BellaOnline Forums Education Astronomy Sextans - the Sextant *new article*

Sextans is a southern constellation invented by Polish astronomer Johannes Hevelius in the 17th century to represent his astronomical sextant. Its stars are dim, but it's rich in deep sky objects.

Sextans - the Sextant

The galaxy NGC 3115 in Sextans in a composite image of data from NASA's Chandra X-ray Observatory and the European Southern Observatory's Very Large Telescope (VLT)

Using the Chandra image, the flow of hot gas toward the supermassive black hole in the center of this galaxy has been imaged. The Chandra data are shown in blue and the optical data from the VLT are colored gold. The point sources in the X-ray image are mostly binary stars containing gas that is being pulled from a star to a stellar-mass black hole or a neutron star. The inset features the central portion of the Chandra image, with the black hole located in the middle.

NGC 3115 the nearest billion-solar-mass black hole to Earth. It's a lenticular galaxy about 32 million light years from Earth.

Image credit: X-ray: NASA, CXC, Univ. of Alabama, K. Wong et al; Optical: ESO, VLT

Composite image of CL J1001+0220, the most distant known galaxy cluster - over 11 billion light years away. X-rays from NASA's Chandra are in purple, infrared from ESO's UltraVISTA are in red, green & blue, and also in green are radio waves from ALMA (the Atacama Large Millimeter/submillimeter Array).

The irregular dwarf galaxy Sextans A looks square from our point of view. (The bright orange star is a foreground star in our Milky Way.)

Credit: S. D. Van Dyk (IPAC /Caltech) et al., KPNO 2.1-m Telescope, NOAO

Some 400,000 light years away in Sextans Spiral galaxy NGC 3169 and neighboring NGC 3166 are interacting gravitationally. The spiral arms of NGC 3169 (at the top) are distorted into tidal tails by this interaction. It probably contains a supermassive black hole in its core. If you look very carefully, you may be able to pick out the small and dim galaxy NGC 3165 just to the bottom right of NGC 3166.

Image Credit & Copyright: Warren Keller, Steve Mazlin, Jack Harvey, Steve Menaker (SSRO/ UNC/PROMPT/ CTIO)

Here is Hevelius's depiction of Sextans Uraniae in his atlas Firmamentum Sobiescianum sive Uranographia (1687). Sextans Uraniae means astronomical sextant - the name was shortened after the time of Hevelius.

Some modern navigators use a sextant. [When a giant solar storm knocks out the GPS system, these navigators will still be able to find their way around!] Here is a simple drawing of a modern sextant.