Yet another new most distant object

Well that didn’t last long. Last week I blogged about the discovery of a new most distant galaxy, and explained how in the years since the publication of Measuring the Universe the redshift of the most distant known object had been pushed back from 5.64 to about 11. A few days later and astronomers announce that the new record holder is at a redshift of 11.9!

The new result comes from UDF12, the Ultra Deep Field 2012, a survey program that points Hubble at a tiny patch of sky (just one-tenth the diameter of the full Moon) in the constellation Fornax. The aim is to take the deepest ever image of the heavens. Astronomers on UDF12 use Hubble’s Wide Field Camera 3 to take infrared pictures with huge exposure times. Very gradually, they build up images of incredibly distant objects. And one of the objects they imaged, UDFj-39546284, has a redshift zof about 11.9: the light that Hubble detects now set off from the galaxy when the Universe was just 380 million years old.

Ultra Deep Field 12

The Hubble Ultra Deep Field, with the redshifts and positions of seven galaxies indicated. The UDF12 program suggests that one of these galaxies has a redshift of 11.9 – the most distant object yet seen.
(Credit: NASA/ESA/R. Ellis/Hubble UDF12 project)

Perhaps the most interesting aspect of this work is that the stars already contain heavy elements, which must have originated in the nuclear reactions taking place in an earlier generation of stars. Even at these redshifts we still haven’t seen the first generation of stars.