Explanation: Using a small telescope to scan the skies on August 14, Japanese amateur astronomer Koichi Itagaki discovered a "new" star within the boundaries of the constellation Delphinus. Indicated in this skyview captured on August 15 from Stagecoach, Colorado, it is now appropriately designated Nova Delphini 2013. Sagitta, the Arrow, points the way to the newcomer's location high in the evening sky, not far from bright star Altair and the asterism known to northern hemisphere skygazers as the Summer Triangle. The nova is reported to be easy to spot with binoculars, near the limit of naked-eye visibility under dark skies. In fact, previous deep sky charts do show a much fainter known star (about 17th magnitude) at the position of Nova Delphini, indicating this star's apparent brightness suddenly increased over 25,000 times. How does a star undergo such a cataclysmic change? The spectrum of Nova Delphiniindicates it is a classical nova, an interacting binary star system in which one star is a dense, hot white dwarf. Material from a cool, giant companion star falls onto the surface of the white dwarf, building up until it triggers a thermonuclear event. The drastic increase in brightness and an expanding shell of debris is the result - but the stars are not destroyed! Classical novae are believed to recur when the flow of material onto the white dwarf resumes and produces another outburst.
Explanation: Using a small telescope to scan the skies on August 14, Japanese amateur astronomer Koichi Itagaki discovered a "new" star within the boundaries of the constellation Delphinus. Indicated in this skyview captured on August 15 from Stagecoach, Colorado, it is now appropriately designated Nova Delphini 2013. Sagitta, the Arrow, points the way to the newcomer's location high in the evening sky, not far from bright star Altair and the asterism known to northern hemisphere skygazers as the Summer Triangle.
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 12:32 pm
by Beyond
So... a nova event of this type, lasts as long as it takes for the transferred stellar stuff to escape. , what a BLAST
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 1:57 pm
by bko
On the night of Sunday, August 11th, 2013, my husband and I were on our boat looking for Perseids. I saw a very bright pinpoint flash near Altair and exclaimed "I just saw a nova!" It was approximately 10pm CDT. The lake is in a suburb outside of Minneapolis, MN.
Is it possible it could have been Nova Delphini 2013?
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 1:59 pm
by PADiers
I would be interested to know just how far away this new star/supernova is
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 2:04 pm
by casusbellum
bko wrote:On the night of Sunday, August 11th, 2013, my husband and I were on our boat looking for Perseids. I saw a very bright pinpoint flash near Altair and exclaimed "I just saw a nova!" It was approximately 10pm CDT. The lake is in a suburb outside of Minneapolis, MN.
Is it possible it could have been Nova Delphini 2013?
more likely, if you did not see a trail, it was a Perseid that just happened to be aimed nearly directly AT you. Novae are not split second occurences!
shan
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 2:05 pm
by Chris Peterson
bko wrote:On the night of Sunday, August 11th, 2013, my husband and I were on our boat looking for Perseids. I saw a very bright pinpoint flash near Altair and exclaimed "I just saw a nova!" It was approximately 10pm CDT. The lake is in a suburb outside of Minneapolis, MN.
Is it possible it could have been Nova Delphini 2013?
You probably saw a meteor or an Iridium flare. The rate that a nova brightens is over minutes or hours, and it stays bright for days. Also, this nova, while bright, is still an object that requires a small telescope to see... it isn't naked eye.
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 2:06 pm
by bko
That's what we concluded- but what a coincidence!
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 3:22 pm
by Joe Stieber
Chris Peterson wrote: ... is still an object that requires a small telescope to see... it isn't naked eye.
Actually, it has reached naked-eye brightness (at least from a moderately dark site). I saw it in binoculars on the night of August 14/15 when it was around magnitude 6 (near the threshold of naked-eye visibility). I was at a dark site, but couldn't pinpoint it naked eye, although I could see magnitude 5.8 Uranus naked eye at the time.
Last night (August 15/16), I saw Nova Delphinus 2013 again in binoculars, but from my suburban home, and estimated it to be about magnitude 4.7-4.8, which is indeed bright enough to see naked eye (although not from my light-polluted suburban skies). The latest AAVSO (American Association of Variable Star Observers) estimates put the nova around magnitude 4.4, so it's still brightening. If it's clear tonight, I might have to take a ride out to darker skies for a look.
Joe Stieber
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 3:33 pm
by Chris Peterson
Joe Stieber wrote:Actually, it has reached naked-eye brightness (at least from a moderately dark site).
Of course, it still isn't going to jump out and grab your attention!
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 3:38 pm
by Borc
I'm wondering what physical perameters differentiate between the causes of a nova and a 1a supernova. Why did it nova early instead of waiting to pop a standard candle?
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 3:46 pm
by Chris Peterson
Borc wrote:I'm wondering what physical perameters differentiate between the causes of a nova and a 1a supernova. Why did it nova early instead of waiting to pop a standard candle?
Novas and supernovas are completely different animals. A supernova is the result of a massive star collapsing when its internal fusion can no longer support it against self-gravity. A nova is a much less energetic event that involves a pair of stars, involves only a small fraction of the total mass of the system, and is essentially a surface event. A supernova happens once, and results in the loss of most of the star's mass, either to energy or dissipation. Novas are cyclic, and don't involve the destruction of the star.
(There are less common types of both novas and supernovas, but they're still different from each other.)
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 4:15 pm
by neufer
Borc wrote:
I'm wondering what physical parameters differentiate between the causes of a nova and a 1a supernova.
Why did it nova early instead of waiting to pop a standard candle?
A nova is caused by the accretion of hydrogen on to the surface of a white dwarf,
which ignites and starts hydrogen nuclear fusion in a runaway manner.
An Ia supernova is caused by the accretion of enough mass on to the surface of a white dwarf (of the common carbon-oxygen variety) to approach the 1.38 solar masses limit so as to ignite carbon fusion in a runaway manner blowing up the white dwarf.
<<A nova is a cataclysmic nuclear explosion in a white dwarf star. It is caused by the accretion of hydrogen on to the surface of the star, which ignites and starts nuclear fusion in a runaway manner. A nova is a sudden brightening of a star. Novae are thought to occur on the surface of a white dwarf star in a binary system. If these two stars are close enough, material from one star can be pulled off the companion star's surface and onto the white dwarf.
<<Type Ia supernovae occur in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf while the other can vary from a giant star to even a smaller white dwarf.
A white dwarf is the remnant of a star that has completed its normal life cycle and has ceased nuclear fusion. However, white dwarfs of the common carbon-oxygen variety are capable of further fusion reactions that release a great deal of energy if their temperatures rise high enough.
Physically, carbon-oxygen white dwarfs with a low rate of rotation are limited to below 1.38 solar masses. Beyond this, they re-ignite and in some cases trigger a supernova explosion. Somewhat confusingly, this limit is often referred to as the Chandrasekhar mass, despite being subtly different from the absolute Chandrasekhar limit where electron degeneracy pressure is unable to prevent catastrophic collapse. If a white dwarf gradually accretes mass from a binary companion, the general hypothesis is that its core will reach the ignition temperature for carbon fusion as it approaches the limit. If the white dwarf merges with another star (a very rare event), it will momentarily exceed the limit and begin to collapse, again raising its temperature past the nuclear fusion ignition point. Within a few seconds of initiation of nuclear fusion, a substantial fraction of the matter in the white dwarf undergoes a runaway reaction, releasing enough energy to unbind the star in a supernova explosion.
This category of supernovae produces consistent peak luminosity because of the uniform mass of white dwarfs that explode via the accretion mechanism. The stability of this value allows these explosions to be used as standard candles to measure the distance to their host galaxies because the visual magnitude of the supernovae depends primarily on the distance.>>
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 4:53 pm
by ta152h0
the cosmic blender is making salsa.....
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 5:18 pm
by Ann
It's a nice picture of an interesting part of the Milky Way. I really appreciate the RGB colors.
I note that the nova is relatively blue. Perhaps that is to be expected from a brand-new nova, but not all cosmic explosions are blue. The most extraordinary recent brightening of any Milky Way star, V838 Monocerotis, was extremely red. Admittedly even V838 Mon started out blue.
As for Nova Delphinus 2013, it is certainly located quite far away behind a lot of Milky Way dust, so it is undoubtedly reddened. Therefore it is probably intrinsically bluer than it appears to be here - or it was. Right now the the energy of the explosion must be shifting towards longer wavelengths, reddening the light of it.
Ann
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 6:02 pm
by Boomer12k
Very interesting....would like to see....but the darn skys are overcast....
:---[===] *
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 7:18 pm
by luigi
This is very interesting!
Is it correct to assume that a nova is like type Ia supernova but without enough force to make the star explode?
If that's right then I wonder how close this nova was to actually being a supernova, is there a way to know?
I also wonder how many binary systems are out there where a white dwarf is preparing for the big bang without anyone here knowing. Is there a list of such candidates? Was this star in the list?
So many questions? This APOD was very nice to me it triggered my curiosity.
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Fri Aug 16, 2013 8:22 pm
by avogt
I'm not positive but I may have inadvertently caught a photo of this the night of the 13th in Oregon while experimenting with my new camera. I've always wanted to get into this type of photography and spent that night and the night before taking pictures of the southerly sky from my back yard. The night of the 13th I shot 30 raw images for the purpose of trying a stacking software (I do still have the raw images as well). Unfortunately since I am still learning how to take the photographs they are not as high quality as they could be.
Andy
Edit: Unfortunately the more I look at it I think I was a little to low towards the horizon. Oh well would have been cool if I had caught it...
avogt wrote:I'm not positive but I may have inadvertently caught a photo of this the night of the 13th in Oregon while experimenting with my new camera.
Looking at the large version of the picture you linked, it does not include Nova Delphinus 2013 (even if it had erupted by the 13th). Altair is the bright star near the top edge towards the upper-left corner of your picture, so Sagitta, which points towards the nova, is above the top edge and not visible. Once you locate Altair (and its companion, Tarazed), it's easy to compare it to today's annotated APOD.
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Sat Aug 17, 2013 2:12 am
by Chris Peterson
drollere wrote:if this is a type Ia supernova as the APOD caption asserts...
The caption asserts no such thing. This is a classical nova, not a supernova. I don't think the progenitor star has been conclusively identified, but it's probably fairly close (and inside our own galaxy, of course).
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Sat Aug 17, 2013 4:55 am
by Ann
Chris Peterson wrote: This is a classical nova, not a supernova. I don't think the progenitor star has been conclusively identified, but it's probably fairly close (and inside our own galaxy, of course).
That's interesting, Chris. Do you think it is not sufficiently far away to be significantly reddened by Milky Way dust?
I would have guessed that the nova is at least a thousand light-years away.
Nova Delphini is quite close to constellation Sagitta, and I checked out a number of bright stars in Sagitta. Many of them have parallaxes of 5,6 or 7 milliarcseconds, making them several hundred but not a thousand light-years away. Admittedly these stars aren't significantly reddened. Do you think Nova Delphini is at a similar distance?
Ann
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Sat Aug 17, 2013 5:14 am
by Chris Peterson
Ann wrote:[That's interesting, Chris. Do you think it is not sufficiently far away to be significantly reddened by Milky Way dust?
I would have guessed that the nova is at least a thousand light-years away.
Maybe it's that far away, I don't know. But 1000 ly is close. I was comparing it with supernovas, virtually always seen in other galaxies.
Re: APOD: Nova Delphini 2013 (2013 Aug 16)
Posted: Sat Aug 17, 2013 9:05 am
by Czernoo
I have reviewed all the comments, still can't seem to find an definite hint of how long a typical nova such as this is supposed to stay extra-bright : days? weeks ? more ?
Nova Delphini 2013
, what a BLAST 
