The Ellensburg WA sky for the week of 6/29/19

Today:  Mercury and Mars are merrily meandering a half a fist held upright and at arm’s length above the west-northwest horizon at 9:45 tonight. Mercury is a little to the left of Mars and is the brighter of the two.

Sunday: Happy Asteroid Day (http://www.asteroidday.org/), the day we celebrate avoiding the destruction of the Earth by an undiscovered asteroid. There are a million asteroids in the Solar System with the potential to strike Earth and destroy a city. Astronomers have discovered only 1% of them. Asteroid Day is an effort to educate the public and encourage policy makers to fund this important effort. King Tut may have celebrated an ancient Asteroid Day by asking his assistants to make a dagger out of a broken-off asteroid that landed on Earth. Astronomers discovered that the blade of the knife contained much more nickel than is found in terrestrial iron, an amount consistent with iron meteorites, especially with one found in the year 2000 in the Kharga region in northern Egypt. For more information about the dagger, go to http://goo.gl/BHBivd.

Monday: Jupiter is two fists above the south horizon at 11 p.m. At this same time, Mars is one fist above the southeast horizon.

Tuesday: This is a good time of the year to find the Big Dipper. The handle is nearly straight overhead at sunset. The cup is in the northwest sky. You can always use the Big Dipper to find some other bright stars. First, follow the curve, or arc, of the Big Dipper down three fists into the southern sky. This is the bright star, Arcturus, the second brightest night time star we can see in Ellensburg. Next, continue on a straight line, or spike, another three fists down toward the south horizon to the star Spica. Spica is the tenth brightest nighttime star we can see in Ellensburg. It is known as the Horn Mansion, one of 28 mansions, or constellations, in the Chinese sky. You now know how to use the Big Dipper handle to “arc” to Arcturus and “spike” to Spica.

Wednesday: Hot enough for you? Don’t blame the Earth-Sun distance. Surprisingly, the overall temperature of the Earth is slightly higher in July, when the Earth is farthest from the Sun, than in January, when it is closest. That’s because in July, the Northern Hemisphere is tilted towards the Sun. (This is the real cause of the seasons.) The Northern Hemisphere has more land than the Southern Hemisphere. Thus, in July, the large amount of Northern Hemisphere land heats up the entire Earth about two degrees Celsius warmer than in January. In January, the watery Southern Hemisphere is tilted toward the Sun. But, water does not heat up as fast as land so the Earth is a few degrees cooler. The distance between the Earth and the Sun is its greatest tomorrow, 152.1 million kilometers. This is called aphelion from the Greek prefix “apo” meaning “apart” and Helios, the Greek god of the Sun.

Thursday: When it is sitting low in the western sky, many people mistake the star Capella for a planet. It is bright. It has a slight yellow color. But, Capella is compelling on its own, even though it is “just” a star. It is the fourth brightest star we can see in Ellensburg. It is the most northerly bright star. It is a binary star consisting of two yellow giant stars that orbit each other every 100 days. At 10 p.m., Capella is a half a fist above the north-northwest horizon. You can also use the Big Dipper to find it.  First, find the two “cap” stars on the cup of the Big Dipper, the stars on the top of the cup. Draw line from the “cap” star closest to the handle to the cap star farthest from the handle. Then, continue that line to the next very bright star, which is Capella. Thus, you can “cap” to Capella. If you can’ it tonight, don’t worry. Capella is the brightest circumpolar star meaning it is the brightest star that never goes below the horizon from our point of view in Ellensburg.

Friday: The bright star Regulus is a finger-width below the crescent moon, low in the western sky at 10 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 https://nightsky.jpl.nasa.gov/planner.cfm.