Those of you on Facebook may have heard of the “25 Random Things About Me” phenomenon, where you are invited to write, well, 25 random things about yourself for all your friends to read, then invite your friends to do the same. It’s an intriguing literary exercise for sure.
But don’t worry, we’re not going to write 25 random things about ourselves… we’re not that interesting. In the spirit of this recent cultural novelty, we present “25 Random Things About… The Milky Way Galaxy”.
1. In Greek Mythology, the Milky Way was created by milk spilled when Hera, the wife (and sister!) of Zeus, was nursing Hercules.
2. Wherever you live in the world, and whatever the season, if you have dark sky you can step outside on a clear night and see the nearby spiral arms of the Milky Way.
3. The center of the Milky Way is in the direction of Sagittarius, which is low on the horizon for observers in the Northern Hemisphere. But near the equator, or in the Southern Hemisphere, the center of the Milky Way is almost directly overhead… a spectacular sight!
4. Most of us learned the Milky Way is a type of spiral galaxy. But in the past few years, astronomers discovered our galaxy is not just a spiral, but a barred spiral galaxy of type SBbc.
5. The Milky Way has a diameter of 100,000 ly.
6. And it’s about 1000 ly thick.
7. Our solar system lies close to the plane of the Milky Way, which means the Milky Way seems to split the night sky into two equal halves.
8. Aristotle believed the Milky Way was caused by burning stars in the upper atmosphere. While he was a fine philosopher, many of Aristotle’s scientific conjectures were way off.
9. There are about 300 billion stars in our galaxy.
10. The Sun lies about 26,000 ly from the center of the Milky Way.
11. The Sun rotates once around the Milky Way every 220 million years. Our solar system (and therefore the Earth) revolves about the galactic center at 220 km/s. At this speed, our solar system travels in the direction of the star Vega at a rate of one light-year every 1400 years.
12. The oldest stars in the Milky Way lie near the centre of the galaxy and in a halo about the centre, which consists of globular clusters and lone ancient stars.
13. Along the spiral arms, away from the galactic center, interstellar clouds collapse under the force of gravity into tight fists of gas and dust that ignite into fresh new clusters of stars.
14. As you read this, the Milky Way is colliding with an obscure dwarf galaxy named the Virgo stellar stream.
15. At the center of the Milky Way lies a gigantic black hole with a mass of 4 million suns that is violently gobbling stars and matter and sending out highly energetic X-rays. But the Earth is in no danger of colliding with this black hole… so don’t worry.
16. Our solar system lies along the inner rim of the Orion Arm of our galaxy. The next arm closer to the center is the Carina-Sagittarius arm, and the next arm farther away from the solar system is the Perseus arm.
17. The name for the Milky Way in China, Japan, and other East Asian cultures, is “Silver River” (a much more accurate name, don’t you think?).
18. The north and south Galactic poles, which point 90 degrees away from the dusty galactic plane, lie in the constellations Coma Berenices and Sculptor, respectively. When you look in the sky towards the poles and away from the galactic plane, you can see into deep intergalactic space where lies millions more galaxies of all shapes and sizes.
19. Galileo was the first to discover the Milky Way is made of stars.
20. The Milky Way and Andromeda galaxy are the largest in what’s known as the Local Group of galaxies. In the Local Group, there are many tiny dwarf galaxies, the largest of which are the Large and Small Magellanic Clouds. The Local Group of galaxies is itself part of a much larger cluster of galaxies called the Virgo Supercluster.
21. The Andromeda Galaxy approaches our Milky Way at 100 km/s, and the two giant galaxies will collide in roughly 2 billion years. The stars in each galaxy won’t collide, but the two galaxies will merge into a featureless elliptical galaxy and lose their beautiful spiral shape and the dust and gas that form new stars.
22. From Thoreau, a beautiful quote to console you when you’re alone with your telescope, wondering if anyone will ever understand why you love the stars so much: “Why should I feel lonely: Is not our planet in the Milky Way?”
23. Most of the mass of the Milky Way is believed to consist of mysterious “dark matter”, the nature of which is still unknown.
24. The oldest star in the Milky Way, called HE 1523-0901 in Libra, is some 13.2 billion years old, almost as old as the universe itself.
25. Because of the effects of light pollution, most children in the world will never see the Milky Way.