The Ellensburg WA sky for the week of 12/31/16

Saturday: Neptune is the dimmest planet that can be seen with binoculars. That makes it difficult to find. But not tonight. It is right next to Mars in the evening sky. First find Mars, the bright, reddish planet nearly three fists held upright and at arm’s length above the south-southwest horizon at 5:30 p.m. Now, center Mars in your binoculars. Neptune is the dot just to the upper left of Mars. View Mars again once an hour until it gets to close to the horizon at about 9 p.m. You’ll notice Neptune moving towards Mars in the sky. Actually, Mars, being much closer to Earth, is moving toward Neptune in the sky. Don’t forget to look at Venus, the bright point of light two fists above the southwest horizon.

Sunday: Today is the day we celebrate the anniversary of something new – a new classification of celestial objects. Giuseppe Piazzi discovered Ceres [pronounced sear’-ease], the first of what are now called “asteroids”, on January 1, 1801. Ceres is the largest asteroid in the belt between Mars and Jupiter. At first, Piazzi thought it was a star that didn’t show up on his charts. But, he noted its position changed with respect to the background stars from night to night. This indicated to him that it had to be orbiting the Sun. The International Astronomical Union promoted Ceres to the status of “dwarf planet” in August of 2006.

It turns out that this is a good time to view Ceres with binoculars. Ceres is four and a half fists above due south at 7 p.m. First find Alrischa, the third brightest star in Pisces. It is a little east of due south at 7 p.m. Move your binoculars so this star is on the far left of your binocular field of view. Ceres should be on the far right of your field of view. It will look like a star. However, if you go to this region of the sky over multiple nights, you’ll notice that one “star” changes position from night to night. This is Ceres.

Monday: Late tonight and early morning’s weather forecast: showers. Meteor showers, that is. The Quadrantid meteor shower peaks late tonight and early tomorrow morning between midnight and dawn. Meteor showers are named after the constellation from which the meteors appear to originate. That makes this shower mysterious because there isn’t any constellation with this name now. The shower was named after Quadrans Muralis, an obsolete constellation found in some early 19^th century star atlases. These meteors appear to come from a point in the modern constellation Draco the dragon. This point is about three fists held upright and at arm’s length above the northeast horizon at 1 a.m. This year, the waxing crescent moon will set long before the best viewing time and will not obscure the dimmer meteors. Meteors are tiny rocks that hit the Earth and burn up in the atmosphere. Most meteors are associated with the path of a comet. This shower consists of the debris from an asteroid discovered in 2003. Keeping with the comet-origin paradigm, astronomers think the asteroid is actually an “extinct” comet, a comet that lost all of its ice as it passed by the Sun during its many orbits. For more information about the Quadrantid meteor shower, go to http://earthsky.org/?p=4287.

Tuesday: You’ve seen the term “a pinch to grow an inch.” Well, Jupiter’s extremely strong gravitational field “pinches” Jupiter so much that it causes Jupiter to shrink by about an inch a year. Look for the svelte Jupiter three and a half fists above the south horizon at 7 a.m.

Wednesday: If the Sun looks big today, your eyes are not playing tricks on you. The Earth is at perihelion at about 6 a.m., Pacific Standard Time. If you dig out your Greek language textbook, you’ll see that peri- means “in close proximity” and helios means “Sun”. So, perihelion is when an object is closest to the Sun in its orbit, about 1.5 million miles closer than its average distance of 93 million miles. Since it is winter in the Northern Hemisphere now, the seasonal temperature changes must not be caused by the Earth getting farther from and closer to the Sun. Otherwise, we’d have summer when the Earth is closest to the Sun. The seasons are caused by the angle of the sunlight hitting the Earth. In the winter, sunlight hits the Earth at a very low angle, an angle far from perpendicular or straight up and down. This means that a given “bundle” of sunlight is spread out over a large area and does not warm the surface as much as the same bundle in the summer. For the Northern Hemisphere, that very low angle occurs in December, January and February.

Thursday: Has it been tough to wake up this past week? It should have been because the sunrise has been getting a little later since summer started. I know. I know. December 21 was the shortest day of the year. But, because the Earth’s orbit around the Sun is elliptical and not circular, the Earth does not travel at a constant speed. It moves faster when it is closer to the Sun and slower when it is farther away. This leads to the latest sunrise occurring in early January and the earliest sunset occurring in early December, not on the first day of winter, the shortest day of the year. On the first day of winter, however, the interval between sunrise and sunset is the shortest. For more information, go to http://goo.gl/SJC5r.

Friday: Saturn is about  a half a fist above due southeast at 7 a.m. Mercury is less than a fist to the lower left of Saturn, a half a fist above the southeast horizon.

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.