As the Northern Hemisphere settles into the scorching heat of summer in July and August, your kids might feel like a panting dog lazing around on a muggy afternoon. It makes sense, but the phrase “dog days of summer” actually has cosmic origins.
The saying comes from an ancient misconception about the brightest star in the sky, Sirius. But there’s no misconception about cool things your kids can spot in the sky between July 3 and August 11—the official dog days. Here’s how to explore this stellar season with your family.
Dog in the sky
Sirius is the brightest star in the constellation Canis Major, or “big dog” in Latin. (The star is in the dog’s nose or neck, depending on the artist.) People have identified a dog shape in this cluster of stars since at least the eighth century B.C., when Greek sky watchers first named the constellation and imagined that it was a companion dog to Orion, the great hunter constellation.
Ancient Greeks, Romans, and Egyptians noticed that during peak summer days—when the heat is most intense—Sirius does something odd: It moves out of the night sky and instead appears at dawn, rising and setting alongside the sun so closely that they couldn’t even see it. (They knew it was there, though, because they watched it move into the dawn sky and then closer to the sun each morning in early summer.) Figuring that the combined power of the sun and Sirius caused the stretch of hot weather each year, these ancient astronomers called those sultry days the “dog days of summer,” after the star in the Canis Major constellation.
At just 8.6 light-years away, Sirius is the brightest star visible in the night sky from anywhere on Earth—it’s nearly twice the size of the sun and shines 25 times brighter. But because it takes 8.6 years for Sirius’s light to reach our planet, it’s too far for any of its heat to affect us. (Our sun is just 8.6 light-minutes from Earth.) The real reason for the summer heat? When the Northern or Southern Hemisphere tilts toward the sun in summer, that hemisphere receives the sun’s rays at a steeper angle, and the atmosphere traps the heat like a blanket.
Because Sirius is so close to the sun during the dog days, you’ll have to wait until the second half of August to get a look. But you can get kids excited about its upcoming reappearance by stargazing during the dog days.
Check out the two bright stars on either side of Orion’s belt. The star on the right is Orion’s foot, named Rigel, 860 light-years away. The orange star to the left of the belt is Orion’s shoulder, called Betelgeuse. About 600 light-years away, Betelgeuse is a monster-size star that makes our own sun look tiny. In fact, if Betelgeuse was where our sun is, it would be as large as Mar’s orbit—Mercury, Venus, and Earth—would be inside. (Keep scrolling to check out the sky chart to locate Betelgeuse and Rigel.)
Early risers can catch sight of the two largest planets in the solar system, Jupiter and Saturn, glinting in the southern skies during the couple hours before sunrise throughout July. (Jupiter is the brighter of the two, on the left.) By early August, these planets rise in the late evening in the east.
With binoculars or a telescope, your kids can see Jupiter’s four largest moons dotting either side of the planet’s disk, and even cloud bands and oval-shaped storms on the planet itself. A small backyard telescope will also reveal Saturn’s rings and a few of its own icy moons.
But those aren’t the only planets to explore: Just after sunset during the second half of July, kids can spot Venus toward the low western sky. Just below and to the right, you can spot much-fainter Mars, which has an orange-red glow because of the iron-rich dust covering the planet’s surface. On July 25, the star Regulus—the brightest start in the constellation Leo—will appear exactly in between these two planets.
Milky Way goodness
From July through September, wait until the darkness of night truly sets in and take your kids on a tour of our home galaxy, the Milky Way. Away from bright city lights, the faint, hazy band of light from hundreds of millions of suns meanders through the overhead night sky. See if kids can spot Jupiter and Saturn to the far left of the galactic cluster.
In the middle of the Milky Way, look for a triangle of three easy-to-find bright stars: Vega, Deneb, and Altair. Making up the Summer Triangle, each star is part of a different constellation: Deneb is in Cygnus the swan, Vega in Lyra the harp, and Altair in Aquila the eagle.
What to watch when the dog days are done
Toward the end of the dog days, the next sky show begins: the Perseids meteor shower. While you can catch a few shooting stars from the Perseids on any clear night between July 17 and August 24, you’ll see the most meteors between midnight and 4 a.m. on the mornings of August 11, 12, and 13.
This meteor shower comes around each year, but because the moon will set mid-evening this summer, the dark sky will show off even the faintest shooting stars. Depending on light pollution levels where you are, your family should be able to see between 30 and 120 meteors an hour.
After that, get ready for the Sirius show to open once again. An hour before sunrise in mid-August, find an unobstructed view toward the low horizon in the eastern sky, and scan the sky for the brightest star visible—you won’t need binoculars or a telescope to spot it. You can also start your search by finding the Orion constellation and looking in a line down and left from the belt.
Sirius isn’t the only very good boy in the sky: Sirius B, nicknamed the Pup, is an Earth-size white dwarf star that orbits Sirius every 50 years. To see it when Sirius is visible in mid-August, bust out your backyard telescope using the highest magnification. It will appear as a faint dot of light just outside the glow of Sirius.
And nearby is Orion’s other companion constellation, Canis Minor, the “little dog.” Find it by looking out for its only bright star, Procyon, below and to the left of Orion.