SUNSET: 
17The nova that erupted in the Sagittarius Teapot on March 15th reached about magnitude 4.3 by March 21st. As of the morning of the 23rd it was dropping, though still easy in binoculars.
| Update April 1: On the way up again. The last week of amateur observations show the nova struggling back up to shine at about magnitude 4.8, after originally peaking at about 4.3 and declining to 6. Its spectrum has also changed in unexpected ways. See the AAVSO's up-to-date preliminary light curve. See our most recent story. |
| Update Sunday March 22: Nova Sagittarii 2015 No.2 reached about magnitude 4.3 yesterday morning and seemed about the same this morning. That's almost 2 magnitudes brighter than at its discovery a week ago. It's now the brightest star inside the main body of the Sagittarius Teapot. It looks definitely yellow to me in 10×50 binoculars. However, after gaining 0.3 magnitude per day from March 16th to the 21st, it looks like it's at a standstill or starting its decline judging by its preliminary AAVSO light curve. This seems to be the brightest nova in Sagittarius since at least 1898, and the brightest anywhere in the sky since Nova Delphini 2013 peaked that August at magnitude 4.3. Sagittarius is a little higher before dawn every morning. |
[Original story, March 16, 2015:]
You never know. On Sunday March 15th, nova hunter John Seach of Chatsworth Island, NSW, Australia, found a new 6th-magnitude star shining in three search images taken by his DSLR patrol camera. The time of the photos was March 15.634 UT. One night earlier, the camera recorded nothing there to a limiting magnitude of 10.5.
A spectrum taken a day after the discovery confirmed that this is a bright classical nova — a white dwarf whose thin surface layer underwent a hydrogen-fusion explosion — of the type rich in ionized iron. The spectrum showed emission lines from debris expanding at about 2,800 km per second.
The nova has been named Nova Sagittarii 2015 No. 2, after receiving the preliminary designation PNV J18365700-2855420. Here's its up-to-date preliminary light curve from the American Association of Variable Star Observers (AAVSO). Here is the AAVSO's list of recent observations.
Although the nova is fairly far south (at declination –28° 55′ 40″, right ascension 18h 36m 56.8s), and although Sagittarius only recently emerged from the glow of sunrise, it's still a good 15° above the horizon just before the beginning of dawn for observers near 40° north latitude. If you're south of there it'll be higher; if you're north it'll be lower. Binoculars are all you'll need.
It looks yellowish. Here's a color image of its spectrum taken March 17th, by Jerome Jooste in South Africa using a Star Analyser spectrograph on an 8-inch reflector. Note the wide, bright emission lines. They're flanked on their short-wavelength ends by blueshifted dark absorption lines: the classic P Cygni profile of a star with a thick, fast-expanding cooler shell or wind.
To find when morning astronomical twilight begins at your location, you can use our online almanac. (If you're on daylight time like most of North America, be sure to check the Daylight-Saving Time box.)
Below is a comparison-star chart from the AAVSO. Stars' visual magnitudes are given to the nearest tenth with the decimal points omitted.
Check back here for further updates!
Comments
Graham-Wolf
March 17, 2015 at 12:30 am
Yehaw
Another target for my 10x50 Binoculars... thanks S&T, for the chart and info. Was starting to miss C/2014 Q2 Lovejoy ( just too far North from here).
The Nova should be an easy binocular object from NZ in the pre-dawn eastern skies.
A bit of overkill with a large Dobbie and a SWA.
Once Cyclone PAM clears our battered shores, it should be a cinch!
Good hunting...
Graham W. Wolf
Lower Hutt, New Zealand
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Adriano-Valvasori
March 17, 2015 at 10:21 am
Thank you so much for having enjoyed my image.
Regards
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March 17, 2015 at 10:24 am
Alan MacRobert, what is that EXTRA DOT that appears when the nova is shown? It appears in the image at about the 5 o'clock position, 2/3rds of the way between the nova and the bottom of the image. Seems too bright to be filtered out of one shot but not the other, based on different magnitude threshold (there are dimmer stars in BOTH nova and pre-nova images). Maybe an artifact of a stacking algorithm gone slightly awry?
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Anthony Barreiro
March 17, 2015 at 2:09 pm
Adriano would be the best person to answer this question, but when I look at the post-nova image I see what looks like internal reflection in a roughly circular area all around the nova. The bright spot toward 5 o'clock noted by Peter is the brightest and most concentrated area. You would not need to stack images to see a sixth magnitude star through a 12-inch aperture telescope.
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Adriano-Valvasori
March 17, 2015 at 7:13 pm
The image is a single exposure of 180 seconds, to which I applied only one stretch logarithmic. I too have noticed this extra dot, but I do not know how to explain it. I had to do new shots this evening, but in Australia there is bad weather conditions. So I planned one shot for tomorrow night, March 19 (3:15 local time Australia) with B, V, I filter. Tomorrow, I will send you the new images. Regards
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Adriano-Valvasori
March 18, 2015 at 5:03 am
I have also verified on the image of Rolando Ligustri, performed in the same hours (although obtained with a different instrument) and do not see anything. Probably the one that appears in my image is a reflection.
Regards, Adriano.
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March 17, 2015 at 4:12 pm
Thank you Alan!!
Emilio Mora
Costa Rica
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Graham-Wolf
March 18, 2015 at 8:15 pm
Hi there, from New Zealand.
Great to hear the observing reports, and that more photos have been taken.
Cyclone PAM has now left our shores and I've had two quick peeks with 10x50 Binocs in the predawn skies ~ 5:30 to 6am NZDT, these last two days. It's definitely there, and still brightening! I've prepared Charts similar to that above but terrestrially orientated for the antipodes. 10df MLim 10 and 5df Mlim 12.... the latter will probably never be required to use.
Contact me at "[email protected]" if you require e-copies of my custom charts.
This morning (a few hours ago), it was headed for Mv 5.0. The AAVSO-VSP website is easy to use to find and generate your own Comparison Charts, if you so desire.
A simple Compact Digicamera (LUMIX DMC-LS 80 8Mpx) will reach Mv 6.7 in 30s at ISO 100 from an Mv 6 darksite (I've already done it). Currently using a simple CANON A480. Set to 800 ISO, and shooting at 5s, 10s, 15s.... "Goldilocks Astrophotography). Too noisy at 1600 ISO. 400 ISO also worth a try. Shoot at max MPx, THEN zoom in and crop "post exposure".
We've had strong Auroral activity here in NZ these last 3 nights. IBC1 to IBC2 rays to SW from Hutt Valley near Wellington. Displays wery strong in lower half of South Island.... Wanaka, Dunedin, Invercargill etc. Similar photography techniques apply here too (read my recent astroblog on "Sky and Telescope" Website re Aurora photography "101").
NOW... get those cameras clicking, and my very best wishes to you all, out there!.
Graham Wolf:- Lower Hutt, New Zealand.
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Anthony Barreiro
March 19, 2015 at 3:32 pm
We had very clear weather here in San Francisco last night and this morning, 19 March. Around 0550 PDT I went out with 8x42 binoculars and was able to see the nova easily. Despite the urban light pollution and the fact that I could see only the top half of the Sagittarius teapot above the roofs of the buildings across the street, the nova was unmistakably the brightest object in that part of the constellation. Woo hoo!
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Graham-Wolf
March 19, 2015 at 10:49 pm
The Nova continues to slowly brighten each day.
Conspicuous in even small binoculars from bright suburbs... from dark sites rated ZLM 6 (say a Bortle Class 2 or 3) or better and 60 deg elevations or better, it should just be naked eye with averted vision. Feeling brave... give it a go!
Took a pic this morning with my simple 10Mpx Canon A480 Compact digicamera.
From my humble suburban back-yard, with tall trees at the right hand edge.
From NZ, "Nova Sgr 2015 No 2" is a little to the right and below the tail of the Scorpion. From the Antipodes, we see and "upside down" teapot, and tghe Nova right in the middle of all that.
06:00am NZDT. 10s at ISO 800, 50mm efl, f3.0.
The nova is most certainly there in the image. Would have even got it at 400 ISO
Graham W. Wolf:- Lower Hutt, NZ.
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osoriosabas
March 20, 2015 at 5:05 pm
I have a doubt.
On tuesday march, 15th?
That date is sunday.
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March 20, 2015 at 5:10 pm
Just one small typo - the first line says Tuesday March 15th but that was actually a Sunday.
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Drsaguirre
March 20, 2015 at 6:08 pm
Hi Everyone.
My last magnitude estimate (Naked Eye)= 4.60
here my images and photometry Vis.
http://goo.gl/tdxZgS
Best Regards
Salvador Aguirre
Mex.
AAVSO (ASA)
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Peter Wilson
March 21, 2015 at 10:03 am
Monday saw it with 7x50s and averted vision. Clouds and rain. This morning saw it unaided from front-porch in Phoenix.
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StarChaser55
March 22, 2015 at 7:40 am
After a week of cloudy mornings it finally cleared here in the Davis Mountains; saw Nova Sagittarii 2015 No. 2 unaided as soon as my eyes dark-adjusted. A beautiful "new" star in the heavens!
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Ted-Hauter
March 22, 2015 at 5:12 pm
Whats going on lower middle right in the image? Lens flare?
Can't wait to see this, but I fear I am too late. Not headlining news here on the website and just now found it.
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Graham-Wolf
March 24, 2015 at 3:02 am
Brightness decline confirmed this morning, from Lower Hutt, New Zealand. Skies cleared after 2 days of scattered showers, to present a clear sky at about 3am NZDT today. Nova also looks somewhat yellower in 10 X50s and 10 X 70's as others have commented. So, I'm not goiung cvolour-blind after all. It appears to be past it's peak now, but still worth visually following. The nova's at over 40 deg elevation locally at 6am NZDT, with about 10 minutes to go to dawn onset. Lucky me!
Don't forget April 4th's midnight Total Lunar Eclipse, if you live in the Antipodes. A nice little Easter "present" from our friendly solar system (so THAT's why they call it "Good Friday")!!.
Graham W. Wolf:- Barber Grove Observatory.
Lower Hutt, New Zealand. Vaklley
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