A1689-zD1 was the most distant and therefore oldest

Speed of light

The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...

 known galaxy

Galaxy

A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...

 discovered as of February 2008. In October 2010, the discovery of galaxy UDFy-38135539

UDFy-38135539

UDFy-38135539 is the Hubble Ultra Deep Field identifier for a galaxy which has been calculated to have a light travel time of 13.1 billion years with a present comoving distance of around 30 billion light-years...

 at 13 billion light-years made A1689-zD1 the second most distant galaxy in the universe.

Due to its distance, 12.8 billion light-years, and the according considerable redshift, ~7.6, the galaxy's faint light reaches us at infrared wavelengths. It could only be observed with Hubble Space Telescope

Hubble Space Telescope

The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...

's Near Infrared Camera and Multi-Object Spectrometer and the Spitzer Space Telescope

Spitzer Space Telescope

The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...

's Infrared Array Camera exploiting the natural phenomenon of gravitational lensing: The galaxy cluster

Galaxy cluster

A galaxy cluster is a compact cluster of galaxies. Basic difference between a galaxy group and a galaxy cluster is that there are many more galaxies in a cluster than in a group. Also, galaxies in a cluster are more compact and have higher velocity dispersion. One of the key features of cluster is...

 Abell 1689

Abell 1689

Abell 1689 is a galaxy cluster in the constellation Virgo. It is one of the biggest and most massive galaxy clusters known and acts as a gravitational lens, distorting the images of galaxies that lie behind it...

, which lies between Earth and A1689-zD1, at a distance of 2.2 billion light-years from us, functions as a natural "magnifying glass" for the light from the far more distant galaxy which lies directly behind it, at 700 million years after the Big Bang, as seen from Earth.