Changes

{{Night Sky

{{Night Sky

| image          =

| image          =

| designation    =[[Messier catalogue|Messier 17]]

| designation    =[[Messier catalogue|Messier 17]]<br/>[[NGC]] 6618

[[NGC]] 6618

| rightascension  =18^h 20^m 26^s<ref name=messier-objects>[http://www.messier-objects.com/messier-17-omega-nebula/ Omega nebula] from messier-objects.com</ref>

| rightascension  =18^h 20^m 26^s  

| declination    =-16° 10′ 36″<ref name=messier-objects/>

| declination    =-16° 10′ 36″

| distance        =5,000-6,000 ly<ref name=messier-objects/>

| distance        =5,000-6,000 ly  

| constellation  =[[Sagittarius]]

| constellation  =[[Sagittarius]]

| type            =[[Emission nebula]]

| type            =[[Emission nebula]]

| dimensions      = 11'

| dimensions      = 20x15'<ref>[http://www.constellation-guide.com/omega-nebula-messier-17/ Omega nebula - M17] from constellation-guide.com</ref>

| magnitude      = 6.0

| magnitude      =Apparent Mag: +6.0<ref name=messier-objects/><br/>Absolute Mag: -5.1<ref>From definition of absolute magnitude, using apparent magnitude given here and midway distance value, 5,500 ly.</ref>

| redshift        =

| redshift        =-0.000149±0.000002<ref name=simbad>[http://simbad.u-strasbg.fr/simbad/sim-id?Ident=m17&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id NGC 6618] from simbad.u-strasbg.fr</ref>

| radvelocity    =

| radvelocity    =-44.577±0.682 km/s<ref name=simbad/>

| propmotion      =

| propmotion      =RA: 1.79 mas/yr<ref name=simbad/><br/>Dec.: -1.96 mas/yr<ref name=simbad/>

| parallax        =

| parallax        =

}}

}}

==History==

==History==

The first observation of the Omega nebula was made in 1745 by Jean-Philippe Loys de Chéseaux.<ref name=seds/> It was independently discovered by [[Charles Messier]] on 3^rd June 1764.<ref name=messier-objects>[http://www.messier-objects.com/messier-17-omega-nebula/ Omega nebula] from constellation-guide.com</ref> [[William Herschel]]'s son, John, first noticed its resemblence to the letter omega. Admiral William Henry Smyth decided it appeared like a horseshoe and named it so in 1836.<ref name=messier-objects/>

The first observation of the Omega nebula was made in 1745 by Jean-Philippe Loys de Chéseaux.<ref name=seds/> It was independently discovered by [[Charles Messier]] on 3^rd June 1764.<ref name=messier-objects/> [[William Herschel]]'s son, John, first noticed its resemblence to the letter omega. Admiral William Henry Smyth decided it appeared like a horseshoe and named it so in 1836.<ref name=messier-objects/>

==Properties and Structure==

==Properties and Structure==