raben.com

The following is discussion of some astronomical objects that may be seen in the sky this week,
August 31 to September 6, 2008.

International Space Station

The International Space Station is visible in the Denver area Sunday through Friday in the early
morning this week. Most passes are low in the northern sky and very brief. The best passes this
week are:

Mon. Sept. 1 at it appears in the north at 4:35 am and disappears in the northeast at 4:37
am. It will reach magnitude -0.8

On Tuesday it appears at 5:01 am in the northwest and disappears in the north-northeast at 5:03
am. It will reach magnitude -0.1 on that pass.

The times the space station is visible vary widely so check with www.heavens-above.com for your location.

Sun

On Sunday Aug. 31 sunrise is at 6:30 am and sunset is at 7:36 PM mdt

On Saturday Sept. 6 sunrise
is at 6:36 am and sunset is at 7:26 pm mdt

Aerosols from the eruption of the Alaskan volcano Kasatochi earlier this month are the cause of
some recent spectacular sunrises and sunsets. Take a look and enjoy!

There are no active regions visible on the solar disk as of Sunday evening.

For more information about solar activity see www.swpc.noaa.gov

Moon

The moon is at lunation 1 on Sunday but will be not be visible as it sets only a few minutes
after sunset. You might be able to spot it on Monday evening just after 8pm. It will appear as a
very thin crescent, low in the west below and to the left of Venus. Tuesday and Wednesday it will
be a pretty view with earth shine illuminating the moon's night side. On Saturday it is at lunation
7.2. It will be at first quarter next Sunday, Sept. 7 at 8:04 am mdt.

Planets

Mercury, Venus, and Mars form a triangle low in the bright twilight in the western sky after
sunset this week.

Jupiter is straight south around 9 PM in constellation Sagittarius. It sets 1:57 am Sunday and
1:33 am on Saturday Jupiter's great red spot crosses the center of the disk at the following times
this week:
Sun evening Aug. 31 at 8:30 PM
Tues. Sept. 2 at 10:08 PM
Thurs. Sept. 4 at 11:47 PM
Fri. Sept. 5 at 7:38 PM

Neptune is constellation Capricorns. It is magnitude 7.8 in brightness and its disk is only 2.4
arc sec across. It is 29.1 a.u. or 2.7 billion miles away.

Uranus is in constellation Aquarius. It is magnitude 5.7 in brightness and its disk is 3.7 arc sec
across. It is 19.1 a.u. or 1.8 billion miles away

Dark Sky

The moon sets around 10:45 PM by the weekend so there is still time for some late evening dark
sky viewing.

High overhead in a constellation called Lyra is a planetary nebula known
as the "Ring Nebula" or M57. Planetary nebula consist of clouds of ionized gas primarily hydrogen
and oxygen. The gases are ejected due to pulsations and instability during the final stages of the
star's life. As the star collapses it emits intense ultraviolet radiation which causes the
surrounding gases to fluoresce. The reddish color is from the ionized hydrogen and the greenish
color is from ionized oxygen. Through the telescopes you will see a round grayish-white ring; the
colors will not be visible. Our eyes are not sensitive to colors at low light levels.

Also visible is another planetary known as the "Dumb bell" nebula or M27 in the
constellation Vulpecula. Through the telescopes you will be able to see the hour glass or dumb
bell shape but not the colors unfortunately.

Another showpiece is M13 a globular cluster in the constellation Hercules. A globular cluster is a
spherical collection of stars tightly bound by gravity and orbiting a common center. They contain
from tens of thousands to perhaps as a many as a million stars. The Hercules cluster is estimated
to contain several hundred thousand stars. It is estimated to be 25,100 light years from Earth and
145 light years in diameter. This is a great object to view on a clear, dark night. Through a
telescope it appears like a sparkling, three dimensional disco ball.

Comets

The easiest to locate is comet 6P d'Arrest in constellation Microscopium. It is magnitude 8.9 in
brightness and has 2 arc min wide coma.

C/2006 W3 Christensen is in constellation Camelopardalis. Ephemeris puts the at magnitude 12.9 and
1 arc min coma.

C/2008 J1 Boattini is in constellation Ursa Minor. It is magnitude 11.3 in brightness and coma is
4 arc min across.

C/2006 OF2 Broughton is in constellation Camelopardalis as well. It is magnitude 11.2 and coma is
2 arc min across.

Summary

This week you might view some spectacular sunsets, view the ISS in the early morning, and see
beautiful earth shine on the moon. Get out your telescope and watch Jupiter's great red spot
crosses the planets disk, view some dim comets and take a look at summertime celestial showpieces
M13, M57, and M27.