# Did I see a meteor(oid) or space debris or something else?

About three years ago I think, at night I've seen something enter the atmosphere in a glowing bright fireball. But I think it wasn't the fire from burning up, but because of ionization (what also happens to meteors) but I might be wrong and it may have indeed been fire. There was also a kind of a contrail behind the glowing ball (which was visible only in the vicinity of the ball). It was in November in the northern hemisphere, so it might have been a Leonid, but it didn't look like the usual meteors. It was much slower and brighter. It was cloudy that night and eventually it disappeared behind a cloud. Whatever it was, it wasn't a typical meteor nor was it an airplane (it was quite straight above me, soundless and it was something entering the atmosphere).

My guess is it was either a meteoroid that was very dense and comparably big (several feet) and a comparably slow one, or it was some retired satellite or some spacecraft debris entering the atmosphere. What do you think?

update: I estimate its speed at about 1/6 that of a typical shower meteor.

• Your description does sound like re-entering space junk. An exact date, time and location would help a lot. At least if you had the date and place. Without that I don't think it is likely to be possible to certainly identify the object as re-entering debris. Do look at youtube videos of re-entries as seen from Earth, they are much slower than typical meteors. – James K Aug 14 '20 at 15:47
• @JamesK As said, it was in a November (either 2017 or 18) and on the northern hemisphere (of planet Earth, I forgot to write that, sorry). :-) About 48 degrees latitude. – Giovanni Aug 14 '20 at 15:59
• Yes, I don't think that is enough to go on. Sorry. Need a location (eg town name, gps coordinates long and latitude) and date. – James K Aug 14 '20 at 16:02
• @JamesK 48 deg latitude. If I tell you the longitude you'll find out where I am or have been. I don't remember the exact date anymore, but why is that necessary? Can you tell me the very exact object from which the debris came? I remember Tiangong 1 was still in orbit, so it must have been Nov 2017. Rather at the beginning of November I think. – Giovanni Aug 14 '20 at 16:06
• @JohnHoltz Do meteoroids really get that slow? I estimate its speed at about 1/6 that of a typical shower meteor. – Giovanni Aug 14 '20 at 16:16

The OP's clarifying comment under the question offers an opportunity to examine further:

Do meteoroids really get that slow? I estimate its speed at about 1/6 that of a typical shower meteor.

The apparent or angular speed of an object in the upper atmosphere depends on several things, including

1. the actual linear speed in say km/sec
2. the distance from observer to the object
3. the cosine of the angle between the direction of motion and direction to object (i.e. the dot product of the normals of those vectors); if it's moving straight towards you the angular speed is zero.

The linear speed of meteors with respect to Earth is a function of the orbital speeds of both objects. See the (currently unanswered) question How to calculate the position of a meteor shower's radiant point based on its associated comet's orbit? and links therein. Just for example if the meteor shower is associated with a comet in a circular orbit at 1 AU with an inclination of 90 degrees (a "polar orbit") then the relative speed is

$$\sqrt{2} \sqrt{G M_{Sun}/1 \text{AU}} \sim 29.7 \sqrt{2} \text{ km/s} \approx 42 \text{ km/s.}$$

Speeds of meteors relative to Earth can theoretically be somewhat higher or much lower than this. So despite 42 being an aesthetic number let's just us 30 km/s for a typical value.

The orbital speed of a spacecraft at 100 km above the Earth before drag stars slowing it down is

$$\sqrt{G M_{Earth}/(6378+100) \text{km}} \approx 7.8 \text{ km/s.}$$

Since both are roughy at the same distance, a burning reentry might appear to move (in angular velocity) four to six times faster than a small bit of space junk burning up.

That ratio could be reduced if the meteor was sighted near the radiant point, where it will appear to move much more slowly by a factor of the cosine of the angle mentioned above.

So in some cases a meteor might appear to move the same speed as a bit of reentering junk, but in that case the trail will be very short, it will not cross the sky. From the OP's question it sounds like the motion was much larger than a few degrees so we can rule this out.

But what if the comet associated with the meteor was moving in an orbit nearly tangent to Earth's with a similar to velocity to that of Earth at the intersection point (i.e. low inclination)?

There can't be absurdly slow slow meteors like that because of Earth's gravity. An object moving nearly the same as Earth will accelerate as it gets closer to Earth. $$v_{escape} = \sqrt{2} v_{orbit}$$ means even a co-orbiting object will reach almost 10 km/s by the time it enters the atmosphere. And I don't know of any meteor showers associated with comments who's orbits fit this description.

## Conclusion

Most likely it was space junk. Bits and pieces reenter regularly so while it's not common to see, from time to time people see it. And soon some people may pay to see it on demand!

• Who would ever have thaught space debris could become that beautiful. – Giovanni Aug 15 '20 at 6:18
• @Giovanni I'm sure it was gratified that someone noticed ;-) – uhoh Aug 15 '20 at 6:35
• No, I was alone or noone else was looking up if there was someone and I think I didn't ever tell anybody of it until yesterday. – Giovanni Aug 15 '20 at 6:45
• After seeing some videos of entering space debris at night I even more think it were some, and I remember now there really seemed something to fall away from the glowing ball, on its contrail. – Giovanni Aug 15 '20 at 6:49
• No I just stated that there r videos that helped me remember there seemed to brake something off the glowing orb. Just google for "entering space debris" on youtube or so. – Giovanni Aug 15 '20 at 10:06