A Telescope as Big as Earth

Astronomers have created an Earth-sized virtual radio telescope that can
detect features 3,000 times smaller than the Hubble Space Telescope can see.

The virtual device, which was created by linking signals from radio
telescopes on several continents, is the first to operate at shortest-ever
(2 millimeter) radio wavelengths.

The international collaboration involves two telescopes in Arizona — the
Heinrich Hertz Submillimeter Telescope (HHT)on Mount Graham and the Kitt
Peak 12-meter Telescope — and telescopes in Spain, Finland, and Chile.

“Both the distance between partner telescopes and the ability to detect
shorter wavelength, higher frequency radio emission gives this telescope its
unprecedented power,” said Lucy Ziurys, director of the Arizona Radio
Observatory, part of the University of Arizona’s Steward Observatory in
Tucson.

Astronomers define telescope power is terms of angular resolution — the
ability to clearly separate two closely spaced objects in the sky. At its
record-breaking best, the new telescope resolved an angle of 50 micro arc
seconds, or about one hundred millionth of a degree of the sky.

“The resolution achieved by this telescope is the equivalent of sitting in
New York and being able to see the dimples on a golf ball in Los Angeles,”
said Sheperd Doeleman of the Massachusetts Institute of Technology’s
Haystack Observatory.

Ziurys, Doeleman, Thomas Krichbaum of the Max-Planck-Institute for Radio
Astronomy in Bonn, Germany, and Albert Greve of the Institut de
Radioastronomie Millemetrique (IRAM), which operates telescopes in Granada,
Spain, and Grenoble, France, are principal collaborators on the project.
Finland’s Metsahovi Radio Observatory, the European Southern Observatory’s
Swedish-operated SEST telescope, and the National Radio Astronomy
Observatory are also involved. The National Science Foundation and the
Tucson-based Research Corporation help fund the U.S. effort.

The world’s most powerful radio telescope began to materialize late last
year, when Greve, Ziurys, and Doeleman agreed to attempt 2mm-wavelength
observations using Kitt Peak’s 12-meter telescope and Mount Graham’s HHT as
the U.S. component of the international telescope array.

“At that time, we didn’t have the capability to do 2mm observations at the
HHT,” Ziurys said. “We could build the devices, but we weren’t sure we could
do it by April, when the observing was scheduled for MIT.”

But thanks to Arizona Radio Observatory chief engineer Henry Fagg, the HHT
had its 2mm detector by April.

The astronomers first linked the two Arizona telescopes, which are separated
by 100 miles, in 2mm radio observations, Ziurys said. They then tackled the
bigger challenge of linking the U.S. telescopes to Europe. The two Arizona
telescopes and one in Spain provided key long distance detections that were
especially critical to the project.

The telescope has successfully picked up radio signals from galaxies more
than 3 billion light years away. It will be used to study one of the
fundamental mysteries of modern astronomy — how so-called “active” galaxies
produce their incredible energetic output.

Normally, galaxies emit as much energy as the sum of their stars. “Active”
galaxies emit far more energy than the sum of their stars. The excess energy
is concentrated at the galaxy’s core. Astronomers believe that super massive
black holes, billions of times bigger than the sun, power these energetic
cores. Some of the cores spew powerful streams of high-speed particles
millions of light years beyond their host galaxies. But how these high-speed
particle jets are launched from galactic cores is not clear. The new
telescope is specifically designed to make detailed images of where the jets
erupt.

The technique of using several telescopes on different continents to
simultaneously record radio emissions from the same object is called Very
Long Baseline Interferometry (VLBI). Signals from each telescope are
time-stamped with extremely accurate atomic clocks, recorded on magnetic
tapes, then combined in a special-purpose supercomputer. The technique forms
a virtual radio telescope that can be as large as the diameter of Earth.

Future plans are to direct the powerful new telescope at the core of the
Milky Way Galaxy to detect structures close to our galaxy’s suspected black
hole.

“We weren’t sure we could get it to work last spring, but clearly these
current results represent just the tip of the iceberg,” Ziurys said. “We are
very excited about future science using this powerful technique.”