Here's what really happened To Betelgeuse Star.
Besides being the host system of the planet in which Ford Prefect lived, according to
Hitchhiker's Guide to the galaxy, it is the second brightest star in the Orion Constellation,
after Rigel.
It is also the tenth brightest star in the night sky, clearly visible to the naked eye.
Also, together with Sirius and Procyon, it is one of the vertices of the asterism of
the famous “Winter Triangle”.
Can you guess who are we talking about?
Of course, Betelgeuse!
I bet you've heard a lot of people talking about it in the last few months.
In the latest months, astronomers were worried about Betelgeuse's behaviour.
Someone said its destiny was uncertain.
But why?
What actually happened to this beautiful star?
Follow me on this video to get to know more about Betelgeuse!
Betelgeuse is a big big star, belonging to the red supergiant spectral class.
Its distance from the Earth is about 600 light-years away.
And it is always there for us.
If you go out and look for the Orion constellation, you will notice Rigel, and then Betelgeuse:
they're the brightest ones.
We know stars evolve.
For example, we know our Sun was born 4.6 billion years ago, and it is currently a main-sequence
star.
It will remain so for another 4-5 billion years.
Then, it will expand, cool and become a red giant.
After that, it will shrink and heat up again, to become a white dwarf.
The white dwarf will then be destined to cool down over billions of years.
These are what we know about our Sun.
What about Betelgeuse?
Well, we actually know pretty well in which evolutionary phase it is.
It is a quite advanced phase, which shows episodes of variability due to almost regular
pulsations of the star.
Betelgeuse is one of the brightest stars ever, and its mass is about 15 to 20 times that
of the Sun.
Therefore, it is believed that Betelgeuse will end its existence by generating a huge
supernova explosion.
Over a period of time that can range from a few weeks to a few months, a supernova emits
as much energy as the Sun is expected to emit during its entire existence and, for about
fifteen seconds, reaches a temperature of one hundred billion Kelvin.
The explosion expels most or all of the material that makes up the star at speeds
that can reach 30,000 km / s (10% of the speed of light ), producing a shock wave that is
spreads in the interstellar medium.
This results in an expanding gas bubble which is called a supernova remnant.
A supernova is therefore an amazing show to watch.
This is why, in 2019, when Betelgeuse suddenly dimmed for no apparent reason, astronomers
were a little alarmed and triggered at the same time.
Some people speculated that Betelgeuse was about to explode in a supernova so bright
that would outshine the full moon.
Astronomers also know that explosions like those are rare.
They estimate that one occurs in our galaxy just a few times a century.
So, even Betelgeuse was of course a beautiful star, someone would have been happy if Betelgeuse
exploded.
When the star started acting strangely, astronomers aimed every telescope they could at the dimming
supergiant.
Luckily (or not?), after some months the star returned to its usual brightness, and the
excitement over an imminent supernova faded.
A team of astronomers has now released new images of the star's surface that clearly
show how its brightness has changed.
Why was that?
Why Betelgeuse didn't explode?
We now think we have an answer.
In fact, research conducted by VLT (Very Large Telescope) of ESO (the European Southern Observatory)
and published by the prestigious scientific journal Nature, revealed that the decrease
in brightness of the star Betelgeuse was due to a cloud of dust that covered her.
This discovery solves the mystery of the "Great Attenuation" of Betelgeuse.
But what do I mean for cosmic dust?
Cosmic dust also called extraterrestrial dust or space dust is dust that exists in outer
space.
The space that exists between stars is not empty.
It is covered by cosmic dust.
Most dust particles measure between a few molecules and 0.1 mm (100 micrometres).
Larger particles are called meteoroids.
According to its astronomical location, cosmic dust can be divided into intergalactic dust,
interstellar dust, interplanetary dust circumplanetary dust (such as in a planetary ring).
In the Solar System, interplanetary dust causes the so-called zodiacal light.
Cosmic dust contains some complex organic compounds that could be created naturally,
and rapidly, by stars.
A smaller fraction of dust in space is "stardust" consisting of larger refractory minerals that
condensed as matter left by stars.
Now that we talked a little bit about cosmic dust, here's how and what astronomers at ESO
found.
Betelgeuse's decline in brightness led astronomer Miguel Montargès and his team to point ESO's
VLT towards the star at the end of 2019.
The team continued to observe the star during the "Great Attenuation" period, capturing
two more never-before-seen images in January and March 2020.
By April 2020, the star had returned to its normal brightness.
"For once, we have seen the appearance of a star change in real-time on a scale of weeks
- said Montargès - the images now published are the only ones showing the surface of Betelgeuse
changing in brightness over time".
In their new study, the team revealed that the mysterious darkening was caused by a dusty
veil covering the star.
In turn, the veil was the result of a drop in temperature on the star surface of Betelgeuse.
Sometime before the "Great Attenuation," the star had ejected a large gas bubble, which
then receded.
One area of ​​the surface cooled just after that.
And the drop in temperature was enough to condense the gas into solid dust.
Here's what happened and here's where the dark veil comes from.
As you can see, this four-panel graphic illustrates how the southern region of the rapidly evolving,
bright, red supergiant star Betelgeuse may have suddenly become fainter for several months
during late 2019 and early 2020.
In the first two panels, as seen in ultraviolet light with the Hubble Space Telescope, a bright,
hot blob of plasma is ejected from the emergence of a huge convection cell on the star's surface.
In panel three, the outflowing, expelled gas rapidly expands outward.
It cools to form an enormous cloud of obscuring dust grains.
The final panel reveals the huge dust cloud blocking the light (as seen from Earth) from
a quarter of the star's surface.
(CREDITS: NASA)
“The dust ejected from evolved cold stars, such as the one we have just witnessed, could
continue to become one of the building blocks of terrestrial planets and life,” said Emily
Cannon, of KU Leuven, also involved in the study.
This new research finally confirms that Betelgeuse's “Great Attenuation” was not a harbinger
of the star's dramatic final fate, as some of us were thinking.
Anyway, could this event, could this dimming be a precursor sign of a supernova explosion?
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Some astronomers think the sudden dimming may be a pre-supernova event.
The star is relatively nearby, about 725 light-years away, which means the dimming would have happened
around the year 1300.
But its light is just reaching Earth now.
"No one knows what a star does right before it goes supernova because it's never been
observed," Dupree explained.
"Astronomers have sampled stars maybe a year ahead of them going supernova, but not within
days or weeks before it happened.
But the chance of the star going supernova anytime soon is pretty small."
However, we need more observations to be able to say more about it.
Right now, Betelgeuse is in the daytime sky, too close to the Sun for Hubble observations.
But NASA's Solar Terrestrial Relations Observatory (STEREO) has taken images of the monster star
from its location in space.
Those observations show that Betelgeuse dimmed again from mid-May to mid-July, although not
as dramatically as earlier in the year.
Do you want to know which instruments and data did the team use?
Here's some of them.
1) Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE).
It is an instrument installed on ESO's VLT to directly view the Betelgeuse surface.
2) Data from the GRAVITY instrument installed on the VLT Interferometer (VLTI) of the ESO.
They were used to monitor the star during darkening.
3) The telescopes, located at ESO's Paranal Observatory in Chile's Atacama Desert.
They've been of course vital diagnostic tools for uncovering the cause of this attenuation
event.
These telescopes are so powerful that astronomers were able to observe the star, not as a single
point of light, but also to resolve the details of its surface and monitor it during the event.
This discovery is important mainly for two reasons.
The first one is that, as we've already said, stars can act in unpredictable ways.
We were expecting an explosion, but it was not the case.
The second reason resides in the high resolution we can reach with the most powerful instruments
we have.
Studies like this underline the importance for an observatory of having good telescopes
and always keep them updated.
We would end the video with a fun fact about the study team's leading astronomer, Montargès.
People keep asking him if he would like ​Betelgeuse to go supernova so he can study it.
But he loves Betelgeuse.
“I would like another star to go supernova,” he says.
“Antares, I don’t care about it; it can explode anytime.
But not Betelgeuse.”
"This video ends here!
Thanks for watching everyone!
Have you ever seen Betelgeuse in the night sky?
Could you spot it?
Let us know in the comment below!
See you next time on the channel!