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Minnesota State University, Mankato

Minnesota State University, Mankato

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Getting to know our galaxy

Starline

July 1 brings a partial solar eclipse, the third eclipse of the year and the third we can't see. It will be visible only from part of the Antarctic Ocean, so very few people will see it.

2011-09-08
By Steve Kipp, Minnesota State Mankato Astronomy professor [published in The Free Press, Mankato, MN, 6/29/2011]

July 1 brings a partial solar eclipse, the third eclipse of the year and the third we can't see. It will be visible only from part of the Antarctic Ocean, so very few people will see it.

The Milky Way is that band of light in the sky, and July is a great time to see it. The Greeks imagined that the Milky Way was made by spilled milk from a celestial goddess. Native Americans thought the strip was a dusty path across the sky where buffalo roamed. But when Galileo inspected the Milky Way with a telescope in 1610, he saw that it consisted of uncountable faint stars.

The Milky Way in the sky is a projection of the disk of stars in which we live: the Milky Way galaxy.

To identify the Milky Way in July, start by finding the constellation Scorpius at about 11 p.m. just above the southern horizon. The stars of Scorpius actually look like a scorpion with a curled tail. Scorpius lies directly in the Milky Way. Above and to the left of Scorpius is Sagittarius, the Archer, although the bright stars in Sagittarius make a "teapot" pattern. The center of the Milky Way is in the direction of Sagittarius.

From Sagittarius you can follow the path of the Milky Way to the northeast high in the sky through Cygnus, the northern cross, and down to the northeast horizon. You can see the Milky Way from dark areas in the city, but you will get a much better view from the dark countryside. On July 4 we celebrate Independence Day, but this year we are also celebrating the Earth being at aphelion, the Earth's greatest distance from the sun.

This year the Earth's aphelion distance is 94,555,000 miles, and the perihelion distance (close approach) is 91,445,000 miles. The Earth's orbit is almost circular.

July 12 is Neptune's birthday! The planet Neptune was first observed Sept. 23, 1846, about 165 years ago.

As of July 12 Neptune will have orbited the sun just once since its discovery. On this basis Pluto, discovered in 1930, with a period around the sun of about 250 years, is not yet a year old!

The Delta Aquarid meteors peak July 28-29 with 20 meteors per hour. Watch the sky a few hours before dawn to see the most meteors.

July began with a new moon. A second new moon falls on July 30. The second full moon in a calendar month has come to be called a "blue moon," but there is no special name for the second new moon.

(Steve Kipp is a professor of astronomy at Minnesota State University, Mankato. Questions or comments about the monthly "Starline" column may be sent to Prof. Steve Kipp, 141 Trafton Science Center N, Mankato, MN, 56001, or to steven.kipp@mnsu.edu.)

(For the complete July "Starline" column, see the June 29 print edition of The Free Press, or click on http://mankatofreepress.com/communityindex/x1435406878/STARLINE-Get-to-know-your-galaxy-and-happy-birthday-Neptune)

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