- 4258 - INTERIOR OF STARS? - New simulation reveals the churning interiors of giant stars. On a basic level, a star is pretty simple. Gravity squeezes the star trying to collapse it, which causes the inner core to get extremely hot and dense. This triggers nuclear fusion, and the heat and pressure from that pushes back against gravity. The two forces balance each other while a star is in its main sequence state.
-------------------------- 4258 - INTERIOR OF STARS
- The details of how
that works are extremely complex. Modeling the interior of a star accurately
requires sophisticated computer models, and even then it can be difficult to
match a model to what we see on the surface of a star. Now a new computer
simulation is helping to change that.
-
- Although the
internal pressure and gravitational weight of a star are generally in
equilibrium, the flow of heat is not. All the heat and energy generated in a
stellar core has to escape in time, and there are two general ways in which it
happens. The first is through a radiative exchange.
-
- High-energy gamma
rays scatter against nuclei in the core, gradually losing some energy as they
migrate to the surface and escape. The interior of a star is so dense that this
can take thousands of years.
-
- The second method
is through convective flow. Hot material near the center of a star tries to
expand, pushing its way toward the surface. Meanwhile, cooler material near the
surface condenses and sinks towards the core. Together this creates a cyclic
flow of material that transfers heat energy to the star’s surface. This
convection churns the interior of a star, and because of things such as
viscosity and turbulent vortices, it is extremely difficult to model.
-
- Stars generally
have a radiative zone and a convective zone. The location and size of these
zones depend on a star’s mass. Small stars are almost entirely convective,
while stars like the Sun have an inner radiative zone and an outer convective
zone.
-
- For massive
stars, this is flipped, with an inner convective zone and an outer radiative
one. One of the things we know about convection is that it can cause the
surface of a star to fluctuate like a simmering pot of water. This in turn
causes the overall brightness of a star to flicker slightly.
-
- Convection regions
in a star are connected to the way in which a star flickers. Sound waves rippling through a star are
affected by convective flows, which in turn change the way a star flickers.
This means in principle we can study the interior of a star by observing its
flicker of light, allowing astronomers to better understand stars.
-
- Right now the
flickers are too small for current telescopes to observe. But with larger and
more sensitive telescopes we should be able to study them. We are already able
to study the effects of sound waves in the Sun, through what is known as
helioseismology. In the coming decades, we should be able to do this with
nearby stars.
-
-
December 7, 2023
INTERIOR OF
STARS
4258
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Thursday, December 7, 2023 ---------------------------------
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