Wikipedia: Cosmic distance ladder
This is a Wikipedia discussion of the Cosmic Distance Ladder, the first step of which is examined in this BLOSSOMS lesson.
Wikipedia: Parallax
This is a Wikipedia entry on the Parallax, a displacement or difference in the apparent position of an object viewed along two different lines of sight
ESA Science: Gaia
This is a discussion on the European Space agency website about Gaia, the ambitious mission to chart a three-dimensional map of our Galaxy and the Milky Way.
The European Space Agency: Little Books of Gaia
This is an educational page on the website of the European Space Agency with a wealth of educational resources about space mission, Gaia.
Wikipedia: Hipparcos
This is a Wikipedia entry on the satellite Hipparcos, the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky
ESA Science: Hipparcos
This is an educational page on the website of the European Space Agency about the space mission, Hipparcos.