A new dark matter survey using the Hubble space telescope

MACS J1206.2-0847 galaxy cluster (photo NASA, ESA, M. Postman (STScI), and the CLASH Team)
MACS J1206.2-0847 galaxy cluster (photo NASA, ESA, M. Postman (STScI), and the CLASH Team)

Dark matter is one of the greatest scientific mysteries of our time. Currently, scientists believe that about one quarter of the universe is made of this kind of matter but because it’s invisible and interacts weakly with the rest of matter it’s difficult to make accurate assessments.

Today, the Hubble Space Telescope is used in a project called Cluster Lensing And Supernova survey with Hubble (CLASH) in a survey about dark matter studying twenty-five galaxy clusters.

For this project, astronomers are using the Hubble Space Telescope newest Wide Field optical Camera (WFC3) installed a couple of years ago along with its Advanced Camera for Surveys (ACS) to obtain measurements ranging from ultraviolet to almost infrared. With these instruments scientists can study the gravitational distortions that huge masses such as those of galaxy clusters are causing to light accurately assessing their distances.

This distortion effect is called gravitational lensing because light passing through it changes direction in a manner similar to what happens when it passes through a lens. Doubled or even multiplied images of the same galaxy are often produced as well.

The effect of these gravitational lenses is always greater than it would be expected based on the amount of visible matter present in a galaxy cluster. The difference between the expected effect and the one actually measured helps to evaluate the percentage of dark matter that composes the cluster.

One of the first galaxy clusters observed is called MACS J1206.2-0847 (or MACS 1206 for short), is located about 4.5 billion light years from Earth and is one of the most massive structures known in the entire universe. Obviously the total gravitational effects are huge. In fact, the Hubble Space Telescope has allowed the astronomers of the CLASH project to discover 47 multiple images of 12 newly identified very distant galaxies.

The evaluation of the amount of dark matter in galaxy clusters that appear to us the way they were billions of years ago can provide clues about the early stages of the formation of the universe organized structures.

The Hubble Space Telescope allows sophisticated researches, also thanks to the latest instruments installed and upgraded, but the James Webb Space Telescope, which should be its successor, would be able to make more detailed observations. The problem is that this new space telescope is under production and some components are being tested but the entire project is under review by the U.S.A. Congress because of its cost.

So far more than three billion dollars have been spent and more than five billion dollars are still expected to be spent but there’s a danger that the U.S.A. decides to quit the project. At that point we should hope that European Union, Canada and the other nations participating in the project decided to continue its implementation.

Let’s hope that the James Webb Space Telescope will be finished and put into operation because such a sophisticated instrument would allow us not only to increase our scientific knowledge but it would also help to discover some of the secrets of the universe. That could change our technologies as well and consequently our everyday lives in ways now unforeseeable.

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