

Hubble Reveals Universe's Oldest Galaxies

The new Frontier Fields images show 13-billion-year-old stars.

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Galaxy cluster Abell 2744 is the deepest image ever made of any cluster galaxy.

Hubble Space Telescope astronomers Tuesday released views of the oldest galaxies yet seen, about 13.2 billion years old. They offer intriguing glimpses of the chaotic birth of the first stars.

The images are the first in a series called Frontier Fields.

Explaining the earliest stars would answer astronomers' questions about how galaxies such as our own Milky Way arose and how stars such as our sun came to reside within a galaxy.

The universe is about 13.7 billion years old. Since 1995, the Hubble Space Telescope has provided astronomers with glimpses of galaxies ever closer in age to the early days of the cosmos. Hubble started with a Deep Field image produced by focusing toward the Big Dipper for 43 hours, uncovering galaxies more than 12 billion years old.

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A parallel field image of galaxy cluster Abell 2744.

The latest images, presented at the American Astronomical Society meeting in Washington, D.C., show galaxies some 500 million years more ancient than those once groundbreaking images.

First Frontier

At this early time, galaxies were "bright blue blobs, closer [together], smaller—and they're everywhere," says astronomer Garth Illingworth of the University of California, Santa Cruz, who presented a look at four surprisingly bright galaxies from this early era, seen by both Hubble and NASA's Spitzer Space Telescope.

While these early galaxies weighed only about one percent as much as the Milky Way, they likely produced stars about 50 times more frequently than our galaxy does now.

"It's very important to understand how these earliest galaxies formed to understand our own galaxy today," says astronomer Eilat Glikman of Vermont's Middlebury College.

Gravitational Lens

As Einstein showed a century ago, gravity bends light. The Hubble First Frontier images rely on the gravity of a closer, tightly packed group of several hundred galaxies, called Abell 2744, to bend the light from more distant and ancient galaxies.

The bending effect focuses the light from the ancient galaxies, making them appear 10 to 20 times larger than they would otherwise appear. This gravitational lens allows Hubble to see the more distant ancient galaxies.

"There's an enormous amount of science that will come out of the Frontier Fields," says astronomer Michael West of the Maria Mitchell Observatory, who was not part of the discovery team. "Many astronomers are eagerly waiting to get their hands on the data!"

Unfortunately, the gravitational lens effect also distorts the ancient galaxies like a "fun house mirror," West says. "Imagine you could only see someone's distorted face in a circus fun house mirror and had to draw a picture of what that person really looks like without being able to see them directly."

Fortunately, astronomers can estimate the amount of distortion produced by the gravitational lensing and reconstruct an image of the distant galaxies and their properties.

For now, the picture painted by these images is one of an early universe where star production ramped up and galaxies grew larger and larger over the first four billion years of the universe.

When it comes to seeing early stars, Glikman says, "we have to be careful the tip of the iceberg really looks like the base of the iceberg." But these early galaxies "are really good indicators of what was going on early in the universe."

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