As we read in the last edition of this series, Seth Nicholson’s satellite discoveries spanned nearly four decades. Let’s dial the clock back a bit from the discovery of his last, Jupiter XII, and take stock of the situation just after WWII.
Jupiter had eleven known satellites–the most number for the largest planet. And that seemed fitting. Saturn had nine. Uranus four. Mars two. Earth one. And distant Neptune one. Total of twenty-nine. Until 1900, these satellites had been discovered by telescopic observation. Jupiter’s latest six had been detected using photography–comparing film negatives and noting the movement of a small black dot in the vicinity of the planet.
By mid-20th century detecting a planet’s satellite was fraught with one or two major problems. A closer orbiter would be washed out in the glare of nearby planet. More commonly, the threshhold of size was shrinking. The moons of Mars and the smaller moons of Jupiter were the size of large cities. The smallest moon detected in the 17th century, by contrast, is Tethys, about 700 miles across. (Tethys, by the way, masses more than all of the solar system’s known smaller moons combined.)
After his schooling in the Netherlands, he came to California’s Lick Observatory in 1933. After a two-year sojourn in Cambridge at the Harvard College Observatory, he settled in at the University of Chicago in 1937, where he was noted for his early work in planetary astronomy.
He turned his attention to atmospheres, detecting carbon dioxide on Mars in 1944.
You may recall the other famous Dutch satellite astronomer, Christiaan Huygens. Professor Kuiper followed in three-century-old footsteps and detected methane on Saturn’s moon Titan, the first definitive non-planet atmosphere detected in the solar system.
Did I mention Dr Kuiper was gifted with extraordinarily sharp eyesight? Perhaps it inspired his imagination to look at the night sky and see objects four times fainter than the average skywatcher. His vision, however above average, was of no help for his satellite discoveries. While Seth Nicholson was finding small moons of Jupiter, Kuiper found previously unknown objects in orbit around the sun’s distant ice giants, billions of miles away, and far too faint to be found by a sharp-eyed observer.
Meet Miranda, his 1948 find:
Kuiper, of course, didn’t see it this way. The image above is from NASA’s Voyager 2, taken from 90,000 miles away. The earthbound astronomer is well over a billion miles distant. Far enough away that the planet Uranus washes out the view–at least for the average amateur telescope.
Meet Nereid, his 1949 discovery:
Again, Kuiper didn’t see it so close. This was also imaged by Voyager 2 during its Neptune encounter, but from a distance of a few million miles. The astronomer of the 1940’s was more accustomed to this family portrait:
Arrows mark the two moons of Neptune in this photograph: Triton near the planet, and Nereid the very faint dot.
Two very different satellites discovered in consecutive years. One orbits her planet in a circular way, just outside a ring system. The other orbits in a long loop that takes her from one to six million miles.
Humans will return to Miranda, if only by means of a future Uranus orbiter. Miranda’s irregular landscape begs many questions. Was it blown apart in a collision and reassembled in a random way? Does it harbor ice geysers and volcanoes like another small moon? Curious and imaginative minds will want to know.
Nereid, sorry to say, will likely be forgotten. Future exploration of the Neptune region will focus on the planet, it’s large moon Triton, and its clumpy ring system. Nereid is a bit out of the way, and will be left to future imaginations pondering the dark, lonely bodies of the outer solar system.
This website’s survey of solar system natural satellites now covers everything up to the Space Age. As future posts will show, the dispatching of robot explorers will put a familiar face on most of the natural satellites discovered before the first artificial ones were sent aloft. Stay with us for those journeys of imagination.