The Hubble Space Telescope has captured the most detailed image yet of a close neighbour of the Milky Way - the Triangulum Galaxy.
The spiral galaxy is located at a distance of about three million light-years.
This panoramic survey gives a view of the 40 billion stars that make up one of the most distant objects visible to the naked eye.
The new image of the Triangulum Galaxy - also known as Messier 33 or NGC 598 - has a staggering 665 million pixels and showcases the central region of the galaxy and its inner spiral arms.
To stitch this gigantic mosaic together, Hubble's Advanced Camera for Surveys needed to create 54 separate images.
Under good dark-sky conditions, the Triangulum can be seen with the naked eye as a faint, blurry object in the constellation of Triangulum (the Triangle).
This gigantic image of the Triangulum Galaxy is a composite of about 54 different pointings with Hubble’s Advanced Camera for Surveys | Image: NASA, ESA, and M Durbin, J Dalcanton and B F Williams (University of Washington)
Our galaxy, the Milky Way, is part of the Local Group - an assembly of more than 50 galaxies bound together by gravity.
Its largest member is the Andromeda Galaxy, followed by the Milky Way and the Triangulum.
The remaining members are dwarf galaxies, each orbiting one of the three larger ones.
The much bigger Andromeda Galaxy was mapped by Hubble in 2015.
At only three million light-years from Earth, the Triangulum is also the smallest spiral galaxy in the group.
This image shows a gigantic gas cloud, NGC 604, located within the Triangulum Galaxy | Image: NASA, ESA, and M Durbin, J Dalcanton and BF Williams (University of Washington)
It measures only about 60,000 light-years across, compared to the 200,000 light-years of the Andromeda Galaxy; the Milky Way lies between these extremes at about 100,000 light-years in diameter.
The Triangulum is not only surpassed in size by the other two spirals, but by the multitude of stars they contain.
It has at least an order of magnitude less stars than the Milky Way and two orders of magnitude less than Andromeda.
These numbers are hard to grasp when already in this image 10 to 15 million individual stars are visible.
A diffuse nebula, NGC 595, in the Triangulum Galaxy. It is a gigantic region of ionised hydrogen about three million light-years away and was discovered by German astronomer Heinrich Ludwig d'Arrest in October 1864 | Image: NASA, ESA, and M Durbin, J Dalcanton and BF Williams (University of Washington)
It does, however, contain a huge amount of gas and dust, giving rise to rapid star formation.
New stars form at a rate of approximately one solar mass every two years.
The abundance of gas clouds is what drew astronomers to conduct this survey.
The Hubble Space Telescope is a project of international cooperation between the European Space Agency (ESA) and NASA.
