In the month of May, if you’re in a dark location at northern temperate latitudes, you might be searching for one of the sky’s most spectacular sights, the starlit band of the Milky Way. You won’t find it in the early part of the night. That luminous band of stars arcing across the dome of sky is nowhere to be seen as evening falls in May. Where is the the Milky Way at nightfall this month?
For starters, remember that the disk of our Milky Way galaxy is flat, like a pancake. At northern temperate latitudes, as evening falls in the month of May, the plane of the pancake-shaped galactic disk pretty much coincides with the plane of your horizon.
Because the Milky Way rims the horizon in every direction at nightfall and early evening, we can’t see this roadway of stars until later at night. Then … whoa! Beautiful.
The galactic disk rims the horizon at about 30 degrees North latitude – the latitude of St. Augustine, Florida. Appreciably north of this latitude, the galactic disk tilts a bit upward of the northern horizon. Appreciably south of 30 degrees north latitude, the galactic disk tilts a bit above the southern horizon.
Even so, the Milky Way is pretty much out of sight in our Northern Hemisphere sky during the evening hours in May.
Like the sun, the stars rise in the east and set in the west. If you stay up until late night – near midnight in early May, a couple of hours earlier by June – you’ll begin to see the the stars of the Summer Triangle – Deneb, Vega, and Altair – rising above your eastern horizon.
In a dark country sky, the Milky Way’s band of stars becomes visible as well, for the Milky Way passes right through the Summer Triangle. Watch for it, if you’re up late this month.
Bottom line: The Milky Way’s softly-glowing band of luminescence hides behind the horizon at nightfall and early evening in the month of May. But if you stay up until around midnight, you’ll begin to see the starlit band of the Milky Way rising in the eastern sky.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.