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Anne Dirkse, Flickr // CC BY-SA 2.0
Anne Dirkse, Flickr // CC BY-SA 2.0

10 Astonishing Things You Should Know About the Milky Way

Anne Dirkse, Flickr // CC BY-SA 2.0
Anne Dirkse, Flickr // CC BY-SA 2.0

Our little star and the tiny planets that circle it are part of a galaxy called the Milky Way. Its name comes from the Greek galaxias kyklos ("milky circle") and Latin via lactea ("milky road"). Find a remote area in a national park, miles from the nearest street light, and you'll see exactly why the name makes sense and what all the fuss is about. Above is not a sky of black, but a luminous sea of whites, blues, greens, and tans. Here are a few things you might not know about our spiraling home in the universe.

1. THE MILKY WAY IS GIGANTIC.

The Milky Way galaxy is about 1,000,000,000,000,000,000 kilometers (about 621,371,000,000,000,000 miles) across. Even traveling at the speed of light, it would still take you well over 100,000 years to go from one end of the galaxy to the other. So it's big. Not quite as big as space itself, which is "vastly, hugely, mind-bogglingly big," as Douglas Adams wrote, but respectably large. And that's just one galaxy. Consider how many galaxies there are in the universe: One recent estimate says 2 trillion.

2. IT'S JAM-PACKED WITH CELESTIAL STUFF.

artist's illustration of the milky way galaxy and its center
An artist's concept of the Milky Way and the supermassive black hole Sagittarius A* at its core.
ESA–C. Carreau

The Milky Way is a barred spiral galaxy composed of an estimated 300 billion stars, along with dust, gas, and celestial phenomena such as nebulae, all of which orbits around a hub of sorts called the Galactic Center, with a supermassive black hole called Sagittarius A* (pronounced "A-star") at its core. The bar refers to the characteristic arrangement of stars at the interior of the galaxy, with interstellar gas essentially being channeled inward to feed an interstellar nursery. There are four spiral arms of the galaxy, with the Sun residing on the inner part of a minor arm called Orion. We're located in the boondocks of the Milky Way, but that is OK. There is definitely life here, but everywhere else is a question mark. For all we know, this might be the galactic Paris.

3. FOR A SPIRAL GALAXY, IT'S PRETTY TYPICAL …

If you looked at all the spiral galaxies in the local volume of the universe, the Milky Way wouldn't stand out as being much different than any other. "As galaxies go, the Milky Way is pretty ordinary for its type," Steve Majewski, a professor of astronomy at the University of Virginia and the principal investigator on the Apache Point Observatory Galactic Evolution Experiment (APOGEE), tells Mental Floss. "It's got a pretty regular form. It's got its usual complement of star clusters around it. It's got a supermassive black hole in the center, which most galaxies seem to indicate they have. From that point of view, the Milky Way is a pretty run-of-the-mill spiral galaxy."

4. …AND YET IT STANDS OUT AMONG ALL GALAXIES.

On the other hand, he tells Mental Floss, spiral galaxies in general tend to be larger than most other types of galaxies. "If you did a census of all the galaxies in the universe, the Milky Way would seem rather unusual because it is very big, our type being one of the biggest kinds of galaxies that there are in the universe." From a human perspective, the most important thing about the Milky Way is that it definitely managed to produce life. If they exist, the creatures in Andromeda, the galaxy next door (see #9), probably feel the same way about their own.

5. FIGURING OUT ITS STRUCTURE FROM THE INSIDE IS A CHALLENGE.


John McSporran, Flickr // CC BY 2.0

We have a very close-up view of the phenomena and forces at work in the Milky Way because we live inside of it, but that internal perspective places astronomers at a disadvantage when it comes to determining a galactic pattern. "We have a nice view of the Andromeda galaxy because we can see the whole thing laid out in front of us," Majewski says. "We don't have that opportunity in the Milky Way."

To figure out its structure, astronomers have to think like band members during a football halftime show. Though spectators in the stands can easily see the letters and shapes being made on the field by the marchers, the band can't see the shapes they are making. Rather, they can only work together in some coordinated way, moving to make these patterns and motions on the field. So it is with telescopes and stars.

6. INTERSTELLAR DUST BLOCKS OUR VIEW OF SOME PARTS OF THE GALAXY.

Interstellar dust further stymies astronomers. "That dust blocks our light, our view of the more distant parts of the Milky Way," Majewski says. "There are areas of the galaxy that are relatively obscured from view because they are behind huge columns of dust that we can't see through in the optical wavelengths that our eyes work in." To ameliorate this problem, astronomers sometimes work in longer wavelengths such as radio or infrared, which lessen the effects of the dust.

7. THE MILKY WAY SPINS, BUT ITS SPEED DOESN'T ADD UP …

Astronomers can make pretty reasonable estimates of the mass of the galaxy by the amount of light they can see. They can count the galaxy's stars and calculate how much those stars should weigh. They can account for all the dust in the galaxy and all of the gas. And when they tally the mass of everything they can see, they find that it is far short of what is needed to account for the gravity that causes the Milky Way to spin.

In short, our Sun is about two-thirds of the way from the center of the galaxy, and astronomers know that it goes around the galaxy at about 144 miles per second. "If you calculate it based on the amount of matter interior to the orbit of the Sun, how fast we should be going around, the number you should get is around 150 or 160 kilometers [93–99 miles] per second," Majewski says. "Further out, the stars are rotating even faster than they should if you just account for what we call luminous matter. Clearly there is some other substance in the Milky Way exerting a gravitational effect. We call it dark matter."

8. … AND WE BLAME DARK MATTER FOR THAT.

Dark matter is a big problem in galactic studies. "In the Milky Way, we study it by looking at the orbits of stars and star clusters and satellite galaxies, and then trying to figure out how much mass do we need interior to the orbit of that thing to get it moving at the speed that we can measure," Majewski says. "And so by doing this kind of analysis for objects at different radii across the galaxy, we actually have a fairly good idea of the distribution of the dark matter in the Milky Way—and yet we still have no idea what the dark matter is."

9. THE MILKY WAY IS ON A COLLISION COURSE WITH ANDROMEDA. BUT DON'T PANIC.

andromeda galaxy
The Andromeda galaxy
ESA/Hubble & NASA

Sometime in the next 4 or 5 billion years, the Milky Way and Andromeda galaxies will smash into each other. The two galaxies are about the same size and have about the same number of stars, but there is no cause for alarm. "Even though there are 300 billion stars in our galaxy and a comparable number, or maybe more, in Andromeda, when they collide together, not a single star is expected to hit another star. The space between stars is that vast," Majewski says.

10. WE'RE THROWING EVERYTHING WE HAVE AT STUDYING IT.

There are countless spacecraft and telescopes studying the Milky Way. Most famous is the Hubble Space Telescope, while other space telescopes such as Chandra, Spitzer, and Kepler are also returning data to help astronomers unlock the mysteries of our swirling patch of stars. The next landmark telescope in development is NASA's James Webb Space Telescope. It should finally launch in 2019. Meanwhile, such ambitious projects as APOGEE are working out the structure and evolution of our spiral home by doing "galactic archaeology." APOGEE is a survey of the Milky Way using spectroscopy, measuring the chemical compositions of hundreds of thousands of stars across the galaxy in great detail. The properties of stars around us are fossil evidence of their formation, which, when combined with their ages, helps astronomers understand the timeline and evolution of the galaxy we call home. 

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Space
Now You Can Train to Be an Astronaut on Your Smartphone
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Just because you don't work for NASA doesn't mean you'll never make it as an astronaut. In the world of private space tourism, a little training could be all you need. And there's an app for that.

Space Nation, a Finnish space tourism startup, recently launched Space Nation Navigator, which the company touts as the first astronaut training app in the world. The app aims to train future space travelers using games, quizzes, and fitness challenges that fall into three categories: "body," "mind," and "social."

Each of the challenges is tailored to help you develop the skills you'd need to survive in space—even the mundane ones. One mission is called "Did you clean behind the fridge?" and is designed to highlight the unpleasant chores crew members on the ISS have to do to keep things tidy. There are "survival" quizzes that test your knowledge of how to properly build a fire, read a map, and dispose of your poop in the forest. The app also plugs into your smartphone fitness data so that you can participate in athletic challenges, like a 650-foot sprint designed to train you to escape a meteor impact zone.

Screenshots of the Space Nation Navigator app
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"Space Nation Navigator offers a way for anyone, anywhere to have a 15-minute astronaut experience every day. These astronaut skills—team building, problem solving, positive life hacks—are not just vital to survive in space," Space Nation CEO Kalle Vähä-Jaakkola said in a press statement. "They are also crucial in your daily life."

New challenges are added to your queue every few hours, and you can compete against other users for high scores. If you get enough points, you can become eligible for real-life training experiences with Space Nation, including a trip to Iceland. In 2019, Space Nation plans to hold an international competition to find one astronaut that the program will send to space.

If you're going to start training, we suggest you take some of the tests Project Mercury applicants faced back in 1958 to see how you'd stack up against the first NASA astronauts.

Get it: iOS, Android

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Big Questions
If Earth is Always Moving, Then How Do We See the Same Constellations Every Night?
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Luis Medrano:

6700 mph is nothing in cosmological speeds and distances. Constellations are freakin’ far away.

Get in a car at night and drive on a straight road, then look at the moon. The angle of the moon in respect to your point of view doesn’t change; it seems like the moon is following you wherever you go. Meanwhile, things that are really close to you—like electric poles, roadside buildings, and trees—seem to fly by really fast.

The effect is known as parallax. Things that are close seem to move faster and “travel more distance” (not really) than things that are far away.

In the video above, there are several objects in perspective. The light in the center, which represents the sun, was placed so far away you can barely see it move.

The sun is only eight light-minutes away; that’s 146 million km on average. At human scale it seems like a lot, but in cosmic distances it is nothing. Orion, for example, has stars that are from 243 to 1360 light years away from us. Imagine traveling at the speed of light for 1360 years. That’s how far these stars are. And these are not even the farthest stars. Some stars are Giga-light years away from us.

Now, with the proper precision instruments you can indeed notice the parallax in distant stars, just not with the naked eye. Furthermore, our solar system has moved so much since the early days of astronomy and astrology, the constellations do not correspond to the early astrology maps. The constellations appear shifted.

As a free info nugget: In case your life is ruled by astrology, whatever sign you think you are, you are not.

This post originally appeared on Quora. Click here to view.

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