Double Stars Overview

By determining the gravitational or mutual orbit of two stars using astrometry, it is possible to derive stellar mass and consequently contribute to and refine contemporary astrophysical theories and knowledge.


What is Time: JD

Julian Dates (JD) are a continuous count of days, and fractions of days, since noon Universal Time on January 1, 4713 BC (on the Julian calendar)


What is an Epoch

An epoch is a particular time period, point in history, or a moment defined by a particular event, and is a moment of time used as a reference point for a time-varying astronomical quantity.



The result of countless different cultures naming the same stars, inconsistent star names have necessitated the need for a dependable and systematic method of stellar nomenclature based on the brightness of stars within any given constellation.


Parsecs and Light Years

Parsecs and light years are common measurements of distance to celestial objects, and the former is especially significant for its importance to scientific writing and its relationship with parallax.

Basic Physics

Kepler’s Laws

Kepler's laws of planetary motion are: the orbits of the planets are ellipses with the sun at one focus, a line from a planet to the sun sweeps over equal areas in equal intervals of time, and a planet’s orbital period (P) squared is proportional to its average distance from the sun (a) cubed


Radial Velocity

A measure of movement towards or away from the observer, radial velocity is just one component of stellar motion that is derived through measurement of the doppler effect.


Telescopes: An Overview

Telescopes gather light from objects, and there are two main types: refractor (uses a lens to bend light) and reflector (uses a mirror to reflect light). Aperture and field of view are two main parameters of telescopes.



Parallax is the apparent shift in position of an object because of a change in the point of view. Closer objects have a larger parallax than farther objects.


Color and Temperature

Star color is based on its temperature (hotter stars are blue, while cooler stars are red), and the color/temperature of a star can be classified into stellar classes