. Maybe fake is too strong a word. But the headline media stories that gain attention are often dismissed by actual astronomers. For example, you’ve heard “Supermoon,” but astronomers know that it’s just a catchy new term for when the Moon comes a bit closer than normal, which looks no different from any other Full Moon. Or you’ll read about an asteroid that “just barely missed Earth” while, in truth, its nearest approach was a million miles from us.
But this week, a news story really did have validity, and really does excite astronomers – even if it was duly accompanied by the mandatory exaggeration. An astronomy professor at a small Midwestern college, along with some of his students, predicted that an odd type of exploding star called a red nova would appear in our skies five years from now. It would be the first naked-eye nova in decades. And the mechanism behind it is fascinating as well.
This story really should be rewound ten years, to when several teams of astronomers closely monitored a distant star in the constellation Scorpius. This was a double star where the two components were so close together that they were actually touching, and whirling around each other every 1.4 days. What was strange is that the orbital period was rapidly decreasing, strongly indicating that the stars might actually merge. Well, it really happened: In 2008, a red nova occurred in that spot, and afterward only one star remained. The two had merged.
Actually, five years earlier, an astronomer predicted that a red nova is caused by the merger of the members of a binary star system – so the 2008 Scorpius event confirmed that theory. This week’s big news is that it’s happening again.
This time, the double star is just off the right wing-tip of Cygnus the Swan. This binary star is extremely faint – 12th magnitude – and from the way the orbit is speeding up from the current 11 hours, that Midwestern astronomer predicts that they will merge in the year 2022, give or take half a year. It will be another red nova.
Because this star system is 1,800 light-years away – which is six times closer than that Scorpius star – the nova should be bright enough to be seen with the naked eye. Of course, since the media still felt the need to exaggerate, some news stories proclaim that it will be the brightest star in the sky. While not impossible, it’s far more likely to be second magnitude: the same brightness as the stars of the Big Dipper. Still, this will be amazing, especially if you know enough backyard astronomy to recognize Cygnus’ shape and be excited by a new star that will extend its right wing. (Since some news stories are saying that it’s the Swan’s left wing, let me mention that yes, if you’re the Swan, it would be your left wing; but for us down below looking at it, it’s the wing on the right side: the wing closest to the famous bright summer star Vega.)
We’ll watch that spot every night – especially starting four years from now.
Want to know more? To read Bob’s previous “Night Sky” columns, visit our Almanac Weekly website at HudsonValleyOne.com.