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. Jupiter, Saturn, and Neptune are shown at their midmonth positions. 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 and has 31 days like July, which is named for Julius Caesar. This is the last full month of summer and it will host many interesting celestial events as the days are getting noticeably shorter even as the nights are getting longer once again.

These events include our two largest planets, Jupiter and Saturn, at their best for the year, all five of the brightest planets being visible in the evening sky, a 10th magnitude comet, another asteroid at opposition, and the best display of the annual Perseid meteor shower until 2025.

Saturn in Capricorn will be the first to reach opposition on Aug. 2. The ringed planet will rise at sunset and continue to grace our sky all night long, not setting until sunrise. At zero magnitude, golden-hued Saturn will appear about 15 times (or three magnitudes) fainter than Jupiter, which now rises an hour after Saturn.

Our largest planet, 10 times our size, can be found 15 degrees to the east of Saturn along the ecliptic in Aquarius. Jupiter will reach its own opposition on Aug. 19. Both of these gas giants are in retrograde – or westward motion – against the fixed background of stars for another couple of months. Jupiter’s retrograde will carry it west into Capricorn on Aug. 18, so both of our largest planets will share the same constellation for a while.

Look for the four large Galilean moons, Io, Europa, Callisto, and Ganymede in a good pair of binoculars. Three of them are in a resonance with each other, demonstrating how carefully tuned they are. The fastest and innermost one, Io, makes four orbits around Jupiter for each orbit that the slowest and outermost moon, Ganymede (also the largest moon in our solar system at 3,200 miles in diameter). Then Europa is in the middle, making two orbits for every one that Ganymede makes. It takes Ganymede one week to orbit Jupiter and it is tidally locked with the same side facing the planet, similar to our moon being tidally locked with Earth.

Now is the best time of year to see the two dark belts straddling the equator, called the North and South Equatorial belts. Through a telescope you can also see some of its plumes and festoons. Jupiter rotates in just less than 10 hours, so all these features are moving quite quickly. There are also some mutual occultations and eclipses of its Galilean moons happening this month.

Mercury will form a very close conjunction with Mars low in the western evening sky on Aug. 18. They will get about as close as Saturn and Jupiter did on the winter solstice last year, which was only a tenth of a degree. You may need binoculars to see them since Mars is about 200 times fainter than Venus which is now in Virgo. Mercury and Mars are in Leo, about 20 degrees to the west of brilliant Venus. Then Mercury will drop out of our picture even as Venus continues to slowly climb into our sky, setting about an hour after sunset each evening.

The comet challenge for this month will be a little easier than the one was for last month. Comet 4P/Faye should reach 10th magnitude between the Hyades and Pleiades star clusters in Taurus, so you could see it in a 6-inch telescope. Discovered by Herve Faye in Paris in 1843, it orbits the sun every 7.6 years.

The featured asteroid that will reach opposition this month is named Julia, after Saint Julia of Corsica who was kidnapped, sold into slavery and then crucified for her faith about 1,500 years ago. This asteroid will reach 8.9 magnitude, so it should be easy to see in a small telescope when it reaches opposition on Aug. 24. This will happen in the water jar asterism in Aquarius, just above where Jupiter is now located. Look for it anytime this month other than the four days around full moon from Aug. 20-24. At 90 miles in diameter, Julia is one of the larger asteroids of the roughly one million named asteroids that are in the main belt between Mars and Jupiter.

Edouard Stephan discovered this asteroid in 1866. He also discovered the marvelous group of five interacting galaxies called Stephan’s Quintet located in the constellation of Pegasus about 300 million light years away. That may seem like a huge distance from Earth, but compared to the radius of the known, or observable universe, which is 50 billion light years, that is nearly 200 times closer to us. I have seen this impressive group of galaxies several times through different telescopes, each time thinking that I was seeing about 1 trillion stars all at once in this little part of the sky in Pegasus.

The main highlight for this month will be the annual Perseid meteor shower. They have already started and they will last for most of this month, but they will peak around noon on Thursday, Aug. 12, so the best time to see them would be at night on Aug. 11 into the morning of Aug. 12 and also the next night and morning into Aug. 13. The moon will not interfere since it will only be a slender waxing crescent four days after new and it will set around 10 p.m., which is well before the best time to view meteor showers. The earth spins into any meteor showers that may be occurring after midnight, so that would be the best time to see them. Before midnight we are spinning away from any meteors. That can be compared to looking out the back window of a car during a snowstorm versus looking out the front window as you are driving right into the storm. We start looking out the front window around midnight, but showers usually get even better toward morning. The whole earth can be seen as a relatively small spaceship anyway, so this is a good analogy to orient yourself in space and better understand what is really happening as we are continually orbiting the sun along with the rest of our family of planets in an intricate and complex open helical dance, never to return to the same place in space twice.

You could see over 60 meteors per hour this year, although they will not be evenly spaced out. The Perseids are the second best shower each year right after the Geminids on Dec. 13. Caused by Comet Swift-Tuttle, these are among the fastest meteors of any of the 10 major showers that we can enjoy each year, smashing into our atmosphere at 130,000 mph, or about twice the speed that we are always orbiting the sun. This comet was only discovered in July of 1862, but the Perseids have been recorded for 2,000 years, since 36AD. The comet orbits the sun every 133 years and last visited us in 1992, when it caused greatly increased rates of meteors.

During a close approach of Comet Temple-Tuttle, which causes the Leonid Meteor shower, I saw nearly 1,000 meteors per hour for three hours on the morning of Nov. 18, 2001 from our newly built observatory in Kennebunk. That averaged one every four seconds and there was not a single lull of more than 10 seconds that whole night. We also saw about 15 fireballs, or bolides, that lit up the whole night in brilliant flashes of light and left long, twisting streamers far better and more dramatic and powerful than any man-made fireworks. That was the first and only time that I had a good sense of the real time motion of the earth through space around the sun as we were plowing through all this debris at 67,000 mph.

Most meteors created by showers burn up around 55 miles high, which is considered the edge of space, where both Richard Branson and Jeff Bezos recently visited for a few brief minutes using very different approaches. You need to be within 100 miles of the meteor to see it from your very limited vantage point on Earth. None of the meteors from showers are big enough to survive their fiery plunge and become a meteorite. They are only about the size of a sand grain. About 500 tons of meteoric material enters our atmosphere every single day, which is the equivalent of 20 of the largest sarsen stones used to build Stonehenge.

AUGUST HIGHLIGHTS

Aug. 2: Saturn is at opposition tonight.

Aug. 3: The Messenger spacecraft arrived at Mercury in 2004. We have another mission of the way there now that will arrive in 2025 named BepiColumbo.

Aug. 4: The Phoenix Mission arrived at Mars near its North Pole in 2007.

Aug. 6: The Curiosity Rover launched to Mars in 2012. It is still working, but the much newer Perseverance Rover has greater capabilities.

Aug. 8: New moon is at 9:50 a.m.

Aug. 11: The moon passes near Venus and Mars.

Aug. 12: The Perseid meteor shower peaks.

Aug. 15: First quarter moon is at 11:20 a.m.

Aug. 18: Mercury and Mars will be just a tenth of a degree apart.

Aug. 19: Jupiter is at opposition.

Aug. 20: The moon passes near Saturn.

Aug. 22: The moon passes near Jupiter. Full moon is at 8:02 a.m. This is also known as the Sturgeon, Green Corn, or Blueberry moon.

Aug. 30: Last quarter moon is at 3:13 a.m.


Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.


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