August Will Have Two New Moons! What’s the Huge Deal?

July 30, 2019 - Comment

First there have been “blue Moons;” now there are “black Moons.” What do these phrases imply? Sky & Telescope diagram For those who’ve been protecting your eyes on astronomy information currently, you might need began noticing hype-filled tales telling you to be sure you hold your eyes open in August: “There’ll be two new Moons!”


First there have been “blue Moons;” now there are “black Moons.” What do these phrases imply?

Phases of the Moon

Sky & Telescope diagram

For those who’ve been protecting your eyes on astronomy information currently, you might need began noticing hype-filled tales telling you to be sure you hold your eyes open in August: “There’ll be two new Moons!” The following new Moon is at three:12 UT on August 1st, which corresponds to 11:12 p.m. EDT; the second new Moon falls at 10:37 UT on August 30th.

A few of these tales lend the phenomenon a nickname, like “Black Moon.” There’s a better-known time period, “Blue Moon,” that has been round for many years. Whereas its precise definition is debated, today it often means the second full Moon in a month. A extra old school definition defines it because the third of 4 full Moons, just like the Blue Moon of Could 2019.

Two new Moons in a month, although — that’s the alternative of a Blue Moon. So what’s the massive deal a couple of Black Moon? Or is it an enormous deal in any respect?

Defining a Month by the Moon

Astronomers measure months in a number of methods. For example, a sidereal month is the time the Moon takes to make one orbit round Earth, relative to the background stars. In the meantime, an anomalistic month is the time between lunar perigees, the Moon’s closest level to Earth. These are about 27.5 earth days. However the lunation, or synodic month, is what most of us speak about after we speak about months: That’s the period of time it takes to return to a section, often from new to new.

Having two full — or new — Moons in a month is unusual however not uncommon. A lunation is about 29.5 days, and there are 365.25 days in a yr. So, on common, there are barely greater than 12 full lunar cycles a yr. This implies about each two and half years (2 years, eight months, roughly talking) there’ll be two full or two new Moons in a given month.

Phases of the Moon

We see the Moon undergo a altering cycle of phases every month resulting from its orbital movement round Earth and the altering geometry with which we view it.
Ana Aceves / Sky & Telescope

Let’s take a much bigger view, although. Since a 29.5-day lunar cycle is shorter than each month besides February, in yearly each month besides February is prone to have a repeated section.

Put otherwise, phases correspond to locations within the Moon’s orbit. So when the Moon finishes a lap and returns to the identical spot in its orbit across the Earth each 29.5 days, it’s additionally on the identical section. So on the finish of most months, the Moon is prone to come again to the spot it was in firstly of a month. Similar to that, there’s a repeated section in each month!

For instance, let’s check out the upcoming yr (dates are listed in UTC time zone):

August: New Moon on the first and 30th.

September: Skinny, waxing crescents on the first and 30th.

October: Waxing crescents on the first and 31st.

November: Waxing crescent on the first & 30th.

December: Waxing crescent on the first & 31st.

January 2020: Waxing crescent on the first & 31st.

February 2020: Not sufficient days for a full cycle, regardless that it’s a bissextile year. No repeating phases.

March 2020: Almost first-quarter crescents on the first and 31st.

April 2020: First quarter on the first and 30th.

Could 2020: Waxing gibbous on the first and 31st.

June 2020: Waxing gibbous on the first and 30th.

July 2020: Waxing gibbous on the first and 30th.

August 2020: Simply-about-full-waxing gibbous on the first & 31st.

So, what occurs if there’s a second new Moon? Not a lot. A second new Moon in a month may also help with skygazing, as a result of there’s no moonlight to scrub out the celebrities. However it’s arduous to get excited in any other case. In spite of everything, the brand new Moon lies between the Solar and Earth, and since the entire Solar’s mild is hitting the lunar far aspect, there’s nothing to see!

You may see information tales that attempt to acknowledge this. However they’ll fumble and say that the Moon shall be invisible to us at nighttime: “Second New Moon in Tonight’s Sky!” Nope. New Moons rise and set with the Solar, in order that they’re up within the daytime, not at evening.

Moreover, because the new Moon is up in the course of the day when clear skies are blue, wouldn’t or not it’s ironic if we referred to as new Moons Blue Moons?

Higher but, let’s keep away from the hype, benefit from the evening sky, and watch one other lunation unfold earlier than our eyes.



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