Wednesday, September 18, 2013
The Ellensburg sky for the week of 9/21/13
Saturday: “You know Aries and Cancer and Draco and Libra. Leo and Pisces and Virgo and Hydra. But, do you recall, the pointiest asterism of all? Triangulum, the three sided asterism, had a very pointy edge….” Sorry. Some stores have started putting up their Christmas decorations and that has put me in the mood to modify some Christmas songs. Anyway, Triangulum is a small constellation between the more prominent Andromeda and Aries. Its main feature is a skinny triangle oriented parallel to and nearly four fists held upright and at arm’s length above the east horizon at 10 p.m.
Sunday: At precisely 1:44 p.m. PDT, the center of the Sun crosses the celestial equator and passes into the southern sky. The celestial equator is an imaginary line that divides the sky into a northern and southern half. When the Sun is in the southern half of the sky, it appears to take a shorter path from rising to setting. It also does not get as high in the sky at noon. This leads to shorter days and longer nights. Since the Sun crosses the celestial equator today, there is an instant when it is equally in the northern and southern sky, called the north and south celestial hemispheres. This so-called “equal night” is given by the Latin word equinox. Thus, today is known as the Autumnal Equinox. However, the day and night are not of equal duration today. The sun rises at 6:50 a.m. and sets at 6:58 p.m. Day and night are closest to equal duration on Tuesday.
Monday: “My laddie, you’re a wee bit close to that launch” is what a stereotypical Scottish person may have said to a frog that watched the recent launch of the Lunar Atmosphere and Dust Environment Explorer. The spacecraft, abbreviated LADEE and pronounced “laddie”, was launched on September 6. A remote NASA camera captured an image of a frog jumping at the same time the rocket blasted off. Read more about the launch, and more importantly, the frog at http://goo.gl/YrwkpU. LADEE’s mission is to study the moon’s very thin atmosphere and conditions near the moon’s surface.
Tuesday: To celebrate the start of school at CWU tomorrow, let’s sing a song of the season. “Oh the weather outside is grand. And the fire is rightfully banned. There is really no place to go. Let it snow, let it snow, let it snow. On Mars.” The Mars Reconnaissance Orbiter has discovered evidence of carbon dioxide snow clouds high above the surface of Mars. Carbon dioxide, also called “dry ice”, exists in Mars south polar ice cap and requires temperatures of nearly 200 degrees below zero Fahrenheit to form. Astronomers were not sure how this polar cap gets replenished but the discovery of carbon dioxide clouds may provide an answer. For more information, go to http://goo.gl/shMTf. Mars is three fists above the east-southeast horizon at 6 a.m. The weather is certainly not grand on Jupiter, which you can find five and a half fists above the southeast horizon at this time.
Wednesday: Did you time the exact length of the day and night on Saturday, the first day of autumn? They were not equal in duration. Many people think that the day and night are the same duration on the autumnal equinox. The day is a little longer than the night for two reasons. First, the Sun is an extended object so even when the middle part has set, the upper half is still above the horizon lighting the sky. The second, and more influential reason is that the atmosphere acts like a lens, bending light from the Sun above the horizon when the Sun is really still below the horizon. Day and night are closest in duration today.
Thursday: The bright bluish star Vega is nearly straight overhead at 8 p.m.
Friday: The cloudy season is coming to Ellensburg. Don’t feel bad. According to astronomers from the European Southern Observatory, it is always cloudy season on HD 85512b, a newly discovered planet orbiting the star called… wait for it… wait for it… called HD 85512. These astronomers developed a method to estimate the cloud cover on planets orbiting distant stars. They think HD 85512b may be cloudy enough to have liquid water on its surface even though it is fairly close to its host star. While the presence of surface water does not guarantee finding life, it is a critical component. For more information, go to http://goo.gl/bGxMD.
The positional information in this column about stars and planets is typically accurate for the entire week.