December 9, 2019

AstroEvent of the Week: 04.20.09: A Morning of Moons and Meteors!

There are two reasons to set your alarm this week; one is the annual Lyrid meteor shower, and the second is the lunar/planetary action in the dawn sky. First, the shower. The Lyrids break the lull we’ve had in meteor showers for a few months; this showers’ radiant is located in the constellation Lyra near the star Vega (of Contact fame!) and can be expected to produce about 10 meteors per hour around the mornings of April 22nd.

This is not the greatest shower of the year. However, the Moon will be a 6% illuminated waning crescent, and ceasing to be much of an interfering factor. Which brings us to our second item of note: on the 19th, the Moon will form a pairing with Jupiter and a very faint (and telescopic!) Neptune; then on the morning of the 22nd, the Moon will go on to join Venus and Mars in conjunction. All of the planetary action except for Saturn seems to be in the morning sky! For viewers west of the U.S. Appalachian Mountains, the Moon will actually occult Venus after dawn around 13:00 universal time! This should provide several unique photo ops, both before and after sunrise. Acquiring the Moon, which is only two days from New, before sunrise will make it easier to follow once the Sun is up; be sure to spot tiny distant Mars before day break, and keep an eye out for swift moving Lyrids!

Which brings us to our astro-word of the week, which is ashen light. Ever notice that you can faintly see the unlit limb of the Moon when it’s a slender crescent? This effect is not an illusion. The crescent is the sliver of the daytime side we see lit by the Sun, while the grayish dark limb is a peak at the nighttime side. This should not be confused (but frequently is) with the lunar farside, which we never see! This is because the Moon is tidally locked in rotation with the Earth… so just what causes that eerie glow? The short answer is; us. The Earth acts as a big mirror, reflecting light off of its oceans, cloud tops and land masses back up to space and the Moon. Imagine standing on the Earthward facing side of the Moon, looking up. You would see a fat, gibbous Earth, the reverse of the phase we see this week! If the Earthward facing side is especially cloud covered, the Ashen light will be even more pronounced. Of course, if your locale is cloud covered, you won’t see anything! Also called Earthshine, or “The old Moon in the New Moon’s arms,” this effect actually occurs around both waxing and waning crescents, such as this week. Enjoy!

 

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  1. [...] of August 21st. The Moon will lie less than 2 degrees from Spica and should display Earthshine or Ashen light “betwixt the horns” of its 23% illuminated crescent. The Moon will actually occult Spica as seen [...]

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