ESA’s Solar Orbiter will meet the “two tails” of the disintegrating ATLAS comet in the coming days. The spacecraft is currently en route to the inner solar system, and ESA scientists have urgently commissioned four key scientific instruments in preparation for the unexpected encounter.
The solar orbiter is designed to be in close contact with our stars several times, during which time it will use a set of 10 scientific instruments to characterize the sun and the heliospheric layer. When the solar orbiter launched at 05:03 on February 10, mission operators were unaware that the spacecraft was “rendezvous” with the tail of comet C/2019 Y4 (ATLAS).
The lucky coincidence was not discovered until earlier this month, when Geraint Jones of the Rader Space Science Laboratory at University College London discovered that the probe would pass 44 million kilometers from the ATLAS comet and could actually encounter its dispersal tail as early as May 31. Jones notified ESA and, along with other authors, wrote a short essay detailing the passage and its possible scientific implications, the study, published May 5 in the journal Research Notes of The AAS.
Comet ATLAS was observed to brighten significantly after it was discovered on December 28, 2019, leading some to believe that it could even become visible to the naked eye. However, the comet then became darker and darker, and in early April it was observed that the comet’s nucleus split into small pieces in early April. In mid-May, it broke into smaller chunks, highlighting the fragility of the icy solar system.
ATLAS is still likely to “survive” with the sun on May 31st, when it will be 37 million kilometers away. However, it is likely to throw less dust and gas than some scientists would like. Thankfully, the solar orbiter will get one last chance to learn about ATLAS before ITUSist completely disintegrates.
The four instruments that will be used to examine the tail of the ATLAS comet won’t be fully operational until June 15, but thanks to the special efforts of ESA scientists and engineers, they will all turn on and harvest the data during their encounter with the comet. Comets are important contributors to particle debris in the inner solar system. By reading as the orbiter passes, scientists can gain important information that will help them understand the dust environment around the star.
The solar orbiter will pass through the ion tail of ATLAS on May 31. The probe will then encounter the physical trajectory of the comet, made up of dust and gas particles, on June 6, a few days later. The success of this work will depend largely on the density of the comet’s tail. During the Encounter, the probe’s solar wind analyzer will attempt to detect changes in the magnetic field between the planets, which are caused by interactions with ions flowing from the comet.
If there are enough particles, some may also hit the detector itself. High-speed impacts vaporize these particles instantaneously and generate a charged gas cloud, which is then analyzed by the spacecraft’s radio and plasma wave instruments. Finally, the solar wind analyzer instrument will try to actually capture particles belonging to the tail of the “Lone Ranger”.
Once the comet probe is complete, the solar orbiter will continue to move inward and in the direction of “rendezvous” with the sun. The closest star “rendezvous” will take place on June 15, when the spacecraft will pass 42 million kilometers from the sun’s “surface.”
“With each encounter with a comet, we learn more about these interesting objects. If the solar orbiter detects the presence of the ATLAS comet, then we will learn more about how the comet interacts with the solar wind, and we can check, for example, whether our expectations of dust tail behavior are consistent with our model,” Jones explained. “All missions that encounter comets provide fragments in the puzzle. “