magnitude

(măg'nĭ-tūd', -tyūd')

1. 1. Greatness of rank or position: "such duties as were expected of a landowner of his magnitude" (Anthony Powell).
   2. Greatness in size or extent: The magnitude of the flood was impossible to comprehend.
   3. Greatness in significance or influence: was shocked by the magnitude of the crisis.
2. Astronomy. The degree of brightness of a celestial body designated on a numerical scale, on which the brightest star has magnitude −1.4 and the faintest visible star has magnitude 6, with the scale rule such that a decrease of one unit represents an increase in apparent brightness by a factor of 2.512. Also called apparent magnitude.
3. Mathematics.
   1. A number assigned to a quantity so that it may be compared with other quantities.
   2. A property that can be described by a real number, such as the volume of a sphere or the length of a vector.
4. Geology. A measure of the amount of energy released by an earthquake, as indicated on the Richter Scale.

[Middle English, from Old French, size, from Latin magnitūdō, greatness, size, from magnus, great.]

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For more information on magnitude, visit Britannica.com.

The brightness of an astronomical object, expressed on a unique numerical scale. The stellar magnitude scale is logarithmic and is inverted in that fainter objects have numerically larger magnitudes. Although used primarily for stars, the stellar magnitude scale can also be used to express the brightness of the Sun, planets, asteroids, comets, nebulae, galaxies, and even background radiation.

Since the brightness of any object varies with wavelength, many different magnitude scales have been defined corresponding to different spectral regions, bandwidths, and methods of observation. Visual magnitudes, corresponding to the sensitivity of the human eye centered in the yellow part of the spectrum, are usually implied if the type is unspecified.

The star catalog of Hipparchus (about 150 B.C.) is thought to have contained approximately 850 naked-eye stars classified according to brightness. The 15 or so brightest stars were referred to as stars of the first magnitude, while second-magnitude stars were on the average two or three times fainter, and so on. The scale is logarithmic because intervals that are perceived as equal intervals are, in fact, equal brightness ratios.

Measurements of brightness ratios in the nineteenth century showed that, on average, stars of the sixth magnitude (near the limit of naked-eye vision) were about 100 times fainter than those of the first. On the scale introduced by N. R. Pogson in 1856 and universally adopted, an interval of 5 magnitudes corresponds to a factor of exactly 100, so that each magnitude corresponds to a factor of 100⁵ ≈ 2.512 ·. The zero point of the Pogson scale was set so that most stars retained their customary magnitudes.

An attractive feature of the magnitude scale is the ease with which fractional magnitudes can be interpreted. Each change of 1% in the brightness of an object corresponds to a change of 0.01 in the magnitude, and this numerical correspondence holds to good accuracy for changes up to about 30%.

A distinction is made between the apparent magnitude of an object viewed from the Earth and its absolute magnitude, which measures the object's intrinsic luminosity by indicating its apparent magnitude as seen from a standard distance. The absolute magnitude may be defined as the apparent magnitude an object would have if viewed from a distance of 10 parsecs (1 pc = 3.26 light-years = 1.92 × 10¹³ mi = 3.09 × 10¹³ km). See also Parsec.

astronomy The range of brightness of the different stars prompted the Greeks to introduce a numeric scale for them, with 1 for the brightest and 6 for the faintest they could see, such numbers being called magnitude. The telescope expanded the visible, and hence the scale. The scale was given a mathematical basis in the 19th century, the five steps from 1 to 6 being defined as forming a geometric scale accumulating to a 100-fold increase in brightness (close to the amount from 1 to 6 in the Greek scale); hence an increment of 1 toward the brighter end of the scale represents a multiplicative increase in brightness of

M = 5 + m - 5log₁₀d

noun

1. Great extent, amount, or dimension: amplitude, bulk, mass, size, volume (often used in plural). See big/small/amount.
2. The quality or state of being large in amount, extent, or importance: amplitude, bigness, greatness, largeness, sizableness, size. See big/small/amount.
3. Relative intensity or amount, as of a quality or attribute: degree, extent, measure, proportion. See big/small/amount.
4. The amount of space occupied by something: dimension, extent, measure, proportion (often used in plural), size. See big/small/amount.

Definition: importance
Antonyms: insignificance, triviality, unimportance

n

Definition: size
Antonyms: littleness, smallness, tininess

Of an earthquake, an expression of the total energy released. See Richter scale.

Term used in science to specify size or amount.

The size of an earthquake, typically reported using the Richter scale. As originally defined by Richter, the magnitude of an earthquake is the logarithm of the amplitude of the largest seismic wave recorded on a particular kind of seismometer located 100 km from the earthquake epicenter. Seismologists today use a variety of magnitude scales that produce similar, but not identical, estimates of earthquake size.

Astronomical brightness measured on a logarithmic scale, based on the ancient practice of noting that the brightest stars in the sky were of "first importance" or "first magnitude", the next brightest being "second magnitude" etc. The human eye is a logarithmic detector, and in 1854 Pogson formalized this scale and defined a difference of 5 magnitudes to be exactly a factor of 100 in brightness. The scale is calibrated to the bright star Vega which is defined to have a magnitude of 0. For reference, the faintest naked-eye magnitude visible from a dark site is +6. Comet C/1996 B2 Hyakutake reached magnitude 0 in late March 1996.

n.

Size. Magnitude being purely relative, nothing is large and nothing small. If everything in the universe were increased in bulk one thousand diameters nothing would be any larger than it was before, but if one thing remain unchanged all the others would be larger than they had been. To an understanding familiar with the relativity of magnitude and distance the spaces and masses of the astronomer would be no more impressive than those of the microscopist. For anything we know to the contrary, the visible universe may be a small part of an atom, with its component ions, floating in the life- fluid (luminiferous ether) of some animal. Possibly the wee creatures peopling the corpuscles of our own blood are overcome with the proper emotion when contemplating the unthinkable distance from one of these to another.

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• Branches, Laws, Theories, and Techniques - magnitude: brightness of star in sky measured on logarithmic scale from zero (brightest) to five (faintest), with fifth-magnitude stars being 100 times fainter than zero-magnitude stars

Asteroid 65 Cybele and 2 stars with their magnitudes labeled

The apparent magnitude (m) of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere. The brighter the object appears, the lower the value of its magnitude.

Contents 1 History 2 Table of notable celestial objects 3 Calculations 3.1 Example 1 - Sun and Moon 3.2 Example 2 - Sirius and Polaris 3.3 Addition 4 See also 5 References 6 External links

History

Visible to typical human eye	Apparent magnitude	Brightness relative to Vega	Number of stars brighter than apparent magnitude[1]
Yes	−1	250%	1
	0	100%	4
	1	40%	15
	2	16%	48
	3	6.3%	171
	4	2.5%	513
	5	1.0%	1 602
	6	0.40%	4 800
No	7	0.16%	14 000
	8	0.063%	42 000
	9	0.025%	121 000
	10	0.010%	340 000

The scale now used to indicate magnitude originates in the Hellenistic practice of dividing stars visible to the naked eye into six magnitudes. The brightest stars were said to be of first magnitude (m = 1), while the faintest were of sixth magnitude (m = 6), the limit of human visual perception (without the aid of a telescope). Each grade of magnitude was considered twice the brightness of the following grade (a logarithmic scale). This somewhat crude method of indicating the brightness of stars was popularized by Ptolemy in his Almagest, and is generally believed to originate with Hipparchus. This original system did not measure the magnitude of the Sun. (For a more detailed discussion of the history of the magnitude system, see Magnitude.)

In 1856, Norman Robert Pogson formalized the system by defining a typical first magnitude star as a star that is 100 times as bright as a typical sixth magnitude star; thus, a first magnitude star is about 2.512 times as bright as a second magnitude star. The fifth root of 100 is known as Pogson's Ratio.^[2] Pogson's scale was originally fixed by assigning Polaris a magnitude of 2. Astronomers later discovered that Polaris is slightly variable, so they first switched to Vega as the standard reference star, and then switched to using tabulated zero points^{[clarification needed]} for the measured fluxes.^[3] The magnitude depends on the wavelength band (see below).

The modern system is no longer limited to 6 magnitudes or only to visible light. Very bright objects have negative magnitudes. For example, Sirius, the brightest star of the celestial sphere, has an apparent magnitude of –1.4. The modern scale includes the Moon and the Sun. The full Moon has a mean apparent magnitude of –12.74^[4] and the Sun has an apparent magnitude of –26.74.^[5] The Hubble Space Telescope has located stars with magnitudes of 30 at visible wavelengths and the Keck telescopes have located similarly faint stars in the infrared.

Table of notable celestial objects

Apparent visual magnitudes of known celestial objects

App. Mag. (V)	Celestial object
–38.00	Rigel as seen from 1 astronomical unit. It is seen as a large very bright bluish scorching ball of 35° apparent diameter.
–30.30	Sirius as seen from 1 astronomical unit
–29.30	Sun as seen from Mercury at perihelion
–27.40	Sun as seen from Venus at perihelion
–26.74[5]	Sun (398,359 times brighter than mean full moon)
–25.60	Sun as seen from Mars at aphelion
–23.00	Sun as seen from Jupiter at aphelion
–21.70	Sun as seen from Saturn at aphelion
–20.20	Sun as seen from Uranus at aphelion
–19.30	Sun as seen from Neptune
–18.20	Sun as seen from Pluto at aphelion
–16.70	Sun as seen from Eris at aphelion
–12.92	Maximum brightness of full Moon (mean is –12.74)[4]
–11.20	Sun as seen from Sedna at aphelion
–10	Comet Ikeya–Seki (1965) which was the brightest Kreutz Sungrazer of modern times[6]
–9.50	Maximum brightness of an Iridium (satellite) flare
–7.50	The SN 1006 supernova of AD 1006, the brightest stellar event in recorded history[7]
–6.50	The total integrated magnitude of the night sky as seen from Earth
–6.00	The Crab Supernova (SN 1054) of AD 1054 (6500 light years away)[8]
–5.9	International Space Station (when the ISS is at its perigee and fully lit by the Sun)[9]
–4.89	Maximum brightness of Venus[10] when illuminated as a crescent
–4.00	Faintest objects observable during the day with naked eye when Sun is high
–3.99	Maximum brightness of Epsilon Canis Majoris, the brightest star of the last and next five million years
–3.82	Minimum brightness of Venus when it is on the far side of the Sun
–2.94	Maximum brightness of Jupiter[11]
–2.91	Maximum brightness of Mars[12]
–2.50	Faintest objects visible during the day with naked eye when Sun is less than 10° above the horizon
–2.50	Minimum brightness of new Moon
–2.45	Maximum brightness of Mercury at superior conjunction (unlike Venus, Mercury is at its brightest when on the far side of the Sun, the reason being their different phase curves)
–1.61	Minimum brightness of Jupiter
–1.47	Brightest star (except for the Sun) at visible wavelengths: Sirius[13]
–0.83	Eta Carinae apparent brightness as a supernova impostor in April 1843
–0.72	Second-brightest star: Canopus[14]
–0.49	Maximum brightness of Saturn at opposition and when the rings are full open (2003, 2018)
–0.27	The total magnitude for the Alpha Centauri AB star system. (Third-brightest star to the naked eye)
–0.04	Fourth-brightest star to the naked eye Arcturus[15]
−0.01	Fourth-brightest individual star visible telescopically in the sky Alpha Centauri A
+0.03	Vega, which was originally chosen as a definition of the zero point[16]
+0.50	Sun as seen from Alpha Centauri
1.47	Minimum brightness of Saturn
1.84	Minimum brightness of Mars
3.03	The SN 1987A supernova in the Large Magellanic Cloud 160,000 light-years away.
3 to 4	Faintest stars visible in an urban neighborhood with naked eye
3.44	The well known Andromeda Galaxy (M31)[17]
4.38	Maximum brightness of Ganymede[18] (moon of Jupiter and the largest moon in the Solar System)
4.50	M41, an open cluster that may have been seen by Aristotle[19]
5.14	Maximum brightness of Vesta asteroid
5.32	Maximum brightness of Uranus[20]
5.72	The spiral galaxy M33, which is used as a test for naked eye seeing under dark skies[21][22]
5.73	Minimum brightness of Mercury
5.8	Peak visual magnitude of gamma ray burst GRB 080319B (the "Clarke Event") seen on Earth on March 19, 2008 from a distance of 7.5 gigalight-years.
5.95	Minimum brightness of Uranus
6.40	Maximum brightness of asteroid Pallas
6.50	Approximate limit of stars observed by a mean naked eye observer under very good conditions. There are about 9,500 stars visible to mag 6.5.[23]
6.73	Maximum brightness of dwarf planet Ceres in the asteroid belt
6.75	Maximum brightness of asteroid Iris
6.90	The spiral galaxy M81 is an extreme naked eye target that pushes human eyesight and the Bortle Dark-Sky Scale to the limit[24]
7 to 8	Extreme naked eye limit with class 1 Bortle Dark-Sky Scale, the darkest skies available on Earth[25]
7.78	Maximum brightness of Neptune[26]
8.02	Minimum brightness of Neptune
8.10	Maximum brightness of Titan (largest moon of Saturn),[27][28] mean opposition magnitude 8.4[29]
9.01	Maximum brightness of asteroid 10 Hygiea[30]
9.50	Faintest objects visible using common 7x50 binoculars under typical conditions[31]
10.20	Maximum brightness of Iapetus[28] (brightest when west of Saturn and takes 40 days to switch sides)
12.91	Brightest quasar 3C 273 (luminosity distance of 2.4 giga-light years)
13.42	Maximum brightness of Triton[29]
13.65	Maximum brightness of Pluto[32] (725 times fainter than magnitude 6.5 naked eye skies)
15.40	Maximum brightness of centaur Chiron[33]
15.55	Maximum brightness of Charon (the large moon of Pluto)
16.80	Current opposition brightness of Makemake[34]
17.27	Current Opposition brightness of Haumea[35]
18.70	Current Opposition brightness of Eris
20.70	Callirrhoe (small ~8 km satellite of Jupiter)[29]
22.00	Approximate limiting magnitude of a 24" Ritchey-Chrétien telescope with 30 minutes of stacked images (6 subframes at 300s each) using a CCD detector[36]
22.91	Maximum brightness of Pluto's moon Hydra
23.38	Maximum brightness of Pluto's moon Nix
24.80	Amateur picture with greatest magnitude: quasar CFHQS J1641 +3755[37][38]
25.00	Fenrir (small ~4 km satellite of Saturn)[39]
27.00	Faintest objects observable in visible light with 8m ground-based telescopes
28.00	Jupiter if it were located 5000AU from the Sun[40]
28.20	Halley's Comet in 2003 when it was 28AU from the Sun[41]
31.50	Faintest objects observable in visible light with Hubble Space Telescope
35.00	Sedna at aphelion (900 AU)
35.00	LBV 1806-20, a luminous blue variable star, at visible wavelengths
36.00	Faintest objects observable in visible light with E-ELT
(see also List of brightest stars)

The above are only approximate values at visible wavelengths (in reality the values depend on the precise bandpass used) — see airglow for more details of telescope sensitivity.

Calculations

30 Doradus image taken by ESO's VISTA. This nebula has an apparent magnitude of 8.

As the amount of light received actually depends on the thickness of the Earth's atmosphere in the line of sight to the object, the apparent magnitudes are adjusted to the value they would have in the absence of the atmosphere. The dimmer an object appears, the higher its apparent magnitude. Note that brightness varies with distance; an extremely bright object may appear quite dim, if it is far away. Brightness varies inversely with the square of the distance. The absolute magnitude, M, of a celestial body (outside the Solar System) is the apparent magnitude it would have if it were 10 parsecs (~32.6 light years) away; that of a planet (or other Solar System body) is the apparent magnitude it would have if it were 1 astronomical unit away from both the Sun and Earth. The absolute magnitude of the Sun is 4.83 in the V band (yellow) and 5.48 in the B band (blue).^[42]

The apparent magnitude, m, in the band, x, can be defined as m_x below (noting that )

where is the observed flux in the band x, and is a reference flux in the same band x, such as the Vega star's for example. See Aller et al. 1982 for the most commonly used system.

Since an increase of 1 in the magnitude scale corresponds to a decrease in brightness by a certain factor, the factor would be , which is 2.512...

The variation in brightness between two luminous objects can be calculated another way by subtracting the magnitude number of the brighter object from the magnitude number of the fainter object, then using the difference as an exponent for the base number 2.512; that is to say (m_f − m_b = x; and 2.512^x = variation in brightness).

Example 1 - Sun and Moon

What is the ratio in brightness between the Sun and the full moon?

2.512^x = variation in brightness

The apparent magnitude of the Sun is -26.74, and the mean apparent magnitude of the full moon is -12.74. The full moon is the fainter of the two objects, while the Sun is the brighter.

Difference in magnitude

Variation in Brightness

variation in brightness = 398,359

In terms of apparent magnitude, the Sun is about 398,359 times brighter than the full moon.

Example 2 - Sirius and Polaris

What is the ratio in brightness between Sirius and Polaris?

variation in brightness

The apparent magnitude of Sirius is -1.44, and the apparent magnitude of Polaris is 1.97. Polaris is the fainter of the two stars, while Sirius is the brighter.

Difference in magnitude

Variation in brightness

In terms of apparent magnitude, Sirius is 23.124 times brighter than Polaris the North Star.

Addition

It is sometimes also necessary to add magnitudes, for example, to determine the combined magnitude of a double star when the magnitude of the individual components are known. This can be done by setting an equation using the brightness (in linear units) of each magnitude.^[43]

Solving for m_f yields

where m_f is the result of adding m₁ and m₂.

It is important to note that the scale is logarithmic: the relative brightness of two objects is determined by the difference of their magnitudes. For example, a difference of 3.2 means that one object is about 19 times as bright as the other, because Pogson's ratio raised to the power 3.2 is 19.054607... A common misconception is that the logarithmic nature of the scale is because the human eye itself has a logarithmic response. In Pogson's time this was thought to be true (see Weber-Fechner law), but it is now believed that the response is a power law (see Stevens' power law).^[44]

Magnitude is complicated by the fact that light is not monochromatic. The sensitivity of a light detector varies according to the wavelength of the light, and the way it varies depends on the type of light detector. For this reason, it is necessary to specify how the magnitude is measured for the value to be meaningful. For this purpose the UBV system is widely used, in which the magnitude is measured in three different wavelength bands: U (centred at about 350 nm, in the near ultraviolet), B (about 435 nm, in the blue region) and V (about 555 nm, in the middle of the human visual range in daylight). The V band was chosen for spectral purposes and gives magnitudes closely corresponding to those seen by the light-adapted human eye, and when an apparent magnitude is given without any further qualification, it is usually the V magnitude that is meant, more or less the same as visual magnitude.

Since cooler stars, such as red giants and red dwarfs, emit little energy in the blue and UV regions of the spectrum their power is often under-represented by the UBV scale. Indeed, some L and T class stars have an estimated magnitude of well over 100, since they emit extremely little visible light, but are strongest in infrared.

Measures of magnitude need cautious treatment and it is extremely important to measure like with like. On early 20th century and older orthochromatic (blue-sensitive) photographic film, the relative brightnesses of the blue supergiant Rigel and the red supergiant Betelgeuse irregular variable star (at maximum) are reversed compared to what our eyes see since this archaic film is more sensitive to blue light than it is to red light. Magnitudes obtained from this method are known as photographic magnitudes, and are now considered obsolete.

For objects within our Galaxy with a given absolute magnitude, 5 is added to the apparent magnitude for every tenfold increase in the distance to the object. This relationship does not apply for objects at very great distances (far beyond our galaxy), since a correction for General Relativity must then be taken into account due to the non-Euclidean nature of space.

For planets and other Solar System bodies the apparent magnitude is derived from its phase curve and the distances to the Sun and observer.

See also

• Magnitude (astronomy)
• Photographic magnitude
• Luminosity in astronomy
• List of brightest stars
• List of nearest bright stars
• List of nearest stars
• Lux
• Surface brightness
• Distance modulus

References

1. ^ "Magnitude". National Solar Observatory—Sacramento Peak. Archived from the original on 2008-02-06. http://replay.waybackmachine.org/20080206074842/http://www.nso.edu/PR/answerbook/magnitude.html. Retrieved 2006-08-23. 
2. ^ Magnitudes of Thirty-six of the Minor Planets for the first day of each month of the year 1857, N. Pogson, MNRAS Vol. 17, p. 12 (1856)
3. ^ Landolt-Börnstein: Numerical Data and Functional Relationships in Science and Technology - New Series " Gruppe/Group 6 Astronomy and Astrophysics " Volume 2 Schaifers/Voigt: Astronomy and Astrophysics / Astronomie und Astrophysik " Stars and Star Clusters / Sterne und Sternhaufen L. H. Aller et al., ISBN 3-540-10976-5 (1982)
4. ^ ^{a b} Williams, Dr. David R. (2010-02-02). "Moon Fact Sheet". NASA (National Space Science Data Center). http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html. Retrieved 2010-04-09. 
5. ^ ^{a b} Williams, Dr. David R. (2004-09-01). "Sun Fact Sheet". NASA (National Space Science Data Center). http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html. Retrieved 2010-07-03. 
6. ^ "Brightest comets seen since 1935". International Comet Quarterly. http://www.icq.eps.harvard.edu/brightest.html. Retrieved 18 December 2011. 
7. ^ Winkler, P. Frank; Gupta, Gaurav; Long, Knox S. (2003). "The SN 1006 Remnant: Optical Proper Motions, Deep Imaging, Distance, and Brightness at Maximum". The Astrophysical Journal 585: 324–335. arXiv:astro-ph/0208415. Bibcode 2003ApJ...585..324W. doi:10.1086/345985. 
8. ^ Supernova 1054 - Creation of the Crab Nebula
9. ^ "ISS Information - Heavens-above.com". Heavens-above. http://www.heavens-above.com/satinfo.aspx?SatID=25544. Retrieved 2007-12-22. 
10. ^ "HORIZONS Web-Interface for Venus (Major Body=299)". JPL Horizons On-Line Ephemeris System. 2006-Feb-27 (GEOPHYSICAL DATA). http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=mb&sstr=299. Retrieved 2010-11-28.  (Using JPL Horizons you can see that on 2013-Dec-08 Venus will have an apmag of -4.89)
11. ^ Williams, David R. (2007-11-02). "Jupiter Fact Sheet". National Space Science Data Center. NASA. http://nssdc.gsfc.nasa.gov/planetary/factsheet/jupiterfact.html. Retrieved 2010-06-25. 
12. ^ Williams, David R. (2007-11-29). "Mars Fact Sheet". National Space Science Data Center. NASA. http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html. Retrieved 2010-06-25. 
13. ^ "Sirius". SIMBAD Astronomical Database. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Sirius. Retrieved 2010-06-26. 
14. ^ "Canopus". SIMBAD Astronomical Database. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Canopus. Retrieved 2010-06-26. 
15. ^ "Arcturus". SIMBAD Astronomical Database. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Arcturus. Retrieved 2010-06-26. 
16. ^ "Vega". SIMBAD Astronomical Database. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Vega. Retrieved 2010-04-14. 
17. ^ "SIMBAD-M31". SIMBAD Astronomical Database. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=M31. Retrieved 2009-11-29. 
18. ^ Yeomans and Chamberlin. "Horizon Online Ephemeris System for Ganymede (Major Body 503)". California Institute of Technology, Jet Propulsion Laboratory. http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=mb&sstr=503. Retrieved 2010-04-14.  (4.38 on 1951-Oct-03)
19. ^ "M41 possibly recorded by Aristotle". SEDS (Students for the Exploration and Development of Space). 2006-07-28. http://www.seds.org/messier/more/m041_ari.html. Retrieved 2009-11-29. 
20. ^ Williams, David R. (2005-01-31). "Uranus Fact Sheet". National Space Science Data Center. NASA. http://nssdc.gsfc.nasa.gov/planetary/factsheet/uranusfact.html. Retrieved 2010-06-25. 
21. ^ "SIMBAD-M33". SIMBAD Astronomical Database. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=M33. Retrieved 2009-11-28. 
22. ^ Jerry Lodriguss (1993). "M33 (Triangulum Galaxy)". http://www.astropix.com/HTML/A_FALL/M33.HTM. Retrieved 2009-11-27.  (shows b mag not v mag)
23. ^ "Vmag<6.5". SIMBAD Astronomical Database. http://simbad.u-strasbg.fr/simbad/sim-sam?Criteria=Vmag%3C6.5. Retrieved 2010-06-25. 
24. ^ "Messier 81". SEDS (Students for the Exploration and Development of Space). 2007-09-02. http://www.seds.org/messier/m/m081.html. Retrieved 2009-11-28. 
25. ^ John E. Bortle (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. http://www.skyandtelescope.com/resources/darksky/3304011.html. Retrieved 2009-11-18. 
26. ^ Williams, David R. (2007-11-29). "Neptune Fact Sheet". National Space Science Data Center. NASA. http://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html. Retrieved 2010-06-25. 
27. ^ Yeomans and Chamberlin. "Horizon Online Ephemeris System for Titan (Major Body 606)". California Institute of Technology, Jet Propulsion Laboratory. http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=mb&sstr=606. Retrieved 2010-06-28.  (8.10 on 2003-Dec-30)
28. ^ ^{a b} "Classic Satellites of the Solar System". Observatorio ARVAL. http://www.oarval.org/ClasSaten.htm. Retrieved 2010-06-25. 
29. ^ ^{a b c} "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 2009-04-03. http://ssd.jpl.nasa.gov/?sat_phys_par. Retrieved 2009-07-25. 
30. ^ "AstDys (10) Hygiea Ephemerides". Department of Mathematics, University of Pisa, Italy. http://hamilton.dm.unipi.it/astdys/index.php?pc=1.1.3.1&n=10&oc=500&y0=2095&m0=6&d0=27&h0=00&mi0=00&y1=2095&m1=6&d1=28&h1=00&mi1=00&ti=1.0&tiu=days. Retrieved 2010-06-26. 
31. ^ Ed Zarenski (2004). "Limiting Magnitude in Binoculars". Cloudy Nights. http://www.cloudynights.com/documents/limiting.pdf. Retrieved 2011-05-06. 
32. ^ Williams, David R. (2006-09-07). "Pluto Fact Sheet". National Space Science Data Center. NASA. http://nssdc.gsfc.nasa.gov/planetary/factsheet/plutofact.html. Retrieved 2010-06-26. 
33. ^ "AstDys (2060) Chiron Ephemerides". Department of Mathematics, University of Pisa, Italy. http://hamilton.dm.unipi.it/astdys/index.php?pc=1.1.3.1&n=2060&oc=500&y0=2097&m0=4&d0=3&h0=00&mi0=00&y1=2097&m1=4&d1=3&h1=00&mi1=00&ti=1.0&tiu=days. Retrieved 2010-06-26. 
34. ^ "AstDys (136472) Makemake Ephemerides". Department of Mathematics, University of Pisa, Italy. http://hamilton.dm.unipi.it/astdys/index.php?pc=1.1.3.1&n=136472&oc=500&y0=2010&m0=3&d0=17&h0=00&mi0=00&y1=2010&m1=3&d1=17&h1=00&mi1=00&ti=1.0&tiu=days. Retrieved 2010-06-26. 
35. ^ "AstDys (136108) Haumea Ephemerides". Department of Mathematics, University of Pisa, Italy. http://hamilton.dm.unipi.it/astdys/index.php?pc=1.1.3.1&n=136108&oc=500&y0=2010&m0=4&d0=6&h0=00&mi0=00&y1=2010&m1=4&d1=6&h1=00&mi1=00&ti=1.0&tiu=days. Retrieved 2010-06-26. 
36. ^ Steve Cullen (sgcullen) (2009-10-05). "17 New Asteroids Found by LightBuckets". LightBuckets. http://www.lightbuckets.com/news/37/17-new-asteroids-found-by-lightbuckets/. Retrieved 2009-11-15. 
37. ^ Cooperation with Ken Crawford
38. ^ "CRedshift 6 Quasar (CFHQS J1641 +3755)". http://panther-observatory.com/gallery/deepsky/doc/CFHQS_J1641_f10.htm. 
39. ^ Scott S. Sheppard. "Saturn's Known Satellites". Carnegie Institution (Department of Terrestrial Magnetism). http://www.dtm.ciw.edu/users/sheppard/satellites/satsatdata.html. Retrieved 2010-06-28. 
40. ^ Magnitude difference is 2.512*log₁₀[(5000/5)^2 X (4999/4)^2] ≈ 30.6, so Jupiter is 30.6 mag fainter at 5000 AU
41. ^ "New Image of Comet Halley in the Cold". ESO. 2003-09-01. http://www.eso.org/public/outreach/press-rel/pr-2003/phot-27-03.html. Retrieved 2009-02-22. 
42. ^ Prof. Aaron Evans. "Some Useful Astronomical Definitions". Stony Brook Astronomy Program. http://www.astro.sunysb.edu/aevans/PHY523/classnotes523/useful-definitions-pp.pdf. Retrieved 2009-07-12. 
43. ^ "Magnitude Arithmetic". Weekly Topic. Caglow. http://www.caglow.com/info/wtopic/mag-arith. Retrieved 30 January 2012. 
44. ^ E. Schulman and C. V. Cox (1997). "Misconceptions About Astronomical Magnitudes". American Journal of Physics 65: 1003. Bibcode 1997AmJPh..65.1003S. doi:10.1119/1.18714. 

External links

• The astronomical magnitude scale (International Comet Quarterly)

v d e Star Evolution Formation Pre–main sequence Main sequence Horizontal branch Asymptotic giant branch Dredge-up Instability strip Red clump PG1159 star Mira variable Planetary nebula Protoplanetary nebula Luminous red nova Luminous blue variable Wolf–Rayet star Supernova impostor Supernova Hypernova Hertzsprung–Russell diagram Color–color diagram Protostars Molecular cloud H II region Bok globule Young stellar object Herbig–Haro object Hayashi track Hayashi limit Henyey track Orion T Tauri FU Orionis Herbig Ae/Be Luminosity class Subdwarf Dwarf Blue Red Subgiant Giant Blue Red Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Blue straggler Spectral classification O B A F G K M Be OB Subdwarf B Late-type Peculiar Am Ap/Bp Oscillating Barium Carbon CH Extreme helium Lambda Boötis Lead Mercury-manganese S Shell Technetium Remnants White dwarf Black dwarf Helium planet Neutron star Pulsar Magnetar Stellar black hole Compact star Quark Exotic Stellar core: EF Eridani B Failed and theoretical stars Substellar object Brown dwarf Sub-brown dwarf Planetar Boson star Dark-matter star Quasistar Thorne–Żytkow object Iron star Nucleosynthesis Alpha process Triple-alpha process Proton–proton chain Helium flash CNO cycle Lithium burning Carbon burning Neon burning Oxygen burning Silicon burning S-process R-process Fusor Nova Remnants Structure Core Convection zone Microturbulence Oscillations Radiation zone Photosphere Starspot Chromosphere Corona Stellar wind Bubble Asteroseismology Eddington luminosity Kelvin–Helmholtz mechanism Properties Designation Dynamics Effective temperature Kinematics Magnetic field Magnitude Absolute Mass Metallicity Rotation UBV color Variability Star systems Binary Contact Common envelope Multiple Accretion disc Planetary system Earth's Solar System Earth-centric observation of Pole star Circumpolar star Magnitude Apparent Photographic Color Radial velocity Proper motion Parallax Photometric-standard star Lists Star names Arabic names Chinese names Most massive Least massive Largest Brightest Historical Most luminous Nearest Nearest bright Stars with exoplanets Brown dwarfs Planetary nebulae Novae Notable supernovae Supernova remnants Supernova candidates Timeline of stellar astronomy Related articles Planet Star cluster Association Open cluster Globular cluster Galaxy Supercluster Helioseismology Guest star Constellation Asterism Gravity Intergalactic star Infrared dark cloud Star portal

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Dansk (Danish)
n. - størrelse, kæmpe-

idioms:

• order of magnitude    størrelsesorden

Nederlands (Dutch)
grootte, grootheid, hoeveelheid, belangrijkheid/ kwaliteit etc., helderheid

Français (French)
n. - ampleur, (Astron) magnitude

idioms:

• order of magnitude    ordre de grandeur

Deutsch (German)
n. - Größe, Ausmaß, Bedeutung

idioms:

• order of magnitude    Größenordnung

Ελληνική (Greek)
n. - μέγεθος, σημασία, σπουδαιότητα

idioms:

• order of magnitude    σειρά μεγέθους

Italiano (Italian)
dimensione, grandezza

idioms:

• order of magnitude    ordine di grandezza

Português (Portuguese)
n. - dimensão (f), valor (m), grandeza (f)

idioms:

• order of magnitude    ordem de grandeza (f)

Русский (Russian)
величина, важность

idioms:

• order of magnitude    порядок величин

Español (Spanish)
n. - magnitud, envergadura

idioms:

• order of magnitude    orden de magnitud, envergadura

Svenska (Swedish)
n. - storlek, omfattning, vikt, magnitud, storhet (matem.)

中文（简体）(Chinese (Simplified))
大小, 光度, 重要

idioms:

• order of magnitude    订单额度

中文（繁體）(Chinese (Traditional))
n. - 大小, 光度, 重要

idioms:

• order of magnitude    訂單額度

한국어 (Korean)
n. - 크기, 규모, 방대, 중요성, 등급

日本語 (Japanese)
n. - 大きさ, 重要性, 偉大さ, マグニチュード, 光度

العربيه (Arabic)
‏(الاسم) عظم, كبر, حجم, أهميه‏

עברית (Hebrew)
n. - ‮גודל, חשיבות, ערך, כבוד (של כוכב)‬

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