- 4085 - BETELGUESE - brightest ready to explode? One of the brightest stars in the night sky might die in a spectacular explosion within our lifetime. The conjecture is that the red giant star Betelgeuse, the left shoulder of the constellation Orion also known as Alpha Orionis, may have less than three hundred years' worth of fuel left in its core.
--------------------- 4085 - BETELGUESE - brightest ready to explode?
- When the star
burns through those last drops, its core will collapse into a black hole and in
the process blast out the star's outer layers at enormous speeds of up to
25,000 miles per second. This fiery demise is a “supernova explosion”, and in
the case of Betelgeuse, it will be a spectacular sight for observers on Earth.
Since the star is only 650 light-years from Earth, those layers of gas and dust
will shine as bright as the full moon in our sky for several weeks.
-
- The problem is
that most astronomers don't think that Betelgeuse is ready to go bang just yet.
So what makes the researchers behind the new paper think otherwise?Betelgeuse
is undoubtedly a red giant star that has already burned through its primary
fuel hydrogen and is now fusing helium in its core into heavier elements. The
point at which a star runs out of hydrogen in its lifetime is unmissable.
-
- Stars short on
hydrogen need to put extra energy into igniting the helium produced during the
fusion of hydrogen, which forces them to expand dozens of times beyond their
original size. In the process, they also become cooler and redder.
-
- Astronomers know
that Betelgeuse is huge. If it were to sit at the center of our solar system,
the scorching gas in its outer atmosphere would reach far enough to engulf even
the planet Jupiter.
-
- However, the exact
width of Betelgeuse is hard to measure.
That's because instead of being one rather smooth ball of plasma, Betelgeuse is
a lumpy clump of boiling gas bubbles shrouded in burped out dust clouds. To
measure its diameter is therefore not easy, yet, the case for determining
Betelgeuse's remaining lifetime rests on the star's size.
-
- Betelgeuse is
larger than what most researchers believe. This could be possible as Betelgeuse
is known to pulsate, expand and shrink, dim and brighten up, at regular
intervals. Most obviously, Betelgeuse's brightness swings up and down every 420
days. Astronomers attribute this brightening to the periodical expansion of the
star's envelope, or roughly spherical outer region, in a phenomenon known as
the fundamental mode.
-
- There are other
quirks in Betelgeuse's behavior, also appearing on a regular basis, which
astronomers attribute to additional turbulent processes taking place inside the
dying star. One of those additional variations takes place on a 2,200-day
cycle, and astronomers have no explanation for it. A proposal is that this 2,200-day oscillation
could, in fact, represent Betelgeuse's main pulsation mode while the 420-day
brightness variation could be a secondary quirk.
-
- Such a scenario,
however, requires Betelgeuse to be up to one third wider for these models of
its evolution to work. To explain the
2,200-day period as fundamental mode requires a much larger radius than the
case of fitting the 420-day period with fundamental mode. A larger radius with a range of observed
surface temperature means the intrinsic brightness of Betelgeuse to be higher
than previously thought.
-
- But for Betelgeuse
to be as wide as the models require, it would also have to be in a later stage
of its life, already done burning helium and instead running on carbon, which
arose from the previous fusion of helium atoms. Whether a red giant star is
burning helium or carbon makes a big difference in terms of how much life it has
left.
-
- The helium-burning
phase of a red giant star's life lasts tens of thousands of years. When
carbon-burning switches on, the end might come within a few thousand years.
-
- Although we cannot
determine exactly how much carbon remains right now, our evolution models
suggest that the carbon exhaustion would occur in less than 300 years. After the carbon exhaustion, fusions of
further heavier elements would occur in probably a few tens of years, and after
that the central part would collapse and a supernova explosion would occur.
-
- The last time a
nearby star went supernova was in 1604. Although stars explode somewhere in the
universe on a daily basis, most of them are too far away to be visible without
powerful telescopes.
-
- If we look at the
sun, we see a well-defined surface with a very crisp edge. But Betelgeuse being a red supergiant, is
extremely fluffy and puffy, and the photosphere, what we would call its
'surface,' is hidden beneath multiple layers of molecular gas and clouds of
dust.
-
- Violent expulsions
of these materials are typical for red giant stars. In the case of Betelgeuse,
astronomers observed one such massive cloud emerge from within the star in
2019, causing the star to temporarily dim.
-
- The unusual brightening of Betelgeuse that led
some enthusiasts to speculate that the star might be about to explode. But
Betelgeuse is actually too bright to be in its death throes due to the fact
that expulsions of material typically make older red giants gradually dim.
Betelgeuse, on the contrary, despite its regular pulsations, has been a fixture
in the top ten brightest stars of our sky for at least the past 100 years.
-
-
July 10, 2023 BETELGUESE
- brightest ready to explode? 4085
------------------------------------------------------------------------------------------
-------- Comments
appreciated and Pass it on to whomever is interested. ---
--- Some reviews are
at: -------------- http://jdetrick.blogspot.com -----
-- email feedback,
corrections, request for copies or Index of all reviews
--- to: ------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
--------------------- ---
Tuesday, July 11, 2023 ---------------------------------
No comments:
Post a Comment