8th-magnitude Nova in Sagittarius

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.

Look What the Pot Cooked Up

This map shows the sky facing southwest in late twilight for observers across the central U.S. and southern Europe. The 8th-magnitude nova (exaggerated here!) lies just above the spout of the Sagittarius Teapot, at right ascension 18h 10m 28s, declination –27° 29′ 59″.  It has been temporarily dubbed TCP J18102829-2729590 accordingly.

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.

A Deeper Look

I've labeled the two bright 'spout stars' in this more detailed map, which shows stars to about magnitude 9.5. This will get you very close. To continue to the nova, use the more detailed chart below.

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.

Nova by Way of Dolphin and Triangle

Use this final chart, which shows stars to about magnitude 10.5, to arrive at the nova. I've labeled a couple suggestive asterisms you can look for that will help you get there. North is up. 

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.

Takes Two to Tango

Novae occur in close binary systems where one star is a tiny but extremely compact white dwarf star. The dwarf pulls material into a disk around itself, some of which is funneled to the surface and ignites in a nova explosion.

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.

28 thoughts on “8th-magnitude Nova in Sagittarius

  1. Graham-Wolf

    Thanks Bob.

    Heard about it just yesterday.
    It’s definitely observable here at 46 South, NZ, and not too far from Comet 29p/SW1.
    Suggesting that 29p/SW1 comet observers, also swing their scopes etc, across to the Nova and “clock it”, too. Two visual trophies for the price of one…

    You should have NO trouble picking it out, Bob. Good luck!

    Graham W. Wolf:- NZ

    1. Bob KingBob King Post author

      Great to hear it, Joe. I managed to get out just in time here tonight and also caught the nova. Through the scope it appeared red. Using an AAVSO chart, I estimated magnitude +7.9. Brightest nova in a while.

  2. SNH

    Sweet! Another Sagittarius nova!! I wish I would have caught your article last evening though when I was out observing. That’s okay because I can set up again today or observe the nova in binoculars. Awesome! I look binoculars objects. Keep me posted.

      1. Bob KingBob King Post author

        Science Kid,
        You can ready my response to DirtyLens. Also keep this in mind: the nova will return to the morning sky eventually and be visible for a long time though of course it will probably have faded a good amount.

    1. Bob KingBob King Post author

      Dirty Lens,
      That depends on your where you live, your latitude. If you live in the southern U.S., you’ll be able to view it for another 4 weeks or so. If in the northern U.S., about two weeks.

  3. Dave-MitskyDave-Mitsky

    I was torn between watching the World Series game and giving TCP J18102829-2729590 a shot tonight.  I decided to travel to the Naylor Observatory and listen to the game on the radio.  The conditions were fair to mediocre.  After a lengthy search using the 17″ f/15 classical Cassegrain and its 5″ f/5 finder scope, I was able to find the “Dolphin” asterism mentioned in the article and locate the nova.  The “new” star was quite low in a murky southern sky but the narrow trapezoid shape it forms with three nearby field stars was unmistakable.  I observed the nova using 162, 185, 216, and 259x.

    Two fellow ASH members who just happened to stop by briefly got to see the nova too.

    1. Bob KingBob King Post author

      You made the perfect choice. It’s a pity the nova’s so low for northern mid-latitude observers, but at least we have at least a small viewing window.

  4. Graham-Wolf

    Hi Bob

    Back last weekend from several days away at an AGM ~1,000km North, in the capital. 2 beautifully clear “planetarium skies” in a row, down here at 46 South. Saw the Nova both times, easy in 7 x50 Binocs, after dark-adaptation. Great article, and nice finder charts. Used my own custom generated charts from the AAVSO-VSP website for Mv estimates. ZLM + 6.2 in my brother’s backyard, early this morning, for example (NZDT). My T.A. variable star section colleagues in the UK, are well to this. Keep up the great work, Bob!.
    Graham Wolf at 46 South, NZ.

    1. Bob KingBob King Post author

      So glad you’re able to continue observation of the nova. It’s been cloudy during evening hours 7 days in the row and counting at my location! My last and only observation was made on Oct. 23. I’m eager to see it again. Did you notice any color? It was red in my 10-inch at low magnification.

  5. Bob-PatrickBob-Patrick

    Bob King:

    Great article. Finder charts are excellent, as already mentioned in the above comments. I found the binary star explanation of novae, and the NASA graphic, to be very helpful.

  6. Tom-Laskowski

    We had a very brief clear window last night so I walked over to a nearby park where I had a good view of the SW. There was a large clear area centered on the southwest sky and I was able to easily see the nova using 15×75 binoculars. This was about 8:10 pm just after it got dark enough and before the nova got too low. Shortly afterwards the clouds moved back in. Then I got to see the Cubs win game 5 of the World Series. A good night overall.

    1. Bob KingBob King Post author

      Sounds idyllic. Yours was the first news I got of the Cubs winning. BTW, there is another even more recently discovered nova only a few degrees east of this one. Not as bright (about 10 mag.) but still easy in a small scope. To make a chart, go to aavso.org and type PNV J18205200-2822100 into the Pick a Star box.

  7. Tom KelloggTom Kellogg

    Thanks for the excellent article and finder charts. Tonight is the first clear night and I easily found it in my 13″ Dobsonian on the sidewalk in front of my home in San Francisco and shared the view with 2 women who stopped to look through my telescope. San Francisco Sidewalk Astronomer Tom Kellogg

  8. Graham-Wolf

    Hi Bob.
    Only saw the Sgr Nova later in the month, so no red colour as I remember. You have apparently seen it very soon after primary outburst.
    I do recall the almighty SN1987A (Feb 24th, 1987) was Mv 5.2….. Colleague Albert Jones found it 3/4 hr later, up near the Tarantula Nebula at Mv 4.7, It was red for both of us (I barely recall), then changed colour over the following weeks…. maybe, this one will do likewise.
    Thanks Bob, for the “heads-up” on the 2nd nova only a few more degrees away in Sgr!
    Will have a peek at that one too!
    Awesome work, Bob.
    Graham Wolf at 46 South N.Z.

  9. Bob KingBob King Post author

    Good luck on that second nova, Graham-Wolf. About SN1987A — I was chomping at the bit to get down to the southern hemisphere for that one. Wish I would have but just didn’t have the wherewithal at the time.

  10. George Gliba


    It looks like after being at a plateau, that the brighter nova in Sagittarius may be starting
    to fade. I was it at 8.3 last night, and I saw it at 8.1 two night before that. I will Keep on
    watching. I will soon loose it as it is going lower each night from here.

    Starry Skies,
    Screech Owl Hill Observatory

  11. George Gliba


    I saw the brighter nova in Sagittarius fade from magnitude 8.1 on November 2nd to 8.9 this evening.
    So, the Fireball Plasma is starting to cool…

    Starry Skies,
    Screech Owl Hill Observatory

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