Starwatch: Planets travel the superhighway of the heavens

May 6, 2017

On Sunday night we have a great conjunction, or what I like to call a celestial hugging, between the nearly full moon and the planet Jupiter in southern sky. The moon and the largest planet in our solar system will only be separated by 3 degrees. That’s the width of three of your fingers together held at arm’s length.

It should be quite a sight that you won’t want to miss. Let’s hope and pray for clear skies. With even a small telescope you can have a field day, or should I say night. Check out the mountains and craters of the moon, as well as Jupiter’s moons that resemble little stars on either side of the planet.

You might even see some of the cloud bands on Jupiter and maybe the great red spot that’s three times the diameter of Earth. The red spot is a storm that’s been raging in Jupiter’s atmosphere for hundreds of years.

Every month we have least one or two of these conjunctions, or celestial huggings. Next weekend we’ll have another conjunction, this time between the moon and Saturn. All of these conjunctions happen because of the ecliptic, the super highway of the planets and moon in our skies.

Planets are certainly wanderers among the stars from night to night and year to year. In fact, the word planet has a Greek origin that’s roughly evolved from what they called wandering stars. Back then, as far we know, no one really knew the nature of the planets except that they appeared to roam among the fixed stars in the celestial dome of heaven.

Early civilization observed that the moon, as well as the wanderers or planets, certainly didn’t move randomly among the fixed stars, but rather took about the same path among the stars, mostly migrating to the east but at times retrograding in a westward direction. This path is called the ecliptic because it was along that path where eclipses of the sun and moon occur.

The reason all of the planets and our moon pretty much take the same ecliptic path among the stars is that they, along with our Earth, all orbit the sun in the nearly the same geometric plane. They also move along the ecliptic at different speeds. The planets close to the sun, like Venus and Mercury are on a celestial caffeine high, and they zip along the ecliptic because they whip around the sun much faster than outer planets like Uranus and Neptune, that really take their sweet time completing the ecliptic circuit. Consider the ecliptic the long and winding road in the stars.

Along and on either side of the ecliptic are 13 constellations referred to as zodiac constellations. On any given night or day, a planet or our moon will be in one of these as they travel down the ecliptic highway.

The planets and moons aren’t the only wanderers in the night sky. Human-made satellites rip across the sky in just about all directions. For about 60 years we’ve shot hundreds and hundreds of satellites into space. Many of them are still functioning, fulfilling their various missions and tasks, but there’s also a lot of junk up there, like dead satellites and spent rocket stages. When I hold my star-watching parties, someone will inevitably call out, “Hey, look at the satellite up there!”

Early in the evening and early in the morning are the best times to spot satellites. While the sun has gone down from our point of view on Earth, the sun is still above the horizon high up in space where the satellites are, and the light is bouncing off of them. That’s what we see when we observe satellites, sunlight bouncing off their reflective surfaces.

Of course some satellites are brighter than others. The absolute king of the satellites is the International Space Station. At first glance it more closely resembles a high-flying jet airliner. The International Space Station is even brighter in the sky when the U.S. Space Shuttle is docked to it, but unfortunately those nights are coming to an end.

There are a lot of good websites for helping you spot and identify satellites, but I think the best one is Heavens Above at www.heavens-above.com. Once you configure the site to your location with the database, you’re good to go. Not only will it help you with satellites, but it can also do a lot of other neat stuff, like produce rough but still useful star maps.

Enjoy all the wanderers!