In olden times, "Natural Sciences" meant the study of pretty much everything. And it showed: being a scientist often meant doing the background work and experimentation spanning what we now call "science", from chemistry to biology to physics. Today's scientific professionals are almost always exclusive to a single field.
That's what makes it so refreshing to think of the crossovers that used to be so common. Without further ado, then, I present...
The List of Elements Named after Astronomical Objects
Helium (Atomic Number 2) - Found based on solar spectral emissions, this element is named after -- hold your breath and wait for it -- the sun.
Selenium (34) - Meaning "moon"; named because of its similarity to tellurium (from "Earth": see below). Those versed in the periodic table will note that selenium falls immediately above her mother tellurium, while those versed in history will note that tellurium was discovered about 35 years earlier. It just made sense.
Palladium (46) - The asteroid Pallas was sighted in 1802. It was the second asteroid ever found, and at just over 500 km in diameter, it's third largest in the inner solar system, after Ceres and Vesta (the two visited by the Dawn spacecraft). Two months after Pallas was identified, William Wollaston used that discovery to coin the element name palladium.
Tellurium (52) - "Tellus" is the Roman name for Earth, which gave us telluride and tellurium, back in the 1780s.
Cerium (58) - Ceres is #1 in the List of Minor Planets. Discovered in 1801 by Giuseppi Piazzi, it also happens to be the only dwarf planet in the inner solar system. Ceres took its name from the god of agriculture, then gave its name to cerium, which was discovered 2 years later (while Ceres was considered a full-fledged planet; this was in the days before the word "asteroid" or term "dwarf planet" had been thought up). Interestingly, Ceres also led to noted self-promoting mathematician/physicist Carl Friedrich Gauss to do some serious work on the orbits of celestial bodies.
Mercury (80) - Named after the planet. Next! No, really, it might not be named after the planet, but rather the Roman god; the ordering is unclear. Mercury -- like Mercury -- has a history stretching back thousands of years, and its chemical symbol (Hg) bespeaks its unusual liquid-at-room-temperature nature (hydragyrum -- "water-silver"). The association with the planet is strong enough that Mercury's planetary symbol has frequently been used to denote mercury the element.
Uranium (92) - Identified (in 1789) 8 years after the discovery of Uranus, this was directly taken from the planet name. Uranus, of course, was the first night sky object that was identified as a planet rather than a star using systematic observation. While it's visible to the naked eye -- and therefore was visible to ancient astronomers -- its dimness and slow motion made it appear more stellar. Continuing with the firsts, then, it was a fine candidate to kick off the name-stuff-after-astronomical-discoveries trend that continued into the 19th century.
Neptunium (93) - Neptune was discovered in 1846, but neptunium wasn't fully isolated until the 1930s and 1940s. Neptunium follows uranium on the periodic table, just as Neptune follows Uranus -- hence the name. Neptunium was more than just a namesake, though, as both share a theory-into-practice history. A large planet perturbing the orbit of Uranus was predicted by Alexis Bouvard based on observed irregularities in the Uranian orbit; mathematician Urban LaVerrier calculated the likely location of the planet, and Johann Galle confirmed the existence with a telescope. The transuranic elements, meanwhile, were predicted to exist based purely on the periodic table, and the Lawrence Livermore National Laboratory was busily seeking them out. Neptunium was the first discovered, and it set the stage for...
Plutonium (94) - In 1940, it was isolated by a team at the University of California, Berkeley. In the spirit of the neptunium turn, the team used Pluto, the next planet (at the time; as I'm sure you know, it's now considered a dwarf planet, and it doesn't seem to be the largest dwarf planet in the solar system), as the basis for this name. The elemental code "Pu" is, apparently, a long-running joke that the team slipped in. Pluto, of course, was named by a British girl; Disney later (likely) took it for the well-known animated dog 10 years before plutonium was isolated. So in a sense, plutonium -- used in nuclear weapons worldwide -- is named after a Disney character. (At least let that bring you a smile if the bombs start flying.)
The List of Not Quites
Elements typically get to be named by their discoverers. In some cases, discoveries are made independently, or someone thinks they've found an element but it's later shown not to be the case. The following were proposed element names that, for one reason or another, just didn't make the cut.
Vestium (not quite 44) - The name chosen by a Polish chemist for ruthenium, but Jedrzej (Andrei) Sniadecki couldn't reproduce his own work, and a later analysis suggests that it did not actually isolate ruthenium anyway. But asteroid Vesta (not quite a dwarf planet due to its mass and shape) had just been discovered, and Sniadecki was jumping on the chance to name his element after that body.
Aldebaranium (not quite 70) - Carl Auer von Welsbach had the star Aldebaran in mind when he proposed this in place of ytterbium -- at the time proposed to be named neoyttrbium. Aldebaran, of course, is the bright star near the "V" in Taurus. Welsbach did get his way when he named both praseodymium and neodymium.
Cassiopium (not quite 71) - Carl Auer von Welsbach strikes again, this time proposing to name something after the constellation Cassiopeia. Element 71 is known as lutetium, after the location where it was found (Lutetia, Sweden). Just so you know, you are likely to still be using a Welsbach flint strike mineral in your cigarette lighter.