The Missing Milky Way
If you go outside soon after dark and look up, you might notice the Milky Way seems to be missing. Fortunately, there’s no cause for alarm. The month of May is the one time of year when the most dense part of our galaxy, that breathtaking band of concentrated starlight stretching from horizon to horizon, isn’t visible in the early evenings.
If you go outside soon after dark and look up, you might notice the Milky Way seems to be missing. Fortunately, there’s no cause for alarm. The month of May is the one time of year when the most dense part of our galaxy, that breathtaking band of concentrated starlight stretching from horizon to horizon, isn’t visible in the early evenings.
Of course, if you live in an urban area (like most of humanity) light pollution made the Milky Way disappear from your night sky long ago. (We’ll talk more about light pollution in a future column.) But even from the darkest sky, you won’t now see the Milky Way unless you stay out a few hours.
Our galaxy, a huge swarm of a hundred billion or more stars, is shaped like a pancake with a bulge in the center. Since we’re inside the pancake, all we see with our naked eyes, even under the darkest sky, are stars and other objects within our home galaxy. (A couple of faint galaxies can barely be seen with naked eyes, but most require binoculars or telescopes.)
So to be precise, virtually everything we see every night is in our Milky Way galaxy, however when we speak of “seeing the Milky Way,” we’re referring to the most densely concentrated band of stars along the plane of the pancake.
The part of the Milky Way we seen in the summer, specifically in the direction of Sagittarius and Scorpius, is toward the galaxy’s center, making the summer Milky Way the richest of the year. During the other seasons, when we’re looking in other directions along the galaxy’s plane, the view isn’t as dramatic.
So, why can’t we see the Milky Way in the early evenings of May? It’s the only time of the year when the galaxy is laying around the horizon, on the same plane with what appears to be the “flat” Earth around us. If you have clear views of the horizon in all directions, you might barely see it hovering just above the horizon, but for all practical purposes, it seems to have temporarily disappeared.
But not to worry — it won’t stay hidden long. As the Earth rotates on its axis, in a few hours the Milky Way will gradually reappear as it rises above the eastern horizon — and the part that rises first is the magnificent Scorpius-Sagittarius central region. So be prepared to be dazzled.
• Sky Calendar.
* May 5 Wed. morning: The Moon is at 3rd quarter.
* 6 Thu. morning: The Eta Aquarid meteor shower peaks, but the 3 a.m. moonrise makes this an unfavorable year for seeing meteors.
* 9 Sun. morning: The crescent Moon is above Jupiter low in the east before dawn.
* 13 Thu.: The Moon is new.
* 15 Sat. evening: The crescent Moon is below Venus low in the west, and then above the brilliant planet the next night.
* 19 Wed. evening: The Moon is below Mars.
* 20 Thu.: The Moon is at 1st quarter.
• Naked-eye Planets. (The Sun, Moon, and planets rise in the east and set in the west due to Earth’s west-to-east rotation on its axis.) Evening: Venus is low in the west, Mars is high in the west, and Saturn is high in the southeast. Morning: Jupiter rises 2 hours before sunrise.
• Star Party. The Central Texas Astronomical Society’s free monthly star party is Saturday, May 8 at the Lake Waco Wetlands beginning at 8 p.m., weather permitting. For directions see my Web site.
Stargazer appears every other week. Paul Derrick is an amateur astronomer who lives in Waco. Contact him at 918 N. 30th, Waco, 76707, (254) 753-6920 or paulderrickwaco@aol.com. See the Stargazer Web site at stargazerpaul.com.
