The Hubble Space Telescope has produced the largest mosaic image of the Andromeda Galaxy ever created.
The Andromeda Galaxy is located 2.5 million lightyears away and is our closest major galaxy.
It's also the most distant object that can be seen with the naked eye, although you need good eyesight and clear, dark skies to see it.
This photomosaic of the Andromeda Galaxy was made using over 10 years of data gathered by Hubble and over 600 different images.
Some 200 million stars are captured in the image, spread across around 2.5 billion pixels.
Hubble and the secrets of Andromeda
The Hubble Space Telescope has been particularly prolific in its study of the Andromeda Galaxy throughout the decades since its launch.
As well as being a fascinating target to study in its own right, the Andromeda Galaxy provides a proxy galaxy for astronomers to learn more about the history and evolution of our own Milky Way galaxy.
That's because we're embedded within one of the Milky Way's spiral arms, and so can't get a complete view of our galaxy, the way it would look to a distant observer.
The 200 million stars that Hubble is able to pick out within the Andromeda Galaxy are all brighter than our Sun.
And there are estimated to be 1 trillion stars in the Andromeda Galaxy, meaning the vast majority aren't massive or bright enough to be detected by Hubble.
Capturing the mosaic
While one of the key advantages of the Andromeda Galaxy is just how close it is to our own (hence why it can be seen with the naked eye on a dark night), its proximity makes it a large target for Hubble to observe.
This full Andromeda Galaxy mosaic was produced over two Hubble observing programs, and the space telescope orbited Earth over 1,000 times while capturing the data.
It began with the Panchromatic Hubble Andromeda Treasury (PHAT) program a decade ago.
This saw Hubble's Advanced Camera for Surveys and Wide Field Camera photograph the northern half of the galaxy in near-ultraviolet, visible and near-infrared wavelengths.
It was followed by the Panchromatic Hubble Andromeda Southern Treasury (PHAST), which added images of about 100 million stars in the southern half of the galaxy.
Combined, the two programmes cover the whole of the Andromeda Galaxy.
Information gathered by Hubble during survey programmes is telling astronomers about the galaxy's age and the masses of its stars, and could reveal whether the Andromeda Galaxy collided with one or more galaxies in the past.
And it's revealing the differences between the Andromeda Galaxy and our own, such as how Andromeda seems to be more populated with younger stars.
This burst of star formation could indicate interactions with another galaxy in the past, and astronomers say satellite galaxy Messier 32 is a good candidate.
But this won't be the only collision the Andromeda Galaxy will experience throughout its lifetime.
Astronomers say it will smash into our own Milky Way galaxy in about 4.5 billion years' time, in an event dubbed the Andromeda-Milky Way collision.
