Solar Orbiter Plane Enters Comet Leonard’s Tail As It Heads Forward to the Sun

Comet Leonard at its closest point to Earth, December 12, 2021. Image: Christian Gloor/CC BY 2.0

SPACE — As Comet Leonard said goodbye to Earth and flew past Venus, a spacecraft headed for the sun flew through the comet’s long tail. According to scientists, the incident was quite an interesting bonus, considering it was unplanned.

“This kind of additional science has always been an exciting part of space missions,” said Daniel Müller, ESA project scientist for the Solar Orbiter., Friday, January 28, 2022.

Known as Comet C/2021 A1, Leonard is a skywatcher’s most spectacular visitor in 2021. It stands out quite a bit, especially in the days leading up to its closest point to Earth on December 12, 2021. And coincidentally, the Agency’s Solar Orbiter mission European Space Agency (ESA) flies through the comet’s tail.

The spacecraft collected comet data until about December 17. At that time, Comet Leonard was moving away from Earth towards the sun. On January 3, the comet reaches its closest point to the sun.

While the Solar Orbiter has just completed a flyby of Earth on November 27 and will head towards the sun. According to the ESA, although the comet’s core is near Venus and is 44.5 million kilometers from the Solar Orbiter, the comet’s tail extends past Earth’s orbit.

Map of the solar system showing where Comet Leonard will be as it approaches Earth on December 12, 2021. Image: NASA
Map of the solar system showing where Comet Leonard will be as it approaches Earth on December 12, 2021. Image: NASA

Samuel Grant, a graduate student at University College London, said he realized the Solar Orbiter flew through the comet’s tail after a computer program combined the spacecraft’s trajectory, the comet’s orbit and the solar wind to form the comet’s ionic tail. The solar wind is a constant flow of charged particles out of the sun and across the solar system.

Although the Solar Orbiter was designed to study the sun, it carried several instruments capable of gathering data about Comet Leonard’s tail as it crossed. For example, the aircraft’s Solar Wind Analyzer instrument suite detects the comet’s ions and compounds, including oxygen and carbon dioxide ions. In addition, the plane’s magnetometer detected signs of magnetic disturbances that might be caused by the comet’s interaction with the sun’s magnetic field.

Of course, Solar Orbiter also took some photos. Specifically, the spacecraft collects ultraviolet images that help scientists study water in comets. Then, light images that can further detail the activity of the comet’s dust.

Although the Solar Orbiter is the only mission to directly cross the tail of Comet Leonard, many other spacecraft in the inner solar system are also studying the comet. This includes the STEREO-A spacecraft, NASA’s Parker Solar Probe, and the joint NASA/ESA mission SOHO.

Daniel Müller said the Solar Orbiter also passed the tail of Comet ATLAS in 2020, shortly after it was launched from Earth. However, when Comet ATLAS passed, it was still in the process of calibrating the aircraft and its various instruments.

“But with Comet Leonard we were completely prepared and the comet didn’t fall apart,” said Daniel Müller.

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