Wildlife

4 Sky Events This Week: Harvest Moon, Green Giant, and Fall Equinox

The Moon offers a great starter destination to learning the night sky. Credit: Andrew Fazekas
September’s full moon rises this week and is called the Harvest Moon, offering a great starter destination to learning the night sky. Credit: Andrew Fazekas

This week two of the brightest planets join forces, and sky-watchers celebrate the change of seasons with a bright full moon.

Saturn and Venus.  Starting on Monday, September 16 after sunset, Venus and Saturn will be having a close encounter that will last most of the week.  Low in the southwest sky, the second planet from the Sun will be the first visible—as the brightest star-like object in the entire heavens.

Look carefully next to Venus—binoculars may help—and fainter Saturn will pop out of the glare of dusk.  Remember that since the two worlds are hot on the heels of the setting sun, they sink below the horizon less than an hour later.

The lord of the rings will pass only 4 degrees above the goddess of love—less than the width of your three middle fingers at arm’s length.  As the week progresses both planets will appear lower in the sky each night with Venus sliding a bit towards the left of Saturn.

Even the smallest backyard telescope will show off Saturn’s iconic rings and even some of its brightest moons—like Titan and Enceladus.

 

Full Harvest Moon.  Watch the near full moon rise soon after sunset, Wednesday, September 18, and reach official full moon status at 7:13 am EDT the next morning around when  sun rises.

The full moon nearest the fall equinox is known as Harvest  Moon and was probably coined by farmers in the Northern Hemisphere since its added light is said to have helped them gather in their crops.

 Binoculars will easily show off the moon’s dark patches visible with the naked eyes. Called plains or maria in Latin, meaning seas, these are vast, ancient lava plains formed over billions of years ago when magma from the moon’s interior spilled out onto the surface, triggered by giant asteroid impacts.

With telescopes, the views get even more exciting—you can get sharp views of hundreds of ridges, mountains, cliffs, and craters up close.

Check out the Hitchhiker’s Guide to the Moon—a very detailed website dedicated to showing you exactly what you can see on the surface of the moon—generated for every day of the calendar.

 

Moon and Uranus.  All night long on Thursday, September 19 the seventh planet from the Sun, Uranus, will park itself near the moon.

The green giant is only 4 degrees away from the moon. The cosmic odd-couple will appear about four degrees apart in the sky—equal to 8 full moons side-by-side.

This week after darkness falls the near full moon acts as a convenient guidepost for finding Uranus. Credit: Starry Night Software/ A.Fazekas

 

The green-colored ice giant has four times the width of Earth, but since it lies nearly 1.9 billion miles (3.1 billion kilometers) away from Earth, it’s barely visible to the naked eye—and only in very dark, pristine skies.

With the glare from the nearby moon, binoculars will be your best bet in spotting Uranus.  Just look for a tiny greenish-blue disk in the field of view. By the way, the absorption of red light by methane in the atmosphere is what gives Uranus it’s cool cyan coloring.

 

Equal Day and Night.  Autumn equinox is at 4:44 pm ET on Sunday, September 22,  and officially marks the time of year we kick off the fall season in the northern hemisphere and the start of spring in the southern hemisphere.  The word equinox comes from Latin meaning “equal night” and refers to the 12 hour long day and night that occurs only twice a year.

Looking at the mid-day position of the sun over the summer season,  Northern Hemisphere sky-watchers will notice that it has been slowly sinking closer to the southern horizon, and creating ever longer shadows.

It’s only on the spring and autumnal equinox that the Sun rises due east and sets due west.

Astronomically speaking, the September equinox marks one of the four major turning points in the cycle of seasons. The Earth spins on its axis, which is tilted at 23.5 degrees with respect to its orbital plane. On these days, however, the Earth’s axis is neither tilted away nor towards the Sun, but has both northern and southern hemispheres experiencing equal amounts of sunshine.

 

Follow Andrew Fazekas, the Night Sky Guy, on Twitter and Facebook.

 

Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.
  • k

    Just a minor correction: From Wiki “Another meaning of equinox is the date when day and night are the same length.[3] The equinox is not exactly the same as the day when day and night are of equal length for two reasons. Firstly, because of the size of the sun, the top of the disk rises above the horizon (constituting ‘sunrise’ which is the start of ‘daytime’) when the center of the disk is still below the horizon. Secondly, the Earth’s atmosphere refracts sunlight which means that an observer can experience light (daytime) even before the first glimpse of the sun’s disk has risen above the horizon. To avoid this ambiguity the term equilux is sometimes used in this sense.[4][note 1] Times of sunset and sunrise vary with an observer’s location (longitude and latitude), so the dates when day and night are of exactly equal length likewise depend on location.”

  • Michael Morris

    It is misleading to say that you can see the disk of Uranus in binoculars. Unless you have very high powered image stabilized binoculars (at least 15x), the image of the disk is unresolvable by the human eye. The maximum diameter of Uranus is 4 seconds of arc, so with 7x binoculars the apparent diameter is less than 1/2 minute of arc, equal to the blur spot of a person with abnormally good acuity of 20/10. Even in binoculars Uranus will look like a star, and how many stars will be visible in binoculars within an 8 degree circular patch of the sky, centered on the moon? To find Uranus in binoculars would require a star map showing its position relative to the moon plus some guide stars to aid in recognizing it.

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