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CeeBee
July 16th 03, 08:16 PM
(G=EMC^2 Glazier) wrote


> Well that would make 4 solid planets,and 4 gas planets. Well the 4
> closest to the sun are rocky,and small.(why) The 4 outer planets are
> made of gas and are the outer planets (why) Do birds of a
> feather stick to gather?


http://www.solstation.com/stars/jovians.htm


> Can we say gas planets just did not have
> enough gas to become stars? Did Alpha Centuri come out of the same
> nebular as our sun? If we found a rock or gas planet a LY from the sun
> that had a diameter of 10 thousand miles would we add that planet,or is
> it to far out? Bert
>
>



--
CeeBee


Google CeeBee @ www.geocities.com/ceebee_2

Kevin D. Nyberg
July 17th 03, 02:27 AM
I like Gibor Basri's definition:

"A planet is a spherical non-fusor born in orbit around a fusor."

It has the advantage of being a definition based on
naturally-occurring benchmarks, such as orbit and sufficient mass to
achieve relative sphericity.

Any satellite of a planet would, by that definition, be just that,
despite its size. Anything too small to achieve sphericity would be
some form of planetesimal. It's simple. It's easy.

However, its chief disadvantage is that it dramatically increases the
number of planets in the Solar System to include the larger asteroids
and KBOs.

But I'd prefer that to the Pluto controversy.

kdn

Mike Bandy
July 17th 03, 05:20 AM
On Wed, 16 Jul 2003 09:37:37 -0400 (EDT),
(G=EMC^2 Glazier) wrote:

> Heard that the Rose planetarium demoted Pluto from a planet status

<snip>

Pluto's status as a planet has recently been disparaged in numerous
news articles, but nobody will successfully reclassify Pluto from a
planet. Once a planet, always a planet. However, it certainly can't
be denied that many astronomers feel that a reclassification is
appropriate. As far as I can tell, there are three reasons:

(1) The other outer planets of the Solar System are gas giants. They
have a small, solid core with thick atmospheres of methane, nitrogen
and other gases. In contrast, Pluto is a rocky planet with a thin
atmosphere (of similar gases).

(2) Pluto is very small. It's diameter of 2,274 km is only 65% of
earth's moon and 47% of Mercury, the next smallest planet. A few
decades ago, Pluto was considered to be much larger. Scientists kept
recomputing the size and mass to make it smaller and smaller.
Luckily, it didn't disappear altogether. In 1978, after the discovery
of Charon (Pluto's moon) the planet's size and mass was computed more
accurately.

(3) Pluto has an eccentric, egg-shaped orbit of 248 earth years which
occasionally brings it closer to the sun than Neptune.

Are there any other reasons some scientists believe that a
reclassification should be made? I wonder whether any other objects
in the Kuiper Belt or the Asteroid Belt will be discovered which have
both an atmosphere and a satellite.

--
Mike Bandy

Painius
July 19th 03, 12:22 PM
"Mike Bandy" > wrote...
in message ...
>
> On Wed, 16 Jul 2003 09:37:37 -0400 (EDT),
> (G=EMC^2 Glazier) wrote:
>
> > Heard that the Rose planetarium demoted Pluto from a planet status
>
> <snip>
>
> Pluto's status as a planet has recently been disparaged in numerous
> news articles, but nobody will successfully reclassify Pluto from a
> planet. Once a planet, always a planet. However, it certainly can't
> be denied that many astronomers feel that a reclassification is
> appropriate. As far as I can tell, there are three reasons:
>
> (1) The other outer planets of the Solar System are gas giants. They
> have a small, solid core with thick atmospheres of methane, nitrogen
> and other gases. In contrast, Pluto is a rocky planet with a thin
> atmosphere (of similar gases).
>
> (2) Pluto is very small. It's diameter of 2,274 km is only 65% of
> earth's moon and 47% of Mercury, the next smallest planet. A few
> decades ago, Pluto was considered to be much larger. Scientists kept
> recomputing the size and mass to make it smaller and smaller.
> Luckily, it didn't disappear altogether. In 1978, after the discovery
> of Charon (Pluto's moon) the planet's size and mass was computed more
> accurately.
>
> (3) Pluto has an eccentric, egg-shaped orbit of 248 earth years which
> occasionally brings it closer to the sun than Neptune.
>
> Are there any other reasons some scientists believe that a
> reclassification should be made? I wonder whether any other objects
> in the Kuiper Belt or the Asteroid Belt will be discovered which have
> both an atmosphere and a satellite.
>
> --
> Mike Bandy

'Lo Mike --

The main reason that some scientists want Pluto reclassified is to
make collection and analysis of Kuiper Belt Objects data more
consistent and easy to deal with. Our emotional desire to keep
Pluto as a planet notwithstanding, the object is a comet wannabe,
nothing more. Our study of KBOs will be greatly simplified when
the IAU comes around to a more modern classification of stellar
system objects.

happy days and...
starry starry nights!

--
A smidgeon of fear and a sprinkle of strife
And a whole lotta love till your cold...
Most everyone here wants to live a long life,
Ah! but nobody wants to get old.

Paine Ellsworth

G=EMC^2 Glazier
July 19th 03, 01:28 PM
Hi Painius and Scott Nice informative posts. Astronomers have Pluto
being made like a comet(dirty snow ball.) Could it have a faint tail,if
viewed close up. The tail would be always facing away from the sun (I
think?). We found a ring around Jupiter just recently. I would think
that Saturn"s great ring of rocks and ice came from a very large comet.
Mostly ice because they reflect light so very well. Bert

Odysseus
July 19th 03, 08:32 PM
David Knisely wrote:
>
> NO, Pluto is *not* a comet wannabe. It is *much* larger than any known
> comet (large enough to force its mass into a spherical shape, which is a
> prime factor in one classification scheme for a planet). It is in a
> stable orbit which does not have the extreme eccentricity which most
> cometary orbits do. It is probably a Kuiper Belt object, but it is also
> classed as a planet.

How far from the sun do comets begin to develop 'tails'? If this
distance is only a few AU then Pluto, whose perihelion is at about 30
AU, would never get warm enough, or encounter strong enough solar
winds, to create a coma even if it's made of the right materials.

--Odysseus

Painius
July 20th 03, 03:38 AM
"Odysseus" > wrote...
in message ...
>
> David Knisely wrote:
> >
> > NO, Pluto is *not* a comet wannabe. It is *much* larger than any known
> > comet (large enough to force its mass into a spherical shape, which is a
> > prime factor in one classification scheme for a planet). It is in a
> > stable orbit which does not have the extreme eccentricity which most
> > cometary orbits do. It is probably a Kuiper Belt object, but it is also
> > classed as a planet.
>
> How far from the sun do comets begin to develop 'tails'? If this
> distance is only a few AU then Pluto, whose perihelion is at about 30
> AU, would never get warm enough, or encounter strong enough solar
> winds, to create a coma even if it's made of the right materials.
>
> --Odysseus

Comets must approach the Sun to about the distance of Mars' orbital
path (~1.5 AU) before the Sun's heat is enough for sublimation to
begin and a coma and tail to form. Actually, comets usually have two
or more tails. The main tail is a dust tail formed mostly by radiation
pressure. A second and third tail, ion tails, may form caused by the
solar wind.

http://amazing-space.stsci.edu/resources/explorations/comets/lesson/tails_nf.html

http://www.windows.ucar.edu/tour/link=/comets/perihelion_pass.html&edu=high

happy days and...
starry starry nights!

--
So watch as we go 'round in circles,
Ending back where we began,
And there's only one outcome
For anyone's time--
Each of us getting a tan.

Paine Ellsworth

Painius
July 20th 03, 03:39 AM
<g>

happy days and...
starry starry nights!

--
So watch as we go 'round in circles,
Ending back where we began,
And there's only one outcome
For anyone's time--
Each of us getting a tan.

Paine Ellsworth

"David Knisely" > wrote in message ...
> Panius posted:
>
> > ur emotional desire to keep
> > Pluto as a planet notwithstanding, the object is a comet wannabe,
> > nothing more. Our study of KBOs will be greatly simplified when
> > the IAU comes around to a more modern classification of stellar
> > system objects.
>
> NO, Pluto is *not* a comet wannabe. It is *much* larger than any known
> comet (large enough to force its mass into a spherical shape, which is a
> prime factor in one classification scheme for a planet). It is in a
> stable orbit which does not have the extreme eccentricity which most
> cometary orbits do. It is probably a Kuiper Belt object, but it is also
> classed as a planet.
> --
> David W. Knisely
> Prairie Astronomy Club: http://www.prairieastronomyclub.org
> Hyde Memorial Observatory: http://www.hydeobservatory.info/
>
> **********************************************
> * Attend the 10th Annual NEBRASKA STAR PARTY *
> * July 27-Aug. 1st, 2003, Merritt Reservoir *
> * http://www.NebraskaStarParty.org *
> **********************************************

David Knisely
July 20th 03, 05:54 AM
You posted:

> Comets must approach the Sun to about the distance of Mars' orbital
> path (~1.5 AU) before the Sun's heat is enough for sublimation to
> begin and a coma and tail to form.

Actually, the comae begin to form at almost twice this distance (inside
of 2.8 A.U.). See INTRODUCTION TO PLANETARY GEOLOGY by Billy Glass.
Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 10th Annual NEBRASKA STAR PARTY *
* July 27-Aug. 1st, 2003, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

Tom Kerr
July 20th 03, 08:02 AM
In article >, David Knisely > wrote:
>You posted:
>
>> Comets must approach the Sun to about the distance of Mars' orbital
>> path (~1.5 AU) before the Sun's heat is enough for sublimation to
>> begin and a coma and tail to form.
>
>Actually, the comae begin to form at almost twice this distance (inside
>of 2.8 A.U.). See INTRODUCTION TO PLANETARY GEOLOGY by Billy Glass.
>Clear skies to you.

Although this depends on the amount of volatiles in the comet. For instance,
Hale-Bopp was clearly active (i.e., had a coma and tail) when it was
discovered at ~7 AU, and pre-discovery images showed it had a coma at 13 AU.
This is believed due to volatiles (e.g., CO) trapped in the ice.

Jonathan Silverlight
July 20th 03, 09:04 AM
In message >, Tom Kerr >
writes
>In article >, David Knisely
> wrote:
>>You posted:
>>
>>> Comets must approach the Sun to about the distance of Mars' orbital
>>> path (~1.5 AU) before the Sun's heat is enough for sublimation to
>>> begin and a coma and tail to form.
>>
>>Actually, the comae begin to form at almost twice this distance (inside
>>of 2.8 A.U.). See INTRODUCTION TO PLANETARY GEOLOGY by Billy Glass.
>>Clear skies to you.
>
>Although this depends on the amount of volatiles in the comet. For instance,
>Hale-Bopp was clearly active (i.e., had a coma and tail) when it was
>discovered at ~7 AU, and pre-discovery images showed it had a coma at 13 AU.
>This is believed due to volatiles (e.g., CO) trapped in the ice.

Chiron (asteroid 2060 but arguably a comet) has also been seen to show
outgassing.
--
"Roads in space for rockets to travel....four-dimensional roads, curving with
relativity"
Mail to jsilverlight AT merseia.fsnet.co.uk is welcome.
Or visit Jonathan's Space Site http://www.merseia.fsnet.co.uk

Tom Kerr
July 20th 03, 11:43 AM
In article >, wrote:
>In message >, Tom Kerr >
>writes
>>In article >, David Knisely
> wrote:
>>>You posted:
>>>
>>>> Comets must approach the Sun to about the distance of Mars' orbital
>>>> path (~1.5 AU) before the Sun's heat is enough for sublimation to
>>>> begin and a coma and tail to form.
>>>
>>>Actually, the comae begin to form at almost twice this distance (inside
>>>of 2.8 A.U.). See INTRODUCTION TO PLANETARY GEOLOGY by Billy Glass.
>>>Clear skies to you.
>>
>>Although this depends on the amount of volatiles in the comet. For instance,
>>Hale-Bopp was clearly active (i.e., had a coma and tail) when it was
>>discovered at ~7 AU, and pre-discovery images showed it had a coma at 13 AU.
>>This is believed due to volatiles (e.g., CO) trapped in the ice.
>
>Chiron (asteroid 2060 but arguably a comet) has also been seen to show
>outgassing.

Absolutely, although I'm sure people will argue that Chiron isn't a good
example of a comet. However, I think comet 46P/Wirtanen also became active
beyond 3 AU from the sun (3 AU being the canonical value for comet
activity).

It's clear that the abundance of more volatile species trapped in water ices
will have an effect on cometary activity, but it's only something we can
start to study these days, given the techniques and equipment required to do
this are recent. What's clear from both observations of comets and ices in
the interstellar medium is that volatiles are often abundant and that you
can't use water ice alone to predict cometary activity.

G=EMC^2 Glazier
July 20th 03, 01:18 PM
Hi All Cometary activity(nice term) Did Man copy comets in the way
they sling shot. Does the main ball of the comet spin? I read there is a
comet that swings around the sun every 1500 years. Does this comet come
from the Oort belt? I read in one of these posts the comet has ion type
materials. That means it has a positive charge.The sun's solar wind I
think has positive charged particles(protons) that could make for an
interesting theory,for it could give another reason why comets miss the
sun,and have their tails always facing away from the sun. Coming around
the sun(sling shot) how fast is say "Halley's" comet going? I can see
in about 50 years man making use of comets,even making man made comets.
Bert