I have seen objects that look like satellites, but there are many of them, and they move in one direction in a straight line. Can someone help me to understand what they are?
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$\begingroup$ Note that in some higher-inclination orbits of starlink, larger gaps between starlink sats may be visable. $\endgroup$– AnarchoEngineerCommented Aug 20, 2023 at 21:12
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28$\begingroup$ I'm curious as to why you tagged this with [spacex]? You're asking if the lights are satellites, but your tag suggests you know not only that they are satellites, but also whose satellites, and (since SpaceX's satellites are pretty much only Starlink) also which satellites. Were you intending to answer your own question on this? (I've added the [starlink] tag, since it seems appropriate - but the [spacex] tag was there already.) $\endgroup$– Infinite_MaelstromCommented Aug 20, 2023 at 21:54
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$\begingroup$ Did you try to run "Stellarium"? It knows about many satellites. Also available as Android app where you can "point at the sky" to "see what you see" ;-) $\endgroup$– U. WindlCommented Aug 22, 2023 at 7:01
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1 Answer
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This is almost certainly a Starlink train.
These look something like this (see image) and are usually seen shortly after a Starlink launch. There have been a few Starlink launches this week, so it is not too surprising that you have seen some.
answered Aug 20, 2023 at 21:02
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$\begingroup$ What is the approximate altitude of the satellites in that photograph? $\endgroup$ Commented Aug 21, 2023 at 23:49
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$\begingroup$ They're in low earth orbit, so around 2000 km above the Earth's surface I believe. $\endgroup$– AAM111Commented Aug 22, 2023 at 0:33
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4$\begingroup$ Starlink is a lot lower than 2000km - that's just the upper limit for L.E.O. These starlinks had just been deployed, so they were at an altitude lower than 300km. They become less visible as they raise their orbits via onboard thrusters, which takes a few months. $\endgroup$ Commented Aug 22, 2023 at 0:36
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3$\begingroup$ In addition to moving to a higher orbit, I believe they also have different configurations / attitudes optimized for low-drag vs. low-visibility. As long as they are still within the (relatively) thicker parts of the atmosphere near their deployment orbit of ~250km they operate in a low-drag configuration, but once they reach their operational orbits at 540–570/~340 km (v1 Phase 1 and 2) and 530–560 km (v2) they transition to a low-visibility configuration. But I could be mis-remembering things, and also, they changed the flare mitigations a couple of times. (Remember the visors?) $\endgroup$ Commented Aug 22, 2023 at 12:42
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$\begingroup$ @JörgWMittag I pretty sure that's exactly what happens, unless I'm mis-remembering in exactly the same way. :-) I think that the newer Starlink sattelites are sort of in the +6 and +7 magnitude range when at final altitude and fully deployed (and sunlit) so while astronomers are still painfully aware of how many are crossing the sky at any moment, stargazers mostly don't see them. $\endgroup$– uhohCommented Aug 26, 2023 at 0:11