What is this pulsating dot visible in day sky Denmark?

A

andersholck

New Member
I noticed a visible and "pulsating" dot in the day sky today. It's most likely a satellite but I can't get anything to line up in the Sitrec tool. (new to tool)
i have attached a video. I did at some point spot a second one close by. The dot were not moving very much. It was visible for me for maybe 5-10 minutes in roughly the same spot.
data from location:

2025-09-07T12:24:00.161Z UTC+2
Copenhagen denmark - 55.676098, 12.568337

I was looking almost straight up. in a North/northvestern direction
can anybody help?
 

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A satellite seems unlikely (basically impossible). Since it's relatively clear and not moving much, I think a balloon is more likely. Possibly a weather or scientific balloon (maybe amateur)
 
Mick West said:
A satellite seems unlikely (basically impossible). Since it's relatively clear and not moving much, I think a balloon is more likely. Possibly a weather or scientific balloon (maybe amateur)
Click to expand...
Thanks for the answer!
Why do you recon it would pulsate like it is doing. Very consistent pulsation throughout the 10 minutes I looked at it.
There were a second one close to it at some point, same cadence in pulsation.
 
andersholck said:
I noticed a visible and "pulsating" dot in the day sky today. It's most likely a satellite but I can't get anything to line up in the Sitrec tool. (new to tool)
i have attached a video. I did at some point spot a second one close by. The dot were not moving very much. It was visible for me for maybe 5-10 minutes in roughly the same spot.
data from location:

2025-09-07T12:24:00.161Z UTC+2
Copenhagen denmark - 55.676098, 12.568337

I was looking almost straight up. in a North/northwestern direction
can anybody help?
Click to expand...
Please tell me the local time. By any chance, did this happen before Noon? Perhaps between 9:00 to 11:00?


Maybe someone can extract metadata from this video, but I can't. It's blank.
 
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andersholck said:
Thanks for the answer!
Why do you recon it would pulsate like it is doing. Very consistent pulsation throughout the 10 minutes I looked at it.
There were a second one close to it at some point, same cadence in pulsation.
Click to expand...
Could it be rotating, and reflecting the sun off various surfaces? essentially like a disco ball?
 
Z.W. Wolf said:
Please tell me the local time. By any chance, did this happen before Noon? Perhaps between 9:00 to 11:00?
Click to expand...
Denmark is on UTC+2.

2025-09-07T12:24:00.161Z UTC+2 means that the local time was either 12:24 pm, or 14:24. I'm confused because the time is labeled Z, which should indicate UTC+0.
 
I didn't recognize this as a time and date. 2025-09-07T12:24:00.161Z UTC+2 I've never seen this format. I just bleeped right over it.

It turns out that this is ISO 8601 format.

T is a "separator"

And the 161 is 161 milliseconds. good grief

Apparently you read the time as 12:24 p.m. in the local time zone, and the time zone is UTC+2

So local time was 12:24 p.m.
 
Mendel said:
Could it be rotating, and reflecting the sun off various surfaces? essentially like a disco ball?
Click to expand...
If it is one of the balloon flights carrying a payload for scientific research, these objects do have solar panels and also instrumentation with possibly flat and reflective parts. If it slowly rotates (likely) it can behave like in the video IMO.

Example:
nasa-balloons-head-nor.jpg
 
It's a little later in the day than I was figuring on, and it's lower in the sky than what might fit the description... but Jupiter is up during the day just now.

The altitude in the sky over Copenhagen would have been 35 degrees. Not an awfully good match to the description - "I was looking almost straight up. in a North/northvestern direction." But witness compass directions and altitude estimates are often off.

I've mentioned a couple of times here that I've seen Jupiter in the daylight sky and the description fits. In this kind of situation Jupiter would be on the edge of being visible and the pulsating could be caused by the atmosphere. The "seeing" conditions change moment by moment. Jupiter would also fit this: "The dot were not moving very much. It was visible for me for maybe 5-10 minutes in roughly the same spot."

The video? I don't know if it fits... Was a telephoto lens in use?

Or it could be a metallized plastic balloon (a so called mylar balloon) throwing off occasional specular reflections of the Sun. The rest of time you'd see specular reflections of the sky. Still pretty bright.
 
Z.W. Wolf said:
I didn't recognize this as a time and date. 2025-09-07T12:24:00.161Z UTC+2 I've never seen this format. I just bleeped right over it.

It turns out that this is ISO 8601 format.

T is a "separator"

And the 161 is 161 milliseconds. good grief

Apparently you read the time as 12:24 p.m. in the local time zone, and the time zone is UTC+2

So local time was 12:24 p.m.
Click to expand...
No, I was wrong.

Wikipedia
Time zones in ISO 8601 are represented as local time (with the location unspecified), as UTC, or as an offset from UTC.
Click to expand...

If the time is in UTC, add a Z directly after the time without a space. Z is the zone designator for the zero UTC offset. "09:30 UTC" is therefore represented as "09:30Z" or "T0930Z". "14:45:15 UTC" would be "14:45:15Z" or "T144515Z".
Click to expand...

The Z is there, so it indicates Zulu time - UTC. Local time was 2:24 p.m. (And this does account for DST.)

Which pretty much washes out Jupiter.
 
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Z.W. Wolf said:
Apparently you read the time as 12:24 p.m. in the local time zone

Not you personally. You = One.

An Americanism. A Brit (who speaks in received pronunciation) might say:

"Apparently one is meant to read the time as 12:24 p.m. in the local time zone."


Which is factually wrong. But I already corrected that in post 12. I think I corrected it.
 
Yes, it's confusing. The Z should indicate that the time is UTC.

But why is the +2 there?

Something is screwy.
 
Z.W. Wolf said:
Yes, it's confusing. The Z should indicate that the time is UTC.

But why is the +2 there?

Something is screwy.
Click to expand...
Usually in this format the time is the local time, and the UTC+2 (or +0200) part indicates the timezone. I've never seen it with the Z in there - usually Zulu time is indicated by UTC+00, or +0000.

So 2025-09-07T12:24:20+0200 should mean it's 12:24 local time, in the UTC+2 timezone, i.e. 10:24 UTC.

(I've always found this formatting slightly counterintuitive, as my brain wants to add on the adjustment, making "12:24 + 0200" equal to 14:24, rather than subtracting it.)
 
Trailblazer said:
Usually in this format the time is the local time, and the UTC+2 (or +0200) part indicates the timezone. I've never seen it with the Z in there - usually Zulu time is indicated by UTC+00, or +0000.

So 2025-09-07T12:24:20+0200 should mean it's 12:24 local time, in the UTC+2 timezone, i.e. 10:24 UTC.

(I've always found this formatting slightly counterintuitive, as my brain wants to add on the adjustment, making "12:24 + 0200" equal to 14:24, rather than subtracting it.)
Click to expand...
Just two or three weeks ago I took a straw poll amongst some mostly technical-ish people on this very issue (users of the Devuan Linux distribution that hang around on the IRC channel, all corners of the globe are represented). Everyone who understood the question was in agreement, but not everyone understood the question.

However, whatever generated the string with two conflicting time zone indicators definitely has a bug.
 
Trailblazer said:
(I've always found this formatting slightly counterintuitive, as my brain wants to add on the adjustment, making "12:24 + 0200" equal to 14:24, rather than subtracting it.)
Click to expand...
To convert from UTC to UTC+2:00, you take UTC and add 2:00.

UTCtime=12:24
Timezone=+2:00
LocalTime=UTCtime+Timezone

but yeah, the notation of appending the +02:00 to a time that already includes the offset looks wrong
 
Z.W. Wolf said:
Please tell me the local time. By any chance, did this happen before Noon? Perhaps between 9:00 to 11:00?


Maybe someone can extract metadata from this video, but I can't. It's blank.
Click to expand...

This is video metadata extracted using MediaInfo tool v25.07. Recorded time is 12:24:20 local or 10:24:20 UTC. Full output in text file attached.

Code: 
Format                      : MPEG-4
Format profile              : QuickTime
Codec ID                    : qt   0000.00 (qt  )
File size                   : 79.7 MiB
Duration                    : 23 s 773 ms
Overall bit rate mode       : Variable
Overall bit rate            : 28.1 Mb/s
Frame rate                  : 24.664 FPS
Recorded date               : 2025-09-07 12:24:20+02:00
Encoded date                : 2025-09-07 11:08:53 UTC
Tagged date                 : 2025-09-07 11:08:54 UTC
Recorded location           : 55.6897°N 12.5438°E 11.547m
Writing library             : Apple QuickTime
Writing operating system    : Apple iOS 18.6.2
Writing hardware            : Apple iPhone 14 Pro
 

Attachments

Z.W. Wolf said:
It's a little later in the day than I was figuring on, and it's lower in the sky than what might fit the description... but Jupiter is up during the day just now.

The altitude in the sky over Copenhagen would have been 35 degrees. Not an awfully good match to the description - "I was looking almost straight up. in a North/northvestern direction." But witness compass directions and altitude estimates are often off.

I've mentioned a couple of times here that I've seen Jupiter in the daylight sky and the description fits. In this kind of situation Jupiter would be on the edge of being visible and the pulsating could be caused by the atmosphere. The "seeing" conditions change moment by moment. Jupiter would also fit this: "The dot were not moving very much. It was visible for me for maybe 5-10 minutes in roughly the same spot."

The video? I don't know if it fits... Was a telephoto lens in use?

Or it could be a metallized plastic balloon (a so called mylar balloon) throwing off occasional specular reflections of the Sun. The rest of time you'd see specular reflections of the sky. Still pretty bright.
Click to expand...
Definitely not Jupiter,
but don't know what else.

Maybe balloon as people are mentioning but I have no clue.
In the very last frame of the video, you can see that there is a similar dot (down to the right) also reflecting light in a similar matter, but this one wasn't as persistent as the main one.
 
I have photographed a very similar looking light over London a couple of times now, most recently in October this year. Clear skies, (apart from contrails), and seemingly at high altitude. Very bright, giving the appearance of glinting as though catching the sun. I'm a box-fresh newbie so am currently awaiting moderator blessing, but I look forward to contributing to this thread with photos and footage. The film perhaps exceeds the size limitations of the forum so I'm going to try to get it to Mick via a file-sharing platform.
 
Feels a lot like a "Mylar" party balloon, which I am reliably informed aren't really made fro Mylar (tm) but that's what the world seems to call them now. Turning in a bit of turbulence, sometimes bouncing light at you from a shiny bit, sometimes a non shiny bit is at the right angle and so it is less bright. (Balloons often just drift along in the air without turning much, but turbulence happens sometimes...)
 
We can -- but I suspect it is like "Kleenex,"m in that the specific has become the generic in general usage, and I doubt we can do much about it.
 
andersholck said:
2025-09-07T12:24:00.161Z UTC+2
Copenhagen denmark - 55.676098, 12.568337
Click to expand...

andersholck said:
Guys, im so sorry that I just left you all hanging here.

The local time in Copenhagen was 12.24

The timestamp is from the SITREC app on this site.
Click to expand...
Did Sitrec actually display "2025-09-07T12:24:00.161Z UTC+2" at some point? If it did I need to fix it, but I can't figure out where that might have been. Can you show a screenshot?
 
Mick checked out my footage and concluded it looks like a balloon, which I'm happy with. It was clearly visible to the naked eye but couldn't be resolved satisfactorily with the available equipment on the day, namely my trusty Panasonic GX8 Micro Four Thirds Camera with Lumix G 14-42mm lens attached. Despite OIS, neither lens nor camera were up to the task of a decent closeup of the object. That said, I wasn't afflicted by the Tedesco Shakes, so I'll post a couple of stills and cropped details for reference. London has some of the most heavily congested skies on the planet, and I do wonder if such airborne clutter could present an airline safety risk if sucked into a jet engine.
 
A bit underwhelming, admittedly, but it would be nice if I could get a telephoto lens on one of these things someday, if only to get a conclusive reference image for other folks. I like the idea of 'Foil Balloons'...maybe BFBs - Baco-Foil Balloons?
 

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A couple more. Still shots don't really convey the rather pleasing glistening effect, but you get the idea from Andersholk's opening post footage. At any rate, it makes an interesting change from the daily planes, helicopters, parakeets and seagulls that assail the London firmament.
 

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One more, this time a screengrab from the footage, showing the BFB now partially obscured by a contrail, but still bright. It seemed to go higher and higher till I lost sight of it. Also visible: part of my guttering, which badly needs sorting.
 

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Carling 4737 said:
London has some of the most heavily congested skies on the planet, and I do wonder if such airborne clutter could present an airline safety risk if sucked into a jet engine.
Click to expand...
The risk, if any, is small. Jet engines are large and certified against the impact of several small or few large birds; the lightweight balloon would likely be propelled outward in the first fan and traverse the engine with the bypass air. If worst came to worst, the crew would shut the engine off, and land safely on the remaining engine(s).

Smaller aircraft are more at risk. I know of one that crashed after it encountered a large bundle of balloons tied together with ribbons, which probably got caught on the control surfaces and effectively "steered" the aircraft into the ground. This aircraft sucked a balloon into its engine and the engine quit (the pilot was aiming for the balloon):
Screenshot_20251211-160949.png


I have been looking for balloon incidents, and they are very rare. Birds are much more dangerous.
(See also https://www.metabunk.org/threads/un...d-weather-balloon-collision.14502/post-355099 ).
 
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Carling 4737 said:
...I do wonder if such airborne clutter could present an airline safety risk if sucked into a jet engine.
Click to expand...
Mendel said:
Jet engines are large and certified against the impact of several small or few large birds
Click to expand...

Aircraft engines and windshields/ canopies are sometimes tested with a flight impact simulator, more widely known as a chicken gun, Wikipedia https://en.wikipedia.org/wiki/Chicken_gun. The carcass of a bird (often a chicken) is shot at the item being tested.

A couple of urban myths have grown up around the chicken gun:
British locomotive engineers borrowed one to test an experimental high speed train's windscreen; the windscreen was obliterated and the chicken was embedded in the rear wall of the driver's compartment. The shocked researchers contacted the FAA to find out if they'd done anything wrong, and got the response
External Quote:
Use a thawed chicken.
British Aerospace engineers loaded a frozen chicken, left it to defrost, but when they later ran the test it had similarly destructive results to their railway counterparts' trial. Reviewing CCTV footage of the unattended chicken gun, they saw an unfortunate cat, lured by the scent of the thawing bird, crawl into the tube...

Both stories courtesy of Snopes.com, https://www.snopes.com/fact-check/catapoultry/, where they are classified as "legend". There's a bit of interesting theorizing about why such stories are popular.

Anyway, a foil party balloon is unlikely to be as destructive as a chicken, even a thawed chicken.
 
John J. said:
Aircraft engines and windshields/ canopies are sometimes tested with a flight impact simulator, more widely known as a chicken gun
Click to expand...
The TV program "Mythbusters" showed one of those a number of years ago. I recall it only dimly, but here is a clip on YouTube if anyone's interested.

Source: https://www.youtube.com/watch?time_continue=34&v=cHTdFGwX6Xg&embeds_referring_euri=https%3A%2F%2Fvideo.search.yahoo.com%2F&embeds_referring_origin=https%3A%2F%2Fvideo.search.yahoo.com&source_ve_path=Mjg2NjY

Edit to add: This was first shown in 2004 - longer ago than I thought!
 
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Glad to learn that the balloon risk to aviation is small. I looked up some bird strike reports and they do sound like a serious and increasing problem. Now I've learned that someone gets paid to fire a frozen chicken from a gun and I feel like I've missed my calling in life.

Drones are increasingly becoming more of an aerial threat, and they are undergoing a rapid and deadly evolution in Ukraine. A subject for a different thread, though.

https://powercorridors.in/how-bird-strikes-can-bring-down-planes-a-look-at-the-growing-threat/
 
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