The award-winning temporary exhibit What is a Planet? re-opened at the Adler Planetarium and Astronomy Museum, but will close shortly. In 2006, the International Astronomical Union (I.A.U.) voted to reclassify the planet Pluto as a dwarf planet rather than grant recognition as planets to celestial bodies of similar size at the periphery of the Solar System that had been discovered since 1992. Given that Pluto had been considered the ninth planet in the Solar System since its discovery by astronomer Clyde William Tombaugh (1906-1997) in 1930, people around the world were upset at the news.
This was not, however, the first time astronomers had to reconsider the definition of planet due to newly discovered knowledge of the Universe. Astronomers used to think of a planet as any celestial body that moved relative to the stars, but the same could be said of the Sun (which is a star, not a planet); asteroids, which are or seem to be the debris from the formation of planets; meteoroids, which are smaller than asteroids; and comets. There was also the realization that Earth, too, was a planet.
Local Italian-American sculptor and industrial designer Alfonso Iannelli (1888-1965), who also sculpted a bronze plaque representing one of the twelve signs of the zodiac that is inset at each corner of the Adler Planetarium’s facade, sculpted the eight planets then accepted by astronomers on display in the building’s lobby. Oddly enough, his work was completed before Tombaugh made the discovery at Lowell Observatory of the existence of the dwarf planet Pluto, so when the I.A.U. downgraded Pluto from planetary status to a mere Kuiper Belt Object in 2006, a representation of Pluto did not have to be removed to conform to the current state of scientific opinion.
In the exhibit, one finds artifacts from the museum’s collections that illustrate how the concept of planet has changed over the past 500 years, reactions in the mass media to the reclassification of Pluto, and find out how astronomers determine what is and what is not a planet today. Presented by Bank of America, the exhibit is open through Sunday, August 18, 2019.
Figure 1 Credit: Adler Planetarium Caption: The exhibit won first place in the British Society for the History of Science 2016 Great Exhibitions Competition.
Figure 2 Credit: Adler Planetarium Caption: Astrolabes like this one were used for celestial navigation. This one has forty-one star markers. It is labeled in Latin in Gothic script.
The Adler Planetarium and Astronomy Museum is located at the northeastern corner of Northerly Island, which is really a peninsula. It is the only island from a chain of artificial islands Daniel Hudson Burnham, Senior (1846-1912) and Edward H. Bennett (1874-1954) called for in the Plan of Chicago. Northerly Island is part of the Chicago Park District’s Burnham Park. The Field Museum of Natural History, the John G. Shedd Aquarium, and Adler Planetarium and Astronomy Museum comprise the Museum Campus at the northern end of Burnham Park, east of Grant Park in downtown Chicago. Soldier Field and the Lakeside Center of McCormick Place are immediately south of the Museum Campus. The Arie Crown Theater is inside the Lakeside Center.
Normally, the Adler Planetarium is open from 9:00 a.m. to 4:00 p.m. It is open from 9:00 a.m. to 6:00 p.m. from Memorial Day (May 27, 2019) through Labor Day (September 2, 2019) and during “Winter Break” from Thursday, December 26, 2019 through Wednesday, January 1, 2020. The Adler Planetarium will close early at 2:00 p.m. on Saturday, September 7, 2019. It will be closed on Thanksgiving Day (Thursday, November 28, 2019) and Christmas Day (Wednesday, December 25, 2019).
The address is 1300 South Lake Shore Drive, Chicago, Illinois 60605. The phone number is (312) 922-7827. The Website U.R.L. is https://www.adlerplanetarium.org.