APOD: Cataclysmic Dawn (2015 Jan 11)

[APOD Robot]

Cataclysmic Dawn

Explanation: Will this dawn bring another nova? Such dilemmas might be pondered one day by future humans living on a planet orbiting a cataclysmic variable binary star system. Cataclysmic variables involve gas falling from a large star onto an accretion disk surrounding a massive but compact white dwarf star. Explosive cataclysmic events such as a dwarf nova can occur when a clump of gas in the interior of the accretion disk heats up past a certain temperature. At that point, the clump will fall more quickly onto the white dwarf and land with a bright flash. Such dwarf novas will not destroy either star, and may occur irregularly on time scales from a few days to tens of years. Although a nova is much less energetic than a supernova, if recurrent novas are not violent enough to expel more gas than is falling in, mass will accumulate onto the white dwarf star until it passes its Chandrasekhar limit. At that point, a foreground cave may provide little protection, as the entire white dwarf star will explode in a tremendous supernova.

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[Ann]

Note to future space travelers: Do not settle on a planet orbiting a cataclysmic variable binary star system.

Ann

[aljoclark]

I don't like the lighting in this picture, it is all wrong! The light falling on the moons seems to be coming from nowhere, certainly not from the two stars.

[tedrey]

A picture worthy of Chesley Bonestell.

[Guest]

Those future humans should be more worried about the two moons that are about to collide. Why do space artists constantly put multiple huge moons in their art? The orbits couldn't possibly be stable around a rocky, earth-like planet.

[geckzilla]

Those future humans should be more worried about the two moons that are about to collide. Why do space artists constantly put multiple huge moons in their art? The orbits couldn't possibly be stable around a rocky, earth-like planet.

Why was there a full moon in a scene immediately following a solar eclipse in the movie Apocalypto? Because moons are so cool that it is very easy to forget the astrophysics that make them impossible in many circumstances. Almost every fantasy world is depicted with gorgeous, huge, impossible moon systems. That's really all there is to it. People are very fond of moons.

[Steve Dutch]

You wouldn't see stars with those light sources in the sky. The lighting on the moons is inconsistent with the light sources. A red giant star would still have a sharp edge to a nearby observer, and would saturate the retina so much it would appear white. Also, the spam catcher refers to the Sun as "burning," which it's not.

[Chris Peterson]

Also, the spam catcher refers to the Sun as "burning," which it's not.

There's nothing wrong with using "burn" when referring to stars. One perfectly acceptable meaning is "marked by intense heat". We talk about burning light bulbs. We talk about burning passion. And even scientific papers talk about fusion processes burning H to He. The word is not limited to oxidizing chemical processes.

[firstmagnitude]

I hate this painting -- it's too busy!

[owlice]

Also, the spam catcher refers to the Sun as "burning," which it's not.

There's nothing wrong with using "burn" when referring to stars. One perfectly acceptable meaning is "marked by intense heat". We talk about burning light bulbs. We talk about burning passion. And even scientific papers talk about fusion processes burning H to He. The word is not limited to oxidizing chemical processes.

I don't see "burn" anywhere in the explanation for this APOD.

[geckzilla]

Also, the spam catcher refers to the Sun as "burning," which it's not.

There's nothing wrong with using "burn" when referring to stars. One perfectly acceptable meaning is "marked by intense heat". We talk about burning light bulbs. We talk about burning passion. And even scientific papers talk about fusion processes burning H to He. The word is not limited to oxidizing chemical processes.

I don't see "burn" anywhere in the explanation for this APOD.

The reference is to the anti-bot question I have set up for guests.

[Chris Peterson]

I don't see "burn" anywhere in the explanation for this APOD.

The reference is to the anti-bot question I have set up for guests.

And FWIW, a couple of the links in the caption go to pages that talk about nuclear burning (one even uses "nuclear fires burn"!)

[BDanielMayfield]

Why do space artists constantly put multiple huge moons in their art? The orbits couldn't possibly be stable around a rocky, earth-like planet.

Cuz, ifen dey onlys put one moons in da dad burn pic, us ignoraint saps mighta thunka da planet is Earth.

Another gripe about space art in films is that, no matter how much time is supposed to have passed, the orientation of the ubiquitous multi-moons never change.

Bruce

[rtyags2k]

Does no one think that a lot of artistic liberty was taken to make the whole celestial image look like a human face? In fact, this may actually be (very likely unintentionally) pretty close to the Hindu deity Shiva who has a "third eye" usually shown embedded in his forehead (the accretion disk) and when the eye opens, it destroys the whole creation (the nova!).

[starsurfer]

It doesn't matter if it's not super realistic but I think it is very evocative and imaginative!

Some examples of cataclysmic binaries are known to be associated with bowshock nebulae including BZ Camelopardalis at the heart of the misclassified planetary nebula EGB 4. This is something I'd like to see imaged by Adam Block.

[dmullins@lcogt.net]

There is actually quite a bit wrong with this picture. That's why nobody likes to go to science fiction movies with me. If it's not technically and scientifically accurate, it should be classified as Fantasy...

There would be no water, clouds, or even an atmosphere left on such a planet. Novas and Supernovas would have blown it all away.

The large star would have to be a very cool brown dwarf to be so dim.

Stars would not be visible in the sky with the stars above the horizon.

The two moons, would not be stable, off axis to the plane of the solar system and would probably be long gone.

Even if the moons were stable, their lit crescents would be greater than 180 degrees being lit from two sources.

In order for the smaller star to capture material from the larger one, the gravitational forces of each would have to cancel close enough to the surface of the large star that material being eject from it by the violent processes of the surface of such a star that the material would be captured by the gravity of the smaller one. I don't think this would look so much like a thread as it would like a funnel structure at the periphery of the acretion disk.

And yes, it is very symmetrical and symbolically face like.

Ok. Enjoy the art.

[dmullins@lcogt.net]

Isn't the name of the star at the center of our solar system Sol?

[geckzilla]

There would be no water, clouds, or even an atmosphere left on such a planet. Novas and Supernovas would have blown it all away.

I think you could get away with something like an atmosphere which is constantly replenished by severe volcanic activity and some other liquid in place of water. Something that doesn't evaporate at such low temperatures. Not like this picture, but something anyway.