How big is the solar system

[Bombus Bombus]

Hi,whist pondering i could not get my head around how small our solar system is in terms of fractions of a light year.I know sun to pluto is 3.5 billion miles roughly and i think one light year is 6 trillion miles which makes our solar system a fraction of one percent lightyear i think.Bring in these oort clouds i just read about apparently one light year away(how can they possibly be part of our solar system)The mind boggles.After all this i reckon the solar system is about 0.5% of one light year.Am i correct or should i stick to birds.Bombus Bombus.

[carlos_dfc]

Hi Bombus (x2)

Miles are too small an increment to use when thinking of something the size of the Solar System. The AU (Astronomical Unit) is a much better measuring stick.
An AU is the average distance from the Earth to the Sun - about 93 million miles, or 150 million km.
A light-year is about 6,240 AUs

Pluto's distance from the Sun varies between about 29.5 AU, and 50 AU - which puts it smack in the realm of the Kuiper belt.
The Kuiper belt is similar to the Asteroid belt, except that it stretches from around Neptune's orbit (30 AU) out to about 55 AU - and Kuiper belt objects (KBOs) are mainly icy, whereas the ateroids are mainly rocky.
Pluto is basically a large KBO (and it isn't even the biggest one) - When Pluto was discovered, nobody knew there was such a thing as the Kuiper belt - so it was wrongly designated as a planet - If it had been discovered recently, it would straight away have been designated 'KBO'

The Oort cloud is a sphere of mainly icy material which streches roughly from the edge of the Kuiper belt (55 AU), out to a distance of about 50,000 AU (about 5/6 of a light-year)

So - the bulk of the solar system (Sun, planets, asteroids, and Kuiper belt) only stretches out to about 1/1000th of a light-year (0.1%) with only the Oort cloud going out further.

As an idea of scale.....
If the Sun was the size of a tennis ball, then if you took 5 tennis balls, and spread them randomly inside a sphere the size of the Earth - you'd have a good approximation of the density of stars in our part of the galaxy.

[thunder]

Originally Posted by carlos_dfc

As an idea of scale.....
If the Sun was the size of a tennis ball, then if you took 5 tennis balls, and spread them randomly inside a sphere the size of the Earth - you'd have a good approximation of the density of stars in our part of the galaxy.

And Sir James Jeans said (or wrote!) Empty Waterloo Station of everything except six specks of dust, and it is still far more crowded with dust than space is with stars.

henrya

[Deer Hunter]

I always think you would go mad thinking about this. I just can't bring my mind to think just how big it is.

[nebucadnezzer]

What blows my mind is:-
Assuming you didn't bump into anything and you travelled
in a straight line. You would travel for eternity.
What I can come to terms with is travelling for hundred years
at the speed of light and then hitting a brick wall!!!! In
the same direction, of course.

Kindest regards,
Ian.

[jnb]

The problem with anything in astronomy is that the numbers are so vast that it's almost meaningless to try to 'comprehend' them. Calculate with them by all means but most people have difficulty comprehending anything above seven items at a time so suddenly throwing in scales of billions is only really useful to get the 'wow that's big' kind of response

I think Douglas Adams has the best description ...

[thunder]

Originally Posted by jnb

I think Douglas Adams has the best description ...

What about Terry Pratchett's "space contains everything and nothing, but there is very little everything and more nothing than you can possibly imagine" (or something like that - from memory)

I've always thought that was exceptionally good.

henrya

[nebucadnezzer]

Originally Posted by thunder

What about Terry Pratchett's "space contains everything and nothing, but there is very little everything and more nothing than you can possibly imagine" (or something like that - from memory)

I've always thought that was exceptionally good.

henrya

Sounds like a 'SECRETARY RUMPSFELT' to me!!!

(please excuse the spelling but you know who I mean.)

Kind regard,
young Ian.

[Amiguru]

I obtained a free copy of a space simulator called Deep Space Explorer last year on a PC magazine cover disk. It is a wonderful program allowing you to pilot your way around the universe visiting 28,000 galaxies and their stars! You can zoom from the Earth all the way out to the limits of the universe, i.e The Big Bang, in seconds. That will give you a sense of how insignificant our galaxy, The Milky Way, is, let alone our solar system. It's awe inspiring especially when used on a big screen

[Strontium]

Hi, just wanted to ask a question since there's loads of info spinning about in an empty universe,

Originally Posted by carlos_dfc

The Oort cloud is a sphere of mainly icy material which streches roughly from the edge of the Kuiper belt (55 AU), out to a distance of about 50,000 AU (about 5/6 of a light-year)

If the Oort cloud is spherically symmetrical about the sun, does that mean that it did not take part in the rotational alignment of the planets etc, when the planets started to form and the kinetics settled a bit? And if it did, does this mean that loads of ice formed after the the stability apeared and became unconnected to the inner solar system, and alot of water could have been present in an earlier state of the solar system that subsequently boiled off into deep space since the gravitational force is so weak?