Articles on Galaxies

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The universe is home to a dizzying number of stars and planets. But the vast bulk of the universe is thought to be invisible dark matter. Illustris Collaboration

Why do astronomers believe in dark matter?

Why do astronomers believe there's dark matter when it cannot be directly detected? Let's look at the evidence, and see what dark matter's presence means for our universe.
An artist’s impression of Kepler-22b, a planet known to comfortably circle in the habitable zone of a sun-like star. It is the first planet that NASA’s Kepler mission has confirmed to orbit in a star’s habitable zone - the region around a star where liquid water, a requirement for life on Earth, could persist. NASA/Ames/JPL-Caltech

Curious Kids: why has nobody found any life outside of Earth?

Life could exist in another solar system in a different part our galaxy. Or in another galaxy far away. We don't have the perfect technology yet to study such far away places but we're still trying.
Nobody knows for sure - but it’s possible. Shutterstock

Curious Kids: Are there living things on different galaxies?

There are probably more than a million planets in the universe for every single grain of sand on Earth. That's a lot of planets. My guess is that there probably is life elsewhere in the Universe.
The other galaxies are there, but they are hiding a very long way away. www.shutterstock.com

Curious Kids: Where are all the other galaxies hidden?

We are in the Milky Way. If you travelled on an extremely fast spaceship for more than two million years, you would reach our neighbour, the Andromeda galaxy. All other galaxies are even further away.
An artist’s impression of the predicted merger between our Milky Way (right) and the neighboring Andromeda galaxy (left). So which galaxy will dominate? NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger

When galaxies collide, size matters if you want to know the fate of our Milky Way

Bigger galaxies tend to dominate the smaller, when the two collide. But the pending battle between our Milky Way and the Andromeda galaxy might be a much fairer fight than we previously thought.

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