A new giant virtual
telescope is the most powerful tool scientists have ever had to study the
universe in a part of the electromagnetic spectrum called long wavelength
submillimeter light.
The Extended
Submillimeter Array (eSMA) was created by combining three telescopes in Hawaii using computer software. By routing them together in a process called interferometry,
the combined telescopes have the virtual resolution of one huge
telescope the size of the distance between them. In this case, the virtual
telescope has a diameter of 782 meters, or about half a mile.
The eSMA is made up of
the SubMillimeter
Array, which contains eight dishes with 6-meter diameters, as well as the
15-meter James Clerk Maxwell Telescope and the 10-meter Caltech Submillimeter
Observatory, all on the summit of Mauna Kea on the Big Island of Hawaii. All
the dishes are linked via fiber optic cable to form an enormous virtual
telescope akin to the sum of its parts.
"It would be
impossible to build a telescope this large, so we take several smaller
telescopes," said Sandrine Bottinelli of France's Center for the Study of
Radiation in Space. "The radiation is collected by each antenna and then
combined by computer software. That allows us to simulate a signal that would
be equivalent to what we would get with a single large telescope."
For now, eSMA is the
most powerful submillimeter
observatory on the planet.
Interferometry is
commonly used to string together radio telescopes. Making a submillimeter
interferometer is a bit trickier because of the weather conditions required for
submillimeter astronomy. The water vapor in the Earth's atmosphere blocks
submillimeter radiation in most locations.
"It's more
difficult to find a site," Bottinelli told SPACE.com. "You
need a generally dry and stable atmosphere, so it must be high altitude."
Mauna Kea's lofty location at 14,000 ft (4,000
meters) is perfect.
Scanning the universe
through submillimeter light allows astronomers to peer deep into the dusty
regions in which new stars, planets and even whole galaxies are being born.
These clouds of gas and tiny dust particles are completely dark in visible
light, because optical wavelength light is absorbed by the gas and dust. But
submillimeter waves, which are longer than optical light waves, can penetrate
this material.
Recently Bottinelli
led one of the first observations made with the newly-built eSMA. She pointed
the scope at a bright radio source located behind a foreground spiral galaxy,
which is so far away its light left when the universe was only 20 percent of
its current age. The foreground galaxy acts like a lens, bending the light from
the radio source and focusing it toward Earth. Since the bright object's light
traveled through the galaxy on its way here, it revealed clues about the
interstellar gas in the spiral, including the presence of atomic
carbon there. Atomic carbon is significant because it plays an important
role in building more complex organic molecules.
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