Distant galaxy helped tidy up early universe, scientists say

In overcoming the faintness issue, Zheng and his colleagues had a strong ally in Albert Einstein. Among the well-validated predictions of Einstein's theory of general relativity: Intense gravity can bend light. And it can magnify light in a process known as gravitational lensing.

The galaxy Zheng's team observed lay behind a galaxy cluster tipping the cosmic scales at 2 million billion solar masses – making it one of the most powerful gravitational lenses known. The lensing effect brightened the early galaxy's light substantially, making it possible to gather enough data to estimate the galaxy's size – tiny enough that it could get lost in the disk of the Milky Way – as well as its mass and the relative abundance of younger and older stars.

The data were gathered by the Hubble Space Telescope, as part of a long-term project to use galaxy clusters and gravitational lensing to test theories about the nature of dark energy. In addition, the team used the Spitzer Space Telescope. Hubble can capture images at wavelengths ranging from ultraviolet at the high end to near-infrared at the low end. Spitzer can detect objects via light well into the infrared range.

The ability to detect light at longer, infrared wavelengths is critical for detecting objects at such distances. The universe is expanding at an increasing pace, and astronomers long ago established that the farther away an object is, the faster it is receding. This phenomenon in effect stretches light from a distant object to longer, redder wavelengths, a feature astronomers have dubbed red shift.

In its immediate neighborhood, the newly discovered galaxy would shine most brightly in the ultraviolet. By the time that light reached Earth, the universe's expansion has stretched the light into infrared or near-infrared wavelengths.

Thus, the combined capabilities of the two telescopes, plus the brightening from gravitational lensing, allowed the team to estimate the galaxy's distance with the highest precision yet achieved for such an observation, Zheng says.

The team also was able to infer something about the galaxy's age and population of stars in the galaxy from the measurements Spitzer made, Zheng says. The proportion of older to younger stars teased from the galaxy's bulk light emissions point to a galaxy no older than about 200 million years.

This was a fecund period for star formation, other researchers have noted. Although solid observations of baby galaxies such as the one Zheng's team uncovered are clearly rare, more-readily spotted galaxies that fall within the next several hundred million years of cosmic evolution boosted their star formation rates 10-fold over that period, according to a paper published last year in Nature by a team led by University of California at Santa Cruz astronomer Rychard Bouwens.

Previous

1 | 2