Saturday: The
Ellensburg Rodeo is a “Top-25” rodeo. What does it take to be a “Top-25” star?
There are many ways to rank stars. The most obvious way for a casual observer
to rank stars is by apparent brightness. The apparent brightness is the
brightness of a star as seen from Earth, regardless of its distance from the
Earth. Shaula (pronounced Show’-la) is the 25th brightest star in the nighttime
sky as seen from Earth. It represents the stinger of Scorpius the scorpion. In
fact, Shaula means stinger in Arabic. Shaula has a visual brightness rating of
1.62. Sirius, the brightest star has a visual brightness rating of -1.46.
(Smaller numbers mean brighter objects.) The dimmest objects that can be seen
with the naked eye have a visual brightness rating of about 6. There are
approximately 6,000 stars with a lower numbered visual brightness rating than 6
meaning there are 6,000 stars visible to the naked eye. Shaula is a blue
sub-giant star that radiates 35,000 times more energy than the Sun. It is 700
light years away making it one of the most distant bright stars. Shaula is a
challenge to find because it never gets more than a half a fist above the
horizon. Look for it tonight about a half a fist held upright and at arm’s
length above the south horizon, a little bit west of due south, at 8:30.
Sunday:
School starts this week so it is time for a little geometry review. A square is
a regular quadrilateral, which means it has four equal sides, four equal
angles, and it uses the restroom on a set schedule. Go outside at 10 p.m.
tonight with notebook in hand to sketch one. The Great Square of Pegasus is
balancing on its corner two and a half fists above due east. The top corner of
the square is two fists above the bottom corner. The other two corners are to
the left and right of the line segment connecting the top and bottom corners.
Monday:
Labor Day was the brainchild of labor unions and is dedicated to American
workers. The first Labor Day was celebrated in 1882. The Greek mythical hero Hercules
probably wished there was a Labor Day to commemorate his work. As punishment
for killing his family while he was temporarily insane, he had to perform
twelve nearly impossible tasks such as killing monsters or stealing things from
deities. Hmmm. Maybe we shouldn’t commemorate his labors. But we can enjoy his
constellation. The keystone asterism representing the body of Hercules is six
fists above the west horizon at 10 p.m. For more information about the Labors
of Hercules, go to http://goo.gl/ozVF5.
Tuesday:
Geometry review, part 2. Go outside at 10 p.m. tonight with notebook in hand.
(Good teaching involves a little repetition.) You’ll have an easy time seeing
your notebook because the moon is just a little past full. A triangle is a
polygon with three corners and three line segments as sides. A good example is
the Summer Triangle made up of the bright stars Vega, Deneb and Altair. Vega,
the brightest star in the triangle, is a little bit southwest of straight overhead.
Deneb is a little bit east of straight overhead and Altair is five fists above
the south horizon.
Wednesday: Jupiter is less than one fist above the west-southwest horizon at
8 p.m. Saturn is two fists above the south horizon.
Thursday: Venus is two fists above due east at 6 a.m. But the more
interesting sight is to the lower left of Venus, halfway to the horizon.
Mercury, Regulus, and Mars make a little line less than a half a fist long.
Mercury is the brightest objects and is in the upper right. Mars is the dimmest
in the lower left.
Friday: “I’m
a little teapot, short and stout. The galactic center, I pour it out.” (I’m a
Little Teapot, astronomy version, 2014.) Despite its great size and importance,
the center of our Milky Way galaxy and its giant black hole remains hidden to
the naked eye behind thick clouds of gas and dust. By plotting the orbits of
stars near the middle of the galaxy, astronomers have determined that the black
hole’s mass is equal to about 4.5 million Suns. While you can’t see the actual
galactic center, you can gaze in the direction of the center by looking just to
the right of the teapot asterism in the constellation Sagittarius. This point is
about one fist above the south-southwest horizon at 9 p.m.
The
positional information in this column about stars and planets is typically
accurate for the entire week. For up to date information about the night sky,
go to http://nightsky.jpl.nasa.gov/planner.cfm.
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