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Bardula is a pseudonym created by a Belgian artist who currently lives and works in France.
Bardula creates luminous paintings including the hypnotic paintings "Blue Interferences" and "Blue ice" (see Figures 1 and 2 above).
Sources :
Light ZOOM Lumière.
Bardula.
Here is a selection of the best motion illusions (see above Figure 1 cf [GomboDigital], Figures 2 to 5 cf [Sélection.ca] and Figure 6 cf [Akiyoshi Kitaoka]) :
1. Rotating vortex (Vectordivider image via Getty Images)
2. Rotating spirals (Vectordivider image via Getty Images)
3. Mesmerizing effect (Mark Grenier image via Shutterstock)
4. Scroll (Guten Tag Vector image via Shutterstock)
5. Glitter Grid (Mark image via Shutterstock)
6. "Expanding pupils" (Image from Akiyoshi Kitaoka)
Sources :
Sélection du Reader's Digest (Canada) - 24 illusions d'optique complètement étourdissantes.
GomboDigital - 5 illusions d'optique qui vont vous scotcher/.
Akiyoshi Kitaoka - Anomalous motion illusions 35.
The Author of this site has made four wind sculptures installed in his garden in Berrac (Gers).
Description :
Design :
These sculptures are made with recycled products (aluminum rails for thermal insulation frame, PVC camping bowls, plastic jerrycan sides, tennis ball, rebar, etc.).
All moving parts are carried on ball bearings.
All the fixed elements are assembled by stainless steel screws.
The sculptures are fixed to the ground by a vertical mast (galvanized steel fence post or old steel water pipe).
Pierre Luu is a French sculptor who has created sculptures with unpredictable movements, driven by wind or water, including the "wind turbine with random motion" (see Figures above, and video "Mobile eolien art cinétique" in [Pierre Luu]).
Description :
Figure 1 above : general view (cf [Art et Eau]).
Figure 2 above : zoom on blades twist angle (video clip 0:12).
Figure 3 above : zoom on blades lenght (video clip 0:22).
The "wind turbine with random motion" is made up of 5 moving parts in unstable equilibrium (cf [Pierre Luu - Quelque chose ne tourne pas rond][Art et Eau - Quelque chose ne tourne pas rond]).
The balance is all the more unstable as there is no weather vane to orient the sculpture in the wind direction. The blue ball is aesthetic and symbolizes the Earth (cf my email of March 5, 2023 from Pierre Luu to Régis Petit).
The two blades are of different size with a secondary rotation nested within the primary rotation (cf [Pierre Luu - Eolide].
The sculpture slowly comes to life and changes shape thanks to the wind action. The movement is maintained by inertia due to the balance of the masses (cf [Art et Eau - Quelque chose ne tourne pas rond]).
The sculpture unfolds in an enigmatic choreography and only finds temporary stability when the blades reach a certain speed (cf [Pierre Luu - Quelque chose ne tourne pas rond]).
Design :
The whole is designed in a search for balance between the masses, the gravity centers, the surfaces exposed to the wind and the relative angles of the surfaces (cf [Pierre Luu - Quelque chose ne tourne pas rond]).
The mobile elements are fixed by ball bearings for all sculptures in project version (cf email of March 7, 2023 from Pierre Luu to Régis Petit). This combination allows fluid rotations and movements even in light winds (cf [Pierre Luu - Fragments mobile éolien).
Material : stainless steel and composite materials (cf [Art et Eau - Quelque chose ne tourne pas rond]).
Height : 3 m 50 (cf [Art et Eau - Quelque chose ne tourne pas rond]).
Sources :
Pierre Luu - Mobile eolien art cinétique (YouTube, 01:57).
Pierre Luu - Un art en mouvement - Sculptures éoliennes et mobiles.
Pierre Luu - Un art en mouvement - Quelque chose ne tourne pas rond.
Pierre Luu - Un art en mouvement - Fragments mobile éolien.
Pierre Luu - Un art en mouvement - Eolide.
Pierre Luu - Un art en mouvement - Solaris : sculpture éolienne et solaire autonome en énergie.
Art et Eau - Ellipse, quelque chose ne tourne pas rond.
Jeff Kahn is an American sculptor who created kinetic sculptures, titled "Invisible Forces", from aluminum and stainless steel.
These sculptures explore balance and gravity and how almost imperceptible air currents interact with them. They are extremely sensitive to the surrounding environment (light breezes, sun heat, weight of the morning dew). See above Figures 1, 2 and 3 showing three particular sculptures : "Astrolabe", "Naked Alien" and "I Ching".
Jeff Kahn's studio is located in Lenhartsville, Pennsylvania, USA.
Sources :
Jeff Kahn - Bio.
Jeff Kahn - Catalog.
Jeff Kahn - Videos.
Anthony Howe is an American sculptor who has created hypnotic mobile sculptures including "Di-Octo" in 2014 (see Figures 1, 2 and 3 above, and "Di-Octo" video in [Anthony Howe] and [KULTT]).
Anthony Howe currently lives in Eastsound, Orcas Island, San Juan County, Washington State (USA).
Description :
Di-Octo is a half-octopus, half-star, wind-driven and near-silent mobile sculpture.
The original Di-Octo, designed and made by Anthony Howe, has been industrialized in two identical copies by Show Canada Inc (Laval steelworks in Quebec) as follows (cf email of March 10, 2023 from David Boulay (Show Canada Inc) to Régis Petit) :
Design :
Di-Octo is 8 meters high, 3 meters in diameter, weighs 725 kilograms and requires only 2 km/h of wind for its moving parts to activate (cf [Concordia University]).
Di-Octo is composed of 36 arms each carrying 16 very thin steel domes and rotating around a vertical circular ring. The inter-arm connections are of the intermediate wheel type with drive fingers. See detail in Figure 3 above (cf [Show Canada]).
The arms always turn in the same direction, regardless of the wind direction. This is due to the domes shape (cf email of March 19, 2023 from David Boulay to Régis Petit).
Di-Octo is entirely made of 316 stainless steel, which gives it better corrosion resistance as well as non-magnetic properties (cf [Show Canada]).
Other similar sculptures :
Anthony Howe designed and made other sculptures similar to Di-Octo (cf [Anthony Howe, https://www.howeart.net/about]) :
Sources :
Anthony Howe.
Anthony Howe - Shindahiku (Fern pull).
The DC Blike Blogger - Shindahiku (Fern Pull).
KULTT - Les sculptures hypnotiques d'Anthony Howe.
Anthony Howe - Di-Octo (Youtube 1:10).
Anthony Howe - Di-Octo (long version) (Youtube 1:33).
Université Concordia - Di-Octo : captivant, cinétique et unique.
Show Canada.
JuanG3D : Di-Octo 3D Model.
What's on - Check out these alien-esque kinetic sculptures in Dubai.
UAE - Famous American artist brings kinetic sculptures to Dubai.
reddit - "Octo II", Anthony Howe, stainless steel, 2013..
Jennifer Townley is a Dutch artist who has created hypnotic mobile sculptures including "Asinas" in 2015 (see Figure 1 above, and video "Asinas").
When viewed at a standstill from the front, it looks like a double helix like the usual representation of DNA.
Description (cf [Jennifer Townley]) :
"Asinas" is a mobile sculpture composed of two helixes that intertwine and slide into each other, producing a fluid and natural movement.
The two helixes slowly rotate in opposite directions and at slightly different speeds, gradually transforming the sculpture.
A demonstration of how this sculpture works helps to better understand this description (see video "Asinas Working Demonstration" in [Amogh Jadhav] and video "SolidWorks Mechanical Sculpture" in [tecnoloxia.org]).
Design :
The sixty-five white wooden bricks that form the two helixes increase in size towards the middle of the sculpture, giving it a conical shape.
Each brick has the shape of a Z with 90 degree angles. The bricks of a helix are fixed on the rotation axis. The bricks of the other helix are connected to one another through small spacers (see Figure 2 above from [Amogh Jadhav]).
The bricks are made from painted wood. The frame is made of steel as well as all the parts connecting the gears to their axes, the bearings to the frame, etc.
Then there are all the other parts : an electric motor, heavy steel spur gears and sprockets, two belts and lots of bearings (cf [The Plus Paper]).
Sources :
Asinas - Jennifer Townley - 2015 - Kinetic art (Youtube 2:31).
Jennifer Townley - Asinas.
L'Usine Nouvelle - Hypnotiques, ces sculptures cinétiques vous étonneront.
Amogh Jadhav - Asinas.
Amogh Jadhav - Asinas Working Demonstration (Youtube 2:14).
tecnoloxia.org - As esculturas cinéticas de Jennifer Townley.
MadCadSkills : Jennifer Townley - SolidWorks Mechanical Sculpture (Youtube 3:43).
The Plus Paper - Asinas : Fluent Movement ( http://www.thepluspaper.com/2015/03/23/asinas-fluent-movement/ ).
Theo Jansen is a Dutch sculptor who in 1991 created strange creatures including the walking robot (see Figures 1 and 2 above).
Working :
This walking robot is a mechanism with very light legs which can move on a horizontal plane under the wind action or on an inclined plane under the action of its own weight (see video cf [Jansen, Plaudens Vela]).
The only actuator in the robot is a central crankshaft making the connection between the legs and the robot body (see red while on Figure 2, and also [Exergia]).
For a robot with three pairs of legs, the crankshaft has three cranks offset successively by 120° to have a constant movement of the robot during the propulsion phase (see Figure 2).
Body description :
The robot body consists of a horizontal platform (length 2a) and vertical fixed supports (length l) carrying the crankshaft (eccentricity m). See Figure 3 above.
The double length (a) of the platform is calculated to ensure non-collision between the front legs and the rear legs.
The length (l) of the supports can be modified to ensure an overall horizontal movement of the robot. Increasing or decreasing the length (l) amounts to pivoting all the bars of each leg around each fixed point F.
Legs description :
Each leg consists of ten articulated bars (bars b to k) of which two form a rigid link (bars e and h)). See Figure 3 above.
The two legs of the same pair are identical and mirror each other on each side of the crankshaft.
The foot of each leg describes an ovoid curve whose lower part is almost flat and horizontal, thus allowing the foot to be in contact with the ground during the propulsive phase.
In the return phase, the foot lifts off the ground and the robot can step over small obstacles without lifting its body too much.
The table of Figure 3 gives the length of each bar according to different authors :
Sources :
Jansen - Plaudens Vela.
Jansen - plaudens vela 1 (Youtube 0:53).
Wikipedia - Mécanisme de Jansen.
Exergia - Simulation von Theo Jansen's Strandbeest.
Giesbrecht Daniel - Design and optimisation of a one-degree-offreedom eight-bar leg mechanism for a walking machine.
The following files describe the monumental and architectural heritage of 140 municipalities located less than 20 km from the towns of Lectoure or Condom in Gers (France), and including Gers Lomagne and its surroundings.
List of municipalities :
The municipalities are listed alphabetically, each followed by the department number: Gers (32 by default), Lot-et-Garonne (47), Tarn-et-Garonne (82).
Each pdf file weighs approximately 500 KB, the heaviest being Lectoure (3.3 MB).
Sources :
- Wikipedia, Descriptif de chaque commune dont département, toponymie, histoire, maire, nombre d'habitants, altitude, lieux et monuments.
- Ministère de la Culture, Immeubles protégés au titre des Monuments Historiques, par département et par commune. N'inclut pas les sites protégés.
- Ministères Ecologie Energie Territoires, Liste des servitudes des sites et monuments du Gers jusque janvier 2015, par commune et incluant la protection des sites et des monuments au titre des Monuments Historiques.
- SDAP renommé STAP (Services Territoriaux de l'Architecture et du Patrimoine), Liste des monuments historiques et des sites du Lot-et-Garonne, par commune et jusqu'en 2006.
- DREAL Midi-Pyrénées (Direction Régionale de l'Environnement, de l'Aménagement et du Logement Midi-Pyrénées), Bilan des sites classés et inscrits du Tarn-et-Garonne, avril 2013, par commune.
- Ministère de la Culture, Base Mérimée du patrimoine monumental français, par commune et par monument incluant date d'origine, lieu, descriptif et propriété.
- Comet Anaïs Villages et bourgs de la Gascogne gersoise à la fin du Moyen Age (1250-1550), par commune, Thèse d'histoire, 2017, Volume 1 : Synthèse (405 p), Volume 2 : Figures (442 p), Volume 3 : Notices (680 p), Volume 4 : Atlas (391 p).
- Google, Recherche par commune (histoire, origine du nom, bastide, castelnau, castrum, fortification, rempart, château, fossé, vestige) ou par monument (protection récente des monuments et des sites au titre des Monuments Historiques)
- Google Images et Google Vidéos, Recherche par commune (monument, "carte postale", vidéo Youtube).
- IGN (Institut Géographique National, renommé Institut National de l'information Géographique et forestière), Géoportail, par commune (situation graphique des lieux-dits et des rues).
- Google, Google Maps, par commune (situation GPS des lieux-dits, rues principales, photos par Street View).
- Google, Recherche par commune (cadrans solaires, moulins, pigeonniers, puits, fontaines, lavoirs).
- Mapio, Photos d'internautes avec titre et géolocalisation précise. Recherche par Région, Département, Arrondissement, Commune.
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Constellations, apparent groupings of stars forming imaginary figures in the sky, have fascinated humanity for millennia.
Today, 88 official constellations are used to map the sky. Some, such as The Little Bear or Cassiopeia, are visible all year round, while others, such as The Swan in summer or Orion in winter, are only revealed in certain seasons.
The zodiacal constellations, crossed by the Sun during the year, are part of these 88 official ones and play a special role in astrology.
Observing the sky also reveals remarkable stars, such as Sirius or Vega, real landmarks in the celestial vault. To make the most of them, it is then important to follow certain practical observation tips.
C4.1. Official constellations [CHA][PER] :
A constellation is an apparent grouping of stars in the night sky as seen from Earth.
The International Astronomical Union (IAU) defined 88 official constellations in 1922 [IAU1]. They cover the entire celestial sphere, divided between the northern and southern hemispheres.
Please note :
- The North Star (Polaris) is an excellent representative of the celestial north pole through which the Earth's own rotation axis passes. The angular deviation between the two (about 0°38' in 2025) is in fact negligible to the naked eye. Given the Earth's own rotation, each constellation makes a complete turn in 24 hours around Polaris in a counterclockwise direction.
- The relative geometric position between constellations, as well as between stars in the same constellation, does not change significantly during the rotation of the Earth (diurnal motion) and its revolution around the Sun (seasonal motion). This is due to the very large distance between the Earth and the stars of these constellations. Only the portion of the sky visible from a given place on Earth at a specific time changes.
- Warning : On a sky map, the east and west directions are reversed to correspond to the point of view of the observer looking towards the sky.
- Stars twinkle. This phenomenon is due to the turbulence of the Earth's atmosphere that disrupts the light coming from these very distant point sources.
- The planets, on the other hand, do not twinkle or twinkle very little. They are in fact much closer to the Earth and appear in the form of small stable disks.
- The brightest objects in the Earth's night sky for the northern hemisphere are, in descending order of brightness :
The main constellations visible from the northern hemisphere are as follows, classified by period of the year and then by position in the sky, according to the following definitions :
C4.2. Constellations visible all year round
:
The constellations most visible all year round (circumpolar constellations) are as follows (see Figures below [IST][LES]) :
To find these constellations in the sky, the simplest method is as follows [DAR][CHA][PER], by referring to the map below :
- Map from July 25, 2025 at 00:00 for mainland France or latitudes from 40 to 55°N, with zenith at the center of the portion of visible sky [STE].
|
1a. Find The Great Bear : Large dipper located in north, at medium height in sky. Find Nord Star Polaris : Bright star located near The Great Bear extending towards the dipper top five times the distance between the two stars on the outer edge of the dipper (see Figure 1 above). 1b. Find The Little Bear : Small dipper with three bright stars : Polaris at the handle end and two stars on the outer edge of the dipper (see Figure 1 above). 2. Find Cassiopeia : W or M, located on a line passing through The Great Bear with Polaris in the middle. 2. Find The Dragon : The head forming a triangle of three bright stars (β, γ, ξ) located above the large dipple perpendicular to the handle end, the body and tail forming a large S of six bright stars which partially wraps between the Great Bear and the Little Bear. 3. Find The Dragon : The head forming a triangle of three bright stars (β, γ, ξ) located above the large dipple perpendicular to the handle end, the body and tail forming a large S of six bright stars which partially wraps between the Great Bear and the Little Bear. 4. Find Cepheus : Polygon with seven bright stars, located halfway between Cassiopeia and The Dragon's head. 5. Find The Giraffe : Group of nine stars including a bright one located in the extension of the handle of the Little Bear. 6. Find The Lynx : Arc of three or four bright stars visible mainly in winter and spring, the brightest star (α) being located near The Lion on a line passing through Regulus with The Lion's head (ε) in the middle. |
C4.3. Summer seasonal constellations :
The seasonal constellations most visible during the extended summer (May to October) are the following (see Figures below [IST][LES]) :
To find these constellations in the summer sky, the simplest method is the following [CHA][PER], by referring to the maps below :
- Summer Triangle.
- Map of July 25, 2025 at 00:00 for mainland France or latitudes from 40 to 55°N, with zenith at the center of the portion of visible sky [STE].
|
Find the Summer Triangle near the zenith around midnight in summer (July to September) : Quasi-isosceles triangle formed by three super-bright stars : Vega (Lyra), Altair (Eagle) and Deneb (Swan). Find the star Vega : Brightest star of the Summer Triangle, blue-white in color. 1. Find The Lyre : Small parallelogram attached to Vega. 2. Find The Eagle : Large X ended by Altair, southernmost star of the Summer Triangle, white in color. 3. Find The Swan : Large cross ended by Deneb, northernmost star of the Summer Triangle, white in color. 4. Find The Herdsman : Group of eight bright stars including a super-bright one (Acturus, orange), located near the Great Bear extending the handle of the dipper and also on a line passing through Deneb with Vega in the middle. 5. Find Hercules : Group of fourteen bright stars located just in front of the head of The Dragon ((triangle β, γ, ξ). 6. Find The Northern Crown : Group of seven stars including two bright ones, located halfway between The Herdsman and Hercules. 7. Find The Scales : Polygon with six bright stars, located on a line passing through The Great Bear with The Herdsman in the middle. 8. Find The Scorpion : Large S with nineteen bright stars including a super-bright one (Antares, red), located near The Scales to the east. 9. Find Sagittarius : Group of fifteen bright stars located near the broken tail of The Scorpion to the east. 10a. Find Ophiuchus : Polygon of twelve bright stars located halfway between Antares and Vega. 10b. Find The Serpent : Group of bright stars located on either side of Ophiuchus (eight for The Serpent's Head forming a Y and five almost aligned for The Serpent's Tail). 11. Find Andromeda : Group of nine bright stars located on a line passing through Polaris with Cassiopeia in the middle. 12. Find Pegasus : Group of eleven bright stars, four of which form a square and one is super-bright (Alpheratz, blue) bordering Andromeda. 13. Find The Fishes : Large V with three bright stars, located just next to Pegasus. 14. Find The Whale : Polygon of six bright stars extended by a line of three other bright ones, located south of The Fishes. 15. Find The Sea Goat : Polygon with eight bright stars, located on a line passing through Vega with Altair in the middle. 16. Find The Water Bearer : Group of ten bright stars, located southeast of Cygnus by extending the axis of its wings. 17. Find The Dolphin : Small diamond with additional tail, with five stars including two bright ones, located just in front of the Eagle's eye (Altair). 18. Find The Arrow : Arrow with four stars including two bright ones, located just in front of the Eagle's eye (Altair). 19. Find The Shield : Slightly broken line of two or three bright stars, located just behind the Eagle's tail. |
C4.4. Winter seasonal constellations :
The seasonal constellations most visible during the extended winter (November to April) are the following (see Figures below [IST][LES]) :
To find these constellations in the winter sky, the simplest method is the following [CHA][PER], by referring to the maps below :
- Winter triangle.
- Map of February 14, 2025 at 00:00 for mainland France or latitudes from 40 to 55°N, with zenith at the center of the portion of visible sky [STE].
- Winter hexagon.
|
Find the Winter Triangle located south around midnight in winter (December to February) : Quasi-isosceles triangle formed by three super-bright stars : Sirius (Canis Major), Procyon (Canis Minor) and Betelgeuse (Orion). Find the star Sirius (brightest star in the Winter Triangle, blue-white in color. 1. Find The Canis Major : Group of ten bright stars including Sirius. 2. Find The Canis Minor : Group of two bright stars including Procyon, easternmost star of the Winter Triangle, white in color. 3. Find Orion : Hourglass with twelve bright stars including a belt of three aligned stars and Betelgeuse, westernmost star of the Winter Triangle, red in color. 4. Find The Have : Group of eight bright stars, located just south Orion. 5. Find The Bull : Large Y with eleven bright stars including a super-bright one (Aldebaran, orange), located just above the arc of Orion, on a line passing through Sirius with Betelgeuse in the middle. 6. Find The Charioteer : Polygon with nine bright stars including a super-bright one (Capella, yellow) and a bright one bordering The Bull (Elnath, blue). 7. Find Perseus : Group of nine bright stars including a super-bright one (Mirfak, white), located on a line passing through Orion with The Bull in the middle. 8. Find The Ram : Curved line of four bright stars, located on a line through Betelgeuse with Aldebaran in the middle. 9. Find The Triangle : Elongated triangle of three bright stars, located just next The Ram. 10. Find The Twins : Group of eleven bright stars including two super-bright ones (Pollux, orange, and Castor, white), located in front of the two horns of The Bull. 11. Find The Crab : Large Y with four bright stars, located on a line through Sirius with Procyon in the middle. 12. Find The Lion : Elongated polygon with nine bright stars including a super-bright one (Regulus, blue), located near The Great Bear extending towards the dipper underside five times the distance between the two stars on the outer edge of the dipper. 13. Find The Virgin : Group of nine bright stars including a super-bright one (Spica, blue), located east of The Lion. 14. Find The Crow : Group of five bright stars, located southeast of The Lion. 15. Find The Cup : Polygon with four stars including a bright one, located south of The Lion. Notice the Winter Hexagon near the zenith around midnight in winter (December to February) : Symmetrical hexagon with six super-bright stars : Sirius (Canis Major), Procyon (Canis Minor), Pollux (The Twins), Capella (The Charioteer), Aldebaran (The Bull), Rigel (Orion). Notice the Big G near the zenith around midnight in winter (December to February) : Big G with nine super-bright stars : Betelgeuse, Bellatrix and Rigel (Orion), Sirius (Canis Major), Procyon (Canis Minor), Pollux and Castor (The Twins), Capella (The Charioteer), Aldebaran (The Bull). |
C4.5. Zodiacal constellations :
The astronomical zodiac is a band in the sky that extends about 8° on either side of the ecliptic (the plane of the Earth's orbit around the Sun).
It includes thirteen official constellations, which are the only ones that the Sun obscures during its annual path, as seen from Earth.
These constellations are as follows, listed from 1 to 12 in the order in which the Sun passes through them :
Their visibility from the northern hemisphere is as follows :
* Constellations visible all year round : none.
* Summer seasonal constellations (May to October) : The Scales, The Scorpion, Ophiuchus, Sagittarius, The Sea Goat, The Water Bearer, The Fishes.
* Winter seasonal constellations (November to April) : The Ram, The Bull, The Twins, The Crab, The Lion, The Virgin.
C4.6.
Tips for good observation :
To properly observe the stars, constellations, planets and satellites in the sky, it is advisable to [CHA][PER] :
C4.7. Color and magnitude :
The apparent color of stars (seen with the naked eye) depends mainly on their surface temperature according to the following simplified classification :
- Blue : Very hot stars ( > 10 000 K approximately), such as Spica.
- White : Hot stars (from 6 000 to 10 000 K approximately), such as Sirius.
-
Yellow : Stars of average temperature (from 5 200 to 6 000 K approximately), such as the Sun.
- Orange : Cold stars (from 3 700 to 5 200 K approximately), such as Aldebaran.
- Red : Very cold stars ( < 3 700 K approximately), such as Betelgeuse.
However, factors significantly influence the apparent color :
- Brightness (whitish effect for very bright stars)
-
Earth's atmosphere (reddish effect near the horizon due to the light diffusion in the air)
-
Interstellar dust (accentuation of red by absorption of short wavelengths (blue))
- Interstellar gas clouds (absorption and diffusion of certain wavelengths depending on their composition)
- Sensitivity of the human eye (attenuation of blue and red in the dark)
The apparent magnitude (M) of a star corresponds to its brightness state as perceived from Earth :
M = -2.5 log10[F/F0]
with :
F = luminous flux received from the star (in W/m2)
F0 = reference luminous flux corresponding to M = 0 (historically that of Vega, before the current more precise measurements).
M is a standardized measure that takes into account four factors :
- Intrinsic luminosity of the star. It corresponds to the total power of light (L in Watt) emitted at its surface, then diffused uniformly in all directions across a spherical surface of increasing radius r.
- Distance between the star and the Earth. The apparent luminosity (I in W/m2), perceived at the distance r from the star, decreases in fact according to the inverse square law : I = L/(4 π r2).
- Extinction (absorption and diffusion of light by the Earth's atmosphere, interstellar dust and gas clouds between the star and the Earth)
- Sensitivity of the human eye (which perceives the apparent luminosity according to an inverse logarithmic scale)
Warning : The lower the numerical value (M) of the apparent magnitude, the brighter the star.
C4.8. Sources relative to constellations :
[CHA] ChatGPT, le moteur d'Intelligence Artificielle développé par OpenAI.
[DAR] Découvrir le ciel à l'oeil nu, Bertrand D'Armagnac et Carine Souplet, Stelvision.
[IAU1] IAU, Les constellations.
[IAU2] IAU, Comment sont nommées les étoiles ?.
[IMA] Imago Mundi, La Girafe.
[IMA] Imago Mundi, Le Lion.
[IMA] Imago Mundi, Le Lynx.
[IMA] Imago Mundi, Ophiuchus.
[IMA] Imago Mundi, Sagittaire.
[IST] iStock, Constellations.
[LES] Les Astronautes, Comment reconnaître les constellations dans le ciel ?.
[PER] Perplexity, le moteur d'Intelligence Artificielle développé par Perplexity AI.
[STE] Stelvision, Carte du ciel du jour (pour France métropolitaine ou latitudes de 40 à 55°N, avec zénith au centre de la portion de ciel visible).
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Last page update : 29 January, 2025.