How dark is it inside a comets coma?

Hi all....

Was thinking about comets last night and a question occured to me that I've
never seen addressed in the popular astronomy literature (not to say I've read
ALL of it though ...

Okay.....so Im on the surface of a comet.....the surface might be nice snowy
white....or it might be dark as charcoal.....I might be standing in an area
where its "raining" small particles and gases upwards gently....or I might
unfortunately be standing next to an explosive jet that makes Old Faithful look
like a dripping faucet by comparision....

My question is.....how much is the sky and sun attenuated by all the gas and
dust that makes up the comets coma? Do I just see a faint haze......or is there
so much scattered light that the "sky" looks like its filled with bright white
clouds....or is so much light scattered and absorbed that Im digging out my
flashlight so I can see where to walk?....

Of course it obviously depends on the comet....and its activity level.....

take care

Blll

(BllFs6) wrote:

Hi all....

Was thinking about comets last night and a question occured
to me that I've never seen addressed in the popular
astronomy literature (not to say I've read ALL of it though
...

Okay.....so Im on the surface of a comet.....the surface
might be nice snowy white....or it might be dark as
charcoal.....I might be standing in an area where its
"raining" small particles and gases upwards gently....or I
might unfortunately be standing next to an explosive jet
that makes Old Faithful look like a dripping faucet by
comparision....

My question is.....how much is the sky and sun attenuated
by all the gas and dust that makes up the comets coma? Do I
just see a faint haze......or is there so much scattered
light that the "sky" looks like its filled with bright
white clouds....or is so much light scattered and absorbed
that Im digging out my flashlight so I can see where to
walk?....

Of course it obviously depends on the comet....and its
activity level.....

take care

Blll

You forgot to mention whether you're on the day side or the
night side.

Also, I don't believe stuff comes out of those jets at a very
high velocity, based on the expansion of the tails of the few
comets I've seen. It always appears that the body itself is
moving lots faster, unless there's some other reason why the
tail seems to be many times longer than its width.

In message , John
Griffin writes
(BllFs6) wrote:

Hi all....

Was thinking about comets last night and a question occured
to me that I've never seen addressed in the popular
astronomy literature (not to say I've read ALL of it though
...

Okay.....so Im on the surface of a comet.....the surface
might be nice snowy white....or it might be dark as
charcoal.....I might be standing in an area where its
"raining" small particles and gases upwards gently....or I
might unfortunately be standing next to an explosive jet
that makes Old Faithful look like a dripping faucet by
comparision....

My question is.....how much is the sky and sun attenuated
by all the gas and dust that makes up the comets coma? Do I
just see a faint haze......or is there so much scattered
light that the "sky" looks like its filled with bright
white clouds....or is so much light scattered and absorbed
that Im digging out my flashlight so I can see where to
walk?....

Of course it obviously depends on the comet....and its
activity level.....

take care

Blll

You forgot to mention whether you're on the day side or the
night side.

Also, I don't believe stuff comes out of those jets at a very
high velocity, based on the expansion of the tails of the few
comets I've seen. It always appears that the body itself is
moving lots faster, unless there's some other reason why the
tail seems to be many times longer than its width.

Being on the night side isn't going to make much difference unless
you're at local midnight and looking directly away from the Sun, because
there will always be illuminated coma only a few miles away.
In his novel "2061:Odyssey Three" Arthur Clarke assumes that the sky of
Comet Halley will only be faintly luminous - that makes sense, because
the tail you see from Earth is all round you and more spread out - and
that the jets will be like a firehose (which would still blast you off
the surface, as in "Deep Impact").
The people planning ESA's Rosetta probe must have the answers, because
they plan a landing. Is there anything on their web site?
--
Save the Hubble Space Telescope!
Remove spam and invalid from address to reply.

John Griffin wrote:

(BllFs6) wrote:

Hi all....

Was thinking about comets last night and a question occured
to me that I've never seen addressed in the popular
astronomy literature (not to say I've read ALL of it though
...

Okay.....so Im on the surface of a comet.....the surface
might be nice snowy white....or it might be dark as
charcoal.....I might be standing in an area where its
"raining" small particles and gases upwards gently....or I
might unfortunately be standing next to an explosive jet
that makes Old Faithful look like a dripping faucet by
comparision....

My question is.....how much is the sky and sun attenuated
by all the gas and dust that makes up the comets coma? Do I
just see a faint haze......or is there so much scattered
light that the "sky" looks like its filled with bright
white clouds....or is so much light scattered and absorbed
that Im digging out my flashlight so I can see where to
walk?....

Of course it obviously depends on the comet....and its
activity level.....

take care

Blll

You forgot to mention whether you're on the day side or the
night side.

Also, I don't believe stuff comes out of those jets at a very
high velocity, based on the expansion of the tails of the few
comets I've seen. It always appears that the body itself is
moving lots faster,

the body is "moving faster" relative to what?
relative to the stuff that makes up the tail?
isn't that the same thing as saying that the stuff does in fact move
fast relative to the comet body - iow, stuff does come out of those
jets at fairly high velocity?

db

db wrote:

John Griffin wrote:

(BllFs6) wrote:

Hi all....

Was thinking about comets last night and a question
occured to me that I've never seen addressed in the
popular astronomy literature (not to say I've read ALL
of it though
...

Okay.....so Im on the surface of a comet.....the surface
might be nice snowy white....or it might be dark as
charcoal.....I might be standing in an area where its
"raining" small particles and gases upwards gently....or
I might unfortunately be standing next to an explosive
jet that makes Old Faithful look like a dripping faucet
by comparision....

My question is.....how much is the sky and sun
attenuated by all the gas and dust that makes up the
comets coma? Do I just see a faint haze......or is there
so much scattered light that the "sky" looks like its
filled with bright white clouds....or is so much light
scattered and absorbed that Im digging out my flashlight
so I can see where to walk?....

Of course it obviously depends on the comet....and its
activity level.....

take care

Blll

You forgot to mention whether you're on the day side or
the night side.

Also, I don't believe stuff comes out of those jets at a
very high velocity, based on the expansion of the tails of
the few comets I've seen. It always appears that the body
itself is moving lots faster,

the body is "moving faster" relative to what?
relative to the stuff that makes up the tail?
isn't that the same thing as saying that the stuff does in
fact move fast relative to the comet body - iow, stuff does
come out of those jets at fairly high velocity?

The visible tail (not referring to the ion tail), seems to be
ten times longer than its widest point. That leads me to
believe that the comet itself moved ten times as far as the
ejecta in the time since the widest part was ejected. I don't
know how fast the comet I remember best was moving relative to
the sun at the time I'm thinking of. If it was going 30 miles
per second at the time and my impression based on the
length/width ratio is correct, the other stuff might have been
moving only three miles per sec...uhh, damn, now that you
mention it, that would scorch yer ass, wouldn't it?!




db