Astronomers Discover New Way to “See” Elusive Dark Matter Halos

Galaxy Surrounded by Gravitational Distortions Due to Dark Matter

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Artist’s impression of a galaxy surrounded by gravitational distortions due to dark matter. Galaxies live inside bigger concentrations of unnoticeable dark matter (colored purple in this image), nevertheless the dark matter’s impacts can be seen by taking a look at the contortions of background galaxies. Credit: Swinburne Astronomy Productions – James Josephides

A little group of astronomers have actually discovered a brand-new method to ‘see’ the evasive dark matter halos that surround galaxies, with a brand-new method 10 times more exact than the previous-best technique. The work is released in Monthly Notices of the Royal Astronomical Society.

Scientists presently approximate that as much as 85% of the mass in deep space is efficiently unnoticeable. This ‘dark matter’ cannot be observed straight, since it does not communicate with light in the exact same method as the normal matter that comprises stars, worlds, and life on Earth.

So how do we determine what cannot be seen? The secret is to determine the impact of gravity that the dark matter produces.

Distorted Spiral Galaxy

Processed picture of a spiral nebula, as may be observed after lensing impacts have actually misshaped the galaxy’s real shape. By determining the orbital movement of gas within a far-off galaxy (seen here in pink), gravitational distortions can be determined a lot more exactly than was formerly possible. Credit: Original image by ESA / Hubble & NASA / Flickr user Det58, image adjustment by Pol Gurri

Pol Gurri, the PhD trainee at Swinburne University of Technology who led the brand-new research study, discusses: “It’s like looking at a flag to try to know how much wind there is. You cannot see the wind, but the flag’s motion tells you how strongly the wind is blowing.”

The brand-new research study concentrates on an impact called weak gravitational lensing, which is a function of Einstein’s basic theory of relativity. “The dark matter will very slightly distort the image of anything behind it,” states Associate Professor Edward Taylor, who was likewise associated with the research study. “The effect is a bit like reading a newspaper through the base of a wine glass.”

Weak gravitational lensing is currently among the most effective methods to map the dark matter material of the Universe. Now, the Swinburne group has actually utilized the ANU 2.3m Telescope in Australia to map how gravitationally lensed galaxies are turning. “Because we know how stars and gas are supposed to move inside galaxies, we know roughly what that galaxy should look like,” states Gurri. “By measuring how distorted the real galaxy images are, then we can figure out how much dark matter it would take to explain what we see.”

ANU 2.3m Telescope at Siding Spring

Photograph of the Australian National University (ANU) 2.3m telescope at Siding Spring Observatory. Credit: Australian National University

The brand-new research study demonstrates how this speed info allows a a lot more exact measurement of the lensing impact than is possible utilizing shape alone. “With our new way of seeing the dark matter,” Gurri states, “we hope to get a clearer picture of where the dark matter is, and what role it plays in how galaxies form.”

Future area objectives such as NASA’s Nancy Grace Roman Space Telescope and the European Space Agency’s Euclid Space Telescope are developed, in part, to make these type of measurements based upon the shapes of numerous countless galaxies. “We have shown that we can make a real contribution to these global efforts with a relatively small telescope built in the 1980s, just by thinking about the problem in a different way,” includes Taylor.

Reference: “The first shear measurements from precision weak lensing” by Pol Gurri, Edward N Taylor and Christopher J Fluke, 21 September 2020, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/staa2893

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