Review 1The Perseids are coming! The Perseids are coming! I'm sure you're already hearing the cry around the world… But what will be the best place to watch and when will be the best date to see the most "shooting stars"? Follow along and let's find out…
The Perseid meteor shower has a wonderful and somewhat grisly history. Often referred to as the "Tears of St. Lawrence" this annual shower coincidentally occurs roughly about the same date as the saint's death is commemorated on August 10. While scientifically we know the appearance of the shooting stars are the by-products of comet Swift-Tuttle, our somewhat more superstitious ancestors viewed them as the tears of a martyred man who was burned for his beliefs. Who couldn't appreciate a fellow who had the candor to quip "I am already roasted on one side and, if thou wouldst have me well-cooked, it is time to turn me on the other." while being roasted alive? If nothing else but save for that very quote, I'll tip a wave to St. Lawrence at the sight of a Perseid!
While the fall rate - the number of meteors seen per hour - of the Perseids has declined in recent years since Swift-Tuttle's 1992 return, the time to begin your Perseid watch is now. While the peak of activity will not occur until August 12 at approximately 11:00 GMT, this will leave many observers in daylight. For those who wish only to observe during the predicted maximum rate, the place to be is western North America and the time is around 4:00 a.m. However, let's assume that not all of us can be in that place and be up at that time… So let's take a more practical look at observing the Perseid Meteor Shower.
For about the last week or so, I've noticed random activity has picked up sharply and traceable Perseid activity begins about midnight no matter where you live. Because we are also contending with a Moon which will interfere with fainter meteors, the later you can wait to observe, the better. The general direction to face will be east around midnight and the activity will move overhead as the night continues. While waiting for midnight or later to begin isn't a pleasant prospect, by then the Moon has gone far west and we are looking more nearly face-on into the direction of the Earth's motion as it orbits the Sun, and the radiant - the constellation of the meteor shower origin - is also showing well. For those of you who prefer not to stay up late? Try getting up early instead!
How many can you expect to see? A very average and cautiously stated fall rate for this year's Perseids would be about 30 per hour, but remember - this is a collective estimate. It doesn't mean that you'll see one every two minutes, but rather you may see four or five in quick succession with a long period of inactivity in between. You can make your observing sessions far more pleasant by planning for inactive times in advance. Bring a radio along, a thermos of your favorite beverage, and a comfortable place to observe from. The further you can get away from city lights, the better your chances will be.
Will this 2000 year-old meteor shower be a sparkling success or a total dud? You'll never know unless you go out and try yourself. I've enjoyed clear skies here for the last week and without even trying caught at least 15 per hour each night I've gone out. One thing we do know is the Perseids are one of the most predictable of all meteor showers and even an hour or so of watching should bring a happy reward!
Wishing you clear skies and good luck…
(cited from Universe Today : Meteor Showers )Review 2:In mid-August each year the Earth is bombarded by thousands of tons of extra-terrestrial debris; the remnants of Comet Swift-Tuttle. But Valdostans need not worry; as these tiny dust particles burn up in the Earth's atmosphere as meteors. This week brings the Perseids, traditionally the finest of the annual meteor showers!
The Perseid meteor shower lasts from August 10th to 13th, peaking after midnight on Wednesday, August 11th. The meteors will radiate from the constellation Perseus, which rises late in the evening in the northeast. Observers need be able to identify Perseus to enjoy this event, however! The Perseid meteors are noted for their long trails and should streak across much of the night sky. One only needs to look towards the northeast after dusk, anywhere from 30 degrees to 80 degrees above the horizon. The best time to observe the Perseids will be after 1:00 am during the morning of August 11th. The morning sky currently features the bright planet Venus, which rises at 2:36 am and is located directly north of the familiar constellation Orion. One can expect to see nearly (but not quite!) as many meteors in the evening sky, before midnight.
The best place to observe the Perseid meteors is in an open area (a field, a golf course, etc.) that is unobstructed by trees or other structures, and which is far from city lights. The darker the sky the better! Because meteors are not amenable to telescopic observation, and because Nevins Hall is currently undergoing renovation, the VSU Observatory will not be open for this event.
One last bit of astronomical nomenclature! The tiny fragments of rock and dust which have evaporated off the nucleus of Comet Swift-Tuttle (last seen in 1862), and which continue to orbit the Sun, are known as meteoroids. Those that encounter the Earth each August enter the atmosphere at high speed (typically 10-30 miles per second) and burn up as a result of air friction. These are the meteors we see in the night sky! Should any fragments survive the fall to Earth the impacting objects will become meteorites; this is however extremely unlikely!
(cited from Perseid Meteor Shower)Bahan Diskusi:Hujan meteor Perseid diketahui akan berlangsung dari tanggal 10 hingga 13 Agustus 2008. Hujan meteor ini disebabkan Bumi melewati sisa komet Swift-Tuttle. Coba perkirakan tebal lapisan sisa komet Swift-Tuttle ini!
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So what can we expect this year? According to NASA's 2009 predictions a significant shower is expected this year when Earth crosses the 1466-dust and 1533-dust ejecta of comet 55P/Tempel-Tuttle. According to J. Vaubaillon, the narrow (about 1-hr) shower is expected to peak on November 17, 2009, at 21:43 (1466) and 21:50 (1533) UT, perhaps 0.5 to 1.0 hour later based on a mis-match in 2008, with rates peaking at about ZHR = 115 + 80 = 195/hr (scaled to rates observed in 2008). E. Lyytinen, M. Maslov, D. Moser, and M. Sato all predict similar activity from both trails, combining to about ZHR = 150 – 300 /hr. P. Jenniskens notes that if the calculated trail pattern is slightly shifted in the same manner as observed before, then the 1533-dust trail would move in Earth's path and its rates would be higher (the 1466-dust trail would move away). However, the 1533-dust trail is distorted in the models, and because of that it is not clear how much higher that would be. This remains a rare opportunity to study old dust trails from comet 55P/Tempel-Tuttle. In such old trails, the model of Lyytinen and Nissinen predicts wide trails, which can be tested by measuring the width of the outburst profile.
Let's take a closer look at the at how the two centuries old trails will affect our observing, beginning with the one created in the year 1466. The exact same trail will be encountered again this year with its maximum rate of up to 115 meteors per hour occurring at 21:43 UT (may be 0.5-1hr later). "The trail will be much closer to the Earth, explaining why we expect a quite high zenith hourly rate." say J. Vaubaillon (et al), "However the discrepancy between the expected time of maximum remains, as well as a general higher expected ZHR. Among the possible explanations are: sensitivity to initial conditions (given that the trail is 16 Rev. old) or change of cometary activity (impossible to verify unfortunately)."
But don't count on only this single trail, because the year 1533 trail will encounter the Earth at almost the same time as the 1466 trail. Its maximum time of arrival is expected to be at 21:50 UT on the 17th of November, with a zenith hourly rate of 80 – for a combined rate of perhaps 200 meteors per hour. "The total level of the shower (ZHR~200/hr) was callibrated using the 2008 observations of the 1466 trail, but nothing is known from the 1533 trail. As a consequence, it will be very interesting to check." comments Vaubaillon, "In particular there might be a difference of up to 1 hour between the 1466 and 1533 trail, or they might even be late together, giving us some insight about how well/poorly we know comet 55P's orbit."
One of the most identifiable nebulae in the sky, the Horsehead Nebula in Orion, is part of a large, dark, molecular cloud. Also known as Barnard 33, the unusual shape was first discovered on a photographic plate in the late 1800s. The red glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis. A blue reflection nebula surrounds the bright star at the lower left. The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left. Streams of gas leaving the nebula are funneled by a strong magnetic field. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming. Light takes about 1500 years to reach us from the Horsehead Nebula. The above image was taken earlier this month with a 0.6-meter telescope at the Mt. Lemmon SkyCenter in Arizona, USA.
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