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Old 07-16-2002, 09:21 PM
Moe Moe is offline
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Quick question: Is Saturn visible to me right now?

I am pretty sure it isn't but my father seems to believe that a particular speck of light in the sky at the moment is Saturn, or another planet.

It is white, fairly bright, and flickering which leads me to believe it is a satellite.

If Saturn was visible, wouldn't it be red because of the red shift, fairly dull, and constant?

Last edited by bibliophage; 07-16-2002 at 11:56 PM.
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Old 07-16-2002, 09:26 PM
Moe Moe is offline
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Sheesh Moe! It wasn't like this has been among your longer posts. Maybe 8.6 seconds max to proofread?

If a Mod happens to read this, would that mod be kind enough to edit the really dumb-sounding redundancy in the subject line please?
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Old 07-16-2002, 09:29 PM
pldennison pldennison is offline
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If you're looking to the west, it's Venus. It's visible from your location nearly due west, and about 15 degrees off the horizon. It's a very, very bright white -- the brightest object in the sky at the moment. Saturn is not currently visible in the Northern Hemisphere.

BTW, the red shift wouldn't have anything to do with it. Red shift describes the appearance of light from objects that are moving away from the Earth at rapid speed.
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Old 07-16-2002, 09:46 PM
Punoqllads Punoqllads is online now
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No, you can't see Saturn right now because you're looking at a computer screen.

But if you were looking up in the sky, that's a different story. First of all, there's no red shift, because red shift only happens when viewing objects moving away from you at a speed that's a significant fraction of the speed of light.

Also, the flickering you see is due to the light passing through the atmosphere, which has high and low density areas that are constantly shifting, bending light slightly this way and that. If you were looking at Saturn, you'd see it twinkle.

However, according to The Griffith Observatory you'd see Saturn to the east-northeast a bit before 5am your time. By their numbers, you should see it rise around 4:30am right about now.

So, unless you're posting from, what, Moscow? Tehran? you're not looking at Saturn.
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Old 07-16-2002, 10:56 PM
Moe Moe is offline
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OK, so I was completely off here.
But a friend brings up a couple of questions:

Why is the light white? Is Venus white at its surface? Where is the light coming from? (I can only assume the sun or perhaps other stars).

And I guess I didn't understand the concept of the "red shift". I thought that it is due to the differences in speed of light at different wavelengths, and thus a planet as far away as Venus (or Saturn as I originally supposed) reflecting white light, would appear to be a different color by the time the light got here.

After a moments reflection, I realized that if my logic was not flawed the light from every star in the sky would undergo the same treatment on its way here.

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Old 07-16-2002, 11:16 PM
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Venus is white because of the reflection of the sun off of its thick cloud layer, which is white (or whitish-yellow).

Yes, you can see Saturn with the naked eye pretty easily, if you're in a dark area and know where/when to look.

All wavelengths of light travel at the same speed. Red shift is the same effect as when an ambulance siren goes past you. The pitch seems higher as it approaches, then lower once it passes. Red shift isn't a factor for planets, since they're never receding from or approaching the earth at any great speed. But for stars, it can make a large difference.
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Old 07-16-2002, 11:22 PM
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KarlGauss KarlGauss is offline
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Quote:
Originally posted by Punoqllads
Also, the flickering you see is due to the light passing through the atmosphere, which has high and low density areas that are constantly shifting, bending light slightly this way and that. If you were looking at Saturn, you'd see it twinkle.
[nitpick]

Generally, a good test for determining if that point of light you're seeing is a planet, is whether or not it twinkles. Planets don't twinkle, stars do.

Stars are so distant that their light is essentially point-like. So, if there's any atmospheric turbulence (and there almost always is at least a bit), such a point of light will be distorted. Planets, on the other hand, are close enough so that their light seems to be coming from a small area. Such an area is often larger than the size of the turbulent cells in the atmosphere so it doesn't get distorted and hence doesn't twinkle.

[nitpick]
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Old 07-16-2002, 11:55 PM
bibliophage bibliophage is offline
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Quote:
Originally posted by Moe
Sheesh Moe! It wasn't like this has been among your longer posts. Maybe 8.6 seconds max to proofread?

If a Mod happens to read this, would that mod be kind enough to edit the really dumb-sounding redundancy in the subject line please?
Done.
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Old 07-17-2002, 01:50 AM
Coriolanus Coriolanus is offline
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Sheesh Moe!
sounded like a fun thing to say

http://space.jpl.nasa.gov/cgi-bin/ws...orbs=1&brite=1

That's a fantastic site.

Next up: Ask Santa for a good set of binoculars. Then Jupiter (the most impressive planet) will look like this:

http://space.jpl.nasa.gov/cgi-bin/ws...bfov=5&porbs=1

Galileo sketched them like this:

http://www.hao.ucar.edu/public/educa...galileo.4.html
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Old 07-17-2002, 05:00 PM
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Quote:
It is white, fairly bright, and flickering which leads me to believe it is a satellite.
Satellites are generally rather faint (although they can have bright "flares", when the sunlight reflects off them at just the right angle), and they'll move across the sky at a very noticeable rate. Most of the easily-visible satellites are in polar orbits, so they'll move from north to south or south to north across the sky.

Venus is most often seen in the evening sky (no more than three hours after sunset), in the west (it can also be seen in the east, before dawn, at times, but fewer folk are up to see it then). It's the third-brightest thing in the sky, after only the Sun and Moon, and it's about the brightness of a very bright airplane flying at you. The easiest way to tell the difference is that Venus won't appear to move relative to the stars, at least not at a rate detectable to the naked eye.

The rest of the visible planets are all fainter than Venus, but still very bright compared to most stars. Mercury is even closer to the Sun than Venus, so there's less time to view it, and more glare, but Mars, Jupiter, and Saturn can potentially be seen at any time of night, depending on where they are in their orbits.
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Old 07-17-2002, 06:01 PM
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Quote:
Originally posted by Chronos:
Satellites are generally rather faint (although they can have bright "flares", when the sunlight reflects off them at just the right angle)
Have you seen the ISS ? In some passes itís brighter than Sirius ! It doesnít flicker much though. See Heavens-above to get magnitude and visibility predictions for all the brighter satellites.
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Old 07-17-2002, 06:08 PM
JS Princeton JS Princeton is offline
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Note about color: it is subjective. White means basically means at that moment in time you are overwhelmed by the number of photons per projected area. It is not a color like red or green or blue is. Likewise black means at that moment in time you are underwhelmed by the number of photons per projected area.

Stars appear white mostly because the sky is dark, but you can also see colors because often times they emit (in the case of stars) or reflect (in the case of planets) light at varying intensity at different wavelengths. Thus the redness of Mars or Arcturus.
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