Wednesday evening August 15th the 4.5-day old waxing crescent Moon will be about 7o from the blue-white star Spica in Virgo the Harvest Maiden.
In addition to the Moon are five planets spread out from west to east – Dwarf Planet Ceres, and the planets Venus, Jupiter, Saturn, and Mars.
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Over the next 10 days, from August 13th to the 23rd, the Moon will move eastward, as it always does, following the ecliptic and interacting with planets and stars near the ecliptic.
click on any graphic below to view each of the graphics full sized.
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Monday evening August 13th the thin 2.5-day young waxing crescent Moon will be about 10o from the inner planet Venus, and about 8o from the Dwarf Planet Ceres. However at 8th magnitude Ceres will be not be naked-eye visible, but Venus at a -4.6 apparent magnitude will be hard to miss!
And spread out from west to east are the planets Jupiter, Saturn, and Mars.
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Before sunrise on Saturday August 11th, Sunday August 12th, and Monday August 13th look toward the east and southeast for ‘shooting stars’, or meteors. The short-lived streaks of light are radiating outward from the area of the constellation Perseus the Hero. These are the annual Perseids – one of the best meteor showers each year. And these three days are centered more or less on the peak.
The Perseid Meteor Shower is named for the constellation from where the meteors radiate outward. This is the same for all meteor showers, and the ‘spot’ in the sky is known as the radiant. The Perseid radiant, as shown in the graphic, is within the Perseus constellation, and under ideal viewing conditions (dark and moonless skies) an average of about 60-80 meteors per hour could possibly be seen. This year without the interference of moonlight will increase the chances of seeing the meteors.
The peak for this year’s Perseids is Monday September 13th at 1 UT (8 pm CDT) however Perseus and the radiant rise at around 11 pm local time. A couple of hours later should be high enough over the horizon to become visible. I always look for a triangle made from using the Pleiades open star cluster, the bright star Capella in the constellation Auriga, and a not as bright star, Mirfak in Perseus. The radiant is up to the left from Mirfak as the graphic shows.
Best viewing times for seeing the Perseids are early morning a few hours before sunrise after Perseus has risen. This is an ideal time as the part of Earth you are viewing from is rotating toward the east, in the direction the Earth is revolving around the Sun. This means you will be seeing metaors ‘head-on’ as the enter the atmosphere.
Meteor showers result from the Earth’s orbital path intersecting areas of comet debris. Comets, as they orbit the Sun, leave behind pieces of their icy, dirty, selves. If these debris clouds happen to be along the Earth’s orbital path then the Earth will regularly pass through the comet debris cloud. As this happens the small comet pieces hit our outer atmosphere and vaporize from the friction generated heat. We then see these as the shooting stars that make up meteor showers.
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Friday August 10th the Sun in its apparent eastward motion along the ecliptic, moves out of the constellation Cancer the Crab and into the constellation of Leo the Lion. This is the true or actual position of the Sun as opposed to the pseudoscience of astrology which usually has the astrological Sun one constellation ahead or east from the Astronomical Sun’s position.
Read a little more about how astrology has the Sun incorrectly placed in a previous blog, and in another blog discussing the effects of precession.
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Friday August 10th the 28.5 day old waning crescent Moon will be crossing the plane of the ecliptic moving north relative to the ecliptic. This is known as the ascending node, one of two intersections the Moon’s orbital path has with the ecliptic. The ecliptic is actually the Earth’s orbit and the Moon’s orbit is inclined about 6o from the ecliptic. So there are two node intersections, the ascending and descending nodes.
Does our Moon actually go around the Earth as many graphics show? From our perspective on the Earth the Moon appears to circle around the Earth. However, in reality, the Moon orbits the Sun together with the Earth*
*Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)
Read this very informative article about the Earth-Moon system and their orbital motions, written by Joe Hanson. “Do We Orbit the Moon?”
Perigee Moon
Our Moon reaches perigee, (closest distance to Earth), for this orbit on Friday August 10th. At that time the Moon will be at a distance of 28.07 Earth diameters (358,100 km or 222,513 miles) from the Earth. The Moon will also be 28.5 days old, and only 15.8 hours from new Moon Phase.
When the time of perigee is close to a node crossing there will be either a lunar or solar eclipse. In this case less then 24 hours after the node crossing there will be a partial solar eclipse. This solar eclipse is only visible from Arctic, Greenland and parts of Asia.
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Wednesday August 8th the innermost planet Mercury reaches inferior conjunction. At inferior conjunction Mercury will move between the Earth and the Sun – much like the position of the Moon at new phase. The graphic to the right shows the planet positions relative to the Earth and Sun for both inner planets and outer planets.
At this inferior conjunction Mercury will not be directly in line with the Earth and the Sun – on the ecliptic. Mercury has an orbital inclination of 7o with respect to the ecliptic. So like our Moon, Mercury during each complete orbit, will cross the plane of the ecliptic moving north (ascending node) and also moving south (descending node). For this inferior conjunction Mercury will be 7o south, its maximum latitude south from of the ecliptic.
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