Celestial Lights
By Phyllis Burton Pitluga
January 2, 2009 San Miguel de Allende

IYA2009: The International Year of Astronomy

Venus, Jupiter and the crescent moon on December 1, 2008 (by Deborah Lewis, visiting from Sacramento, California).

The United Nations General Assembly endorses celebrating astronomy this year with the theme “The Universe: Yours to Discover.” It seeks to inspire youth to develop an interest in astronomy. Throughout the world and all year long, events will be focusing on the wonders of our fascinating cosmos. This year I am dedicating each monthly column to highlighting the Universe, moving farther outward each month and telling you about telescope observation opportunities.

The year 2009 was chosen because it was 400 years ago that Galileo first assembled lenses into a “spyglass” and turned it toward the sky. In honor of IYA2009, Mexico is celebrating the Noche de Estrellas (Night of the Stars) on Saturday January 31 from 7–11pm at various archaeological sites. In Querétaro state, the archaeological site is El Cerito. In Guanajuato state it is Plazuelas. Astronomers and telescopes will be available for informed viewing. For more information, go to http://dti.inah.gob.mx. On the main page in the upper right in the box named “buscar,” type in Noche de las Estrellas and click; on the next page click on “Todos las Palabras” and click “buscar.” On the next page click on the listing and then click on “English.”

I am talking with the director of El Charco del Ingenio about an observing event there in the spring for sanmiguelenses—stay tuned.

Four of the five easily visible planets are now adorning our evening sky. To give you an idea of what Galileo saw, use a pair of binoculars. You can steady them by propping up your elbows on a wall or table like a tripod. When Galileo looked at Jupiter through his newly crafted telescope he saw tiny worlds going around Jupiter— like in a racetrack. You can see these four “Galilean Moons,” as they are called today, even with binoculars and small telescopes. They are similar to what Galileo used and he made many discoveries. When he saw the moons going around Jupiter it made him realize that the idea of Copernicus must be correct—that the planets, including Earth, orbit around the Sun. He famously argued that point of view for the rest of his life.

As Galileo observed Venus in his new optics, he saw that Venus changes phase and shape like our moon. He realized that this could only happen if Venus went around the Sun, periodically passing between Earth and the Sun. Between now and March, you can see Venus becoming a taller, skinnier crescent as it nears us to pass by the Sun at the end of March.

When he viewed Saturn, Galileo didn’t know what to make of its shape. He remarked that it looked like it had ears. We know now that these ears are the famous rings circling Saturn. Right now, we are viewing the southern side of the rings. By year’s end we will be viewing the northern side. Like Earth, Saturn is tilted, causing seasons. Saturn glides around the Sun in an orbit taking nearly 30 years to complete, so the seasons are very long. For the past 15 years, the southern hemisphere and the southern face of the rings have been tipped toward the Sun—and Earth as well, because we are closer to the Sun. By September 4, it will be the spring equinox on Saturn and the thin-edged rings will disappear. Gradually, we will begin viewing the northern face of the rings for the next 15 years.

Galileo reported his discoveries in a small book he called Starry Messenger that was published in 1610. You can replicate these discoveries yourself with patience and binoculars or a small telescope. Bigger telescopes will improve upon Galileo’s view. As we explore the unbelievable new views and understandings of our universe in the year ahead, let’s celebrate the 400th anniversary of the astronomical telescope. 



Sky Calendar, January 2009 

By following the Moon as the biggest and brightest “pointer” in the sky, you can identify different planets and bright stars during this month. On subsequent nights you can relocate them, but without the Moon—the Moon moves about 25 times its own diameter from one night to the next. The Moon is much closer to us than the planets of our Solar System and the stars are even farther away. That is why when the Moon appears close to a celestial light they are truly separated by millions, billions or even trillions of miles.

As January begins, Mercury and Jupiter are low in the southwest in the glow of twilight. Venus is high in the south at sunset. Saturn rises after midnight in the east, crosses the sky all night and sets at dawn. Mars is beyond the Sun and is not visible.

Jan. 4, Sunday: This is the best view of Mercury above Jupiter, low in the southwest at 7pm. Tonight is the first quarter moon. The Quadrantid meteor shower rains meteors into our atmosphere between 1 and 5am low in the northern sky. Earth is closest to the Sun at 91.4 million miles in its yearly journey around our star—the average distance is 93 million miles. Paradoxically, this is also the time of year when our days are shorter and cooler than when we are farthest away in early July. This is because the Northern Hemisphere is tipped away from the Sun now.

Jan. 7, Wednesday: The waxing gibbous moon passes above the Pleiades star cluster.

Jan. 10, Saturday: Tonight’s full moon is the biggest of 2009 because it is also closest, so tides will be highest and lowest today. The full moon rises at sunset; for the next two weeks the Moon rises about 50 minutes later each night, becoming visible in the morning sky as it orbits toward the Sun.

Jan. 14, Wednesday: Venus is highest in the sky above the just-set Sun this evening.

Jan. 15, Thursday: The waning gibbous moon passes below Saturn.

Jan. 17, Saturday: The last quarter moon rises at midnight.

Jan. 21, Wednesday: The bright star Antares is just below the waning crescent moon in the morning sky.

Jan. 26, Monday: Mercury is to the left of Mars low in the morning sky. Today is the new moon, appearing dark because its dark side faces Earth.

Jan. 30, Friday: The waxing crescent moon passes above Venus in the evening sky. 

Phyllis Burton Pitluga is Astronomer Emerita of the Adler Planetarium and Astronomy Museum, Chicago, and is now a San Miguel resident.