Friday, 5 August 2016

The Perseid Meteors.

The Perseid Meteor shower lasts from late July to early September each year, and are expected to be at a peak on Thursday 11- Friday12 August 2016. The Moon is expected to be quite bright on that night, however it will be setting at about 1.00 am local time on 12 August (this will b the same wherever you are on Earth), which should mean could viewing from most parts of the globe. The shower is expected to be particularly intense this year, possibly reaching 80-150 meteors per hour. The Perseids get their name from the constellation of Perseus, in which the meteors have their radiant (the point from which they appear to originate), which will be rising at about 10.00 pm local time on 11 August.

 The radiant of the Perseid Meteors. National Astronomical Observatory of Japan.

The shower is caused by the Earth passing through the trail of the Comet 109P/Swift-Tuttle, and encountering dust from the tail of this comet. The dust particles strike the atmosphere at speeds of over 200 000 km per hour, burning up in the upper atmosphere and producing a light show in the process. 

The Earth does not need to pass close to 109P/Swift-Tuttle for the meteor shower to occur, it simply passes through a trail of dust from the comet's tail that is following the same orbital path. Comet 109P/Swift-Tuttle itself only visits the Inner Solar System once every 133 years, last doing so in 1992. It is currently 36.4 AU from the Earth (i.e. 36.4 times as far from the Earth as the Sun, more than twice the distance between Neptune and the Sun) on an eccentric orbit tilted at 113° to the plane of the Solar System (or 67° with a retrograde orbit - an orbit in the opposite direction to the planets - depending on how you look at it), that takes it from 0.95 AU from the Sun (95% of the distance at which the Earth orbits the Sun) to 51.22 AU from the Sun (51.22 times as far from the Sun as the Earth, more than three times as far from the Sun as Neptune and slightly outside the Kuiper Belt, but only scraping the innermost zone of the Oort Cloud).

 The orbit of 109P/Swift-Tuttle. Note that this is almost entirely below the plain of the Solar System. JPL Small Body Database Browser.


109P/Swift-Tuttle is currently 36.4 AU from the Sun (i.e. 36.4 times as far from the Sun as Earth and some way outside the orbit of Neptune) ans 37.2 AU from the Earth. The comet is next expected to visit the Inner Solar System in 2126, reaching about 22 950 00 km  (0.15 AU) from Earth in August of that year.

See also...

http://sciencythoughts.blogspot.co.uk/2016/05/the-eta-aquarid-meteors.htmlThe Eta Aquarid Meteors.                              The Eta Aquarid Meteor Shower will peak before dawn on Thursday 5 and Friday 6 May 2016, with up to 45 meteors per hour at it's peak, radiating from the constellation of Aquarius. This does not spend long above the horizon in the Northern Hemisphere at...
http://sciencythoughts.blogspot.co.uk/2016/04/bright-fireball-meteor-seen-over.htmlBright fireball meteor seen over Southern California.                                                    The American Meteor Society has received reports of a bright fireball meteor being seen over much of southern California slightly at about 9.30 pm local time on Monday 23 April 2016 (about 4.30 am on...
http://sciencythoughts.blogspot.co.uk/2016/04/lyrid-meteors-to-be-visible-next-week.htmlLyrid Meteors to be visible next week.         The Lyrid Meteors will be visible between Saturday 16 and Monday 25 April 2006, with peak acticity on Friday 22 April, when the number of meteors may exceed 20 per hour. However with the Full Moon also falling on... 
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