Going Deep with the Hubble Space Telescope

The Hubble Space Telescope enables us to see intricate and colorful photos from outer space that are otherwise invisible to the naked eye. However, the future of this space mission is uncertain.

Published August 1, 2004

By Robert Irion
Academy Contributor

During its 14 years in orbit, the Hubble Space Telescope has unveiled some memorable images of the heavens. But one of its latest pictures, released earlier this year to international fanfare, may become the telescope’s enduring legacy.

Called the Hubble Ultra Deep Field (UDF), the photograph is the most sensitive view of the distant universe ever taken. It reveals thousands of galaxies spread throughout a tiny patch of the sky, arrayed like gems against the black velvet of space. The photo, which took nearly 300 hours to produce, is sharp even by Hubble’s standards. “It’s a magnificent, beautiful, stunning image,” says astrophysicist Michael Shara of the American Museum of Natural History (AMNH) in New York.

Indeed, the UDF is so scientifically rich that Shara and other astronomers in the area decided to share their research efforts with thousands of people. For six days in March, researchers and students from AMNH, Columbia University, and Stony Brook University pored over the image in front of fascinated onlookers beneath the white sphere of the Hayden Planetarium. The teams worked at banks of computers, fielded questions, and even produced a daily video that aired on a giant screen in Times Square.

“This was a unique opportunity to share the excitement of scientific research with the general public,” says organizer Kenneth Lanzetta, an astronomer at Stony Brook.

How Galaxies Change and Grow

Hubble’s leaders conceived of the UDF as a way to improve upon the original Hubble Deep Field, a 10-day-long photographic exposure of thousands of remote galaxies. That 1995 image and a 1998 follow-up opened startling windows into the depths of the universe, where galaxies were a fraction of their current age. The two Deep Fields launched a new era of research into how galaxies change and grow over time. But the images also tantalized astronomers with hints of the true original building blocks of modern galaxies, which lay beyond Hubble’s grasp in the 1990s.

Now, the telescope can detect those objects thanks to a powerful new tool: the Advanced Camera for Surveys. Astronauts installed the camera in 2002 during the space shuttle’s last service call to Hubble. It gives the telescope a crisper focus for photography and a wider field of view. The patch of sky captured in the UDF is still small by the standards of the human eye – just 1/67th the size of the full moon – but it’s big enough to display about 10,000 galaxies of all shapes and sizes, with unsurpassed clarity. “The quality of the data is better than anything we’ve ever done with Hubble,” says Steven Beckwith, director of the Space Telescope Science Institute in Baltimore, Maryland.

The new camera is sensitive to near-infrared light, just past the reddest wavelengths of light that our eyes perceive. As the entire universe expands, light shining from distant galaxies stretches into redder and redder light. For extremely remote objects, most of the optical light shifts into infrared radiation, which we know as “heat.” Hubble’s new camera, along with a revitalized instrument that detects infrared light exclusively, endowed the telescope with the vision it needed to see galaxies near the fringes of the observable universe.

The Universe: 13.7 Billion Years Old

Hundreds of galaxies in the UDF shine most brightly in the infrared, including some faint objects that may have existed just 800 million years after the Big Bang. Astronomers believe the universe is about 13.7 billion years old today. Seeing such distant galaxies is like looking at pictures from the childhood album of a 50-year-old adult – all the way back to age 3.

Astronomers who are trying to devise a coherent picture of how galaxies assembled will focus most intently on the faint red objects in the UDF. Even a glance at the image reveals that these galaxies look nothing like the gorgeous spirals and other large metropolises of stars we see today. “The objects really are quite irregular,” says Beckwith. “We’re clearly seeing back to a time when the universe was chaotic. We see a variety of unusual shapes that we can’t identify right now.”

These blotches were scrutinized by the Stony Brook team at the AMNH public event. Prior to the release of the UDF, Lanzetta expected the image might reveal galaxies shining a mere 500 million years after the Big Bang. However, after six days of working nearly round the clock to analyze the light from a whopping 8,172 galaxies, the team determined that none of them was quite so far away. Still, knowing the distances to that many objects – and studying their shapes – will help astronomers figure out how galaxy collisions and waves of star-birth transformed ragged shreds of stars into the grand galaxies of today.

Distant Object Detected

The Columbia researchers, led by astronomer Arlin Crotts, scoured the UDF for changing flares of light. The Hubble team assembled the photograph from a series of shorter exposures over a four-month period. If any star in a distant galaxy exploded as a supernova during that time, it might appear as a brighter pinprick of light in some of the exposures. Crotts anticipated that his group might see a half-dozen such flares, but they found none – an outcome that came as a mild surprise.

Meanwhile, Shara and his AMNH colleagues examined the images for evidence of moving objects. Specifically, the team searched for nearby stars that move quickly through space – so quickly that their motion would show up during the four months of UDF exposures. Such stars would have to be close to our sun – perhaps within 10 or 20 lightyears – but so faint that previous surveys had not detected them. After six days of intense hunting, says Shara, “We have exactly one candidate. Talk about a needle in a haystack!” The team hopes to confirm the object – and learn its nature – with further research, including another view by Hubble within a year.

The combined results of the three teams didn’t make any headlines – and that was just fine, the participants agreed. This raw process was in full view at AMNH, and the scientists could not have been more pleased.

“The single most important reason was to demystify, insofar as we could, astronomical research,” Shara says. “Most of the public still has this view of astronomers as old pipe-smoking men sitting at a telescope on a dark night and peering through the eyepiece. We wanted to show that astronomy is done by living, breathing people, many of them quite young, almost half of them female, and we don’t know the answers.”

Working to Save Hubble

One particular issue rang out during the public discussions, Crotts notes: “Saving Hubble was one of the major issues on people’s minds.” Most visitors were aware that in January, NASA announced it would no longer fly the space shuttle to maintain and upgrade the telescope. Without another such mission, Hubble probably will expire by 2006 or 2007 – several years earlier than astronomers had planned. Although NASA administrator Sean O’Keefe insists that the decision is based on the safety of the astronauts, scientists and science lovers have reacted strongly and negatively.

Regardless of Hubble’s fate, the UDF image will persist as one of the telescope’s profound contributions to science. And in New York, thousands of people watched as astronomers labored to comprehend our cosmic ancestry – encoded within swirls of light on their glowing computer screens.

Also read: Robin Kerrod and the Romance of Astronomy