Betelgeuse Fainting

[Superluminal]

Another Astronomical Telegram from Edward Guinen.
http://www.astronomerstelegram.org/?read=13439

[CJSF]

Seems like things have nearly leveled off between 1.60 and 1.65 mag, with slight fluctuations over the last week or so (though I see AAVSO has it at ~1.69!). I wonder how quickly it will increase in brightness, once it reaches minimum.

CJSF

[antoniseb]

Seems like things have nearly leveled off between 1.60 and 1.65 mag, with slight fluctuations over the last week or so (though I see AAVSO has it at ~1.69!). I wonder how quickly it will increase in brightness, once it reaches minimum.

CJSF

We can look at previous minima to get a good estimate. Previous minima were roughly flat for five to eight weeks, and then rose back to normal brightness over the course of a few months.

[antoniseb]

It isn't statistically significant because it is only one observation, and it is an outlier, but someone just reported a visual preverified magnitude of 2.2, which is 0.2 lower than any previous report.

[CJSF]

Just looking tonight, Betelgeuse still seemed noticeably dimmer than Rigel and about the same as Bellatrix, which seems to fit in with the ~1.64 observations qualitatively.

CJSF

[CJSF]

Dr. Plait wrote about some of the recently released imagery and results from observations late last year from the Very Large Telescope. Weirder and weirder.

https://www.syfy.com/syfywire/betelg...-it-is-dimming

The dimming seems to be asymmetric.

CJSF

[Superluminal]

Just looking tonight, Betelgeuse still seemed noticeably dimmer than Rigel and about the same as Bellatrix, which seems to fit in with the ~1.64 observations qualitatively.

CJSF

Had a really good sky last night and Betelgeuse looked brighter that Bellatrix.

[Superluminal]

Dr. Plait wrote about some of the recently released imagery and results from observations late last year from the Very Large Telescope. Weirder and weirder.

https://www.syfy.com/syfywire/betelg...-it-is-dimming

The dimming seems to be asymmetric.

CJSF

Astronomers believe Betelgeuse may have recently consumed a companion star. I wonder if the bright spot is actually the companion inside the thin outer atmosphere of Betelgeuse. And Betelgeuses odd shape is because the star is still convulsing from the merger?

[Superluminal]

83906486_2885907791459312_6987265917704994816_o
Betelgeuse through a C-8 Schimt-Cass. Taken with a cell phone. Probably not holding the camera very steady or Betelgeuse is really odd.

[Roger E. Moore]

A paper from 1997 on dimming and changes in surface brightness detected in 1994-1995. "We conclude that the fading was due to a global expansion and cooling of the photosphere."

https://ui.adsabs.harvard.edu/abs/19....819W/abstract

The changing face of Betelgeuse
Wilson, R. W. ; Dhillon, V. S. ; Haniff, C. A.
November 1997

We describe a sequence of four optical interferometric observations of Betelgeuse, obtained using the non-redundant aperture mask method at the 4.2-m William Herschel Telescope on La Palma between 1994 November and 1995 January. The observations reveal complex asymmetries in the brightness distribution of the star, detected at a very high signal-to-noise ratio. Adequate modelling of the intensity structure requires at least three bright spots superposed on the stellar disc. Changes in the relative flux and positions of the spots are evident over the 8-week period spanning the observations. The brightness and maximum size of these features are consistent with convective surface hotspots. Simultaneous photometry of the integrated light of Betelgeuse shows a large and rapid dimming over the same period, which is not correlated with any change in the bright features. We deduce that, in this instance, the photometric variation did not result from localized convective activity associated with the spots. The interferometric data also show strong evidence for structure on a scale much larger than the photospheric diameter, which has not been present in previous observations over recent years. We attribute this new component to scattering from a newly formed dust halo, with a minimum angular diameter of approximately 0.3 arcsec. Since the brightness of this structure relative to the stellar disc did not change significantly throughout our observations, it is unlikely that the dimming of the star resulted from increased absorption by the dust halo. We conclude that the fading was due to a global expansion and cooling of the photosphere.

[CJSF]

Latest plot on the Betelbot Twitter feed is starting to show a tell-tail bottoming out today - very near to the predicted ~420 day cycle. Might be too early to tell, but looks intriguing.

https://twitter.com/betelbot/status/...991744/photo/1

CJSF

[antoniseb]

Latest plot on the Betelbot Twitter feed is starting to show a tell-tail bottoming out today - very near to the predicted ~420 day cycle. Might be too early to tell, but looks intriguing.

https://twitter.com/betelbot/status/...991744/photo/1

CJSF

Looking at the AAVSO data, it is still well within the margin of error, but yes. especially looking at the red and blue filtered observations, there seems to be a mild tick upward.

[Roger E. Moore]

A melancholy editorial on the possible fate of Betelgeuse: we will miss you. Orion won't be the same.

https://slate.com/technology/2020/02...-changing.html

[Van Rijn]

A melancholy editorial on the possible fate of Betelgeuse: we will miss you. Orion won't be the same.

https://slate.com/technology/2020/02...-changing.html

Yes, but I would still like to see a supernova. Meh, it probably isn’t going to happen for many thousands of years anyway.

[CaptainToonces]

I looked at it tonight--no brighter than Bellatrix and well dimmer than Procyon.

Looks like the dyson sphere is nearly complete.

[antoniseb]

I looked at it tonight--no brighter than Bellatrix and well dimmer than Procyon.

Looks like the dyson sphere is nearly complete.

Because the color is different, I couldn't tell if its brightness was greater or less than the left and center belt stars. Definitely brighter than the right one. I also can't tell from Bellatrix. Thanks to the AAVSO regulars who look and report these things regularly, and know how to judge these brightness differences, or have the electronics to measure it.

[George]

I'm curious why there aren't reliable amateur photometers like this one? The meter result would show a relative difference and it might be possible to quantify the difference if there are equally bright reference stars nearby.

In the '70s, I designed and built a cheapy by simply looking at what Radio Shack had to offer (sensor and transistors). It was applied to a laser (for new sewer lines) to prove to the laser manufacturer that a new laser sent to us was much weaker than it should be. They had "never heard" that a new laser could be weaker than the other new lasers, apparently. It did get us a new laser.

[StupendousMan]

I'm curious why there aren't reliable amateur photometers like this one? The meter result would show a relative difference and it might be possible to quantify the difference if there are equally bright reference stars nearby.

Why so few photomultiplier tubes in current use? In part, because the electronics required to make such devices are close to extinct. In larger part, because a photoelectric photometer does just one thing (measure the relative brightness of stars), while a camera -- film or electronic -- can do many things. In addition, it's a lot easier to use a camera than a photometer.

[Hornblower]

I took a look at dusk as the brighter stars were becoming visible. Betelgeuse and Bellatrix looked equal within my observing uncertainty, as they have for the past few weeks. While not suitable for quantitative comparison with a stars over a range of brightness, the bright sky made small differences, if any, very apparent.

[George]

Why so few photomultiplier tubes in current use? In part, because the electronics required to make such devices are close to extinct. In larger part, because a photoelectric photometer does just one thing (measure the relative brightness of stars), while a camera -- film or electronic -- can do many things. In addition, it's a lot easier to use a camera than a photometer.

Agreed, but my point wasn't the type of sensors in use but the methodology of using a simple, low-cost, sensor for a photometry approach over the visual method. Given that a relative result, not an accurate flux rate value, should work fine with minimal calibration with one or more reference stars. The spectral sensitivity could, however, add a little to the effort to convert to a visual magnitude value, but even this shouldn't be that much of a problem to establish initially.

The reference I gave is an old paper that was offering something similar, but decades ago, so perhaps there is something more modern and even less expensive.

[StupendousMan]

A standard photoelectric photometer is considerably more complicated to use, in the field, than a camera. I suspect that the operating procedure is complex enough to make it unattractive to any but the most dedicated amateurs.

For example, a typical session might involve something like this:

- set up equipment
- point telescope toward target
A: - center target star on crosshair
- flip mirror to send light onto detector
- integrate for 3 seconds
- unflip mirror
- slew 0.5 degrees to "sky" area
- verify that no stars fall into photometer's field
- flip mirror
- integrate for 3 seconds
- unflip mirror
B: - slew back to target
- repeat steps A-B four more times

- slew scope to comparison star
- repeat previous steps, this time measuring comparison star

- slew scope to check star
- repeat previous steps, this time measuring check star

That should provide the data from one a single measurement of the target star can be extracted.

[antoniseb]

It may still be only low statistics, but Betelgeuse looked slightly brighter than Bellatrix to me last night, AND the majority of the AAVSO observations in the last two days have put it at magnitude 1.5 which is up from the 1.65 (or so which was the bottom so far). There are still a lot of observations dimmer than 1.5, and not many brighter, so it is also possible that many people know that this week is when the rebrightening should begin, and that it isn't different from last week.

[Superluminal]

It may still be only low statistics, but Betelgeuse looked slightly brighter than Bellatrix to me last night, AND the majority of the AAVSO observations in the last two days have put it at magnitude 1.5 which is up from the 1.65 (or so which was the bottom so far). There are still a lot of observations dimmer than 1.5, and not many brighter, so it is also possible that many people know that this week is when the rebrightening should begin, and that it isn't different from last week.

I observed last night for the first time in several days, thanks to the February weather. Betelgeuse did seem a tad (is that a scientific term?) brighter than Bellatrix. Could be bouncing back.

[kpatz]

I observed last night for the first time in several days, thanks to the February weather. Betelgeuse did seem a tad (is that a scientific term?) brighter than Bellatrix. Could be bouncing back.

I looked tonight at dusk when it was just starting to be visible and I could see Betelgeuse just edging out Bellatrix in brightness. So you're probably right, it's starting to brighten. Right on schedule according to some websites.

[Superluminal]

Maybe I've been a bit lucky, I've had two exceptionally clear nights in a row. Orion is starting to look like it's old self again.

[Superluminal]

According to Edward Guinnen of Villanova, Betelgeuse has started to brighten again on schedule.
http://www.astronomerstelegram.org/?read=13512
Observations of all kinds continue to be needed to understand the nature of this unprecedented dimming episode and what this surprising star will do next.

[Roger E. Moore]

Another photo of Orion my wife took, about a week ago with her cell phone. Betelgeuse still there. Sirius in lower left.

[StupendousMan]

The latest Astronomer's Telegram notes that even though the visual brightness of Betelgeuse has changed sharply over the past few years, its infrared brightness has not.

http://www.astronomerstelegram.org/?read=13518

[CaptainToonces]

The latest Astronomer's Telegram notes that even though the visual brightness of Betelgeuse has changed sharply over the past few years, its infrared brightness has not.

http://www.astronomerstelegram.org/?read=13518

Does that mean we are talking about something like a dust cloud obscuring the visible range?

[antoniseb]

Does that mean we are talking about something like a dust cloud obscuring the visible range?

The dust itself would have an IR brightness from the heat of the visible light it blocked.