Friday, January 2, 2015
The Ellensburg WA sky for the week of 1/3/15
Saturday: 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 19th 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 gibbous moonlight will 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 on how to observe a meteor shower, go to http://goo.gl/K8QRTY.
If the Sun looks big today, your eyes are not playing tricks on you. The Earth is at perihelion just before midnight tonight. 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.
Sunday: According to a crazy internet rumor, the planets will align at 9:47 a.m. PST and decrease gravity on Earth enough to make you feel weightless. DO NOT use this as an excuse to overeat the night before. The planets will not be lined up this morning. And even if they were, they are too far away to have any measurable upward pull on you. You should be more worried about the gravitational pull of those three body builders who work in the office right above yours than about the gravitational pull of any planet other than Earth. To find out more about this planetary alignment hoax, go to http://goo.gl/JZiexL.
Monday: Mercury and Venus are about a half a fist above the southwest horizon at 5 p.m. You will be able to spot Venus right away. Mercury is dimmer and may require binoculars to be seen. As the week progresses, these two planets will be moving higher in the sky and closer together.
Tuesday: Comet Lovejoy C/2014 Q2, the fifth comet discovered by the Australian amateur astronomer Terry Lovejoy, is making its closest approach to Earth tonight. Throughout the rest of the month, it will be moving higher in the sky and getting brighter. Tonight, it will be a challenge to find, even with binoculars. First find Rigel, the brightest star in the constellation Orion, three and a half fists above due south at 10 p.m. Comet Lovejoy is one fist, or about two binocular fields of view to the right of Rigel. For more information, including a finder chart, go to http://goo.gl/psV4F1.
Wednesday: The moon and Jupiter travel through the sky together tonight. They rise in the east-northeast sky just before 8 p.m. with Jupiter being about a fist to the upper left of the moon. As the night goes on, the moon moves eastward with respect to Jupiter meaning by the morning, Jupiter will be about a fist to the upper right of the moon.
Thursday: Saturn is two fists above the southeast horizon at 7 a.m.
Friday: Have you ever looked down on the ground and spotted a penny? In Yakima? While you were standing in Ellensburg? If you have, then you may be able to see the star Hamal as more than just a point of light. It has an angular diameter that can be directly measured from Earth. Hamal, the brightest star in the constellation Aries the ram, has the same angular diameter as a penny 37 miles away. (For comparison, the moon is about half the diameter of a penny held at arm’s length.) Hamal is three and a half fists above due west at 11 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 http://nightsky.jpl.nasa.gov/planner.cfm.