Mike Brown

Michael E. Brown (1965- ) is the Richard and Barbara Rosenberg Professor of Planetary Astronomy at the California Institute of Technology (Caltech). Brown, with collaborators Chad Trujillo and David Rabinowitz, has identified many of the largest and most distant objects in the Solar System since Pluto was found by Clyde Tombaugh in 1930. The increasing number of such objects precipitated a heated and well-publicized debate over Pluto's status as a planet and led to Brown's popular identity as "the man who killed Pluto." He is also a leading researcher in the efforts to prove the existence of Planet X, which would become the outermost planet in Earth's Solar System.

Brown was born on June 5, 1965, in Huntsville, Madison County, to Thomas Brown and Barbara Skaggs. Brown's father was an engineer at the Marshall Space Flight Center, so he grew up surrounded by the space program. As children, Brown and his brother, Andy, built model rockets. In the second grade, when Brown learned how the Moon got its craters, he made a muddy mess out of his backyard and created his own mini-Moonscape by pitching rocks into it. As a teenager, he noticed two bright "stars" near the constellation Orion that moved slightly from night to night. He soon learned that he had "discovered" his first two planets, Jupiter and Saturn—an event that spurred his lifelong quest to find other planets.

After graduating from Virgil I. Grissom high school in 1983, Brown entered Princeton University in Princeton, New Jersey, to study physics. After earning his bachelor's degree in 1987, Brown pursued graduate studies in astronomy at the University of California, Berkeley, where he completed a Ph.D. in 1994, writing a dissertation on the volcanism of Jupiter's innermost large satellite, Io. There Brown met research scientist Jane Luu, co-discoverer of several of the first objects beyond Neptune. Such objects are now thought to be part of the so-called Kuiper Belt, which surrounds the Solar System from the orbit of Neptune beyond Pluto to about 50 times the Earth's distance from the Sun. Pluto is part of this debris ring, which is somewhat like an icy version of the rocky asteroid belt that lies between Mars and Jupiter. Brown became intrigued by the possibility of more icy bodies (known as Kuiper Belt Objects, or KBOs) beyond Neptune, some perhaps even larger than Pluto.

Following post-doctoral appointments in 1995 at the University of Arizona as a Hubble Fellow and in 1996 at Caltech, in 1997 Brown accepted an assistant professor position at Caltech and decided to pursue his investigation of the Kuiper Belt. His first attempt to find large bodies beyond Neptune made use of the Oschin 48-inch Schmidt telescope at the Palomar Observatory on Palomar Mountain in San Diego County, California. With assistants Jean Mueller and Kevin Rykoski, Brown conducted a photographic survey of a sizable fraction of the plane of the Solar System known as the ecliptic, where most planets orbit.

Brown's initial investigation exposed traditional photographic plates over long periods of time to pick up the light from distant bodies. He collected three exposures per night on each telescopic field of view to look for dim objects with an expected slow drift rate in the sky; he then scanned them into a computer for analysis. He found nothing, however, and eventually decided that he might have better results if he could automate his survey and use a more sensitive digital camera. In 2001, he teamed with Chad Trujillo, an astronomer from the University of Hawaii, using a sensitive digital camera that Trujillo had designed, in a new survey with the 48-inch Schmidt telescope at Palomar. By this time, several hundred KBOs had been discovered by other researchers, yet none compared with Pluto in size or mass. Brown and Trujillo were determined to find one. In June 2002, they found what initially appeared to be an object larger than Pluto, but it turned out to be smaller than its brightness implied because of a highly reflective icy surface. It was eventually named Quaoar and was the first of several new KBOs discovered by the team.

In 2003, Yale University's David Rabinowitz joined the team, bringing a new extremely wide-field camera to the survey, and they discovered many objects beyond the orbit of Neptune, including three in one night. In late 2003, the team found an object, subsequently named Sedna, with an orbit much larger than Pluto's; it is believed to be the first discovered member of the so-called Oort Cloud, a hypothesized spherical ring of icy comet-like bodies that surrounds the Solar System. Such objects are believed to be the unprocessed material remaining from the formation of the Solar System. Another particularly noteworthy object, found by the team in January 2005, was famously, if temporarily, dubbed "Xena," after the lead character in the Xena: Warrior Princess television series. The subsequent discovery that it has a moon allowed the researchers to calculate that Xena is more massive than Pluto and thus argue that Pluto should no longer be given status as a planet in the Solar System. In a wry acknowledgment of the uproar they caused about the definition of a planet, they officially named the object Eris, after the Greek goddess of discord, and its moon Dysnomia, the Greek goddess of lawlessness.

By 2005, the accumulated discovery of hundreds of KBOs and even a possible member of the Oort Cloud raised a debate within the astronomical community about how to classify such objects. One school of thought favored the designation as planets of all objects in the Solar System massive enough for gravity to have made them round; a second group insisted that an object must be the gravitationally dominant object in its orbit to be called a planet. At least two committees in the planetary community, one within the International Astronomical Union and another within the American Astronomical Society, failed to reach consensus. This impasse set the stage for what some have dubbed the "Battle of Prague" at the 2006 meeting of the International Astronomical Union, at which the governing body created a new class of "dwarf planets" that includes Pluto, several KBOs such as Eris, and Ceres, the largest body in the belt of rocky debris between Mars and Jupiter (formerly known as the asteroid belt). Although Brown did not attend the IAU meeting, he was one of the early and most outspoken proponents of the view that Pluto and the other KBOs should be classified in some way other than "planet." His role in the discovery of the object that sparked the controversy and his support for the "downgrade" of Pluto have since earned him the tongue-in-cheek name "Pluto killer."

Brown married Diane Binney, whom he had met at Palomar Observatory back in 1996, in March 2003, and the couple has one daughter, Lilah. They live in Pasadena, California. Brown is currently engaged in a search for more distant members of the Oort Cloud and has most recently published research on the existence of so-called Planet X, a giant planet theorized to exist on the outermost edge of our Solar System. He also spends much of his spare time giving public lectures explaining how the demotion of Pluto reflects the discovery that the Solar System is much more complicated and interesting than was previously believed.

Brown has received several major honors for his work, including Caltech's prestigious Feynman Prize for Outstanding Teaching in 2007, the Urey Prize for best young planetary scientist from the American Astronomical Society's Division of Planetary Sciences, a Presidential Early Career Award from the National Science Foundation, and a Sloan Fellowship. In 2012, Brown, along with fellow KBO discoverers David Jewett and Joan Luu, shared the Kavli Prize in astrophysics, awarded by the Norwegian Academy of Arts and Sciences, the Kavli Foundation, and the Norwegian Ministry of Education and Research, for their pioneering work on the outer Solar System. He has also won much recognition in the popular press. In 2006, Wired Online named Brown one of its Top Ten Sexiest Geeks, and Time magazine named him one of the world's 100 most influential people of the year. Brown is the author of How I Killed Pluto and Why It Had It Coming, a best-selling account of the events leading up to Pluto's "death" as a planet and its "rebirth" as a dwarf planet. Additionally, Brown is author or co-author of more than 115 scientific publications.

Additional Resources

Boyle, Alan. The Case for Pluto: How a Little Planet Made a Big Difference. New York: John Wiley & Sons, 2010.

Batygin, Konstantin, and Michael E. Brown. "Evidence for a Distant Giant Planet in the Solar System." Astronomical Journal 151(February 2016); http://iopscience.iop.org/article/10.3847/0004-6256/151/2/22#artAbst.

Rusch, Elizabeth. The Planet Hunter: The Story Behind What Happened to Pluto. Flagstaff, Ariz.: Rising Moon Books, 2007.