Astronomy and Astrology

This astronomic diagram example was redesigned from the Wikimedia Commons file: Extragalactic distance ladder.JPG.
[commons.wikimedia.org/ wiki/ File:Extragalactic_ distance_ ladder.JPG]
Red boxes: Technique applicable to star-forming galaxies.
Green boxes: Technique applicable to Population II galaxies.
Cyan boxes: Geometric distance technique.
Pink box: The planetary nebula luminosity function technique is applicable to all populations of the Virgo Supercluster.
Solid lines: Well calibrated ladder step.
Dashed lines: Uncertain calibration ladder step.
"The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A real direct distance measurement of an astronomical object is possible only for those objects that are "close enough" (within about a thousand parsecs) to Earth. The techniques for determining distances to more distant objects are all based on various measured correlations between methods that work at close distances with methods that work at larger distances. Several methods rely on a standard candle, which is an astronomical object that has a known luminosity.
The ladder analogy arises because no one technique can measure distances at all ranges encountered in astronomy. Instead, one method can be used to measure nearby distances, a second can be used to measure nearby to intermediate distances, and so on. Each rung of the ladder provides information that can be used to determine the distances at the next higher rung." [Cosmic distance ladder. Wikipedia]
The astronomy diagram sample "Extragalactic distance ladder" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Astronomy solution from the Science and Education area of ConceptDraw Solution Park.