Orion belt

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Orion belt , and belt of Orion ( English Orion's belt ), a showy is star series in the middle of the constellation Orion mentioned, which with the belt stars Mintaka (δ Ori), Alnilam (ε Ori) and Alnitak is formed (ζ Ori). Their star locations are near the celestial equator (→ equatorial coordinate system ).

Orion constellation with the three belt stars δ, ε and ζ
The three belt stars in Orion: Mintaka (δ Ori) on the right, Alnilam (ε Ori) in the middle, Alnitak (ζ Ori) on the left - next to it the Flame Nebula and below the Horsehead Nebula and also σ Ori
Map of the constellation Orion with a depiction of the hunter Orion in Greek mythology ( London , 1825), Orion belt blue.

These three bright stars of the second magnitude are apparently close to each other at a distance of about 1 °. They can be connected to each other in the imagination and thus form a row on an imaginary, almost straight line. Perceived as the stars of a belt, their names go back to medieval Arabic astronomy .

The star in the middle of the belt, Alnilam or Epsilon Orionis (ε Ori), has after Rigel (β Ori) and Beteigeuze (α Ori) as stars of the first magnitude and Bellatrix (γ Ori) the fourth strongest apparent brightness in Orion, but a considerably greater distance than this from the sun. It is also further away than the somewhat weaker outer stars of the Orion belt, Mintaka or Delta Orionis (δ Ori) to the west (or right) and Alnitak or Zeta Orionis (ζ Ori) to the east (or left). Together with well over a hundred, much fainter stars of similar age, these two belong to an open star cluster around 800–900 light years away: Collinder 70 , whose apparent size is around 3 °.

In the vicinity of the Orion Belt, various zones around 1500 light years away from the star formation of the Milky Way can be observed, which belong to the Orion complex . This includes u. a. next to the flame fog and the Pferdekopfnebel also freiäugig visible Orionnebel ( M 42 ) to the south (or below) in the so-called "Sword".

With the stars connected to the belt as an auxiliary line, the brightest star can be found about six times longer to the left, Sirius (α CMa) in the constellation Great Dog ; Aldebaran (α Tau) in the constellation Taurus can be found at a similar distance to the right .

Naming and cultural reception

The constellation Orion bears its common name in western culture and specialist astronomy after the hunter Orion in Greek mythology . If the constellation is deposited with a pictorial representation of the hunter, the stars of the Orion belt mark the belt of his clothing.

In medieval Europe the row of these three stars was also called Jacob's staff or Jacob's ladder .

In Spain, Portugal and South America as a predominantly Catholic cultural area, the name Tres Marías or Três Marias (" Three Marys ") is also common.

Location and appearance

Orion and adjacent constellations - the belt stars are almost on the celestial equator

The constellation Orion is bordered by the constellations Gemini ( Gemini ), Taurus ( Taurus ), River Eridanus , Hare ( Lepus ) and Unicorn ( Monoceros ). The latter three are closest to the Orion Belt.

The striking constellation of the belt stars in Orion is very close to the celestial equator - the declination amounts are below 2 °. This is why the belt stars for observers on earth, with the exception of areas near the poles, are completely above the horizon for almost twelve hours a day. In the evening starry sky they can be easily observed in the last and first quarter of the year, i.e. in Central Europe from late autumn to the beginning of spring.

Alnilam , the middle one, is apparently and absolutely the brightest of the three belt stars. In terms of its spherical coordinates, it is almost exactly in the middle between the asterisk of the two outer ones. The western belt star Mintaka (the right one for observers in the northern hemisphere) is only ¼ degrees south of the celestial equator; Due to the precession of the earth's axis , this angle will temporarily become zero around the year 2080.

Orion belt when the line appears to observers in central European latitudes rise approximately perpendicular to the horizon and when sinking approximately parallel horizon.

Belt star (with FK5 - coordinates ( RA , declination 2000.0) and apparent brightness )
Surname Right ascension declination brightness comment
Mintaka (δ Ori) 5 h 32 m 0.4 s 1998 243.3−0 ° 17 ′ 56.7 ″ 2.2 mag
Alnilam (ε Ori) 5 h 36 m 12.81 s 1988793.1−1 ° 12 ′ 6.9 ″ 1.69 likes between Mintaka and Alnitak about 0.07 ° south of the center ( 5 h 36 m 23 s , −1 ° 7 ′ 15 ″ ) 536231989 285
Alnitak (ζ Ori) 5 h 40 m 45.53 s 1984365.735−1 ° 56 ′ 34,265 ″ 2.03 mag


If you visualize the constellation as the figure of a hunter facing a hunter with his head at the northern end (i.e. standing upright when observed from northern latitudes), the belt in the overall picture hangs slightly to the right side of the body (i.e. in the plan view to the left below), where Orion Sword would be thought. The quiver of weaker stars hangs on the left of this row of stars on the hunting belt ( viewed from above) , three or four of which are visible to the naked eye, depending on the visibility conditions.

5 ° (corresponding to 3 finger widths with an outstretched arm) south of the center star of the belt, the Orion Nebula with the trapezoidal stars , also known as the "sword hanger" of the Orion belt, shines freely . This consists of a short row of stars , which from north to south is composed of 42 Ori, θ Ori and ι Ori, in the middle of which the nebula is the 4th object. It has the designation M42 in the Messier catalog and is the brightest emission nebula (i.e. self-luminous) in the starry sky. At the beginning of astrophotography about 150 years ago, it was the first nebula object that was successfully captured with long exposure times due to its high surface brightness .

In the Orion Nebula and the belt stars there are numerous glowing gas nebulae and thread-like fringes. New stars emerge in these so-called elephant trunks , as can be seen in infrared light. Nearby is a huge gas and molecular cloud that is 1,500 light years away and fills most of Orion in the infrared.

Just south of the southeastern belt star Alnitak is the Horsehead Nebula, which is not visible to the naked eye . This dark cloud directly in front of an emission nebula forms a high-contrast object for amateur astronomers . The glowing background gas cloud is part of the extensive Orion complex and stretches around the belt stars in a wide arc of 10–15 ° in diameter starting north of the Orion belt and extends southwards almost to the Rigel .

See also

  • Star naming
  • M43 (De Mairans Nebel), northern part of the Orion Nebula M42

Web links

Commons : Orion Belt  - collection of images, videos and audio files