- 4419 - SOLAR ECLIPSE – 2024 , much more to learn? Although Earth-based telescopes can provide images of the sun in a higher resolution, these telescopes can't study the extreme ultraviolet part of the solar light spectrum. Because these frequencies are filtered out by Earth's atmosphere, ground-based telescopes therefore don't see many of the key phenomena driving the sun's behavior.
------------------------- 4419 - SOLAR ECLIPSE – 2024 , much more to learn?
- There is a gap in our observations of the
sun. Part of its atmosphere is effectively invisible to our telescopes.
However, images taken from Earth during a solar eclipse are filling in that
hole, providing an unprecedented look at our star's hidden layer.
-
- On eclipse day, 66 cameras fitted with
special filters and distributed across three observing locations in
Mexico, April 6, 2024, and the U.S. will
capture tens of thousands of images during the roughly four-minute eclipse.
-
- Made of extremely thin, charged gas called
plasma, the solar corona is the upper part of the sun's atmosphere. It is a
million times dimmer than the underlying photosphere that makes up the sun's
visible surface, so it is completely outshined by the light of the star when
viewed in visible light.
-
- To observe the corona, astronomers need to
obscure the visible solar disk to allow the faint coronal light to appear
against the dark cosmos. To do this, they use an instrument called a
coronagraph, which is equipped with an occulter that blocks the sun's light.
-
- However, if the occulter were to cover only
the visible sun, the diffraction, the bending of light around an obstacle,
would let the bright light of the photosphere spill around the occulter's edges
and ruin the photographs. Therefore, astronomers use bigger occulters that also
cover the inner corona up to the distance of one solar radius from the sun's
surface.
-
- The moon, however, being far away, causes
no diffraction while being just the right size to perfectly cover the solar
disk during a total eclipse. If you
take images from space telescopes such as the Solar Dynamics Observatory, you
can see the sun's surface in extreme ultraviolet light.
-
- The corona is the source of the solar wind,
the constant stream of charged particles that expands across the solar system.
Occasionally, it erupts with massive outbursts known as “coronal mass
ejections”, which can cause dramatic geomagnetic storms on Earth. Many of the
processes that accelerate this solar wind into space happen in the
coronagraph's blind spot: The sun itself.
-
- The coronal gas, made mostly of ionized
hydrogen and helium, with a smattering of heavier elements, such as iron,
magnesium, silicon or calcium, loops around the sun's magnetic-field lines. Elsewhere,
it streams into space from large sunspots or active regions and flows from
coronal holes where the magnetic-field lines are broken.
-
- In addition to capturing the white light
of the corona, the researchers can now visualize spectral lines of various
energetic ions present in the coronal gas. This opens the door for more
exciting science. Different types of
ions emerge at different temperatures, so by imaging spectral lines of
different types of ions, we can measure the temperature in different parts of
the corona.
-
- Newly discovered fast magnetic waves might
explain why the sun's corona is so hot. Scientists may have just found what
makes the sun's outer atmosphere, the corona, so inexplicably hot.
-
- For decades, scientists have been struggling
to explain why temperatures in the sun's outer atmosphere, the corona, reach
mind-boggling temperatures of over 1.8 million degrees Fahrenheit. The sun's
surface has only about 10,000 degrees F, and with the corona farther away from
the source of the heat inside the star, the outer atmosphere should, in fact,
be cooler.
-
- Using images taken by the “Extreme
Ultraviolet Imager” (EUI), a camera that detects the high-energy extreme
ultraviolet light emitted by the sun, scientists have discovered small-scale
fast-moving magnetic waves that whirl on the sun's surface. These
fast-oscillating waves produce so much energy, according to latest
calculations, that they could explain the coronal heating.
-
- Scientists have previously detected slower
magnetic waves, but those didn't seem to produce enough energy to explain the
enormous temperature difference between the sun's surface and the outer
atmosphere.
-
- Over the past 80 years, astrophysicists
have tried to solve this problem and now more and more evidence is emerging
that the corona can be heated by magnetic waves. Solar Orbiter, launched in February 2020,
takes the closest images of the star at the center of our solar system.
-
- Solar Orbiter, which makes regular
approaches to less than 48 million miles from the sun (closer than the orbit of
the solar system's innermost planet Mercury), doesn't have those issues. In its first images of the sun alone,
released in June 2020, Solar Orbiter found other indications of processes that
might play a role in the coronal heating mystery.
-
-
April 4, 2023 SOLAR
ECLIPSE – 2024 , much more to learn? 4419
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--------------------- --- Friday, April 5, 2024
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