In general terms, galaxies and stars group together thanks to their gravitational pull, but not all galaxies follow this pattern.
The Milky Way is part of a cluster of galaxies known as the Local Group, which contains more than 54 galaxies. Interestingly there does exist a lone galaxy outside of this cluster, and the Hubble Space Telescope has been observing it.
Lonely galaxy sits on the edge of the Local Void
The gravitational center of the Local Group is found somewhere between the Milky Way galaxy and the Andromeda galaxy, but outside the Local Group lies an empty area of space which scientists call the Local Void, which measures 150 million light-years in diameter.
A dwarf spiral galaxy known as NGC 6503 can be found at the edge of this void. It measures only 30,000 light-years across, and does not form a part of any cluster of galaxies; it is completely alone, located 18 million light-years from Earth.
NGC 6503, as well as having a catchy name, is part of the Legacy Extragalactic UV Survey carried out by the Space Telescope Science Institute using data gathered by the Hubble telescope. Although such data usually only relates to tens of orbits, this time around data was gathered over 154 Hubble orbits, which meant that scientists were able to gain some real insights into the lonely galaxy.
Hubble provides new insights into NGC 6503
For one, they found out that the classic central bulge is almost nonexistent, and a huge cloud of gas envelops the galaxy. However the large gas cloud is coupled with a weak gas hole in the center of the galaxy, which only receives small amounts of gas to feed the black hole.
The images were taken with the Hubble’s Wide Field Camera 3, and released this week. They are far more detailed than previous images. Red regions show areas of gas in the spiral arms of the galaxy, whereas blue regions indicate where new stars are being formed. Dark brown shows dusty regions.
The Local Void formed due to the clustering of galaxies due to their gravitational pull, and was first discovered in 1987. As clusters move closer together, voids are created.
Data collected by Hubble reveals that the Local Void continues to widen at a rate of 230 kilometers per second.