NGC 6822 - Barnard's Galaxy - Caldwell 57 - IC 4895 (Márcio Spínola)

NGC 6822 - Barnard's Galaxy - Caldwell 57 - IC 4895

NGC 6822 - Barnard's Galaxy - Caldwell 57 - IC 4895

This beautiful dwarf galaxy has only 7,000 light years in extension, structure similar to the small Magellan cloud, and is located just 1.6 million light years away in the constellation of Sagittarius. It is a bar-shaped irregular galaxy that is part of the local group of galaxies and is the closest of the galaxies after the Large and Small Magellan Cloud.

This galaxy is considered to have low amounts of elements heavier than hydrogen and helium, being an object of studies for the evolution of stars. It is home of Cepheid-type variable stars that are important because they hold a relationship between luminosity of distance and shape used by Hubble to estimate the distance from us.

In this image acquired with 23min and 20s of exposure we were unable to resolve great majority of stars, but it is possible to note the bluer glow corresponding the integration of thousands and thousands of younger stars in contrast to a more orange background color, probably corresponding to populations of smaller and longer-lasting stars. Also that it is possible to notice some nebulosity that apparently is a very reddish nebula in the shape of a bubble known as Bernard’s Bubble Nebula. This is an emission region of H II and has a radius of approximately 380 light years (more on Wikipedia).

NGC 6822 - Galáxia de Barnard – Caldwell 57 – IC 4895

Esta belíssima galáxia anã que possui apenas 7 mil anos luz de comprimento e estrutura semelhante a pequena nuvem de Magalhães e está localizada a apenas 1.6 milhões de anos luz de distância na constelação de Sagitário. É uma galáxia irregular em formato de barra que faz parte do grupo local de galáxias sendo a mais próxima das galáxias depois da Grande e Pequena Nuvem de Magalhães.

Esta galáxia é considerada possuir baixa quantidade de elementos mais pesados que o hidrogênio e hélio sendo um objeto de estudos para evolução de estrelas. Possui estrelas variáveis do tipo cefeídas que são importantes, pois guardam uma relação entre luminosidade de distância e forma utilizadas por Hubble para estimar a distância de nós.

Neste registro de apenas 23min e 20s de exposição não conseguimos resolver a maioria das estrelas, mas é possível notas as cores mais azuladas (estrelas mais jovens) em contraste com uma cor de fundo mais alaranjada provavelmente correspondendo a populações de estrelas menores e mais duradouras. Também que é possível notar através da resolução da placa o NGC 6822B que aparentemente é uma nebulosa bem avermelhada em forma de uma bolha, sendo uma região de emissão de H II e possui um raio aproximado de 380 anos luz.

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Status	Advanced success
Started	...
Astrometry.net job	8540620
PixInsight job	BAUQ619CLZVWV2ZKIB9LH4JKUWAHF1M6
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	19h44m56s.62
RA (top/left)	19h44m01s.92
RA (top/right)	19h43m09s.33
RA (bottom/right)	19h45m51s.34
RA (bottom/left)	19h46m43s.50

Dec (center)	-14°47′54″.9
Dec (top/left)	-14°17′23″.9
Dec (top/right)	-15°08′49″.3
Dec (bottom/right)	-15°18′30″.7
Dec (bottom/left)	-14°26′59″.0

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