Solar Orbiter flies through the dusty remnants of exploded Comet ATLAS

European Space Agency’s Solar Orbiter flies through the dusty remnants of exploded Comet ATLAS in a unique chance encounter, revealing how solar wind’s magnetic field ‘drapes’ over the tail

The Solar Orbiter made its chance encounter with comet ATLAS in June 2020
It turned on its instruments as it passed through the remnants of the comet tail
Astronomers have recreated that encounter using a new mathematical model
This allowed them to track the solar winds passing over the dust and particles
They found the background ‘magnetic field’ drapes over the top of the tail

The European Space Agency (ESA) probe ‘Solar Orbiter’ had a chance encounter with the exploded Comet ATLAS, flying through its dusty tail.

Doing so provided astronomers with a unique opportunity to study the remnants of a frozen object formed in the most distant regions of the solar system.

ATLAS was discovered in December 2019 and initially it was suggested it would become one of the brightest comets visible to the naked eye, but it began to disintegrate in March 2020 as it made its closest approach to the sun.

It left its tail behind when it disintegrated, and in June 2020 the ESA Solar Orbiter passed through the tail of the comet while travelling to the sun to begin its mission.

Studying data from the probe’s instruments, Imperial College London experts found the sun’s background magnetic field ‘drapes’ over the comet, carried by solar winds.

They hope that as the probe, and the NASA Parker Solar Probe also studying the sun, will be able to explore the remnants of the comet in more detail in the coming years.

Hubble space telescope observations from April 2020 captured the ATLAS comet breaking apart as it became closer to the sun

The encounter with ATLAS, pictured, was not planned — the Solar Orbiter probe was launched in February to study the sun up-close, with a focus on the star’s polar regions

ESA’s Solar Orbiter ‘accidentally’ passes through the tails of Comet ATLAS

ESA’s Solar Orbiter probe will ‘accidentally’ passed through the tails of Comet ATLAS at the end of May.

Scientists switched on four of the spacecraft’s instruments especially to take advantage of this rare opportunity in order to conduct ‘bonus science’.

The encounter with ATLAS was not planned — the Solar Orbiter probe was launched in February to study the sun up-close, with a focus on the star’s polar regions.

Solar Orbiter mission scientists were altered to the window for data gathering by planetary scientist Geraint Jones of Britain’s Mullard Space Science Laboratory.

The probe collected data on the separate trails of dust and charged particles released from the comet as it is slowly vaporised by the solar radiation from the Sun.

The craft passed within 27.3 million miles (44 million km) of the comet’s core, or ‘nucleus’ — passing through the ion tail on May 31–June 1 and the dust tail on June 6.

Comet tails are made up of dust and charged particles that interact with the solar winds as they enter the inner solar system and feel the influence of the sun.

Sometimes, as was the case with ATLAS, they break apart due to the solar radiation and the Hubble Space Telescope observed this moment of destruction in April 2020.

Soon after launching, the Solar Probe team realised that its path would go through the tail of the comet, something it hadn’t been designed to handle.

In fact the instruments on board weren’t due to be switched on until much later in the mission, but they decided to see if they could ‘make it work’.

After the comet broke apart the team wasn’t sure if there would be anything to detect but they went ahead with plans to switch the instruments on early and rendezvous with the cometary tail.

As it passed through the remnants of the tail, astronomers switched on all of the in-situ instruments on the Solar Probe to get as broad of a picture as possible.

They discovered that the ‘ambient interplanetary magnetic field,’ a field of particles carried by solar winds, ‘drapes’ around the comet.

It then surrounds a central tail region with a weaker magnetic field, they found.

Comets are typically characterised by two separate tails; one is the well-known bright and curved dust tail, the other – typically fainter – is the ion tail.

The ion tail originates from the interaction between the cometary gas and the surrounding solar wind, the hot gas of charged particles that constantly blows from the Sun and permeates the whole 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.

Researchers ‘recreated’ the encounter with the comet, and in this diagram, lines identify interplanetary magnetic field lines in the solar wind that are draped around the comet

The simultaneous presence of magnetic field draping and cometary ions released by the melting of the icy nucleus then produces the characteristic second ion tail, which can extend for large distances downstream from the comet’s nucleus.

Lorenzo Matteini, a solar physicist at Imperial College London and leader of the work, described it as a ‘unique event’.

Adding it is also an ‘exciting opportunity for us to study the makeup and structure of comet tails in unprecedented detail.’

‘Hopefully with the Parker Solar Probe and Solar Orbiter now orbiting the Sun closer than ever before, these events may become much more common in future!’

ESA says the instruments on the spacecraft are ‘working beautifully’ and providing a holistic view of the Sun and solar wind in a way never before seen

It was one of the very few cases where scientists have been able to make direct measurements from a fragmented comet.

Data from this encounter is expected to contribute greatly to scientists understanding of the interaction of comets with the solar wind and the structure and formation of their ion tails.

This in turn could help work out why they disintegrate as they get closer to the inner solar system.

The findings were presented at the Royal Astronomical Society National Astronomy Meeting.

Explained: The difference between an asteroid, meteorite and other space rocks

An asteroid is a large chunk of rock left over from collisions or the early solar system. Most are located between Mars and Jupiter in the Main Belt.

A comet is a rock covered in ice, methane and other compounds. Their orbits take them much further out of the solar system.

A meteor is what astronomers call a flash of light in the atmosphere when debris burns up.

This debris itself is known as a meteoroid. Most are so small they are vapourised in the atmosphere.

If any of this meteoroid makes it to Earth, it is called a meteorite.

Meteors, meteoroids and meteorites normally originate from asteroids and comets.

For example, if Earth passes through the tail of a comet, much of the debris burns up in the atmosphere, forming a meteor shower.

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