NANOGrav and the IPTA

NANOGrav, or the North American Nanohertz Observatory for Gravitational Waves, is a collaboration of astronomers and physicists from a dozen institutions across the U.S. and Canada. The goal of this ambitious project is to directly detect gravitational waves. Gravitational waves are tiny ripples in the fabric of spacetime. What is spacetime? Spacetime is a concept invented by Albert Einstein in his general theory of relativity. Basically, it is a way of describing how objects move and how clocks tick when they are in a gravitational field. We often think of spacetime as a sheet — in this analogy, a massive object like a bowling ball deforms the sheet, causing other objects to move on a curved path. A similar effect causes planets to move in ellipses around stars. The idea of spacetime as a sheet isn't a perfect one, though...

Gravitational waves are like ripples in this sheet, and they cause the distance between any two points to shrink and stretch (this happens to whole objects, too, meaning that a gravitational wave passing through your head will cause you to get taller and skinnier, and then shorter and fatter). But although we have fantastic (and Nobel prize-winning) evidence for the existence of gravitational waves, they have never been directly observed — we've never seen the actual stretching and shrinking of spacetime. A direct detection of gravitational waves is the near-term goal of NANOGrav, with the longer-term goal being the study of gravitational waves and the objects that create them.

To detect gravitational waves, NANOGrav is using an array of rapidly spinning neutron stars called millisecond pulsars, or MSPs. MSPs can be used like ultra-precise clocks, and gravitational waves will cause these interstellar clocks to appear to run a little fast or a little slow. This technique is somewhat similar to the one used by projects like LIGO and VIRGO, which are looking for tiny changes in the distance between two test objects. But NANOGrav will be able to detect and study gravitational waves from unique sources: relics from the earliest instants after the Big Bang (a period known as Inflation) merging supermassive black holes at the centers of galaxies, and maybe exotic, hypothetical objects called cosmic strings. NANOGrav will almost certainly detect completely unknown and surprising sources of gravitational waves, too.

NANOGrav is a North American effort, but there are similar projects in Europe (the European Pulsar Timing Array) and Australia (the Parkes Pulsar Timing Array). All these projects are cooperating under the framework of something called the International Pulsar Timing Array (IPTA), and together we hope to detect gravitational waves within five to ten years. This could possibly be the first detection ever!

My main role in NANOGrav and the IPTA is as chair of the outreach and education working groups. I'm also involved in NANOGrav research. Our outreach groups record podcasts, create online tools, public talks, social media pages, and work with projects that involve high school students in cutting edge research. We have big ideas for lots of other projects coming up in the near future, so stay tuned by following both NANOGrav and the IPTA on Facebook.