Dark matter

A Hubble Space Telescope image showing gravitational lensing in action. At the centre of the image is a galaxy cluster, which contains so much dark matter mass its gravity is bending the light of more distant objects (seen as curves of light around the cluster). Image Credit: NASA, ESA, J. Richard (CRAL) and J.-P. Kneib (LAM). Acknowledgement: Marc Postman (STScI)

Dark matter – the ‘missing’ Universe

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Latest hunt for dark matter begins

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Big and Small in Space at Ed Sci Festival

The earliest stars in the Universe have been detected for the first time. A team of astronomers found the imprint of starlight's first glow on the cosmic microwave background radiation.

Earliest stars in the Universe detected

The giant elliptical galaxy in the centre of this image, taken by the NASA/ESA Hubble Space Telescope, is the most massive and brightest member of the galaxy cluster Abell 2261. Astronomers refer to it as the brightest cluster galaxy (BCG). Spanning a little over one million light-years, the galaxy is about 20 times the diameter of our Milky Way galaxy. Astronomers used Hubble's Advanced Camera for Surveys and Wide Field Camera 3 to measure the amount of starlight across the galaxy, catalogued as 2MASX J17222717+3207571 but more commonly called A2261-BCG (short for Abell 2261 brightest cluster galaxy). Abell 2261 is located three billion light-years away. The observations were taken between March and May 2011. The Abell 2261 cluster is part of a multi-wavelength survey called the Cluster Lensing And Supernova survey with Hubble (CLASH).

Dark matter study views wobbling galaxies

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Map of the cosmos ‘sees’ dark Universe

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What is dark matter?

This artist’s impression shows the Milky Way galaxy. The blue halo of material surrounding the galaxy indicates the expected distribution of the mysterious dark matter, which was first introduced by astronomers to explain the rotation properties of the galaxy and is now also an essential ingredient in current theories of the formation and evolution of galaxies. New measurements show that the amount of dark matter in a large region around the Sun is far smaller than predicted and have indicated that there is no significant dark matter at all in our neighbourhood. Credit: ESA / NASA

Dark matter left early galaxies alone

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Galaxy found that is 99.99% dark matter

For the calibration of relatively short distances the team observed Cepheid variables. These are pulsating stars which fade and brighten at rates that are proportional to their true brightness and this property allows astronomers to determine their distances. The researchers calibrated the distances to the Cepheids using a basic geometrical technique called parallax. With Hubble’s sharp-eyed Wide Field Camera 3 (WFC3), they extended the parallax measurements further than previously possible, across the Milky Way galaxy. To get accurate distances to nearby galaxies, the team then looked for galaxies containing both Cepheids and Type Ia supernovae. Type Ia supernovae always have the same intrinsic brightness and are also bright enough to be seen at relatively large distances. By comparing the observed brightness of both types of stars in those nearby galaxies, the team could then accurately measure the true brightness of the supernova. Using this calibrated rung on the distance ladder the accurate distance to additional 300 type Ia supernovae in far-flung galaxies was calculated. They compare those distance measurements with how the light from the supernovae is stretched to longer wavelengths by the expansion of space. Finally, they use these two values to calculate how fast the universe expands with time, called the Hubble constant.

Universe is expanding faster than expected

Left: a section of the Illustris simulation showing the distribution of dark matter, with a width and height of 350 million lightyears and a thickness of 300,000 light years. Galaxies are found in the small, white, high-density dots. Right: The same data showing the distribution of normal matter. Credit: Markus Haider / Illustris collaboration

Black holes blast matter into cosmic voids

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Dark matter map reveals early Universe history

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Black holes could be ideal dark matter labs

Collage of six cluster collisions with dark matter maps

Dark matter: the plot thickens