Gazing into the night sky has sparked my curiosity about the universe since I was a little girl. Imagining each tiny star that twinkles is actually a huge fireball (some several 100’s of times larger than our own Sun) is fascinating to say the least, and puts life’s existence here into perspective. Star-gazing is one of my favorite ways to explore the cosmos from right here on Earth, and I’d like to share this experience with you! The Star Gazer’s Guide will provide some of the upcoming week’s best astronomical events that you can view right from your backyard.
You can use the star chart provided here. And for any terms or units you may be unfamiliar with, I’ve provided a glossary at the end of the guide for your convenience. All events were calculated based on Boulder, CO (latitude 40⁰ N), but should provide good approximations for most cities near the same latitude. If you would like, you can change your location on the linked sites for each event. Let me know if you have any questions. I’d love to know what you see this week!
Across the sea of space, the stars are other Suns. — Carl Sagan
Thursday 10/8
14:08 MDT Moon-Venus Conjunction
The Moon and Venus will be very close, passing within 0⁰39′ of each other. Venus will have a magnitude of -5.3. The conjunction will occur near Regulus of the Leo constellation. Regulus is the brightest star in Leo (front leg) and the 22nd brightest star in the sky, with a magnitude of 1.35. More information here.
20:16 MDT ISS Passing
The ISS will make a visible pass (magnitude -0.8) starting at 10⁰ elevation in the NW and moving Northward. More information here.
Friday 10/9
00:00 MDT Venus near Regulus
Venus will be very near Regulus, the brightest star in Leo.
08:45 MDT Moon-Mars Conjunction
The Moon and Mars will be very close, passing within 3⁰16’of each other. Mars will have a magnitude of 1.5. The conjunction will occur between the Leo and Sextans constellations. More information here.
12:00 MDT Moon, Mars, and Jupiter within a 4 deg circle
Look between the constellations Leo and Sextans.
16:00 MDT Moon near Jupiter
Look near the Leo constellation.
19:23 MDT ISS Passing
The ISS will make a visible pass (magnitude -1.0) starting at 10⁰ elevation in the WNW and moving NNE. More information here.
19:33 MDT Iridium Flare (Iridium 65)
The Iridium 65 satellite will cause an iridium flare of magnitude -7.5 that will be seen as a bright streak across the sky. The flare will begin at an elevation of 51⁰ in the SSE. More information here.
Saturday 10/10
06:10 MDT Iridium Flare (Iridium 43)
The Iridium 43 satellite will cause an iridium flare of magnitude -7.6 that will be seen as a bright streak across the sky. The flare will begin at an elevation of 43⁰ in the S. More information here.
20:09 MDT ISS Passing
The ISS will make a visible pass (magnitude -0.6) starting at 10⁰ elevation in the NNW and moving N. More information here.
Sunday 10/11
06:00 MDT Moon near Mercury
Look near the Virgo constellation.
07:19 MDT Moon at apogee (farthest from Earth)
The Moon will reach the furthest point in its orbit from Earth. The Moon’s distance from the Earth varies because its orbit is not perfectly circular. Instead, the Moon traces out an ellipse with Earth at one of its foci. The Moon’s distance varies by 10% throughout its orbit (between 363,000 km and 405,000 km), which means its size in the night sky varies by nearly 13%. Tonight the Moon will appear to have an angular size of 29.39′, as compared to its average angular size of 31.07′. It should also be noted that the Moon’s apparent size in the sky will also vary depending on its vicinity to the horizon. For instance, the Moon will appear much larger when it is closer to the horizon. More information here.
19:16 MDT ISS Passing
The ISS will make a visible pass (magnitude -0.7) starting at 10⁰ elevation in the NW and moving NNE. More information here.
Monday 10/12
12:19 MDT Mercury at perihelion (closet to Sun)
Mercury will reach the closest point in its orbit to the Sun, 0.31 AU from the Sun. While most of the planets follow nearly circular orbits around the Sun, Mercury has a significantly elliptical orbit, with its distance varying between 0.307 AU and 0.467 AU. This variation of over 50% means that Mercury’s surface receivers over twice as much energy from the Sun at perihelion as compared to apehelion (farthest from Sun). More information here.
20:01 MDT ISS Passing
The ISS will make a visible pass (magnitude -0.6) starting at 10⁰ elevation in the NNW and moving N. More information here.
21:36 MDT Uranus at Opposition
Uranus will be visible near the constellation Pisces, reaching its highest point in the sky around 24:00 MDT. More information here.
Tuesday 10/13
18:07 MDT New Moon
A New Moon occurs when the Moon passes between the Earth and the Sun, such that its lighted side is facing directly away from the Earth (sun-side). While the New Moon can be seen during a more rare solar eclipse, most months the Moon passes just above or below the Sun as seen from the Earth. The New Moon rises and sets with the Sun, and this is why we are unable to see the New Moon–it is hidden in the glare of the Sun during the day. More information here.
15:57 MDT 22P/Kopff reaches its brightest
Comet 22P/Kopff is forecast to reach its brightest of mag 11.3. The comet is located at a distance of 1.56 AU from the Sun and 2.04 AU from the Earth. More information here.
19:09 MDT ISS Passing
The ISS will make a visible pass (magnitude -0.7) starting at 10⁰ elevation in the NNW and moving NNE. More information here.
Wednesday 10/14
19:53 MDT ISS Passing
The ISS will make a visible pass (magnitude -0.8) starting at 10⁰ elevation in the NNW and moving NNE. More information here.
Glossary
Apogee: The point in the orbit farthest away from the Earth.
Apehelion: The point in the orbit farthest away from the Sun.
Arcminute: An angular measurement, defined as 1/60 of one degree. Denoted by ‘. (approx. 1 inch at a distance of 100 yards, the Moon is approx 31’)
Arcsecond: An angular measurement, defined as 1/60 of an arcminute. Denoted by “. (approx. dime at a distance of 1 mile )
A great resource for understanding and approximating angular measurements in the night sky, here. The Moon is approx 1/2⁰. Your outstretched hand is approx 20⁰, with each finger approx 1⁰. Your closed outstretched palm is approx 10⁰.
AU: Astronomical Unit, Defined as the distance between the Sun and Earth.
Conjunction: An alignment of two celestial bodies such that they present the least angular separation as viewed from Earth.
Iridium Flare: Iridium fares occur when sunlight is reflected off the antenna (of one of the 66 active telecommunication sats in LEO, known as the Iridium constellation) directly down at Earth. This reflection causes an illuminated spot on the surface of the Earth. To an observer on the ground, the event appears to be a bright flash, or flare in the sky, which lasts for a few seconds.
ISS: International Space Station. More information here.
Magnitude: A logarithmic measure of the brightness of an object. Brighter objects have a lower (more negative) magnitude. More information here.
Opposition: When a celestial body is opposite the Sun in the sky.
Perigee: The point in the orbit closet to the Earth.
Perihelion: The point in the orbit closest to the Sun.
Time Conversions from MDT
Eastern Daylight Time, EDT = MDT + 2:00
Central Daylight Time, CDT = MDT + 1:00
Mountain Daylight Time, MDT
Pacific Daylight Time, PDT = MDT – 1:00
Alaska Daylight Time, AKDT = MDT – 2:00
The standard for astronomical times is UTC if you happen to come across it, where MDT = UTC – 6:00.
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