Did this man demote Pluto?

David Rabinowitz, a Yale-based astronomer that helped discredit Pluto as a planet, works in his office researching new dwarf planets.
David Rabinowitz, a Yale-based astronomer that helped discredit Pluto as a planet, works in his office researching new dwarf planets. Photo by Yale University .

Yale-based astronomer David Rabinowitz is a part of the reason that Pluto is no longer a planet. In the early 2000s Rabinowitz and his team of Yale-based scientists joined with astronomers at the California Institute of Technology to develop the QUEST camera, the device they used to discover hundreds of celestial bodies the same size and composition as Pluto. Because of this discovery, the official definition of a planet was changed, and Pluto was left out of the official list of planets in the solar system. The News spoke to Rabinowitz Tuesday about his work with Pluto and his current research.

Q: Tell us a little about your work related to Pluto.

A: I worked with Yale researchers professor Charles Baltay, Nan Ellman, Rochelle Lauer, Will Emmet and Tom Hurteau to build one of the largest and most ambitious digital cameras in the world — the QUEST camera. We placed this instrument on the largest wide-field telescope in the world (Caltech’s Palomar Schmidt telescope), and programmed the control system to search the whole sky automatically. Then I collaborated with Caltech scientists Mike Brown, Chad Trujillo and Meg Schwamb (Meg’s now working with us at Yale) to use this instrument to find the most distant objects in the solar system — the icy bodies in the Kuiper Belt beyond Neptune.

We knew there would be many small ones about 100 km across or smaller, from previous searches by ourselves and others. And we know there was one giant object, Pluto, with a diameter of 2000 km. But no one had ever searched the whole northern sky to the faint limits that could now be reached with QUEST. We ended up discovering a whole new population of Pluto-sized objects, including Eris, Sedna, Haumea, Makemake, Orcus, and “Snow White”.

It became obvious that Pluto was not a unique giant among the Kuiper Belt. It was crowded with giant ice balls — a new population of dwarf planets. Largely because of the inconvenience of having to accept so many new objects into the Planet pantheon, and largely because there was no existing classification scheme to distinguish planets from icy remnants, a formal distinction was promulgated. This left Pluto out in the cold, so to speak.

Q: What are the most significant impacts of the reclassification?

A: In truth, the most significant impact is that it captured worldwide attention. The classification system by itself does not alter our observation research, or our science goals — which are ultimately to understand how planets form and evolve. But the realization that scientists couldn’t actually agree on a good definition for a planet exposed the limitations of science. We had been calling ourselves planetary scientists for decades without really knowing the meaning of the term.

Q: Describe your current research a little bit for us. What are you working on now?

A: Currently, I am working with Meg Schwamb and Ellie Hadjiyska to discover more dwarf planets. We moved our camera to another large, wide-field telescope in Chile. Now we are searching the whole southern sky for new dwarf planets. I am also working with professor Baltay and Ellie Hadjiyska to look for exploding stars — supernovae — that will help us determine why the universe is expanding at an ever-increasing rate, instead of slowing down. So on any given clear night in Chile, what is most exciting changes depending on what we find. It could be an ice giant in our own backyard, or unusual explosion in another galaxy.

Q: What, in your opinion, is the most promising frontier in astronomy today?

A: Extrasolar planets is currently the most amazing field. Within our lifetimes, we may find a planet with evidence of life! That will really flip us out.


  • laurele

    No, this man did not demote Pluto. In fact, he was one of several hundred professional astronomers who signed a formal petition rejecting the IAU planet definition and subsequent demotion of Pluto, as can be seen here: http://www.ipetitions.com/petition/planetprotest/ . Pluto and Eris are different from most Kuiper Belt Objects because they are large enough to be rounded by their own gravity, a state known as hydrostatic equilibrium. This makes them complex worlds, geologically differentiated into core, mantle, and crust just like Earth is. Pluto has an atmosphere and weather and rather than being a “iceball,” it is estimated to be 70-75 percent rock. Eris, being marginally smaller but more dense than Pluto, likely has an even higher percentage of rock. It is important to distinguish between these worlds, which are clearly small planets, and the majority of tiny, shapeless asteroids and Kuiper Belt Objects shaped simply by their chemical bonds. The IAU definition represents only one side of an ongoing debate. Those who oppose it favor a geophysical definition in which a planet is defined as a non-self-luminous spheroidal body in orbit around a star. Dwarf planets are simply small planets large enough to be in hydrostatic equilibrium but not large enough to gravitationally dominate their orbits. Significantly, the New Horizons mission, whose Principal Investigator Dr. Alan Stern coined the term dwarf planet back in 1991, continues to refer to Pluto as a planet. For more on the pro-Pluto and dwarf planets as planets argument, visit my Pluto Blog at http://laurelsplutoblog.blogspot.com .

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