Euclid Found an Entire Galaxy Made of Dark Matter

This is the most powerful  survey telescope in existence. It took 23 countries, 80  companies, 300 institutes, and 3,500 people to build.

A telescope unlike any other. It views the sky with a broad, panoramic view, taking in swathes of stars at once, whilst also focusing with  the precision of a surgeon, spotting the smallest details  from the faintest lights.

This is Euclid. And it needs this unique skillset  to solve a great cosmic mystery that has baffled cosmologists  for more than a century.

Because hidden in the darkness of space lies an enigma that influenced the  development and eventual destiny of our entire Universe.

There is a “dark universe” out there - one we have never seen, or detected. But Euclid intends to map it.

I’m Alex McColgan, and you’re watching Astrum. Join me today in this supercut as we  take a look at the Euclid space telescope and its efforts to chart the  Universe’s dark matter and energy, and explore the incredible discoveries  it has been making along the way.

To understand the need for Euclid, we’ll first need to start by understanding  the mystery that cosmology is facing.

Understanding the structure of this Universe is something we only really began to  do in the last 100 years or so.

We had plenty of understanding  of stars before that point, but it was yet to be discovered how far away  some of those stars actually were. Scientists before then largely believed that the Universe  was just a single galaxy, filled with stars.

Although some astronomers began to spot little  fuzzy patches (actually galaxies) in the sky and postulated them to be “island universes” external  to our own, nothing was proven until the 1920’s, when American Astronomer Edwin Hubble  began studying one such object for himself.

While studying what we now call  the Andromeda galaxy in 1923, Hubble realised that one of the stars he was  looking at was a Cepheid variable star – a type of star that blinks brighter and dimmer over  the course of weeks. Importantly, it had been

proven that these stars’ periods were linked to  their luminosity, so by measuring how regularly the star brightened and dimmed, Hubble could  calculate how bright the star should have been.