Apparent and Absolute Magnitude
Two specific types of magnitudes distinguished by astronomers are:
- Apparent magnitude, the apparent brightness of an object. For example, Alpha Centauri has higher apparent magnitude (i.e. lower value) than Betelgeuse, because it is much closer to the Earth.
- Absolute magnitude, which measures the luminosity of an object (or reflected light for non-luminous objects like asteroids); it is the object's apparent magnitude as seen from a certain distance. For stars it is 10 parsecs (32.6 light years). Betelgeuse has much higher absolute magnitude than Alpha Centauri, because it is much more luminous.
Usually only apparent magnitude is mentioned, because it can be measured directly; absolute magnitude can be calculated from apparent magnitude and distance using;
This is known as the distance modulus, where d is the distance to the star measured in parsecs.
Read more about this topic: Magnitude (astronomy)
Famous quotes containing the words apparent, absolute and/or magnitude:
“Philosophic argument, especially that drawn from the vastness of the universe, in comparison with the apparent insignificance of this globe, has sometimes shaken my reason for the faith that is in me; but my heart has always assured and reassured me that the gospel of Jesus Christ must be Divine Reality. The Sermon on the Mount cannot be a mere human production. This belief enters into the very depth of my conscience. The whole history of man proves it.”
—Daniel Webster (1782–1852)
“Atheism..., that bugbear of women and fools, is the very top and perfection of free-thinking. It is the grand arcanum to which a true genius naturally riseth, by a certain climax or gradation of thought, and without which he can never possess his soul in absolute liberty and repose.”
—George Berkeley (1685–1753)
“Constancy has nothing virtuous in itself, independently of the pleasure it confers, and partakes of the temporizing spirit of vice in proportion as it endures tamely moral defects of magnitude in the object of its indiscreet choice.”
—Percy Bysshe Shelley (1792–1822)