7 Oct 2016

New Hubble Photo Shows Center of Spiral Galaxy NGC 247


NGC 247 is a spiral galaxy approximately 11.5 million light-years from Earth in the southern constellation Cetus.

Otherwise known as ESO 540-22, LEDA 2758 or UGCA 11, this galaxy is a member of the Sculptor Group, a collection of galaxies that also contains the more famous Sculptor Galaxy (NGC 253).

NGC 247’s nucleus is visible in this Hubble image as a bright, whitish patch, surrounded by a mixture of stars, gas and dust.

The dust forms dark patches and filaments that are silhouetted against the background of stars, while the gas has formed into bright knots known as H II regions, mostly scattered throughout the galaxy’s arms and outer areas.

NGC 247 displays one unusual feature — it is not visible in this image, but can be seen clearly in wider views of the galaxy.

The northern part of the galaxy’s disc hosts an apparent void, a gap in the usual swarm of stars and H II regions that spans almost a third of the galaxy’s total length.

There are stars within this void, but they are quite different from those around it. They are significantly older, and as a result much fainter and redder.

This indicates that the star formation taking place across most of the disc of NGC 247 has somehow been arrested in the void region, and has not taken place for around one billion years.

Although astronomers are still unsure how the void formed, recent studies suggest it might have been caused by gravitational interactions with part of another galaxy.

This colour image of NGC 247 (hi-res version) is a composite of separate exposures taken in the visible and infrared regions of the spectrum with Hubble’s Advanced Camera for Surveys (ACS).

Three filters (the blue filter F475W, the broad V-band filter F606W and the near-infrared filter F814W) were used to sample various wavelengths.

The colour results from assigning different hues to each grayscale image associated with an individual filter.

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