The Earliest and Faintest Galaxies in the Universe
A new research observation by an international team of astrophysicists using the Hubble Space Telescope has led to the discovery of the largest sample of the faintest, smallest, and earliest known galaxies in the Universe.
Gravitational lensing is an awesome natural phenomena that allows us to study the farthest and oldest structures in the Universe. It happens when mass within a certain volume reaches the critical density needed to curve space and time. The higher the density, the more dramatic the warping the Universe experiences; therefore we expect to find strong gravitational lensing in areas where galaxies join in groups or clusters. Such huge ensembles are made up of dozens to hundreds of galaxies, each with billions of stars. Yet, not even by adding up all the mass of trillions of stars would we have enough mass, and therefore density, to warp space and time. We need dozens to hundreds of times more mass than what we detect to create the lensing effect we see through telescopes. That’s where dark matter comes in, an exotic form of matter that interacts with the Universe only in gravitational form and that theory and observations show exists in huge quantities around galaxies. Put several galaxies together and you have an exorbitant amount of dark matter in a cluster that is enough to create these space-time distortions.
So how does curved space and time look like? See Figure 1. Remember that because light travels at a finite speed, we see more distant objects as they were farther into the past. Now, put a light emitting object in your mind far, far away. There are a couple of factors that might limit us from detecting the light from that object: 1. something might come between us and that light-emitting object, blocking its light; 2. the —> Read More