Andromeda Galaxy: Complete guide and how to see it
Facts about the Andromeda Galaxy, M31, and images captured by astrophotographers.
By Iain Todd
Published: Tuesday, 28 November 2023 at 20:30 PM
The Andromeda Galaxy is the closest major galaxy to our home galaxy the Milky Way and is located over 2 million lightyears from Earth.
It is a spiral galaxy found in the Andromeda constellation and is about 200,000 lightyears wide. It is also known as M31, part of the deep-sky Messier Catalogue.
The Andromeda Galaxy is notable for its bright blue tinge, which is caused by pockets of hot young stars burning bright blue.
The Andromeda Galaxy by Brian Cummins, Virginia, USA, 1, 2, 24 & 25 November 2019. Equipment: ZWO ASI 1600MM-Pro mono camera, Orion 8″ Newtonian astrograph reflector, Sky-Watcher NEQ6 Pro mount
How to find the Andromeda Galaxy
The Andromeda Galaxy can be seen in the night sky in the northern hemisphere throughout much of the year, but is best seen in autumn.
What’s more, the Andromeda Galaxy can be seen with the naked eye under good conditions, making it the furthest object than can be seen with the human eye.
Use Cassiopeia to find the Andromeda Galaxy
Use star Schedar in Cassiopeia to help you locate the Andromeda Galaxy. Credit: Pete Lawrence
The W-shaped constellation of Cassiopeia is a great tool for locating the Andromeda Galaxy.
This technique of hopping from star to star to help you locate a difficult target is known, unsurprisingly, as star-hopping.
From the UK, Cassiopeia appears circumpolar, meaning it never sets.
Its shape is distinctive and its stars are easy to see, even from a suburban city location.
In the winter months, Cassiopeia can be seen in the north-west. Its W shape makes it easy to find, but you can use a star chart or stargazing or astronomy app to help you.
You can use Cassiopeia to help you locate the Andromeda Galaxy using these steps:
Locate Cassiopeia in the night sky
At the bottom of the deeper of the two Vs of Cassiopeia is star Schedar
Treat this V like an arrow, which points to the Andromeda Galaxy
You’ll see the Andromeda Galaxy as a faint smudge with the naked eye
Use the Great Square of Pegasus to find the Andromeda Galaxy
To find M31 and M33, start at Alpheratz in the Great Square of Pegasus and follow our star-hopping trail. Credit: Pete Lawrence
Another star-hop you can do to find the Andromeda Galaxy involves the asterism known as the Great Square of Pegasus.
Imagine a diagonal from the southwest to northeast corner of the Square
Extend it for about the same distance again to reach star Mirach
Turn 90º to head northwest for a short distance towards dimmer Mu (m) Andromedae
The Andromeda Galaxy and the Milky Way are gravitationally interacting, and astronomers have calculated that both galaxies will collide in about 4.5 billion years time. This event is known as the Andromeda-Milky Way collision.
The Andromeda Galaxy by James Downey, Ongar, Essex, 18 August and 9 September 2020. Equipment: ZWO ASI 533MC-Pro camera, William Optics RedCat 51 apo refractor, Sky-Watcher Star Adventurer Pro mount
The Great Debate
Observations of the Andromeda Galaxy have led to some of the most important discoveries in the Universe: particularly its part in the Great Debate, in which astronomers Harlow Shapley and Heber Curtis debated about whether other galaxies existed beyond our own.
The matter was settled largely because of the work of Edwin Hubble, after whom the Hubble Space Telescope was named.
Hubble was able to photograph individual stars in the ‘Andromeda Nebula’ (as it was then known) and in 1923, his observations of Cepheid variable stars led him to conclude that the Andromeda Galaxy must be located beyond our own Galaxy.
The Andromeda by Galaxy Lloyd Mainwaring, Barry, 9 October 2020. Equipment: Canon 600D DSLR, William Optics GT81 apo refractor, Sky-Watcher HEQ5 mount.
Life in the Andromeda Galaxy?
We know there is life in the Milky Way galaxy, in the shape of us!
But what about our nearest major galaxy, the Andromeda Galaxy?
Since life has not yet been confirmed beyond Earth, astronomers cannot say for sure whether there exists life elsewhere in the cosmos, the Andromeda Galaxy included.
But since the 1990s, the field of exoplanet science – the study of planets beyond our Solar System – has exploded, to the point that now astronomers calculate there is on average at least one planet orbiting every star we can see in the night sky.
And considering the Andromeda Galaxy is thought to contain about 1 trillion stars, that means at least 1 trillion planets, some of which will be orbiting close enough to their stars for liquid water to form on the surface.
Since liquid water is a key condition for life as we know it here on Earth, it is an important part of the search for life beyond our planet.
For all we know, galaxies like the Andromeda Galaxy could be teeming with habitable worlds, some of which may even host intelligent life.
But until definitively detected, for now the question as to whether life exists in the Andromeda Galaxy remains unanswered.
Hubble image
The sharpest ever view of part of the Andromeda Galaxy, captured by the Hubble Space Telescope. Credit: NASA, ESA, J. Dalcanton (University of Washington, USA), B. F. Williams (University of Washington, USA), L. C. Johnson (University of Washington, USA), the PHAT team, and R. Gendler. – NASA, ESA, J. Dalcanton (University of Washington, USA), B. F. Williams (University of Washington, USA), L. C. Johnson (University of Washington, USA), the PHAT team, and R. Gendler
In 2015, NASA released an amazing image showing part of the Andromeda Galaxy, captured by the Hubble Space Telescope.
The image is the sharpest and largest ever taken of the galaxy.
The cropped version released by NASA contains 1.5 billion pixels, and over 600HD TV screens would be required to display the whole image.
The Andromeda Galaxy image is the biggest Hubble image ever released and shows over 100 mill stars and thousands of star clusters.
Pictures of the Andromeda Galaxy
Below is a selection of images of the Andromeda Galaxy captured by astrophotographers and BBC Sky at Night Magazine readers.
M31, the Andromeda GalaxyHarshwardhan Pathak, IC Astronomy Observatory, Spain, captured remotely via Telescope Live, 15 July 2023Equipment: QHY600PH-M mono CMOS camera, Takahashi FSQ-106EDX4 astrograph, Paramout MIX mount
The Andromeda Galaxy, Yann Sainty, Lorraine, France, 22-23 August 2022Equipment: ZWO ASI2600MM Pro mono CMOS camera, Takahashi FSQ-106EDX4 refractor, Sky-Watcher EQ6-R Pro mount
The Andromeda galaxySteve Young, Liphook, Hampshire, 20 December 2022Equipment: ZWO ASI 2600MC-Pro camera, Askar FRA400 refractor, Celestron CGX mount
The Andromeda Galaxy, Davy Viaene, remotely via the E-EyE Observatory, Spain, 3 and 8 November 2022Equipment: ZWO ASI 6200MC Pro camera, Takahashi FSQ106ED III refractor, Paramount MyT robotic mount
Andromeda galaxyJelieta Walinski, Medicine Rock State Park, MT, USA, August 1 2022Equipment: ZWO ASI2600MCPRO camera, Celestron Nexstar Evolution 9.25 235mm f/10 Schmidth Cassegrain, Sky Watcher EQ-6R PRO mount
Andromeda GalaxyHerschel, Planck, IRAS, COBE, 16 June 2022CREDIT: ESA/NASA/JPL-Caltech/GBT/WSRT/IRAM/C. Clark (STScI)
The Andromeda GalaxyDrew Evans, Flagstaff, Arizona, USA, November 2021Equipment: ZWO ASI2600MM Pro camera, William Optics GT81 refractor, Celestron CGX-L mount
A cropped image of M31 taken with the AA24CFX camera and a Sky-Watcher Esprit 150ED refractor, using 3 hours of 10’ and 15’ exposures. Credit: Tim Jardine
The Andromeda GalaxyPaul Gordon, Rochford, Essex, 1 and 3 October 2021Equipment: ZWO ASI533MC camera, William Optics Zenithstar 73 apo refractor, Sky-Watcher HEQ5 Pro mount
The Andromeda Galaxy in ultraviolet, GALEX, 18 JULY 2021. IMAGE CREDIT: NASA, JPL-Caltech, GALEX
The Andromeda Galaxy Lloyd Mainwaring, Barry, 9 October 2020. Equipment: Canon 600D DSLR, William Optics GT81 apo refractor, Sky-Watcher HEQ5 mount.
An image of the Andromeda Galaxy taken using an iOptron SkyTracker and Canon 700D EOS DSLR camera with 135mm lens, made from a stack of 20x 30” exposures. Credit: Stuart Atkinson
The Andromeda Galaxy Vicki Pink, Southampton, 21 September 2020. Equipment: Altair Hypercam 183C camera, Sky-Watcher 72ED Evostar refractor, Sky-Watcher HEQ5 Pro mount
The Andromeda GalaxyJames Downey, Ongar, Essex, 18 August and 9 September 2020Equipment: ZWO ASI 533MC-Pro camera, William Optics RedCat 51 apo refractor, Sky-Watcher Star Adventurer Pro mount
The Andromeda Galaxy Kush Chandaria, remotely via Telescope Live, IC Astronomy Observatory, Spain, 24 July 2020. Equipment: FLI PL16803 mono CCD camera, Takahashi FSQ-106EDX4 apo refractor, Paramount MX mount
The Andromeda Galaxy Tom Howard, Isle of Wight/Crawley, December 2018 and August 2020. Equipment: Nikon D7000 DSLR camera, TS-Optics 65mm quadruplet refractor, Sky-Watcher EQ6 mount
The Andromeda Galaxy. Credit: Bernhardt Gotthardt / CCDGuide.com
The Andromeda Galaxy Nishant Revur, Washington, USA, 19 June 2020. Equipment: ZWO ASI 294MC Pro colour camera, William Optics RedCat 51 apo refractor, Celestron Advanced VX mount
A Perseid meteor seen near the Andromeda Galaxy (the bright smudge on the left of the image, Rocky Mountain National Park, Colorado, US, 12 August 2018. Credit: STAN HONDA/AFP via Getty Images
The Andromeda Galaxy, captured from the Brecon Beacons. Credit: Martin Griffiths
Andromeda GalaxyNick Berry, Gloucestershire, 25 December 2019 Equipment: Canon 650D DSLR camera, SkyWatcher 72ED refractor, SkyWatcher HEQ5 Pro mount
An image of the Andromeda Galaxy by NASA’s Galaxy Evolution Explorer. – NASA/JPL-Caltech – https://images.nasa.gov/details-PIA15416.html
M31 Andromeda Galaxy Tom Mogford, Goult, France, 20 August 2018. Category: Young Astronomer (highly commended). Equipment: Canon 750D DSLR, Sky-Watcher Esprit 80ED triplet apo refractor, Celestron AVX mount.
Andromeda Galaxy Raul Villaverde Fraile, Ocentejo, Castile-La Mancha, Spain, 12 August 2018. Category: Galaxies (highly commended). Equipment: Canon 550D camera DSLR Takahashi FSQ 106ED apo refractor, Sky-Watcher EQ6 mount.
NASA’s Wide-field Infrared Survey Explorer detects dust in the Andromeda galaxy’s spiral arms.
This image of the Andromeda Galaxy, M31, shows you the quality and detail that can be achieved with a CMOS camera. Credit Gary Palmer
The Andromeda Galaxy. Credit: Charles Thody
The Andromeda Galaxy imaged by Peter Kurucz, Wurmberg, Germany, 9 September 2018.Equipment: ZWO ASI1600 mono camera, homemade 8-inch Newtonian, Sky-Watcher EQ6 Pro SynScan mount, Astronomik HaLRGB Filter set.
The sharpest ever view of part of the Andromeda Galaxy. – NASA, ESA, J. Dalcanton (University of Washington, USA), B. F. Williams (University of Washington, USA), L. C. Johnson (University of Washington, USA), the PHAT team, and R. Gendler
The Andromeda Galaxy, M31. Despite being our nearest galactic neighbour, its stars are only resolveable through a telescope, reminding us of the vastness of the Universe.Image credit: NASA/JPL-Caltech