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: Look for Venus and Jupiter very low in the western sky right
after sunset. By 8 p.m., Venus is less than a half a fist above the west
horizon.
Thursday: “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.
Friday: The
most effective learning requires frequent review, especially when first
introduced to a topic. So let’s review triangles. Mars, Saturn, and Antares
form a small triangle one fist above the southwest horizon and just to the left
of the Moon at 9 p.m. Mars, the brightest object is on the far left. Saturn is
one fist to the right of Mars and Antares is less than a fist below Saturn.
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.