Celestial Lights
By Phyllis Burton Pitluga, Jan, 5 2007

January 2007, Venus is back in the evening sky

Just a year ago, Venus moved from the evening sky into the morning sky, where it remained for most of the rest of 2006. Now, Venus is once again in our evening sky after having been hidden behind the Sun for nearly three months. Venus will continue to adorn our western sky in the months ahead as it orbits out and around, toward us—getting ever brighter and bigger in telescopes. By June, Venus will be highest up from the setting Sun (45 angular degrees up, or halfway up, in the sky to overhead) before it quickly zips toward the Sun to pass between Earth and the Sun in August. 

As you follow the changing elevation of Venus in the sky, recall that the Mayans were careful observers. They used its cycles in their very accurate calendar system, as recorded in the Dresden Codex. 

Orion Nebula composite photograph from the Hubble Space Telescope and the Spitzer Space Telescope (public domain through the National Aeronautics and Space Administration)



Earth closest to Sun on January 3

If you are surprised that we are closest to the Sun in January (thinking that we must be closest in the summer), then read on. Earth orbits the Sun in an elliptical (oval) orbit. On July 6 we will be farthest from the Sun and now, in January, we are closest. The difference is about 1.5 million miles to either side of our average distance of 93 million miles (2.5 million kilometers to either side of 150 million kilometers). What affects our seasonal temperature far more is that the Northern Hemisphere is tipped toward the Sun in the summer. Thus, the Sun shines more directly upon us (overhead in San Miguel). Now, in the wintertime, the Sun is much lower, giving us angled sunlight that is more spread out and thus cooler.

So, are the summers in the Southern Hemisphere, when it is summer in January, much hotter because the Southern Hemisphere is tipped toward the Sun and we are tipped away? Actually, the two hemispheres are very different. The Southern Hemisphere has far more ocean and much less land. The oceans are big “heat sinks,” absorbing solar energy, whereas the northern lands reradiate the sunlight, heating the blanket of air around us.

Starbirth in a neighborhood nearby

This time of year, the beautiful Orion Nebula is up in our eastern sky at dusk and rises higher and higher all evening long. Located nearly 1,500 light years away from Earth, the cloud is the brightest spot in the sword in the constellation Orion-the-Hunter. Soon, we will have a planetarium and observatory here in San Miguel where you will be able to view such celestial wonders through telescopes (more information in an upcoming article). 

The Orion Nebula is one of many clouds of gas and dust where gravity is pulling together the gases, sculpting out clusters of newborn stars. 

This cloud is the closest star-forming region, and some 1,000 young stars are shining within it.

The photograph is a composite taken with the Hubble Space Telescope and the Spitzer Infrared Space Telescope. Here is the NASA description that accompanied the composite: “At the center are four monstrously massive stars, collectively called the Trapezium. These stars are approximately 100,000 times brighter than our Sun, identified as the yellow smudge near the center of the composite. The swirls of green were revealed by Hubble’s ultraviolet and visible-light detectors. They are hydrogen and sulfur gases heated by intense ultraviolet radiation from the Trapezium’s stars.

“Wisps of red and orange detected by Spitzer indicate infrared light from illuminated clouds containing carbon-rich molecules…. Additional stars in Orion are sprinkled throughout the image in rainbows of colors. Spitzer exposed infant stars deeply embedded in a cocoon of dust and gas (orange-yellow dots). Hubble found less embedded stars (specks of green) and stars in the foreground (blue). Stellar winds from clusters of newborn stars scattered throughout the cloud etched all the well-defined ridges and cavities.”

This amazing composite photograph taken in different wavelengths of light (different energies from cooler infrared to hotter visible light and then to the even hotter ultraviolet light) are revealing the dynamic stories of the stars. Our star, the Sun, was born from a similar cloud five billion years ago and has undergone changes to become the steady source of heat and light that we enjoy today. 



Sky calendar, January 2007

By following the Moon as the biggest and brightest “pointer” in the sky, during the month you can identify different planets and bright stars. On following 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 than the planets of our Solar System, and the stars are even farther. So, when the Moon appears close to a celestial light they are truly separated by millions, billions or trillions of miles. 



Jan. 3, Wednesday: Quadrantid Meteor Shower—best viewing halfway up in the northeast at 5am, Earth closest to Sun, Full Moon rises at sunset; for the next two weeks the Moon rises about 50 minutes later each night, making it also visible in the morning sky as the Moon orbits toward the direction of the Sun. 

Jan. 6, Saturday: Waning Gibbous Moon passes two moon-diameters above Saturn.

Jan. 11, Thursday: Last Quarter Moon rises after midnight.

Jan. 15, Monday: Waning Crescent Moon passes 12 moon-diameters beneath Jupiter.

Jan.18, Thursday: New Moon (= no Moon because the dark side faces Earth). 

Jan. 20, Saturday: Waxing Crescent Moon passes below Venus.

Jan. 25, Thursday: First Quarter Moon, at sunset, is halfway across the sky from west to east and will continue orbiting eastward each evening.

Jan. 27, Saturday: Waxing Gibbous Moon.



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