- Solar System.This is the picture taken closer to the Sun
- Mission: NASA wants to reach the Sun
Since the beginning of time, man has lived solar eclipses with fascination. This phenomenon of alignment between the Sun, the Moon that hides it from our eyes and the Earth is of great interest to scientists, who only at that time can observe certain phenomena that occur in our star.
But NASA no longer only looks at the Sun from the ground or from somewhat closer satellites. Since August 12, 2018, it has a solar infiltrate, the Parker probe, which is currently only 24 million kilometers from the Sun (35 solar radii), a distance never before reached by a space mission. The mysteries he reveals have been made public this Wednesday, in four simultaneous articles in the journal Nature .
A mysterious dust free zone
Around the sun there are multiple dust rings. They are in the orbits of the planets, such as Earth, Venus or Mercury. They are the vestiges of the formation of the Solar System, remains of comets and debris from asteroid collisions. Scientists study them to know their composition and how they move in space. With this they try to understand the origin of the planets.
The dust ring in the orbit of Mercury was discovered by chance last year by researchers at the US Naval Research Laboratory in Washington Guillermo Stenborg and Russell Howard. They were not looking for the ring itself, but quite the opposite, an enigmatic dust-free area very close to the Sun that has been talked about for decades but has never been seen.
It is believed that the high temperatures of the Sun transform any very dust particles into gas, leaving a discontinuity of waste called DFZ (Dust Free Zone acronym). How to find this region without solid particles is complicated if viewed from Earth, Howard and his colleagues devised a technique and designed an instrument that has been installed aboard the Parker probe to see it. It is the Widefield Imager for Solar Probe (WISPR) camera that now shows, for the first time, the first signs of the existence of the dust-free zone around the Sun.
What "WISPR sees, is a very slight decrease in the intensity profile" of light reflected by the particles, "which indicates that there is no sudden disappearance of dust," Russell Howard, lead author of the World finding published Wednesday in the journal Nature. These are preliminary data in which there is a decrease in the intensity of light of the solar F-corona compared to what is seen - again - beyond "this dark area," Howard explained.
"If it is discovered that the dust-free zone exists, a prediction made 90 years ago will be confirmed. These observations will help improve theories related to the way in which dust passes from a solid particle to a gas. The composition of the dust is unknown. dust and it is unknown if there is more than one type, "he added.
The researcher waits for the Parker probe to get closer to the Sun to obtain definitive data of the dust-free zone. On December 26, Parker will already fly near Venus. At the end of January 2020, the satellite will be only 28 solar radios from our star , with a vision range of 8 solar radios. "We believe that at that distance we will see the dust-free zone, unless something new happens," Howard said.
The work of Russell Howard and his colleagues also describes very small eruptions of plasma expelled by the sun and that they observe with two forms, the so-called magnetic flux strings (already evidenced before) and the "predicted, but not yet observed, magnetic islands. "So far, as they write in their study.
The origin of the slow solar wind
The atmosphere of the Sun, the outermost layer of our star, which is called the crown and can be seen during a total eclipse, moves and moves away from the star. This movement is called solar wind and is due to the magnetic field. It can basically be of two types: fast (more than 500 kilometers per second) and slow (less than 500 kilometers per second). The fast has already been documented in other missions, while the slow is the great unknown.
A research team led by Stuart Bale at the University of California, Berkeley has studied this slow wind at 35 solar rays thanks to the Parker probe. Their results [https://www.nature.com/articles/s41586-019-1818-7] have also been published this Wednesday in the journal Nature.
" Where the slow solar wind originates is an open question. There are several theories . Our measurements show very clearly that the slow solar wind can emerge from small equatorial coronal holes," Stuart Bale has confirmed to this newspaper.
Bale explains that High-speed solar wind arises at the poles, in the depths of these holes when the Sun is most active. However, their data reveal that the origin of the slow solar wind is in the holes of the crown that are near the equator. Crown holes are areas that do not emit much radiation and appear dark when viewed with X-rays.
Bale's article presents a detailed and direct view of the magnetic field at very close distances from the Sun providing "unprecedented results," said the astrophysicist at the Institute of Astrophysics of the Canary Islands Fernando Moreno Insertis.
Moreno Insertis, who has not participated in this study has underlined the strong structuring of the magnetic field measured at that distance and its frequent polarity reversals. His study allows to locate directly and in situ, "the source of the solar wind that is currently going through the detectors on board the ship," he said.
More heat at a greater distance
Bale and his colleagues have confirmed, in addition, the presence of plasma emissions in the atmosphere that produce disturbances as a micro-stability and that these play, in turn, play an important role in plasma heating.
" It is the beginning of human knowledge about the acceleration of the solar wind and the heating of the crown, two closely linked phenomena. This has been unknown until now. It is a phenomenon similar to sitting next to a fire, moving away ten meters and notice much more heat than a meter. It is intriguing, curious and surprising, "said Javier Rodríguez-Pacheco, a scientist at the University of Alcalá who has not participated in this research.
Rodríguez-Pacheco belongs to the Solar Orbiter mission, which will support the Parker probe soon. The launch will take place in Florida in February. This new mission is not going to get so close to the sun, it will be next to the orbit of Mercury, but it will have a more complete instrumentation. It will carry instruments to detect the environment surrounding the ship and telescopes.
"Parker is blind, does not have those telescopes and Solar Orbiter will serve to give Parker eyes. We can also correlate the data Parker takes in situ at a certain location near the Sun with the Solar Orbiter measurements further back. This will be done along with observations of ships that are close to the Earth, so we will have an image of the interaction of the Sun with the Earth that we had never achieved, "said Rodríguez-Pacheco.
In another of the new articles, Justin Kasper (a researcher at the University of Michigan) and his colleagues measure and model the magnetic fields that increase the speed of the solar wind. They describe them as S-shaped curves that form in the lines of the magnetic fields that come from the Sun.
"One of the most relevant results has been to detect that such magnetic waves produce peaks of velocity in the plasma with a duration of several minutes and speeds of up to 50 kilometers per second. Such movements of the solar plasma question the current dynamic models of the solar corona and demonstrate, once again, that the physics of the Sun is fascinating, "Javier Trujillo Bueno, a CSIC researcher at the Institute of Astrophysics of the Canary Islands, told the media and has not taken part in this research.
On the other hand, David McComas (of Princeton University) and his collaborators have studied radiation or plasma eruptions that accelerate ions and electrons in the crown. The authors identify in the latest work of the journal Nature fast and slow particles that reach the probe with a path length is longer than expected, suggesting that the magnetic field has a more complicated geometry than previously assumed. The finding could corroborate the S-shaped magnetic field curves described by Parker.
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