How super is the upcoming supermoon?

The moon is growing now, more and more visible every night. While it’s technically full for only one night, it will seem above all full for a night or so before and after. The bright summer moon can be frustrating: It’s so dazzling that it drowns out the stars and dimmer objects that many astronomers like to stay up late to view. And the upcoming full moon will be one of the brightest of 2023 — it’s the first full moon “supermoon” of the year. Save the nebula and galaxies for next week; spend this full moon cycle appreciating our closest celestial neighbor.

The full moon occurs at 7:39 am Eastern DST on Monday, July 3, which means it will appear full on both Sunday night and Monday night. The term “supermoon” is a relatively recent introduction to the astrological lexicon, but these events are nothing new; occur several times a year. We will have two full moons in August, including a blue supermoon (a second full moon in a month) on August 31st.

A supermoon occurs when the Moon is closest to Earth in its elliptical orbit around our planet. As pioneering scientist Johannes Kepler discovered four centuries ago, bodies do not orbit in a perfect circle, but in an ellipse. This means that they will sometimes move in and out of their host. The Moon is on average 238,000 miles from Earth, but on July 3, our celestial companion will be about 224,895 miles away. This is still extremely distant; you could fit 28 Earths between here and there. But it’s closer than average. And the closer Moon takes up more space in the sky.

Supermoons can appear not only larger, but about 30% brighter.
Supermoons can appear not only larger, but about 30% brighter. PICCO99, CC BY 3.0/Wikimedia

The Moon may appear about 14% larger during perigee, its closest approach to the Earth, than during its apogee, its farthest point. It can also appear 30 percent brighter. If you pay attention throughout the year, you may notice how much smaller or larger the Moon can seem from month to month. To understand the differences, we need to talk about how astronomers divide the celestial vault.

From horizon to horizon, the sky is a 180-degree semicircle; straight overhead is 90 degrees and so on. For a rough estimate of how to break it into smaller sections, make a fist and punch it skyward at arm’s length. At that range, your punch will cover about 10 degrees of arc. These degrees are further divided into sections. One degree contains 60 arc minutes, which are in turn divided into 60 arc seconds. The Moon and Sun are about 30 arcminutes in diameter, depending on the month.

On the night of the supermoon, the Moon will have a diameter of 33.02 arcminutes. During the February full moon, when our neighbor was at apogee and we witnessed a “micromoon,” it covered 29.44 arcminutes. Just a few arcseconds doesn’t seem like a lot, but it will seem like a lot. The Moon will be bright all night, all this week and all weekend. If you’re lucky enough to have clear skies, head out after dark. You might be surprised at how much you can see by the light of the Moon alone.

Although the Moon is extremely bright this cycle, it will not overwhelm the brilliant Venus in the western sky. On July 1, the planet will shine below Mars and near the bright star Regulus. Mars and Venus will pass within 3.5 degrees of each other, a very close astronomical alignment. Over the centuries, astrologers have attached great significance to such events. But I think it’s worth noting that they are beautiful without attributing any higher meaning to them. Just like the next “supermoon”.

Is there something you would like to know about our brilliant night sky? Share your stargazing questions with us, and you may see them answered in a future Wondersky column!

#super #upcoming #supermoon
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