Dark Matter

Dark Matter makes up about 25% of the Universe, but we can’t see it or feel it (or hear it or anything it!) We can only tell it’s there by its effect on other things due to its gravity.

dark matter piechart cartoon

And don’t even ask about Dark Energy! We know almost nothing about that, but it needs to be about 70% of the Universe so that our observations of the Universe’s expansion make any sense at all.

Collage of six cluster collisions with dark matter maps

These six galaxy clusters have their Dark Matter shown in blue.

Dark Matter doesn’t interact with light, so it’s invisible. The blue shading has been added here by computer. The Dark Matter is found by looking at how light bends because the dark matter’s gravity has affected the shape of space.

Image credits: NASA, ESA, D. Harvey (École Polytechnique Fédérale de Lausanne, Switzerland), R. Massey (Durham University, UK), the Hubble SM4 ERO Team, ST-ECF, ESO, D. Coe (STScI), J. Merten (Heidelberg/Bologna), HST Frontier Fields, Harald Ebeling(University of Hawaii at Manoa), Jean-Paul Kneib (LAM)and Johan Richard (Caltech, USA)

dark matter halos in galaxy clusters

There’s a lot of Dark Matter out there. It causes so much gravity that galaxies clump together in clusters.

This is the Formax cluster about 60 million light years from Earth.

Image credit: NASA/JPL-Caltech


Dark Matter detection challenge. Try to make a model that shows how astronomers can work out where dark matter is.

Stuff a pillow case with some bits of clothing – shirts and socks work well. Make some shapes with the stuffing so that there are hills and valleys on the top of the pillow case. If you roll a small ball or marble down over the surface, it will change direction following the shapes of the clothes.

The challenge is to get somebody else to try and draw out where they think the clothes ‘hills and valleys’ are from just watching the movement of the ball. You could really test them by taking a video like this one:

Challenge someone else: can they find the dark matter you’ve hidden?

Awesome tip: if you have a glow in the dark ball and record a video of it with the lights off then only the ball will be visible, not the pillow shapes!

Scientists used the ball on the pillows idea, following the paths of light rays to make this map of Dark Matter in the Universe

Image credit: NASA/ESA and R. Massey (California Institute of Technology)

You can go to the previous DeepSpace secret pages by clicking the places below.

Distant UniverseBlack Hole