Here are this week’s best astronomical events that you can view right from your backyard. Happy exploring!
Astronomy compels the soul to look upward, and leads us from this world to another. — Plato
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!
Thursday 10/22
05:17 MDT Hubble Passing
The Hubble Space Telescope will make a visible pass (magnitude 3.4) starting at 11⁰ elevation in the South and moving SSE. More information here.
19:18 MDT ISS Passing
The ISS will make a visible pass (magnitude -3.3) starting at 10⁰ elevation in the NW and moving SE. More information here.
Friday 10/23
05:09 MDT Hubble Passing
The Hubble Space Telescope will make a visible pass (magnitude 3.3) starting at 12⁰ elevation in the SSE and moving SE. More information here.
06:47 MDT Hubble Passing
The Hubble Space Telescope will make a visible pass (magnitude 3.0) starting at 10⁰ elevation in the SW and moving SE. More information here.
20:03 MDT ISS Passing
The ISS will make a visible pass (magnitude -0.6) starting at 10⁰ elevation in the W and moving SSW. More information here.
Saturday 10/24
05:00 MDT Hubble Passing
The Hubble Space Telescope will make a visible pass (magnitude 3.3) starting at 13⁰ elevation in the SSE and moving SE. More information here.
06:37 MDT Hubble Passing
The Hubble Space Telescope will make a visible pass (magnitude 3.0) starting at 10⁰ elevation in the SW and moving SE. More information here.
19:09 MDT ISS Passing
The ISS will make a visible pass (magnitude -1.4) starting at 10⁰ elevation in the WNW and moving SSE. More information here.
Sunday 10/25
03:28 MDT Venus-Jupiter Conjunction
Venus and Jupiter will be very close, passing within 1⁰01’ of each other. Venus will have a magnitude of -5.1, while Jupiter will have a magnitude of -1.8. Both will be located in the constellation Leo. From Boulder, the pair will be visible at dawn, rising at 03:28 MDT and setting at 07:05 MDT around sun rise. More information here.
03:59 MDT Moon at Aphelion (farthest from Sun)
The Moon will reach the furthest point in its orbit from the Sun, at a distance of 0.9965 AU. The Moon will lie on the opposite side of the Earth as the Sun. For comparison, the Earth will lie at a distance of 0.9944 AU from the Sun. More information here.
19:45 MDT Asteroid 29 Amphitrite at Opposition
Asteroid 29 Amphitrite will be well placed for observation in the constellation Aries and will remain high above the horizon for much of the night. Regardless of your location on Earth, 29 Amphitrite will reach its highest point in the sky around midnight. From Boulder, it will become visible around 19:45 MDT and set at 05:24 MDT when it sinks below the western horizon. Its highest point will occur around 00:36 MDT, 67⁰ above the southern horizon. More information here.
20:00 MDT Iridium Flare (Iridium 76)
The Iridium 76 satellite will cause an iridium flare of magnitude -7.8 that will be seen as a bright flash across the sky. The flare will begin at an elevation of 41⁰ in the SE. More information here.
Monday 10/26
03:28 MDT Venus at Greatest Elongation West
Venus will be at its greatest separation from the Sun and well placed for observation in the dawn sky. From Boulder it will rise at 03:28 MDT and attain an elevation of 38⁰ above the SE horizon before dawn break around 07:02 MDT. More information here.
18:01 MDT Moon at Perigee (closest to Earth)
The Moon will reach the closest point in its orbit to the Earth. This close approach occurs when the Moon is near full phase, and so the Moon will appear unusually large and bright (called a supermoon). 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 33.32′, 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.
18:18 MDT Iridium Flare (Iridium 64)
The Iridium 64 satellite will cause an iridium flare of magnitude -4.6 that will be seen as a bright flash across the sky. The flare will begin at an elevation of 41⁰ in the SSW. More information here.
18:22 MDT Moon-Uranus Conjunction
The Moon and Uranus will be very close, passing within 0⁰52’ of each other. The Moon will have a magnitude of -12.8, while Uranus will have a magnitude of 5.7. Both will be located in the constellation Pisces. From Boulder, the pair will be visible in the evening sky, starting around 18:22 MDT (10⁰ above the eastern horizon) and sink from view around 0529 MDT. It will reach its highest point in the sky around 23:46 MDT with and elevation of 56⁰ above the southern horizon. More information here.
19:15 MDT NGC-869 Well Placed
The open star cluster NGC-869 will be well placed for observation in the constellation Perseus. From Boulder, it will be visible all night, starting around 19:15 MDT at dusk 33° above the NE horizon. It will reach its highest point in the sky around midnight local time and will be lost around dawn at 06:22° above the NW horizon. It will not be visible from latitudes much south of 12° S. More information here. See NGC-884 below.
Tuesday 10/27
18:45 MDT Full Moon
The Moon will reach full phase, lying almost directly opposite the Sun in the sky. This full moon will take place unusually close to the time when the Moon is closest to Earth (perigee). As a result, this full moon will appear slightly larger and brighter than usual in the sky. Such full moons are called supermoons and occur roughly once every 13 months. Full moons are traditionally given names according to the season in which they occur. This will be the second full moon of autumn, and thus will be called the Hunter’s Moon. More information here.
19:14 MDT NGC-884 Well Placed
The open star cluster NGC-884 will be well placed for observation in the constellation Perseus. From Boulder, it will be visible all night, starting around 19:14 MDT at dusk 33° above the NE horizon. It will reach its highest point in the sky around midnight local time and will be lost around dawn at 06:38° above the NW horizon. It will not be visible from latitudes much south of 12° S. More information here. See NGC-869 above.
Wednesday 10/28
06:02 MDT Hubble Passing
The Hubble Space Telescope will make a visible pass (magnitude 3.1) starting at 11⁰ elevation in the SWW and moving South. 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.
Elongation: The angle between the Sun and a planet, with Earth as the reference point. The greatest elongation of a planet occurs when this separation angle is at its largest. More information here.
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.
Radiant: The point in the sky where meteors of a meteor shower appear to originate.
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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