sidereal
adjective
si·de·re·al sī-ˈdir-ē-əl 
sə-
: of, relating to, or expressed in relation to stars or constellations : astral
Example Sentences
Recent Examples on the Web Called sidereal time, the measurement calculates the length of a day by comparing the earth's rotation to the stars. 
Aaron Pressman, Fortune, 12 Apr. 2017 One tweet, in particular, has birthed a fair number of inky astronauts floating across a sidereal arm. Jesse Lichtenstein, New York Times, 15 June 2017 With this definition, a sidereal year is something like 365.256363 solar days. Rhett Allain, WIRED, 29 Feb. 2012
Aaron Pressman, Fortune, 12 Apr. 2017 One tweet, in particular, has birthed a fair number of inky astronauts floating across a sidereal arm. Jesse Lichtenstein, New York Times, 15 June 2017 With this definition, a sidereal year is something like 365.256363 solar days. Rhett Allain, WIRED, 29 Feb. 2012 Word History
Etymology
Latin sidereus, from sider-, sidus star, constellation
First Known Use
1612, in the meaning defined above