Star “outburst”

I originally gave this timelapse series the title “star explosion,” but in fact it’s not clear what the deuce is going on here. What is clear is that it’s something spectacular.  The YouTube notes describe what we’re seeing and how the montage was made:

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.

As light from the eruption propagates outward into the dust, it is scattered by the dust and travels to the Earth. The scattered light has travelled an extra distance in comparison to light that reaches Earth directly from the stellar outburst. Such a light echo is the optical analogue of the sound echo produced when an Alpine yodel is reflected from the surrounding mountainsides.

The NASA/ESA Hubble Space Telescope has been observing the V838 Mon light echo since 2002. Each new observation of the light echo reveals a new and unique “thin-section” through the interstellar dust around the star. This video morphs images of the light echo from the Hubble taken at multiple times between 2002 and 2006. The numerous whorls and eddies in the interstellar dust are particularly noticeable. Possibly they have been produced by the effects of magnetic fields in the space between the stars.

Anyway, the “event”, covering four years compressed into 49 seconds, is something to see:

But what is it?  Gizmodo gives several possibilities, which also appear in Wikipedia, but Gizmodo leaves out #6: a “common envelope event.

  • An atypical nova outbursts (this is very unlikely.)
  • A thermal pulse of a dying star (the new pulse illuminates the layers of star material previously ejected its previous outbursts.)
  • A thermonuclear event within a massive supergiant (in which the helium in one of the layers of the massive star ignites and starts a fusion process.)
  • A mergeburst (the burst caused by the merge of two main sequence stars.)
  • A planetary capture event (in which the star has swallowed one of its giant gas planets.)

If the last possibility is true, this star got the worst case of gas in the Universe, belching big time.  Actually, I have no idea what’s going on here, and even speculating is way about my pay grade. Readers with some astronomical/cosmological knowledge may wish to speculate.


  1. GBJames
    Posted April 26, 2020 at 1:18 pm | Permalink


  2. Posted April 26, 2020 at 1:32 pm | Permalink

    The current majority-opinion in the primary literature is that it was a merger event between a massive star (perhaps 8 solar masses) and a lower-mass star (about 0.3 solar masses).

  3. Posted April 26, 2020 at 1:47 pm | Permalink

    Very cool. There seems to be a lot of inhomogeneity in the interstellar dust, but it doesn’t conform to any intuitive shape (like a planar arrangement of planets and asteroids) that I would expect. But then, I’m an astronomy ignoramus.

  4. Ken Kukec
    Posted April 26, 2020 at 1:49 pm | Permalink

    The numerous whorls and eddies in the interstellar dust are particularly noticeable.

    At about the two-thirds mark in the video, the whorls and eddies resemble those in the Donald’s Rococo comb-over.

    • Posted April 26, 2020 at 2:24 pm | Permalink

      Yes! God is trying to tell Trump’s followers something. I’ve recently began to wonder why those that believe Trump was chosen by God to lead the American people, don’t also see the COVID-19 pandemic as God saying they’re wrong and that they made a bad choice. After all, his presidency is the perfect example of a “disaster” (bad star) like this one.

  5. Posted April 26, 2020 at 2:13 pm | Permalink

    Since we don’t know what it is, it must be aliens.

  6. Posted April 26, 2020 at 2:21 pm | Permalink

    It is a clear explanation that the outward propagation we are seeing is because light is being scattered from various layers of interstellar dust, and so the light takes different amounts of time to reach us. Less scattered light gets to use first, more scattered light gets to use later.
    But what I dont’ understand is why it looks like illuminated dust moving away from the central star. You see structures next to structures next to structures, and these seem to be moving outward, together, thru the series of images. But if the dust is moving, as it seems to, the speeds would be incredible.

    • Posted April 26, 2020 at 2:21 pm | Permalink

      us, not use.

    • Steve Gerrard
      Posted April 26, 2020 at 3:10 pm | Permalink

      Look at the related post listed above, titled ‘A “light echo” from a star actually shows light moving.” It’s for a WEIT post in Nov 2013 on the same event. It explains that the dust isn’t moving, it is the progress of light reaching dust further and further out from the star that you see transpiring in the video.

  7. rickflick
    Posted April 26, 2020 at 2:27 pm | Permalink

    A spectacular time-lapse. Kudos to NASA and Hubble.

  8. ThyroidPlanet
    Posted April 26, 2020 at 2:30 pm | Permalink

    The idea of a light echo is fascinating

  9. Hempenstein
    Posted April 26, 2020 at 5:36 pm | Permalink

    Hard to fathom that this happened 20kyrs ago, too.

    • David Harper
      Posted April 27, 2020 at 4:24 am | Permalink

      And V838 Mon is relatively close in astronomical terms. Go out and look for the Great Andromeda Galaxy (aka Messier 31) in the late summer or early autumn. If you have dark skies, you’ll be able to see it with the naked eye as a fuzzy smudge on the sky. It’s two million light years away, making it the most distant object that you can see without a telescope or binoculars. The light that’s hitting your retina left the stars of that galaxy two million years ago. To put that in perspective, that’s not very long after our distant ancestors began using stone tools.

      • Hempenstein
        Posted April 27, 2020 at 6:49 am | Permalink

        Yep, further unfathomable, by two orders of magnitude!

  10. Torbjörn Larsson
    Posted April 26, 2020 at 6:31 pm | Permalink

    Main sequence stars and light echos (or black holes and jets) are enough astronomical physics to stumble around in. I don’t envy those who try to study these eruptions!

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