The Universe Held a Party, and We Missed It

It’s too bad. Life evolved here on Earth after the Universe’s big parties already ended. Sure, there’s the occasional galaxy merger, and we’ve got a few regions of furious star formation here in the Milky Way. But billions of years ago, galaxies were banging and crashing together, leading to vast eras of star formation. In fact, in the first 25% of the Universe’s history more than half of the galaxies were in the midst of one of these cosmic collisions.

This was the research unveiled by University of Texas at Austin researcher Shardha Jogee. She and her team surveyed a region of space approximately the size of the Moon using the Hubble Space Telescope. Within this region, they found thousands of bright galaxies in the process of merging with one another.

Kyle Penner, from the University of Texas at Austin explained how they saw the mergers, “with Hubble’s spectacular resolution, we could discern amazing tell-tale clues of the mergers and interactions – huge tails, warps, ripples, double nuclei – in galaxies billions of light-years away.”

They used ground-based observatories to determine the galaxies age, and then analyzed these galaxies using the Spitzer Space Telescope to track the rate of star formation in each galaxy. Normally hidden in visible light, the stellar nurseries are revealed in Spitzer’s infrared view which can peer right through the obsuring gas and dust.

If you take two nice neat spiral galaxies and smash them together, you get a mess. The galaxies are torn apart, tidal tails of stars are flung out in all directions. The stars “forget” their original orbits and circle the central point of gravity in all directions. Two beautiful spirals become an elliptical galaxy.

They found that when the Universe was only 2.1 billion years, over 40% of massive galaxies were strongly interacting and merging. And then, over each billion-year interval, only 10% of galaxies are involved in strong interactions and mergers. During these periods, the galactic interactions collapsed vast clouds of gas, creating periods of star formation.

The researchers turned up a few surprises. They found that all this galactic interaction actually only increased the rates of star formation in the host galaxies by a mere factor of 2 or 3. They also turned up a large number of “bulgeless” galaxies. These should be very rare, size a past major merger in the life of a galaxy always builds a bulge.

Just imagine what the Universe would have looked like 7 billion years ago; every where you looked galaxies would have been crashing together, spraying stars in all directions. Galaxies would have blazed with regions of active star formation.

It must have been quite the party.

Original Source: University of Texas at Austin News Release

4 Replies to “The Universe Held a Party, and We Missed It”

  1. So I wonder if after the initial 25% of the universe’s age there is a propensity for eliiptical galaxies? And also, does the galaxy density drop off? For simplicity sake if we assume the universe is 14 billion years old is the density of galaxies over 10.5 billion light years higher than what is closer? And from ~10.5 billion light years to something much closer is there a population spike for ellipticals? Does this also imply ellipticals eventually “sort themselves out” again into spirals?

  2. We’re not missing anything. From what I understand, we are in the midst of a galactic merger right now.

  3. Peculiar galaxies and interacting pairs tend to be really far away, which suggests that all this chaos happened a long time ago. Who knows, the Tadpole Galaxy might be more like a regular spiral galaxy at this very moment!

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