Spacecraft Enters the Sun's Corona for the First Time in History
From: Center for Astrophysics (Harvard and
Smithsonian)
December
14, 2021 -- Cambridge, MA -- A spacecraft launched by NASA has done
what was once thought impossible. On April 28, the Parker Solar Probe
successfully entered the corona of the Sun — an extreme environment that’s
roughly 2 million degrees Fahrenheit.
The historic moment was achieved thanks
to a large collaboration of scientists and engineers, including members of the Center for
Astrophysics | Harvard & Smithsonian (CfA)
who built and monitor a key instrument onboard the probe: the Solar Probe Cup.
The cup collects particles from the Sun's atmosphere that helped scientists
verify that the spacecraft had indeed crossed into the corona.
"The goal of this entire mission is
to learn how the Sun works. We can accomplish this by flying into the solar
atmosphere," says Michael
Stevens, an astrophysicist at the CfA who helps
monitor the cup. "The only way to do that is for the spacecraft to cross
the outer boundary, which scientists call the Alfvén point. So, a basic part of
this mission is to be able to measure whether or not we crossed this critical
point."
The corona is the outermost layer of the
Sun's atmosphere where strong magnetic fields bind plasma and prevent turbulent
solar winds from escape. The Alfvén point is when solar winds exceed a critical
speed and can break free of the corona and the Sun's magnetic fields. Prior to
April 28, the spacecraft had been flying just beyond this point.
"If you look at close-up pictures
of the Sun, sometimes you'll see these bright loops or hairs that seem to break
free from the Sun but then reconnect with it," Stevens explains.
"That's the region we've flown into — an area where the plasma, atmosphere
and wind are magnetically stuck and interacting with the Sun."
According to data collected by the cup,
the spacecraft entered the corona three times on April 28, at one point for up
to five hours. A scientific paper describing the
milestone has been accepted for publication in
the Physical Review Letters.
CfA astrophysicist Anthony
Case, the instrument scientist for the Solar
Probe Cup, says the instrument itself is an incredible feat of engineering.
"The amount of light hitting the
Parker Solar Probe determines how hot the spacecraft will get," Case
explains. "While much of the probe is protected by a heat shield, our cup
is one of only two instruments that stick out and have no protection. It's
directly exposed to the sunlight and operating at a very high temperature while
it's making these measurements; it's literally red-hot, with parts of the
instrument at more than 1,800 degrees Fahrenheit [1,000 degrees Celsius], and
glowing red-orange."
To avoid degradation, the device is
constructed of materials that have high melting points, like tungsten, niobium,
molybdenum and sapphire.
But the success of the Parker Solar
Probe represents much more than technological innovation. There are many
mysteries about Earth’s closest star that scientists are hoping the probe can
help solve.
For example, "We don't actually
know why the outer atmosphere of the Sun is so much hotter than the Sun
itself," Stevens says. "The Sun is 10,000 degrees Fahrenheit [5,500
degrees Celsius], but its atmosphere is about 3.6 million degrees Fahrenheit [2
million degrees Celsius]."
He adds, "We know that the energy
comes from the churning magnetic fields bubbling up through the surface of the
sun, but we do not know how the Sun's atmosphere absorbs this energy."
In addition, outbursts from the Sun,
like solar flares and high-speed solar winds, can have a direct impact on
Earth, disrupting power grids and radio communication.
The Parker Solar Probe can help better
understand all these phenomena as it continues to orbit the Sun and take
measurements and data for scientists to analyze here on Earth.
Case says, "The plasma around the
Sun can act as a laboratory that teaches us about processes taking place in almost
every astronomical object across the entire universe."
https://cfa.harvard.edu/news/spacecraft-enters-suns-corona-first-time-history
No comments:
Post a Comment