Don't forget to get ready for Perseid Below on August 13, 2012

2012 August 10
Perseid Below
Credit: Ron Garan, ISS Expedition 28 Crew, NASA

Explanation: Denizens of planet Earth watched last year's Perseid meteor shower by looking up into the bright moonlit night sky. But this remarkable view captured on August 13, 2011 by astronaut Ron Garan looks down on a Perseid meteor. From Garan's perspective onboard the International Space Station orbiting at an altitude of about 380 kilometers, the Perseid meteors streak below, swept up dust left from comet Swift-Tuttle heated to incandescence.

The glowing comet dust grains are traveling at about 60 kilometers per second through the denser atmosphere around 100 kilometers above Earth's surface. In this case, the foreshortened meteor flash is right of frame center, below the curving limb of the Earth and a layer of greenish airglow, just below bright star Arcturus.

Want to look up at this year's Perseid meteor shower? You're in luck. This weekend the shower should be near its peak, with less interference from a waning crescent Moon rising a few hours before the Sun.

PHOTOS

http://www.amsmeteors.org/wp-content/uploads/2012/08/PER-22001.jpg1.jpg

TO VIEW THE PERSEID

Viewing the 2012 Perseid Meteor Shower
By Robert Lunsford, in Meteor Showers

Examples of Perseid meteors as seen at 10pm local daylight time while facing northeast.

Perseid meteors can be seen from anywhere in the northern hemisphere during the month of August. They can be seen during the late evening hours but are best seen between midnight and dawn. The shower is compromised in early August by the full moon. Since most of the Perseid meteors are faint, the bright moonlight will obscure them. The moon will remain a problem right up to the date of maximum activity, which is expected to be on the morning of August 12th. By the 12th though, the moon will only be 25% illuminated and not nearly as intense as when near its full phase. This will allow fainter meteors to be seen as long as the moon lies outside your field of view.

The weekend of August 11/12 will be prime viewing time for the Perseids. One can view on earlier dates but the rates will be less and the moon more of a problem. On Saturday morning, August 11th, the 35% illuminated moon will rise near 0100 local daylight time (LDT) for observers located in the mid-northern latitudes. The moon will be located in central Taurus, mid-way between the bright orange star Aldebaran and the naked eye star cluster known as the Pleiades. This position lies only 30 degrees from the Perseid radiant, which lies in the northern portion of the constellation Perseus. The radiant is the area of the sky these meteors appear to shoot from. You should center your view more to the north or in the opposite direction to avoid seeing moonlight, which will impair your night vision. Perseid meteors will be visible as soon as it becomes dark on Friday evening, but at only rates of 5 per hour. This is due to the fact that the Perseid radiant lies low in the north at this time and only a small percentage of the activity can be see. See the difference in the position of Perseus in the two illustrations. Meteors from other minor showers plus random activity can be seen at this time of night raising the total to near 10 per hour.

Examples of Perseid meteors as seen at 4am local daylight time while facing northeast.

With each passing hour the Perseid radiant rises higher into the northeastern sky. The hour before the first hint of morning twilight should produce the best rates, which should be near 25 per hour on Saturday morning for observers with transparent skies. Those who have to view under hazy skies will probably only see half this total. On Saturday evening Perseid rates should be 5-10 per hour. On Sunday morning the moon will have moved eastward and is now located in eastern Taurus, some 10 degrees below the bright planet Jupiter, which lies just 5 degrees north of Aldebaran. It is now 25% illuminated and will rise between 0100 and 0200 LDT. It is now 40 degrees away from the Perseid radiant but still too close to the radiant to view in that direction. For observers with clear, transparent skies, I would expect rates of near 40 Perseids per hour this morning. Again, those with hazy skies will only see half this amount.

The evening of the 12th may provide up to 10 Perseids per hour. On Monday morning the 13th, the 18% illuminated moon will lie just above the brilliant planet Venus and will rise near 0200 LDT. In fact later on that afternoon, the moon will actually pass in front of Venus for those situated in North America. Meanwhile, the Perseids are expected to be slightly weaker on Monday morning with perhaps 30-35 shower members appearing each hour. Beyond the 13th, the moon becomes a non-factor but unfortunately the Perseid rates fall precipitously with less than 5 shower members appearing each hour by the weekend of the 18/19.

There is no need to ask about circumstances for your particular location as the times and dates are good for all locations in North America. For Europe and Asia, the moon’s location will be slightly different but the general circumstances are much the same. If you live south of the equator then that is another matter. The Perseids are not well seen in the southern hemisphere. If you examine the chart for the southern hemisphere you will notice that Perseus is located just above the northern horizon. This is as high as it gets from latitude 25 south. Some activity can be seen shooting upwards, but it is only a fraction of what can be seen in the northern hemisphere with the radiant high in the sky.

Perseids as seen facing north before dawn from the southern hemisphere

All Perseid meteors will shoot from the area of Perseus. You can verify this by tracing the path backwards. If the path intersects northern Perseus then you can be certain it was a member of the Perseid shower. While most Perseid meteors will appear swift, one cannot base shower association on velocity alone. Perseids that appear near the radiant are moving toward you and therefore will appear to move slower than those further away from the radiant. The fastest and longest Perseids will occur about 90 degrees away from the radiant. Perseids seen close to the horizon are moving away from you and will also appear to travel slower than those seen higher in the sky.

Unless you are comfortable, most people are going to be disappointed with the show. If you are serious about seeing meteors then get comfortable in a lounge chair. There will be times when no activity will appear for 5 minutes and then 10 meteors will suddenly appear in the same time span. You may go outside and stand for 5 minutes and not see a thing. You need to get comfortable and watch as long as possible so that you may witness the peaks of activity along with the droughts. Really serious folks will hop in the car and head for dark skies away from the city. This will certainly increase the activity you will see as the fainter meteors become visible. If you are really crazy, then you will count the number of Perseids you see each hour and report it to other crazy people like us at the AMS. It may be crazy, but it is fun to watch natures fireworks. It is also scientifically useful to record this activity as it can reveal the particle density in outer space and help us predict what may occur in the years to come.

If you have any questions, shoot them my way and I will answer the asap.

Clear Skies!
Robert Lunsford
American Meteor Society