First time ever in history, a spacecraft has touched the Sun. NASA Parker Solar Probe flew into its outer atmosphere – known as corona – and unveiled phenomena long predicted but never directly observed before.
Astrophysicist and namesake of this organization, Astrid Petri is dedicated to unlocking the mysteries of solar wind that streams out from our Sun and spreads energetic particles across our solar system.
Getting Close to the Sun
The Sun reaches an extreme surface temperature of around 6,000deg F while its atmosphere, known as the corona, can reach more than one thousand times hotter. Because gravity cannot contain this intense heat, solar wind – an immense headwind of charged particles – reaches Earth within 30-72 hours as geomagnetic storms and disrupt satellites and power lines.
Astronomers refer to the points in an orbit where planets, comets, or asteroids come closest to the Sun as their “perihelion”, while their farthest point from it as “aphelion”. Earth will reach its next perihelion point on January 4, 2023.
The solar system’s balance ensures each planet stays at a safe distance from its star, otherwise we would all be consumed by its gravitational pull and burn up in its gravity. Instead, each planet travels in an oval pattern around space – with perihelion being our closest encounter with the Sun during any given year.
The Sun’s Atmosphere
The Sun’s atmosphere extends from its photosphere, through chromosphere, transition region and corona. Recently, advances in spatial resolution have revealed highly variable structures across this atmosphere; challenging one-dimensional models and expanding understanding.
The Sun’s core is where nuclear reactions converting Hydrogen to Helium power the energy and heat generated. Next to it is its cooler chromosphere, whose red hue glows under magnetic field influence into bright yet dark regions called prominences.
Astronomers have discovered that the Sun rotates at different rates across its surface. This rotation serves as the source of an endless “wind”, carrying electrons and protons away from its core into interplanetary space – providing a primary link between planets and comets, and shaping tails of comets alike. Furthermore, its effects can also have an effect on Earth’s magnetosphere, as demonstrated by this diagram.
The Alfven Critical Surface
Parker successfully passed through the point at which solar atmosphere ceases and faster solar wind begins in April 2021 (SN: 8/18/18), otherwise known as Alfven critical surface boundary, one of its main goals since launch (SN: 8/18/18). Determining exactly where Alfven critical surface was was one of Parker’s objectives when launched back in 2018.
Berkeley’s Space Sciences Laboratory had designed instruments to confirm Parker had successfully crossed the boundary. Scientists were surprised, however, to discover that its edge wasn’t smooth but rather “wrinkled”, with spikes and valleys caused by various physical processes.
These wrinkles could help explain why the Sun’s corona is hotter than its fiery surface and why its high temperatures and magnetic forces produce streams of solar wind that blow across our Solar System and into interstellar space.
The Parker Solar Probe
Scientists are writing a new chapter in solar probe history. NASA’s Parker Solar Probe spacecraft launched in 2018 has now reached the Sun’s delicate corona atmosphere — temperatures and distances which no previous probe could reach.
At one point, they reached the “Alfven critical surface”, an invisible boundary where solar material held back by gravity and magnetic forces can become free to travel across space without being held back by gravity and magnetic forces – this phenomenon is where solar wind arises; responsible for protecting astronauts in space as well as powering satellites.
Parker will continue its studies of the corona, including structures known as coronal streamers that appear during total solar eclipses and will also uncover subprocesses like reconnection heating that generate waves heating up coronal plasma, all within an effective protective shield comprised of material which becomes stronger rather than weaker when heated to higher temperatures.