Comet’s dust trail stretches over 10 million km

Comet 67P/Churyumov-Geraimenko’s dust trail has been observed to stretch at least 10 million kilometres in the latest images taken by professional astronomers working on the ground-based observing campaign.

The image mosaic shown here is composed of four images taken using the 2.5 m Isaac Newton Telescope on La Palma on the night of 12 March.

R-band mosaic of Comet 67P/C-G on 12 March 2016, taken with the 2.5m Isaac Newton Telescope on La Palma. The brightest part of the comet was imaged for 30 minutes, while the most distant parts of the dust trail required 1 hour of exposure. Credit: Isaac Newton Group/John Davies/Alan Fitzsimmons/Colin Snodgrass.

R-band mosaic of Comet 67P/C-G on 12 March 2016, taken with the 2.5m Isaac Newton Telescope on La Palma. The brightest part of the comet was imaged for 30 minutes, while the most distant parts of the dust trail required 1 hour of exposure. Credit: Isaac Newton Group/John Davies/Alan Fitzsimmons/Colin Snodgrass.

The image shows reflected light from dust grains and highlights the comet’s various tail structures. Similar images were obtained by amateur astronomers a few months ago when the comet was closer to the Sun and much brighter.

Most striking is the long trail, stretching over two degrees from the comet – equivalent to the apparent size of four full Moons on the sky as seen from Earth (see graphic below for scale) – or greater than 10 million kilometres at the comet’s distance. By comparison, Rosetta is flying beside the comet nucleus as close as just 10 km.

The long trail is made up of larger grains left behind in the orbit of the comet, probably from several previous passages of the comet around the Sun. When the Earth passes through similar dust trails from other comets it gives rise to meteor showers. Unfortunately this won’t happen with 67P/C-G, as the orbit does not approach our planet.

The shorter dust tail just below the trail is a ‘neck-line’ structure, made from dust grains ejected by the comet during this current orbit.

Any anti-solar tail of the comet would be to the south but not so readily seen; in any case it would be very foreshortened in this geometry as the comet was at opposition, and at about 3 degrees phase angle, so the tail is mostly ‘behind’ the coma from our point of view.

Comet 67P/C-G’s long dust trail, seen with a full moon for scale. Note that the Moon shows the apparent scale on sky as seen from Earth rather than the physical scale – the Moon would be much smaller at the comet's distance. Credit: Isaac Newton Group/John Davies/Alan Fitzsimmons/Colin Snodgrass.

Comet 67P/C-G’s long dust trail, seen with a full moon for scale. Note that the Moon shows the apparent scale on the sky as seen from Earth rather than the physical scale – the Moon would be much smaller at the comet’s distance. Credit: Isaac Newton Group/John Davies/Alan Fitzsimmons/Colin Snodgrass.

See our previous blog post “Twin tails” for more about the comet’s dust trails.

Read more about the professional observing campaign in recent blog posts here and here, and keep up to date with latest images from the Professional-Amateur Collaborative Astronomy project community here and here.

Many thanks to Colin Snodgrass, Alan Fitzsimmons and John Davies for inputs to this blog post!

Comments

4 Comments

  • Kamal says:

    Who would have thought the old man to have had so much blood in him?

  • Kamal says:

    Harvey: Here is a fun question to think about. Suppose that instead of planning to land Rosetta on C-G, the mission planners picked one of these large dust grains (say its size is of the order of meters) to land on. What would happen? I imagined some possibilities below, but there must be more one can come up with:

    1) The electrical activity on Rosetta would lead to spontaneous combustion and Rosetta would be burnt up in a fire.

    2) Something that large is obviously a rocky boulder, so Rosetta might get smashed, but with the low gravity it might just bounce off like Philae did off C-G.

    3) The boulder would disintegrate under Rosetta’s weight leaving it covered with lots of organic stuff, perhaps even living things if C-G has them.

    4) Rosetta would gently land and settle down, and the dust grain would move farther and farther into the tail over time.

  • Kamal says:

    After reading about the post on the finding of amino acids, am convinced that the comet definitely knows how to make fun of me.

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