quinta-feira, 9 de agosto de 2012

Perseid meteor shower this weekend

The annual Perseid meteor shower is this weekend. You can expect to see up to one meteor each minute streaking across the sky. Meteors are tiny fragments of minerals that burn up upon hitting our atmosphere. Some Meteorites can be comprised up of minerals rich in silicon and oxygen. Other meteorites consist mainly of iron and nickel, while some are combinations of all four elements. Most are surprisingly tiny about the size of a grain of rice. They burn up in our atmosphere 30-60 miles above the surface of the earth. If a meteor does make it all the way to the ground, we call it a meteorite.

We often hear about a meteor shower occurring on one or two nights. The reality is that these shows begin way before they peak. This week the Perseid's are at their maximum on the night of the 11th and early morning of the 12th. You will, if it's clear and you get away from light pollution, be able to see shooting stars tonight and through the weekend. These pieces of debris are hurling trough space at 37 miles per second or about 133,200 miles per hour. At this speed they could cross the entire country in under 2 minutes. Not all meteors travel at the same speed. A fast meteor could go from the earth to the moon in about a minute and a half. That isn't as fast as the speed of light of course. If someone turned on a light on the moon you would see it a second and a half later here on earth.

Saturday and Sunday nights the moon will be in a waning crescent phase, therefore moonlight won't hamper viewing. The meteors tend to streak across the sky, but you will want to look toward the Perseus constellation, which is in the northeast part of the sky and forms an inverted "Y" shape. In the southern hemisphere you will have to look just above the northern horizon to see the meteors.

What to expect
If you are watching the show with kids you can have them try to find a satellite while waiting for a meteor. Satellites are quite easy to spot as they look like shooting stars but move across the sky at a much slower speeds. It can take a minute or more for a satellite to cross your field of view. I use the opportunity to talk about the earth, orbits and other planets to children during these events. On Saturday the 11th, leading into the 12th, expect about 25-60 meteors per hour. You won't see the meteors evenly spread out over time. You may see nothing for five minutes and then four or more in a row a minute later. Lie on a blanket and look up rather than stand. If you stand with your neck tilted up, you will have neck issues in the morning. On Sunday night, heading into the morning of the 13th there will be fewer meteors per hour, but still a nice show. The best time to see this will be around 2AM-3AM, but if you don't want to wait till then it's still worthwhile once it gets dark.

Fonte: Boston.com

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