Unidentified Flying Object

20 July, 2008

A Leonid Fireball Meteor from 1966.
A Leonid Fireball Meteor from 1966.
Image: J. W. Young
Source: TMO, JPL, NASA.

Question: I saw a very bright object moving across the sky last night. It seemed to be right above us and was travelling quite fast. Can you tell me what it was?

Answer: The object you saw last night was almost certainly a meteor (shooting star).

The only other objects that move noticeably across the sky (other than aircraft) are satellites. Satelites move considerably more slowly than meteors and are only visible just after dark or just before dawn.

A very bright meteor (brighter than any of the stars or planets) is called a fireball. Sometimes a fireball is also called a bolide although often the name bolide is used only for large meteors that explode at the end of their flight.

It is very difficult to judge the distance to such small, fast moving objects, so most people imagine meteors to be closer than they really are. Meteors lose visibility about  20km above the ground. Thus, if you could still see the meteor, it would have been at least 20km away.

Most meteors (and around one in three fireballs) are fragments of comets made up of ice and dust. They are generally very small, about the size of a grain of sand. Meteors this size usually burn up completely about 100km from the Earth’s surface, generating a huge amount of light as they do so.

A small number of meteors (but a much larger proportion of fireballs) come from rocky asteroid material. Most are small (about the size of a pebble) but they can be up to kilometres across. Large rocky meteors do not always burn up completely. Meteors that survive the passage through the Earth’s atmosphere and hit the ground are called meteorites.

Two specimens of the Murchison meteorite

Two specimens of the Murchison meteorite which fell at Murchison, 80 km north of Melbourne, on the 29 September 1969. 
Photographer: Frank Coffa / Source: Museum Victoria

Reports of observations of meteors are very useful to astronomers. People who do sight these events are encouraged to report them to the Astronomical Society of Victoria Skyline (03 9888 7130) or the International Meteor Organisation.

Comments (8)

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Brian Milkins 13 July, 2009 10:03
Driving into Beaufort (Victoria) at 10.15 p.m. last night (Sunday 12th July) an exceedingly bright, what I would describe as a swirling blue-green ball with a very long, bright tail shot across my line of sight, travelling very rapidly in a north-westerly direction, very low in the air and lasting maybe 1 - 2 seconds. My immediate reaction was that it was something crashing and I actually expected to see some sort of an explosion - however I didn't see any evidence of this occurring. The driver of a Queensland registered truck travelling about 20 metres immediately in front of me owned by Australian Express Parcels (registered number AXL.13) must have also observed this amazing sight. I'm puzzled what this was. Have you any ideas and did any other people from around the Beaufort area report this sighting? Regards Brian Milkins.
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Jaclynn Jones 13 July, 2009 18:44
I was driving home last night from Coburg in Victoria on Sunday 12th July at 10.15, when I saw the same bright light Brian Milkins saw. I was travelling off the Bell St exit, onto the Tullamarine freeway and travelling toward Essendon when I saw an extremely bright light which was descending very fast.It appeared as a white ball with a long tail and had a bluish tinge (in the brief time I saw it.)I also expected to see some kind of explosion but I could not see any evidence. My jaw dropped with surprise as I knew it was not an aircraft or anything I had seen before. I expected something to be on the news or some acknowledgement of the event but have heard nothing.I am very pleased to know that someone else saw it too! Can anyone confirm what we saw? Regards Jaclynn Jones
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Discovery Centre 30 July, 2009 13:26

Hi Brian & Jaclynn,

What you saw was certainly a shooting star or meteor – the only other kind of celestial object that moves noticeably across the sky is a satellite.

Meteors lose visibility around 20km above the ground, so the closest you saw the meteor was about 20km away. It was probably travelling at around 50 km/s when it first hit Earth’s atmosphere, slowing down to about 2km/s.

Most meteors are fragments of comets made up of ice and dust. They are generally very small, about the size of a grain of sand. Although very small, because they burn up completely, they generate a lot of light. Small meteors generally burn up around 100km above the ground.

You can report your sighting to the International Meteor Organisation.

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Kerry hude 31 January, 2010 08:59
I live in Bairnsdale, East Gippsland, Victoria. I was sitting on my patio last night - Saturday 30 January. At about 11.25 pm I believe I saw a meteorite. I think I would have been facing N.W and it was heading E.W.? What facinated me was that it was so big compared to distant shooting stars I have seen during my life. It had a yellow firey tail. I think it lasted 3 or 4 seconds.
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Ashley kordus 25 August, 2010 23:05
Did any body see a white flaming ball/streak that ended shining bright green befour it disappeared in the sky at about 10.35pm on the 25th of August 2010 that started from the west and proceeded in a downward motion to the north west of Melbourne it was seen clearly by a resident of West Footscray did anybody else see this if you did can you email me the suberb you saw it from and any ideas of what it may have been to kordus.ashley2@gmail.com
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Dan Stax 26 September, 2010 21:55
When I went to hang out the washing tonight, Sunday, 26th September 2010, a gold streak caught my eye and when I looked up I saw what could only be described as a shooting star enter the earths atmosphere and shoot across the sky from east to west. It disintegrated into about 3-4 pieces within 2-3 sec. It was the most beautiful sight in the night sky. It happened at about 2130hrs. Did anyone else see it..
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Dea Swalling 1 November, 2010 18:42
Just as I got home today 01.11.2010 at 5pm, my son and I saw two green lights travelling at very high speed over the Doncaster area. They were long and very low, there was no sound, there were no planes in the area and moving to quick to be a plane. Did anyone else see this?
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Steve 1 November, 2010 22:23
I saw a similar fireball as described above this afternoon (1st November 2010). A bright green colour with a long tail streaking across the sky. As it trailed off it seemed to have smaller bits coming off it. This fascinated me as it was about 5pm and still bright and sunny. It was really interesting to see this against a blue sky. Wondered if anyone else saw this, but didn't know how to find out.
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