Whether it is the mythical and legendary Kwapa Day by Day, the Post-Eclipse Sun, or the various telescopes and detectors aimed at the Sun since modern times, it may mean that from ancient times to the present, human interest in the Sun has never faded.
Recently, Thomas Zurbuchen, deputy director of NASA's Science Mission Board, announced that "the Parker Solar Probe successfully crossed the solar corona on April 28 this year, becoming the first spacecraft in human history to 'touch' the sun".[1]
GIF | Parker probe "touching" the sun (Source: screenshot of related video)
Launched in 2018, the probe aims to observe the sun's interior and reveal the solar mechanism, providing evidence to solve some of the long-standing problems in the astronomical community.
Published Dec. 14 in Physiological Review Letters, the paper titled "Parker Solar Probe Enters the Magnetically Dominated Solar Corona." The first author is Justin C. Kasper, a professor at the Michigan Institute of Astrophysics and deputy chief technology officer at BWX Technologies.
Figure | Related papers (Source: Physical Review Letters)
The pace of humanity "day by day" has never stopped
Human beings cannot do without sunlight, just as they cannot do without air and water. Like the silent spring rain, the sun's rays play a vital role in maintaining the earth's circular operation.
In ancient times, the sun was once mythologically adult, and it is recorded in the Huainanzi Astronomical Training: "The sun comes out of the Yang Valley, bathes in the salty pond, and blows on the Fusang, which is called morning light." ”
In modern times, with the progress of scientific civilization, we finally know that the sun is actually just an ordinary star in many galaxies in the Milky Way, and the so-called sun luminescence is only its internal nuclear fusion reaction. However, human curiosity about the sun has not been satisfied, but more and more want to explore its true face hidden under the "mask of heat".
Figure | Images of the corona during a total solar eclipse (Source: NASA)
In the 1990s, the United States launched the Ulysses solar probe for a closer look at Earth's poles. After a long flight of 17 years, it finally ended its mission perfectly in 2008;
In 2001, the Origin probe was successfully launched. It is worth mentioning that the detector successfully collected samples of solar wind particles through a collection device;
In 2003, the "Evolution of Galaxies" probe was successfully launched, which was the first ultraviolet measurement of space outside the Milky Way, which supported the evolutionary research of many galaxies, including the solar system;
On August 12, 2018, the protagonist of the report, the Parker Solar Probe, was launched at the Kennedy Space Center. Unlike previous spacecraft, NASA has high hopes for it, believing that "this will be the first time that a human probe has come into such close contact with the sun that it will fly directly into the orbit of the corona in the outer atmosphere of the sun, just 6.5 million kilometers from the surface of the sun."
Figure | Parker Solar Probe (Source: NASA)
It's important to note that the concept of sending a spacecraft into the solar magnetized atmosphere even predates NASA's inception.
It is reported that the Parker probe is currently the fastest known human spacecraft, with a speed of almost 400,000 kilometers per hour.
In addition, it takes its name from the American astronomer Eugene Parker in recognition of his outstanding contributions to solar wind research.
The probe entered the solar corona for the first time
Although the announcement date is December 14, the actual time parker probe arrived at the solar corona was April 28 and stayed for five hours.
The parker's main goal is to understand how the sun works, but that requires it to travel through the solar atmosphere and collect solar particles.
The corona is the outermost layer of the Sun's atmosphere, reaching temperatures of 2 million degrees Celsius, while the temperature inside the Sun is only about 5500 degrees Celsius. How to make the spacecraft withstand the erosion of high temperatures across the outer boundary of the sun has thus become the key.
To solve this dilemma, the research team at the Harvard-Smithsonian Center for Astrophysics (CfA) designed a cup-like detection instrument made of materials with high melting points such as tungsten, niobium, molybdenum and sapphire that will not melt even when crossing the corona.
CfA astrophysicist Anthony W. Case said, "The amount of light that hit the Parker Solar Probe determines the temperature of the spacecraft." While most of the probe is protected by a heat shield, our cup is one of only two instruments that stand out and are not protected. ”
In Case's view, the solar probe cup is an engineering feat in itself.
He further explains, "When taking measurements, the cup is directly exposed to sunlight and runs at very high temperatures; it is actually hot, part of the instrument is over 1000 degrees Celsius and emits a reddish-orange light. ”
The end result is that the Solar Probe Cup successfully completed the collection of solar particles, which will help scientists understand the latest developments in the Parker probe and whether it has safely reached the corona.
Figure | Artist's vision of a Parker probe close to the sun (Source: NASA)
Through the data returned by Parker, the scientists found an interesting phenomenon that the critical surface of Alvin is not smooth, but has "wrinkles" like an old man.
The Alvin critical surface is located at the position of "the end of the solar atmosphere and the beginning of the solar wind", and since the sun has no solid surface, this position becomes the interface in the conventional sense.
The researchers noticed that the regress points below the Alvin critical surface were much smaller than the retracement points above them. This discovery could mean that no regurgitation will form within the corona.
"We've been looking at the sun and its corona for decades, and we know there's interesting physics going on there to heat up and accelerate the solar wind plasma, but we still can't say exactly what this physics is." Nour Raouafi, a scientist on NASA's Parker Solar Probe program, said.
"As the Parker Solar Probe now flies into the magnetically dominated corona, we will gain long-awaited insights into the inner workings of this mysterious region."
-End-
reference:
1.J.C. Kasper et al. Physical Review Letters127,255101(2021).
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.255101
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