MACS0647-JD : possibly the oldest and farthest galaxy ever seen from Earth
Astronomers spotted the furthest galaxy ever, a little cluster named ‘MACS0647-JD’ b/w the Big and Little Dippers.
- Probably the most distant, and thus oldest, galaxy ever seen.
- Distance from Earth: 13.3 billion light years that created the Universe 13.7 billion years ago.
- Formation: 420 million years after the Big Bang
What is Gravitational Lensing ?
Lensing / gravitational lensing is an effect of Einstein’s theory of general relativity – simply put, mass bends light.
We know that normal lenses like the ones in a magnifying glass / spectacles work by bending light rays that pass through them (a process known as refraction), in order to focus the light somewhere (such as in your eye). Now, Gravitational lensing works in an analogous way.
The gravitational field of a massive object will extend far into space, and cause light rays passing close to that object (and thus through its gravitational field) to be bent and refocused somewhere else. The more massive the object, the stronger its gravitational field and thus the greater the bending of light rays – just like using denser materials to make optical lenses results in a greater amount of refraction.
When astronomers take a telescope image of a part of the night sky, we can see many galaxies on that image. However, in between the Earth and those galaxies is a mysterious entity called dark matter. Dark matter is invisible, but it does have mass, making up around 85% of the mass of the Universe. This means that light rays coming towards us from distant galaxies will pass through the gravitational field of dark matter and thus will be bent by the lensing effect.
The astronomers, grouped under the joint American-European CLASH project, use the orbiting Hubble and Spitzer telescopes as well as employing massive galaxy clusters as cosmic magnifiers to find distant galaxies.
“Gravitational Lensing”, helps astronomers to see galaxies that emit light with a brightness weaker than that of a candle on the Moon, thus undetectable straight via telescopes on Earth.
- CLASH: Cluster Lensing And Supernova survey with Hubble.