Sun 1, Comet 0

[tvashtarkatena]

 

Now that's a Big Bang

 

One celestial coincidence that made for some fine reality TV.

[murraysovereign]

Cool, but shouldn't the comet's tail be pointed directly away from the sun, regardless of the comet's direction of travel? The dust trail would track along with the direction of the comet, but it would be quite faint. That bright tail we see in the image must be the ablated gases and other material being blown off the nucleus by the solar wind, in which case it should be pointing directly away... ?

 

I'm no astrophysicist, so maybe someone can 'splain that to me?

[tvashtarkatena]

Like any orbiting object, a comet is constantly changing direction - tail particles emitted sooner travel in a different direction then those emitted later. The effect is increased with elliptical orbits, because the coma is accelerating in addition to changing direction. If the comet were sitting still in space, or headed directly for the sun, the tail would point directly away from the sun in a straight line.

 

 

Edited May 14, 2011 by tvashtarkatena

[Crux]

Right when a post was logged to Spray... there go a CME and teh wurst fukkin weather. Ever.

 

Nuf said.

 

 

[TheOtter]

 

You otter check this:

OTTER CLICK IT

 

 

 

[tvashtarkatena]

Hmmm...almost accurate.

 

Cliff Claven to the rescue...

 

Ion tails don't exactly point directly away from the sun, the ion particles themselves MOVE almost directly away from the sun with the solar wind (with the comet's velocity component thrown in at first). The ion trail bends just like the dust tail does, only the curvature is much slighter. Ionized particles leave the nucleus at near the speed of the solar wind - about a million mph, much faster than the comet's velocity of tens of thousands of mph. In addition, the visible portion of the ion tail is relatively short due to rapid dissipation - too short for this slight curvature to be noticeable.

 

The dust trail doesn't go along the comet's path like a reverse airliner's contrail, as the above article claims (towards the direction of travel?...only if the comet is headed away from the sun, not towards). Dust particles fly off the nucleus as its ice sublimates, they are then blown away from the nucleus by by the solar wind in a vectored directly the combines the comet's and solar wind's velocity and direction. Not being ionized, however, dust particles leave the nucleus at much lower velocities that are much closer the comet's velocity. The dust tail can also be visible for millions of miles. For these two reasons, a dust tails tighter curvature is much more noticeable than for the ion tail.

 

The comet's dust tail in the video is 'following' the nucleus because it's headed nearly directly towards the sun. If it had missed and swung around the sun in a tight elliptical orbit, the dust tail would have pointed more perpendicular to the comet's direction of travel, then more toward its direction of travel as it moved away from the sun.

 

It's a vector thing.

Edited May 16, 2011 by tvashtarkatena

[tvashtarkatena]

First extrasolar vacation destination?