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Spiral Galaxy NGC 253
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Name: NGC 253, Silver Dollar galaxy, Caldwell 65
Description: Spiral Galaxy
Position (J2000): RA 00hr 47m 33.65s Dec -25° 17' 5.94"
Constellation: Sculptor
Distance: 11 million light years
Apparent Dimensions: 27.5' × 6.8'
Visual Magnitude: 8.0
Field of view: 32.87 x 29.79 arcminutes
Orientation: North is 1.6° right of vertical
Image Credit: ESO
Release date: January 19, 2009

Other NGC 253 Images:  G0902     G1025     ESO1334
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Preface:   Measuring 70 000 light-years across and lying 13 million light-years away, the nearly edge-on spiral galaxy NGC 253 is revealed here in an image from the Wide Field Imager (WFI) on the MPG/ESO 2.2-meter telescope at the La Silla Observatory. The image is based on data obtained through four different filters (R, V, H-alpha and OIII). North is up and East to the left. The field of view is 30 arcminutes


Thanks to the Very Large Telescope's acute and powerful near-infrared eye, astronomers have uncovered a host of new young, massive and dusty stellar nurseries in nearby galaxy NGC 253. The center of this galaxy appears to harbor a twin of our own Milky Way's supermassive black hole.

Astronomers from the Instituto de Astrofísica de Canarias (Spain) used NACO, a sharp-eyed adaptive optics instrument on ESO's Very Large Telescope (VLT), to study the fine detail in NGC 253, one of the brightest and dustiest spiral galaxies in the sky. Adaptive Optics (AO) corrects for the blurring effect introduced by the Earth's atmosphere. This turbulence causes the stars to twinkle in a way that delights poets, but frustrates astronomers, since it smears out the images. With AO in action the telescope can produce images that are as sharp as is theoretically possible, as if the telescope were in space.

NACO revealed features in the galaxy that were only 11 light-years across. "Our observations provide us with so much spatially resolved detail that we can, for the first time, compare them with the finest radio maps for this galaxy - maps that have existed for more than a decade," says Juan Antonio Fernández-Ontiveros, the lead author of the paper reporting the results [1].

Astronomers identified 37 distinct bright regions, a threefold increase on previous results, packed into a tiny region at the core of the galaxy, comprising just one percent of the galaxy's total size. The astronomers combined their NACO images with data from another VLT instrument, VISIR, as well as with images from the NASA/ESA Hubble Space Telescope and radio observations made by the Very Large Array and the Very Large Baseline Interferometer. Combining these observations, taken in different wavelength regimes, provided a clue to the nature of these regions.

"We now think that these are probably very active nurseries that contain many stars bursting from their dusty cocoons," says Jose Antonio Acosta-Pulido, a member of the team. NGC 253 is known as a starburst galaxy, after its very intense star formation activity. Each bright region could contain as many as one hundred thousand young, massive stars.

This comprehensive set of data also leads astronomers to conclude that the center of NGC 253 hosts a scaled-up version of Sagittarius A*, the bright radio source that lies at the core of the Milky Way and which we know harbors a massive black hole (see ESO Press Release eso0846). "We have thus discovered what could be a twin of our Galaxy's Center," says co-author Almudena Prieto.


[1] Because observations in the radio wavelength domain are not affected by the turbulence of the atmosphere and because radio waves have much longer wavelengths than visible light, it is relatively easy to obtain very high spatial resolution at radio wavelengths by combining observations from well-separated radio telescopes (using interferometry). This is why, until recently, radio maps of galaxies show much more detail than their equivalents in the near-infrared or the optical.