Thousands of extra-solar planets have been detected by the Kepler satellite. Surprisingly, these exoplanets are not like any of the planets in our Solar system, with the majority of them having sizes between Earth and Neptune and orbits within that of Mercury. Compared to such super-Earths, our Solar system planets are either too small or too far away from the host star. Does this mean our Solar system is a special case?
Wei Zhu, the recipient of this year’s Vincent and Beatrice Tremaine Fellowship, tries to answer this question by combining results from different detection techniques. In a recent study [1], he and his collaborators found that super-Earth systems may not be as common as people had thought. By combining the transit and the transit timing variation (TTV) techniques, they found that planetary systems are very hierarchical: systems with many planets or flat and ordered, whereas systems with few planets are chaotic. Based on this result, they re-evaluated the fraction of stars with super-Earths, and found that stars that do not host super-Earths, such as our Sun, are in fact the majority.
In another work [2], Wei further included the cold giant companions from the radial velocity technique. He found that stars with inner small planets (such as super-Earths) also more likely host outer giant planets (such as our Jupiter). This solar system-like architecture, with small planets inside and giant planets outside, is probably very popular among all types of planetary systems, which again confirms that our solar system is not very special.
Wei has been a CITA postdoctoral fellow since the fall of 2017. Prior to coming to CITA, he earned his PhD from The Ohio State University.
The Tremaine Fellowship is given annually in memory of Beatrice D. and Vincent J. Tremaine to honor their lifelong interest in mathematics, science and learning. The award was initially established at CITA by Vincent Tremaine in memory of his wife Beatrice when their son, Scott Tremaine, was the first director.
[1] About 30% of Sun-like Stars Have Kepler-like Planetary Systems: A Study of Their Intrinsic Architecture (http://adsabs.harvard.edu/abs/2018ApJ…860..101Z)
[2] The Super Earth-Cold Jupiter Relations (http://adsabs.harvard.edu/abs/2018AJ….156…92Z)