Category Archives: evolution of galaxies

What Do You See Here?

A Sky Full of Galaxies, and What Else?

The farther out from Earth you look into space, the more galaxies you see. As you let your eyes roam around this recently released Hubble Space Telescope image, notice how many galaxies you see. Not sure what’s a galaxy? Look for things that are kind of cigar-shaped, or with spiral shapes. Some galaxies in this image may look blobby or irregular. There are hundreds of them in this image.

The objects with crosshairs on them? Those are stars that lie fairly close to us. The blue cloud of light off to the bottom left? That’s why this picture was taken. It’s a portion of a galaxy called that is being disrupted by an encounter with another galaxy. The two together are called NGC 4038 and NGC 4039, and nicknamed the Antennae. They lie about 45 million light-years away from us (and all those other galaxies lie at least that far away, or more). As they merge together, the gravitational influences of the two are warping them, and sending out two tails of gas. The blue color comes from the new stars that are being born under the influence of this galactic commingling. Star formation is a major “effect” of galaxy collisions, and contributes to the long-term evolution of galaxies and the stars they contain.

(Images Credit:NASA, ESA & Ivo Saviane (European Southern Observatory)/Robert Gendler)

Galaxies Can’t Do that, Can They?

It Turns Out They Do… All Over the Place

Back before astronomers had high-resolution cameras and spectrographs and orbiting spacecraft to look at the distant universe, interacting galaxies were just plain weird. They didn’t fit into the standard scheme of galaxies as set out by the venerable giant of astronomy, Edwin Hubble. Every astronomer worth his (and sometimes a few “her”) salt memorized the Hubble tuning fork diagram and tried to fit every galaxy observed somewhere in this hierarchy.

Trouble is, not all galaxies “played the game.” Some of them looked downright pathological, twisted up, or misshapen or something. But the problem was that until we could look at these galactic weirdos with good optics and high-resolution spectrographs, astronomers couldn’t really tell what was going on with many of them.

That’s why the monumental set of galaxies that Hubble Space Telescope and other high-resolution ground-based observatories have observed over the years is such a great achievement. For the first time, astronomers can see what’s happening. And, they’re finding galaxy interactions (collisions, if you will) all over the place. The fact that we’re seeing them nearly everywhere we point a telescope to tells us that collisions aren’t just oddball occurrences in the universe. They’re part of an evolutionary process that shapes galaxies and triggers star formation in the process.

Our own Milky Way is actually cannibalizing smaller galaxies as you read this. The Sloan Digital Sky Survey is tracing out the streams of stars that are pouring into our galaxy as these smaller galaxies interact with the Milky Way. Here’s what it looks like from our vantage point inside the Milky Way.

Galaxy interaction is a hot topic in astronomy these days as the folks researching these cosmically titanic events dig into the details. Stay tuned!