NGC 1300 is an excellent example of a Barred Spiral Galaxy located in the direction of the constellation Eridanus, the river. Eridanus is one of the 88 modern constellations, yet it dates at least as far back as the 2nd century when identified by the ancient and famous astronomer, Ptolemy.

The visually straight bar spanning the center of NGC 1300 is composed of hundreds of millions of stars like our sun. It appears to connect the galaxy core with the otherwise normal spiral arms as would be visible in a galaxy without bars.  About two thirds of spiral galaxies have some sort of bar, although most are not nearly as pronounced as this galaxy. Spiral galaxies without a bar have the designation Sa, Sb, or Sc with the “a” representing the most tighly wound arms and the “c” the most loosely wound arms. Likewise barred spirals are SBa, SBb, or SBc. NGC 1300 is between SBb and SBc so its designation is SBbc.

Since the discovery of barred spirals, the bar structure has been a bit of a mystery. More recent studies have shown that they are much more present in today’s universe at about 65% of spiral galaxy population, than in the early universe, when only 20% of spiral galaxies contained bars. Galaxies may even alternate between barred and unbarred spirals throughout their evolution.

What causes the bar structure is not the galaxy rotation, as that would diminish, not maintain a rigid bar shape. On the contrary, the bars mostly likely originate at the center of the galaxy where density waves push outwards in opposing directions causing stars revolving about the core to align in a relatively straight line and channel gas and dust inwards towards the center fueling even more star birth and more density waves. This is furthermore substantiated with the observations that barred spirals often have very active galactic nuclei. In this image the inset of the galaxy core shows both the active nuclei as well as the central spiral structure withing the overall spiral structure as often happens with these very large barred spirals. It does have a central super massive black hole containing the equivalent mass of 30-130 million suns. The galaxy itself is half the size of our own galaxy and contains some 100-200 billions stars.

NGC 1300 is a member of the Eridanus Cluster of about 200 galaxies that are on average about 75 million light years from earth and our Milky Way galaxy. NGC 1300 is one of its brighter members and was discovered by John Herschel in 1835.

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