50 years ago, astronomers were chipping away at Pluto’s mass
Excerpt from the August 28, 1971 issue of Science News
Throughout the 20th century, estimates for the mass of Pluto (right) kept getting smaller. The discovery of Pluto’s moon, Charon (left), helped settle the dwarf planet’s size.
NASA, JHUAPL, SwRI
The shrinking mass of Pluto — Science News, August 28, 1971
Pluto was the last of the planets to be discovered (in 1930).