Galactic Lenses Confirm Universe's Age, Size

The size and age of the universe, as well as how fast it is expanding, has been confirmed with a new, precise method that uses galaxies as lenses to look at other galaxies.

The new measurement confirmed the age of the universe as 13.75 billion years old, to within 170 million years, and also confirmed the strength of dark energy, which is responsible for the accelerating expansion of the universe.

When looking out at the cosmos, it can be difficult for scientists to distinguish between a very bright light far away and a dimmer source much closer to Earth.

To circumvent this problem, a team of researchers used a technique called gravitational lensing to measure the distances light traveled from a bright, active galaxy to the Earth along different paths, along with data from the Hubble Space Telescope. Researchers can use the observations to infer not just how far away the galaxy lies but also the overall scale of the universe and some details of its expansion.

Size and age

The size of the universe is often expressed by astrophysicists in terms of a quantity called Hubble's constant, which describes the rate at which galaxies in the universe are flying away from each other.

"We've known for a long time that lensing is capable of making a physical measurement of Hubble's constant," said team member Phil Marshall of the researchers at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC). But gravitational lensing had never before been used in such a precise way.

The new measurement provides an equally precise measurement of Hubble's constant as long-established tools such as observation of supernovas (often used as "standard candles" of cosmic distance) and the cosmic microwave background, the remnant radiation of the Big Bang.

The most widely accepted value for the Hubble constant right now is 72 kilometers per second per megaparsec, obtained by the Hubble Space Telescope.

"Gravitational lensing has come of age as a competitive tool in the astrophysicist's toolkit," Marshall said.