The Ellensburg sky for the week of 12/29/12

Saturday: Did you get a new telescope for Christmas? Skyandtelescope.com has a good article on how to get started using it. Go to http://goo.gl/2cJwo. Any observing tip to the night sky should include Jupiter. Jupiter is six fists held upright and at arm’s length above due south at 10 p.m. tonight. A small telescope should reveal Jupiter’s cloud belts and its four largest moons. These are called the Galilean moons because Galileo Galilei discovered them about 400 years ago.

Sunday: Mars is a half a fist above the southwest horizon at 5:30 p.m.

Monday: Forget about that big bright ball in Times Square. You can mark the start of the new year with one of the sky’s own big bright balls. That perennial favorite New Year’s Day marker, Sirius, the brightest star in the night sky, rises to its highest point in the sky a little after midnight on January 1. Thus, when Sirius starts to “fall”, the new year has begun. Look for Sirius about two and a half fists above due south at midnight.

Tuesday: 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.

If the Sun looks big today, your eyes are not playing tricks on you. The Earth is at perihelion at about 9 p.m. 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.

Wednesday: Venus is a half a fist above the southeast horizon at 7 a.m.

Thursday: Today’s early morning weather forecast: showers. Meteor showers, that is. The Quadrantid meteor shower peaks this 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 above the northeast horizon at 1 a.m. This year, the waning moon will be rising just before the peak observation time so the dimmer meteors will be obscured by moonlight. 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.

Friday: 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 22 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 during the first week in 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. 

The positional information in this column about stars and planets is typically accurate for the entire week.

The Ellensburg sky for the week of 12/15/12

Saturday: Listen, do you want to know a secret? Do you promise not to tell? Whoa oh, oh. The Beatles certainly didn’t write this song about the Barringer meteorite crater in Arizona. Astronomers are studying this 50,000-year-old impact to learn more about our planet’s violent history as well as the physics of impacts throughout the solar system. If you’d like to be let in on some of these secrets, go to http://goo.gl/sqbBe.

Sunday: I know you’re staying up late to train yourself to wait up for Santa. So look out a south-facing window at 1 a.m. and see Sirius, the brightest star in the nighttime sky, as high as it ever gets in the sky. It is two and a half fists held upright and at arm’s length above due south.

Monday: Today is Saturnalia, an ancient Roman festival in honor of their god Saturn, the god of agriculture and time. The holiday featured a break from work and school, a public banquet, and private gift giving. Some of these customs influenced the secular aspects of Christmas celebrations. Celebrate Saturnalia at 6 a.m.-alia by viewing the planet Saturn, two fists above due southeast.

Tuesday: Jupiter is nearly two fists above the east-northeast horizon at 5 p.m. Wow – night sky observations at 5 p.m. It must be getting close to winter.

Wednesday: Venus is one fist above due southeast at 7 a.m. Even though the sky is fairly well lit by the nearly rising Sun, Venus is bright enough to be easily seen. The bigger challenge is Mercury, a half a fist to the lower left of Venus and just above the horizon.

Thursday: Tonight’s first quarter moon is in the constellation Pisces the fish.

Friday: At 3:12 a.m., the Sun reaches its lowest point in the sky with respect to the background stars. This point is called the Winter Solstice. During the day that the Sun reaches this point, your noontime shadow is longer than any other day of the year. Also, the Sun spends less time in the sky on the day of the Winter Solstice than any other day making this the shortest day of the year. Even though it is the shortest day of the year, it is not the day with the latest sunrise or the earliest sunset. The latest sunrise is during the first week in January and the earliest sunset is during the second week in December. The Sun is at its southernmost point with respect to the background stars on the day of the winter solstice. This means the Sun spends the least amount of time above the horizon on that day. But, the Sun rise and set time depends on more than its apparent vertical motion. It also depends on where the Sun is on the analemma, that skinny figure-8 you see on globes and world maps. During the second week in December, the Sun is not quite to the bottom of the analemma.  But, it is on the first part of the analemma to go below the horizon. During the first week in January, it is on the last part of the analemma to rise above the horizon. For more information on this, go to http://goo.gl/wE9nP.

The positional information in this column about stars and planets is typically accurate for the entire week.

The Ellensburg sky for the week of 12/8/12

Saturday: The earliest sunsets of the year occur all this week – 4:13 p.m. That seems counterintuitive because the shortest day of the year in the Northern Hemisphere isn’t until December 21. Since the Earth’s orbit is elliptical, the Sun does not appear to move across the sky at the same rate from day to day throughout the year. That means some parts of the year the Sun is “fast” and sometimes “slow”. Today, the Sun reaches the noontime position of due south at 11:52 a.m. meaning it will also reach the setting position a few minutes earlier than the expected time. For more information on this, go to http://goo.gl/kjnHP. Or just go watch the sunset. But don’t stare at the Sun.

Monday: Okay boys and girls. Let’s follow along with the moon this week as it tours the bright objects in the southeastern sky. At 6:30 a.m., the bright star Spica is less than a half a fist above the moon. Spica is believed to be the star that provided the ancient astronomer Hipparchus with the data to show that the Earth precesses like a spinning, wobbling top.

Tuesday: On these cold mornings, it is difficult to get going. You just want to plop into a chair and sit still. But, are you really sitting still? You’re moving at about 700 miles per hour due to the rotation of the Earth on its axis and 66,000 miles per hour due to the revolution of the Earth around the Sun. If that’s not enough, the entire solar system is orbiting the center of the galaxy at a whopping 480,000 miles per hour! So while you may be sitting still with respect to your living room (and all of the over achievers in your house), you are NOT sitting still with respect to the center of the galaxy. For more information about this concept, go to http://goo.gl/lPVPS. Before you barf from all of that motion, go outside at 6:30 a.m. and observe Saturn, less than a fist above the moon in the southeast sky. Because of Saturn’s rapid rotation, only 10.5 hours, it appears visible flattened.

Tuesday: At 6:30 this morning, the moon marks the right angle corner of a right triangle with the very bright Venus above it and Mercury to its lower left.

Wednesday: Just like during last month’s new moon, people are humming the astronomy version of 1981 Blondie hit The Tide is High: “The tide is high ‘cause the moon is new. Higher still when the moon’s close, too.” Tonight's moon is new. The new moon is the phase where the Moon is directly between the Earth and the Sun. That means the moon and Sun are both stretching the Earth in the same direction causing the ocean water in line with the Sun and moon to be pulled upward. In addition, the moon is at perigee so this is the day of the month when the moon is closest to the Earth. This accentuates the upward pull on the water and makes the tides really high.

Thursday: The Geminid meteor shower peaks late tonight and early tomorrow morning. Meteor showers are named after the constellation from which the meteors appear to originate. These meteors appear to come from a point in Gemini the twins. This point is about three fists held upright and at arm’s length above the east-northeast horizon at 9 p.m. tonight. You can follow this point throughout the night, as it will remain near the bright star Castor, the right hand star of the “twin” stars Pollux and Castor. This shower is typically one of the best ones of the year producing bright, medium speed meteors with up to 80 meteors per hour near the peak. This year, the moon will be new during the peak night ensuring dark skies.

Most meteor showers occur when the Earth passes through the orbital trail of a comet. The broken off comet fragments collide with the earth and burn up in the atmosphere. Astronomers had searched for a comet source for this shower since 1862 when the shower was first observed. Finally, in 1983, astronomers discovered the object that created the fragments that cause the meteor shower. To their surprise, it was a dark, rock that looked like an asteroid, not a shiny icy comet. Astronomers named this object Asteroid 3200 Phaethon. But, they still don’t know if it an asteroid or if it is a comet with all of its ice sublimated away by many close passes by the Sun. For more information about 3200 Phaethon, go to http://goo.gl/LuwGW.

Friday: Mars is less than a fist to the left of the thin crescent moon, low in the southwest sky.

The positional information in this column about stars and planets is typically accurate for the entire week.