NGC 6744: the Milky Way’s Cosmic Twin?

The nearby galaxy NGC 6744, similar to the Milky Way, has been imaged by the European Southern Observatory. What can we see in this beautiful galactic portrait?

This picture was taken by the Wide Field Imager attached to the MPG/ESO 2.2-m telescope at ESOòÀÙs La Silla Observatory in Chile. The picture was created from exposures taken through four different filters that passed blue, yellow-green and red light and the glow coming from hydrogen gas. These are shown in this picture as blue, green, orange and red, respectively. (Image credit: ESO)

Barred spiral galaxy NGC 6744 is located in a constellation of the southern hemisphereòÀÙs sky, called Pavo (Latin for peacock). At a distance from our Solar System of about 30 million light years, NGC 6744 is not only one of the closest spiral galaxies but is thought to be one of the visible galaxies most like our own Milky Way. Is it our cosmic doppelganger?

We are looking face on at the disc of NGC6744 which is about 175 000 light years across, much larger than the Milky Way Galaxy (which is a mere 100 000 light years wide).ˆà Wrapped around the elongated nucleus of ancient stars, the spiral arms of NGC6744 are sites of star formation within the galaxy and are veined with lanes of dark dust, warmed by the furious radiation of birthing stars. Hydrogen gas ionised by the fierce ultra violet emissions of new stars shows as splatters of pinkish red along the spiral arms.

The stars in a galaxy orbit its centre, taking hundreds of millions of years to make a single circuit.ˆàˆà It is easy to imagine the galaxy slowly spinning over the aeon, but bizarrely the spiral arms remain stationary! The arms are not moving structures swirling around the galaxyòÀÙs core but rather fixed areas of greater density which stars enter, pass through and later exit. They can best be compared to that bane of a commuteròÀÙs life, the humble traffic jam. The arms are largely composed of clouds ofˆà cold ionised hydrogen and dust, the raw stuff of stars and planets.ˆà It is likely that star formation is triggered by stars ploughing into these higher density regions. Among the newly-formed stars are big and hot O and B class stars which live their short and fast lives entirely inside the structure, dying before they leave it. Their lower mass sibling stars live longer, surviving to populate the remainder of the galactic disc.

Astronomers at the European Southern Observatory used the Wide Field Imager on the MPG/ESO 2.2m telescope to capture this impressive image of NGC 6744. It also shows the much smaller companion galaxy NGC 6744A at the lower right of NGC 6744, which is reminiscent of one of the Milky WayòÀÙs neighbouring Magellanic Clouds. This beautiful image of NGC 6744 suggests how our own galactic home may look in alien eyes.