Dimming of Betelgeuse explained

These images, taken with the SPHERE instrument on ESO’s Very Large Telescope, show the surface of the red supergiant star Betelgeuse during its unprecedented dimming, which happened in late 2019 and early 2020. The image on the far left, taken in January 2019, shows the star at its normal brightness, while the remaining images, from December 2019, January 2020, and March 2020, were all taken when the star’s brightness had noticeably dropped, especially in its southern region. The brightness returned to normal in April 2020. Credit: ESO/M. Montargès et al.

June 16, 2021 — When Betelgeuse, a bright orange star in the constellation of Orion, became visibly darker in late 2019 and early 2020, the astronomy community was puzzled. A team of astronomers have now published new images of the star’s surface, taken using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), that clearly show how its brightness changed. The new research reveals that the star was partially concealed by a cloud of dust, a discovery that solves the mystery of the “Great Dimming” of Betelgeuse.

Betelgeuse’s dip in brightness — a change noticeable even to the naked eye — led Miguel Montargès and his team to point ESO’s VLT towards the star in late 2019. An image from December 2019, when compared to an earlier image taken in January of the same year, showed that the stellar surface was significantly darker, especially in the southern region. But the astronomers weren’t sure why.

The team continued observing the star during its Great Dimming, capturing two other never-before-seen images in January 2020 and March 2020. By April 2020, the star had returned to its normal brightness.

“For once, we were seeing the appearance of a star changing in real time on a scale of weeks,” says Montargès, from the Observatoire de Paris, France, and KU Leuven, Belgium. The images now published are the only ones we have that show Betelgeuse’s surface changing in brightness over time.

In their new study, published today in Nature, the team revealed that the mysterious dimming was caused by a dusty veil shading the star, which in turn was the result of a drop in temperature on Betelgeuse’s stellar surface.

Betelgeuse’s surface regularly changes as giant bubbles of gas move, shrink and swell within the star. The team concludes that some time before the Great Dimming, the star ejected a large gas bubble that moved away from it. When a patch of the surface cooled down shortly after, that temperature decrease was enough for the gas to condense into solid dust.

“We have directly witnessed the formation of so-called stardust,” says Montargès, whose study provides evidence that dust formation can occur very quickly and close to a star’s surface. “The dust expelled from cool evolved stars, such as the ejection we’ve just witnessed, could go on to become the building blocks of terrestrial planets and life,” adds Emily Cannon, from KU Leuven, who was also involved in the study.

Moons of Jupiter and Saturn at the June meeting

was captured last week by NASA's robotic Juno spacecraft as it passed only about 1,000 kilometers above the immense moon. Credits: NASA/JPL-Caltech/SwRI/MSSS
This image of Ganymede, a moon of Jupiter, was captured last week by NASA’s robotic Juno spacecraft as it passed only about 1000 kilometers above the immense moon. Credits: NASA/JPL-Caltech/SwRI/MSSS

The June 14, 2021 membership meeting of the Cuyahoga Astronomical Association (CAA) will take place via the Zoom online service beginning at 7:30 p.m. Gary Kader, CAA member and director of the Burrell Observatory at Baldwin Wallace University, will present a talk dealing with the satellites of Jupiter and Saturn.

Attendees may join the Zoom meeting beginning at 7:20 p.m. the nights of CAA scheduled meetings, and meetings begin at 7:30.

The evening will begin with introductions and a program by the featured speaker. The talk will be followed by the monthly membership business meeting, typically concluding at about 9 p.m. Guest attendees are welcome.

To attend:

You can either “Phone in” or watch and participate via “Zoom Video”.

Phone In:  Just dial:  1-312-626-6799  (Chicago number)

You will be required to enter our meeting number:  954 8268 6049

Zoom Video with video and audio, on your web browser. (No camera required)
https://zoom.us/j/95482686049

Or download the desktop application from: https://zoom.us/download#client_4meeting

June 10’s sunrise solar eclipse in pictures

Members of the Cuyahoga Astronomical Association (CAA) rose early June 10 to view, photograph, and promote the (locally) partial solar eclipse. Already in progress as Sun rose above the horizon, the annular eclipse or “ring of fire” could not be seen but decent coverage of the solar disk did result in some impressive views.

In addition to watching the eclipse members, led by special events director Jay Reynolds, hosted members of the public at Cleveland’s Edgewater Park. The view from Edgewater’s lakefront location included the rising partly-eclipsed Sun with the lakeshore and Cleveland’s skyline.

Other members took up station at Avon Lake, Bay Village, and even inland at a Medina County location. Here, in mixed order, is a sampling of member photographs:

Eclipse Sunrise by Jeff Lewis
Jeff Lewis, in Bay Village, captured this view of the eclipsed sun as it rose above the Lake Erie horizon.
Dave Nuti Eclipsed Sun and Cleveland skyline
Dave Nuti captured this view of the rising eclipsed Sun and the Cleveland, Ohio skyline as seen from Edgewater Park.
Jay Reynolds -- Early risers viewing sunrise and Cleveland Skyline
Jay Reynolds made this photograph of early risers viewing the eclipse from Edgewater Park with the “photo op” Cleveland sign in the foreground.
CAA member Nora Mishey, CAA’s Education Director, discusses the science of eclipses with members of the public at Edgewater Park in this photo by Anita Kazarian.
A horn of the eclipsed Sun become visible as it rises from the Lake Erie horizon. Viewed from Bay Village.
Eclipsed Sun rising through morning fog in rural Medina County. by James Guilford
James Guilford captured this view from far inland — rural Medina County — where ground fog created interesting lighting effects.
Joe Hamlin, in Avon Lake, produced this colorful capture of the eclipse over Lake Erie.
Photographing the eclipse from Edgewater Park, the photographer was photographed by Anita Kazarian.
Matt Franduto shot this photo of the cloud-obscured eclipse through his telescope.
Jeff Lewis, from Bay Village, shared this view of the rising eclipse as it clears some low clouds.
Eclipsed Sun rising through morning fog in rural Medina County. by James Guilford
Calling this the “cherry bowl”, James Guilford produced this image of the sunrise eclipse as seen through ground fog in rural Medina County.
Rising from a nest of clouds, the red eclipsed Sun was imaged by Timothy Campbell from Edgewater Park.
Chris Elder was in Hampton Beach, New Hampshire, for the eclipse. Patchy clouds blocked the view at dawn, but they broke up about 20 minutes in revealing some of the best eclipse views available in the country.

June 10 brings a solar eclipse — be careful how you view it!

Annular Eclipse of the Sun. Image Attribution: Smrgeog, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons

An annular eclipse of the sun will take place June 10 and it will be underway at sunrise. Unfortunately, even with clear skies we will not see the “ring of fire” that is the namesake look of this type of eclipse. In fact, no place in the United States will see the complete circle, or annulus, of Sun around Moon. So don’t feel left out.

In our area, sunrise will be at 5:55 AM (EDT) with the eclipse already at its maximum for us. The eclipse ends at 6:35 AM as Moon completes its passage across Sun.

A total eclipse of the sun takes place when Earth’s Moon, at normal orbital distances, covers the solar disk completely and blocks all but the glowing corona from view. An annular eclipse takes place when Moon is at higher points in its orbit when it passes between Earth and Sun, too distant and small to form a perfect cover, allowing a brilliant ring of our star to shine.

What we may see at dawn and diminishing thereafter, is a partial solar eclipse — looking a bit like the chomping character from the classic PAC-MAN video game. Much of the solar disk will be visible but the curved edge of Moon will take a bite out of one side.

How can you watch the eclipse? With great care!

Partial Eclipse of the Sun, August 21, 2017 — this image rotated to resemble what viewers might see at dawn, June 10, 2021. Photo by James Guilford

How can you watch the eclipse? With great care! At no time during our partial solar eclipse will it be safe to watch the event without vision protection. If you have eclipse glasses from a recent solar eclipse, those should be just fine — just make sure there are no pinholes or other damage to the plastic film “lenses”! You can check for damage by holding the eclipse viewer at arm’s length and looking at a bright lightbulb. If you see any dots of light through the viewer film, throw those glasses out!

Do NOT look at the sun through sunglasses, even multiple sets of sunglasses, or photo negatives, Compact Discs, or anything other than certified eclipse viewing equipment! Pinhole and other projection techniques can be used safely since the viewer is looking at a projection and not the sun itself. Five Ways to View the Solar Eclipse

“The Sun can be viewed safely with the naked eye only during the few brief seconds or minutes of a total solar eclipse. Partial eclipses, annular eclipses, and the partial phases of total eclipses are never safe to watch without taking special precautions. Even when 99% of the Sun’s surface is obscured during the partial phases of a total eclipse, the remaining photospheric crescent is intensely bright and cannot be viewed safely without eye protection [Chou, 1981; Marsh, 1982]. Do not attempt to observe the partial or annular phases of any eclipse with the naked eye. Failure to use appropriate filtration may result in permanent eye damage or blindness!” — NASA: Eye Safety During Solar Eclipses