The star Betelgeuse appears as a brilliant, ruby-red, twinkling patch of light in the upper right shoulder of the winter constellation of Orion the Hunter . But up close, astronomers know it as a bubbling monster with a heartbeat of days of regular pulsations. This aging star is classed as a supergiant because it has swelled to an astonishing diameter of around 1 billion miles. If placed in the center of our solar system, it would reach the orbit of Jupiter. The star’s ultimate fate is to explode into a supernova. When it does finally happen, it will briefly be seen in the daytime sky from Earth. But there are plenty of fireworks going on before the final detonation.
Astronomers using Hubble and other telescopes have deduced that the star blew up a huge portion of its surface seen in 2019.
This has never been seen before on a star. Our petulant Sun regularly undergoes massive ejections from its outer atmosphere, the corona. But these events are orders of magnitude smaller than what has been seen on Betelgeuse. The first clue came when the star mysteriously darkened at the end 2019. A huge cloud of obscuring dust formed from the ejected surface as it cooled. Astronomers have now pieced together a scenario for the upheaval. And the interior resounds like a bell struck with hammer blows, disturbing the ordinary cycle of the star. That doesn’t mean the monster star is going to explode anytime soon, but the end-of-life convulsions could continue to amaze astronomers.
Analyzing Hubble Space Telescope data from NASA and several other observatories, astronomers have concluded that the bright red supergiant star Betelgeuse literally exploded in 2019, losing a substantial portion of its visible surface and producing a gigantic floor mass ejection (SME). This is something unheard of in standard star behavior.
Our Sun regularly blows out parts of its tenuous outer atmosphere, the corona, during an event known as coronal mass ejection (CME). But the Betelgeuse SME blew up 400 billion times more mass than a typical CME!
Harvard & Smithsonian in Cambridge, Massachusetts.
These new observations provide clues as to how red stars are losing strength. mass late in their lives when their nuclear fusion furnaces burn out, before exploding as a supernova. The amount of mass loss greatly affects their shape. However, Betelgeuse’s surprisingly petulant demeanor isn’t proof that the star is about to explode anytime soon. Thus, the mass loss event is not necessarily the signal of an imminent explosion.
Dupree now brings together all the puzzle pieces of the star’s petulant behavior before, after and during the eruption into a cohesive story of a titanic convulsion never before seen in an aging star.
This includes new spectroscopic and imaging data from the STELLA robotic observatory, the Tillinghast Reflector Echelle (TRES) spectrograph at the Fred L. Whipple Observatory. from NASA’s Hubble Space Telescope and the American Association of Variable Star Observers (AAVSO). Dupree points out that the Hubble data was essential in helping to solve the mystery.
“We have never before seen a huge mass ejection from the surface of a star. We are left with something that we do not fully understand. It is a totally new phenomenon that we can directly observe and solve the details of the area with Hubble. We are observing stellar evolution in real time.”
The titanic explosion of 2019 may have been caused by a a convective plume, over a million miles in diameter, bubbling from deep within the star. Betelgeuse is now struggling to recover from this injury.
Weighing approximately several times more than our Moon. The dimming, which started late 2019 and lasted a few months, was easily noticeable even by backyard observers watching the star change in brightness. One of the brightest stars in the sky, Betelgeuse sits easily on the right shoulder of the constellation Orion.
Even more fantastically, the supergiant’s 400 day pulsation rate is now gone, perhaps at least temporarily. For nearly years, astronomers have measured this rhythm as evidenced by changes in the brightness variants and floor motions of Betelgeuse. Its disruption attests to the ferocity of the eruption.
The star’s inner convection cells, which drive the regular pulsation, can sway like a washing machine tub unbalanced, suggests Dupree. The TRES and Hubble spectra imply that the outer layers may have returned to normal.
Although our Sun has coronal mass ejections which expel small pieces of the outer atmosphere, astronomers have never seen so much of a star’s noticeable surface blasted out into space. Therefore, area mass ejections and coronal mass ejections may be different events.
Betelgeuse is now so huge that if it replaced the Sun at the center of our system solar, its outer surface would extend beyond the orbit of Jupiter. Dupree used Hubble to solve for hotspots in the area of the star at 1996. This was the first direct impression of a star other than the Sun.
NASA’s Webb Space Telescope may be able to detect the ejected material in the light infrared as it continues to move away from the star.