Apparent magnitude

For a more detailed discussion of the history of the magnitude system, seeMagnitude (astronomy).

Asteroid65 Cybeleand two stars, with their magnitudes labeled

Apparent magnitude(m) is a measure of thebrightnessof astaror otherastronomical object.An object's apparent magnitude depends on its intrinsicluminosity,its distance, and anyextinctionof the object's light caused byinterstellar dustalong theline of sightto the observer.

The wordmagnitudein astronomy, unless stated otherwise, usually refers to a celestial object's apparent magnitude. The magnitude scale dates to before the ancientRoman astronomerClaudius Ptolemy,whosestar catalogpopularized the system by listing stars from1st magnitude(brightest) to 6th magnitude (dimmest).The modern scale was mathematically defined in a way to closely match this historical system.

The scale is reverselogarithmic:the brighter an object is, the lower itsmagnitudenumber. A difference of 1.0 in magnitude corresponds to a brightness ratio of${\sqrt[{5}]{100}}$,or about 2.512. For example, a star of magnitude 2.0 is 2.512 times as bright as a star of magnitude 3.0, 6.31 times as bright as a star of magnitude 4.0, and 100 times as bright as one of magnitude 7.0.

The brightest astronomical objects have negative apparent magnitudes: for example,Venusat −4.2 orSiriusat −1.46. The faintest stars visible with thenaked eyeon the darkest night have apparent magnitudes of about +6.5, though this varies depending on a person'seyesightand withaltitudeand atmospheric conditions.The apparent magnitudes of known objects range from the Sun at −26.832 to objects in deepHubble Space Telescopeimages of magnitude +31.5.

The measurement of apparent magnitude is calledphotometry.Photometric measurements are made in theultraviolet,visible,orinfraredwavelength bandsusing standardpassbandfilters belonging tophotometric systemssuch as theUBV systemor theStrömgrenuvbyβsystem.Measurement in the V-band may be referred to as theapparent visual magnitude.

Absolute magnitudeis a related quantity which measures theluminositythat a celestial object emits, rather than its apparent brightness when observed, and is expressed on the same reverse logarithmic scale. Absolute magnitude is defined as the apparent magnitude that a star or object would have if it were observed from a distance of 10parsecs(33 light-years; 3.1×10¹⁴kilometres; 1.9×10¹⁴miles). Therefore, it is of greater use instellar astrophysicssince it refers to a property of a star regardless of how close it is to Earth. But inobservational astronomyand popularstargazing,references to "magnitude" are understood to mean apparent magnitude.

Amateur astronomerscommonly express the darkness of the sky in terms oflimiting magnitude,i.e. the apparent magnitude of the faintest star they can see with the naked eye. This can be useful as a way of monitoring the spread oflight pollution.

Apparent magnitude is really a measure ofilluminance,which can also be measured in photometric units such aslux.

History

Visible to typical human eye	Apparent magnitude	Bright- ness relative toVega	Number of stars (other than theSun) brighter than apparent magnitude in the night sky
Yes	−1.0	251%	1 (Sirius)
	00.0	100%	4 (Vega,Canopus,Alpha Centauri, Arcturus)
	01.0	40%	15
	02.0	16%	48
	03.0	6.3%	171
	04.0	2.5%	513
	05.0	1.0%	1602
	06.0	0.4%	4800
	06.5	0.25%	9100
No	07.0	0.16%	14000
	08.0	0.063%	42000
	09.0	0.025%	121000
	10.0	0.010%	340000

The scale used to indicate magnitude originates in theHellenisticpractice of dividing stars visible to the naked eye into sixmagnitudes.Thebrightest starsin the night sky were said to be offirst magnitude(m= 1), whereas the faintest were of sixth magnitude (m= 6), which is the limit ofhumanvisual perception(without the aid of atelescope). Each grade of magnitude was considered twice the brightness of the following grade (alogarithmic scale), although that ratio was subjective as nophotodetectorsexisted. This rather crude scale for the brightness of stars was popularized byPtolemyin hisAlmagestand is generally believed to have originated withHipparchus.This cannot be proved or disproved because Hipparchus's original star catalogue is lost. The only preserved text by Hipparchus himself (a commentary to Aratus) clearly documents that he did not have a system to describe brightness with numbers: He always uses terms like "big" or "small", "bright" or "faint" or even descriptions such as "visible at full moon".

In 1856,Norman Robert Pogsonformalized the system by defining a first magnitude star as a star that is 100 times as bright as a sixth-magnitude star, thereby establishing the logarithmic scale still in use today. This implies that a star of magnitudemis about 2.512 times as bright as a star of magnitudem+ 1.This figure, thefifth root of 100,became known as Pogson's Ratio.The1884 Harvard Photometryand 1886Potsdamer Duchmusterungstar catalogs popularized Pogson's ratio, and eventually it became a de facto standard in modern astronomy to describe differences in brightness.

Defining and calibrating what magnitude 0.0 means is difficult, and different types of measurements which detect different kinds of light (possibly by using filters) have different zero points. Pogson's original 1856 paper defined magnitude 6.0 to be the faintest star the unaided eye can see,but the true limit for faintest possible visible star varies depending on the atmosphere and how high a star is in the sky. TheHarvard Photometryused an average of 100 stars close to Polaris to define magnitude 5.0.Later, the Johnson UVB photometric system defined multiple types of photometric measurements with different filters, where magnitude 0.0 for each filter is defined to be the average of six stars with the same spectral type as Vega. This was done so thecolor indexof these stars would be 0.Although this system is often called "Vega normalized", Vega is slightly dimmer than the six-star average used to define magnitude 0.0, meaning Vega's magnitude is normalized to 0.03 by definition.

Limiting Magnitudes for Visual Observation at High Magnification

Telescope aperture (mm)	Limiting Magnitude
35	11.3
60	12.3
102	13.3
152	14.1
203	14.7
305	15.4
406	15.7
508	16.4

With the modern magnitude systems, brightness is described using Pogson's ratio. In practice magnitude numbers rarely go above 30 before stars become too faint to detect. While Vega is close to magnitude 0, there are four brighter stars in the night sky at visible wavelengths (and more at infrared wavelengths) as well as the bright planets Venus, Mars, and Jupiter, and since brighter means smaller magnitude, these must be described bynegativemagnitudes. For example,Sirius,the brightest star of thecelestial sphere,has a magnitude of −1.4 in the visible. Negative magnitudes for other very bright astronomical objects can be found in thetablebelow.

Astronomers have developed other photometric zero point systems as alternatives to Vega normalized systems. The most widely used is theAB magnitudesystem,in which photometric zero points are based on a hypothetical reference spectrum having constantflux per unit frequency interval,rather than using a stellar spectrum or blackbody curve as the reference. The AB magnitude zero point is defined such that an object's AB and Vega-based magnitudes will be approximately equal in the V filter band. However, the AB magnitude system is defined assuming an idealized detector measuring only one wavelength of light, while real detectors accept energy from a range of wavelengths.

Measurement

Main article:Photometry (astronomy)

Precision measurement of magnitude (photometry) requires calibration of the photographic or (usually) electronic detection apparatus. This generally involves contemporaneous observation, under identical conditions, of standard stars whose magnitude using that spectral filter is accurately known. Moreover, as the amount of light actually received by a telescope is reduced due to transmission through theEarth's atmosphere,theairmassesof the target andcalibration starsmust be taken into account. Typically one would observe a few different stars of known magnitude which are sufficiently similar. Calibrator stars close in the sky to the target are favoured (to avoid large differences in the atmospheric paths). If those stars have somewhat differentzenith angles(altitudes) then a correction factor as a function of airmass can be derived andappliedto the airmass at the target's position. Such calibration obtains the brightness as would be observed from above the atmosphere, where apparent magnitude is defined.

The apparent magnitude scale in astronomy reflects the received power of stars and not their amplitude. Newcomers should consider using the relative brightness measure in astrophotography to adjust exposure times between stars. Apparent magnitude also integrates over the entire object, regardless of its focus, and this needs to be taken into account when scaling exposure times for objects with significant apparent size, like the Sun, Moon and planets. For example, directly scaling the exposure time from the Moon to the Sun works because they are approximately the same size in the sky. However, scaling the exposure from the Moon to Saturn would result in an overexposure if the image of Saturn takes up a smaller area on your sensor than the Moon did (at the same magnification, or more generally, f/#).

Calculations

Image of30 Doradustaken byESO'sVISTA.Thisnebulahas a visual magnitude of 8.

Graph of relative brightness versus magnitude

The dimmer an object appears, the higher the numerical value given to its magnitude, with a difference of 5 magnitudes corresponding to a brightness factor of exactly 100. Therefore, the magnitudem,in thespectral bandx,would be given by $$m_{x}=-5\log _{100}\left({\frac {F_{x}}{F_{x,0}}}\right),$$ which is more commonly expressed in terms ofcommon (base-10) logarithmsas $$m_{x}=-2.5\log _{10}\left({\frac {F_{x}}{F_{x,0}}}\right),$$ whereF_xis the observedirradianceusing spectral filterx,andF_x,0is the reference flux (zero-point) for thatphotometric filter.Since an increase of 5 magnitudes corresponds to a decrease in brightness by a factor of exactly 100, each magnitude increase implies a decrease in brightness by the factor${\sqrt[{5}]{100}}\approx 2.512$(Pogson's ratio). Inverting the above formula, a magnitude differencem₁−m₂= Δmimplies a brightness factor of $${\frac {F_{2}}{F_{1}}}=100^{\frac {\Delta m}{5}}=10^{0.4\Delta m}\approx 2.512^{\Delta m}.$$

Example: Sun and Moon

What is the ratio in brightness between theSunand the fullMoon?

The apparent magnitude of the Sun is −26.832(brighter), and the mean magnitude of thefull moonis −12.74(dimmer).

Difference in magnitude: $$x=m_{1}-m_{2}=(-12.74)-(-26.832)=14.09.$$

Brightness factor: $$v_{b}=10^{0.4x}=10^{0.4\times 14.09}\approx 432\,513.$$

The Sun appears to be approximately400000times as bright as the full Moon.

Magnitude addition

Sometimes one might wish to add brightness. For example,photometryon closely separateddouble starsmay only be able to produce a measurement of their combined light output. To find the combined magnitude of that double star knowing only the magnitudes of the individual components, this can be done by adding the brightness (in linear units) corresponding to each magnitude. $$10^{-m_{f}\times 0.4}=10^{-m_{1}\times 0.4}+10^{-m_{2}\times 0.4}.$$

Solving for$m_{f}$yields $$m_{f}=-2.5\log _{10}\left(10^{-m_{1}\times 0.4}+10^{-m_{2}\times 0.4}\right),$$ wherem_fis the resulting magnitude after adding the brightnesses referred to bym₁andm₂.

Apparent bolometric magnitude

While magnitude generally refers to a measurement in a particular filter band corresponding to some range of wavelengths, the apparent or absolutebolometric magnitude(m_bol) is a measure of an object's apparent or absolute brightness integrated over all wavelengths of the electromagnetic spectrum (also known as the object'sirradianceor power, respectively). The zero point of the apparent bolometric magnitude scale is based on the definition that an apparent bolometric magnitude of 0 mag is equivalent to a received irradiance of 2.518×10⁻⁸wattsper square metre (W·m⁻²).

Absolute magnitude

Main article:Absolute magnitude

While apparent magnitude is a measure of the brightness of an object as seen by a particular observer, absolute magnitude is a measure of theintrinsicbrightness of an object. Flux decreases with distance according to aninverse-square law,so the apparent magnitude of a star depends on both its absolute brightness and its distance (and any extinction). For example, a star at one distance will have the same apparent magnitude as a star four times as bright at twice that distance. In contrast, the intrinsic brightness of an astronomical object, does not depend on the distance of the observer or anyextinction.

The absolute magnitudeM,of a star or astronomical object is defined as the apparent magnitude it would have as seen from a distance of 10 parsecs (33ly). The absolute magnitude of the Sun is 4.83 in the V band (visual), 4.68 in theGaia satellite'sG band (green) and 5.48 in the B band (blue).

In the case of a planet or asteroid, the absolute magnitudeHrather means the apparent magnitude it would have if it were 1astronomical unit(150,000,000 km) from both the observer and the Sun, and fully illuminated at maximum opposition (a configuration that is only theoretically achievable, with the observer situated on the surface of the Sun).

Standard reference values

Standard apparent magnitudes and fluxes for typical bands

Band	λ (μm)	⁠Δλ/λ⁠ (FWHM)	Flux atm= 0,Fx,0
			Jy	10−20erg/(s·cm2·Hz)
U	0.36	0.15	1810	1.81
B	0.44	0.22	4260	4.26
V	0.55	0.16	3640	3.64
R	0.64	0.23	3080	3.08
I	0.79	0.19	2550	2.55
J	1.26	0.16	1600	1.60
H	1.60	0.23	1080	1.08
K	2.22	0.23	0670	0.67
L	3.50
g	0.52	0.14	3730	3.73
r	0.67	0.14	4490	4.49
i	0.79	0.16	4760	4.76
z	0.91	0.13	4810	4.81

The magnitude scale is a reverse logarithmic scale. A common misconception is that the logarithmic nature of the scale is because thehuman eyeitself has a logarithmic response. In Pogson's time this was thought to be true (seeWeber–Fechner law), but it is now believed that the response is apower law(seeStevens' power law).

Magnitude is complicated by the fact that light is notmonochromatic.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 theUBV systemis widely used, in which the magnitude is measured in three different wavelength bands: U (centred at about 350 nm, in the nearultraviolet), 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 human eye. When an apparent magnitude is discussed without further qualification, the V magnitude is generally understood.

Because cooler stars, such asred giantsandred dwarfs,emit little energy in the blue and UV regions of the spectrum, their power is often under-represented by the UBV scale. Indeed, someL and T classstars have an estimated magnitude of well over 100, because they emit extremely little visible light, but are strongest ininfrared.

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 bluesupergiantRigeland the red supergiantBetelgeuseirregular variable star (at maximum) are reversed compared to what human eyes perceive, because this archaic film is more sensitive to blue light than it is to red light. Magnitudes obtained from this method are known asphotographic magnitudes,and are now considered obsolete.

For objects within theMilky Waywith a given absolute magnitude, 5 is added to the apparent magnitude for every tenfold increase in the distance to the object. For objects at very great distances (far beyond the Milky Way), this relationship must beadjusted for redshiftsand fornon-Euclideandistance measures due togeneral relativity.

For planets and other Solar System bodies, the apparent magnitude is derived from itsphase curveand the distances to the Sun and observer.

List of apparent magnitudes

See also:List of brightest stars

Some of the listed magnitudes are approximate. Telescope sensitivity depends on observing time, optical bandpass, and interfering light fromscatteringandairglow.

Apparent visual magnitudes of celestial objects

Apparent magnitude (V)	Object	Seen from...	Notes
−67.57	gamma-ray burstGRB 080319B	seen from 1AUaway	would be over2×1016(20 quadrillion) times as bright as the Sun when seen from the Earth
−41.39	starCygnus OB2-12	seen from 1 AU away
−40.67	starM33-013406.63	seen from 1 AU away
−40.17	starEta CarinaeA	seen from 1 AU away
−40.07	starZeta1Scorpii	seen from 1 AU away
−39.66	starR136a1	seen from 1 AU away
−39.47	starP Cygni	seen from 1 AU away
−38.00	starRigel	seen from 1 AU away	would be seen as a large, very bright bluish disk of 35° apparent diameter
−30.30	starSiriusA	seen from 1 AU away
−29.30	starSun	seen fromMercuryatperihelion
−27.40	star Sun	seen fromVenusat perihelion
−26.832	star Sun	seen fromEarth	about 400,000 times as bright as mean full Moon
−25.60	star Sun	seen fromMarsataphelion
−25.00	Minimum brightness that causes the typical eye slight pain to look at
−23.00	star Sun	seen fromJupiterat aphelion
−21.70	star Sun	seen fromSaturnat aphelion
−21.00	star Sun	seen from Earth on an overcast midday	measuring about 1000 lux
−20.20	star Sun	seen fromUranusat aphelion
−19.30	star Sun	seen fromNeptune
−19.00	star Sun	seen from Earth on a very strongly overcast midday	measuring about 100 lux
−18.20	star Sun	seen fromPlutoat aphelion
−17.70	planet Earth	seen fully illuminated asearthlightfrom theMoon
−16.70	star Sun	seen fromErisat aphelion
−16.00	star Sun	astwilighton Earth	measuring about 10 lux
−14.20	An illumination level of 1lux
−12.60	full moon	seen from Earth at perihelion	maximum brightness of perigee + perihelion + full Moon (~0.267 lux; mean distance value is −12.74,though values are about 0.18 magnitude brighter when including theopposition effect)
−12.40	Betelgeuse(when supernova)	seen from Earth when it goes supernova
−11.20	star Sun	seen fromSednaat aphelion
−10.00	CometIkeya–Seki(1965)	seen from Earth	which was the brightestKreutz Sungrazerof modern times
−9.50	Iridium (satellite) flare	seen from Earth	maximum brightness
−9 to −10	Phobos (moon)	seen from Mars	maximum brightness
−7.50	supernova of 1006	seen from Earth	the brightest stellar event in recorded history (7200 light-years away)
−6.80	Alpha Centauri A	seen fromProxima Centauri b
−6.00	The totalintegrated magnitudeof thenight sky(incl.airglow)	seen from Earth	measuring about 0.002 lux
−6.00	Crab Supernova of 1054	seen from Earth	(6500 light-years away)
−5.90	International Space Station	seen from Earth	when the ISS is at itsperigeeand fully lit by the Sun
−4.92	planet Venus	seen from Earth	maximum brightnesswhen illuminated as a crescent
−4.14	planet Venus	seen from Earth	mean brightness
−4	Faintest objects observable during the day with naked eye when Sun is high.An astronomical object casts human-visible shadows when its apparent magnitude is equal to or lower than −4
−3.99	starEpsilon Canis Majoris	seen from Earth	maximum brightness of 4.7 million years ago, the historicalbrightest starof thelast and next five million years.
−3.69	Moon	lit by earthlight, reflectingearthshineseen from Earth (maximum)
−2.98	planet Venus	seen from Earth	minimum brightness when it is on the far side of the Sun
−2.94	planet Jupiter	seen from Earth	maximum brightness
−2.94	planet Mars	seen from Earth	maximum brightness
−2.5	Faintest objects visible during the day with naked eye when Sun is less than 10° above the horizon
−2.50	new moon	seen from Earth	minimum brightness
−2.50	planet Earth	seen from Mars	maximum brightness
−2.48	planet Mercury	seen from Earth	maximum brightness atsuperior conjunction(unlike Venus, Mercury is at its brightest when on the far side of the Sun, the reason being their different phase curves)
−2.20	planet Jupiter	seen from Earth	mean brightness
−1.66	planet Jupiter	seen from Earth	minimum brightness
−1.47	star system Sirius	seen from Earth	Brightest star except for the Sun at visible wavelengths
−0.83	starEta Carinae	seen from Earth	apparent brightness as asupernova impostorin April 1843
−0.72	starCanopus	seen from Earth	2nd brightest star in night sky
−0.55	planet Saturn	seen from Earth	maximum brightness near opposition and perihelion when the rings are angled toward Earth
−0.3	Halley's comet	seen from Earth	Expected apparent magnitude at 2061 passage
−0.27	star systemAlpha CentauriAB	seen from Earth	Combined magnitude (3rd brightest star in night sky)
−0.04	starArcturus	seen from Earth	4th brightest star to the naked eye
−0.01	star Alpha Centauri A	seen from Earth	4th brightestindividualstar visible telescopically in the night sky
+0.03	starVega	seen from Earth	originally chosen as a definition of the zero point
+0.23	planet Mercury	seen from Earth	mean brightness
+0.46	star Sun	seen from Alpha Centauri
+0.46	planet Saturn	seen from Earth	mean brightness
+0.71	planet Mars	seen from Earth	mean brightness
+0.90	Moon	seen from Mars	maximum brightness
+1.17	planet Saturn	seen from Earth	minimum brightness
+1.33	star Alpha Centauri B	seen from Earth
+1.86	planet Mars	seen from Earth	minimum brightness
+1.98	starPolaris	seen from Earth	mean brightness
+3.03	supernovaSN 1987A	seen from Earth	in theLarge Magellanic Cloud(160,000 light-years away)
+3 to +4	Faintest stars visible in an urban neighborhood with naked eye
+3.44	Andromeda Galaxy	seen from Earth	M31
+4	Orion Nebula	seen from Earth	M42
+4.38	moonGanymede	seen from Earth	maximum brightness(moon of Jupiter and the largest moon in the Solar System)
+4.50	open clusterM41	seen from Earth	an open cluster that may have been seen byAristotle
+4.5	Sagittarius Dwarf Spheroidal Galaxy	seen from Earth
+5.20	asteroidVesta	seen from Earth	maximum brightness
+5.38	planet Uranus	seen from Earth	maximum brightness(Uranus comes to perihelion in 2050)
+5.68	planet Uranus	seen from Earth	mean brightness
+5.72	spiral galaxyM33	seen from Earth	which is used as a test fornaked eyeseeing under dark skies
+5.8	gamma-ray burstGRB 080319B	seen from Earth	Peak visual magnitude (the "Clarke Event" ) seen on Earth on 19 March 2008 from a distance of 7.5 billion light-years.
+6.03	planet Uranus	seen from Earth	minimum brightness
+6.49	asteroidPallas	seen from Earth	maximum brightness
+6.5	Approximate limit ofstarsobserved by ameannaked eye observer under very good conditions. There are about 9,500 stars visible to mag 6.5.
+6.64	dwarf planetCeres	seen from Earth	maximum brightness
+6.75	asteroidIris	seen from Earth	maximum brightness
+6.90	spiral galaxyM81	seen from Earth	This is an extreme naked-eye target that pushes human eyesight and the Bortle scale to the limit
+7.25	planet Mercury	seen from Earth	minimum brightness
+7.67	planet Neptune	seen from Earth	maximum brightness(Neptune comes to perihelion in 2042)
+7.78	planet Neptune	seen from Earth	mean brightness
+8.00	planet Neptune	seen from Earth	minimum brightness
+8	Extreme naked-eye limit, Class 1 onBortle scale,the darkest skies available on Earth.
+8.10	moonTitan	seen from Earth	maximum brightness; largest moon of Saturn;mean opposition magnitude 8.4
+8.29	starUY Scuti	seen from Earth	Maximum brightness; one of largest known stars by radius
+8.94	asteroid10 Hygiea	seen from Earth	maximum brightness
+9.50	Faintest objects visible using common 7×50binocularsunder typical conditions
+10	Apollo 8CSMin orbit around the Moon	seen from Earth	calculated (Liemohn)
+10.20	moonIapetus	seen from Earth	maximum brightness,brightest when west of Saturn and takes 40 days to switch sides
+11.05	starProxima Centauri	seen from Earth	closest star
+11.8	moonPhobos	seen from Earth	Maximum brightness; brighter moon of Mars
+12.23	starR136a1	seen from Earth	Most luminous and massive star known
+12.89	moonDeimos	seen from Earth	Maximum brightness
+12.91	quasar3C 273	seen from Earth	brightest (luminosity distanceof 2.4 billionlight-years)
+13.42	moonTriton	seen from Earth	Maximum brightness
+13.65	dwarf planetPluto	seen from Earth	maximum brightness,725 times fainter than magnitude 6.5 naked eye skies
+13.9	moonTitania	seen from Earth	Maximum brightness; brightest moon of Uranus
+14.1	starWR 102	seen from Earth	Hottest known star
+15.4	centaurChiron	seen from Earth	maximum brightness
+15.55	moonCharon	seen from Earth	maximum brightness (the largest moon of Pluto)
+16.8	dwarf planetMakemake	seen from Earth	Currentoppositionbrightness
+17.27	dwarf planetHaumea	seen from Earth	Current opposition brightness
+18.7	dwarf planetEris	seen from Earth	Current opposition brightness
+19.5	Faintest objects observable with theCatalina Sky Survey0.7-meter telescope using a 30-second exposureand also the approximatelimiting magnitudeofAsteroid Terrestrial-impact Last Alert System(ATLAS)
+20.7	moonCallirrhoe	seen from Earth	(small ≈8 km satellite of Jupiter)
+22	Faintest objects observable in visible light with a 600 mm (24″)Ritchey-Chrétien telescopewith 30 minutes of stacked images (6 subframes at 5 minutes each) using aCCD detector
+22.8	Luhman 16	seen from Earth	Closestbrown dwarfs(Luhman 16A=23.25, Luhman 16B=24.07)
+22.91	moonHydra	seen from Earth	maximum brightness of Pluto's moon
+23.38	moonNix	seen from Earth	maximum brightness of Pluto's moon
+24	Faintest objects observable with thePan-STARRS1.8-meter telescope using a 60-second exposureThis is currently the limiting magnitude of automated allskyastronomical surveys.
+25.0	moonFenrir	seen from Earth	(small ≈4 km satellite of Saturn)
+25.3	Trans-Neptunian object2018 AG37	seen from Earth	Furthest known observable object in the Solar System about 132 AU (19.7 billion km) from the Sun
+26.2	Trans-Neptunian object2015 TH367	seen from Earth	200 km sized object about 90 AU (13 billion km) from the Sun and about 75 million times fainter than what can be seen with the naked eye.
+27.7	Faintest objects observable with a single 8-meter class ground-based telescope such as theSubaru Telescopein a 10-hour image
+28.2	Halley's Comet	seen from Earth (2003)	in 2003 when it was 28 AU (4.2 billion km) from the Sun, imaged using 3 of 4 synchronised individual scopes in theESO'sVery Large Telescopearray using a total exposure time of about 9 hours
+28.4	asteroid2003 BH91	seen from Earth orbit	observed magnitude of ≈15-kilometerKuiper beltobject seen by theHubble Space Telescope(HST) in 2003, dimmest known directly observed asteroid.
+29.4	JADES-GS-z13-0	seen from Earth	Discovered by theJames Webb Space Telescope.One of the furthest objects discovered.
+31.5	Faintest objects observable in visible light withHubble Space Telescopevia theEXtreme Deep Fieldwith ≈23 days of exposure time collected over 10 years
+34	Faintest objects observable in visible light withJames Webb Space Telescope
+35	unnamed asteroid	seen from Earth orbit	expected magnitude of dimmest known asteroid, a 950-meter Kuiper belt object discovered (by the HST)passing in front of a starin 2009.
+35	starLBV 1806−20	seen from Earth	a luminous blue variable star, expected magnitude at visible wavelengths due tointerstellar extinction

See also

• Angular diameter
• Distance modulus
• List of nearest bright stars
• List of nearest stars
• Luminosity
• Surface brightness

External links

• "The astronomical magnitude scale".International Comet Quarterly.