A galaxy torn and rekindled, NGC 1313 burns with newborn stars along arms that refuse to keep their shape
NGC 1313, known as the Topsy Turvy Galaxy, is a barred spiral of type SB(s)d in the southern constellation Reticulum; a late-type system with a loose, irregular disk and an off-centre bar, it is listed as an HII galaxy for the intensity of its star formation It lies about 13.5 million light-years away, a distance fixed by the tip of the red giant branch and by Cepheid variables, and spans 9.1 by 6.9 arcminutes on the sky, roughly 36,000 light-years across or a little over a third the diameter of the Milky Way; at an integrated visual magnitude of 8.7 it is one of the brighter galaxies of the far southern sky The bar crosses the centre as a band of blue-white light dominated by young stars rather than the warm, old bulge of most spirals; from its ends the arms break into chains of rose-magenta hydrogen clouds and blue star clusters, richest along the arm curving to the right of the bar and in a dense starburst complex at the lower edge of the disk; dust lanes cut dark channels below the bar, the outer disk resolves into individual supergiant stars and young clusters, and dozens of far more distant galaxies are scattered across the background The lopsided arms, the offset bar and an extended loop of neutral hydrogen beyond the visible disk point to a past gravitational encounter, possibly with a small satellite galaxy, and that disturbance is thought to have triggered the waves of star formation still lighting its arms; close to the bar sits NGC 1313 X-1, one of the best-studied ultraluminous X-ray sources, a compact object accreting matter at rates that strain conventional limits, making this nearby galaxy a natural laboratory for how encounters shape small spirals
Imaged in LRGB and Hα OTA Planewave CDK 1000, Camera QHY 461, at Observatorio El Sauce, Chile
Image Acquisition and Processing: Mike Selby