ESA’s solar orbiter meets the tail of the fragmented comet ATLAS | Astronomy, Space exploration
Long-period comet C / 2019 Y4 (ATLAS) fragmented during its perihelion in April 2020. About two months later, ESA’s Solar Orbiter observed the dusty tail of the fragmented comet as the spacecraft space was at a distance of about 0.5 AU from the Sun. .
C / 2019 Y4 (ATLAS) was a comet with a near-parabolic orbit and an orbital period of about 6,000 years.
Also known as comet ATLAS, the object was discovered on December 28, 2019 by a reflecting telescope atop Mauna Loa in Hawaii as part of the Earth Asteroid Impact Alert System (ATLAS).
At the time of its discovery, the comet was about 3 AU from the Sun and was shining at a magnitude of 19.6 in the constellation Ursa Major.
In April 2020, it fragmented just before its closest approach to the Sun, leaving its old tail trailing through space in the form of clouds of dust and charged particles. The decay was observed by the NASA / ESA Hubble Space Telescope.
In June 2002, ESA’s Solar Orbiter approached the remains of the tail during its current mission.
Using the combined measurements of all Solar Orbiter in situ instruments, Lorenzo Matteini, solar physicist from Imperial College London, and his colleagues reconstructed this meeting.
The resulting model indicates that the ambient interplanetary magnetic field carried by the solar wind “rotates” around the comet and surrounds a central region of the tail with a weaker magnetic field.
“Comets are generally characterized by two distinct tails; one is the well-known shiny, curved dust tail, the other – usually weaker – is the ion tail, ”the researchers said.
“The ion tail comes from the interaction between cometary gas and the surrounding solar wind, the hot gas of charged particles that constantly blows from the Sun and permeates the entire solar system.”
“When the solar wind interacts with a solid obstacle, like a comet, its magnetic field is thought to bend and ‘drape’ around it.”
The simultaneous presence of magnetic field draping and cometary ions released by the melting of the ice core then produces the characteristic second ion tail, which can extend great distances downstream from the comet’s nucleus.
“This is a fairly unique event and an exciting opportunity for us to study the composition and structure of cometary tails in unprecedented detail,” said Dr Matteini.
“I hope that with NASA’s Parker Solar Probe and ESA’s Solar Orbiter now orbiting the Sun closer than ever, these events could become much more frequent in the future! “
Scientists presented the results this week at Royal Astronomical Society National Astronomical Meeting 2021 (NAM 2021).
L. Matteini et al. Waves and structures of the Solar Orbiter meeting with the tail of comet C / 2019 Y4 (ATLAS); signatures of magnetic field draping and cometary pickup ion instabilities. NAM 2021