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Betelguese loses its luster

This article first appeared in the 2/21/20 edition of the Davis Enterprise.

Betelguese loses its luster

Position of Betelgeuse in the constellation of Orion. Photo courtesy of Hubble European Space Agency. Photo credit is Akira Fujii.

Betelguese loses its luster



by Vinita Domier

Davis Astronomy Club



Betelgeuse has been of immense viewing interest to both professional and amateur astronomers since late 2019 when the supermassive pulsating star was observed to be dimming rapidly. By early 2020, the star had dimmed by 36% of its normal brightness which was noticeable to even a casual observer. As supergiant stars end their lives in a massive explosion or supernova, some astronomers are speculating that this unprecedented dimming might be a sign that Betelguese is nearing the end of its life as a red supergiant.


In the last few months, Betelgeuse has dropped in visual magnitude from an average of +0.4 to plateauing at a historic low of +1.6 in mid-February. This is considerably more than its usual periodic magnitude variation between +0.4 and +0.9 in about 420 - 430 days. Whereas the star is usually bright enough to be at the bottom of the list of top ten brightest stars in the sky, presently it cannot even be included in the top twenty list. Telescopic observations of Betelguese in the same time period have shown a pronounced deformation in its spherical shape.


Betelguese is a mature semi regular variable red supergiant star and is usually the second brightest star in the great Orion Constellation. In contrast, the six other bright stars that depict the central hourglass figure of the constellation are young blue giant or supergiant stars, including the brightest star Rigel. Betelguese is around 700 light years distant from Earth and is about 15 - 20 times more massive and 1400 times larger than the Sun.


Orion, the Hunter, is one of the most recognizable and brightest of the 88 official constellations and is prominent in the southern evening sky from January to March. Comprised of some of the brightest stars in sky that are visible to the naked eye, it is easy to imagine the shape of its namesake Greek mythological hunter with one outstretched arm holding a spear overhead and the other arm holding a shield in front. Bright red Betelguese is visible at the top left of Orion’s torso with bright bluish Rigel diagonally opposite on the bottom right.


A distinguishable feature of the constellation is a close grouping of three relatively bright stars in a slanted line that can be imagined to be Orion’s belt across his midsection along with a vertical line of three dimmer stars depicting his sword. Even with the unaided eye, however, the middle ‘star’ in the sword appears fuzzy rather than a pinpoint of light. Known as the Orion Nebula (also Messier 42 or M42), this region of active star formation is the closest to Earth at 1600 light years distance.


Join the Davis Astronomy Club on Saturday, February 22 starting at 7pm at Explorit Science Center (3141 5th Street, Davis) at the free public meeting for all ages where we will discuss the star Betelguese in particular and the Orion Constellation in general, followed by a star party where we will gaze at the stars of Orion, weather permitting.



Explorit's coming events:


  • Come find Explorit at the following community events: Duck Days Saturday, February 22; Children’s Activity Faire Tuesday, February 25; and Women in STEM-Leap In, at Peregrine School Saturday, February 29.


  • Explorit Summer Camp registration will be open soon!  For information on dates and topics visit our website


  • Become a member of Explorit!  Membership grants you free visits to Explorit’s regular public hours, discounts on events, camps, and workshops, and gives you ASTC benefits.  For more information or to purchase or renew your membership visit or call Explorit at 530-756-0191.


  • Pi Day Celebration! Saturday, March 14 from 10am-5pm.  Admission is $6 for Members/$8 for Non-Members for a day of circle and pi fun! No passes.



  • Extended public hours: 1-5pm every day during the week of April 6-10.  Regular hours resume Saturday, April 11.
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