The International Meteor Organization (IMO) was founded in 1988 and has more than 250 members now. IMO was created in response to an ever growing need for international cooperation of meteor amateur work. The collection of meteor observations by several methods from all around the world ensures the comprehensive study of meteor showers and their relation to comets and interplanetary dust.
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August brings arguably the best meteor shower of the year – the Perseids. The large numbers of bright, colorful meteors, holidays and warm summer nights make this one of the best celestial shows of the year. Pack your gear, drive under dark skies and enjoy the spectacle!
The activity graph below is updated every 15 minutes - click for details.
The Perseids are one of the strongest annual meteor showers. As most other meteors, the Perseids are caused by small dust particles called meteoroids. Meteoroids usually originate from comets. As a comet revolves around the Sun it periodically heats up and ices on its surface begin to sublimate, releasing tiny mineral grains and clumps which were trapped in the ice. During tens to hundreds of successive revolutions around the Sun, a comet produces a long stream of meteoroids. If the Earth passes through this stream, meteoroids bombard our atmosphere, hitting it at tens of kilometers per second and creating beautiful streaks of light we know as meteors.
The Perseids are caused by the meteoroids from the periodic comet 109P/Swift-Tuttle, which revolves around the Sun every 130 years. The Perseids have been observed for centuries, but were officially recognized as a major meteor shower in the middle of the 19th century. They have been regularly observed for the past 150 years and are best known for a series of strong outbursts in the first half of the 1990s, which reached ZHRs up to about 500 meteors per hour.
Perseid meteoroids hit our atmosphere at 59 km/s, so the Perseids are swift meteors and often very colorful. Many brighter shower members leave persistent trains. Fireballs may leave persistent trains that last for tens of seconds or even minutes! Interestingly enough, the meteoroids that cause ordinary bright Perseids are only a few millimeters across! Even the meteoroids that produce fireballs are only centimeters across.
The Perseids all appear to radiate from (fly out of) a point – the radiant – in the constellation of Perseus. The radiant drifts eastward each successive night. At the beginning of the shower's activity it is located in the western part of Cassiopeia, drifting through it and into Perseus by early August and towards the border with Camelopardalis in late August. Check the radiant position before observation.
Perseid radiant drift from mid July to late August. Radiant positions are marked for every 5 days.
The first Perseids appear in mid July, but the shower begins picking up strength in the first week of August. By August 7 you may be able to see about 10 to 15 Perseids per hour just before dawn, if your sky is dark. By August 10 the rate increases to about 20-30 Perseids per hour. On the peak night, August 12/13, the rate will reach 80-100 meteors per hour! The numbers then decline by half every night, so the night after the peak you may see about 40-50 meteors per hour and on August 14/15 there will be about 25-30 Perseids per hour. The final Perseids may be seen around August 25. These rates are expected under dark skies - light pollution will diminish the number of meteors significantly.
Position of Perseid radiant on August 13 at 3 am from 45°N, looking east.
But the rate also changes during the night. As the radiant rises, so does the number of meteors! The radiant is at its lowest during the evening hours and climbs high in the sky in the morning. The final hour before dawn will usually produce the most Perseids. So do persist until dawn!
Also remember that the Perseids are not the only active meteor shower in this period. Other active showers include the Kappa Cygnids, Southern delta Aquariids and Alpha Capricornids. Check the 2015 IMO Shower Calendar for more information.
To observe the Perseids, you need to dress warmly, bring a reclining chair and watch the sky. You need no other equipment. Find a dark observing spot, preferably with a low horizon and look in any (the darkest) direction.
Use this light pollution map to find dark locations near you.
But you can also contribute valuable observational data! If you decide to do so, use the IMO major meteor shower observing technique. This way your data will be in a standard format, that can readily be used for analysis. Send us your data as soon after the observations as possible.
The 2015 Perseids are expected to be above average. While their average annual ZHR is in the 80 – 100 range, some years are significantly better than that. With the Perseids an increase in activity is caused by one of the following two factors: 1) an encounter with a young dust trail or 2) a favourable gravitational perturbation by Jupiter and/or other planets, which shifts the center of the meteoroid stream earthwards.
Theoretical modelling by Jérémie Vaubaillon indicates a close encounter with the 1862 (1-rev) dust trail at only 0.00053 a.u. (80 000 km) from the Earth at 18h39m UT on August 12th (IMO Shower Calendar 2015). This is certainly a significantly close encounter, however, being 23 years behind the parent comet the activity levels are very uncertain. Any increase in activity caused by this encounter will last several hours centered on the peak time. In comparison, the same 1862 dust trail was also encountered in 2004, at 0.00132 a.u. distance. It caused a 2-hour outburst with peak ZHR ~200, dominated by faint meteors. That encounter, however, was only 12 years behind the parent comet.
In addition to the 1-rev dust trail encounter, it is highly likely that this year the overall activity of the Perseids will be somewhat elevated due to a favourable gravitational perturbation by Jupiter. The annual peak is expected on August 13 between 6h30m and 9h00m UT, however, variability found in the annual peak timing indicates the peak may occur any time between 1h30m and 14h00m UT on August 13. The maximum enhancement by this effect is expected in 2016 and 2017.
The June 2015 issue of the IMO Journal is now in print. It will be mailed shortly and subscribers can also immediately access the journal in PDF format. The contents this month:
Front cover photo: Bright fireball recorded by the Hiroshima University allsky camera on 2015 May 18. Photo courtesy: Koji S. Kawabata, Hiroshima University.
The April 2015 issue of the IMO Journal is now in print. It will be mailed shortly and subscribers can also immediately access the journal in PDF format. The contents this month:
Front cover photo: Bright fireball over the Atacama Large Millimeter/submillimeter Array (ALMA) in the Chilean Andes. Credit: ESO/Christoph Malin.
Seven witness near Zurich reported a rumbling boom sound shortly after the fireball appeared. A witness outside of Zurich described the boom by saying, "About two minutes after the fireball there was a considerably strong sonic boom.
The February 2015 issue of the IMO Journal is now in print. It will be mailed shortly and subscribers can also immediately access the journal in PDF format. The contents this month:
Front cover photo: Bright meteor on 2013 August 24 at 22h30m UT from Jura mountains, Switzerland. Photo courtesy: Jonas Schenker.