Who was Georg Steller and why are that jay and sea lion named after him?

In the Oct-Dec issue of Bay Nature: 

That crested camp-robber eyeing your pretzels, all squawk and blue feathers, is known as a Steller’s jay. And the Steller sea lion, quite vocal in its own right, is a larger, rarer cousin of Pier 39’s infamous California sea lion. Both the bird and the sea lion are native to the West Coast and named for Georg Wilhelm Steller, an 18th-century German botanist, zoologist, physician, and explorer.

...read on!