The sky this week from October 22 to 29


saturday 23 october
Cepheus the King is a house-shaped star pattern that surrounds Polaris as one of many circumpolar constellations. This means that it is generally high and easy to observe from many places in the northern hemisphere.

Tonight, let’s zoom in on Herschel’s garnet star, a ruby-red luminous point also cataloged as Mu (μ) Cephei. This magnitude 4 luminary, also called Erakis, is located in the southern part of the constellation, approximately 1.5 ° south of the central point on a line drawn between Alpha and Zeta (ζ) Cephei.

Mu is a cold but bright supergiant star that is one of the brightest suns in our galaxy. While its relatively low temperature certainly contributes to its red color, the veil of galactic dust that lies between us and this star reddens its glow even more. Mu is also a variable star, which clears up and then fades again over a period of about 800 to 1000 days.

Sunrise: 7:20 a.m.
Sunset: 6:08 p.m.
Moonrise: 19:56
Moon setting: 10:11
Moon phase: Gibbous decreasing (92%)

Sunday 24 October
The International Space Station, or ISS, circles the planet about once every 90 minutes at an altitude of 250 miles (400 km). This orbit is constantly changing, so it doesn’t always pass the same place twice every time, but you can easily determine if and when the ISS is visible from your location.

When you see it, the glow comes from sunlight reflecting off the outside of the station as it orbits above your head, even though you can’t see the sun from your location. (This is the same reason why man-made satellites are visible in the night sky.) It usually takes a few minutes for the ISS to cross the sky from a given location, and this morning those in the US Midwest can catch it just before 6:00 a.m. 3:00 p.m. (Hourly in CDT.) The station will appear in visibility in Aries and move to the celestial North Pole near Polaris, then descend to the horizon at Boötes and disappear just before 6 h 20. It will reach a height of 48 ° above the horizon in the north-northwest around 6:16:30 am, blazing with a brilliant magnitude -3.4. You can find out more, including whether it’s visible from your specific location, at

This is in fact the second of two passages that the ISS will make this morning; it is briefly visible for about two minutes from just before 4:42 am, but traverses only a very small region of the sky, from Leo to Coma Berenices, and is of a much lower magnitude –0.3.

The Moon reaches its peak – the farthest point from Earth in its not-quite-circular orbit – at 11:28 a.m. EDT. By that time it will be 252,038 miles (405,616 km) away.

Sunrise: 7:21
Sunset: 6:07 p.m.
Moonrise: 8:33 p.m.
Moon setting: 11:12
Moon phase: Gibbous decreasing (86%)

Monday, October 25
Mercury reaches its greatest aspect ratio in the west at 2 a.m. EDT, when it is at 18 ° from the Sun. From the midwestern United States, the tiny planet rises around 5:50 a.m. local time and has climbed nearly 12 ° above the horizon 30 minutes before sunrise. It blazes with a brilliant magnitude -0.5 in Virgo.

Mercury currently stretches 7 “and is illuminated at 57%. Despite the fact that it will now slowly begin to move towards the Sun in the sky, the fast planet should remain easy to find in the morning for now. It will continue to illuminate a few tenths of magnitude by the end of the month.

If you go out early enough to see a few stars that are still shining, you will see that Mercury is about 3.5 ° below magnitude 2.7 Porrima (Gamma [γ] Virginia). Porrima is one of the most famous double stars in the northern sky, so peek through a telescope if you have the time. Sometimes its stars are too close to separate without a large instrument, but you’re in luck – they’re currently separated by a space large enough (about 3 “) that even small telescopes resolve the two magnitude 3 components, 5. Each is about 1.5 times more massive than our Sun.

It takes nearly 170 years for these stars to complete a full orbit around each other. They last came together in 2005.

Sunrise: 7:22
Sunset: 6:06 p.m.
Moonrise: 9:17 p.m.
Moon setting: 12:09
Moon phase: Gibbous decreasing (78%)

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