Ballard was part of a collaborative team that was the first to successfully use the transit-timing variation method. This resulted in her team's confirmation of this theoretical search procedure and the discovery of the Kepler-19 planetary system with that technique.[7] Ballard took part in the discovery of four exoplanets (early numbered) in the Kepler spacecraft mission prior to its finding of significant quantities of planets around other stars.
Ballard was a NASA Carl Sagan Fellow at the University of Washington where she did postdoctoral work;[6] and in 2015 was awarded a Women in Science Fellows postdoctoral fellowship by L'Oréal USA to continue her research at MIT.[5]
The transit-timing variation method (TTV) is one of two techniques, along with the transit-duration variation method, proposed in 2001 by astronomer Jordi Miralda-Escudé.[19] TTV was amplified upon in 2004 by astronomers Matthew J. Holman and Norman W. Murray;[20] and by Eric Agol, Jason Steffen, Re’em Sari, and Will Clarkson.[21]
Ballard was the principal investigator in the 2009 application to use the Spitzer Space Telescope to examine "The First Exoplanet Smaller than the Earth".[22] Ballard led the team which precisely estimated the diameter of Kepler-93b to within 1 percent, using TTV.[16][23]
Activism
When exoplanetologist Geoffrey Marcy resigned from the UC Berkeley faculty over charges that he had sexually harassed female undergraduate students, Ballard came out publicly as one of his victims in order to help bring attention to sexual harassment in academia.[24][25][26] In an interview published by Wired, she said that "In the parking lot outside her apartment [...] he gave her advice about her current relationship. She opened the door and stuck her legs out, eager to leave. [...] He put his hand on the back of her neck and told her to relax, that everything would work out with that boy".[27]
Ballard was one of a number of scientists who expressed concern in "An open letter to SCOTUS from professional physicists drafted by the Equity & Inclusion in Physics & Astronomy group"[33] following oral arguments in the U.S. Supreme Court case commonly known as Fisher II involving inclusiveness in admissions policies at the University of Texas.
^Miralda-Escudé, Jordi (2001), "Orbital perturbations of transiting planets: A possible method to measure stellar quadrupoles and to detect Earth-mass planets", 2001 arXiv: 0104034; 2002 ApJ 564 1019.
^Holman, Matthew J.; and Murray, Norman W. (2004), "The Use of Transit Timing to Detect Extrasolar Planets with Masses as Small as Earth", 2004 arXiv: 0412028; 2005 Science 307 1288.
^Agol, Eric; Steffen, Jason; Sari, Re'em; and Clarkson, Will (2004), "On detecting terrestrial planets with timing of giant planet transits"; 2004 arXiv: 0412032; 2005 MNRAS 359 567.