Far-off Worlds Studied Through 'Characterization by Proxy'



Our understanding of the size and temperature of planets depends crucially on the size and temperature of the stars they orbit. Astronomers already have a robust way to discern the physical properties of solar-type stars -- those like the Sun -- by measuring the light they emit at different wavelengths and matching that to synthetically created spectra.

"The challenge is that small stars are incredibly difficult to characterize," Ballard said. Those theoretical methods don't work well for what are called M-dwarf stars, lower-mass stars about half the size of the Sun and smaller -- which is too bad, because such stars make up about three-quarters of the universe.

Ballard is using the characterization by proxy method to try to fill this knowledge gap. She is building on what she calls "truly remarkable" work by astronomer Tabetha Boyajian, now at Yale University, who uses a near-infrared interferometer -- an array of telescopes working in unison studying light wavelengths a bit longer than visible light -- to resolve the physical size of relatively nearby stars.




A funny thing also happened along the way: Kepler-61 turned out to be bigger and hotter than expected, which in turn recalibrated planet Kepler-61b's relative size upward as well -- meaning it, too, would be hotter than previously thought and no longer a resident of the star's habitable zone.

All of this caused Ballard to informally subtitle the paper, "How Nearby Stars Bumped a Planet Out of the Habitable Zone."

PIO Contact:
Peter Kelley
+1 206-543-2580

Science Contact:
Sarah Ballard
+1 617-249-3081


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