The sky this week from September 9 to 16
Sunday September 11
The Moon passes 1.8° south of Jupiter at 11:00 a.m. EDT. This evening, our satellite has moved towards Cetus and is 6.5° east of the gas giant two hours after sunset.
As the bright Moon rises in the east, let’s turn our gaze to the west. There you will find Vega of magnitude 0, which ranks as the fifth brightest star in the sky. Less than 2° northeast of Vega is Epsilon (ϵ) Lyrae, also known as the Double Double Star. Indeed, when viewed through a telescope at 75x or greater magnification, this single bright spot splits into two distinct pairs of stars. The northern pair is cataloged as Epsilon1, while the southern pair is Epsilon2. Epsilon1 is composed of two stars of magnitudes 5.1 and 6, separated by 2.6″; Epsilon2 contains stars of magnitudes 5.1 and 5.4, separated by 2.3″. See if you can capture both pairs with bright Vega in a single field of view.
Sunset: 7:15 p.m.
Moonrise: 8:15 p.m.
Moon setting: 7:50 am
Moon phase: Waning gibbous (98%)
monday september 12
Orion and his two trusty hounds stand high in the early morning sky. An hour before sunrise, look east to find the familiar three-star asterism in Orion’s belt, along with its trusty sword hanging about 3.7° south of the outermost star. east of the belt, magnitude 1.7 Alnitak. The sword, which appears out of focus to most people, contains the famous Orion Nebula (M42), a rich region of nearby star formation that is absolutely stunning through a telescope. Even with the waning gibbous Moon in the sky, it’s worth a look if you have a medium or even small telescope.
Some 30° east of Orion’s belt is Canis Minor, Orion’s smallest hunting dog. The brightest star in this constellation is Procyon of magnitude 0.4, which marks the little dog’s nose. Just 11.4 light years away, Procyon is the eighth brightest star in the sky.
Let’s slide up this chart and then visit Sirius, the brightest star in the sky. Also called the Dog Star, this luminary marks the nose of Canis Major the Big Dog and lies nearly 26° southwest of Procyon. With a Greek name that literally means ‘burning’ or ‘scorching’, you can’t miss this magnitude -1.4 star! But there’s something else you couldn’t miss: So close to the horizon, Sirius can seem to flicker violently or dance in place. Turn binoculars or a telescope over it, and you can even see it change color, shimmering as if looking at it through a kaleidoscope. This effect, called scintillation, occurs when you observe starlight through Earth’s turbulent atmosphere, blurring your view. The brighter a star and the closer it is to the horizon, the greater the effect.
Sunset: 7:14 p.m.
Moonrise: 8:39 p.m.
Moon setting: 8:59
Moon phase: Waning gibbous (93%)
tuesday september 13
While the Double Double we observed in Lyra earlier this week required a telescope to fully separate, tonight we’re going to test your naked-eye skills. First, find the Big Dipper, that famous Ursa Major asterism to the north. Early in the evening, it is upright and swaying under Polaris, the North Star. Locate the last star at the end of the Big Dipper’s handle – it’s Alkaid, also known as Eta (η) Ursae Majoris.
Now look for a star inside, the “kink” in the handle. Do you see a star or two? The obvious bright star that most people recognize in the handful is Mizar of magnitude 2.3. But just under 12 feet to the northeast is Alcor of magnitude 4 – much fainter, but still visible to the naked eye. Some people like to use this widely separated pair as a visual acuity test. How do you score?
Mizar and Alcor can see close in the sky, but they are not considered a binary pair. This is because they are separated by a full light year, so they cannot be linked and orbit around each other. Nonetheless, they appear to be related, as the two travel together across the galaxy in the same direction and at the same speed, with several other stars in the Big Dipper that together form the Ursa Major Moving Group.
Sunset: 7:12 p.m.
Moonrise: 9:05 p.m.
Moon setting: 10:07
Moon phase: Waning gibbous (87%)
Wednesday September 14
The Moon passes 0.8° north of Uranus at 7:00 p.m. EDT. If you want to try and spot the pair, you’ll have to wait until they come up after dark, located in Aries the Ram. The Moon is now just under 3.5° east of the ice giant, whose magnitude 5.7 glow can be a bit difficult to spot with binoculars or a telescope with our satellite so close. However, that doesn’t stop you from trying to spot the grayish 4-inch-wide disc of Uranus to the west of the Moon.
According to NASA, today also begins the shortest solar day of the year. While days on Earth are always considered to be 24 hours long, the length of the solar day – defined as the time between two successive times when the Sun is highest in the sky – varies throughout the year. . The shortest day, as measured between two consecutive solar noons, usually occurs in September, and this year begins at solar noon today and ends at solar noon tomorrow. Its duration is 23 hours, 59 minutes and 38.6 seconds.
Sunrise: 6:40 a.m.
Sunset: 7:10 p.m.
Moonrise: 9:33 p.m.
Moon setting: 11:14 a.m.
Moon phase: Waning gibbous (80%)