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What is this? Satellite? Iridium flare? Asteroid? Someting else?

Off-topic Satellite
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Nick Large avatar
Nick Large avatar
Hi everyone,

Yesterday night i was imaging the Cone Nebula in Monoceros and I notice something I have never seen (yet) on 4 of my sub-exposures.
It moved linearly across the 4 subs . My subs are 5 min longs so I would expect significant trailing from a satellite on each image, but it is not the case here. I've checked on Heavens Above and not satellites were predicted to fly by at that time (23:03-23:18 CST).

I've stacked the 4 subs and annotated the image with zoom-in of the object.

Any idea what this might be?

Thanks,
Nick

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andrea tasselli avatar
andrea tasselli avatar
It looks like a satellite with a very dark underside that briefly flashes every 5 mins or thereabout.
Boyan Stiliyanov avatar
Boyan Stiliyanov avatar
andrea tasselli:
It looks like a satellite with a very dark underside that briefly flashes every 5 mins or thereabout.

It could be this. You checked Heavens Above for passing satellites, but did you check all of the satellites (it could be those non usually visible radio satellites?)? It isn't a geo-sync satellite because it moves relative to the sky. Could it be space junk that rotates and therefore shines on regular intervals? I haven no idea.

Iridium flares flash for just a couple of seconds and their brigthness gets high and then low in a short period. Basically what you're getting is a lightstreak. Asteroids should show up the same way - a lightstreak but very dim.
Marc Dickinson avatar
Marc Dickinson avatar
Just glancing at it, appears to be moving east along a line of DEC at ~5 min RA spacing, same time length as your subs, you can plate-solve and check if that is right.  If so, it would likely be a geosynchronous satellite.  Not sure why it wouldn't have a 5 min long streak though unless its reflection is changing over time.
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Nick Large avatar
Nick Large avatar
Thanks everyone for your replies. My money is on a satellite as well but the absence of long trail is really intriguing. I checked all the satellites availaible in Heavens above (including Radio satellites) but it didn't show anything passing in this area that night.
Maybe an alien ship signaling me smile

The good thing is that if doesn't spoil my image or mess up my stacking :-)
Duane Melvin avatar
Duane Melvin avatar
If this is a rapidly moving object outside of Earths proximity and perhaps outside of our solar system..it must be gigantic and traveling at incomprehensible speed… and able to give off photons for only a few seconds at a time…. then shut these photons off for five minutes…then repeat.  Also the relative size is decreasing as it appears to be moving further away…… as seen in each instance.  If it is in Earth orbit, this object is tumbling quite slowly and somehow not reflective on 95 percent of its surface or else a trail would be produced..  seems unlikely to me to be in orbit.
Tim McCollum avatar
Tim McCollum avatar
Most geostationary are spin stabilized.
I have observed this many times as they are passing thru Orion.
The ones I've seen flash / rotate once about ever 13 seconds.
I've put my binoculars on them and watch as they move against the back ground stars.
Tim
Paolo Manicardi avatar
Paolo Manicardi avatar
Tim McCollum:
Most geostationary are spin stabilized.
I have observed this many times as they are passing thru Orion.
The ones I've seen flash / rotate once about ever 13 seconds.
I've put my binoculars on them and watch as they move against the back ground stars.
Tim

yes this is true, but in this case we will se an almost continuos trace, with luminosity that change along the trace due to rotation.
In this case the strange thing is that this flash occur at 5min interval and seems in syncro with the exposures.
Duane Melvin avatar
Duane Melvin avatar
Indeed….that's the amazing part….this phenomenon is MOVING across the guided FOV.  Satellites move granted….but reflect all along the movement; thus leaving behind those wonderful perfectly straight light lines I abhor to find in my long exposures!   This thing is getting dimmer with each position too.  What can turn on, emit photons,  for a few seconds,  then turn off for 5 minutes….move across the FOV undetected,  then do this four times in a periodic function equally spaced intervals…….and exactly four times only.  I guess a stationary satellite will also move across the FOV because it moves with earth.  But seems odd that it is dimming.  I guess the sun's angle of light would do just this though as it is constantly changing angle with respect to the sun.
andrea tasselli avatar
andrea tasselli avatar
If it gets dimmer and its albedo isn't changing on its own then the object is moving further away from the observer.
Well Written