Light echoes from V838 Mon

Mar 19, 2013
Credit: NASA, ESA

(Phys.org) —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 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 above spans about six light years in diameter.

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HannesAlfven
1.8 / 5 (5) Mar 19, 2013
Okay, then where are the shadows?

It might just as well be an interstellar plasma which exhibits sufficient charge flow to switch from the dark to the glow modes.
Fleetfoot
5 / 5 (6) Mar 19, 2013
Okay, then where are the shadows?


How do you know some of the darker patches on the sphere aren't shadows?

It might just as well be an interstellar plasma which exhibits sufficient charge flow to switch from the dark to the glow modes.


That would produce emission at characteristic spectral lines, not the broadband emissions seen, and if your plasma was moving outward, it would show Doppler shift.

You're giving Alfven a bad name.