This is the time of year to dust off your telescope if it has been in the closet over the winter. Or dust off your observing skills if you are like me and have been inside more than you should be. We live in a very dusty place. I’m not talking about the Four Corners and the Desert Southwest, but about our solar system.
When the solar system formed 4.5 billion years ago, matter started collecting into clumps mostly from random collisions. The bigger the clump was, the greater the gravitational attraction it had, and thus the greater ability to attract even more material to itself. The biggest clump, around 99.9 percent of the material, ended up as the sun. Most of the rest ended up in Jupiter. Fortunately for us, there was enough dust and debris remaining to form the other planets.
Dust is still falling into Earth’s gravitational well. Every day, many tons of space dust fall into the Earth’s atmosphere. If the grains are large enough, we see them as meteors when they hit. But most are too small to see. And the tiniest grains can float down without burning up. Recently, this space dust has been found on rooftops and in all the usual places you might find dust. It has always been there, but just took some time to verify its identity since it is mixed in with all the terrestrial dust.
You can see this space dust, and you don’t even need a microscope to do it. Just look for it while it is still in space. Because dust reflects light from the sun, it can be seen when conditions are right and you have dark skies like we have in Durango. The light reflected from the dust is called the zodiacal light, because it is aligned with the zodiac.
The zodiac is the band in the sky around the ecliptic, which is the path the sun takes through the sky. It is tilted with respect to the Earth’s equator, which is why we have seasons. All the planets, and most of the interplanetary dust, stays within this zodiacal band.
Whatever the time of year happens to be, the zodiac at sunset shows the path the sun will take over the next few months. Half the year the zodiac is high overhead in the evening, and the other half it is low on the southern horizon. Right now, near the spring equinox, the sun is near the celestial equator and the evening zodiac is high overhead. Conversely, at the fall equinox, the evening zodiac will be low in the southern sky.
This monthThis is the best time of the year for observing the zodiacal light in the evening. On a very clear night without much moonlight it should be easy to spot. The sun is setting approximately due west, and from the horizon, the zodiac is pointed as high overhead as it will ever get in Durango. Right after dusk, look for the faint region rising up from where the sun just set through Taurus and Gemini, where it will intersect the Milky Way. The fall equinox will show it similarly well in the morning before dawn.
Jupiter reached opposition April 7. That was the day it was closest to Earth. For the next few months, it will be the brightest object in the evening sky, and for the next month or so it will be in retrograde motion. That means it will be moving west with respect to the background stars rather than the more typical eastward motion. On April 10, Jupiter will be quite close to the almost full moon. To see the Galilean moons change position from night to night take a look through binoculars.
Dust from the comet Thatcher collides with Earth during the Lyrid meteor show. The peak might show 20 meteors per hour on the morning of April 23, with the radiant near the bright star Vega.
Charles Hakes teaches in the physics and engineering department at Fort Lewis College and is the director of the Fort Lewis Observatory. Email him at firstname.lastname@example.org.