January 26, 2023

Solar Orbiter Spacecraft Catches a Second Comet by the Tail

Metis is Solar Orbiters multi-wavelength coronagraph. “The visible light images can hint at the rate at which the comet is ejecting dust, while the ultraviolet images can provide the water production rate,” states Alain Corso, a Metis co-investigator at the CNR-Istituto di Fotonica e Nanotecnologie, Padova, Italy.

For a spacecraft created to carry out unique studies of the Sun, Solar Orbiter is likewise making a name for itself exploring comets. For a number of days fixated 1200-1300 UT on December 17, 2021, the spacecraft found itself flying through the tail of Comet C/2021 A1 Leonard.
A composite of Comet Leonard images recorded December 15-16, 2021, in visible light by the Metis instrument onboard the ESA/NASA Solar Orbiter spacecraft. The comet transited throughout the field of vision with its dust and ion tails pointing towards the instrument. Credit: ESA/Solar Orbiter/Metis Team
The encounter caught information about the particles and electromagnetic field present in the tail of the comet. This will enable astronomers to study the method the comet engages with the solar wind, a variable wind of particles and magnetic field that originate from the Sun and sweep through the solar system.

” The huge benefit is that for basically no effort on the spacecrafts part, you get to sample a comet at an enormous distance. Thats pretty exciting,” says Samuel, who is now looking at archive data from other spacecraft searching for comet tail crossings that have actually so far gone undetected.
The work likewise helps construct experience for ESAs Comet Interceptor objective, for which Geraint is the Science Team Lead. The mission will visit an as-yet undiscovered comet, making a flyby of the target with 3 spacecraft to produce a 3D profile of a dynamically new object which contains unprocessed product surviving from the dawn of the Solar System.
The ESA/NASA Solar Orbiter spacecraft flew through the tail of Comet C/2021 A1 Leonard in December 2021, gathering images and in-situ solar wind and particle data. At the exact same time, SOHO (ESA/NASA), Parker Solar Probe (NASA) and STEREO-A (NASA) were likewise enjoying the comets evolution from other angles.
In the meantime, the instrument groups on Solar Orbiter are busy examining the Comet Leonard information not just for what it can tell them about the comet however about the solar wind.
” This kind of extra science is constantly an amazing part of a space objective,” states Daniel Müller, ESA Project Scientist for Solar Orbiter. With Comet Leonard we were totally ready– and the comet didnt fall apart.”.
Solar Orbiter. Credit: ESA/ATG medialab.
In March, Solar Orbiter makes its closest pass to the Sun yet at a distance of 0.32 au (approximately one-third of the Earth-Sun range, or about 50 million kilometers). It is among practically 20 close passes to the Sun that will take place during the next decade. These will lead to unmatched images and information, not just from close up, however likewise from the Suns never-before seen polar regions.
” There is a lot to anticipate with Solar Orbiter, were only just getting begun,” states Daniel.

A composite of Comet Leonard images captured December 15-16, 2021, in noticeable light by the Metis instrument onboard the ESA/NASA Solar Orbiter spacecraft. The comet transited across the field of view with its dust and ion tails pointing towards the instrument. Credit: ESA/Solar Orbiter/Metis Team.

This information plot uses solar wind speed and instructions information from the Solar Wind Analysers proton and alpha sensor (SWA-PAS) to estimate how close the ESA/NASA Solar Orbiter spacecraft approached to the center of Comet C/2021 A1 Leonards ion tail throughout December 2021. A composite of Comet Leonard images caught December 15-16, 2021, in ultraviolet light by the Metis instrument onboard the ESA/NASA Solar Orbiter spacecraft. NASAs Parker Solar Probe was almost on the opposite side of the Sun from the ESA/NASA Solar Orbiter spacecraft when its WIPSR instrument taped images of Comet Leonard on December 7, 2021. NASAs Parker Solar Probe was almost on the opposite side of the Sun from the ESA/NASA Solar Orbiter spacecraft when its WIPSR instrument tape-recorded images of Comet Leonard on December 7, 2021. The ESA/NASA Solar Orbiter spacecraft flew through the tail of Comet C/2021 A1 Leonard in December 2021, collecting images and in-situ solar wind and particle data.

NASAs Parker Solar Probe was nearly on the opposite side of the Sun from the ESA/NASA Solar Orbiter spacecraft when its WIPSR instrument taped images of Comet Leonard on December 7, 2021. From Parker Solar Probes perspective the comet appeared to pass straight between Venus and Earth. Credit: NASA/USNRL/G. Stenborg/K. Battams.

The Solar Orbiter Heliospheric Imager (SoloHI) also captured data. These images reveal big parts of the comets ion tail taken while the spacecraft itself was inside the tail. As the image series progresses, modifications in the tail can be seen in action to variations in the solar wind speed and instructions.
And it was not simply Solar Orbiter that was enjoying the crossing. The ESA/NASA SOHO mission and NASAs STEREO-A and Parker Solar Probe spacecraft were observing from afar. This means that not just do astronomers now have information from inside the tail, they also have contextual images from these other spacecraft (see images above).
The SOHO spacecraft identified Comet Leonard in its Solar Wind Anisotropies (SWAN) instrument in Lyman-alpha. SWAN doesnt look directly at the Sun, it rather maps the whole sky in ultraviolet light, and sees interstellar hydrogen that engages with the solar wind. The maps can be utilized to expose brilliant points in ultraviolet light indicating the presence of a comet, for example, as is the case here. Credit: SOHO (ESA & & NASA); W. Boonplod.
Comet tail crossings are fairly unusual events. Of those that have actually been found, most have actually been discovered only after the event. The ESA/NASA Ulysses objective experienced three comet ion tails, including that of C/1996 B2 Hyakutake in May 1996, and C/2006 P1 McNaught in early 2007. Solar Orbiter itself crossed the tail of fragmenting comet C/2019 Y4 ATLAS in May and June 2020, quickly after releasing.
Whereas the early crossings were a surprise, both of Solar Orbiters encounters were predicted beforehand thanks to the computer code developed by Geraint Jones, University College London Mullard Space Science Laboratory, and extended by Samuel.

NASAs Parker Solar Probe was practically on the opposite side of the Sun from the ESA/NASA Solar Orbiter spacecraft when its WIPSR instrument taped images of Comet Leonard on December 7, 2021. From Parker Solar Probes perspective the comet appeared to pass straight between Venus and Earth.

The crossing had actually been predicted by Samuel Grant, a post college student at University College Londons Mullard Space Science Laboratory. He adapted an existing computer system program that compared spacecraft orbits with comet orbits to consist of the effects of the solar wind and its ability to form a comets tail.
This plot series represents information collected by the Solar Wind Analysers Heavy Ion Sensor as the ESA/NASA Solar Orbiter spacecraft travelled through Comet Leonards tail in December 2021. The data cover December 11-20, with the last and first plot before and after the tail crossing, respectively, marked by an absence of singly ionized ions. During the tail crossing the instrument discovered particles that are attributable to the comet instead of the solar wind, for example ions of oxygen, carbon, and molecular nitrogen, and molecules of carbon monoxide gas, carbon dioxide, and water. (Ions are atoms or particles that have been stripped of several electron and now bring a net positive electrical charge.) Credit: ESA/Solar Orbiter/SWA group
” I ran it with Comet Leonard and Solar Orbiter with a couple of guesses for the speed of the solar wind. Whichs when I saw that even for rather a wide range of solar wind speeds it appeared like there would be a crossing,” he states.
At the time of the crossing, Solar Orbiter was reasonably near to the Earth having gone by on November 27, 2021, for a gravity assist maneuver that marked the start of the objectives science stage, and put the spacecraft on course for its March 2022 close technique to the Sun. The comets nucleus was 44.5 million kilometers away, close to the planet Venus, however its giant tail stretched throughout area to Earths orbit and beyond.
This information plot utilizes solar wind speed and instructions information from the Solar Wind Analysers proton and alpha sensor (SWA-PAS) to estimate how close the ESA/NASA Solar Orbiter spacecraft approached to the center of Comet C/2021 A1 Leonards ion tail during December 2021. The plot records how close each packet of solar wind identified by SWA-PAS is thought to have actually got to the comets nucleus throughout its journey from the Sun to the spacecraft. The left axis provides the scale in astronomical units (au), where 1 au is the distance from the Sun to the Earth, and the same range is revealed in kilometers on the right axis.Changes in the solar wind circulation speed and direction are accountable for the variations in the outlined distance. There are brief data acquisition gaps on December 15 and 17. Credit: ESA/Solar Orbiter/SWA team & & S. Grant (UCL).
Far, the best detection of the comets tail from Solar Orbiter has actually come from the Solar Wind Analyser (SWA) instrument suite. Its Heavy Ion Sensor (HIS) plainly determined atoms, ions, and even particles that are attributable to the comet instead of the solar wind.
Ions are atoms or molecules that have been stripped of one or more electron and now carry a net favorable electrical charge. SWA-HIS detected ions of oxygen, carbon, molecular nitrogen, and particles of carbon monoxide gas, co2 and potentially water. “Because of their little charge, these ions are all clearly of cometary origin,” says Stefano Livi, Lead Investigator of SWA-HIS from Southwest Research Institute, Texas.
A composite of Comet Leonard images recorded December 15-16, 2021, in ultraviolet light by the Metis instrument onboard the ESA/NASA Solar Orbiter spacecraft. The comet transited across the field of vision with its dust and ion tails pointing towards the instrument. Credit: ESA/Solar Orbiter/Metis Team.
As a comet moves through area, it tends to curtain the Suns magnetic field around it. This magnetic field is being brought by the solar wind, and the draping develops discontinuities where the polarity of the magnetic field changes dramatically from north to south and the other way around.
The magnetometer instrument (MAG) data does undoubtedly suggest the existence of such draped electromagnetic field structures but there is more analysis to be done to be definitely sure. “We remain in the process of examining some smaller sized scale magnetic perturbations seen in our information and combining them with measurements from Solar Orbiters particle sensing units to understand their possible cometary origin,” states Lorenzo Matteini, a co-investigator on MAG from Imperial College, London.
In addition to the particle data, Solar Orbiter likewise got images.

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