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Light Echoes from V838 Mon

Explanation: What caused this outburst of V838 Mon? For reasons unknown, star V838 Mon's outer surface suddenly greatly expanded with the result that it became the brightest star in the entire Milky Way Galaxy in January 2002. Then, just as suddenly, it faded. A stellar flash like this had never been seen before -- supernovas and novas expel matter out into space. Although the V838 Mon flash appears to expel material into space, what is seen in the above image from the Hubble Space Telescope is actually an outwardly moving light echo of the bright flash. In a light echo, light from the flash is reflected by successively more distant rings in the complex array of ambient interstellar dust that already surrounded the star. V838 Mon lies about 20,000 light years away toward the constellation of the unicorn (Monoceros), while the light echo above spans about six light years in diameter.

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Ah yes, very interesting. V838 Mon is a reminder of how bright stars can get and how red they can get in the process.

In order for a star to get so bright and so red, its outer envelope has to expand tremendously, yet remain luminous the whole time. Personally I can't help wondering if the fusion processes going on inside it must work faster during this enormous outer expansion. Or were we watching the effects of some kind of gravitational core contraction?

There has been a lot of speculation as to the cause of V838 Mon's exceptional behavior. One hypothesis has been that the star suddenly "ate" one of its planets.

I think it has been proven that V838 Mon started out as a bright blue star before it had its tremendous outburst. Personally I doubt that a less massive star, for example the Sun, could imitate V838 Mon's behavior under any circumstances.

For all of that, I hope the Sun will refrain from flaring up like mad because it suddenly snacked on Mercury, for example!

Ann

The successive pictures of this light echo over the past 6 years could be used to create a true 3D map of dust in the surrounding region. Would be awesome. Has anyone tried?

I haven't found the date of the image. Since the light echo is 6 light-years across, I expect it to be 3 years after the initial burst. Is that true?

I found the image here:
http://en.wikipedia.org/wiki/File:V838_ ... ansion.jpg

which says it's from Feb. 8, 2004. This is about 25 months after the outburst, so how can the radius be 3 l.y.? Is this some superluminal illusion?

I love this image. Not the least because it is very eerily the same as the Firefox Icon on my Mac. http://imgur.com/gallery/uQe7h

Is "echo" correct terminology here? An echo is what you get when sound is reflected back to the hearer or reverberates like in a hall. What is described here is a light pulse traveling outward from its source and successively illuminating parts of a surrounding shell of material. Observers here saw it as a brief flash of light from the star. Since the pulse has left its source, the surrounding shell should be as we see it. If the shell is changing in appearance, is it because output from the star is fluctuating? Or, is light in fact bouncing back and forth in the shell? Don't understand.

zbvhs wrote:Is "echo" correct terminology here?

Have a look at the V838 Monocerotis Wikipedia page. It has a clear explanation of the light echo effect, as well as a concise comparison of the various theories as to what happened.

Rob

Hugo wrote:
The successive pictures of this light echo over the past 6 years could be used to create a true 3D map of dust in the surrounding region. Would be awesome. Has anyone tried?

I don't know, Hugo.

Even if there is a continuous succession of pictures somewhere it's not as easy a project as one might first imagine:

• 1) There is no guarantee that the primary illuminating source is a single spherically symmetric pulse.
  
  • a) There is continuous bright illumination from the bright stars we see here.
    b) There might have been a number of pulses.
    c) If the pulse source resembled Eta Carinae it seems unlikely that the illumination was spherically symmetric.
  2) The cloud itself might be optically thick in places thereby producing both shadowing & re-echoing complications.

neufer wrote:

Hugo wrote:
The successive pictures of this light echo over the past 6 years could be used to create a true 3D map of dust in the surrounding region. Would be awesome. Has anyone tried?

I don't know, Hugo.

Even if there is a continuous succession of pictures somewhere it's not as easy a project as one might first imagine:

• 1) There is no guarantee that the primary illuminating source is a single spherically symmetric pulse.
  
  • a) There is continuous bright illumination from the bright stars we see here.
    b) There might have been a number of pulses.
    c) If the pulse source resembled Eta Carinae it seems unlikely that the illumination was spherically symmetric.
  2) The cloud itself might be optically thick in places thereby producing both shadowing & re-echoing complications.

True, but a wildly inaccurate 3D map would get just as many ooohs and aaahs!

Edit P.S. Besides, we don't need no steenking complications!

Always an awe inspiring sight.

:---[===] *

Hello Dave - how are you?

Spock: "Captain, the light curve produced by the eruption is unlike anything previously seen."


:---[===] *

Hugo wrote:The successive pictures of this light echo over the past 6 years could be used to create a true 3D map of dust in the surrounding region. Would be awesome. Has anyone tried?

I don't know about any 3d maps but there are some nice timelapse videos of it on youtube. Very nice picture by the way. One of my favorites.

Timelapse:
http://www.youtube.com/watch?v=EhwGkFM5_jo

I don't get it...
If it´s a light echo, shouldn't the forms change continually, showing the dust structure (like a magnetic resonanse imaging) ?
Also, shouldn't the speed be the same from beginning to end?

looks like I am looking down the barrel of a shotgun, perhaps similar to looking down the axis of Eta Carinae

Guest wrote:Timelapse:
http://www.youtube.com/watch?v=EhwGkFM5_jo

I don't get it...
If it´s a light echo, shouldn't the forms change continually, showing the dust structure (like a magnetic resonanse imaging) ?
Also, shouldn't the speed be the same from beginning to end?

It looks like they used the Hubble images and used morphing technology on them - morphing *stretches* the smaller light echo to match the larger one, so it looks like a smooth video.

neufer wrote:

Hugo wrote:
The successive pictures of this light echo over the past 6 years could be used to create a true 3D map of dust in the surrounding region. Would be awesome. Has anyone tried?

I don't know, Hugo.

Even if there is a continuous succession of pictures somewhere it's not as easy a project as one might first imagine:

• 1) There is no guarantee that the primary illuminating source is a single spherically symmetric pulse.
  
  • a) There is continuous bright illumination from the bright stars we see here.
    b) There might have been a number of pulses.
    c) If the pulse source resembled Eta Carinae it seems unlikely that the illumination was spherically symmetric.
  2) The cloud itself might be optically thick in places thereby producing both shadowing & re-echoing complications.

The other bright stars in view did not illuminate the dust before V838 Monocerotis brightened.
There is every indication that the illumination was spherically symmetric.

There were two pulses mostly in infrared wavelengths after the first one. The main pulse started out blue, and got redder, making it easier to create a 3D map, if someone wanted to. It would still be difficult though - and impossible in some areas.

FLPhotoCatcher wrote:

Guest wrote:Timelapse:
http://www.youtube.com/watch?v=EhwGkFM5_jo

I don't get it...
If it´s a light echo, shouldn't the forms change continually, showing the dust structure (like a magnetic resonanse imaging) ?
Also, shouldn't the speed be the same from beginning to end?

It looks like they used the Hubble images and used morphing technology on them - morphing *stretches* the smaller light echo to match the larger one, so it looks like a smooth video.

Oooh. That makes sense. Thanks.

Very interesting APOD. Can't say that I have ever seen anything quite like it. Looks like a gravitationally lensed wookie

FLPhotoCatcher wrote:
The other bright stars in view did not illuminate the dust before V838 Monocerotis brightened.
There is every indication that the illumination was spherically symmetric.

There were two pulses mostly in infrared wavelengths after the first one. The main pulse started out blue, and got redder, making it easier to create a 3D map, if someone wanted to. It would still be difficult though - and impossible in some areas.

Be that as it may.

There seems to be much more astrophysical interest in exactly what caused the light pulse in the first place:

http://en.wikipedia.org/wiki/V838_Monocerotis wrote:
Models:

• 1 Atypical nova outburst
  2 Thermal pulse of a dying star
  3 Thermonuclear event within a massive supergiant
  4 Mergeburst
  5 Planetary capture event

low octane helium, perhaps ?

Exactly Light EchoOne with only half the calorieshalf the calorieshalf the calories