Betelgeuse dimmer

[Nigella Bryant]

Hi all, intrigued by the news betelgeuse is much dimmer I went outside to have a look this evening. To my dismay it certainly isn't the star it used to be and significantly dimmer. I did do a quick 30sec image with my mobile phone. Can't really distinguish how much dimmer it is using a mobile. If it's clear in the coming few night's I'll get my dslr out and have a go at imaging it wide field. But for now just a mobile image. 

[Paul M]

Nice image. Which phone was used? I've read that one of the latest Huwawei phones has a "bulb" shutter setting suitable for astro.

[Nigella Bryant]

1 minute ago, Paul M said:

Nice image. Which phone was used? I've read that one of the latest Huwawei phones has a "bulb" shutter setting suitable for astro.

It's an older HUAWEI P10. You can use it in Pro mode to set iso and exposure. I used iso640 and a 30sec exposure. I set a 5sec delay on the shutter to stop shaking. Huawei are certainly good for astrophotography. 

[Les Ewan]

Don't worry it will come back . The magnitude of Betelgeuse has historically been hard to estimate because of its redness but I've seen estimates of its fluctuations vary from 0.2-1.4 magnitude which is as bright as Capella to as dim as Regulus. To make matters worse during the fainter part of its cycle its spectrum is even redder and the human eye is less sensitive to red light.

Its said that Betelgeuse is overdue to go supernova and some Youtube comments suggest that this latest dimming could be a prelude to it exploding ,but given the historic magnitude estimates over the last couple of hundred years I wouldn't write the star off just yet.

[PeterW]

Definitely something to engage the public with (the visual difference bit, less so the supernova bit). We eagerly await the next few weeks... more dim or return to former brightness? Shown the kids for them to remember.

Peter

[Les Ewan]

A lot of people would like to see Betelgeuse go supernova now just for the spectacle of a star as bright as the full Moon.Personally I wouldn't it would be like wishing the death of an old friend. After a few weeks when it disappeared from view most of us would really miss it, Orion just would not be the same,although future generations of astronomers may well have a bright new planetary nebula to enjoy. 

[Nigella Bryant]

I'm kind of torn, I'd miss the familiar shape of Orion but then again I'd like to see a supernova up close and personal as Betelgeuse would be. I also wonder when amateur equipment would be able to image the expanding gas cloud if it did explode. So there's plus and minus to it.

It still is amazing to me to see how much betelgeuse has decreased in brightness. I've never witnessed it to this extent before. 

[Paul M]

Maybe we should be prepared; think the unthinkable - Orion without Betelgeuse.

So not much of a hunter any more. I think the remnant constellation would be more of a shopping trolley. Maybe the new constellation could be called "Aldi"?

[PeterW]

Or a pushchair.... Orion without his armpit?!

Peter

[Nigella Bryant]

12 minutes ago, PeterW said:

Or a pushchair.... Orion without his armpit?!

Peter

Definitely the pushchair, lol. 

[Les Ewan]

Orion is next to Eridanus a modern asterism can be made of a shopping trolley dumped  in a river!

[Sunshine]

I just snuck out for a look at big B, I have been reading about how much it has dimmed but, tonight was the first time I have been able to see it. 

WOW is it ever fainting, I wasn't sure what to expect, as I walked out my door I could see what I was sure was Orion's shoulders looming over 

the rooftop but, I had to walk further out to confirm I was seeing Orion. Betelgeuse looked so underwhelming compared to what I am used to seeing,

it looks about the same as Bellatrix, this fainting has been going on for weeks, we will see what happens in the coming weeks, awfully exciting really.

[carastro]

It's difficult for me living in Bortle 8, as all the stars are dimmer, in fact I can only see the brightest magnitude stars where I live.  But even then I think Betelguese looks dimmer than usual now you mention it.  Must take a closer look.

All this talk about it going supernova, it would be quite ironic if this happened during the summer months when we can't even see it.  (Or winter months if you live in the Southern hemisphere).

Carole 

[michael.h.f.wilkinson]

On 02/01/2020 at 13:54, Les Ewan said:

A lot of people would like to see Betelgeuse go supernova now just for the spectacle of a star as bright as the full Moon.Personally I wouldn't it would be like wishing the death of an old friend. After a few weeks when it disappeared from view most of us would really miss it, Orion just would not be the same,although future generations of astronomers may well have a bright new planetary nebula to enjoy. 

Strictly speaking, it would be a supernova remnant, not a planetary nebula. I did some back-of-the-envelope calculations based on M1, which is a 1,000 year old SNR, at almost exactly 10 times the distance to Betelguese. It is some 420x290 arcsec. Assuming linear expansion, that means about 0.3 - 0.4" expansion per year, which in the case of Betelguese would translate to 3 - 4" per year. Quite spectacular, and easily resolved in amateur kit. 

[Walshie79]

Just been out for a look, first clear night since I heard about this.

It's much dimmer than "normal". I've known it be as bright as Rigel, but now as I see it's: 

Clearly fainter than Aldebaran

Slightly fainter than Pollux

Still brighter than Bellatrix, but not by much

Will compare it to Regulus when that rises to a decent altitude.

 

[Walshie79]

And just now I could briefly see Betelgeuse and Regulus simultaneously; I think Betelgeuse is fainter. Also Betelgeuse is not visible through thin clouds that keep swirling around in front of the stars while the other bright stars nearby (Rigel, Procyon, Sirius) are.

I'd put Betelgeuse at around 1.4 at the moment

[Nigella Bryant]

2 hours ago, Walshie79 said:

And just now I could briefly see Betelgeuse and Regulus simultaneously; I think Betelgeuse is fainter. Also Betelgeuse is not visible through thin clouds that keep swirling around in front of the stars while the other bright stars nearby (Rigel, Procyon, Sirius) are.

I'd put Betelgeuse at around 1.4 at the moment

To quote Jeremy Shears, in the late 70's it reached magnitude 1.5 . Recent observations put it at a similar level between 1.3 and 1.5. So your estimate is spot on.  If it goes any deeper it'll be the deepest dip ever. It will probably follow the same pattern as in the 20's, 40's and 70's of the 20th century and begin to brighten again rather than explode.  It's still fascinating to observe this. 

[Whirlwind]

On 02/01/2020 at 05:37, Les Ewan said:

Its said that Betelgeuse is overdue to go supernova and some Youtube comments suggest that this latest dimming could be a prelude to it exploding ,but given the historic magnitude estimates over the last couple of hundred years I wouldn't write the star off just yet.

The youtube comments that it is about to blow are all conjecture without any real basis or evidence.  There is little historic data on pre-supernova sequences (and indeed could be different dependent on mass of the progenitor).  Betelgeuse is already a known variable likely due to pulsations and large dark convection cell spots (like our own stellar spots but much larger).  Alternatively it could have recently shed a lot of dusty material that is now in out line of sight (though I've read that the luminosity reduction is the same across all wavelengths and if it was dust then we'd expect wavelengths to be dimmed by different amounts).  So it is probably just a case of multiple periodic cycles lining up - it's pulsated to a smaller size and there is a dark convective cell on the visible face to us.  To put things into context if the luminosity change was *just* due to a size reduction then a 1 magnitude change would equate to a current radius about 65% of what it was in October (and assuming no temperature change). 

[Merlin66]

Current spectroscopic observations do not show a significant change across the visual spectrum...................

[Les Ewan]

I'm not great at variable star estimates and don't do many but studying Betelgeuse this evening using Pollux,Castor and Bellatrix I estimate Betelgeuse to be magnitude 1.2-1.3 just now.

To me its fainter than Pollux but brighter than Castor and Bellatrix.

 

[RT65CB-SWL]

I went to take my lady-friend's son to LGW lastnight, (12th Jan 2020), as he has six weeks of cabin-crew training with an airline that has its base/hub there. 

When I dropped my lady-friend back to her home in Hounslow, there was a clear patch of sky around Orion and I did notice that Betelgeuse was brightness was dimmer of about one magnitude to what it usually is.

When I arrived at my home, I had planned to take some photo images as part of the OU/FutureLearn [Orion] course / week 1 assignment, it was cloudy.

[Les Ewan]

During clear spell  while walking the dog I got the impression Betelgeuse  was  just a shade brighter last night perhaps magnitude 1.1-1.2. This is not a scientific observation just a impression.

There was a gale at the time so the sky was swept clean and very transparent (between the clouds) with no Moon.

PS For any newbies out there astronomic observations can be made without a dog!😁

[Stu]

I'm no expert at this, but last night I thought it only a shade brighter than Bellatrix so put it at mag 1.5. That's probably on the dim side I suspect, has anyone got the true current magnitude?

[Nigella Bryant]

2 hours ago, Stu said:

I'm no expert at this, but last night I thought it only a shade brighter than Bellatrix so put it at mag 1.5. That's probably on the dim side I suspect, has anyone got the true current magnitude?

This last dimming cycle is quite unusual as the star is at record low brightness, and this dimming is significant enough to be seen by the naked eye. The latest data has the magnitude of the star at 1.5, which is 0.2 magnitudes dimmer than the previous known record of 1.3 magnitudes in 1927 and 1941.

[Stu]

16 minutes ago, Nigella Bryant said:

This last dimming cycle is quite unusual as the star is at record low brightness, and this dimming is significant enough to be seen by the naked eye. The latest data has the magnitude of the star at 1.5, which is 0.2 magnitudes dimmer than the previous known record of 1.3 magnitudes in 1927 and 1941.

Thanks for that, I was bang on then 👍

Where did you get the info from, out of interest.