I'm not sure what I saw was an Iridium sat on reflection, as it was in no way a 'flare'. It was exactly what the ISS looks like in the night sky in fact - except that according to my app the ISS was over Australia at the time...Saw a few last night, but gave up quite quickly, OH saw a couple of corkers. (I had driven up from Wales in some tiring traffic and we're off early to Whitby for Sunday morning so needed some shut-eye !)
And an Iridium flare in daylight a couple of days ago ...
I'm not sure what I saw was an Iridium sat on reflection, as it was in no way a 'flare'. It was exactly what the ISS looks like in the night sky in fact - except that according to my app the ISS was over Australia at the time...
Sliver of a partial eclipse starting 1940BST 21 August for 48 minutes.didn't see any this year. bah, curse my tired eyes. And clouds. Sposed to be an eclipse in america land soon, I don't know if that means we'll see it as well but you'd think so wouldn't you.
The comet is massive compared to the bits we're seeing. Each meteor is about the size of a grain of sand, and the comet is 26km in diameter.So as the meteorite shower is due to the Earth going through the cloud of the Swift-Tuttle comet. Surely over time the comet will shrink as matter is released from it every time it passes round the sun - so how come we're still seeing the Perseids, shouldn't it have all dissipated by now? Recorded sightings go back to 69bc. And if the comet is on 133 orbital cycle, how come we go through it's cloud every year?
Schoolboy errors I'm sure. Please explain.
It will indeed shrink and has a limited lifetime.So as the meteorite shower is due to the Earth going through the cloud of the Swift-Tuttle comet. Surely over time the comet will shrink as matter is released from it every time it passes round the sun - so how come we're still seeing the Perseids, shouldn't it have all dissipated by now? Recorded sightings go back to 69bc. And if the comet is on 133 orbital cycle, how come we go through it's cloud every year?
Schoolboy errors I'm sure. Please explain.
The comet is massive compared to the bits we're seeing. Each meteor is about the size of a grain of sand, and the comet is 26km in diameter.
There's enough dust left to keep us in meteor showers for a long time
According to Wiki, the cloud has been there for 1,000s of years.But what about going through the cloud every year if it's only on an orbit of once every 133 years, surely the cloud would dissipate well before it returns.
It does gradually spread out, gravitationally perturbed (though solar radiation pressure does rearrange some of the lighter material). Then every 133 years the parent comet repopulates the trail of debris. That’s why the precise date and peak varies form year to year and why after a recent passage a meteor storm is often observed (the classic being 55P/Tempel–Tuttle which re-seeds the Leonid shower every 33 years or so and has yielded some spectacular meteor storms - I saw the last one back in 1999, from the UK, and it was truly spectacular).But what about going through the cloud every year if it's only on an orbit of once every 133 years, surely the cloud would dissipate well before it returns.
Hmm..I suppose so, because it happens, but I'd like to see a graphic (.gif) showing the orbit of the cloud and Earth's.
The trail of ‘debris’ (increasingly being laid down well before arrival in the inner solar system and then decreasingly so well after) is co-moving with the parent body and largely stays along the same orbit, though gradually spreading and twisting out from that over time (over many millions of years a lot of material will end up along most if not all of the orbital path of the comet - see previous lifetime estimate). Jupiter plays a fairly major role in putting kinks into the trail of material and that will result in apparent outbursts (as seen on Earth) from time to time.
Generally: Short period comets (<200 year orbits) tend to come from the Kuiper Belt and are largely constrained to orbit in the plane of the ecliptic (ie same plane as all the planets plus or minus a bit) given the Kuiper Belt is likewise. Longer period comets (>200 year orbits) come from the Oort Cloud so they tend to have widely varying, random inclinations to the ecliptic (since the Oort Cloud is spherically distributed).I didn't actually realise the orbital path truncated the inner solar system, I thought it was on the same plane, that makes more sense in constantly passing through a ring of debris then.