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  #1  
Old 06-25-2003, 08:39 PM
sonicsink sonicsink is offline
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Moving "stars" in the sky at night,what could they be?

Last night hubby and I were out on the roof star gazing when suddenly we saw movement.There was this object that looked exactly like a star except it was moving pretty quickly from approx. north east to south east. As we were watching it, another "star" that was not as bright moved under it passing from approx. south east to north. After about 1/2 hour we spotted yet another "star" moving from approx. south east to east about as bright as the first. Now at first we though it was a plane,but it was moving too fast across the sky and it was just a bright white light,we checked it out with binoculars and there were no blinking lights typical of an airplane and this was a very bright white light. Then we thought it could be satelites,but do they move and where would the bright white light come from?Reflection of the sun? Why was the second "star" not as bright then? Obviously we don't know too much about this stuff so any insite would be appreciated!
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  #2  
Old 06-25-2003, 08:44 PM
hibernicus hibernicus is offline
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Most likely from your description the brighter object was the International Space Station.

The light is reflected sunlight, and the ISS stays visible for typically a couple of minutes until it enters the earth's shadow and winks out reasonably suddenly.

I don't know what the less bright south to north moving object was - an aircraft maybe?
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  #3  
Old 06-25-2003, 08:48 PM
Blake Blake is offline
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Sattelites of some sort. Whether one was the ISS or not I couldn't say. They aren't exactly rare these days.
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Old 06-25-2003, 08:48 PM
bernse bernse is offline
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The ISS wouldn't go in the direction the OP mentioned.

Probably just a sattelite of some sort. There is gazzilions up there. Wait until you see an Iridium flare. They can be incredibly bright if you're at the right place at the right time.

Here is a website for you to track visible sattelites:

http://www.heavens-above.com/
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  #5  
Old 06-25-2003, 08:50 PM
bernse bernse is offline
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Of course, I seem to have great difficulty spelling the words "satellite"

Oh well.

I hope I got it right that time!
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  #6  
Old 06-25-2003, 08:50 PM
Stupendous man Stupendous man is offline
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There are all sorts of satellites that are visible when the sky grows dark after sundown. In a park a few weeks ago we saw several withing a few minutes.
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Old 06-25-2003, 09:59 PM
KarlGauss KarlGauss is offline
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Just to add that by and large you'll see more satellite action in the first hour or so after sunset. This happens because although the Earth is already in darkness, the satellites are still high enough to catch some sunlight. As the night progresses, only the highest orbiting satellites still remain "uneclipsed".
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  #8  
Old 06-25-2003, 10:14 PM
Musicat Musicat is offline
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Satellite Schedules.

Put in your geo coords and get a list of what you can see.

Around dawn & sunset, when the sun is below your horizon, many satellites are still in sunlight and they show up well in the darkened sky.

I haven't done this recently, but we used to print out a schedule for our area, then go down to the beach where the sky is unobstructed, with an accurate clock, and watch the satellites go by. Better than submarines.
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Old 06-26-2003, 12:53 AM
rjk rjk is offline
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A possibly related question: What about lights that don't move? Last month on several nights I saw what seemed to be a small cluster of lights in the western sky shortly after sunset. They seemed to be in about the same place, (maybe 20 degrees behind the sun, or a little more) every time I saw them. The airport flight path is in the same direction, but these didn't move like a plane does.

Any thoughts?
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  #10  
Old 06-26-2003, 12:56 AM
bernse bernse is offline
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Pleiades?
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  #11  
Old 06-26-2003, 01:05 AM
Trigonal Planar Trigonal Planar is offline
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Nah, pleiades wouldn't be moving across the sky.


These answers are too logical. Obviously it was a UFO.
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  #12  
Old 06-26-2003, 01:08 AM
commasense commasense is online now
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Bernse mentioned the Iridium flares in passing. There are 66 Iridium satellites in low earth orbit and when the angle of the sun is right (usually around local sunrise or sunset), their antennas create a really brilliant reflection that appears suddenly, is visible for a few seconds, and then just as quickly vanishes.

It is an almost magical thing to see, and you can often catch three or four within an hour. All you need is cloud-free sky, a clear horizon, an accurate watch, and the ability to determine the compass direction and angle above the horizon within about 20 degrees. (It's easy!)

Let me urge Dopers to visit the Heaven's Above Web site Bernse linked to, and look for a flare today. They are just soooooo cool, you'll be dragging your friends out to see them.
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Old 06-26-2003, 01:18 AM
Trigonal Planar Trigonal Planar is offline
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Wow, that is a very cool site

Thanks for that link.
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  #14  
Old 06-26-2003, 02:01 AM
Coriolanus Coriolanus is online now
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Quote:
Originally posted by rjk
A possibly related question: What about lights that don't move? Last month on several nights I saw what seemed to be a small cluster of lights in the western sky shortly after sunset. They seemed to be in about the same place, (maybe 20 degrees behind the sun, or a little more) every time I saw them. The airport flight path is in the same direction, but these didn't move like a plane does.

Any thoughts?
Very likely you're seeing planes in an oval holding pattern. I've seen much the same thing from Jones Beach, LI -- planes circling (ovaling?) JFK looking like slow-moving fireflies.

I've noticed the Iridium sattelites often come in bunches, from the same direction, which makes sense as the lot of them comprise a network.
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Old 06-26-2003, 09:40 AM
bernse bernse is offline
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Quote:
Originally posted by Trigonal Planar
Nah, pleiades wouldn't be moving across the sky.
Well duh.

I wasn't answering the OP. I was answering the question immediately before that post:
Quote:
A possibly related question: What about lights that don't move?
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  #16  
Old 06-26-2003, 10:46 AM
Philster Philster is offline
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Sattelites: some are stanionary by design and stay put above the sky (like my Direct TV sattelite), and some don't have geo stationary orbits and move across the sky.

sound right?
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  #17  
Old 06-26-2003, 10:55 AM
Bruce_Daddy Bruce_Daddy is offline
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http://www.heavens-above.com/ has my neighborhood!!!
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  #18  
Old 06-26-2003, 11:07 AM
commasense commasense is online now
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I don't believe that any geostationary satellites are visible to the naked eye. They are at least 100 times farther from us than LEO satellites, and therefore would be only 1/10,000th as bright, all other things being equal.
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  #19  
Old 06-26-2003, 11:12 AM
buckgully buckgully is offline
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Yes, there are satellites that have such high orbits that they appear to not move in relation to the ground. That's called a "geostationary" orbit. Any satellite TV sat, or anything you don't need to move an antenna to keep track of is in a geostationary orbit. However, I don't think there are any geostationary satellites that are visible to the naked eye.

Satellites you can see are in low earth orbit (LEO). For example, Iridium satellites are only around 300 miles away when they're directly overhead. Most of the other ones are between 250-350 miles out. Geostationary satellites sit out in a band that's more than 21,000 miles away.

A great site to see the orbits of satellites is J-track 3d. http://liftoff.msfc.nasa.gov/realtim.../JTrack3D.html

You see the swarm of satellites in LEO clustered around the earth, then a few oddballs here and there in medium earth orbit, and then a ring of satellites out in the geostationary/geosyncronous orbits.
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  #20  
Old 06-26-2003, 02:40 PM
CurtC CurtC is offline
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Quote:
Karl Gauss wrote:
Just to add that by and large you'll see more satellite action in the first hour or so after sunset.
This varies based on latitude and time of year, but in the northern hemisphere and this time of year, satellites are visible for *much* longer after sunset than in the winter. That's because with the north pole pointed towards the sun, when you're in the shadow, an object doesn't have to be as high to still be in sunlight. In the middle of winter is when things disappear into Earth's shadow within an hour of sunset. But it's quite easy to see satellites in June at 11 pm or later, and that's here at just 33 degrees latitude. You northerners would probably be able to see them all night long.
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  #21  
Old 06-26-2003, 03:34 PM
bernse bernse is offline
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Quote:
Originally posted by commasense
I don't believe that any geostationary satellites are visible to the naked eye. They are at least 100 times farther from us than LEO satellites, and therefore would be only 1/10,000th as bright, all other things being equal.
True, and even if you could see them I don't know how you would know it was a satellite compared to a star as it wouldn't move.
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  #22  
Old 06-26-2003, 04:02 PM
eburacum45 eburacum45 is online now
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At night, a 200 metre geostationary satellite would be clearly visible;
there aren't any,
but they could be built (or perhaps inflated) if there was any need for them.
Such a satellite would not move, of course, but the rest of the sky would move past it-
and this relative motion would be clearly visible in binoculars.
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  #23  
Old 06-26-2003, 04:18 PM
Yeticus Rex Yeticus Rex is offline
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If you want to really freak your friends out....there are the "NOSS" satelites (National Oceanic Surveillence System) that orbit the Earth in groups of three that form a triangle moving amongst the stars. You do need to use binoculars though, they are faint (Mag ~5.2 - 9.0+) depending on your location and sun's reflection. There are 3 sets of these NOSS triplets, labeled:

Noss 2-1 B
Noss 2-1 C
Noss 2-1 D

Noss 2-2 C
Noss 2-2 D
Noss 2-2 E

Noss 2-3 C
Noss 2-3 D
Noss 2-3 E

Take an ignorant friend (everybody has at least one!) and after you find the orbital elements and are familiar with the night sky, take this friend out to just look at the stars and satelites with your binoculars. *Accidentally* find these satelites (or are they UFOs?) flying in a pattern and then let the friend see it and let them run with it for a while. Very entertaining evening indeed!

I found these satelites by accident when I was looking at the Big Dipper last year and a shiver ran through my spine when I saw these 3 "stars" move together in triangular formation. After searching Google (which lead me to the Heavens Above site), I found out that they are satelites designed to locate (by triangulation) and eavesdrop on ships in the ocean, and possibly land targets as well.

Can't link it to Heavens Above, you have to be a registered user (which is easy to do). Go to the "Select" a satelite from the database and type in "%NOSS%" on the third field to get all the NOSS satelites listed. Pick one of the satelites (use the 2-2 or the 2-3 groups, 2-1 won't be listed) I listed above and then click on the "passes" to get all the info you need.

The site is also great for finding the best Iridium Flares for your location.....very cool site.
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  #24  
Old 06-26-2003, 04:20 PM
Yeticus Rex Yeticus Rex is offline
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Argh....National = Nautical for "NOSS"
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  #25  
Old 06-26-2003, 04:21 PM
Yeticus Rex Yeticus Rex is offline
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Dammit! Nautical = Navy for "NOSS"....
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