Mesmerising New Hubble Picture Particulars The Enigmatic Knife Edge Galaxy

Image a spiral galaxy. You are in all probability imagining one thing like Messier 34 – lengthy, spiralling arms sweeping away from a brightly glowing centre, speckled with glittering star clusters and punctuated with darkish streaks of mud.

However from our vantage level, galaxies could be oriented any which means, together with edge-on – like NGC 5907, often known as the Knife Edge Galaxy, the attractive topic of a newly launched Hubble House Telescope picture processed by citizen scientist Judy Schmidt.

As you’ll be able to see within the picture above, the spiral arms cannot be made out from this angle. Even many of the star clusters are obscured by thick galactic mud. Nevertheless, we will infer that the galaxy is a spiral one as a result of we will nonetheless see a vivid glow in its centre.

That is the galactic bulge: a dense, tightly-packed spheroidal group of stars discovered within the centre of most spiral galaxies. Even the Milky Method has one. We will not see what it appears to be like like from the surface as a result of – in fact – we will not go away our galaxy, however we will see what it appears to be like like from inside and put collectively the remaining primarily based on our observations of different spiral galaxies.

NGC 5907, situated round 50 million light-years away within the northern constellation of Draco, is definitely an oddball in a couple of different methods. It has very low metallicity; analyses counsel that it is primarily made up of hydrogen and helium, and never a lot else. As well as, only a few big stars have been detected in it.

Since heavier components are produced over stellar generations, solid in supernovae whose mud is taken up in subsequent generations of stars, this implies that NGC 5907 is usually populated by very previous, very long-lived dwarf stars.

(Van Dokkum et al., ApJL, 2019)

The opposite attention-grabbing factor about NGC 5907 can solely be seen once you zoom out. There’s a single big stream of stars looping round it, over 700,000 light-years lengthy, in line with a current research, and confirmed by unbiased observations.

Prior to those research, NGC 5907’s stellar stream was thought to have a fancy, corkscrewing form with two loops.

There have been two competing explanations for this. The primary was that the galaxy subsumed a smaller dwarf galaxy orbiting it, very like the Milky Method is regarded as doing with the Sagittarius Dwarf Spheroidal Galaxy. The second was a significant merger with a galaxy the identical measurement as NGC 5907, round eight to 9 billion years in the past.

The newer observations counsel a 3rd state of affairs: an in depth encounter with a “tidally disrupting satellite tv for pc” that extracted a stream of stars round NGC 5907.

Nevertheless, a extra complete evaluation will should be performed to establish the perfect match for the newly noticed configuration.