Image: Lensing effect
A. Feild / STScI / NASA / ESA
This diagram illustrates how gravitational lensing by foreground galaxies will influence the appearance of far more distant background galaxies. This means that as many as 20 percent of the most distant galaxies currently detected will appear brighter because their light is being amplified by the effects of foreground intense gravitational fields.
updated 1/13/2011 12:00:34 AM ET 2011-01-13T05:00:34

Cosmic lenses created by the ultra-strong gravity of some objects in space may spoil upcoming estimates of the number of galaxies during the universe's earliest days by as much as a factor of 10, a new study warns.

A great deal of mystery surrounds the days when stars were first born. To learn more about the first galaxies that formed, astronomers focus on the farthest ones they can see. If light from a galaxy took a long time coming to Earth, the galaxy must be very old as well as very distant.

After all, the universe is estimated to be 13.7 billion years old.

The problem that researchers now face has to do with the way gravity warps space-time. The greater the mass of an object in space, the stronger its gravitational pull. This in turn can bend light around it, affecting the view by telescopes on Earth.

Blame it on gravity
Scientists call this cosmic effect "gravitational lensing." When it is caused by galaxies that lie on the way toward the ancient ones scientists want to study, it can lead to distorted views of the targets' light.

The probability of gravitational lensing distorting measurements of distant galaxies had been estimated at just 0.5 percent.

However, the study found that astronomers failed to account for "magnification bias," which can make a galaxy appear brighter than it is.  

"Gravitational lensing is magnifying all galaxies lying behind a gravitational lens, and this happens much more often for the most distant galaxies," said the study's lead author, Stuart Wyithe, an astronomer at the University of Melbourne in Australia.

Galaxy-magnifying distortions
When astronomers search for galaxies in a certain patch of space, they don't want their images to be flooded with unnecessary light, so their telescope limits the brightness that can be detected (making some galaxies too faint to be observed). However, because gravitational lensing magnifies the light from galaxies relative to their intrinsic brightness, intrinsically faint galaxies start popping up in the results.

"Since faint galaxies are much more common than bright galaxies, the number of sources observed behind gravitational lenses is significantly enhanced," Wyithe told

At very large distances, magnification bias can increase the number of gravitationally lensed galaxies detected by as much as a factor of 10, according to Wyithe and his colleagues.

The implication is that our view of the most distant galaxies through the Hubble Space Telescope "might be distorted significantly by gravitational lensing, a kind of cosmic hall of mirrors," Wyithe said.

Better telescopes needed
The next-generation James Webb Space Telescope will be required to properly investigate the lensing phenomenon. By looking for redshift — the distortion in light from an object as it moves away from an observer — one might be able to overcome this magnification bias "and measure an unbiased census of early galaxies," Wyithe said.

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Knowing how many galaxies existed in the early universe is key to investigating enigmas such the so-called "reionization" of the early universe. This critical, but not yet fully understood, event occurred when the atomic hydrogen that once pervaded the universe was ionized into its constituent protons and electrons, increasing the temperature of the universe to some 18,000 degrees Fahrenheit (10,000 degrees Celsius).

Studies of the most distant, ancient galaxies suggest they did not put out enough radiation to reionize the early universe.

"This reionization occurred between about 400 million and 900 million years after the Big Bang, but astronomers still don't know which sources of light caused it to happen," Wyithe said. The new galaxy candidates now being seen in the Hubble Ultra Deep Field come from right in this important epoch in the evolution of the universe, and could thus help solve the mystery.

The scientists detail their findings in Thursday's issue of the journal Nature.

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Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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