মঙ্গলবার, ৩০ এপ্রিল, ২০১৩

Fireballs! 'Tis the season for massive meteors.

Tonight (April 23) through Friday at dawn may be your best chance of the year to spot a fireball, a meteor that shines brighter than Venus, the brightest planet in the sky.

By Joe Rao,?SPACE.com / April 23, 2013

In this picture provided by Wally Pacholka of AstroPics.com, a Geminid fireball explodes over the Mojave Desert in the Jojave Desert, Calif. on Dec. 13, 2009. Unlike this Geminid fireball, the fireball-watching in the next few nights isn't connected to the just-completed Lyriad meteor shower or any other regular meteor shower.

Wally Pacholka / AstroPics.com / AP

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The dramatic fireball that exploded over Russia in February got many people wondering if there is any way to anticipate future dazzling meteors before they appear.

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Well, meteors not associated with an annual shower are certainly tough to predict. But there are some patterns that skywatchers can keep in mind to maximize their chances of spotting a fireball (which technically is any meteor that shines more brightly than Venus in the sky).

For example, springtime is "fireball season," when the number of bright meteor sightings increases by as much as 30 percent, NASA experts say. And the three-day stretch from Tuesday (April 23) to Thursday (April 25) is perhaps the best time to watch for the next prospective fireball event, which might possibly even lead to the fall of a meteorite.?

Over the years, some real dazzlers have been seen during this time frame. And in at least two cases, the orbits of the meteors were virtually identical, suggesting Earth might hit more such space rocks when it passes through this part of its orbit.

A river of rubble?

Is there perhaps a "river of rubble" orbiting the sun that is populated by rather large meteoroids?

Unlike most of the annual meteor showers that are composed chiefly of dust and sand-sized particles ? such as the Lyrids, which peaked overnight Sunday (April 21) ? this supposed fireball stream might be made up of objects that are considerably larger, perhaps originating in the main asteroid belt between Mars and Jupiter or perhaps being shed by the nucleus of a long-dormant comet.?

The circumstantial evidence for such a meteor stream lies with two brilliant fireballs that appeared during the 1960s.

One of these fireballs cast shadows over northern New Jersey on April 23, 1962. The other was seen by thousands of people over England, Wales and Northern Ireland on April 25, 1969 and also dropped a 0.6-pound (0.27 kilograms) meteorite in the town of Sprucefield, Northern Ireland.

Source: http://rss.csmonitor.com/~r/feeds/science/~3/JN_cGf2dRGw/Fireballs!-Tis-the-season-for-massive-meteors

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