Gadget in Extremis: Canada’s Hydrogen Intensity Mapping Experiment


Radio telescope CHIME-770

The Canadian Hydrogen Intensity Mapping Experiment (dubbed CHIME) has begun the largest volume survey of the universe ever undertaken. It’s in the White Lake Basin, south of Penticton in the West of Canada, at the Dominion Radio Astrophysical Observatory, which is operated by the National Research Council of Canada.

With no moving parts, it doesn’t look like, or operate like, most other radio telescopes, but it collects very faint radio signals that arrive from space. Basically, it scans half of the sky each day.

Its “spec” is described as four 100 x 20 metre semi-cylinders each containing 1,024 radio receivers sensitive at 400–800 MHz. Pictured above is one of the semi-cylinders, but you can see the full context below.


According to Wikipedia:

CHIME will make precise measurements of the acceleration of the Universe to improve the knowledge of how dark energy behaves. The experiment is designed to observe the period in the Universe’s history during which the standard CDM model predicts that dark energy began to dominate the energy density of the Universe and when decelerated expansion transitioned to acceleration.

In addition to its main, cosmological purpose, CHIME will also be well-equipped for other astrophysical science. It will be used for discovering and monitoring pulsars and other radio transients, a specialised instrument is being developed for these science objectives.

On the topic of pulsars, the University of British Columbia writes:

Radio pulses travelling through our galaxy and through the space between galaxies change shape, much as ocean waves change shape as they travel. Sharp features and smooth general shapes travel at different speeds. In fact, the pulses only last 1/1,000 seconds at their source, but are spread out over many seconds by the time they reach CHIME. By analysing the signals to put them back to their original spiked shapes, CHIME will learn the distance to the source of each burst.

Neutron stars in our galaxy spin, and the radio waves they emit pierce the sky like the beam from a lighthouse. These radio waves are seen as repetitive pulses and called sources pulsars. These sources act like cosmic clocks and CHIME will monitor the pulses from all known pulsars visible from Penticton, nearly every day. Among other things, this information will aid in the search for gravitational waves—travelling ripples in space-time—passing through our galaxy. It will also lead to new insights into the structure and magnetic fields on neutron stars, and enable other tests of Einstein’s theory of general relativity.

Researchers working on CHIME come from a range of Canadian and USA universities: University of Toronto, National Radio Astronomy Observatory, McGill University, University of British Columbia and the Perimeter Institute.

You can read more online »

Image: University of British Columbia


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