A hypergiant star’s mysterious dimming | EarthSky.org

Giant red star with huge loops of plasma and dust.

View larger. | Artist’s idea of purple hypergiant star VY Canis Majoris, with its big arcs of plasma (harking back to prominences on our solar). In line with a brand new examine, these huge arcs are thought to contribute to an noticed dimming of this star over the previous a number of centuries. Picture through NASA/ ESA/ R. Humphreys (College of Minnesota)/ J. Olmsted (STScI)/ Hubblesite.

VY Canis Majoris – within the route to our constellation Canis Major the Greater Dog – is likely one of the largest stars recognized. It’s a purple hypergiant, so big that it makes the well-known big star Betelgeuse look small by comparability. In case you changed our solar with VY Canis Majoris, its outer layers would prolong previous the orbit of the fifth , Jupiter. It’s distant at about 3,900 light-years, so it solely appears to be like like a faint star to us (with telescopes) although it’s truly as vibrant as 300,000 suns. Astronomers have questioned about this star, as a result of – like Betelgeuse in late 2019 and early 2020 – it’s recognized to have pale in brightness. VY Canis Majoris, although, has pale very progressively, over the previous couple of centuries. On March 4, 2021, astronomers utilizing the Hubble Area Telescope said they assume they know why. They mentioned this getting old star is belching out big clouds of gases, forming mud that’s progressively blocking increasingly more of its gentle. One of many researchers commented:

VY Canis Majoris is behaving lots like Betelgeuse on steroids.

The researchers published their peer-reviewed findings on February Four in The Astronomical Journal.

The dimming is harking back to Betelgeuse, a purple supergiant star, which instantly and dramatically faded yr, however then totally recovered its former brightness. The dimming led to hypothesis that Betelgeuse may explode quickly in a supernova! After all, Betelgeuse has not exploded. In line with astrophysicist Roberta Humphreys on the College of Minnesota, Minneapolis – who led the brand new examine – the dimming of VY Canis Majoris is probably going just like that of Betelgeuse, however on a a lot bigger scale. The fading durations on VY Canis Majoris are for much longer, and the star dims extra dramatically. The dimming is because of rising quantities of mud being shaped that briefly blocks gentle from the star.

The scientists assume that there are related processes creating the mud round each stars, however that the a lot bigger outflows are forming extra substantial quantities of mud round VY Canis Majoris. Humphreys commented:

This star is totally superb. It’s one of many largest stars that we all know of, a really advanced, purple supergiant. It has had a number of, big eruptions.

Bright nebula of material shown in three zoomed-in panels.

This view “zooms into” VY Canis Majoris, which is surrounded by an immense nebula of fabric expelled from the star. mage through NASA/ ESA/ R. Humphreys (College of Minnesota)/ J. Olmsted (STScI)/ Hubblesite.

Outline of Canis Major constellation with text annotations.

VY Canis Majoris is positioned within the route to our constellation Canis Main the Larger Canine. Sirius, the brightest star in our sky, can be on this constellation. Picture through NASA/ ESA/ J. DePasquale (STScI)/ A. Fujii/ Hubblesite.

So simply how do these stars – Betelgeuse and VY Canis Main – trigger these huge clouds of obscuring mud?

They’re thought to shed a few of their mass by means of big arcs of plasma, extraordinarily scorching gases, just like the solar prominences seen to loop up at instances from our personal solar. The arcs from VY Canis Main – a a lot bigger star than our solar – are additionally a lot, a lot bigger. One other distinction is that the arcs of fabric seem to not be bodily connected to the star. As a substitute, they look like thrown out from the star, after which they drift away from it. Beforehand, Humphreys and  her group had calculated the arcs of fabric had been ejected from the star in periodic episodes from a number of hundred years in the past to inside the previous couple hundred years.

A giant arc extending from the surface of the sun.

Our solar behaves in a method that’s just like VY Canis Majoris, albeit on a smaller scale. Right here’s an eruptive prominence as seen in UV gentle on our solar, on March 30, 2010. Earth is superimposed for a way of scale. Picture through NASA/ SDO.

The brand new Hubble observations present extra buildings, reminiscent of knots of scorching fuel, regarded as lower than 100 years outdated. It turned out that the of the formation of a few of these options coincided with observations from the 19th and 20th centuries that confirmed VY Canis Majoris had dimmed to about one-sixth of its normal brightness.

This is the reason VY Canis Main – as soon as a visual star to the attention – can not be seen with the attention alone. In our time, you want a telescope to look at it.

It’s onerous to fathom simply how immense a purple hypergiant star like VY Canis Majoris is. The plenty of simply among the small knots of fuel on VY Canis Majoris are than twice that of Jupiter. The star itself has a mind-boggling radius 1,420 instances that of our solar. Betelgeuse can be immensely bigger than our solar, but VY Canis Majoris is so big it sheds 100 instances extra mass than Betelgeuse. As Humphreys famous:

It’s superb the star can do it. The origin of those excessive mass-loss episodes in each VY Canis Majoris and Betelgeuse might be brought on by large-scale floor exercise, giant convective like on the solar. However on VY Canis Majoris, the cells could also be as giant as the entire solar or bigger.

That is most likely extra frequent in purple supergiants than scientists thought and VY Canis Majoris is an excessive instance. It could even be the primary mechanism that’s driving the mass loss, which has all the time been a little bit of a thriller for purple supergiants.

Smiling woman with eyeglasses.

The brand new examine was led by astrophysicist Roberta Humphreys on the College of Minnesota. Picture through University of Minnesota.

Big stars like VY Canis Majoris don’t dwell so long as much less large stars like our solar. Our solar is already four-and-a-half billion years outdated and thought of center . VY Canis Majoris is lower than 10 million years outdated and thought of to be in its “outdated age.” The purple hypergiant big part of a star like this one is estimated to final between 100,000 and 500,000 years. VY Canis Main is predicted to blow up as a supernova inside the subsequent 100,000 years. If it does explode, we’d see it brighten significantly although it’s fairly far away from us. Its distance (3,900 light-years) is larger than that of Betelgeuse, which is barely about 640 light-years away.

Whereas scientists usually assume that  VY Canis Majoris will finally explode in a supernova, there’s additionally an opportunity it might flip instantly right into a black hole as a substitute, skipping the supernova stage.

It’ll be attention-grabbing to see how a lot dimmer the star turns into within the years forward!

Large reddish star with rectangular inset showing tiny dot next to it with text annotations.

The dimensions of VY Canis Majoris is really immense, about 1,420 instances bigger (and 300,000 instances brighter) than our solar. Picture through Oona Räisänen/ Wikipedia.

Backside line: Astronomers assume they’ve found out why VY Canis Majoris, one of many largest and brightest stars in our , has been progressively dimming in brightness over the previous couple hundred years.

Source: The Mass-loss History of the Red Hypergiant VY CMa*

Via Hubblesite

Paul Scott Anderson



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