APOD: The Rise and Fall of Supernova 2015F (2016 Feb 09)

[APOD Robot]

The Rise and Fall of Supernova 2015F

Explanation: Sit back and watch a star explode. The actual supernova occurred back when dinosaurs roamed the Earth, but images of the spectacular event began arriving last year. Supernova 2015F was discovered in nearby spiral galaxy NGC 2442 by Berto Monard in 2015 March and was unusually bright -- enough to be seen with only a small telescope. The pattern of brightness variation indicated a Type Ia supernova -- a type of stellar explosion that results when an Earth-size white dwarf gains so much mass that its core crosses the threshold of nuclear fusion, possibly caused by a lower mass white-dwarf companion spiraling into it. Finding and tracking Type Ia supernovae are particularly important because their intrinsic brightness can be calibrated, making their apparent brightness a good measure of their distance -- and hence useful toward calibrating the distance scale of the entire universe. The featured video tracked the stellar disruption from before explosion images arrived, as it brightened, and for several months as the fission-powered supernova glow faded. The remnants of SN2015F are now too dim to see without a large telescope. Just yesterday, however, the night sky lit up once again, this time with an even brighter supernova in an even closer galaxy: Centaurus A.

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[Ann]

That's a very interesting APOD!

APOD Robot wrote:
Sit back and watch a star explode.

Click to view full size image

Fritz Zwicky.

When I read that, I couldn't help thinking of the brilliant but eccentric Swiss-American astronomer Fritz Zwicky. (Sorry, I couldn't find out who is the author of the iconic image at left.)

I once saw a cartoon of Fritz Zwicky, where the scientist is madly gazing through his telescope all night, looking for supernovas. His exhausted assistant lies down for a nap, telling Zwicky, "Prof, wake me up when something explodes up there!"

Now APOD is making it almost possible for us to do just that!

Ann

[alex_ag]

Yes, very interesting APOD indeed. In the video, it seems that many stars in the foreground seem alos to appear or vanish...

[nstahl]

Talk about a bad day in the neighborhood!

[mister T]

as the fission-powered supernova glow faded.

Am I correct in assuming this means the the "afterglow" is powered by the breakdown of the heavier (unstable?) isotopes created in the initial blast?

"First I'm gonna smack you with my fusion then I'm gonna pummel you with fission..."

[hamilton1]

The link for an 'even brighter supernova' doesn't seem to be working.

[smitty]

Sorry, but I find this write-up confusing. Stars routinely are powered by nuclear fusion reactions, so what is meant by saying that the star gained so much mass that its core crossed the threshold of nuclear fusion?

[nstahl]

Typically it would gain mass from a companion star.
https://en.wikipedia.org/wiki/Supernova#Normal_Type_Ia

[smitty]

Thank you. (Had the original write-up stated that the star gained sufficient mass that its core crossed the threshold of CARBON fusion this clarification would not be needed.)

[neufer]

as the fission-powered supernova glow faded.

Am I correct in assuming this means the the "afterglow" is powered by the breakdown of the heavier (unstable?) isotopes created in the initial blast?

"First I'm gonna smack you with my fusion then I'm gonna pummel you with fission..."

• Yes.

[b][color=#0000FF]Comparative supernova type light curves[/color][/b]

---

Click to play embedded YouTube video.

<<The visual light curves of the different supernova types all depend at late times on radioactive heating, but they vary in shape and amplitude on the underlying mechanisms of the explosion, the way that visible radiation is produced, the epoch of its observation, and the transparency of the ejected material. The light curves can be significantly different at other wavelengths. For example, at ultraviolet wavelengths there is an early extremely luminous peak lasting only a few hours corresponding to the breakout of the shock launched by the initial explosion, but that breakout is hardly detectable optically.

The light curves for type Ia are mostly very uniform, with a consistent maximum absolute magnitude and a relatively steep decline in luminosity. Their optical energy output is driven by radioactive decay of nickel-56 (half life 6 days), which then decays to radioactive cobalt-56 (half life 77 days). These radioisotopes from material ejected in the explosion excite surrounding material to incandescence. Studies of cosmology today rely on ⁵⁶Ni radioactivity providing the energy for the optical brightness of supernovae of Type Ia, which are the "standard candles" of cosmology but whose diagnostic 847keV and 1238keV gamma rays were first detected only in 2014, 47 years after the prediction of their emission by supernovae. The initial phases of the light curve decline steeply as the effective size of the photosphere decreases and trapped electromagnetic radiation is depleted. The light curve continues to decline in the B band while it may show a small shoulder in the visual at about 40 days, but this is only a hint of a secondary maximum that occurs in the infra-red as certain ionised heavy elements recombine to produce infra-red radiation and the ejecta become transparent to it. The visual light curve continues to decline at a rate slightly greater than the decay rate of the radioactive cobalt (which has the longer half life and controls the later curve), because the ejected material becomes more diffuse and less able to convert the high energy radiation into visual radiation. After several months, the light curve changes its decline rate again as positron emission becomes dominant from the remaining cobalt-56, although this portion of the light curve has been little-studied.

Type Ib and Ic light curves are basically similar to type Ia although with a lower average peak luminosity. The visual light output is again due to radioactive decay being converted into visual radiation, but there is a much lower mass of nickel-56 produced in these types of explosion.>>

[Guest]

To me, ,the most amazing thing here are the astronomers.How do they know where to look? How long does it take to catch a "moment" like this? Is the greatest virtue of an astronomer Patience? or maybe good tracking programs in this age? My congratulations to Mr. Monard for his fine work and also to those many other searchers who haven't found a "pot of gold" (yes, it may have been created here) yet.

[Ron-Astro Pharmacist]

Supernovae at least go out with a bang. At the point of "black dwarf" is the only loss of heat through radiation into empty space? At the end of its energy, after that last photon is radiated, at the end of light does it still have mass or just dark matter? Brrrr!

That would be some cold dark matter.

[Tszabeau]

That is the most awesome video I've ever viewed. The galaxy appears as a living thing. I'm not sure if it's that we are, actually, seeing it's stars moving or if it's just an illusion of graininess and wishful thinking but, it sure works for me.

[Chris Peterson]

That is the most awesome video I've ever viewed. The galaxy appears as a living thing. I'm not sure if it's that we are, actually, seeing it's stars moving or if it's just an illusion of graininess and wishful thinking but, it sure works for me.

Except for the supernova, all the change, the flickering, the variation in this video is caused by atmospheric seeing, cosmic ray strikes, and statistical noise.

[JohnD]

I've asked before if the Universe isn't, in the long run, too dangerous for life except in a few lucky places, to learn from Chris that massively energetic X-rays would be blocked by an atmosphere. But what would be the radius of destruction of a Supernova?

John

[Chris Peterson]

I've asked before if the Universe isn't, in the long run, too dangerous for life except in a few lucky places, to learn from Chris that massively energetic X-rays would be blocked by an atmosphere. But what would be the radius of destruction of a Supernova?

That's a complicated question. In terms of mechanical energy, just a few light years at most. In terms of radiation, somewhere from a few tens of light years in most cases to a much rarer 1000 or so light years- assuming a planet like Earth where small atmospheric changes have a large impact on life. Much less, probably, for planets where the life is largely in water.

Fortunately, given the short lifetimes of most stars that supernova, many are found in the vicinity of the region in which they formed, so most of their neighbors are young as well, and therefore unlikely to harbor life (especially complex life).

There are many ways that a nearby supernova can impact a star system- but "destruction" is not generally one of them.

[JohnD]

Thank you, Chris! I suppose it all depends on what you mean by "impact" then!
Fingers crossed.
John

(Are there any Type 1A supernova candidates in range of us?)

[Chris Peterson]

(Are there any Type 1A supernova candidates in range of us?)

Yes.

The impact of the nearest is likely to be some small chemistry changes in the atmosphere, like a reduction in the ozone layer. In rarer cases, enough radiation might penetrate that mutation rates would increase, driving an evolutionary pulse (something suspected to have occurred in the past). Technology should allow us to mitigate many potentially harmful effects.

[daddyo]

...Technology should allow us to mitigate many potentially harmful effects.

Maybe not the initial onslaught of radiation, we need a supernova duck & cover red alert system...

[Chris Peterson]

...Technology should allow us to mitigate many potentially harmful effects.

Maybe not the initial onslaught of radiation, we need a supernova duck & cover red alert system...

Unless it's very close, radiation itself isn't likely to be much of a problem. The bigger issue is the loss of the ozone layer, and that doesn't spell instant disaster.

[JohnD]

daddyo,
"Duck and cover"?
This was the UK equivalent, "Protect and survive" : https://www.youtube.com/watch?v=6677Eppc-sk

Remember, that was the Official UK Government's response to all-out nuclear exchange.
"Duck and cover" was the US equivalent: https://www.youtube.com/watch?v=BFT8hLjHtuE

Just so's you know.
John

[Boomer12k]

Very nice video...amazing to catch something like that.

:---[===] *

[ta152h0]

this is a great catch. Was there a clue this was going to happen ?

[Ann]

this is a great catch. Was there a clue this was going to happen ?

There were no clues.

A supernova explosion explosion is like a landmine. First there is nothing, then there is a bang. Yes, if astronomers could have carefully studied the particular progenitor of SN 2015F, they just might have caught some little signs that something was about to happen.

But the particular star system that gave rise to SN 2015F would have been far, far too faint even for Hubble to study in a meaningful way. The host galaxy is about 80 million light years away, and the progenitors of SN type Ia are typically relatively faint.

And what do we mean by saying that something is "about" to happen? That might just mean that a supernova could be happening very "soon" - like, say, in a thousand years. We can hardly expect the Hubble telescope to keep a unblinking eye on every moderately nearby galaxy for the next thousand years in order to catch any possible supernova as it happens before our descendants' eyes.

Ann

[bls0326]

Did any neutrino detectors report a rise in neutrino count associated with this supernova?