<page_title> Planets beyond Neptune </page_title> <section_title> Pluto loses Planet X title </section_title> <table> <cell> 1931 <col_header> Year </col_header> </cell> <cell> Nicholson & Mayall <col_header> Notes </col_header> </cell> <cell> 1942 <col_header> Year </col_header> </cell> <cell> 0.91 Earth <col_header> Mass </col_header> </cell> <cell> Wylie <col_header> Notes </col_header> </cell> </table>
In 1931, Nicholson and Mayall calculated Neptune's mass to be equal to 1 Earth, a value similar to the 0.91 Earth mass calculated in 1942 by Lloyd R. Wylie.