A galaxy full of surprises — NGC 3621 is bulgeless but has three central black holes

This image, from ESO’s Very Large Telescope (VLT), shows a truly remarkable galaxy known as NGC 3621. To begin with, it is a pure-disc galaxy. Like other spirals, it has a flat disc permeated by dark lanes of material and with prominent spiral arms where young stars are forming in clusters (the blue dots seen in the image). But while most spiral galaxies have a central bulge — a large group of old stars packed in a compact, spheroidal region — NGC 3621 doesn’t. In this image, it is clear that there is simply a brightening to the centre, but no actual bulge like the one in NGC 6744 (eso1118), for example.

NGC 3621 is also interesting as it is believed to have an active supermassive black hole at its centre that is engulfing matter and producing radiation. This is somewhat unusual because most of these so-called active galactic nuclei exist in galaxies with prominent bulges. In this particular case, the supermassive black hole is thought to have a relatively small mass, of around 20 000 times that of the Sun.

Another interesting feature is that there are also thought to be two smaller black holes, with masses of a few thousand times that of the Sun, near the nucleus of the galaxy. Therefore, NGC 3621 is an extremely interesting object which, despite not having a central bulge, has a system of three black holes in its central region.

This galaxy is located in the constellation of Hydra (The Sea Snake) and can be seen with a moderate-sized telescope. This image, taken using B, V, and I filters with the FORS1 instrument on the powerful VLT, shows striking detail in this odd object and also reveals a multitude of background galaxies. A number of bright foreground stars that belong to our own Milky Way are also visible.

Crédito:

ESO

Sobre a imagem

Id:potw1148a
Tipo:Observação
Data de divulgação:28 de Novembro de 2011 às 10:00
Tamanho:2044 x 2044 px

Sobre o objeto

Nome:NGC 3621
Tipo:Local Universe : Galaxy : Type : Spiral
Local Universe : Galaxy : Component : Central Black Hole
Distância:22 milhão anos-luz
Constellation:Hydra
Categoria:Galaxies

Formatos de imagens

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Coordenadas

Position (RA):11 18 16.56
Position (Dec):-32° 48' 50.91"
Field of view:6.81 x 6.81 arcminutes
Orientação:O norte está a 89.8° à esquerda da vertical

Cores e filtros

BandaTelescópio
Óptico
B
Very Large Telescope
FORS1
Óptico
V
Very Large Telescope
FORS1
Infravermelho
I
Very Large Telescope
FORS1

 

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