NGC 6811

NGC 6811
NGC 6811
	Star cluster
Research history
Discoverer	John herschel
opening date	August 29, 1829
Designations	NGC 6811 , OCL 185
Observational data; ( Epoch J2000.0 )
Type of	Open cluster type IV3p
Right ascension
Declination
Visible magnitude (V)	6.8
Visible dimensions (V)	15.0 '
Constellation	Swan

NGC 6811 (another designation - OCL 185 ) is an open cluster located in the constellation Cygnus about 3,300 ^[1] light years from us. This object is one of those listed in the original edition of the New General Catalog .

Observations

For the first time, NGC 6811 was observed by the English astronomer John Herschel in 1829 , adding it in 1864 to his famous New General Catalog ( NGC ). Recently, the cluster was chosen as an object for study by the Kepler mission in order to determine the characteristics of its constituent stars (mass, radius, age, etc.), as well as to search for exoplanets . ^[2]

NGC 6811 cluster is located in the northeastern part of the constellation Cygnus, not far from the bright triple star δ Cygnus (which also has the traditional name “Ruch”). The cluster is quite extended: its angular size is 15 ', which is equivalent to the half of the moon , visible in the night sky. The cluster length is about 14 light years. It is best to watch it in the summer in the northern hemisphere. It is an excellent object for observation even for beginning astronomers: its brightest stars have 10 apparent magnitude. It can even be observed with binoculars with a tenfold magnification, but it’s better to arm yourself with a medium- aperture telescope. ^[1] NGC 6811 is also called the “ Hole in the Cluster ” because of the dark area in its center. ^[3] Why stars in a cluster form a “crown” without filling its center, while it cannot be explained.

Characteristics

NGC 6811 lies outside the galactic plane, which makes it related to other relatively old open clusters. ^[4] Its total luminosity is about 2100 solar. Astronomers estimate the average age of the cluster to be 1.00 ± 0.17 billion years old and suggest that at birth it numbered up to 6000 stars. However, due to gravitational interactions with the surrounding interstellar medium and due to evolutionary stellar processes, at the moment the cluster has about 1000 stars. The spectral classes of most of them oscillate between the middle F and early K-classes. ^[2] 16 of the investigated stars turned out to be variable , 12 of which belong to the type δ Sct . ^[five]

Cluster Star List

Below is a table of some cluster stars. ^[6] Sorted by increase in right ascension .

Name	Right ascension	Declination	Spectral class	Distance (over years )	Note
HD 185115	19 ^h 35 ^m 32 ^s	+ 46 ° 35 ′ 22 ″	F1 IV	-
BD + 46 ° 2737	19 ^h 35 ^m 38 ^s	+ 46 ° 42 ′ 25 ″	M2	-
KIC 9836020	19 ^h 35 ^m 43 ^s	+ 46 ° 40 ′ 02 ″	-	-	Variable type δ Sct
Kepler-66	19 ^h 35 ^m 55 ^s	+ 46 ° 41 ′ 15 ″	G0 V	3610	Has a planet .
BD + 46 ° 2738	19 ^h 36 ^m 01 ^s	+ 46 ° 36 ′ 16 ″	K5	-
BD + 45 ° 2930	19 ^h 36 ^m 34 ^s	+ 46 ° 07 ′ 23 ″	K2 III	-
Kepler-67	19 ^h 36 ^m 36 ^s	+ 46 ° 09 ′ 59 ″	G9 V	3610	Has a planet .
KIC 9594100	19 ^h 36 ^m 55 ^s	+ 46 ° 15 ′ 18 ″	-	-	Variable type γ dor
BD + 46 ° 2739	19 ^h 37 ^m 03 ^s	+ 46 ° 38 ′ 09 ″	K0	-
HIP 96538	19 ^h 37 ^m 34 ^s	+ 46 ° 20 ′ 53 ″	-	-
BD + 46 ° 2744	19 ^h 38 ^m 12 ^s	+ 46 ° 43 ′ 09 ″	K0	-
KIC 9533449	19 ^h 38 ^m 37 ^s	+ 46 ° 11 ′ 16 ″	-	-	Variable type δ Sct

Notes

↑ ¹ ² Craig Crossen, Gerald Rhemann. Sky Vistas: Astronomy for Binoculars and Richest-Field Telescopes . - Springer, 2004. - p. 67. - ISBN 978-3-211-00851-5 .
↑ ¹ ² Søren Meibom et al. THE KEPLER CLUSTER STUDY: STELLAR ROTATION IN NGC 6811 (eng.) . The Astrophysical Journal Letters (2011 May 2). The appeal date was August 9, 2013. Archived August 16, 2013.
↑ L. Phil Simpson. Guidebook to the Constellations . - Springer, 2012. - p. 505. - ISBN 978-1-4419-6941-5 .
↑ Stephen James O'Meara. Deep-Sky Companions: The Secret Deep . - Cambridge University Press, 2011. - p. 389. - ISBN 978-1-139-50007-4 .
↑ YP Luo et al. Variable stars in the open cluster NGC 6811 (English) . New Astronomy (August 2009). The appeal date is August 9, 2013.
↑ SIMBAD query result for NGC 6811 (English)

Links

Information in English and French from the original New Shared Catalog
Information (English) from the Revised “New Common Directory”
SIMBAD (eng.)
VizieR (eng.)
NASA / IPAC Extragalactic Database (English)
List of publications dedicated to NGC 6811

[Sky_Vistas-1] ¹ ² Craig Crossen, Gerald Rhemann. Sky Vistas: Astronomy for Binoculars and Richest-Field Telescopes . - Springer, 2004. - p. 67. - ISBN 978-3-211-00851-5 .

[Meibom-2] ¹ ² Søren Meibom et al. THE KEPLER CLUSTER STUDY: STELLAR ROTATION IN NGC 6811 (eng.) . The Astrophysical Journal Letters (2011 May 2). The appeal date was August 9, 2013. Archived August 16, 2013.

[3] L. Phil Simpson. Guidebook to the Constellations . - Springer, 2012. - p. 505. - ISBN 978-1-4419-6941-5 .

[4] Stephen James O'Meara. Deep-Sky Companions: The Secret Deep . - Cambridge University Press, 2011. - p. 389. - ISBN 978-1-139-50007-4 .

[5] YP Luo et al. Variable stars in the open cluster NGC 6811 (English) . New Astronomy (August 2009). The appeal date is August 9, 2013.

[6] SIMBAD query result for NGC 6811 (English)