Orionnebulosan

Orionnebulosan
Orionnebulosan fotograferad i synligt ljus
Observationsdata
TypReflektionsnebulosa
StjärnbildOrion
Rektascension05t 35m 17s
Deklination-05° 23′ 28″[1]
Avstånd1344 ± 20 ljusår
Skenbar storlek65x60 bågminuter
Skenbar magnitud+4,0
Fysiska egenskaper
Radie12 ljusår
Upptäckt
Upptäcktsår1610
UpptäckareNicolas-Claude Fabri de Peiresc
Andra beteckningar
NGC 1976, LBN 974, XSS J05351-0519, 3C 145, Mills 05+0A, DGW65 26, 4C -05.21, MSH 05-0-11, PT56 6, CTA 37, NRL 6, WCO2009 J053517-052326, GAL 209.01-19.4, PKS 0532-054, LBN 209.13-19.35, ORION A, PKS 0532-05[1], GC 1179, h 360, Sh 2-281
Se även: Nebulosor, Lista över nebulosor

Orionnebulosan, även kallad M42 - Messier 42, eller NGC 1976, är en ljusstark nebulosa i Orions stjärnbild.

Nebulosan har en diameter på cirka 24 ljusår och ligger 1 344 ± 20 ljusår bort från jorden. Det gör den till det närmaste området i Vintergatan där massiv stjärnbildning kan observeras.

Under mörka förhållanden, så som de som råder på landsbygden, är det relativt lätt att se Orionnebulosan med blotta ögat som den suddiga fläck som utgör mellersta "stjärnan" i Orions svärd. Den hittas enklast genom att utgå från den mellersta stjärnan i Orions bälte och nedanför denna finna de tre ljuspunkter i en lodrät rad som utgör Orions svärd. Den mellersta av dessa är Orionnebulosan. Nebulosan är egentligen bara en liten välupplyst del av ett mycket större gasmolnskomplex som upptar hela Orions stjärnbild.

Orionnebulosan M42.

Orionnebulosan är både en så kallad emissionsnebulosa och en reflektionsnebulosa. I den centrala och ljusaste delen av nebulosan kan man även med ett mindre teleskop finna de fyra ljusstarka stjärnor som bildar det så kallade Trapetset eller Trapezium. Dessa jättestjärnor är tillsammans med många andra stjärnor i regionen relativt nybildade, troligen bara för 1-3 miljoner år sedan. De producerar väldiga stjärnvindar som skapar chockvågor i det omgivande gasmolnet och blir därmed orsak till att ytterligare stjärnor bildas. Enbart den massivaste av de fyra stjärnorna, Theta Orionis C, genererar en mäktig stjärnvind som är 100 000 gånger starkare än solens. Den ultravioletta strålningen från Trapetsstjärnorna joniserar nebulosans gasmoln vilket ger upphov till molnets rödaktiga färg.

(c) ESA/Hubble, CC BY 4.0
Exempel på nya stjärnor och planetsystem under bildande i Orionnebulosan.

Orionnebulosans relativa närhet till jorden har gjort den till ett av de allra mest studerade objekten på stjärnhimlen. Detta har på senare år lett fram till helt nya insikter om hur stjärnor och planetsystem bildas och utvecklas. Man känner för närvarande till cirka 700 stjärnor i Orionnebulosan som är under bildande. Hubbleteleskopet har bland dessa hittat över 150 som omges av en protoplanetär skiva vilken utgör förstadiet till utvecklingen av ett planetsystem. Studierna av detta har gett en klarare bild av hur vår egen sol och jord har kommit till.

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Media som används på denna webbplats

Orion Nebula with proplyd highlights (captured by the Hubble Space Telescope).jpg
(c) ESA/Hubble, CC BY 4.0

The Orion Nebula is home to tens of what could be fledgling planetary systems. In this image, six of these modest "smudges" with big potential are highlighted (from top down): 132-1832, 206-446, 180-331, 106-417, 231-838 and 181-825.

Within the gaseous folds of Orion, researchers have identified two different types of discs around young and forming stars: those that lie close to the brightest star in the cluster (Theta¹ Orionis C) and those farther away from it. This bright star heats up the gas in the nearby discs, causing them to shine brightly. The discs that are farther away do not receive enough of the energetic radiation from the star to set the gas ablaze; thus, they can only be detected as a dark silhouette against the background of the bright nebula, as the dust that surrounds these discs absorbs background visible light. In these silhouetted discs, astronomers are better able to study the properties of the dust grains that are thought to bind together and possibly form planets like our own.

The brighter discs are indicated by a glowing cusp in the excited material and facing the bright star, but which we see at a random orientation within the nebula, so some appear edge on, and others face on, for instance. Other interesting features enhance the look of these captivating objects, such as emerging jets of matter and shock waves. The dramatic shock waves are formed when the stellar wind from the nearby massive star collides with the gas in the nebula, sculpting boomerang shapes or arrows.
Orion Nebula - Hubble 2006 mosaic 18000.jpg
In one of the most detailed astronomical images ever produced, NASA/ESA's Hubble Space Telescope captured an unprecedented look at the Orion Nebula. ... This extensive study took 105 Hubble orbits to complete. All imaging instruments aboard the telescope were used simultaneously to study Orion. The Advanced Camera mosaic covers approximately the apparent angular size of the full moon.
Coordinates
Position (RA):	5 35 9.73
Position (Dec):	-5° 24' 50.32"
Field of view:	30.03 x 30.03 arcminutes
Orientation:	North is 0.0° left of vertical
Colours & filter Band	Wavelength	Telescope
Optical B	435 nm	Hubble Space Telescope ACS
Optical V	555 nm	Hubble Space Telescope ACS
Optical H-alpha	658 nm	Hubble Space Telescope ACS
Infrared I	775 nm	Hubble Space Telescope ACS
Infrared Z	850 nm	Hubble Space Telescope ACS
Notes: Additional observational data from the WFI instrument on the ESO.MPG 2.2-metre telescope.
PIA01322 - Chaos at the Heart of Orion.jpg

NASA's Spitzer and Hubble Space Telescopes have teamed up to expose the chaos that baby stars are creating 1,500 light years away in a cosmic cloud called the Orion nebula.

This striking infrared and visible-light composite indicates that four monstrously massive stars at the center of the cloud may be the main culprits in the familiar Orion constellation. The stars are collectively called the Trapezium. Their community can be identified as the yellow smudge near the center of the image.

Swirls of green in Hubble's ultraviolet and visible-light view reveal hydrogen and sulfur gas that have been heated and ionized by intense ultraviolet radiation from the Trapezium's stars. Meanwhile, Spitzer's infrared view exposes carbon-rich molecules called polycyclic aromatic hydrocarbons in the cloud. These organic molecules have been illuminated by the Trapezium's stars, and are shown in the composite as wisps of red and orange. On Earth, polycyclic aromatic hydrocarbons are found on burnt toast and in automobile exhaust.

Together, the telescopes expose the stars in Orion as a rainbow of dots sprinkled throughout the image. Orange-yellow dots revealed by Spitzer are actually infant stars deeply embedded in a cocoon of dust and gas. Hubble showed less embedded stars as specks of green, and foreground stars as blue spots.

Stellar winds from clusters of newborn stars scattered throughout the cloud etched all of the well-defined ridges and cavities in Orion. The large cavity near the right of the image was most likely carved by winds from the Trapezium's stars.

Located 1,500 light-years away from Earth, the Orion nebula is the brightest spot in the sword of the Orion, or the "Hunter" constellation. The cosmic cloud is also our closest massive star-formation factory, and astronomers believe it contains more than 1,000 young stars.

The Orion constellation is a familiar sight in the fall and winter night sky in the northern hemisphere. The nebula is invisible to the unaided eye, but can be resolved with binoculars or small telescopes.

This image is a false color composite where light detected at wavelengths of 0.43, 0.50, and 0.53 microns is blue. Light at wavelengths of 0.6, 0.65, and 0.91 microns is green. Light at 3.6 microns is orange, and 8.0 microns is red.