The Ellensburg WA sky for the week of 3/5/16

Saturday: It’s getting dark. The last remnant of twilight has disappeared. Suddenly, you notice a large softly radiant pyramid of light in the western sky. The base of this ghostly triangle is along the west horizon and the peak stretches two or three fists above the horizon. It is not really a ghost. It is an effect called the zodiacal light. This light comes from sunlight reflecting off dust grains in our solar system. The effect is the most visible when the band of constellations called the zodiac makes a steep angle with the horizon. You need a clear dark sky with no haze or light pollution to see the zodiacal light. At its brightest, the zodiacal light rivals the light of the central Milky Way. Look for the ghostly patch after twilight for the next few weeks.

Sunday: Jupiter is opposition tomorrow night. That doesn’t mean that Jupiter is a teenager. Opposition means that Jupiter is on the opposite side of the Earth as the Sun. When an object is in opposition, it is at its highest point in the sky during the darkest time of the day. Thus, opposition is typically the best time to observe a planet. Jupiter is five fists above due south at midnight. If you don’t want to stay up so late, you can see it two fists above the east-southeast horizon at 8 p.m.

Monday: Last week I wrote that astronomers estimated that asteroid 2013 TX68 will pass “close to” Earth. But I didn’t say when. That’s because they were not sure. The latest measurements have it pass somewhere between 15,000 miles and 3 million miles from Earth today or tomorrow. The uncertainty is so large because astronomers don’t know enough about its orbit. For more up to date information about 2013 TX68, go to http://goo.gl/5qUbhx.

Tuesday: Do you have a trip to Indonesia planned for today? If you do, make sure you observe the total solar eclipse. During a total solar eclipse, the Moon passes directly between the Earth and Sun, blocking the Sun’s light from hitting the Earth. Maximum eclipse happens today at 6 p.m. Ellensburg, Washington time and at about 9 a.m. March 9 in Jakarta, Indonesia. The San Francisco Exploratorium Museum has a live webcast of the eclipse at http://www.exploratorium.edu/eclipse/. The telescope feed goes from 4:00 to 7:15 p.m. and the actual webcast, with commentary, goes from 5:00 to 6:15 p.m. Pacific Standard Time today, March 8.

Wednesday: If the National Enquirer was around in Galileo’s day, it may have featured the headline: “Saturn has love handles; Opis leaves him for a much hotter starlet”. When Galileo first observed Saturn through a telescope, he reported objects that looked like bulges on either side of Saturn’s midsection. He was actually seeing Saturn’s rings through less than ideal optics. Saturn is two fists above the south horizon at 5:30 a.m. The star(let) Antares is about a fist to the lower right of Saturn. Antares’ rival, Mars, is about one and a half fists to the right of Mars, just on the other side of due south.

Thursday: Venus is just above the east-southeast horizon at 6 a.m.

Friday: It is often said that Earth is a water world because about 70% of the Earth’s surface is covered by water. What would it look like if all that water on the surface were gathered up into a ball? That “ball” would be about 700 km in diameter, less than half the diameter of the Moon. The Astronomy Picture of the day shows us right here http://goo.gl/4wXLM.

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.