University of Wisconsin–Madison

Tag: space & astronomy

Curiosities: Why is Pluto not considered a planet?

Until 2006, astronomers had not carefully defined “planet,” says James Lattis, director of the UW Space Place. Asteroids were not considered planets because they are too small and numerous. Likewise, comets were not considered planets because they are too small and have noncircular orbits that go far outside the plane of the solar system (location …

Curiosities: Why do stars appear to twinkle in the night sky?

Courtesy European Space Agency (ESA/Hubble). Stars twinkle because we view them through our atmosphere, says James Lattis, director of University of Wisconsin-Madison Space Place.  “Seen from the moon, where there is no atmosphere, stars do not twinkle at all, but here on Earth starlight passes through many miles of air on its way to our …

Curiosities: How many galaxies have humans discovered?

“We don’t know,” says Ed Churchwell, professor of astronomy. “We know it’s a very large number.” It’s in the hundreds of billions, Churchwell says. In contrast, there are but 4 billion stars in our own galaxy, the Milky Way — and the number will keep growing for some time before we run out of galaxies …