Is it a bird? Is it a plane?

June 11, 2006 3:39 AM

Is it a bird? Is it a plane? I'm lying on the grass staring at the summer stars. I see a star that's moving slowly but steadily - if I stretch my hand right out in front, it crosses my palm in about 30 seconds. Using only common-sense, how can I work out what it is?

I see these moving stars often and always wonder what they are. I associate aeroplanes with flashing lights - that might be my first mistake. Meteors tend to look as if they are burning and move much faster. So I guess that they are man-made satellites. Is that right and can I equip myself with a little extra knowledge to have a fair stab at guessing (given the time, my location and the compass points - but no other resources) what kind of satellites they are?

posted by grahamwell to science & nature (13 comments total)

Satellite. Not a TV satellite, though; those are geosynchronous. You can try J-Track (it seems to require Java.) Or this.
posted by Kirth Gerson at 3:49 AM on June 11, 2006

It's a satellite. Check out the Visual Satellite Observer's page for more.
posted by richmondparker at 3:49 AM on June 11, 2006

Assuming your palm is 4 inches and your arm is 2 feet long, it's either doing 550mph at 96,000 ft (far too high), or 227 mph at 40,000 ft (a bit slow). So I'm guessing not a plane.

(That's just using basic ratios and speed = distance/time)
posted by cillit bang at 3:55 AM on June 11, 2006

And if you see a moving object with a slow blink it's probably space junk.
posted by cropshy at 5:20 AM on June 11, 2006

Congratulations on witnessing a satellite!

A great site to track these sorts of things is Heavens Above. You'd be surprised just how many of these satellites you can see in one evening.
posted by Merdryn at 8:22 AM on June 11, 2006

Regarding the heavens above link: If you get a chance to see the ISS fly over, it's worth your time to go out and see it.
posted by 517 at 8:27 AM on June 11, 2006

I second 517. Once, I got to see both the ISS and the space shuttle pass over within seconds of each other (the shuttle was on its long approach). A very cool experience.
posted by muddgirl at 8:37 AM on June 11, 2006

I'll third the ISS bit. It's BRIGHT. With binoculars or a tracking telescope, you may be able to make out a "T" shape to the orbiting space station.

What's really great about sites like Heavens Above is that you can print out a list (even star charts for location) of satellite passes that night. Set your watch to www.time.gov, call out your wife/husband/boyfriend/girlfriend/kids/neighbors and say "Check it out: A discarded rocket body from a rocket used by the Soviets is going to pass directly overhead at 9:54PM."

I really hope you get bit by this bug. :) First, satellites. Then, seeing Jupiter's four moons with a good strong pair of binoculars (yes, you can see them all lined up). You'd be amazed at how many star clusters you can see with a decent pair of binoculars, even with hazy summer light-polluted skies.
posted by Merdryn at 10:08 AM on June 11, 2006 [1 favorite]

Merdryn, I have the bug but sadly where I live in England it's nearly impossible to see anything, ever. Our night skies are sodium orange. This stargazing was made possible by a camp-out in mid-Wales, about as far from light pollution as it's possible to get in the UK - but even then, nothing like the skies I've seen in the U.S. or New Zealand (an astronomer's paradise). It's a real downside to living in what Lovelock describes, accurately as a sort of enormous city - one that's normally overcast and cold.

Thanks to all for the links, particularly to Heavens above. Based on where and when, it looks like the star was Envisat (which I have to say is the ugliest looking amazing thing ever). I didn't realize it was such a parking lot/junkyard up there.

One last thing, am I right to say that if it isn't flashing, it isn't an aeroplane?
posted by grahamwell at 11:02 AM on June 11, 2006

I am so jealous of all of you who can see stars in the sky at night. The sky here (Philadelphia suburbs) is bright orange even on the clearest of nights.
posted by dmd at 1:06 PM on June 11, 2006

Use this ESA site to find when the space station is a negative magnitude (smaller numbers are brighter) and at least 45 degrees max altitude. For example: Space Station over Chicago.

Click on the date to see it's star chart to locate it in the sky, and find out how far away it will be. It can be thousands of miles away and still visible.

Since the brightest stars are magnitude -1, if you can see any stars at all, you will be able to see the Space Station.

Often, it passes into the Earth's shadow, so it fades to a reddish color and then disappears suddenly. The star chart will show the path ending before the horizon.

These bright passes are very easy to see.
posted by jjj606 at 3:30 PM on June 11, 2006

I saw MIR fly over one night in Seattle, it was a bright light like a searchlight on a helicopter, then when it was directly overhead it faded to a pinpoint of light (it had passed the terminator, going from bright sunlight to the night side, therefore light faded). A month or so later I traveled down to California to meet a 'net interest' and we went out to Mt. Lassen and camped out under the stars to see the first linkup between MIR and the space shuttle. At the designated time we watched it come over the horizon out in the wilderness, just as in Seattle and as it passed overhead it faded to a small point of light just as it had before. Beautiful stuff.
posted by mk1gti at 9:35 PM on June 11, 2006

Man, you all have seen nothing until you've seen an "iridium flare". Use the same heavens-above.com site mentioned above, enter your location, and prepare to have your brain explode. Light pollution? Ha! These things top out at magnitude -8.

Hopefully we'll all have a chance to see the shuttle-chasing-ISS thing in a few weeks.
posted by intermod at 10:37 PM on June 11, 2006