Unknown Force Kicks Stars Out of Milky Way

Unknown Force Kicks Stars Out of Milky Way. Really. (TIME, Jan 10, 2014):

If you could see it from the outside, the Milky Way would look like a majestic spiral of stars and glowing gas, rotating on its axis once every 200 million years or so like a gigantic, pinwheel 100,000 light-years across. Up close, though, you’d see that each star is jostling along on its own, moving through an entirely independent orbit. It’s more like an unruly crowd, going in the same approximate direction at the same approximate speed, than a military formation marching in lockstep.

At least a few stars, however, are headed somewhere else entirely, and in a big hurry. They’re known as hypervelocity stars, and they’re going so fast that they’re on their way out of the Milky Way altogether. While the astronomers think they have an explanation for the 18 hypervelocity stars discovered since 2005, a new group of 20, just announced at a meeting of the American Astronomical Society outside of Washington, DC, seems to make no sense at all.

“What’s going on?” asks Vanderbilt University grad student Lauren Palladino, lead author of a paper in the Astrophysical Journal describing these cosmic speedsters. “We don’t know.”

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NASA’s Hubble: Milky Way Destined For Head-On Collision With Andromeda Galaxy

NASA’s Hubble Shows Milky Way is Destined for Head-on Collision with Andromeda Galaxy (HubbleSite, May 31, 2012):

The three largest galaxies in our Local Group of Galaxies are our Milky Way along with the Andromeda (also known as Messier 31) and Triangulum (also known as Messier 33) galaxies. This scientific visualization of a computer simulation depicts their joint evolution over the next several billion years and features the inevitable massive collision between the Milky Way and Andromeda. Hubble Space Telescope observations indicate that the two galaxies, pulled together by their mutual gravity, will crash together in a head-on collision about 4 billion years from now. The thin disk shapes of these spiral galaxies are strongly distorted and irrevocably transformed by the encounter. Around 6 billion years from now, the two galaxies will merge to form a single elliptical galaxy. The Triangulum galaxy continues to orbit the merged pair through the end of this computer simulation, though other computer models show it becoming part of the collision.

The visualization covers 8.2 billion years into the future at 105 million years per second. Colors are representative: light blue for spiral galaxies (considered “blue” in astronomy parlance because of their active star formation) and orange-yellow for elliptical galaxies (called “red” by astronomers for their old stellar populations). A random background field of galaxies has been added to the simulation in order to indicate the camera motion through the simulation volume.

Study: Hundred Billion Planets In The Milky Way, With 17 Billion Of Them The Size Of Earth!

Our Galaxy Is Crammed Full of Planets (Slate, Jan 7, 2013):

One of the most exciting fields in astronomy—really, in all of science—is the search for alien worlds. The first planet around another star was found in 1992 (though the star was the remnant of a supernova, so not terribly Sun-like), and the first planet around a Sun-like star just three years later. Fast forward two decades, and we now know of hundreds of such planets, and have thousands more detected that have to be confirmed (the data look good, but we still call them candidates until confirmation).

In fact, there are enough that the field of exoplanets is in the next step of the scientific process past discovery: categorization. We have enough known planets orbiting other stars that we can start to plop different labels on them: massive, big, small, orbiting hot stars, orbiting cool ones, having tight orbits or wide-sweeping ones. And once you can do that some very, very interesting things start to fall in place.

For example, you can use some statistics to extrapolate how many planets there must be in our galaxy. A new study has done just that, and the number they get is stunning: they calculate there may be a hundred billion planets in the Milky Way, with 17 billion of them the size of Earth!