The Johns Hopkins Gazette: May 6, 2002
May 6, 2002
VOL. 31, NO. 33


Hubba-Hubble! Images from ACS Surpass Expectations

By Michael Purdy
Johns Hopkins Gazette Online Edition

Elated astronomers from Johns Hopkins, the Space Telescope Science Institute and NASA recently unveiled the first images taken by the Advanced Camera for Surveys, a new instrument installed in the orbiting Hubble Space Telescope in March.

The new pictures contain beautiful vistas that include nebulas awash in glowing gas and dust, and galaxies colliding or merging on panoramic backdrops of more distant galaxies and proto-galaxies.

Scientists named this galaxy the Tadpole Galaxy for the long tail of stars and gas trailing behind it, which resulted from a collision with another galaxy. The galaxy is located about 420 million light-years from Earth in the constellation Draco.

"These are among the best images of the distant universe that humans have ever seen," said Holland Ford, astronomy professor in the Krieger School of Arts and Sciences and leader of the team that built the new camera.

"My colleagues and I were stunned," Ford reported at a NASA press conference on April 30. "We had underestimated just how extraordinary these images would be."

Astronomers singled out for particular attention an image of a galaxy they named the Tadpole Galaxy. Thanks to a collision with another, smaller galaxy, the Tadpole Galaxy has a tail of stars, gas and dust trailing out behind it for nearly 280,000 light-years.

That's only half the wonder of the photograph, though. In the background, astronomers believe they can see about 3,000 other distant galaxies, or about twice the number of galaxies detected in Hubble's two prior images of the very distant universe.

Faint red galaxies just barely discernible behind the Tadpole Galaxy may be among the earliest ever detected. Given the tremendous distances light has to travel, looking out into the universe entails looking back in time, and Ford said that some of the faint red galaxies in the image appear to date back to as little as 1 billion years after the universe was formed. Astronomers estimate the universe is now 13.5 billion years old.

"ACS will allow us to push back the frontier of the early universe. We will be able to enter the 'twilight zone' period when galaxies were just beginning to form out of the blackness following the cooling of the universe from the big bang," Ford said of the prospects for the new camera.

The new image including distant galaxies was taken in a fraction of the time previously required, thanks to the state-of-the-art detectors and design included in the ACS, which has much greater resolution, field of view and sensitivity than prior cameras.

Ford and other astronomers have many other ideas for projects that they're eager to put the ACS to use on. These include attempting to obtain the first direct images of planets in other nearby solar systems; taking a closer, more detailed look at the weather on planets in our solar system; and verifying the celestial yardstick astronomers have used for several decades to gauge distances around the universe.

To view all four of the recently released first images, go to