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Betelgeuse

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ZPA
ZPA's picture
Betelgeuse

  I was curious to see if anyone else has noticed whether Betelgeuse seems to be brighter than average lately. I haven't tried making an estimate yet, but two nights ago I was up and outside just before dawn, and it seemed like Betelgeuse almost rivaled Rigel in brightness. I used to make regular visual estimates for it, but I haven't for years. It could very well just be my imagination!

SGQ
SGQ's picture
Betelgeuse

Dear Paul,

      thanks for pointing us out about Betelgeuse, that now is visible in the most tiring part of the night...

Betelgeuse at its rising is only about 4° higher than Rigel so I do not expect a big effect for the atmospheric extinction on Rigel with respect to Betelgeuse, but the fact that Rigel is bluer than Betelgeuse may play a key role for low altitudes. I am used to classify L=low an object when it is lower than 15° for these reasons (under clear sky obviously). My last observation of Alf Ori are of august 13-14, 2016 at magnitude 0.42, so only 0.29 magnitudes fainter than Rigel.

Good observations

Costantino

BRJ
BRJ's picture
Betelgeuze

Assuming that Betelgeuze's magnitude is currently +0.3 or +0.4, then this would be within about 0.1 magnitudes of its mean brightness over the course of the last 10,000 days.

J.Bortle   (BRJ)  

lmk
lmk's picture
Tough visual

The brightest stars like Betelgeuse are more difficult to estimate accurately than typical fainter stars, which one does by using binoculars and telescopes. The main issues are:

1. Lack of suitable nearby comp stars. To get good estimates, one needs two comps, a few tenths brighter and fainter, of similar color, to properly bracket the estimate. And, the comps have to be nearby enough you can orient all the stars simultaneously at about the same distance from your fovea. The "best" comps for Betelgeuse are probably Rigel (V=+0.15) and Procyon (V=+0.36) on the bright side, and Aldeberan (V=+0.86) on the faint side. None of  these are ideal, due to the extreme color difference between the hot, blue type B Rigel, and the cool, red type M Betelgeuse. Procyon is a little better color-wise, but it is located further away in the sky. Aldeberan is the most similar in color to Betelgeuse, but is also some distance away. So, you have difficulties with color mismatches, and inconvenient positions and distances to make a good estimate.

2. It is impractical to try defocus to help improve estimate accuracy with naked-eye stars.

3. The large angular separation of the comps means that atmospheric extinction becomes significant, and needs to be accounted for, plus any other differences in the sky background from one spot to another. Such as different background light pollution levels, or clouds, transparency, etc.

4. Purkinje effect. These bright stars can be estimated with direct vision using the cones in the fovea, but you must then switch your view back and forth between the comps, you can't compare them simultaneously, as with typical fainter stars in a small fov. And, you must not "stare" at the bright red star, to keep short quick glances at all of them.

So, taking all these factors into account, you can see that accurate estimates of Betelgeuse are fraught with many difficulties that are not found with the typical telescopic stars we usually estimate to +/-0.05 or +/-0.10 magnitudes!

Betelgeuse would be an excellent star for small instrument PEP however...

Mike

 

Jorge1977
Jorge1977's picture
At its brightest

Hi guys: 

Very interesting ideas! The measurement of the red brightests stars is a very interesting theme for me.

Paul: Indeed, it seems that Betelgeuse is now at its brightest point in the last years. 

In fact, I don,t remember a brighter Betelgeuse than now, almost since the early 90,s, when I started in Astronomy...It seems as bright as Procyon and nearly Rigel.

Good skyes!

Jorge

 

HRHA
HRHA's picture
looking at past visual time series for Betelgeuse

I'm working with a couple statisticians, Mark Heiple and Jamie Riggs, to learn about working with Red Giant star time series and light curves. Mostly this work is done in the R statistical language.  We've been looking through a catalog (see Levesque.pdf)  of about 60 red giant stars, of which Betelgeuse is one, with data going back to 1914!.  This catalog was pulled last January and needs to be updated, but it includes all observations for these stars. One method we're trying out is to average over a weekly time span all visual (Vis.) observations.  There are no CCD observations as they tend to have too wide a range of magnitudes.  

Attached are some graphs and spline fits to these weekly Vis. data. From this it does look like Betelgeuse has had an increase in magnitude the last few years.  

One question we'd like to answer would be how do we 'segment' this series?  If we knew where to break and segment these data we could use a time series regression with indicator variables marking discontinuities in the series. The response would be the magnitude and the predictors would be time and indicator variables to demarcate the segments. Significant differences of the slopes and intercepts among the segments would suggest changing magnitudes.

Rodney

WI
The simple answer to your

The simple answer to your question is, Yes, Betelgeuse is a bit brighter than this time last season and about as bright as I have ever seen it. The difference is subtle, as it always is with Betelgeuse, just a tenth or two this way or that. The color effect is large for some observers. But everything considered, Betelgeuse is brighter.

Jorge1977
Jorge1977's picture
Very interesting

Very interesting docs Rodney. 

Than you for share it with us.

HRHA
HRHA's picture
up-to-date data on Betelgeuse

Sara was kind enough to pull all data as of 1st of November.  I've done some 'exploratory' analysis using what is called Shannon noise-burst ratios to try and identify where there are slope changes in the time series.  It uses two data streams, one the magnitude (Vis.) time series the second is the period estimates; in this case 388.5 weeks!  (Almost half the period of the sun's solar cycle).  

Those little blue spikes in this graph that drop below zero may be good start and end times for a 'segment' of observations before the noise cause another burst (drop below zero and a change in the slope from the previous segment).  You can see in the early years of sparse data there was a lot of noise.  But, if these observations are (were) accurate then Betelguse was pretty bright back in the 1920's and 1930's. 

Rodney

 

Jorge1977
Jorge1977's picture
Not period

This is very interesting. If these data are accurate, Betelegeuse has not evident period apparently.

It seems almost irregular in its brightness shift.

However I,ve read about a,more or less, seven years period in different publications.

 

Jorge

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