* Astronomy

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RE: April 2008

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Amateur Astronomy - Sky this Week Apr 20-26, 2008

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Earth Day

www.nature.org/earthday/

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Credit SOHO/NASA

Mercury 16:18 UT, 19th April 2008

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Mercury just passed superior conjunction on April 16, but in the days to come it will bolt out to become easily visible low in the west-northwest at dusk. On Wednesday evening, April 23, Mercury should be visible within about 30 minutes after sunset if your sky is quite clear.
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21:07 UT, 23rd April 2008

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With spring right around the corner it is the season for auroras. The beautiful and mysterious auroras are spectacular to watch, but they are actually a manifestation of violent space weather. This weather can create big problems here on Earth by disrupting power grids, satellites, air travel and even GPS signals.

NASA: The Mystery of the Aurora

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While auroras have fascinated observers for centuries, little had been known about their origin. But NASA is aiming to resolve this mystery with a new mission called THEMIS.

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Tonight's Sky: April 2008

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On April 8th, a 12% crescent Moon will be close to the Pleiades star cluster in the western evening sky.
The Pleiades, also known as the Seven Sisters, are a young star cluster the lies 400 light years away.

The event, shortly after sunset (roughly 8:30 P.M. local time), is best viewed through binoculars.
The best location will be in the Americas.
The Moon will set shortly after 11 P.M. local time.

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Comets

46P/Wirtanen

Comet 46P/Wirtanen is brightening as it travels through Pisces this month. The comet passes close to the spiral galaxy NGC 524 on February 4 - 5.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase   m1 
2008 04 04    06 05.23   +35 03.0    1.133    1.330    76.9    47.1  11.1
2008 04 09    06 29.90   +35 10.1    1.182    1.368    77.1    45.5  11.4
2008 04 14    06 53.51   +34 59.5    1.235    1.407    77.2    44.0  11.7
2008 04 19    07 15.91   +34 33.6    1.292    1.447    77.0    42.5  12.0
2008 04 24    07 37.05   +33 55.2    1.353    1.488    76.7    41.1  12.2
2008 04 29    07 56.93   +33 06.6    1.418    1.530    76.1    39.7  12.5

8P/Tuttle

The comet is starting to fade rapidly....

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase   m1 
2008 04 04    04 59.55   -60 50.8    1.183    1.435    81.7    43.6  11.5
2008 04 09    05 17.70   -61 35.3    1.208    1.483    83.8    42.2  11.8
2008 04 14    05 37.73   -62 15.1    1.232    1.533    85.9    40.8  12.2
2008 04 19    05 59.62   -62 48.8    1.256    1.583    88.1    39.4  12.5
2008 04 24    06 23.31   -63 14.9    1.280    1.633    90.4    38.0  12.8
2008 04 29    06 48.62   -63 31.4    1.305    1.684    92.6    36.7  13.1

Comet 17P/Holmes

The comet is faint..

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase   m1 
2008 04 04    04 40.70   +36 41.2    3.496    3.123    60.3    16.1  20.1
2008 04 09    04 48.60   +36 31.9    3.575    3.144    57.0    15.5  20.2
2008 04 14    04 56.59   +36 22.7    3.652    3.166    53.8    14.8  20.3
2008 04 19    05 04.64   +36 13.4    3.728    3.187    50.7    14.1  20.4
2008 04 24    05 12.73   +36 03.9    3.801    3.209    47.5    13.4  20.5
2008 04 29    05 20.85   +35 54.1    3.871    3.230    44.4    12.6  20.6

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Meteor Showers
This month sees the arrival of the Lyrids and the Virginids. Neither shower is very intense, but they do provide you with examples of shooting stars with different speeds: the fast Lyrids compared to the slower Virginids.

The peak of the April Lyrids (from the constellation of Lyra, the Harp) is on the 22nd, 5::00 UT, when you could see a maximum of about 15 meteors an hour. A near Full Moon will interfere with the Shower.
The Virginids are active until the 18th, peaking on the 11th with 10 meteors an hour. Unfortunately the light of the nearly Full Moon will also washout most of the meteors.
Watch out for sporadic meteors. Their rates for the Northern Hemisphere are now reaching a plateau. Expect around 12 random meteors per hour during the morning hours

You can listen to them by tuning to the 67 MHz meteor radar in Roswell, NM.

Shower	Activity Period	Maximum	Radiant		Velocity	ZHR
		Date	R.A.	Dec.	km/s
Gamma Virginids	Jan 25 to April 15	Apr. 11	195°	-04°	33	4.6
Lyrids	April 19 - 25	Apr22 23 UT	271°	+34°	49	15
Pi Puppids	April 18-25	Apr23	110°	-45°		18
	for UK (A.Smith)	Radio Meteor Observation Station Track