Personal items of cosmologist Stephen Hawking are going on auction at Christie's for nine days starting Wednesday. The online auction, "On the Shoulders of Giants," will include 22 items from Hawking's estate.

The auction will also offer documents and letters and other items by or associated with Albert Einstein, Charles Darwin and Sir Isaac Newton.

It will include Hawking's Cambridge Ph.D. thesis, "Properties of expanding universes." Dated Oct. 15, 1965, it's signed twice by Hawking, with "This dissertation is my original work" inscribed in the front. It is one of five known hard copies of the thesis and is estimated to sell between $126,000 and $189,000. (In 2017, a digital version of the thesis was offered free via University of Cambridge and was downloaded so many times it crashed the school's servers, according to NPR.)

Hawking's first year at Cambridge, 1962, coincided with his motor neurone disease diagnosis, "leading to a period of depression in which he abandoned his studies," according to Christie's. When it became clear he could live with the disease, he resumed his work. "His thesis is therefore in a sense his expression of renewed confidence in the future, and in many ways set the direction of his future work," writes Christie's.

Another expensive item is a motorized wheelchair that Hawking used from the late 1980s to the mid-1990s, before he became unable to use his hands to drive a chair, according to Christie's. The wheelchair is covered in maroon and red leather and has a metal foot rest. It's expected to fetch $12,600 to $18,900. (The proceeds of the wheelchair will be donated to the Motor Neurone Disease Association and the Stephen Hawking Foundation, Hawking's daughter Lucy said.)