Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Fortran on 18/07/2009 16:50:03

Title: What did I see?
Post by: Fortran on 18/07/2009 16:50:03
About a week ago I awoke around 3:15 GMT (just before dawn) and noticed a very bright object around due south about 25 degrees above the horizon.  At first I thought it was Venus even though it was much brighter than I had ever seen the planet. After a few a few minutes I again peered out and was surprised to see the object had faded to about half it's previous brightness. Since it appeared stationary I wondered whether it was a super nova - but after a few more minutes I went back to sleep. It was not a dream as my wife also saw the object. Later in the day I checked the position of Venus and promptly discounted this as the cause. For the last few days this has perplexed me until I realised that the direction of the observation coincides with with geostationary TV satellite positions. The following night (to the annoyance of my wife) I set the alarm for the same time - you guessed it - no sign of anything near the location where seen.

Is it possible that I saw a direct reflection from the solar panels of a geo sat?  does anybody have any other possible explanations?
Title: What did I see?
Post by: RD on 18/07/2009 17:12:04
Iridium flare?

Explanation: Have you seen an Iridium flare? Satellites in low Earth orbit reflect sunlight and are often visible gliding across early evening and predawn skies. But sun glints from Iridium commercial digital communications satellites are providing the most spectacular sightings. This Iridium flare photographed on September 20, 1997 by Belgian amateur astronomer Chris Dorreman reached an impressive -8 magnitude (about as bright as the half illuminated Moon).
Title: What did I see?
Post by: Pumblechook on 18/07/2009 18:12:31
Geosats are regularly seen from Earth.
Title: What did I see?
Post by: Soul Surfer on 18/07/2009 20:02:06
Sounds just like a sattelite flare.  Some of them are predictable and get listed in the astronomy events web pages.
Title: What did I see?
Post by: syhprum on 18/07/2009 22:22:13
Here is a useful Iridium satellite prediction program
Title: What did I see?
Post by: LeeE on 18/07/2009 22:54:56
Low Earth orbit satellites move quite quickly, so I doubt it was a sat.  It was most probably a distant aircraft flying pretty much directly towards you.  As it was night/dusk, it would have had its landing lights on, and they are very bright when pointing towards you and easily visible from 40+ miles away.
Title: What did I see?
Post by: lyner on 19/07/2009 10:21:15
Geosats are regularly seen from Earth.
With a telescoe (it says). They are an awful long way away!
Title: What did I see?
Post by: Fortran on 23/07/2009 23:20:17
Thanks for the replies, Aircraft? probably not, the direction of this light was not a usual flight path. Since the light faded whilst the source was stationary (reference a nearby star) this also rules out a plane - though I have seen 'stationary' plane lights before. Iridium flare? no, I have seen many of these. I still think it may have been sunlight glinting from a geostationary - otherwise I'll go with the plane - 3rd maybe some Alien trying to find his home planet...
Title: What did I see?
Post by: turnipsock on 24/07/2009 00:00:16
The flares and satellites are only visable at dusk and dawn, not in the middle of the night. The flares are very short lived I believe as its just the sun reflecting off a big solar panel.


An iridium satellite.
Title: What did I see?
Post by: LeeE on 24/07/2009 01:22:09
Work out the maximum area of light that could be reflected from a geosynchronous satellite, remembering that the light won't be appreciably brighter than direct sunlight on Earth and won't be focussed towards you, and then figure out if you could see it from 22,000 miles away.

We don't have flight lanes, as in the US, and 'usual flight paths' in the UK are only flown by regularly scheduled flights.  In any case, if it was actually 40+ miles away you wouldn't be aware of what the usual flight paths were for that area unless you're a bit of an enthusiast, and it could have easily been a military or non-scheduled flight anyway.  The fact that the light dimmed as you watched it suggests even more strongly to me that it was an aircraft; unless it was flying directly down towards you on the ground the axis of the light would drift past you and the light would have indeed dimmed.
Title: What did I see?
Post by: lyner on 24/07/2009 15:50:01
I saw something similar, recently and reported it here.
The only solution which really seemed to fit was a model hot air balloon - (Chinese Lantern style) with a light in it. Mine was going Southwards, across the sky. It took a couple of minutes and it disappeared out over the sea (in Brighton), getting fainter and fainter.

A disappointing explanation  - SO UN-SEXY - but reasonable. Especially as it looked to me to be 'on fire'. The actual distance was impossible to judge and I can't remember the wind direction and speed. It was unpowered because there was total silence.
Title: What did I see?
Post by: LeeE on 24/07/2009 17:00:27
A model hot-air balloon is a distinct possibility for what you saw SC; they're easy enough to make.
Title: What did I see?
Post by: lyner on 24/07/2009 17:13:17
Yeah. Really pissed me off that there could be such a mundane explanation.

I think it was a flaming meteor fireball which entered the atmosphere at just the right angle and speed to dissipate at just the correct rate to take it right across my sky. As it would have gone into the sea, no one can prove my explanation's wrong.
You can't say it's the worst nonsense that has ever graced this forum so I'm sticking to it!!
I can choose not to wear my 'hat of rigour' if I want to, today.
Title: What did I see?
Post by: Pumblechook on 24/07/2009 23:03:31
We had some sky lanterns over here one day.. Quite eerie they are.
Title: What did I see?
Post by: Pumblechook on 24/07/2009 23:04:35
I saw the ISS once and picked up radio sigs from it.
Title: What did I see?
Post by: turnipsock on 24/07/2009 23:45:58 (

The ISS can often be viewed from the earth and is the brightest thing around other than the sun and the moon.
Title: What did I see?
Post by: LeeE on 25/07/2009 16:12:15
SC: I've only ever seen one meteor fireball, but it was certainly a lot faster than any sort of hot-air balloon.  How long was it visible for, and what angle of the sky did you see it traverse?
Title: What did I see?
Post by: lyner on 25/07/2009 17:10:35
I hate to tell you, because you will shatter my dream. From 45 degrees elev N to near horizon S. Straight line. Took 1 or. 2 minutes.
Sounds too much like a sky lantern dunnit?
Title: What did I see?
Post by: Stefanb on 26/07/2009 02:15:37
Yeah... it's too bad. The one meteor I've seen faded in less than half a second. It looked as if a paintbrush had painted fast fading scarlet a mile in the sky
Title: What did I see?
Post by: LeeE on 26/07/2009 11:39:04
Yeah, sorry Doc, but one or two minutes sounds far too long for a meteor.  Meteors are normally traveling at hypervelocity, roughly between 3-30 km/s, so if you saw it for just one minute it would have traveled at least 180 km, and probably a lot further.
Title: What did I see?
Post by: Fortran on 02/08/2009 23:37:22
It seems what I saw was jupiter temporarily brightened by the impact of a comet collision the day before it happened :=)
Title: What did I see?
Post by: LeeE on 03/08/2009 00:53:42
The recent Jupiter collision was reckoned to have happened on 19th July, one day after you first posted here, and therefore about a week after what you saw.