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VanderL
2003-Sep-22, 03:16 PM
Hi there,
Who remembers the "eye-popping" Hubble images of V838 Monocerotis, March this year?
In the news release the phenomenon is explained as light hitting earlier expelled concentric shells of matter, see http://www.space.com/scienceastronomy/aas2...est_030526.html (http://www.space.com/scienceastronomy/aas202_strangest_030526.html)
What I don't understand is what concentric shells they are talking about. To my eyes there is only one shell of material that is seen expanding, you can even trace back all the structure from the last image to the first. So what is all this talk of light reflection about when clearly there is one shell rapidly expanding??

Cymbyz
2003-Sep-24, 06:24 AM
I recall reading a UT report several days ago that the star, on further analysis, was found to have apparently consumed three close-orbiting gas-giant planets.

VanderL
2003-Sep-24, 09:27 PM
Thanks,

I read about the planets being swallowed, unfortunately the planets have disappeared and we can never be sure that this is really what happened. It could be true, but then again, how are we going to prove it?
All this is still not answering my question, that what I see in the pictures is ONE shell expanding, while the experts are talking about light echoes from previously expelled material. How can they claim this, based on the pictures shown in the above link?
Beats me.

VanderL
2003-Dec-05, 07:53 AM
Hi there,
I finally found the reason why V838 Mon is thought to be lighting up previously expelled layers. APOD today (December 5th), tells us these layers MUST exist because otherwise the shell would have been expanding faster than light!!
So these people claim something that cannot be proven, and, more importantly, cannot be concluded from the existing data. I think this is really bad science. What if the object in the picture is much closer than we think? This could be a good way to estimate the real distance to this object.
The next question is what happened to the star, I think it just gave birth to a planet. And closely watch the news on this "strange" variable star, it could well be the next news-item that a planet closely orbits this star, the news would of course concentrate on the "mystery"' of how a planet so close to the star could have survived the blast.
Cheers.

Haglund
2003-Dec-05, 11:02 AM
And since the shell is several lightyears, how could there be only months between the pictures?

Edit: Hm, should've done a little more "research" before asking that, since the answer is to be found here: http://www.space.com/scienceastronomy/ligh...326.html#update (http://www.space.com/scienceastronomy/light_echo_030326.html#update) and here: http://www.space.com/php/multimedia/imaged...030326_02,0.jpg (http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=light_echo_graphic_030326_02,0 .jpg)

VanderL
2003-Dec-05, 01:48 PM
Thanks Parker,

Good question and the answers are available, but I don't see the evidence of light-echoes. What I see is an expanding shell (only one) and apparently what I should see is existing shells lighting up. So my question remains unanswered; what do we HAVe to see a light-echoe when there is no need?

VanderL
2003-Dec-07, 12:31 PM
Did some more digging (there's too little time for me to do it extensively so anyone with more info please help) and I found that V838 Mon is not acting like nova theory predicts. Apparently there is no explosion of outer layers, only a "ballooning" of outer layers. Also V838 Mon is a binary system, and I would be curious to know if this fact was known before the "eruption".
The people studying this star system say it doesn't fit nova theory and try to make it into a very rare and special phenomenon. Suppose this is a normal nova (I don't know of any other example where a nova happened while we were looking), then nova theory is incorrect and we need a model that can explain this outburst. Don Scott has explained what happened to V838 Mon using the Electric Model and it can be found at http://www.electric-cosmos.org/hrdiagr.htm , it is in the section commenting on variable stars that falsify current theory.
Anyone have any comments?
And of course I still don't get the "light-echo" explanation. I can only see an expanding shell, not a number of existing shells that are successively lighted.
Thanks.

Littlemews
2003-Dec-08, 05:00 AM
Some of the website saids this binary star system is pretty similiar to the one of "M31-RedVar" and "V4332 Sgr"..... a sub Giant, later it will become a super giant..later (thats what I think ><)

"The light echo is caused by energy from the eruption interacting with dust surrounding the star. The interaction scatters the light, making it very bright in the cooler wavelengths. It is believed that the dust surrounding the star exists as slowly expanding shells shed during the star&#39;s (or a companion&#39;s) earlier life. As the energy from the outburst reaches each shell, its brightness changes based on the density and geometry of the shell and the outburst energy. Measuring the growth rate of the echo gives us an estimated distance from Earth of around 7500 light years. "

From : http://www.aavso.org/vstar/vsots/1202.shtml

VanderL
2003-Dec-08, 08:03 AM
Thanks Littlemews,

The light-echo scenario is explained in detail as you quoted, but if you remember the time-lapse "movie" it is immediately clear that there are no previous shells being lighted (look at the sequence and try to see different shells). What is visible is one shell expanding, there is structure in the shell (strings and holes) that grow in size, exactly what you expect when one shell is expanding. Also the event was very fast, the star brightened 10.000 times in only one day&#33; This is not expected in current theory, so the event is thought to be very rare. But since we see it, it can&#39;t be that rare, maybe this is exactly what every nova looks like in reality, not in theory.
Cheers.

Littlemews
2003-Dec-08, 07:58 PM
That look like a White Dwarf Super Nova, because of the Hydrogen gas is very hot, and it begins to blast(I think)

"Mass of the shell less than 10,000 of the Mass of the sun, but very bright"

So it is White Dwarf Super Nova, because u said its luminosity is very bright only in a few day. I mean it gets very bright...

Blob
2006-Oct-27, 02:38 PM
Hubble has returned to the intriguing V838 Monocerotis many times since its initial outburst in 2002 to follow the evolution of its light echo. Two new images provide the most astonishing views of V838 to date.

The unusual variable star V838 Monocerotis (V838 Mon) continues to puzzle astronomers. This previously inconspicuous star underwent an outburst early in 2002, during which it temporarily increased in brightness to become 600,000 times more luminous than our Sun. Light from this sudden eruption is illuminating the interstellar dust surrounding the star, producing the most spectacular "light echo" in the history of astronomy.

<attachment>
Expand (http://imgsrc.hubblesite.org/hu/db/2006/50/images/c/formats/large_web.jpg) (259kb, 716 x 800)
Credit NASA
Position (2000): R.A. 07h 04m 04.8s Dec. -03 50' 50"

Read more (http://www.spacetelescope.org/news/html/heic0617.html)

Peter Wilson
2006-Oct-27, 06:39 PM
Thanks Littlemews,

The light-echo scenario is explained in detail as you quoted, but if you remember the time-lapse "movie" it is immediately clear that there are no previous shells being lighted (look at the sequence and try to see different shells). What is visible is one shell expanding, there is structure in the shell (strings and holes) that grow in size, exactly what you expect when one shell is expanding...
Things aren't always as they appear.

Simplest explanation is that we are seeing forward-scattered light from initial flash reflected at ever-greater angles off pre-existing dust, i.e a light-echo.

George
2006-Oct-28, 04:46 AM
There is an impressive video (http://www.spacetelescope.org/videos/html/mov/320px/heic0405a.html) of V838Mon.

antoniseb
2006-Oct-28, 11:41 AM
There is an impressive video (http://www.spacetelescope.org/videos/html/mov/320px/heic0405a.html) of V838Mon.
That is a nice video. I'm curious to know how many actual images were used to make it, and how much was from CGI to fill the gaps.

eburacum45
2006-Oct-28, 01:36 PM
The mere fact that the 'shell' appears to expand faster than light is good confirmation that we are seeing light echoes, not any physical thing expanding faster than light.

George
2006-Oct-28, 03:00 PM
That is a nice video. I'm curious to know how many actual images were used to make it, and how much was from CGI to fill the gaps.
I'd bet a small ice cream cone it is just these images (http://www.spacetelescope.org/images/screen/heic0405b.jpg).


The mere fact that the 'shell' appears to expand faster than light is good confirmation that we are seeing light echoes, not any physical thing expanding faster than light.
Yes, and it reveals its distance with simple trig. :) I think I read it was 20,000 lyrs. This method was used with 1987a demonstrating its distance.

It is my understanding there are three echos that have been found.

George
2006-Oct-28, 08:13 PM
The idea that the light echos may have been caused by large planets having migrated into the star is very intresting.

If migrations of large planets into their host star are common during the early years of stellar formation, could light echos be more common than we think?

If these events primarily occur in the early years while most stars are still in the cocoon of the larger nebula, would these flashes go unnoticed?

As an amateur, this is an area of research I would like to get into if there is such a chance. [Besides, heliochromology is somewhat limited. ;)]

ozmarble
2006-Nov-27, 11:14 AM
VanderL,

I found this forum while searching for updated images of V838 Monocerotis. From the first time i saw the first 4 images a few years ago, I too shared the belief that there is only a single shell expanding. Might break current understandings of light speed perhaps, but OTOH I say that
a) I can't see any light echos coming from the center rear of the star...yet
b) The 'expanding shell' seems more likely given the holes 'grow', implying a single shell, rather than the more unlikely scenario of multiple shells that happen to have the holes in the same places (ie the star wasn't rotating, morphing etc while giving off these earlier shells over a significant period of time)

Eventually, when light from the back side of the nebula begins to arrive, the light echo will give the illusion of contracting, and finally it will disappear. (http://heritage.stsci.edu/2005/02/supplemental.html)

Somehow, I don't see the above prediction coming true... In fact I think there's enough evidence from those expanding holes already to drive truck through the light echo explanation....actually maybe more than 1 truck.......uhh - how big is that star again? :P

Call me a fool perhaps - but I'm looking forward to the impact this star is going to have on physics over the next couple of years...