- 4273 - EXTREME STARS - simulated in the laboratory. Scientists study violent 'superflares' on stars thousands of times brighter than the sun. By applying what we've learned about the sun to other, cooler stars, we were able to identify the physics driving these flares, even though we could never see them directly.
--------------
4273 - EXTREME
STARS - simulated in the laboratory.
-
- Scientists may
have solved the physics behind massive and violent "superflares" that
rip free from stars thousands of times as bright as the sun. Our host star regularly erupts with solar
flares that can impact Earth and, if strong enough, disrupt communications and
power infrastructure on a global scale.
-
- These solar flares
are small compared to the thousands of "superflares" that “Transiting
Exoplanet Survey Satellite” (TESS) and the Kepler space telescopes have seen
blasting from stars between 100 and 10,000 times brighter than the sun.
-
- Superflaring stars
have stronger magnetic fields than the sun, leading to brighter flares, and
these stars also seem to display an initial, short-lived boost in brightness
enhancement, followed by a secondary, longer-lasting but less intense flare.
-
- The superflares of
bright, distant stars and the solar flares of the sun are believed to share the
same underlying physical mechanisms, emerging from the sudden release of
magnetic energy.
-
- By applying what
we've learned about the sun to other, cooler stars, we were able to identify
the physics driving these flares, even though we could never see them
directly. The changing brightness of
these stars over time actually helped us 'see' these flares that are really far
too small to observe directly.
-
- Scientists have
theorized that coronal loops, which are massive hoops of plasma that follow the
trajectory of magnetic field lines seen on the sun, may be present in
superflares as well. If they exist, however, these loops would need to be
incredibly dense on the superflaring stars; as of yet, astrophysicists have
been unable to test this idea. From our vantage point on Earth, we can only
witness coronal loops on the sun.
-
- But another
feature could hint at the presence of these distant stars' coronal loops.
Kepler and TESS have spotted some stars with a peculiar
"bump" in associated light curves. This "peak bump," as
it's called, seems to represent a jump in brightness and result in a light
curve that resembles a phenomenon seen on the sun when an initial burst of light is followed by a
second, more gradual peaking of the light, a phenomenon called "solar
late-phase flares."
-
- Cold this
brightness in visible light on distant stars be caused by massive stellar loops
like the sun's coronal loops cause our star to vary in brightness? Computer simulations of fluids were used
that mimicked coronal loops, periodically upping the length of the loops and
increasing the magnetic energy behind.
-
- They found that
large flare energies would pump more mass into these loops on brighter stars,
increasing their density. This would allow dense stellar loops to contribute to
visible light emissions. And, the scientists concluded, with a longer
evolutionary timescale, the loops would surely produce a distinct, secondary
emission peak just as seen in light
curves collected by TESS and Kepler.
-
- They further found
that the late time "bump" flaring of light seen in the light spectrum
of distant, flaring stars would be the result of super-hot plasma at the
highest points of associated coronal loops on the stars cooling down, then
falling back to the star as glowing material. In turn, that whole process would
lead to the atmosphere heating up.
This finding supports the model because it is analogous to
the coronal rains seen falling from coronal loops that cause the sun's own
atmosphere to heat up.
-
- This research
establishes a strong link between quantum mechanics and astrophysics and
provides a new perspective on the inner nature of neutron stars. They may finally understand the dynamics of
neutron star "glitches" that occur when these ultradense dead stars
suddenly speed up their spins. It would appear that the strange behavior may be
caused when tiny vortices of swirling inner material "break the surface"
of these intense stellar corpses.
-
- A better
understanding of the neutron star glitches could reveal more about their inner
composition and movements, thus giving scientists a window into an object
that's made of arguably the universe's most unique and strange form of matter.
Neutron stars, in essence, are made almost exclusively of neutrons, which is
why they're so utterly dense.
-
- There is a strong
link between quantum mechanics and astrophysics and provides a new perspective
on the inner nature of neutron stars.
Neutron stars are formed when massive stars "die" and their
stellar cores, with masses between one and two times that of the sun, collapse
to the width of just 12 miles.
-
- That's a huge
reduction in size. The neutron-rich matter that comprises neutron stars is so
dense that a mere sugar cube of it would weigh about 1 billion tons on
Earth. That extreme weight, along with
the immense distance to these stellar corpses, means we can hardly bring
neutron star samples down to Earth to study.
-
- However, the study
of neutron stars is brought "down to Earth" by numerically simulating
a neutron star using a proxy in the form of “ultracold dipolar atoms” , an
exotic phase of magnetic gases with a negatively charged atom coupled to a
positively charged atom over long distances.
-
- The glitching of
neutron stars may suggest that the matter beneath these objects' surfaces
exists in the form of a superfluid, a substance that resembles a liquid but has
zero viscosity . Viscosity is a measure
of the resistance a fluid has to changes in shape or to flowing around.
-
- High-viscosity
fluids, such as honey or cold maple syrup, flow slowly and can even act like
solids. Think, stiff peanut butter or even glass. Low-viscosity fluids, on the
other hand, flow more rapidly. But zero-viscosity superfluids are another
story. They rotate in the form of numerous tiny swirling vortices, all of which
carry a little bit of the system's angular momentum.
-
- A key factor in
this behavior and thus a vital element of neutron star glitching would be a
state that shows both crystalline and superfluid properties , a "supersolid." If neutron stars demonstrate this behavior
as they rotate, often as fast as hundreds of times per second, glitches would
occur as vortices break out of the star’s inner crust , the superfluid , to
its solid crystalline outer crust. Those flyaway vortices would carry with them
angular momentum that boosts the rotational speed of the star's outer layer.
-
- This supersolid
phase has been induced in ultracold dipolar atoms of Erbium (Er) and Dysprosium
(Dy). They found that glitches can
indeed occur in ultracold supersolids, which are analogous to larger, more
extreme glitching demonstrated by neutron stars. These results suggest that it
is truly superfluid vortices carrying angular momentum to the surface of these
stars that make them appear to glitch.
-
- This research
shows a new approach to gain insights into the behavior of neutron stars and
opens new avenues for the quantum simulation of stellar objects.
-
-
December 15, 2023
EXTREME STARS
- in the laboratory. 4273
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Monday, December 18, 2023 ---------------------------------
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