Gravitational Wobbles

NASA’s Kepler space telescope holds the record when it comes to candidate and confirmed exoplanets — to date, it has identified more than 5,000. To scan the universe for these alien planets, Kepler uses what’s called the “transit method.” Basically, Kepler watches out for the brightness dips that occur when a planet crosses the face of the star it orbits.

This isn’t the only method to catch exoplanets. The High Resolution Echelle Spectrometer (HIRES) instrument at the Keck Observatory in Hawaii detects radial velocity instead of brightness dips. This radial velocity method searches stars for signs of gravitational wobbles induced by orbiting planets. HIRES was part of a two-decade long radical velocity-planet hunting program and it has compiled almost 61,000 individual measurements made of more than 1,600 stars.

“HIRES was not specifically optimized to do this type of exoplanet detective work, but has turned out to be a workhorse instrument of the field,” said Steve Vogt, from the University of California Santa Cruz, who built the instrument. “I am very happy to contribute to science that is fundamentally changing how we view ourselves in the universe.”

From this huge amount of data, a team of researchers led by Paul Butler of the Carnegie Institution for Science in Washington, D.C., identified more than 100 possible exoplanets. Specifically, the researchers identified 60 candidate planets, plus 54 more that require further examination. They published their study in the The Astronomical Journal.

“We were very conservative in this paper about what counts as an exoplanet candidate and what does not,” researcher Mikko Tuomi explained, “and even with our stringent criteria, we found over 100 new likely planet candidates.” Among the candidate exoplanets, one could be orbiting the fourth-closest star (GJ 411) to our Sun just about 8.3 light years away. It’s not an Earth-twin however, as this potential planet has an orbital period that’s equivalent to just 10 days.

Collaborative Exploration

There’s still a considerable amount of data to comb through. So, together with their findings, Butler’s team made the HIRES data set available to the public. “One of our key goals in this paper is to democratize the search for planets,” explained team member Greg Laughlin of Yale. “Anyone can download the velocities published on our website and use the open source Systemic software package and try fitting planets from the data.”

It’s certainly a noble idea and a timely one. “I think this paper sets a precedent for how the community can collaborate on exoplanet detection and follow-up”, said team-member Johanna Teske. “With NASA’s TESS mission on the horizon, which is expected to detect 1000+ planets orbiting bright, nearby stars, exoplanet scientists will soon have a whole new pool of planets to follow up.”

Other tools that can facilitate this search for exoplanets and potentially habitable ones include the recently completed James Webb Space Telescope (JWST). Its powerful array of lenses and mirrors will give our ability to scan the universe a much appreciated boost. Technological advances like the JWST, NASA’s TESS, and a couple of other interstellar eyes will allow us to see the universe like never before.