June 12, 2025: The night sky shows that summer is approaching. The Summer Triangle – Vega, Altair, and Deneb – is in the east-northeast after sundown.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 5:15 a.m. CDT; Sunset, 8:26 p.m. CDT. Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.
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Venus Summary Article
VENUS AS A MORNING STAR, 2025
Sunrise is at its earliest. This continues through the 19th.
Anticipating Summer
Without modern calendars or computers, our ancestors observed the sky and the natural world around them. Unburdened by precise schedules or modern deadlines, they noted the appearance of new plants, the leafing of trees, and the changing night sky. Some tracked the rising and setting of the sun.
With less than two weeks until the summer solstice — the point when the sun’s northward journey along the horizon halts and begins moving southward — the sun’s rising point appears to pause. Without a method for counting days from when the sun last passed a specific horizon landmark during a previous warm season, identifying the exact solstice was nearly impossible. With previous knowledge to determine the solstice, simply anticipating the seasonal shift was a significant moment of the year.
Summer Triangle
Step outside and look eastward about an hour after sunset. Three stars make a large triangle, known as the Summer Triangle. The shape appears in the east-northeast after sundown during this season. It is quite large and the scale is easily missed. The triangle’s vertices are marked by three of the brightest stars in the night sky.
The highest is blue-white Vega. It is high in the sky. Altair is about 10° up in the east. It rises about 15 minutes after sunset and appears slightly higher after sundown. On solstice night it is 15° above the horizon.
Deneb, the dimmest of this triangle trio, is over 20° above the northeast horizon.
Look for the seasonal changes in the sky. The appearance of the Summer Triangle in the eastern sky after sunset is a signal that summer is near.
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