SKY GUIDE: This map represents the night sky as it appears over Maine during August. The stars are shown as they appear at 10:30 p.m. early in the month, at 9:30 p.m. at midmonth, and at 8:30 p.m. at month’s end. Saturn is shown at its midmonth position. To use the map, hold it vertically and turn it so that the direction you are facing is at the bottom. Sky Chart prepared by Seth Lockman
The month of August is named for Augustus Caesar. Both July and August have 31 days because they are named after Roman emperors. We start this month celebrating the midpoint of summer on Aug.1, one of the four cross-quarter days between the equinoxes and solstices. This day is also known Lammas Day, a Christian holiday celebrated in some English speaking countries. The word means “loaf-mass.”
It has been a rainy and humid summer so far, but hopefully August will turn out much nicer with the traditional Bermuda high pressure system keeping out more of the rain. There are many interesting highlights to observe in the midsummer skies this month. The “star” of the month will be the planet Saturn since it will reach its opposition on Aug. 27 when it will rise at sunset and not set until sunrise and shine at its best and brightest as it is also closest to Earth. The other major highlights include a favorable Perseid meteor shower close to the new moon that could approach 100 meteors per hour from a dark sky site on Aug. 12 and Aug. 13, and not one but two super moons including a blue moon and the closest super moon of the year on Aug. 30.
Then we have some lesser highlights like losing Venus in the evening sky early this month just to have it return to our morning sky on Aug. 21 showing a large and very thin crescent shape in a telescope. Mars and Mercury will have a close conjunction around the middle of the month very low in the western evening sky.
Saturn reaches opposition every 54 weeks. That is when a superior planet is closest to earth and directly opposite the sun from Earth, causing it to rise at sunset and not set until sunrise. All the superior planets reach their oppositions in the midpoint of their retrograde loops, or westward moving loops they trace in our sky as seen against the fixed background of stars.
This motion is an optical illusion since we are all orbiting the sun continuously in a counterclockwise direction as seen from above our solar system. No planet ever actually stops and reverses direction for a while, but it certainly looks that way. Saturn started its retrograde or westward motion on June 17 and it will return to its normal eastward motion on Nov. 4. Saturn will get as close as 746 million miles from us on Aug. 27, compared to its average distance of 835 million miles.
Even with Saturn at its best, Jupiter will still be nearly 3 magnitudes – or 15 times brighter – than Saturn. Jupiter begins the month rising around midnight and ends the month rising around 10 p.m. It will go into retrograde in Taurus early next month on Sept. 4, reach opposition on Nov. 2, and end its retrograde on Dec. 3. The king of the planets will be close to a last quarter moon on Aug. 8 and just 16 degrees from the Pleiades open star cluster in Taurus. Jupiter is still getting a little closer and brighter each night and you can see one or more of its four large Galilean moons with just a pair of binoculars.
Venus will pass through inferior conjunction with the sun on Aug. 13 when it will disappear for about a week and then return to our morning sky. It is a very large and thin crescent now since it is so close to Earth. This arrangement leads to transits across the face of the sun, or mini eclipses, if Earth, Venus, and the sun are perfectly aligned at inferior conjunction. That only happens eight years apart with a following gap of 121.5 years and then two more transits eight years apart with the next gap lasting only 105.5 years. I was lucky enough to see both of the last two transits of Venus, on June 8, 2004 and June 5, 2012. The next one will be in 2117.
Mercury will be visible below and to the right of Mars very low in the western evening sky half an hour after sunset for the first three weeks of this month. Mars will be very close to a thin waxing crescent moon on the evening of Friday, Aug. 18. Mercury will reach greatest eastern elongation from the sun on Aug. 9, but it will still not be very high in our sky.
The major highlight of this month is a favorable showing of the Perseid Meteor shower. You can expect more than one meteor per minute from a dark sky site since the moon will be a thin waning crescent rising at 1:30 a.m. on Aug. 12 and 2:30 a.m. on Aug. 13. It will be new on Aug. 16, a few days after the Perseids. Caused by Comet Swift-Tuttle, which orbits the sun every 133 years and is in an eleven to one orbital resonance with Jupiter, the Perseids are usually the second best shower of each year right behind the Dec. 13 Geminids.
These meteors are quite fast, hitting our upper atmosphere at the edge of space about 62 miles high at 37 miles per second, which is twice as fast as the earth is always orbiting the sun. They are tiny, about the size of a grain of sand and even less dense, but the ionization energy they generate at that great speed translates into those very bright streaks of light, most of which last less than one second. All of the meteors will originate from Perseus the Hero below the circumpolar constellation of Cassiopeia the Queen, but the best place to look is about 45 degrees away from this radiant, which is in Cygnus the Swan and the rest of the summer triangle which nicely frames the summer Milky Way.
AUGUST HIGHLIGHTS
Aug. 1: Full moon is at 2:32 p.m. This is also known as the Grain, Green Corn, or Sturgeon moon. This is also a super moon since it is less than one day from perigee at 1:52 a.m. on Aug 2.
Aug. 3: The moon passes 2 degrees south of Saturn this morning.
Aug. 4: In 2007 the Phoenix mission was launched to Mars. It got there on May 25, 2008 and studied the planet for five months. It landed farther north on Mars than any other spacecraft. It dug down about a foot into the Martian surface and verified the presence of water ice along with sending back over 25,000 pictures. It also discovered perchlorates, which can be food for some microbes and poison for others. Perchlorates are used in rocket fuel, explosives, and fireworks.
Aug. 6: The Curiosity Rover landed on Mars on this day in 2012 and it is still working. It found evidence of ancient lakes on Mars with the right chemistry to support living microbes along with methane in its thin atmosphere, about 100 times thinner than ours on Earth. Mars may even have had fresh, drinkable water for millions of years. The Perseverance Rover was launched July 30, 2020 and got there Feb. 18, 2021. Its little helicopter drone named Ingenuity made its first flight on April 19, 2021, just 118 years after the Wright Brothers first flight on Dec. 17, 1903. We got to the moon 66 years later, but we were flying around on another planet, 400 times farther away than the moon 118 years later.
Aug. 8: The moon passes 3 degrees north of Jupiter this morning. Last quarter moon is at 6:28 a.m.
Aug. 9: Mercury is at greatest eastern elongation from the sun today.
Aug. 13: The Perseid meteor shower peaks this Sunday morning. It will happen for several weeks before and after this date. Venus is at inferior conjunction this morning.
Aug. 16: New moon is at 5:38 a.m.
Aug. 17: In 2006, the Voyager 1 spacecraft made it out to 100 astronomical units into our solar system, more than twice as far away as Pluto.
Aug. 18: The moon passes near Mars and Mercury this evening.
Aug. 22: The X-15 experimental jet set a height record of 354,000 feet or 67 miles high in 1963. That is just beyond the edge of space which is called the Karman line and is 100 km or 62 miles above the surface of Earth. That is where most of the meteors burn up and the northern lights take place. Above that line it is all black even with a bright sun because there are no more air molecules to scatter any sunlight.
Aug. 24: First quarter moon is at 5:57 a.m. The moon passes 1.1 degrees north of Antares this evening.
Aug. 25: In 2003 the Spitzer Space Telescope was launched. It was the last one of the family of four great space telescopes that started with the Hubble Space Telescope in April of 1990.
Aug. 27: Saturn is at opposition.
Aug. 28: In 1789, William Herschel discovered the sixth largest moon of Saturn, Enceladus. This moon has a warm salty ocean with organic matter under its icy surface.
Aug. 30: The moon passes 2 degrees south of Saturn. Full moon is at 9:36 p.m. This is the closest super moon of the year since its perigee happens less than 10 hours earlier. This is also a blue moon since it is the second full moon of this month.
Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.
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