- \n
- Betelgeuse might not be one star, but two!<\/strong> The smaller star could be 1.7 times the mass of our sun.<\/li>\n
- Betelgeuse underwent a \u201cgreat dimming\u201d<\/strong> in recent years, causing some astronomers to think it might be on the verge of exploding as a supernova. But now a team of astronomers thinks the smaller star plays a role in Betelgeuse\u2019s variability.<\/li>\n
- If Betelgeuse has a companion,<\/strong> it might mean this star \u2013 the nearest red supergiant to Earth at 427 light-years \u2013 won\u2019t go supernova for a long time.<\/li>\n<\/ul>\n
Betelgeuse might have a buddy<\/h3>\n
A close analysis of the light curve \u2013 the record of starlight waxing and waning \u2013 for the old red supergiant star Betelgeuse has revealed the possibility of a 2nd star in the system. In other words, the single point of light we see as Betelgeuse might be 2 stars, with the smaller one about 1.7 times the mass of our sun. If this is so \u2026 is the explosion of Betelgeuse as a supernova still about to happen?<\/p>\n
Betelgeuse is a variable star. It periodically changes in brightness and sometimes has irregular light changes. In recent years, it has undergone periods of dimming, which have caused astronomers to speculate that Betelgeuese \u2013 which is the nearest red supergiant to Earth at 427 light-years away \u2013 might be on the verge of going supernova. <\/p>\n
Prior to the Great Dimming of Betelgeuse in 2019, astronomers said that, yes, Betelgeuse was due to explode, but perhaps not for thousands of years.<\/p>\n
![\"Star](\"https:\/\/earthsky.org\/upl\/2023\/12\/betelgeuse-rigel-orion-1600-e1704024915414.jpg\")
Here\u2019s the famous constellation Orion the Hunter in the night sky. You\u2019ll find it high in the east on September mornings. It\u2019s easily recognizable for its 3 Belt stars, 3 medium-bright stars in a short, straight row. Betelgeuse is one of Orion\u2019s 2 brightest stars. It is distinctly red in color and shines with a somber light.<\/figcaption><\/figure>\n The out-of-sync variation of Betelgeuse<\/h3>\n
A trio of astronomers investigated a 2,170-day cycle of dimming and brightening of Betelgeuse. These scientists describe a long secondary period of variation, which isn\u2019t unusual for stars of Betelgeuse\u2019s class. However, the most common explanation for long secondary periods tends to be that the stars are in binary systems. And, they say, this explanation is specifically likely at Betelgeuse.<\/p>\n
Variable stars like Betelgeuse pulse<\/em>. They literally grow larger and smaller over time. We can study the variability of Betelgeuse in part via a a technique called radial velocity, the movement of something in space (in this case, the movement of the outer surface of Betelgeuse) toward or away from us. But, at Betelgeuse, the radial velocity variation doesn\u2019t line up with the star\u2019s light curve, the measurement of its waxing and waning in brightness. It\u2019s like someone clapping on exactly the wrong beat.<\/p>\n
Authors of the paper \u2013 astronomers Jared A. Goldberg, Meridith Joyce and L\u00e1szl\u00f3 Moln\u00e1r \u2013 claim this out-of-syncness is a smoking gun. Betelgeuse, they said, isn\u2019t alone:<\/p>\n
\n
The light curve-radial velocity phase difference requires a companion to be behind<\/em> Betelgeuse<\/strong> at the long secondary period luminosity minimum \u2026<\/p>\n<\/blockquote>\n
In other words, they said, Betelgeuse is brightest when the red supergiant star and its hypothetical little buddy are shining together, as seen from our earthly perspective.<\/p>\n
This new work resulted in a study that was submitted August 17, 2024, to the online scholarly archive arXiv. <\/p>\n
![\"Graphics:](\"https:\/\/earthsky.org\/upl\/2024\/09\/Betelgeuse-Binary-Motion-800x709.png\")
This schematic shows the dust modulation by a companion star of Betelgeuse over the course of one orbit. The diagram in the center shows 4 orientations of the companion (black circle) as well as Betelgeuse (solid red blob) and some circumstellar gas and dust (curly lines). The arrows represent the motion of the 2 objects. Read more about this image via arXiv.<\/figcaption><\/figure>\n The Great Dimming and its aftermath<\/h3>\n
Back in 2019, Betelgeuse\u2019s brightness dropped dramatically and unexpectedly. The turning down of the lights lasted until 2020. Later, that time of dimming for Betelgeuse became known as the Great Dimming. There was much speculation that Betelgeuse might be about to explode! But it didn\u2019t explode, and, later, dust was offered as an explanation for the dimming.<\/p>\n
Yet the Great Dimming trigged a wave of interest in Betelgeuse. It caught people\u2019s imaginations: would we see this familiar red star blaze forth in brightness, becoming the brightest star in our night sky, perhaps even visible in the daytime?<\/p>\n
That\u2019s why the authors of the new paper describe their results about Betelgeuse as groundbreaking<\/em>:<\/p>\n
\n
These studies have led to revisions in our understanding of Betelgeuse\u2019s behavior and fundamental parameters, as well as opened new lines of inquiry into some of Betelgeuse\u2019s less well-understood properties \u2026<\/p>\n<\/blockquote>\n
So is<\/em> Betelgeuse a binary? The notion Betelgeuse is a binary star dates back at least 25 years. But observations and interpretations since the Great Dimming dust storm strongly reinforce the idea. And the authors say dust is important to understanding what\u2019s going on:<\/p>\n
\n
While such early versions of the binarity hypothesis were most concerned with whether a close companion could induce low-frequency modes on the primary star, the current leading theory is that the timescale of the LSP period is set by the orbital time of a low-mass companion, and the mechanism of dimming and brightening involves the formation and removal of dust along the line of sight in phase with the companion\u2019s orbit.<\/p>\n<\/blockquote>\n
Supernova soon? Not if it\u2019s a binary star<\/h3>\n
Knowing if another, smaller star lurks off the shoulder of Orion may tell us how long Betelgeuse has to live. Betelgeuse is still expected one day \u2013 maybe soon, maybe in thousands of years \u2013 to explode as a supernova.<\/p>\n
When it blows depends on whether a companion star is making it move.<\/p>\n
Betelgeuse has another well-known periodicity in its orbit. This one fluctuates on a cycle of about 420 days, and is believed to be the star\u2019s fundamental mode. If it isn\u2019t, Betelgeuse will go supernova sooner than later.<\/p>\n
The paper explains:<\/p>\n
\n
If the 2,100-day periodicity is the fundamental mode, it implies a large and observationally contentious radius for Betelgeuse. Further, it would place Betelgeuse\u2019s current evolutionary stage beyond the onset of core carbon burning, suggesting that a supernova explosion is imminent within the next several dozen to several hundred years. If, on the other hand, the 2,100-day periodicity is an LSP, Betelgeuse is comfortably within in its core helium burning phase and not due for an explosion for hundreds of thousands of years.<\/p>\n<\/blockquote>\n
This means things don\u2019t look good for those hoping to see a nearby supernova in their lifetimes. The trio of authors say their data means Betelgeuse probably isn\u2019t alone:<\/p>\n
\n
We overview all of the scenarios proposed as an explanation for Betelgeuse\u2019s LSP, demonstrating critical flaws in all but one case: Betelgeuse has a companion that interacts with the star\u2019s dusty circumstellar environment.<\/p>\n<\/blockquote>\n
Not in our lifetime<\/h3>\n
When Betelgeuse finally blows, it\u2019ll probably be visible in the daytime. But that might not be for at least hundreds of thousands of years, according to the ideas presented in this new research.<\/p>\n
![\"Billowing](\"https:\/\/earthsky.org\/upl\/2022\/10\/Betelgeuse-supernova-artist-impression-Royal-astronomical-society-CC4.0-e1665666748293.jpg\")
No supernova in the offing? Artist\u2019s concept of the old red supergiant star Betelgeuse as a supernova, or exploding star. Stars like Betelgeuse are thought to\u00a0dim dramatically before they explode. But if a component of Betelgeuse\u2019s variability is caused by a companion star, its supernova explosion may be far in the future. Image via Royal Astronomical Society\/ ESO\/ L. Cal\u00e7ada (CC BY 4.0).<\/figcaption><\/figure>\n Bottom line: A recently published study suggests the red giant star Betelgeuse might have a sun-size companion. Betelgeuse\u2019s buddy would explain some of the intricacies in astronomers\u2019 measurements of the star\u2019s brightness and variability.<\/p>\n
Read more: Betelgeuse: The Great Dimming of 2019-2020<\/p>\n
Source: A Buddy for Betelgeuse: Binarity as the Origin of the Long Secondary Period in b Orionis<\/p>\n
<\/div>\n
\n - Betelgeuse underwent a \u201cgreat dimming\u201d<\/strong> in recent years, causing some astronomers to think it might be on the verge of exploding as a supernova. But now a team of astronomers thinks the smaller star plays a role in Betelgeuse\u2019s variability.<\/li>\n