APOD: Betelgeuse Eclipsed (2023 Dec 15)

[APOD Robot]

Betelgeuse Eclipsed

Explanation: Asteroid 319 Leona cast a shadow across planet Earth on December 12, as it passed in front of bright star Betelgeuse. But to see everyone's favorite red giant star fade this time, you had to stand near the center of the narrow shadow path starting in central Mexico and extending eastward across southern Florida, the Atlantic Ocean, southern Europe, and Eurasia. The geocentric celestial event is captured in these two panels taken at Almodovar del Rio, Spain from before (left) and during the asteroid-star occultation. In both panels Betelgeuse is seen above and left, at the shoulder of the familiar constellation Orion. Its brightness diminishes noticeably during the exceedingly rare occultation when, for several seconds, the giant star was briefly eclipsed by a roughly 60 kilometer diameter main-belt asteroid.

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[shaileshs]

That day I tried to get a "live" video streaming, I looked and searched and searched.. got none. It was disappointing. From the photo (right frame), seems the passing was subtle (not so obvious, not so conspicuous) to naked eyes (or even small binoculars) ? It's strange that people didn't know whether eclipsing going to be full or ring type or concentric circle type or at different angle and no one knew how long it was going to last (some said 8 seconds, some said 15 seconds..). Seems there was no good data/prediction - neither on size of asterois nor angle (precise passing path) from various viewing locations in that narrow belt... Oh well..

[AVAO]

That day I tried to get a "live" video streaming, I looked and searched and searched.. got none. It was disappointing. From the photo (right frame), seems the passing was subtle (not so obvious, not so conspicuous) to naked eyes (or even small binoculars) ? It's strange that people didn't know whether eclipsing going to be full or ring type or concentric circle type or at different angle and no one knew how long it was going to last (some said 8 seconds, some said 15 seconds..). Seems there was no good data/prediction - neither on size of asterois nor angle (precise passing path) from various viewing locations in that narrow belt... Oh well..

https://www.youtube.com/watch?v=QPIz74AWf8A

9.050 Aufrufe 12.12.2023
Last night, the asteroid Leona passed in front of the red supergiant Betelgeuse, one of the brightest stars of the famous constellation Orion, but this was only visible from a very narrow corridor covering Asia, Europe and America. Such event is extremely rare for such a bright star: once in an astronomer lifetime!
Despite high clouds covering southern Spain, I clearly saw Betelgeuse darkening for about ten seconds from the Alicante area.
Betelgeuse is much larger than the Sun: placed at the center of the solar system, it would engulf the orbits of Mercury, Venus and Mars. Within 100,000 years (a very short time on the scale of the life of stars), it could explode in a supernova. Since Leona was not large enough to hide it completely, the occultation occurred as an annular eclipse and this is the reason why Betelgeuse did not disappear but only darkened.

Thierry Legault - www.astrophoto.fr

40:45 https://www.youtube.com/watch?v=ik746bduNAI
https://www.youtube.com/watch?v=SWHkEqFgtmA

[Rauf]

Click to play embedded YouTube video.

[Ann]

Click to play embedded YouTube video.

Thanks, Rauf! Seeing a video really helped. I must say I'm a little disappointed, though - I sort of imagined that the light of Betelgeuse would be completely blotted out by asteroid 319 Leona. Guess we can't have everything!

Oh, and thank you too, Jac!

Ann

[Dave4Gee]

G'day,

You got the shadow path direction wrong.
The shadow started traversing the Earth's surface at 01:08 UT near Turkmenistan, then crossed Turkey, Greece, Italy, Spain, US-Florida, then ended at 01:26 UT near Mexico.
Currently there are nearly 40 observers with formal reports submitted.

Regards
Dave Gault
Kuriwa Observatory

[Rauf]

Click to play embedded YouTube video.

Thanks, Rauf! Seeing a video really helped. I must say I'm a little disappointed, though - I sort of imagined that the light of Betelgeuse would be completely blotted out by asteroid 319 Leona. Guess we can't have everything!

Oh, and thank you too, Jac!

Ann

Your welcome, Ann

If Betelgeuse appears larger than Leona, even a central occultation will end up resembling an annular solar eclipse: The star won’t be completely blocked even at the centerline of the shadow’s path. If Betelgeuse is more on the smaller side though, and the Leona shape model proves to be correct, there will be a narrow strip of “totality” just a few kilometers wide around the center line, where the star completely disappears for a few seconds. (Leona itself will only be visible in large telescopes, as its brightness is 14.3 mag). The farther you are from the center line, the lesser the magnitude drop you'll see and the briefer the whole event.

It seems no one was sure if Betelgeuse was going to be totally eclipsed or just partially. I guess we found out

[Christian G.]

Click to play embedded YouTube video.

Quite impressive to see this unfold in real time! Whoever happened to be gazing at Betelgeuse at that moment without knowing about the eclipse must have thought "That's it!! She's blowing up!!"

[shaileshs]

Thanks to folks posting video/link of occultation. One question remains - why the brightness of star is seen lowering equally (full 360 deg, round) and not partially just where the occultation happened ? Whenever we see moon/Sun getting eclipsed like that - partially, at an angle, cutting it's visual surface - we see little bit of overall brightness going down but more obvious is seeing sliced portion (one slice normal bright, other slice dark). In YT videos above, whole 360 deg brightness goes down, we can't see slices..

[Chris Peterson]

Thanks to folks posting video/link of occultation. One question remains - why the brightness of star is seen lowering equally (full 360 deg, round) and not partially just where the occultation happened ? Whenever we see moon/Sun getting eclipsed like that - partially, at an angle, cutting it's visual surface - we see little bit of overall brightness going down but more obvious is seeing sliced portion (one slice normal bright, other slice dark). In YT videos above, whole 360 deg brightness goes down, we can't see slices..

Because the star is not resolved. Optically, it is a point source, larger in the image because of diffraction and scattering. Both the asteroid and the star subtend angles much smaller than a single pixel.

[johnnydeep]

I can't visualize why Betelgeuse isn't eclipsed the same amount for all points on Earth for which Betelgeuse and the asteroid are visible at all. That is, why doesn't the shadow cover the entire Earth to an equal extent? The actual eclipse event happened at the distance of the asteroid, which is much much farther away than the Moon!

[Chris Peterson]

I can't visualize why Betelgeuse isn't eclipsed the same amount for all points on Earth for which Betelgeuse and the asteroid are visible at all. That is, why doesn't the shadow cover the entire Earth to an equal extent? The actual eclipse event happened at the distance of the asteroid, which is much much farther away than the Moon!

The eclipse happens on a line between the star and the asteroid. A line about the same width as the asteroid.

[johnnydeep]

I can't visualize why Betelgeuse isn't eclipsed the same amount for all points on Earth for which Betelgeuse and the asteroid are visible at all. That is, why doesn't the shadow cover the entire Earth to an equal extent? The actual eclipse event happened at the distance of the asteroid, which is much much farther away than the Moon!

The eclipse happens on a line between the star and the asteroid. A line about the same width as the asteroid.

Ok, I can see that now: the light from the star is essentially parallel and wherever the asteroid blocks it we would see it eclipsed ("rock in a stream" effect). But why doesn't Betelgeuse blink totally off and on again instead of gradually dimming and brightening? Because it's not a point source in reality due to multiple CCD pixels being affected?

Also, is there a penumbral path as well as a totality path?

[Chris Peterson]

I can't visualize why Betelgeuse isn't eclipsed the same amount for all points on Earth for which Betelgeuse and the asteroid are visible at all. That is, why doesn't the shadow cover the entire Earth to an equal extent? The actual eclipse event happened at the distance of the asteroid, which is much much farther away than the Moon!

The eclipse happens on a line between the star and the asteroid. A line about the same width as the asteroid.

Ok, I can see that now: the light from the star is essentially parallel and wherever the asteroid blocks it we would see it eclipsed ("rock in a stream" effect). But why doesn't Betelgeuse blink totally off and on again instead of gradually dimming and brightening? Because it's not a point source in reality due to multiple CCD pixels being affected?

Also, is there a penumbral path as well as a totality path?

Neither the asteroid nor Betelgeuse are physically point sources. But both are optically point sources to the equipment used to observe the eclipse here on the ground. So if the asteroid subtends a smaller physical angle than Betelgeuse, we wouldn't see the star completely disappear. And no matter what the actual size of the asteroid, the physical occultation takes time. Which we see as a dimming then brightening.

Imagine a total solar eclipse that was unresolved. All you'd need for that would be a one pixel camera. Like a light meter. You'd have no idea about the nature of the eclipse, like the direction of movement of the bodies. All you'd get would be a dimming then a brightening.

[johnnydeep]

The eclipse happens on a line between the star and the asteroid. A line about the same width as the asteroid.

Ok, I can see that now: the light from the star is essentially parallel and wherever the asteroid blocks it we would see it eclipsed ("rock in a stream" effect). But why doesn't Betelgeuse blink totally off and on again instead of gradually dimming and brightening? Because it's not a point source in reality due to multiple CCD pixels being affected?

Also, is there a penumbral path as well as a totality path?

Neither the asteroid nor Betelgeuse are physically point sources. But both are optically point sources to the equipment used to observe the eclipse here on the ground. So if the asteroid subtends a smaller physical angle than Betelgeuse, we wouldn't see the star completely disappear. And no matter what the actual size of the asteroid, the physical occultation takes time. Which we see as a dimming then brightening.

Imagine a total solar eclipse that was unresolved. All you'd need for that would be a one pixel camera. Like a light meter. You'd have no idea about the nature of the eclipse, like the direction of movement of the bodies. All you'd get would be a dimming then a brightening.

Sigh. Still have trouble with this. So, Betelgeuse isn't a point source (it subtends an angle greater than 0), so more of its light can be blocked as the asteroid (also not a point source) gradually passes more and more in front of it. But if it was a point source, then it would blink on/off instead of dim/brighten, no?

[Chris Peterson]

Ok, I can see that now: the light from the star is essentially parallel and wherever the asteroid blocks it we would see it eclipsed ("rock in a stream" effect). But why doesn't Betelgeuse blink totally off and on again instead of gradually dimming and brightening? Because it's not a point source in reality due to multiple CCD pixels being affected?

Also, is there a penumbral path as well as a totality path?

Neither the asteroid nor Betelgeuse are physically point sources. But both are optically point sources to the equipment used to observe the eclipse here on the ground. So if the asteroid subtends a smaller physical angle than Betelgeuse, we wouldn't see the star completely disappear. And no matter what the actual size of the asteroid, the physical occultation takes time. Which we see as a dimming then brightening.

Imagine a total solar eclipse that was unresolved. All you'd need for that would be a one pixel camera. Like a light meter. You'd have no idea about the nature of the eclipse, like the direction of movement of the bodies. All you'd get would be a dimming then a brightening.

Sigh. Still have trouble with this. So, Betelgeuse isn't a point source (it subtends an angle greater than 0), so more of its light can be blocked as the asteroid (also not a point source) gradually passes more and more in front of it. But if it was a point source, then it would blink on/off instead of dim/brighten, no?

Right. The smaller the angular size of the star, the faster the occultation will occur. No star is physically a point source, of course, but most are small enough or far enough away that the interval of dimming and then brightening will be so short as to be unresolved temporally... and therefore appear instantaneous.

[johnnydeep]

Neither the asteroid nor Betelgeuse are physically point sources. But both are optically point sources to the equipment used to observe the eclipse here on the ground. So if the asteroid subtends a smaller physical angle than Betelgeuse, we wouldn't see the star completely disappear. And no matter what the actual size of the asteroid, the physical occultation takes time. Which we see as a dimming then brightening.

Imagine a total solar eclipse that was unresolved. All you'd need for that would be a one pixel camera. Like a light meter. You'd have no idea about the nature of the eclipse, like the direction of movement of the bodies. All you'd get would be a dimming then a brightening.

Sigh. Still have trouble with this. So, Betelgeuse isn't a point source (it subtends an angle greater than 0), so more of its light can be blocked as the asteroid (also not a point source) gradually passes more and more in front of it. But if it was a point source, then it would blink on/off instead of dim/brighten, no?

Right. The smaller the angular size of the star, the faster the occultation will occur. No star is physically a point source, of course, but most are small enough or far enough away that the interval of dimming and then brightening will be so short as to be unresolved temporally... and therefore appear instantaneous.

Somehow it was much easier for me to see that a planet orbiting a far away star will dim its when it passes in front of it - that seems so obvious! But a nearby asteroid - although much closer to Earth and much farther from the star- can do the same exact thing! And in fact, it does it better because it subtends a greater angle the closer to us it is.