The object larger than Pluto (July 31)

Comments and questions about the APOD on the main view screen.
Empeda
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Post by Empeda » Wed Aug 17, 2005 3:41 pm

I found a good reference for the comparative distances/sizes at http://www.nineplanets.org:

Imagine Earth the size of a grape.
The moon would be a foot from the earth.
The sun would be 1.5m in diameter and 150 metres away.
Jupiter would be the size of a large grapefruit and be about 5 city blocks away.
Saturn (an orange!) - 10 blocks.
Uranus and Neptune (lemons) - 20 and 30 blocks.
A Human - the size of an atom.
The nearest star: 40,000 KILOMETERS AWAY.

Vast my friend.... vast..... :shock:
I'm an Astrophysics Graduate from Keele University, England - doesn't mean I know anything but I might be able to help!

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orin stepanek
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Post by orin stepanek » Thu Sep 01, 2005 12:11 am

do you suppose there are objects; (asteroids); in orbit around two stars??? I don't know much about astronomy but is seems possible.
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makc
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Post by makc » Thu Sep 01, 2005 6:04 am

Perhaps you've missed it, but there are planets in orbit around three stars.

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orin stepanek
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Post by orin stepanek » Thu Sep 01, 2005 1:29 pm

I was thinking about stars that may be few light years apart. There must be planets out there that may be so far out that they could be caught in orbit around two stars. The large planet in the three star system seems to be more logical for a three star orbit.
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makc
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Post by makc » Thu Sep 01, 2005 3:13 pm

orin stepanek wrote:There must be planets out there that may be so far out that they could be caught in orbit around two stars.
Huh, there you go. Leaving natural question (how could it get SO far out) aside, why do you think there would be such thing as an orbit, in that case? Why an object "caught" in that way can't be later "released", or "hi-jaked" by another star?

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orin stepanek
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Post by orin stepanek » Thu Sep 01, 2005 3:39 pm

I can see that it could be captured by another star.
Orin

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BMAONE23
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Post by BMAONE23 » Thu Sep 01, 2005 7:17 pm

Empeda wrote:I found a good reference for the comparative distances/sizes at http://www.nineplanets.org:

Imagine Earth the size of a grape.
The moon would be a foot from the earth.
The sun would be 1.5m in diameter and 150 metres away.
Jupiter would be the size of a large grapefruit and be about 5 city blocks away.
Saturn (an orange!) - 10 blocks.
Uranus and Neptune (lemons) - 20 and 30 blocks.
A Human - the size of an atom.
The nearest star: 40,000 KILOMETERS AWAY.

Vast my friend.... vast..... :shock:
This is another way to put it
Speed of light travel and the distance of space

If you could walk at the speed of light, this would be how fast you could travel.
Start at a point on the ground which will represent the center of the sun and mark it, then walk at your regular pace. If you walk for 2.3 seconds, you will reach the outside of the sun. Mark that spot and continue. All distances will be given as time from this point.
Continue walking from the sun for 3 minutes and you reach Mercury, 6 minutes and you reach Venus, 8 ½ minutes to get to Earth (look back to your starting point can you still see it?). 11 minutes from the sun you’ll find Mars. 46 minutes from the sun and you get to Jupiter. 1 hour and 16 minutes from the sun and you arrive at Saturn. 2 hours and 43 minutes from the sun you will find Uranus. 4 hours and 13 minutes of walking will get you to Neptune. 6 hours (360 minutes) of walking will get you to Pluto. How far can you walk in 6 hours? To get to our nearest star, you will have to walk, non stop, for over 4 years. That’s far.

makc
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Post by makc » Fri Sep 02, 2005 6:05 am

BMAONE23 wrote:look back to your starting point can you still see it?
sure I can, because its lighting is right behind me :)

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orin stepanek
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Post by orin stepanek » Fri Sep 02, 2005 1:38 pm

If you were in a car going 60 miles an hour; and compared that to the speed of light. That would make Earth 8 1/2 miles back. How far can you drive in over four years non stop? So my wayward planet would be lost is space for a long time. Still I believe in the possibility.
Orin

Empeda
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Post by Empeda » Fri Sep 02, 2005 3:39 pm

I think it's certainly possible - anything is.....but an object that far away would be incredibly unlikely to be orbiting a star, or be stuck in the middle of two. The proper motions of the two stars would have to be pretty close I would have thought, and the tiny gravitational force at that kind of distance would be open to many weak fluctuations.

Still, never write anything off..... :shock:
I'm an Astrophysics Graduate from Keele University, England - doesn't mean I know anything but I might be able to help!

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Post by Aqua » Tue Oct 04, 2005 1:07 am

2003 UB313's peculiar orbit and other KBO's with similarly odd orbits may prove them to be 'captured' interstellar objects? Close encounter(s) with another star, or brown dwarf, where the lesser body's gravity looses influence over its orbitals. Cassini is showing us frozen water worlds and evidence of ongoing 'brown dwarf'-like neucleosynthesis within Saturn. Could Saturn be a captured 'brown dwarf'? That would go a long way into explaining what happened to Uranus? Where Jupiter got its water moons, and how Venus was resurfaced? Or even why Phobos appears to be part of MUCH larger body? There are more answers than questions.. right?

Empeda
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Post by Empeda » Tue Oct 04, 2005 11:14 am

Åqua wrote:Could Saturn be a captured 'brown dwarf'? T
Yep - the more we discover the less we know... :x

Saturn isn't likely to be captured as it orbits along the same plane as the rest of the planets, suggesting that it was formed in an accretion process.
I'm an Astrophysics Graduate from Keele University, England - doesn't mean I know anything but I might be able to help!

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Post by Aqua » Wed Oct 05, 2005 9:10 pm

Saturn's rings and equator are inclined by 27° while its Inclination to the Solar Ecliptic is 2°29'17". Only Mercury, Venus and Pluto have higher inclinations to the solar ecliptic. Add 27° with 2°29'17" and you get an even higher angular inclination of almost 30°! Uranus' equator is inclined a whopping 97.86°, while Venus' inclination of Equator to Orbit is 177.3°! Tell me again how these orbital eccentricities originated.... why not speculate?

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Re: Illusional Illustrations

Post by Zaha » Thu Oct 06, 2005 5:06 pm

papiamento wrote:No it's not just you (well... maybe, it could be).

Actually, I think APOD sometimes does a disservice with illustrations.

Objects that distant (100 AU) are just not going to be that well lit.
In fact, I think they would. At 100AU from Sun, the planet receives 1/10000 of the sunlight intensity Earth does. By comparison, the Sun's apparent magnitude on Earth is -26.7 and full Moon's -12.6, therefore we have by the definition of magnitude that Sun is 100^(26.7-12.6)/5) = 437000 times as bright as the full Moon. So an object at 100AU is 43.7 times brighter than Earth in full Moon's light, and as humans can see quite well (even colors) in good direct moonlight they would see the object fairly well lit with eyes adapted to dark.

With long enough exposures, it might even be possible to photograph the dark side in just starlight (even better if the object is illuminated by its own moon too) - though not in the same picture with the sunlit side.

makc
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Post by makc » Thu Oct 06, 2005 6:57 pm

Thank you, Zaha, I've almost forgot what this thread originally was about.