Name: Astronomy Day
Start: 2026-09-19
End: 2026-09-19

Here’s a brief look at what’s going on in the Mile High City this week.

September 21:

NASA ends Galileo's mission — NASA ends Galileo’s mission

On this day in 2003, NASA ended the Galileo spacecraft’s mission by sending it into Jupiter’s atmosphere after nearly eight years exploring the giant planet and its moons.

September 22:

Space Telescope Science Institute: How to Image Alien Worlds with Dr. Emily Rickman, ESA: Free, online event via YouTube: 5:00PM
The September Equinox occurs, when the Sun reaches the point along the ecliptic where it crosses into the southern celestial hemisphere marking the start of autumn in Denver: 6:07PM

September 23:

Catch Jupiter and Mars in the eastern morning sky. Look for the gas giant in Cancer and the red planet in Gemini from about 4:00AM until dawn.

September 24:

Standley Lake Stargazing: Weekly Livestream: Free Online program via Zoom: 6:00PM

September 25:

International Observe the Moon Night at Eldorado Canyon State Park

Standley Lake Stargazing: International Observe the Moon Night: Free, in-person event at Eldorado Canyon State Park: 7:00PM
CU Boulder Observatory Open House: Free, in-person event at Sommers-Bausch Observatory: 9:00PM
Astronomy on Tap – Boulder: Free, In-person event at Rosetta Hall: 8:00PM

September 26:

Full Harvest Moon: 10:49AM
FREE Full Moon Queso and Chips from QDOBA with the purchase of an entrée.

September 27:

Look for the waning gibbous Harvest Moon near Saturn in the constellation Pisces rising in the east around 8:00PM

This Week’s Solar System Summary:

The Sun shifts from rising about 6:46 AM to 6:52 AM, while sunset moves from 6:58 PM to 6:48 PM, bringing noticeably shorter days as we approach the end of September.
The Moon rises in the afternoon at the start of the week and shifts into the evening by the weekend, while moonset moves from late evening into the morning hours.
Mercury remains low in the western sky after sunset and is still difficult to see in the bright twilight.
Venus shines brilliantly in the western sky after sunset and reaches its greatest brightness this week, making it an especially striking sight despite its low altitude.
Mars rises in the early morning and can be found low in the eastern sky before sunrise. It remains relatively faint but is slowly becoming more prominent.
Jupiter rises during the early morning hours and is becoming an increasingly easy target before sunrise in the eastern sky.
Saturn rises in the evening and remains visible throughout most of the night. It is well placed for evening observing and continues to improve as it approaches opposition in early October.
Uranus rises during the evening and remains visible through the night. It can be found with binoculars or a telescope under dark skies.
Neptune rises in the evening and remains visible through most of the night. It reaches opposition this week, making this an excellent time to observe the distant planet with a telescope.

This Week’s Meteoric Activity:

You can keep track of the activity of meteor showers as well as those beyond the limits of visual observing by visiting the NASA Meteor Shower Portal.

Anthelion (ANT): 2:00 AM near Aquarius/Pisces: About 1–2 per hour
September ε-Perseids (SPE): 5:00 AM in Perseus: Less than 1 per hour. Activity ends September 23
Southern Taurids (STA): 1:00 AM in Taurus: Less than 1 per hour. Activity begins September 20
χ-Cygnids (CCY): 10:00 PM in Cygnus: Less than 1 per hour
August β-Piscids (BPI): 3:00 AM in Pisces: Less than 1 per hour