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Night Sky

Night Sky

May 2011 Night Sky

—Charlie Christmann

Spring Fireballs

Almost any evening, you can go outside and watch the night sky for meteors. On any given night, you should be able to see about 10 random meteors streaking across the sky. But spring seems to be a great time to look for bright fireballs. According to Bill Cooke of NASA’s Meteoroid Environment Center, “For reasons we don’t fully understand, the rate of bright meteors climbs during the weeks around the vernal equinox.” Over the past 30-some years, astronomers have noticed the nightly rate mysteriously climbs 10 to 30 percent above other times of the year.

According to NASA, 100 tons of meteoroids, fragments of dust and gravel and sometimes even big rocks, enter the Earth’s atmosphere every day. But where does all this stuff come from? Surprisingly, the experts are somewhat puzzled.

There is no rational explanation for the spike in spring meteor rates. There is a point in the night sky called the “apex of the Earth’s way.” That point is the direction our planet is traveling as the Earth circles the sun. You would expect that having this apex overhead at night would increase the rate of debris picked up by our atmosphere and, therefore, cause more meteor streaks in the sky. If Earth were a car, the apex would be the front windshield. When a car drives down a road, insects accumulate on the glass up front. The same idea applies for meteoroids swept up by Earth’s atmosphere.

The apex climbs to its highest point in the night sky each autumn. Yep, I said autumn. There seems to be a problem here. During spring, the apex’s highest point is located in the day-lit sky. Spring evenings are at the anti-apex—or the back window of our car. How many bugs accumulate on the back window?

Meteoroid expert Peter Brown of the University of Western Ontario notes that “some researchers think there might be an intrinsic variation in the meteoroid population along Earth’s orbit, with a peak in big fireball producing debris around spring and early summer.”

Yes, it is a puzzle. So, NASA is setting up a network of cameras to track the brighter fireballs (those brighter than Venus) to try and learn where they originate. Check out http://fireballs.ndc.nasa.gov.

There have been several fireball sightings this year:

  • Jan. 11: Over Louisiana about 8:50 p.m. CST, a green fireball was reported. Similar reports came from Oklahoma to Florida.
  • Feb. 15: Over Pennsylvania about 12:30 p.m. EST, a fireball traveled east for hundreds of miles.
  • March 23: Large fireball reported by 30 witnesses over Texas, Oklahoma, Kansas, Colorado, Arkansas, and New Mexico about 8:15 p.m. MDT.
  • March 30: A bright meteor was reported streaking across Auckland, New Zealand and the upper North Island.
  • April 6: Large fireball reported over Alabama, Tennessee, Kentucky, Maryland, Ohio, and Arkansas about 8:30 p.m. CDT.
  • April 14: At 12:31 a.m. local time, northern Italy saw a bright fireball that ended with an explosion.

The nights are getting warmer, and the skies are clear and bright. Get outside, and add your eyewitness account to the fireball reports.

The Planets and Moon

This is the month to get up before sunrise to see the planets.

  • Check for Mercury rising in the east this month around 5 a.m. On the 18th, use binoculars 20 minutes before sunrise to find Venus one degree above Mercury. Also see Jupiter seven degrees to the upper left of Venus.
  • Venus, too, rises in the east around 5 a.m. this month. Look 20 minutes before sunrise on the 11th to find Jupiter 0.5 degrees above and to the left of Venus. With binoculars, you might also see Mercury 1.5 degrees to the lower right of Venus. A Venus-Moon conjunction occurs 20 minutes before sunrise on the 31st.
  • Mars rises in the east from 5:30 a.m. early in the month to 4:30 a.m. late in the month.
  • Jupiter is a morning riser in the east from 5:15 a.m. early in May to 3:45 a.m. late in May. On the 1st, look 15 minutes before sunrise to see the waning crescent moon just five degrees below Jupiter. If you have binoculars, you might also be able to spot Mars 0.3 degrees to the upper left of Jupiter—DON’T LOOK AT THE SUN! A Jupiter-Moon conjunction happens an hour before sunrise on the 29th.
  • Saturn is the loner this month, high up in the east after sunset. There is a Saturn-Moon conjunction on the 13th.
  • The Moon is new at 12:51 a.m. on the 3rd and full at 5:09 a.m. on the 17th.
     

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