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20 April 2011
The disturbed galactic duo NGC 3169 and NGC 3166
The galaxies in this cosmic pairing, captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile, display some curious features, demonstrating that each member of the duo is close enough to feel the distorting gravitational influence of the other. The gravitational tug of war has warped the spiral shape of one galaxy, NGC 3169, and fragmented the dust lanes in its companion NGC 3166. Meanwhile, a third, smaller galaxy to the lower right, NGC 3165, has a front-row seat to the gravitational twisting and pulling of its bigger neighbours.
NGC 3169 and NGC 3166 in the constellation of Sextans
This galactic grouping, found about 70 million light-years away in the constellation Sextans (The Sextant), was discovered by the English astronomer William Herschel in 1783. Modern astronomers have gauged the distance between NGC 3169 (left) and NGC 3166 (right) as a mere 50 000 light-years, a separation that is only about half the diameter of the Milky Way galaxy. In such tight quarters, gravity can start to play havoc with galactic structure.
Wide-field view of the sky around NGC 3169 and NGC 3166
Spiral galaxies like NGC 3169 and NGC 3166 tend to have orderly swirls of stars and dust pinwheeling about their glowing centres. Close encounters with other massive objects can jumble this classic configuration, often serving as a disfiguring prelude to the merging of galaxies into one larger galaxy. So far, the interactions of NGC 3169 and NGC 3166 have just lent a bit of character. NGC 3169’s arms, shining bright with big, young, blue stars, have been teased apart, and lots of luminous gas has been drawn out from its disc. In NGC 3166’s case, the dust lanes that also usually outline spiral arms are in disarray. Unlike its bluer counterpart, NGC 3166 is not forming many new stars.
Supernova 2003cg in the galaxy NGC 3169
NGC 3169 has another distinction: the faint yellow dot beaming through a veil of dark dust just to the left of and close to the galaxy’s centre [1]. This flash is the leftover of a supernova detected in 2003 and known accordingly as SN 2003cg. A supernova of this variety, classified as a Type Ia, is thought to occur when a dense, hot star called a white dwarf — a remnant of medium-sized stars like our Sun — gravitationally sucks gas away from a nearby companion star. This added fuel eventually causes the whole star to explode in a runaway fusion reaction.
Zooming in on the disturbed galactic duo NGC 3169 and NGC 3166
Notes:
[1] Other much more noticeable points of light, such as the one toward the left end of the spiral arm running underneath of NGC 3169’s core, are stars within the Milky Way that happen to fall by chance very close to the line of sight between our telescopes and the galaxies.
[2] ESO’s Hidden Treasures 2010 competition gave amateur astronomers the opportunity to search through ESO’s vast archives of astronomical data, hoping to find a well-hidden gem that needed polishing by the entrants. To find out more about Hidden Treasures, visit http://www.eso.org/public/outreach/hiddentreasures/.
More information
ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and VISTA, the world’s largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
Links:
* Photos of La Silla Observatory: http://www.eso.org/public/images/archive/category/lasilla/
* The MPG/ESO 2.2-metre telescope: http://www.eso.org/public/images/esopia00046teles/
Images, Text, Credit: ESO / Igor Chekalin / IAU and Sky & Telescope / Digitized Sky Survey 2. Acknowledgement: Davide De Martin / Video: ESO/A. Fujii/Digitized Sky Survey 2/Igor Chekalin. Music: John Dyson (from the album Moonwind).
Cheers, Orbiter.ch
