The Milky Way Inside and Out

AS02 - Milky Way Inside & Out

The 108-page special issue with galaxy foldout from Astronomy magazine takes you on a tour of our galaxy. You’ll discover how the galaxy was formed, what makes stars explode, what's at the heart of the Milky Way, everything you know about exoplanets, and so much more!

United States
Kalmbach Publishing Co. - Magazines
8,64 €(TVA Incluse)

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3 min
our city of stars

From a dark site on a clear summer night, you’ll see a band of light arching across the sky. Thousands of years ago, people imagined the milk of a goddess had spilled across the heavens. They called the region Via Lactea (the Milky Way). But it was Galileo Galilei who first looked at the Milky Way “close-up,” more than 400 years ago. He aimed his simple refracting telescope toward this band of light and wrote that he could resolve many more stars than he could see with his naked eye. This simple observation started subsequent astronomers on a quest to understand our galaxy’s structure. We now know the Milky Way is a barred spiral galaxy. Four curved stellar arms — regions where a great deal of star formation occurs — radiate outward…

11 min
recipe for a galaxy

Spend some time under the stars on any clear, dark night away from city lights, and you’ll notice a misty lane arching overhead across the sky. Recognized since antiquity, this luminous glow was associated with a heavenly path or celestial stream by most ancient peoples. The Romans called it Via Lactea, or the Milky Way. But a name used by a tribe in South Africa’s Kalahari Desert better hints at this glowing lane’s true nature: “The Backbone of the Night.” For the Milky Way is nothing less than the full structure of our galaxy seen edgewise. As 18th-century scientists began to realize this, the Roman name for a cosmic highway became our galaxy’s name. When Galileo Galilei turned his spyglass to the Milky Way in 1610, he revealed for the first time…

8 min
meet the stars next door

Most of the space in the Milky Way Galaxy can be pretty lonely — a dull, dark void. But our own neighborhood stands out as among the more intriguing places in the universe. Recently, with new telescopic technologies, astronomers have made big strides toward finding all our stellar neighbors. Knowing the stellar cast, they can then project this information into the galaxy at large to help us learn how stars, and even planets, are born and live out their lives. As a result of these studies, astronomers are now learning how our own Sun fits into the overall picture. Neighborhood cliques If we define our galactic neighborhood as a sphere just over 30 light-years across and centered on the Sun, it encompasses several planetary systems. Within this sphere lie 71 stars (including…

2 min
spectra — one of astronomy’s greatest tools

Organizing stars If you spread starlight into a rainbow — a spectrum — from violet through red, you will see absorption lines cutting out narrow bands of color. Each line is produced by a specific atom or ion. More than a century ago, stars were organized into classes O, B, A, F, G, K, and M according to the lines present in their spectra. Astronomers later realized this scheme corresponds to a temperature scale that runs from 50,000 kelvins (90,000 degrees Fahrenheit) at the top (class O) to a bit above 2,000 K (3,100 F) at the bottom (class M). In the past few years, astronomers have added cooler classes (L and T) with surface temperatures down to hundreds of kelvins. Each class is divided into 10 parts from warm to cool; the…

1 min
future close passages

Close stellar encounters Our galaxy is in constant transition, and nearby stars present a few possible dangers. As stars orbit the galaxy, they constantly change positions relative to each other. Someday, a supergiant will invade our neighborhood, and, at Alpha Centauri’s distance, it could shine with the light of 20 Full Moons. Even at 30 light-years, were it to explode, the results could severely damage Earth’s atmosphere and alter life processes. Radioactive isotopes in Earth’s ocean beds confirm that such an event actually has happened. And don’t discount the potential effects of red dwarfs. Trillions of comets, ejected from the early solar system, surround the Sun. They form the Oort Cloud, which extends a good part of the way to Alpha Centauri. While local stars don’t collide, they still can come close…

1 min
defining distances

Astronomers could measure the distances to stars in miles, but the numbers get big. Instead, they use the light-year, the distance light travels in a year. The universe’s top speed is the speed of light: 186,282 miles per second. The 31.56 million seconds in one year means one light-year stretches for 5.87 trillion miles (roughly the distance the U.S. population drives annually). The fundamental unit in astronomy, the astronomical unit (AU), is the average distance between Earth and the Sun: 93.2 million miles. This makes the light-year 63,240 AU long, just a bit short of the number of inches in a mile.…