Have you had that ‘blanket of stars’ moment when you’re standing under the starriest sky you’ve ever seen and you wonder … what is all that? What am I looking at? Why has no-one taught me anything about the stars?
Where are we?
The night sky is just geography, and learning a little about what you can see can give you powerful doses of both wonder and perspective. Forget ‘why are we here?’. No-one knows that. Ask ‘where are we?’. That’s a much more interesting question and has some incredible answers that are best realized by stargazing. It’s a journey of discovery that’s best shared.
So here are five things to find in the night sky from May through September, and the story behind them. Arm yourself with a planetarium app to help you find the star or planet in question, and with the stories and facts below about the significance of what you’re looking at, you’re all set to learn and share these secrets of the cosmos with friends and family. Attention spans are short, so don’t try too hard.
1. Meet the neighbors
Start at the beginning. If you’ve got a clear sky, start by asking your fellow stargazers what they’re looking at. Answers will likely include ‘the Universe’, ‘the Milky Way’ and the vague ‘some stars’. You’re looking at our neighborhood. Almost everything you can see with the naked eye are stars that are bright enough because they are (a) bigger than most stars and (b) relatively close to us. Some others are bright because they are colossal, so despite being far away, they’re still bright enough to see. You just saw the night sky in 3D!
From the northern hemisphere, it’s not possible to see the nearest visible star to the Sun, Alpha Centauri, while Sirius, the Dog Star and the brightest star in the sky, isn’t visible in summer. So direct your stargazing friends towards Vega, just 27 light years away and an anchor star of the summer night sky in the northern hemisphere.
- Fact: there are 45 known stars within 17 light years of the Sun according to NASA
- Fact: There are thought to be between 200-400 billion stars in the Milky Way
2. Jupiter and its moons
For some, finding out that other planets in the solar system have moons will blow their minds. However, only one planet’s moons are visible from here. Io, Europa, Ganymede and Callisto are the four so-called Galilean moons of Jupiter. The giant planet is at opposition (i.e. the brightest of the year) on June 10, 2019, but point any pair of binoculars or a small telescope at Jupiter at any time of night this summer and you’ll see some or all of those moons in a line. It’s a beautiful sight.
- Fact: Ganymede is bigger than Mercury
- Fact: Europa has a salt-water ocean beneath an ice sheet that could contain life
3. The Summer Triangle
From mid-June look out for the three bright stars rising in the east. First comes Vega in Lyra, then Deneb in Cygnus, and finally Altair in Aquila. Why? Firstly, it’s a classic seasonal asterism (a shape, but not a constellation) that single the arrival of summer. Secondly, it’s directly over the Milky Way (which runs behind it through Deneb and Altair). Thirdly, it’s a great lesson in star nearness and brightness that we already discussed. Though all three stars look similar in brightness, Altair is a mere 17 light years distant and Vega just 27 light years. However, Deneb is a whopping 1,500 light years away at least. That’s just about as distant a star it’s possible to see. Why so bright? Deneb is the Milky Way’s most luminous star, a blue-white supergiant that’s about 2o0 times bigger than the Sun.
- Fact: Deneb is 200 times the size of the Sun.
- Fact: Close to Vega and Deneb is where the Kepler Space Telescope found the majority of the 4,000+ exoplanets so far discovered.
4. Our home the Milky Way
Are there any more impressive sights than the Milky Way arching across the sky? This collection of 200 billion+ stars is our home, though the fact that we can see a lot of it during summer tells you that we’re some distance from the center (in winter we’re looking away from the center). In fact, we’re orbiting an average star in the Orion Arm, a minor spiral arm of the Milky Way. From around June until October the Milky Way is visible soon after dark, though you must (a) only look when the moon is down (the last few days of each month in 2019 are ideal). You can see the Milky Way in the south-east, streaming down through the Summer Triangle.
- Fact: The Milky Way is a barred spiral galaxy much like billions of others in the Universe
- Fact: The Sun orbits the center of the Milky Way about once every 230 million years.
5. Arc to Arcturus, spike to Spica
Now look north for the Big Dipper/The Plough, one of the most recognizable asterisms (shapes) of all. Not a constellation? No. It’s the central part of Ursa Major, the Great Bear (finding the bear’s feet and the tail is fun since they’re mostly all easy-to-see double stars). Follow the stars of the Big Dipper’s and it leads in an easy ‘Arc to Arcturus’, a massive and very bright orange (and obvious) star in the constellation of Bootes, 37 light-years away from us. Arcturus is often mistaken for Mars (though only every other year when Mars passes close by, as it will next in 2020).
Now take a ‘spike to Spica’, the next bright star closer to the horizon. About 250 light-years away, Spica is actually a binary star; it’s two stars orbit each other every four stars. So what? Well, as it turns out, most of the stars we can see are, in fact, binary stars …
- Fact: Arcturus is the closest giant star to Earth and it’s moving erratically through the Milky Way, so may have come from another small galaxy that merged with the Milky Way.
- Fact: Most of the stars in the Big Dipper constitute the closest star cluster to the Sun.