Motions Of Nearby Stars Research Articles

A star passing close to the solar system.

Stellar Astrometry![Figure][1] Many new comets could be produced by the passage of the small star Gliese 710 through the Oort Cloud. PHOTO: WILLIAM ATTARD MCCARTHY/ALAMY STOCK PHOTO The Gaia astrometry satellite has greatly improved measurements of the position and motion of nearby stars. Berski and Dybczynski searched the Gaia data for the star that will pass closest to the Sun. They found that Gliese 710, a small faint star, will pass within 13,000 ± 6,000 astronomical units (one astronomical unit is roughly the distance from Earth to the Sun). That will be well within the Oort Cloud, a collection of small bodies on the outskirts of our solar system. Some of those bodies will be knocked inward, generating large numbers of new comets. Earth is safe for now, though; the encounter will happen in 1.3 million years. Astron. Astrophys. 595 , L10 (2016). [1]: pending:yes

Discovering the rotation of our own galaxy

In the early twentieth century, the Dutch astronomer, Jan Oort, made brilliant use of the two most basic measurements of the motions of nearby stars. These are motions away or towards the Sun based on the Doppler effect, and motion perpendicular to the line of sight, measured as a slow change in the position of the star on the sky. He was able to draw far-reaching conclusions about the rotation and the mass of the Milky Way galaxy in which our Sun is located. His arguments and calculations were based on a simple dynamical model. This model is introduced and described in this article. It can serve as an excellent exercise in an undergraduate physics course, illustrating both mechanical principles and basic astronomy.