A streak of light in a star trails image

Mick West

Staff member
DSCN8572 Last Frame South Star Trails.jpg

The above image is mostly star trails, looking south (you can see the curve around the southern celestial pole. But what caught my eye was the streak of light going behind the trees.

Now at first I was convinced it was a meteor - it's Persid season after all. And the trail starts bright and then flickers out. However the streak formed over two frames, which were both 25 second exposures with a short gap in-between. The meant it was probably moving relatively slow. So then I though of space junk.

To get a better look I isolated the trail to get more detail.
Metabunk 2018-08-12 07-48-55.jpg

Then it becomes clear it's some kind of aircraft. As it fades out there's a series of regular spaced flashes
Metabunk 2018-08-12 07-49-57.jpg

And back near the start there's a similar sequence.
Metabunk 2018-08-12 07-52-46.jpg

And we can see it did actually start abruptly, meaning it was there for the entire first frame,
Metabunk 2018-08-12 07-57-41.jpg

And close examination of the east end shows a continuation of the trail:
Metabunk 2018-08-12 08-01-37.jpg

It took over two full frames, so it took around a minute to cross the field of view.

So ultimately a banal explanation - just a plane flying from west to east. As the angle changes the main light becomes less and less visible, then is hidden by the body of the plane. A bit boring, but it goes to show you should always check your initial assumptions. I was initially convinced it was a meteor or space junk by the way the trail faded out.