Jared May: What's Up July October 1-8, 2021

October, the true month of fall, is finally here. It seems that that spooky season is greeting us with lots of mostly cloudy skies, unfortunately. But some nights ahead may give way to some briefly clear moments. The nighttime temperatures are a little warmer this week, hovering around the low 60s. Sunset is around 7:10 PM so have your telescopes, binoculars, and stargazing gear out and ready by 8 PM. Be on the lookout this week for the new moon, zodiacal lights, the vertical Milky Way, some outer planets, the “evening star”, and some fall constellations.

If you are an observant person, you will have noticed the moon still hanging out in the western skies early morning this past week. Have you been able to track its motion across the sky from day to day? If you were tracking it, you have noticed it creeping closer to the sun (further east) every day. The whole lunar cycle, from new moon to full moon back to new moon, takes 28 days, so each “quarter cycle” takes a week. One week is a full moon and next week around the same time will be the 3rd quarter, a week after will be the new moon, and so on. Wednesday, October 6, will mark the official new moon for the month of October, so the night skies will be clear of its bright light for a few days.

Zodiacal light is an elusive astronomical phenomenon that very few people will see in their lifetimes. This is mostly because it is very faint and can easily be washed out by light domes and light pollution. This faint stream of light is best seen in the eastern skies just before sunrise at this time of year. A faint white light will appear to stretch from the eastern horizon up along the ecliptic (the plane of the solar system). The zodiacal lights are caused by lots of tiny “dust” particles floating around in the solar system reflecting sunlight. The zodiacal lights aren’t as photogenic as the northern lights and they are arguably much more difficult to see.

A simulated view of the elusive zodiacal light (seen just above the “E”) in the morning skies.

If you find yourself under dark skies, one of the long arms and the core of the Milky Way will make their presence known. Around this time of year about an hour after sunset, the Milky Way stands straight up starting at the southwest horizon and stretching all the way through the zenith. Since we are in the plane of the Milky Way, we can only see into/out of the plane or above/below. As you might imagine, as we look into the plane of the Milky Way (where most of the stars in our galaxy reside), there is a rich field of stars, clusters, gas, and dust.

This week the Milky Way stands straight up in the evening when the skies are fully dark.

Between roughly 7:15 PM and 8 PM, you will see the sky transition from a pale blue color to black. Through this transitionary period from twilight to darkness, more and more stars will fill the sky. Some of the first “stars” to be visible during this period are actually planets. If you look above the southern horizon anytime this month you will see Jupiter and Saturn. Because they reflect so much sunlight, they appear very bright and to the untrained eye, may appear as bright stars.

Amongst the brightest “stars” in the southeast after sunset are not really stars at all, but planets.

If we turn our attention to the western horizon just after sunset, we will see the “evening star”, also known as Venus. Since Venus is roughly the same size as the earth and relatively nearby, it reflects a lot of sunlight and appears even brighter than the gas giants of Jupiter and Saturn. This is why Venus is the second brightest object in the night sky (the brightest object is the moon).

Venus hovers near the western horizon right after sunset all month.

Each season is home to a set of different constellations. This is caused by the earth’s orbit around the sun. During different times of the year, different parts of the sky are hidden behind the sun and different parts are visible at night. Fall is famous for the Andromeda, Perseus, Cassiopeia, and Triangulum constellation (among many others). These constellations didn’t always look like how we see them. When the ancient Greeks and other civilizations were naming them and using the stars to navigate, the night sky looked different. This is because the stars are not fixed objects. All of the stars we see are also whipping around the Milky Way at whopping hundreds of thousands of miles per hour! And despite the sky looking like a flat painting, there is depth. So the constellations we see are actually very 3D arrangements of stars. Think about that the next time you are stargazing. (https://www.amnh.org/explore/ology/astronomy/what-is-astronomy)

October is here and it brought with it some cloudy nights. Despite this, there is some good news – the nights will still be relatively warm for several days so you don’t need to pull out your winter coat for stargazing just yet. If some of the forecasted partially cloudy nights have some gaps in the clouds then be on the lookout for the zodiacal lights, the vertical Milky Way, Jupiter, Saturn, Venus, and some fall constellations.

Clear Skies!