Fall’s night sky: Stars that twinkle, planets that shine

The waning crescent moon and the planet Venus can be easily seen before sunrise Sept. 17 and 18.

While the recent eclipse drew people’s attention to the daytime sky, Steven Velasquez said each season of the year has its own interesting sights in the night sky.

Velasquez, chairman of the mathematics and physics department at Heidelberg University, said knowing which stars and planets to look for can be a good, ongoing study of astronomy.

“We can identify most of the things in the night sky, things that I look at and know Galileo looked at,” he said.

Galileo Galilei (1564-1642) was an Italian astronomer, physicist, engineer, philosopher and mathematician whose observations laid the foundation for modern physics and astronomy.

“If it’s really bright, it’s probably a planet,” Velasquez said. “The planets are typically brighter than most of the stars.”

IMAGES FROM THE WEBSITE, EARTHSKY.ORG The moon can guide the eye to the planet Saturn and the star Antares Sept. 25-27.

He said the old adage “twinkle, twinkle little star” provides a way to determine the difference between planets and stars.

“A star is so far away it’s literally just a pin hole,” he said. “A star will always appear to be shimmering. A planet is a dot, but bigger, and never twinkles.

“If it’s shimmering a little bit, it’s going to be a star,” he said.

He said four or five planets are visible in the night sky in the fall.

“Let’s start with the moon,” he said. “It’s very recognizable.”

Watch for the waxing crescent moon to join up with the planet Jupiter after sunset Sept. 21 and 22.

Every full moon has a name.

“The names come from Native American tradition,” he said.

In the fall sky, he said, full moons can be seen on: Sept. 6, Corn Moon; Oct. 5, Hunters’ Moon; Nov. 4, Beaver Moon; and Dec. 3, Cold Moon.

Velasquez said people often notice the sky during a full moon, but the best time to see the rest of the sights in the night sky is at a new moon, when it’s darkest two weeks before and after a full moon.

“A new moon is the best time to see the stars, because the full moon bleeds light across the sky, making it harder to see,” he said.

One planet that can be seen in the fall is Venus.

“If you’re a morning person, look about two hours before sunrise,” he said.

Venus can be found in the eastern sky.

“Venus, like the moon, goes through phases,” he said. Sometimes it’s seen as a crescent and sometimes full like the moon.

“This helped give credence to Copernicus’s theory that the sun was the center of the universe,” he said.

Nicolaus Copernicus (1473-1543) was a mathematician and astronomer who formulated the idea that the sun was the center of the universe, rather than the Earth, as had been the accepted knowledge of the time.

Mercury and Mars also can be seen in the fall, Velasquez said. Both planets can be found in the east near sunset close to the sun, especially around Sept. 16.

“Mercury is really close to the sun,” he said. “Mars is more distinctive because of the red. Mars in rusty. Most people don’t know that.”

Mercury, below Venus, is visible before sunrise in September, but timing is critical.

“If you look too soon, Mercury will still be under the horizon,” according to the website, EarthSky.org. “If you look too late, it will be obscured by the morning twilight.”

Watch for Mercury low in the sky, and near the sunrise point on the horizon.

Find Mercury and the star Regulus beneath Venus Sept. 10, and then the moon and Venus can help guide the eye to Mercury and maybe Mars Sept. 16.

Sky watchers also can find Jupiter this fall.

“Jupiter is actually visible in the lower portion of the sky in the southwest and west near the constellation Virgo,” Velasquez said.

To find Virgo, he suggested finding the Big Dipper, which most people know how to find.

“It looks like a pot with a bent handle,” he said.

The Big Dipper points toward Virgo, and its brightest star, Spica. Jupiter shines in front of the constellation Virgo. Spica disappears from the evening sky in October but can be seen near Venus in early November.

To find Jupiter, look low in the southwest to west as darkness falls. It sinks in a westerly direction throughout the evening. The bright planet disappears from the evening sky in October, but reappears in the morning sky in November.

Jupiter and Venus are in close proximity in the morning sky Nov. 13, and the moon and Jupiter can be found near each other Sept. 21-22.

“If you have a small telescope, you can see the four moons of Jupiter,” Velasquez said.

Saturn, the ringed planet, also can been seen at this time of year.

“Sometimes you can see the rings and sometimes not,” he said, depending on movement around the sun and its own movement.

Saturn’s biggest moon, Titan, also can be seen.

“With a moderate telescope you should be able to see Titan,” he said. “It’s the only moon with an atmosphere.”

To keep up to date on astronomy, he suggested checking the website EarthSky.org.