How did comet Lovejoy survive its trip around the sun?

Mar 14, 2012 by Jason Major, Universe Today
Comet C/2011 W3 (Lovejoy) re-emerging from behind the Sun on Dec. 15, 2011. Credit: NASA/SDO

It was just about three months ago that the astronomy world watched in awe as the recently-discovered comet Lovejoy plummeted toward the Sun on what what expected to be its final voyage, only to reappear on the other side seemingly unscathed! Surviving its solar visit, Lovejoy headed back out into the solar system, displaying a brand-new tail for skywatchers in southern parts of the world (and for a few select viewers above the world as well.)

How did a loosely-packed ball of ice and rock manage to withstand such a close pass through the Sun’s blazing corona, when all expectations were that it would disintegrate and fizzle away? A few researchers from Germany have an idea.

Scientists from the Max Planck Institute for Extraterrestrial Physics and the Braunschweig University of Technology have hypothesized that managed to hold itself together through the very process that, to most people, defines a : the outgassing of sublimated icy material.

As a comet near the Sun, the increased heating from solar radiation causes the frozen materials within the to sublimate — go directly and suddenly from solid to gas, skipping the liquid middle stage — and, in doing so, burst through the surface of the comet and create the long, hazy reflective tail that is so often associated with them.

Overview of the forces acting on sungrazing comets. Credit: Illustration from paper

In the case of Lovejoy, which was on a direct path toward the Sun, the sublimation itself may have provided enough outward force across its surface to literally keep it together, according to the team’s research.

“The reaction force caused by the strong outgassing (sublimation) of the nucleus near the Sun acts to keep the nucleus together and to overcome the tidal disruption,” the paper claims.

In addition, the team states that the size of the comet’s nucleus can be derived using an equation that takes into consideration the combined forces of outgassing, the material composition of the comet’s nucleus, the comet’s own gravity and the tidal forces exerted by the comet’s close proximity to the Sun (i.e., the Roche limit).

Using that equation, the team concluded that the diameter of Comet Lovejoy’s nucleus is anywhere between 0.2 km and 11 km (.125 miles and 6.8 miles). Any smaller and it would have lost too much material during its pass (and had too little gravity); any larger and it would have been too thick for outgassing to provide enough counterbalancing force.

If this hypothesis is correct, taking a trip around the may not mean the end for all comets… at least not those of a certain size!

Watch the video of Lovejoy’s Dec. 15 solar swing below:

This video is not supported by your browser at this time.

The paper was submitted to the journal Icarus on March 8, 2012 by Bastian Gundlach. See the full text here.

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User comments : 4

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Doug_Huffman
not rated yet Mar 14, 2012
Leidenfrost Effect writ large.
HannesAlfven
1 / 5 (3) Mar 14, 2012
But, what about the exploding comets which appear to do so in response to solar outbursts? See David Talbott's video "Elenin and the Mystery of Exploding Comets" ...

http://www.youtub...DWYHJpqg

Does ice explode in response to charged particles? Why is the explosion velocity so high?

Anybody who proposes that the way to understand complex phenomena is to isolate and calculate just doesn't get it. David Bohm showed us that if a person does not know that a random number generator is being used, then a string of numbers can be assumed to be random. But, the second that the more meta, interdisciplinary view is adopted, the apparently random phenomenon stops being random. Randomness is a feature of CONTEXT, and by choosing the most focused context for answering questions about comets, the answers will not generally hold water.

David Talbott and Wal Thornhill's plasma-based explanation for comets takes the interdisciplinary view necessary to FULLY explain comets.
kaasinees
2 / 5 (4) Mar 14, 2012
This is easy to explain with heat capacity, the structure and substances that make the comet.
Callippo
not rated yet Mar 14, 2012
At first, the density of solar surface is 20.000-time lower, than the density of Earth atmosphere. It's essentially a very good vacuum, which would glow very slightly inside of glass tube of common size. The plasma inside of common neon sign is way more energetic, dense and hot. If the Sun would be just a bit less hot, it would be transparent deeply beneath its surface and we could see the stars through it. We can observe it at the case of sunspots - from proximity they would appear like gigantic basins of colder transparent plasma, essentially forming the cavities or gigantic bubbles at the sun surface.

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