Astronomy Cosmology popular science and science education UD's Sci-Tech watch

Betelgeuse dims, astrophysicists speculate

Spread the love
Orion on the Celestial Equator, with Betelgeuse highlighted
Orion is the brightest constellation in the sky [HT: Wikipedia]

Since about October 2019, Betelgeuse (the bright reddish star at Orion’s shoulder in the brightest constellation in the sky that is about 600 – 700 ly distant from us) has begun a sharp dimming that has now gone beyond what has been seen in modern observations. As of the end of January, it was down about 2.5 1.4 in apparent magnitude (corrected from the added graph).

Here is its “portrait” — it is one of the few stars we have seen as a disk:

Betelgeuse, captured by ALMA. Notice, it is lop sided and seems to be roiled by large convection cells. In size, it is almost as large across as the orbit of Jupiter (HT: Wiki)

ADDED: a plot of apparent magnitude:

Betelgeuse light curve since 2010, HT Edward Guinan, Villanova University, .infinitoteatrodelcosmo.it and WUWT; also UD reader Latemarch

Discussion at WUWT suggests that by about Feb 21 we should see an uptick if this is something that is near-normal. Odds are, we don’t have a long enough instrumented observation base to make a definitive decision, we are watching and learning. (I am influenced here, by experience with a mountain that moved beyond the usual and helped to re-write volcanology. I’d love to see a proper expertise weighted elicitation yielding a projection, but that’s not likely.)

As it is a red giant, it is thought to be end of life, and is due for supernova within the next 100,000 years.

As, normally we only see a supernova after it has happened, we do not know what precursors look like.

Some concerns have been expressed, that we may suffer x-ray bursts should that happen, but those tend to be aligned with the polar axis and such is thought to be unlikely. If it does go supernova, it will blaze up to high brightness, reaching that of the full moon approximately, then will fade away leaving behind a neutron star (or possibly a black hole, it seems to be borderline).

Here is a recent video:

This is a reminder that we are observing, we do not know to certainty. END

PS: Further digging gives a nigh on 40 year trend from cloudy nights. That suggests an earlier dip to mag 3. (Lower mag is brighter.)

Further data, notice 2012 as boxed

U/D, Feb 17: HT LM, here is a video courtesy ESO:

In the video, we see a discussion of shape shifting and surface dimming; Betelgeuse is anything but a compact nearly spherical ball:

Notice the surface dimming and apparent pinching in of the shape

25 Replies to “Betelgeuse dims, astrophysicists speculate

  1. 1
    kairosfocus says:

    Betelgeuse dims, astrophysicists speculate

  2. 2
    Latemarch says:

    Nice article at Watts Up With That.
    They think that it will declare itself in the next three weeks.

  3. 3
    kairosfocus says:

    A nice discussion.

  4. 4
    kairosfocus says:

    Did some adding, using WUWT and an image search. The best discussion on the web seems to be in Italian. I am not going to try to read Italian on my shaky Spanish!

  5. 5
  6. 6
    kairosfocus says:

    I added a clip. 2012 may be analogous to what is happening.

  7. 7
    Latemarch says:

    2012 dip was very quick unlike the current dip which seems more….how shall we say it….deliberate.
    I think that I read somewhere, though can’t find it now, that it is currently down in the 2.5 Magnitude range.
    The take home point is that we don’t actually know what a star does just before it goes supernova. We should know soon whether Betelgeuse turns around or not.

  8. 8
    kairosfocus says:

    LM, it is now 8:20+ pm here, I took a few steps outside and looked right up overhead. This is a relatively clear evening here; little or no light pollution. Betelgeuse does look like a mag 3, per my memory. The colour seems dull as a result, too. So, maybe the down 2.5 is relative to its mag 0 peak brightness baseline? It is about two weeks on from the above, on a sharp decline. KF

  9. 9
    kairosfocus says:

    PS: Was back outside, despite rain and cloud. Cleared a bit, definitely low, comparable to the belt and sword, well down from Rigel and of course Sirius. It was fun to do that on the line to someone 800 mi W and one degree N of here.

  10. 10
    Eugen says:

    Great information Kairos!

    One thing is certain for me, when it goes supernova it will be cloudy here for weeks πŸ˜€

  11. 11
    kairosfocus says:

    Eugen, I am of the view that until we see some clear sign of the unprecedented, we should hold the least likely outcome is supernova. Let’s see what happens come Feb 28. KF

  12. 12
    kairosfocus says:

    Just looked, Betelgeuse is dim but fine. KF

  13. 13
    Latemarch says:

    KF:
    Just looked, Betelgeuse is dim but fine. KF/
    For certain definitions of fine “;^)
    Looks Magnitude 2 to my eye.

  14. 14
    ET says:

    Yes, it will look fine right up until it doesn’t. And remember, the light that you see now left Betelgeuse just over 640 years ago!

  15. 15
    kairosfocus says:

    LM, Saiph next to Rigel in the outer envelope is a mag-2 [2.07], as are the belt stars. Meissa, tip of the triangle forming the head is a 3.3. B is comparable there. Normally it should be comparable to diagonally opposite Rigel, and should outshine Bellatrix in the W top corner at 1.64. We are all making rough visual comparisons. KF

    PS: A “normal” photograph http://astropixels.com/constel.....ri-01.html

  16. 16
    kairosfocus says:

    Folks, this is a live science exercise that anyone can take part in; Orion is literally the second most prominent constellation after Scorpio, which is instantly recognisable as a scorpion, with that curling tail. If things go bang, this will be a major news story. Why not, let’s watch and take opportunity to learn some basic Astronomy and cosmology (maybe, prominent stars in a grid too that allows us to find our way around the sky? Star map https://staratlas.com/ and Sky & telescope’s primer leaflet https://www.skyandtelescope.com/astronomy-resources/getting-started-in-astronomy/ ) Way back, I used the Hamlyn basics book. Dorling Kindersley has an affordable Astronomy coffee table book. A great trick is to use a strong flashlight as a pointer in the sky, the beam looks like a pointer. I suggest also learning how the galactic disk appears to us, with galactic centre in Sagittarius, the Archer. Orion, The Dipper and the pole star, Taurus with the Pleiades, Leo, and a few other sign-post constellations will orient us. A great exercise would be to track planets down, esp Mars, Jupiter and Venus, also a full cycle of the Moon. KF

  17. 17
    kairosfocus says:

    ET, yup, and not fine will be a bang in the sky for months, if it goes now; though I doubt. My thought is, a great opportunity to dip a toe into the oldest Science, the one where Amateurs play a significant role still.I think this augments basic Physics and Chem, sets up reflections on local and potential exo-biology and much more. A user friendly gateway to science. I also notice how some quite good reflectors in the 4 to 5-inch class are quite affordable now, and many at the next level are programmable. I suggest an 8 incher for getting really serious, though a 6 incher can do. And BTW there is a whole roll your own hobby, starting with grinding your own mirror. Nope, with reflectors like this I would not go refractor, just get a nice affordable pair of binoculars. Note, standard astro telescopes invert images, there are workarounds. KF

  18. 18
    ET says:

    I have two 4.5″ and one big 10″ (4′ focal length).. But winter has finally decided to show up here so I will have to wait.

  19. 19
    Latemarch says:

    Technical details (not for the faint of heart) and updates found at The Astronomer’s Telegram

    Agree KF. This does present an opportunity to actually engage in the science as it happens. Particularly as it will in all likelihood be a negative result. Demonstrating the importance of reporting negative results which all too often get neglected. It’s hard to get enthused enough to publish your “failures.” But negative results are just as important as the positive.

    If you are not familiar with the night sky there are several planetarium apps available for your phone my favorite is Star Walk II for the iPhone. I suspect it is available for Android but I haven’t checked.

    My favorite book for teaching yourself (or teaching children) is H.A. Rey’s The Stars. He simplifies the constellation outlines making them much easier to identify.

    Agee also KF with the suggestion for binoculars rather than starting with a telescope. There are huge number of objects that are easily found with a good set of low power, wide field binoculars. Low power is important as many things in the sky are larger than you might think and are better appreciated with a lower power and thus wider field. I like 7X50. Quick overview and how to choose a binocular here. If you will be out with others and particularly children then a parallelogram tripod mount which allows different people of different heights to easily view the same object makes observing quite pleasant. Parallelogram Mount

  20. 20
    kairosfocus says:

    ET, I see I am preaching to the assistant parson here. A 10 incher! I assume you have a camera mount to go with that much optical power. Do you have some shots of Betelgeuse? KF

  21. 21
    kairosfocus says:

    LM, again, I see you are active. Yes, 7 x 50 porro’s or roof prism will work for wide field viewing. 7 x 35 is a bit old fashioned now, 8 x 42 is more the typical. That people may have around and it will do a bit better than eyeball mark 1 without worries on tracking the moving celestial sphere. I also see the modern computerised scopes seem to almost set themselves up no need for equatorial mounts anymore it seems. But let us not underestimate eyeball mark 1. KF

    PS: This is good advice on using binoculars https://www.youtube.com/watch?v=xeyBcMkUaj8 and this is on tips for astronomy https://www.youtube.com/watch?v=UPoh76f60kA . My feeling is, a binocular helps familiarise with working with optics.

  22. 22
    kairosfocus says:

    Newbie scope setup https://www.youtube.com/watch?v=eoZyR7U8cuo He confused, longitude for latitude . . . the North Celestial pole is elevated above horizontal by your latitude, I assume northern hemisphere. Language is a bit rough.

  23. 23
    ET says:

    Nope. I do not have a camera mount on the 10″. Working on it, though. What I have is an Opteka 650-1300mm telephoto lens that comes with a doubler to boost it to 2600mm. I get great shots of the Moon with it. And it’s good for planets, too. I haven’t used it for Betelgeuse. But I may when it warms up a bit.

  24. 24
    Latemarch says:

    Also appears to have changed shape Astronomers watch dimming of supergiant star Betelgeuse.
    Also a short video from the ESO at the link.

  25. 25
    kairosfocus says:

    LM, thanks. I updated with the video and the ESO image of the shape change and dimming. Betelgeuse is one of the few stars we can image as an extended object. KF

Leave a Reply