One of the best tools astronomers have to glimpse the
distant universe is a technology that nature invented. Cosmic magnifying
glasses called gravitational lenses help scientists zoom in on far-away scenes they
could never spot otherwise.
In a recent survey of a section of the universe, researchers
counted 67 new gravitational lenses, leading them to believe there are nearly
half a million similar lenses in the rest of the universe.
"Gravitational lenses amplify the signal," said Peter
Capak, an astronomer at California Institute of Technology who worked on the
study. "It's like a second telescope in front of your telescope. We can
see things that are much fainter than we can normally see."
These natural telescopes are created when massive objects
distort the space-time around them through the strength of their gravitational
pull, causing light to bend as it travels through the warped space.
If a gravitational
lens lies between us and a distant object, then the image of the object we
see can be distorted and magnified.
In the rare case that a gravitational lens is perfectly
aligned between Earth and a distant object, "typically you can get at
least a factor of 10 – 50 magnification," said Jean-Paul Knieb, an astronomer
at Laboratoire d'Astrophysique de Marseille, France, leader of the study.
The effect was predicted
in the 1930s by Einstein's general theory of relativity, and was first observed
in 1979.
The 67 newly discovered lenses are caused by large galaxies,
although clusters of galaxies often produce strong gravitational lenses too.
A team of astronomers used the NASA/ESA Hubble Space
Telescope, along with follow-up observations from the ground, to image a 1.6
square degree field of sky (about nine times the area of the full Moon) in
great detail. The researchers then pored over the images by eye to spot the
tell-tale circular warping signatures of gravitational lenses.
In addition to giving scientists a better idea of how many
gravitational lenses are out there, the discovery will help researchers study
the spread of dark
matter around the galaxies causing the lenses.
"The main thing the gravitational lenses do for us is
they allow us to study the mass distribution in individual galaxies,"
Capak told SPACE.com. "A lot of the mass is contained in dark
matter. We want to understand how the dark matter is distributed."
By analyzing patterns in the warping of space-time caused by
the gravitational lenses, the scientists hope to gain a better understanding of
the structure of galaxies.
"You can think of the lenses as glass beads," Capak
said. "If you hold up a glass bead and look thorough it, it distorts the
picture behind it. The shape of the glass bead is what's causing the different
distortions. The shape of the mass distribution in galaxies is distorting the
background in different ways."
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