Parker Solar Probe: Touching the Sun for the First Time
The Solar Parker Probe has flown below that critical limit where the solar atmosphere ends. The solar probe, designed for extremes, will approach even closer.
NASA's Parker Solar Probe has flown through the Sun's outer atmosphere, becoming the first spacecraft to touch this star, according to the U.S. space agency. The passage through the sun's corona took only a few hours and took place back on April 28, 2021, it said.
"Touching the stuff the sun itself is made of" will provide a wide variety of information about our central star and its influence on the solar system, the statement said. Particles and magnetic fields were studied in the solar corona. First results of this flyby have now been published in the journal "Physical Review Letters".
The probe orbits the sun on elliptical orbits and will approach it even closer in the coming months and years. At its last closest approach to date (perihelion) on November 21, 2021, it was about 8.5 million kilometers above the surface. It is currently traveling at a speed of more than 590,000 kilometers per hour. At this speed, it could cover the distance Earth-Moon in less than an hour. A few weeks earlier, it had picked up momentum from Venus.
The Alfvén surface marks the end of the Sun's atmosphere
Unlike the Earth, the Sun has no solid surface. The components of its atmosphere are bound to the Sun by gravity and magnetic forces, but are pushed away from it by heat and radiation pressure. Beyond a certain limit, gravity and magnetic fields are too weak to prevent the material from escaping - it becomes solar wind, which disappears into space without ever being recaptured by the Sun. The boundary at which this happens is called the Alfvén surface. It marks the outer end of the solar atmosphere. During its flyby of the Sun last April, the Parker Solar Probe passed this boundary several times, which does not extend spherically around the Sun but has numerous irregularities and bulges.
The probe had already come closer to the Sun than any other spacecraft before, just a few months after its launch in August 2018. At that time, it had come closer than 42.7 million kilometers to the sun, breaking the record set in April 1976 by the German-American Helios-2 probe. By the end of its mission, it will have come within 6.16 million kilometers of the sun.
Protected by an almost twelve-centimeter-thick armor made of carbon fiber, the 680-kilogram flight vehicle, which is the size of a small car, should be able to withstand extreme heat and radiation. NASA hopes that the mission, which is scheduled to last until 2025, will provide insights into why the corona is many times hotter than the surface of the sun and thus into how stars work. The data could also make future predictions of "space weather" more accurate. The idea is to better understand the solar wind. Depending on its strength, the stream of charged particles can disrupt terrestrial telecommunications and satellite communications when it hits Earth.
Spectrum of Science
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Originalartikel auf Spektrum.deTitelbild: Nasa/Johns Hopkins APL/Steve Gribben
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