What you will see on a clear night
Shorter days and dropping leaves are sure signs we are quickly approaching (or already into) fall. Another sign: the way some constellations are shifting to the west, as though drawn by a giant magnet.
Even though we’re experiencing cooler weather, it doesn’t mean that we can’t lean back in a lounge chair with a pair of binoculars to become familiar with constellations and other star groups.
It means we need a sweater or a jacket to observe stars and the Moon’s craters. Then use a telescope to examine fine details of the Moon, Jupiter (and four of its moons), as well as some double stars.
Circle Sept. 23 on your calendar. That’s the fall equinox, making it the first day of fall. Summer changes to fall at precisely 5:05 am.
On Sept. 23 the Sun will be above the horizon for about 12 hours and below the horizon for about 12 hours. (The last time this happened was on March 20, when the spring equinox marked the beginning of spring). After Sept. 23, the days will become shorter and the nights longer.
Even though summer has come and gone, the SUMMER TRIANGLE--a dramatic arrangement of stars—is still with us. Although technically not a constellation, the enormous Summer Triangle comprises three very bright stars that were high overhead in July and August. Since then, these stars have moved a little to the west.
The brightest of the three stars is VEGA, which started to rise over the northeast horizon in early May. Vega, the third brightest star in the entire night sky--after SIRIUS and ARCTURUS--is in the western sector of the triangle. The remaining stars comprise DENEB in the northern sector and ALTAIR in the south.
The three stars of the Summer Triangle are part of three constellations. Vega is in LYRA (The Lyre), Altair is in AQUILA (The Eagle) and Deneb is in CYGNUS (The Swan). Deneb serves as the swan’s tail while the star ALBIREO at the far end is the swan’s head. The wings are at right angles to the body.
Cygnus is also known as the NORTHERN CROSS due to its shape. The swan’s wings double as the arms of the cross while the swan’s body doubles as the cross’s shaft.
Albireo at the south end of the swan (or the cross) within the Summer Triangle) is a double star. You will need binoculars or a telescope to pick out two stars of different colours; one is blue (hotter than the Sun) and the other is yellow (similar to the Sun, although somewhat cooler).
Amateur astronomers use a special trick with their telescope to accentuate the colour of a star; they adjust their focus knob so that the star goes out of focus. Vega is a prime example; by putting it out of focus, you will see that it is a bluish-white star.
The Summer Triangle has moved from the eastern sector of the sky (in May) to the western sector because most constellations relocate from east to west as the Earth rotates around the Sun. Star groups such as the Summer Triangle and constellations such as ORION, which are well below the NORTH STAR, rise above the eastern horizon and then disappear below the western horizon during a portion of the year. Orion will return next winter at which time The Summer Triangle will disappear.
The most popular group of stars is the Big Dipper. All you have to do is look north and there it is; a four-star bowl with a three-star handle.
The seven-star Big Dipper is in the constellation Big Bear. The Big Dipper is a well-known group of stars as it can be seen year-round. This is because it is close to the North Star (Polaris), making it a circumpolar grouping.
Most constellations like Orion and the Summer Triangle are known as seasonal constellations because they are far from the North Star and slip beneath the western horizon after travelling for a few months across the night sky.
The Big Dipper can be used to find the NORTH STAR. First, find the bowl. Then draw an imaginary line up and beyond the two end stars of the bowl and you will locate the NORTH STAR. Many people think that the North Star is the brightest in the night sky. Not true! It’s way down on the brightness scale.
The North Star (which remains in one spot year-round) is the lead star of the seven-star LITTLE DIPPER, which pours into the Big Dipper. But you have to be at a very dark site—like a farm or a cottage away from city lights—to be able to make out the Little Dipper.
There is something unique about one of the seven stars of the Big Dipper. Look carefully at the second star from the end of the Dipper’s handle and you’ll spot a double star, ALCOR & MIZAR. The star duo is more definitive with binoculars or a telescope.
The brightest star now in the night sky (as it was in summer) is Arcturus, replacing Sirius, last winter’s titleholder. Here’s how you find Arcturus: First, locate the BIG DIPPER high overhead. Then draw an imaginary arc-shaped line beyond the handle of the Big Dipper and you will see Arcturus.
That’s why some astronomers say, “Let’s arc to Arcturus.” However, don’t wait too long to find it as it disappears over the western horizon in late September.
The largest planet in the solar system, Jupiter, is now (mid-Sept.) visible around midnight. It would be best to wait until mid-Oct. when it will appear shortly after it gets dark as a very brig"t “s"ar” in the east.
Jupiter appears as a star because it's five times as far from the Sun as the Earth. Since it’s so far away, it takes a long time to circle the Sun. If you are 12 years old, you have something in common with Jupiter: the time you've been on Earth is the same the gaseous planet has taken to orbit the Sun once.
Jupiter, the fifth planet from the Sun, is a huge gas ball of helium and hydrogen. Its diameter of 143,000 km is so big that 11 Earths could fit across it. To put it another way, its volume could contain as many as 1,300 Earths.
Are you aware there are about 150 moons in the solar system? Because of the powerful magnetic fields of the four gaseous planets—Jupiter, Saturn, Uranus and Neptune—they have most of the moons. Since Jupiter has 65 moons, some observers refer to the giant planet as a mini solar system.
If you aim a telescope at Jupiter, you will see more than a white disc (as well as some parallel lines representing layers of gas). Look closely and you’ll spot the planet’s four largest moons. Jupiter’s remaining 61 moons are too small to be seen.
Even though these four moons appear as tiny dots, they are about the same size as the Moon. They are always in a straight line because they are rotating around Jupiter’s equator. Usually they appear in three patterns: (1) three on one side and one on the other, (2) two on either side, or (3) four on one side.
If only three moons appear, it means one is either in front of (or behind) Jupiter. The four largest moons, called IO, EUROPA, GANYMEDE and CALLISTO, are known as the Galilean moons after Galileo who discovered them four centuries ago.
You can Google the moons to learn about their surface features and size. For example, an ocean capped with fractured ice fields covers Europa. There might be microscopic life in that frigid ocean!
The brightest object in the night sky--some astronomers say the most rewarding—is the MOON. Between September 19 and Oct. 29, you'll see the Moon display it's early evening phases:
- Sept. 19 and Oct. 18: crescent Moon
- Sept. 22 and Oct. 21: first quarter Moon
- Sept. 29 and Oct. 29: full Moon
Where to look for the Moon after sunset? The crescent phase will appear in the west, the quarter phase in the south and the full Moon in the east.
Did you know that the Moon's craters are the result of our closest celestial object being pummelled and battered by giant space rocks or asteroids? If the Moon had an atmosphere, the craters would have long eroded away from wind and water erosion like what happened here on Earth. But because there is no atmosphere on the Moon, the craters have not changed ever since they were formed.
The Moon’s craters and mountains are most dramatic if you look near the terminator—the line that separates the dark side from the sunlit side. That’s because the shadows created by the Sun are the longest. If you look through a telescope, you can even spot crater walls disappearing into the shadows.