Messier 26

Messier 26
Open cluster Messier 26
Credit: Hillary Mathis, Vanessa Harvey, REU program/NOIRLab/NSF/AURA
Observation data (J2000.0 epoch)
Right ascension18h 45m 18.0s[1]
Declination−09° 23′ 00″[1]
Distance5,160 ly (1,582 pc)[2]
Apparent magnitude (V)8.0[3]
Apparent dimensions (V)14′[3]
Physical characteristics
Radius11 ly[4]
Estimated age85.3[1] million years
Other designationsMessier 26, NGC 6694,[5] Cr 389, C 1842-094
Associations
ConstellationScutum
See also: Open cluster, List of open clusters

Messier 26, also known as NGC 6694, is an open cluster of stars in the southern constellation of Scutum. It was discovered by Charles Messier in 1764.[a] This 8th magnitude cluster is a challenge to find in ideal skies with typical binoculars, where it can be, with any modern minimum 3-inch (76 mm) aperture device. It is south-southwest of the open cluster Messier 11 and is 14′ across.[3] About 25 stars are visible in a telescope with a 150–200 mm (6–8 in) aperture.[6]

M26 spans a linear size of 22[4] light years across with a tidal radius of 25 light-years,[7] and is at a distance of 5,160[2] light years from the Earth. The brightest star is of magnitude 11[6] and the age of this cluster has been calculated to be 85.3[1] million years. It includes one known spectroscopic binary system.[8]

An interesting feature of M26 is a region of low star density near the nucleus. A hypothesis was that it was caused by an obscuring cloud of interstellar matter between us and the cluster, but a paper by James Cuffey suggested that this is not possible and that it really is a "shell of low stellar space density".[9] In 2015, Michael Merrifield of the University of Nottingham said that there is, as yet, no clear explanation for the phenomenon.[10]

  1. ^ a b c d Cite error: The named reference Wu2009 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference kharchenko2005 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Thompson2007 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Kharchenko2009 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Burnham1978 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Piskunov2008 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Mermilliod2007 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Cuffey1940 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Merrifield2015 was invoked but never defined (see the help page).


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