Theoretical rendering of the analemma, looking east in the northern hemisphere. The dates of the sun's position are shown.

In astronomy, an analemma (IPA: /ˌænəˈlɛmə/, Latin for the pedestal of a sundial) is a curve representing the angular offset of a celestial body (usually the Sun) from its mean position on the celestial sphere as viewed from another celestial body (usually the Earth). For instance, knowing that Earth's average solar day is almost exactly 24 hours, an analemma can be traced by plotting the position of the Sun as viewed from a fixed position on Earth at the same time every day for an entire year. The resulting curve resembles a figure of eight. This curve is commonly printed on globes. It is possible, though challenging, to "photograph" the analemma, by leaving the camera in a fixed position for an entire year and snapping images on 24-hour intervals (or some multiple thereof). An image of the analemma that includes a total solar eclipse as one of the images is called a Tutulemma[1] Image File history File links Download high-resolution version (1105x779, 60 KB) Fotomontage die das Analemma illustriert welches die Sonne über das Jahr einnimmt. ... Image File history File links Download high-resolution version (1105x779, 60 KB) Fotomontage die das Analemma illustriert welches die Sonne über das Jahr einnimmt. ... For other uses, see Astronomy (disambiguation). ... This chart shows concisely the most common way in which the International Phonetic Alphabet (IPA) is applied to represent the English language. ... For other uses, see Sundial (disambiguation). ... Sol redirects here. ... The celestial sphere is divided by the celestial equator. ... This article is about Earth as a planet. ... A synodic day is the period of time it takes for a planet to rotate once in releation to the body it is orbiting (as opposed to a sidereal day which is one complete rotation in relation to the stars). ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... World globe A Baroque era celestial globe A globe is a three-dimensional scale model of a spheroid celestial body such as a planet, star or moon, in particular Earth, or, alternatively, a spherical representation of the sky with the stars (but without the Sun, Moon, or planets, because their... This article is about the astronomical phenomenon. ...

There are three parameters that affect the size and shape of the analemma: obliquity, eccentricity, and the angle between the apse line and the line of solstices. For an object with a perfectly circular orbit and no axial tilt, the Sun would always appear at the same point in the sky at the same time of day throughout the year and the analemma would be a dot. For an object with a circular orbit but axial tilt similar to Earth's, the analemma would be a figure of eight with northern and southern lobes equal in size. For an object with eccentricity similar to Earth's, but no axial tilt, the analemma would be a straight east-west line along the equator. In astronomy, axial tilt is the inclination angle of a planets rotational axis in relation to a perpendicular to its orbital plane. ... (This page refers to eccitricity in astrodynamics. ... In astrodynamics apse line (or line of apsides) is a common name for an imaginary line defined by orbits eccentricity vector. ... “Summer solstice” redirects here. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ...

The north or south component of the analemma is the declination, or how far the Sun is north or south of the celestial equator. The east or west component is the equation of time, or the difference between solar time and local mean time. This can be interpreted as how "fast" or "slow" the sun is compared to clock time. In astronomy, declination (abbrev. ... The equation of time is the difference, over the course of a year, between time as read from a sundial and a clock. ... Solar time is based on the idea that when the sun reaches its highest point in the sky, it is noon. ... Local mean time is a form of solar time that corrects the variations of local apparent time. ...

Earth's Analemma

The analemma for Earth

Plotting the analemma with the width exaggerated shows that it is slightly asymmetrical due to the misalignment of apsides and solstices.

Due to the earth's tilt on its axis (23.45°) and its elliptical orbit around the sun, the relative location of the sun above the horizon is not constant from day to day when observed at the same time on each day. Depending on one's geographical latitude, this loop will be inclined at different angles. Image generated June 18, 2004 by User:Curps with Gnuplot and using altitude and azimuth data generated by JPL Horizons. ... Image generated June 18, 2004 by User:Curps with Gnuplot and using altitude and azimuth data generated by JPL Horizons. ... This article is about Earth as a planet. ... Image generated June 18, 2004 by User:Curps with Gnuplot and using altitude and azimuth data generated by JPL Horizons. ... Image generated June 18, 2004 by User:Curps with Gnuplot and using altitude and azimuth data generated by JPL Horizons. ... A diagram of Keplerian orbital elements. ... “Summer solstice” redirects here. ...

Plotting the analemma with the width exaggerated shows that it is slightly asymmetrical due to the misalignment of apsides and solstices. A diagram of Keplerian orbital elements. ... Solstice is an astronomical term regarding the position of the Sun in relation to the celestial equator. ...

See equation of time for an in-depth description of the east-west characteristics of the analemma. The equation of time is the difference, over the course of a year, between time as read from a sundial and a clock. ...

Other Analemmas

The analemma for Mars

On Earth, the analemma appears as a figure eight, but on other solar system bodies it may be very different[2]. The variation is due to the interplay between the tilt of each body's axis and the elliptical shape of its orbit. The analemma on Mars is not figure-8 shaped as it is on Earth. ... The analemma on Mars is not figure-8 shaped as it is on Earth. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... This article is about Earth as a planet. ... The axis of rotation of a rotating body is a line such that the distance between any point on the line and any point of the body remains constant under the rotation. ...

In the following list, "day" and "year" refer to the synodic day and sidereal year of the particular body. A synodic day is the period of time it takes for a planet to rotate once in releation to the body it is orbiting (as opposed to a sidereal day which is one complete rotation in relation to the stars). ... The sidereal year is the time for the Sun to return to the same position in respect to the stars of the celestial sphere. ...

• Mercury: Because the day is exactly two years long (due to orbital resonance), the method of plotting the sun's position at the same time each day would only yield a single point. However, the equation of time can still be calculated for any time of the year, so an analemma can be graphed with this information. The resulting curve is a nearly straight east-west line. An interesting phenomenon occurs because of the relationship between Mercury's day and year (see Mercury (planet)#Orbit and rotation).
• Venus: There are slightly less than two days per year, so it would take several years to accumulate a complete analemma by the usual method. The resulting curve is an ellipse.
• Mars: teardrop
• Jupiter: ellipse
• Saturn: technically a figure 8, but the northern loop is so small that it more closely resembles a teardrop
• Uranus: figure 8
• Neptune: figure 8
• Pluto: figure 8

This article is about the planet. ... In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... This article is about the planet. ... Adjectives: Venusian or (rarely) Cytherean Atmosphere Surface pressure: 9. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... For other uses, see Jupiter (disambiguation). ... This article is about the planet. ... For other uses, see Uranus (disambiguation). ... For other uses, see Neptune (disambiguation). ... Adjectives: Plutonian Atmosphere Surface pressure: 0. ...

See Also

• Analemma calendar

Analemma calendars are a common feature at science museums and planetariums. ...

External links

• Astronomy Picture of the Day, 2002 9 July: Analemma
• Astronomy Picture of the Day, 2003 20 March: Sunrise Analemma
• Astronomy Picture of the Day, 2004 21 June: Analemma over Ancient Nemea
• Astronomy Picture of the Day, 2005 13 July: Analemma of the Moon
• Astronomy Picture of the Day, 2006 23 December: Analemma over the Temple of Olympian Zeus
• Astronomy Picture of the Day, 2006 30 December: Martian Analemma at Sagan Memorial Station (simulated)
• Astronomy Picture of the Day, 2007 17 June: Analemma over the Ukraine
• Analemma Series from Sunrise to Sunset
• Analemma explanation by John Holtz
• Earth Science Photo of the Day, Jan 22, 2005
• The Equation of Time and the Analemma, by Kieron Taylor
• An article by Brian Tung, contains link to a C program using a more accurate formula than most (particularly at high inclinations and eccentricities)
• The Analemma for Latitudinally-Challenged People explains rising and setting analemmas as viewed from different latitudes. It provides more depth than most analemma sources. PDF format. 1,433 Kb.
• Analemma.com is dedicated to the analemma.
• Calculate and Chart the Analemma is a web site offered by a Fairfax County Public Schools planetarium that describes the analemma and also offers a downloadable spreadsheet that allows the user to experiment with analemmas of varying shapes.