A nova in Sagittarius, discovered a few nights ago by a Japanese amateur, has become bright enough to see in binoculars.
|Update: As of October 31st, the nova had been holding at about magnitude 8.0 for a week. It's temporarily designated TCP J18102829-2729590.
This is not to be confused with another nova just above the spout of the Sagittarius Teapot! The new one, temporarily named ASASSN-16ma, was discovered five days later on October 25th. As of October 31st it was about magnitude 9.7 and perhaps still rising. Expect an article by Bob King shortly.
Just in the nick for time — at least for northern observers — a bright nova has been discovered in Sagittarius. I say "nick of time" because the constellation is sinking in the southwestern sky right after dusk, affording only a short viewing window from mid-northern latitudes. But a window it is, and there's still time to snatch a view of this amazing stellar explosion. Just make sure to look right after the end of twilight. That means about an hour and a half after your local sunset time.
Well-known nova hunter Koichi Itagaki of Japan nabbed the "new star" on October 20th, using a 180-mm telephoto lens to take sky-patrol photos. At the time it was only about 11th magnitude. But within two days, the star shot up an additional three magnitudes and now shines brighter than 8.0. That puts it within range of 50-mm binoculars and any telescope you might have.
Get out early for the best views. First, locate Sagittarius in the southwestern sky using Mars as your guide. Then focus on the two stars at the end of the spout and use the maps above to track your way through a dense Milky Way field to pinpoint the nova. Work step by step; it may take some time. It is Sagittarius after all, a constellation known for its stellar throngs.
All classical novae are close binary stars with a compact white dwarf stealing hydrogen from its companion. The gas ultimately funnels down to the surface of the dwarf, where its piles up on the star’s surface. It becomes compacted by gravity and heated until hydrogen fusion ignites. The layer explodes like a hydrogen bomb in the shape a thin shell enclosing the star. This is what you see when you look at a nova – a gigantic bomb going off! The underlying white dwarf survives intact, and begins accreting a new, fresh layer that will eventually explode again.
Material gets blasted into space at tremendous speeds of some 3,000 kilometers per second (6.2 million mph). A faint, unnoticed star brightens 50,000 to 100,000 times in a matter of hours, becoming luminous enough for someone back here on Earth to spot it in binoculars over the trees. Simply remarkable.
You can keep track of what the nova's doing night to night by visiting the American Association of Variable Star Observers (AAVSO) website and entering its temporary name, TCP J18102829-2729590, in the Pick a Star box. You then have options to check recent observations, plot a light curve of them, or create a chart of your own. More details, including recent magnitude estimates, can be found in the AAVSO's Alert Notice for the nova. Click here to download an AAVSO chart with magnitudes, so you can track the star's changing brightness.
Good luck and let us know how the nova's doing! I can't wait to see it myself tonight.