The subject of what galaxy lies closest to us (besides the Milky Way, which we live inside) is one of much debate, mostly revolving around what exactly constitutes a galaxy or not. Let’s go on a quick tour.
The majestic Andromeda Galaxy, formally recognized by its coordinates RA: 0h 42.7m; Dec: 41° 16′ north, stands as the nearest spiral galaxy to our home, the Milky Way, at an astounding distance of 2.54 million light-years. M31 is significantly larger in physical size than our own galaxy and may or may not be more massive. Not only was Andromeda the very first galaxy whose existence was proven beyond our Milky Way, but it was also the inaugural galaxy to have its distance accurately determined.
Credits: 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.
M31 hosts at least 450 globular clusters orbiting around it, compared to the paltry 150–180 or so our Milky Way has. M31 was the first galaxy proven to exist outside our own and the first to have its distance measured, and it can be seen with the naked eye or binoculars even from suburban areas. Binoculars or a small telescope will reveal M31’s companion galaxies, M32 and M110 (both are dwarf elliptical galaxies), as well as a hint of the galaxy’s dust lanes. A large telescope can show you the immense globular cluster G1, located several degrees away from M31 in the sky, as well as M31’s brightest open star cluster, NGC 206, and maybe a bit of the galaxy’s spiral arms.
However, Andromeda is not the nearest galaxy to us at all, as many objects lie quite a bit closer, though they are all quite a bit less impressive in terms of size, mass, and brightness. Still, for those dreaming of intergalactic voyages, the vastness of space poses a challenge. With our current technology, a journey to even the nearest galaxy would span millions of years, a humbling reminder of our place in the boundless universe.
Disrupted Nearby Galaxies That are Closer to Milky Way
Our Milky Way is not just a passive entity drifting in the vast expanse of space; it is an active participant in the cosmic dance that has shaped the universe’s landscape for billions of years. Throughout its existence, our galaxy has engaged in a process of consuming, or merging with, other smaller galaxies. This might sound like an aggressive act, but in the astronomical context, it is a natural and fairly common phenomenon.
Mergers and acquisitions, so to speak, have played a pivotal role in the growth and evolution of galaxies. In fact, these interactions have significantly influenced the size, shape, and overall composition of the galaxies involved. When two galaxies come close, their mutual gravitational attraction can pull them toward each other. If the conditions are right, they might merge into a larger entity. While larger galaxies like the Milky Way tend to dominate these interactions, consuming smaller dwarf galaxies, even they are not immune to being absorbed by even more massive cosmic structures.
There are several nearby objects that probably constitute galaxy fragments but are no longer actual galaxies. The closest of these is Omega Centauri, 15,800 light-years away, or about 3500 times the distance to the nearest star to us. Star clusters and curious anomalies within our galaxy provide a historical record of its growth, much like the rings inside a tree tell its age.
Omega Centauri is the brightest globular star cluster in our skies—so bright that it can be resolved into individual stars with a pair of handheld binoculars, and it is easily seen as a fuzzy patch with the naked eye. Other, dimmer globulars are also visible with the naked eye, but their non-stellar nature is not easily apparent. It has about 4 million solar masses’ worth of stars, compared to the paltry half-million or so of even the massive globular clusters like M13 and M3. The only known globular with more mass is G1, sometimes called Mayall II, a globular that orbits the Andromeda Galaxy.
Omega Centauri has an abnormal distribution of metallicity, and it appears that its stars are not all the same age, unlike most globulars, which seem to form all their stars at once. This points to it being the core of a galaxy that was consumed by our own Milky Way, which would make it the closest galaxy fragment or remnant to us.
Next up is the Canis Major/Monoceros Overdensity, also called the Canis Major Dwarf, about 25,000 light-years from our own Sun. This “object” is only visible to us as a slight increase in the stellar population (particularly red giants) concentrated in an elliptical/arc-shaped area. It is completely possible that this region is a slight overconcentration of Milky Way stars and thus a mere statistical fluke. While some debate exists about its nature, many clues hint at it being a dwarf galaxy being gradually torn apart by the Milky Way’s gravitational forces. If true, this means the Canis Major Dwarf is in the process of donating its stars and clusters to our galaxy. This “donation” might sound peaceful, but it’s the result of powerful gravitational interactions. The resultant structure, often referred to as the Monoceros Ring or Overdensity, is believed to contain remnants of this dwarf galaxy as well as several associated globular clusters.
If you do not count either Omega Centauri or the Canis Major Dwarf, the closest “galaxy” to us or our Milky Way galaxy, is the Sagittarius Dwarf Spheroidal Galaxy, 70,000 light-years away. It consists of a stream or loop of material wrapped around our galaxy roughly perpendicular to the Milky Way’s spiral arms and several globular star clusters, including Messier 54, Terzan 7, Terzan 8, Arp 2, Palomar 12, Whiting 1, Segue 1, and possibly Messier 53. As they orbit within the tidal radius of Sag dSph, they offer a glimpse into the galaxy’s past glory and its ongoing interaction with the Milky Way. The Sagittarius dSph probably started being consumed by our galaxy sometime between 300 and 900 million years ago and will probably be gone entirely in the next few hundred million years. Messier 54 and Messier 53 are the closest globulars to us that do not belong to our own galaxy, and you can clearly spot them with binoculars or a small telescope; their stars are among the only extragalactic ones you can spot individually and positively identify as not belonging to our own Milky Way.
Spiral & Dwarf Galaxies Closest to Us
Apart from a few other disputed dwarf galaxies, which may just be star clusters or are all-but-unrecognizable after encountering the Milky Way, the nearest proper galaxy is the Large Magellanic Cloud, or LMC, easily visible to the naked eye from the Southern Hemisphere and about 163,000 light-years away.
The LMC is in fact so big and bright that it easily appears as a nebulous object under dark skies in the Southern Hemisphere. The LMC’s exact structural nature is contested; it appears to have once been a dwarf spiral galaxy and still sports a faint “bar” of stars and gas as well as telltale signs of spiral arms, but is now more like an irregular galaxy. Despite making up only 1% of the mass of our own Milky Way, the LMC is home to a number of globular clusters and nebulae, which you can observe with a backyard telescope (if you are fortunate enough to live well south of the equator).
The LMC is home to the Tarantula Nebula, a jaw-droppingly beautiful star-forming region that is the most active one known. Thanks to its extremely high activity, the Tarantula happens to also be home to SN 1987A, the closest supernova observed since the invention of the telescope, and the R136 star cluster, which contains some of the most massive and bright stars known, the biggest of which is R136A1, a Wolf-Rayet star 315 times the mass and 8.7 MILLION times the brightness of our own Sun. The Small Magellanic Cloud (NGC 292 or SMC) is a bit further away than the LMC at 205,000 light-years out and is a dwarf irregular galaxy.
Another standout member of the Local Group is M33, the Triangulum Galaxy. Located about 3 million light-years away, M33 is the third-largest galaxy in the Local Group, easily visible to the naked eye or with binoculars under dark skies, though quite a bit dimmer than Andromeda. With its beautiful spiral structure, it’s a favorite target for amateur astronomers. M33 is gravitationally interacting with Andromeda, and there’s evidence of past interactions between the two.
Speaking of interactions, the future holds a grand cosmic event for our Local Group. Current data suggests that the Andromeda galaxy (M31) and the Milky Way are on a collision course. As they merge, M33, the Triangulum Galaxy, is expected to join this union, along with many small dwarf galaxies that get caught up in the mix, including the Magellanic Clouds. While the exact nature of its role is still debated, some simulations suggest that M33 will either collide with the Andromeda galaxy first or eventually merge with the combined Milky Way-Andromeda entity. This event, occurring billions of years from now, will reshape our cosmic neighborhood, birthing a new elliptical galaxy in the process.
