saturn with the naked eye

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saturn with the naked eye

Postby thebest » Sun Jul 04, 2010 3:46 pm

If we could see the Saturn the same distance as the moon from the earth, then how big would it look in the sky?
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RE: saturn with the naked eye

Postby tddun » Sun Jul 04, 2010 3:46 pm

At a guess I would say that it would fill most of the sky, and depending on it's position then the rings would be in constant view day and night. With the light coming off Saturn as well I would say maybe no stars would ever be visible but I'm sure someone else has a more accurate answer.
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RE: saturn with the naked eye

Postby sftonkin » Sun Jul 04, 2010 5:26 pm


[quote]ORIGINAL: thebest

If we could see the Saturn the same distance as the moon from the earth, then how big would it look in the sky?
[/quote]

[color=#FF0000]<back_of_envelope>[/color]
Saturn's diameter (disc) is approx 120,000 km
Moon's diameter is approx 3500km
So Saturn is about 34x the diameter of the Moon,
The Moon is approx 0.5 deg across
Ergo Saturn's disc would be approx 17 degrees of arc across.
[color=#FF0000]</back_of_envelope>[/color]
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RE: saturn with the naked eye

Postby thebest » Sun Jul 04, 2010 6:33 pm

so it would be quite a view i imagine? thanks!
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RE: saturn with the naked eye

Postby lancashire astroguy » Sun Jul 04, 2010 7:56 pm

Let me put my astrophysicist hat on for a back-of-envelope calculation:

As it would be 4,000 times closer, it would appear 16,000,000 times brighter in the sky as it does currently. In fact, sunlight is 100 times more intense near Earth so it would actually appear 1,600,000,000 times brighter!

On the magnitude scale of brightness which puts faint stars at +6.0, bright stars at +1.0 and the full moon at -12.7, Saturn is typically magnitude -0.2. However, if it was 1.6 billion times brighter, this would be 23 magnitudes difference. The magnitude of Saturn would be -23.2 or thereabouts. That is the equivalent of over 10,000 full moons in the sky.

In other words, it would look flippin spectacular. It would ruin night-time astronomy though! [:o]

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RE: saturn with the naked eye

Postby sftonkin » Sun Jul 04, 2010 8:13 pm

Er, James, I think you need to remember that it's an extended object and hence the surface brightness would not be equivalent to mag -23-ish.

More astrofizz hat stuff -- if it was that close to us, we would be its moon. Fortunately, we would be beyond its rings, otherwise we would have a periodic bombardment of ring particles.... CBA (too many stiff bloody-marys) to work out what our period of revolution would be, but it would be, but it would be considerably less than a month over which we would cycle through the complete period of ring-changes that now takes nearly 30 years. Also, if it was that close to us (an hence the Sun), Titan would have terrestrial-type temperatures; now that would be an interesting evolutionary laboratory!
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RE: saturn with the naked eye

Postby thebest » Sun Jul 04, 2010 11:00 pm

how interesting.. regarding implications, i should really think about what i wish for..i might just.... good job i don't have a genie lamp..always do your research first. [;)]
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RE: saturn with the naked eye

Postby les » Mon Jul 05, 2010 12:56 am

HI Thebestl,
Being a absulute thicko at maths no backs of envelopes for me.I simply 'went' to Dione (which is approximatly the Earth-Moon distance)using the trusty old Starry Night Backyard and got the information in seconds without eating a pencil.[:D] From Dione Saturn would be 18 degrees across and have a magnitude of -16.8.
Regards Les.
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RE: saturn with the naked eye

Postby lancashire astroguy » Mon Jul 05, 2010 1:30 am

Les,

Don't forget though that Saturn would be dimmer from Dione because at that distance from the Sun, there is only 1% of the sunlight to reflect off Saturn and its rings as there would be at Earth's distance from the Sun. Its a little known fact that the Earth viewed from Saturn is almost as bright as Saturn viewed from the Earth!

Going back to what you were saying about us being Saturn's moon if it was that close, I can't help thinking that such systems might be common amongst extrasolar planets. Perhaps even more common than terrestrial planets in temperate orbits. I guess you haven't seen the movie Avatar (I know you hate TV so I'm guessing your not keen on movies either!) but it is set on a habitable moon orbiting a Jupiter-type planet around Alpha Centauri A. The only thing that would concern me about the habitability of such worlds is the high-energy particles from the Van Allen belts of the parent planets. Surely this would frazzle any surface life?

Regards,
James
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RE: saturn with the naked eye

Postby philip pugh » Mon Jul 05, 2010 1:46 am

I've thought that life on a Moon orbiting a gas giant may well be possible, even in our own solar system.

I'd have thought that anything orbiting Alpha Centauri A or B the size of Jupiter would have been detected by now.
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