The myth of the princess who paid for her mother’s mistakes, the hero who negotiated before rescuing her, and the nearest galaxy you can see tonight with your own eyes. With medieval Arab astronomy, Vedic tradition, and the most fascinating deep-sky objects of autumn.
By Juan Pablo Martin | ASTRONOMIKA TV | August 2026
The Andromeda Constellation holds two equally extraordinary stories: that of a princess who paid for her mother’s mistakes, and that of a galaxy already heading toward us for 4.5 billion years. Tonight you can step outside, find four bright stars in the autumn sky, and see with your own eyes the farthest light the human eye can reach.
But first, the story.
The day a mother sacrificed her daughter to save her ego
Andromeda did nothing wrong. That needs to be said first. She defied no god, broke no oath, made no political miscalculation. She was an Ethiopian princess living in her parents’ palace on the coast of what is now Lebanon or Israel, and the only thing she had was a beauty her mother found too good to keep to herself.
And a life that, until that moment, was looking pretty good.
Andromeda was the daughter of Cepheus, king of Ethiopia, and Cassiopeia, his queen. Cassiopeia was the kind of woman who justified her own ego. Tall, long-necked, with the bearing of a statue and a beauty that never asked permission because it never had to. Dark abundant hair she wore pinned up with the calculated precision of someone who knows exactly the effect it has when loose. Eyes that looked down at people even when she was at the same height. A body sculptors would have paid to immortalize, treated with the indifference of someone accustomed to being the most valuable object in any room.
Cassiopeia’s problem wasn’t that she was beautiful. It was that she knew it, and had always known it, with the calm of someone who has never had reason to doubt herself.
She also had the body that matched that certainty. A long neck over perfectly proportioned shoulders, a figure that royal tunics didn’t hide but framed, because Cassiopeia knew exactly what fabrics to wear and how to wear them. Not the youthful, defenseless beauty of her daughter. Something more calculated and more dangerous than that: the beauty of a woman who has had decades to perfect the effect she has on others and has used it as a tool ever since she learned it worked.
Andromeda was promised in marriage to Phineus, a man of noble blood and sufficient lineage to aspire to the hand of a princess. Phineus was, in fact, her father’s brother. Her uncle. Marriages between close relatives were common practice in ancient dynasties, a way to keep power within the family and seal alliances without ceding territory. No one at the Ethiopian court found this strange.
We do, but that’s another conversation.
What the classical texts don’t tell us is what Andromeda saw in Phineus beyond the contract. But Phineus was heir to Belus, a powerful figure in the kingdom, with command over men and resources. In the world Andromeda lived in, that was no small thing. She had probably known him her whole life. She had probably learned to see him as her future.
What Andromeda didn’t know was that future had an expiration date.
Cassiopeia, queen of Ethiopia, was a woman who confused privilege with merit. One day, in public, as a declaration of state, she opened her mouth and said what she never should have said.
According to the oldest version of the myth, left to us by the Roman mythographer Hyginus in his Fabulae, Cassiopeia proclaimed that her daughter Andromeda’s beauty surpassed that of the Nereids, the fifty sea nymphs, daughters of the god Nereus. In another equally documented version, what she proclaimed was that her own beauty was superior to theirs. Both versions say the same thing about Cassiopeia: she was the kind of person who needed everyone to know her worth. The difference is only whether she used her daughter as a trophy or simply relied on her own ego.
In either case, the result was identical.
The Nereids heard. Poseidon, god of the sea and protector of the nymphs, heard too. And Poseidon was not the type to let insults slide, especially from mortals.
He sent Cetus, the most feared sea monster of the ancient Mediterranean, to devastate the coasts of Ethiopia, in what is now the coastal strip of present-day Lebanon and Israel. Fields razed, fishermen killed, ports destroyed, ships sunk before reaching shore. An entire kingdom paying for its queen’s vanity.
Andromeda heard about all this from her palace. Picture her there: a young woman watching her world collapse because of her mother’s words. Hearing the cries of people on the coast. Watching her father pace the halls with the face of someone who doesn’t know how to fix what wasn’t his fault. Waiting for someone to do something. Looking at Phineus, her betrothed, the man with an army and the lineage to try anything, and seeing in his eyes something she didn’t expect to see.
Not decision. Not courage. Waiting.
Phineus was waiting. Calculating. Watching how things developed before committing to anything.
Cepheus, desperate, consulted the oracle of Ammon. The answer came without hesitation and without mercy: the only way to stop Cetus was to sacrifice Andromeda. Hand her to the monster. His own daughter.
And here is where the story gets truly dark, because what happened next was not the unilateral decision of a heartless father. It was something more complicated and more disturbing than that.
Cepheus came to Andromeda. He explained what the oracle had said. He told her the entire kingdom depended on what was decided in the next few hours. And in that moment, Andromeda looked her father in the eyes, looked toward the window where she could hear the sea destroying her kingdom’s coast, and made the only decision anyone in that story was capable of making.
She said yes.
Not because her parents demanded it. Not because Phineus asked her to. But because Andromeda was the kind of person who, when no one else acts, acts. Because she looked around, saw that the men who supposedly loved and protected her were paralyzed, and decided that if someone had to pay that debt, she preferred to choose it herself rather than have it imposed on her.
There is a difference between being sacrificed and deciding to sacrifice yourself. Greek texts rarely acknowledge that difference. But it was there.
The darkest decision in this saga wasn’t made by the monster or the god. It was made by a man who loved his daughter and chained her anyway. The story of the king who carried that weight has its own chapter.
And while Andromeda made that decision, Cassiopeia, who caused everything with one ill-timed ego trip, appears in no version of the myth. She simply isn’t there. She let her daughter pay the bill alone.
What followed was brutal in its simplicity.
In ancient Greek culture, sacrifice required the offering to be presented without artifice, without protection, without anything mediating between her and the will of the gods. So what followed wasn’t an accident or an excess. It was a protocol.
They stripped her of her clothes. In front of her father’s soldiers. In front of the very citizens she had decided to save. With her parents’ palace visible on the horizon and torches burning as if nothing extraordinary was happening on the shore.
And Phineus, her betrothed, the man with an army and the lineage to try anything, was there too. The texts don’t say so explicitly. But they don’t say he wasn’t there either. And if he was there, if he saw that moment and stayed where he was without moving, without protesting, without doing absolutely anything, then there is only one word to describe what Phineus really was.
He wasn’t Andromeda’s betrothed. He was a spectator.
There are silences that define a person forever. This was Phineus’s.
They left her only her princess jewelry: a golden diadem on her forehead, bracelets on her forearms, earrings that the sea breeze would later move. The only ornament they allowed her to keep was the one that reminded everyone she was someone, that she had a name and a rank, even though in that moment neither did her any good.
Andromeda didn’t bow her head. The texts don’t say that either. But every thread of this character’s narrative points in one direction: she was the kind of person who didn’t bow her head. So we imagine it that way, because it’s the only version consistent with who she was.
They chained her naked to a rock on the seashore. And the entire kingdom she had decided to save left her there and walked away.
Think about what was going through her head in that moment. The cold of metal on her wrists. The salt wind hitting her skin. The waves breaking against the rock at her feet, getting colder, getting higher. The coast of her own kingdom visible from there, her parents’ palace on the horizon, lights on, life continuing. The silence of Phineus. The absence of her mother. And the certainty, growing with every wave, that no one was coming.
She waited.
Then he arrived.
But before talking about what Andromeda saw from that rock, we need to understand who the man who appeared in the sky was.
Perseus was the son of Zeus and Danae, a mortal princess from Argos, in the south of present-day Greece. His story began long before this moment and would end long after, but what matters to understand what was about to happen on that rock is this: he had just decapitated Medusa, the only mortal Gorgon, a creature whose gaze turned anyone who looked directly at her to stone. To accomplish this, the gods had equipped him with a polished bronze shield he used as a mirror, a harpe, a sickle-shaped sword forged from adamantine, the hardest metal in the cosmos, winged sandals, and a leather bag to carry what he cut. He was flying back over the Mediterranean when he looked down.
Where exactly he came from, what else he had done before this moment, and what would happen after, that has its own chapter. The full story of Perseus begins long before this rock.
Now then. Let’s be honest with the story and with ourselves.
Perseus had faced Medusa without blinking, had crossed the edge of the known world without hesitation, had carried a gorgon’s head in a bag like it was nothing. By any reasonable measure, he was the bravest man of his generation.
But he had also spent weeks completely alone at the edges of the world. No city, no palace, no conversation that wasn’t with monsters or gods.
Greek heroes had a very strict code of honor. But they also had eyes. And Perseus, demigod or not, was still a man in his mid-twenties with all the consequences that implies. Calling what he felt in that moment “additional courage” would be technically accurate. The Greeks simply called it Eros, the god who doesn’t ask permission from anyone, not even the sons of Zeus.
“Boys will be boys.” Even when the boy is the son of Zeus.
What he saw from the sky was this: Andromeda chained to the rock, naked except for her jewelry, arms raised above her head, her body lit by the Ethiopian afternoon sun. And the gaze. Open. Eyes not closed. The gaze of someone who had made a decision and was already on the other side of it.
That was what finally decided Perseus. Not just the beauty, though the beauty was there and was impossible to ignore. It was that: the gaze.
Perseus descended on Pegasus. The white horse with enormous wings spread to the sides cut through the air with the silent precision of something that doesn’t belong completely to any world. Andromeda raised her eyes and saw a figure coming down from the sky, a man in armor, mounted on something that shouldn’t exist but did.
Perseus landed on the rock beside her. The first thing he did was talk to her. With genuine curiosity. Who are you, why are you here, what did they do to you. And Andromeda told him everything: her mother’s vanity, the oracle, her father’s decision, Phineus’s silence. Perseus listened. Which was also something no one had done that day.
Then he did something Andromeda didn’t expect: before rescuing her, he flew back to the shore where Cepheus and Cassiopeia were and negotiated the marriage. He closed the deal first.
Yes, that’s also true. Perseus was a hero, not a saint. And Greek heroes didn’t do anything without calculating the outcome.
Andromeda was still chained to the rock while the adults closed the deal on the shore. The sea at her feet sounded different now, deeper, as if something large was moving beneath the surface. The time it took Perseus to return from the shore must have been the longest of that entire endless day. The fear that her parents might say no. That the deal might fall through. That this extraordinary moment might evaporate and leave her alone again with what was coming from the depths.
But the parents accepted. Of course they did.
Perseus returned.
And then the sea opened.
Cetus emerged from the depths with the slowness of something that has no hurry because nothing in the ocean dares to challenge it. A dark enormity advancing the way things advance that live where no light reaches, where the water pressure crushes anything not born specifically to withstand it.
Andromeda watched it coming from the rock. The water at her feet changed color first, from blue to dark green, as if something very large was pushing the ocean floor upward. Then the sound, a deep movement that wasn’t a wave because it came from too far below. Then the shadow, enormous, under the surface, advancing directly toward where she stood.
The classical texts don’t describe what Andromeda felt in that moment. But one thing we do know: she didn’t look away.
And while Cetus advanced and Perseus launched to intercept it, Andromeda did the only thing she could do: stay on that rock and want with every bit of strength she had left for the man who had come down from the sky for her to win.
Perseus acted before Cetus reached the rock. The versions of the myth don’t agree on the exact method. Some say he used Medusa’s head to petrify the monster before it arrived. Others say he faced it with the harpe directly, using the shield’s reflection to orient himself in combat. Ovid places him fighting on top of the monster, in the water, during what must have been several minutes of real combat.
He probably used everything he had. That was Perseus’s style.
When the water calmed and Cetus stopped moving, there was a moment of absolute silence over the Ethiopian sea. The kind of silence that only exists after something very large ends once and for all.
Perseus returned to the rock. Soaked, his bronze breastplate darkened by seawater, the harpe still in hand. He stood before her.
Him, covered in bronze and leather and sea. Her, with nothing except her jewelry and that gaze. Both at the same height for the first time, face to face on that rock, with the still water below and the afternoon sky lighting up behind them.
With the same hand that had just killed Cetus, he broke the chains.
The metal fell into the sea.
That first second of freedom has a very specific physicality: the sudden weight of the arms coming down, muscles burning after hours of tension, the strange and wonderful sensation of the body remembering it has gravity. Wrists marked by the shackles. Air filling the lungs differently.
Andromeda lowered her arms. She looked at him. With the same open gaze with which she had faced the horizon all day. Except now the horizon had another face.
Sometimes opposites don’t cancel each other out. They complete each other.
As for what happened next, before returning to the shore where her parents waited, let’s say that Perseus’s bronze armor turned out to be, in that specific moment, considerably less relevant than it had been an hour before. The Greeks understood that there are moments that belong to the people living them, not to those who tell them afterward.
What we do know is that when they arrived at the shore, they arrived together.
The wedding was celebrated in Ethiopia that same night. And it was, to put it delicately, memorable.
Because in the middle of the banquet, when the food was served and the wine had circulated enough times, the doors of the hall opened and in walked Phineus.
The betrothed who hadn’t lifted a finger when Andromeda was chained to the rock. The man who had waited to see how things developed before committing to anything. The uncle claiming what he considered his now that the danger had passed and someone else had done the work.
He arrived with an armed army, claiming Andromeda as his original betrothed.
It was Cepheus himself who confronted him first. And the words he said were recorded in Ovid’s Metamorphoses with a precision that still stings: “Why didn’t you take her off the rocks where she was chained? The prize is now claimed by the man who stood watching while an old father nearly lost his daughter?”
Phineus didn’t respond with words. He threw a spear.
Chaos erupted in the wedding hall. Torches swayed, tables flew, cups rolled across the floor mixing wine with blood. Phineus’s men were many. Perseus was one. But Perseus had killed Medusa with a mirror and a harpe while flying above her, so the concept of “numerical disadvantage” produced more curiosity than fear in him.
Perseus, outnumbered but not out-resourced, did what only he in all of Greek mythology could do in that moment: he opened the bag.
He first warned those on his side to look away. And then he raised Medusa’s head.
Phineus and all his men turned to stone in the middle of the wedding hall. Some with their cup still in hand. Some with their sword raised. Some with their mouths open mid-sentence, a phrase they never finished.
The bride’s uncle, turned to statue at his own wedding protest, surrounded by his petrified army. Forever.
Andromeda had started that day naked and chained to a rock, waiting for a sea monster to end everything. She ended it also naked, but on her wedding night, beside the only man who that day had bothered to come down from the sky for her. If that isn’t a narrative arc, I don’t know what is.
And here comes the detail that makes this story different from almost everything else in Greek mythology, because happy endings there are a statistical rarity. The Greeks believed life had a natural tendency toward tragedy. Oedipus discovered he had killed his father and married his mother. Achilles chose short glory over a long life and died young. Heracles, the most powerful of all, ended his days burning in a poisoned tunic.
Andromeda and Perseus went to Argos, in the Peloponnese, in the south of present-day Greece, and reigned together. They had seven children. They built something. They grew old.
When they died, the goddess Athena placed them together among the stars, so they could be eternally close to one another in the northern sky. Not as punishment, not as a warning, not as a reminder of some excess of pride committed. Simply so they could stay together.
If this story sounds like something that should have music, at ASTRONOMIKA BEATS we turned it into exactly that. “La princesa encadenada” (The Chained Princess), from the album “Historias en las Estrellas” (Stories in the Stars), is the musical version of what you just read. Find it on Spotify.
The woman no one defended, who made the only decision anyone else in that story was capable of making, who endured chained and naked on a rock before the sea while waiting for something she had no objective reason to expect, ended up being the only person in this entire story who truly chose her own destiny.
In Greek mythology, that is the closest thing to justice you will find.
Cassiopeia also ended up in the sky. But she spins eternally around the north pole, sometimes upside down, unable to rest. And the most disturbing thing isn’t the punishment. It’s that in no version of the myth, in no surviving Greek text, does she ever ask for forgiveness. Not once.
That one also has its own chapter.
But the Greeks weren’t the only ones who looked at this corner of the sky and found something extraordinary. Thousands of kilometers away and centuries apart, other civilizations raised their eyes toward the same stars and saw completely different worlds.
The same sky, three completely different stories
The astronomer who saw M31 first and didn’t know what it was
In the year 964 AD, in the city of Shiraz, in present-day Iran, a Persian astronomer named Abd al-Rahman al-Sufi finished writing one of the most important books in the history of astronomy: the Kitab suwar al-kawakib, the Book of Fixed Stars.
Al-Sufi was the kind of scientist the centuries produce very rarely. Meticulous, obsessive, with the patience of someone who can spend years staring at the same patch of sky without getting bored. He took Ptolemy’s star catalog, reviewed it entirely, corrected what was wrong, and added what was missing. Every star had its position, its brightness, its name in classical Arabic. A life’s work condensed in a single volume.
And at some point in that work, while tracking the region of sky the Greeks called Andromeda, Al-Sufi noted something he didn’t know how to classify.
He called it sahabet al-leil. The little night cloud.
It was M31. The Andromeda Galaxy.
He didn’t know what it was. Nobody in the world did yet. He didn’t have the vocabulary to describe it because the concept of galaxy wouldn’t exist for nearly a thousand more years. But he saw it, drew it with enough precision for modern astronomers to identify it without any doubt, and recorded it in his book as a real object worth documenting even if it couldn’t be explained.
That’s what a good scientist does: document what they see even if they can’t explain it yet.
The Arabic names that Al-Sufi and his predecessors gave to the stars of Andromeda are the same ones we use today. Alpheratz comes from the Arabic surrat al-faras, the navel of the horse, a star the Arabs shared between Andromeda and Pegasus because geographically it belongs to both. Mirach comes from al-maraqq, the flank. Almach comes from al-anaq al-ard, the badger.
Each name is a coordinate in a celestial navigation system that worked for centuries, long before telescopes or satellites or astronomy apps on phones existed.
Where the Greeks saw the drama of a dysfunctional family, Arab astronomers saw a precision map and a mysterious cloud that didn’t fit anything they knew. Two completely different ways of looking at the same sky. Both equally valid. Both equally fascinating.
And while Al-Sufi documented with a scientist’s precision, on the other side of the world a completely different system of knowledge was looking at the same stars and finding something that had nothing to do with clouds or maps.
The serpent that sleeps where the stars end
In ancient India, Vedic astronomers divided the sky in a completely different way from the Greeks and Arabs. Instead of constellations, they used lunar mansions: 27 regions of the sky that the Moon traverses over its monthly cycle. They called them nakshatras.
The 26th mansion was called Uttarabhadrapada, which in Sanskrit means something like “the auspicious feet.” Its two main stars are Gamma Pegasi and Alpha Andromedae, exactly the ones that today mark the corner of the Square of Pegasus and the head of the Andromeda constellation.
The Vedic seers looked at those two stars and didn’t see a princess. They saw the hind legs of a funeral bier, a symbol of transformation and passage between worlds. The threshold between what exists and what comes after.
And the deity governing that nakshatra was Ahirbudhnya, pronounced roughly “ah-heer-bood-nyah,” and which, it must be said, the Vedic texts themselves never bothered to make famous.
The Sanskrit name says it all: ahi means serpent, budhnya means bottom or depth. Ahirbudhnya is the serpent that lies beneath the surface of the earth, in the primordial depths where no light reaches and where the Vedic texts suggest the oldest mysteries of the cosmos sleep.
Now then. Here comes the interesting part, or rather, the part where the lack of information itself becomes fascinating.
Ahirbudhnya appears exactly twelve times in the entire Rigveda, one of the most extensive and detailed texts of antiquity. Twelve. In a book with more than ten thousand verses. And in none of those twelve mentions does it appear as the protagonist of anything. Always in lists, always in passing, always alongside other gods who do have epic stories, battles, romances, and betrayals.
Academics who have spent centuries studying Vedic texts basically shrug when someone asks about Ahirbudhnya. The little the texts say is that it was born in the waters, lives at the bottom of cosmic rivers, and that the faithful invoked it asking it not to harm them. That last part is particularly revealing: they didn’t ask for favors, didn’t ask for prosperity or love or victory in battle. They asked it to simply leave them alone.
It is the most mysterious deity in the Vedic pantheon not because its stories are complicated but because it apparently has none. Or if it does, someone decided three thousand years ago it was better not to write them down.
And that, paradoxically, makes it more unsettling than any story they could have invented for it.
The Greeks placed a chained princess in this corner of the sky and built around her a five-character family drama complete with sea monster. The Vedic seers looked at the same stars and placed there an entity so ancient and so dark that they didn’t even bother to give it a story. They just asked it, very respectfully, not to do anything bad.
What none of them anticipated, not the Greeks, not Al-Sufi, not the Vedic seers, is what the Andromeda Constellation holds in its interior. Something that makes Cassiopeia’s family drama seem, with all due respect, like a minor matter.
The neighboring galaxy already on its way and visible tonight
M31, the Andromeda Galaxy. The neighbor that won’t stop approaching.
M31, the Andromeda Galaxy, has approximately one trillion stars. To put that in perspective: the Milky Way, our galaxy, has between 200 and 400 billion. M31 doubles it. It is the largest spiral galaxy in the Local Group, the cosmic neighborhood we live in, and it is already traveling toward us at 110 kilometers per second. To calibrate that speed: it’s like covering the distance from New York to Los Angeles in about 40 seconds, without stopping, for billions of years.
In approximately 4.5 billion years, M31 and the Milky Way will merge.
It won’t be a violent collision like the word “merge” suggests. The space between stars is so enormous that the odds of two stars colliding directly are almost zero. It’s more like mixing two clouds of smoke than a train crash. But the result will be a completely new elliptical galaxy that astronomers have already given a provisional name: Milkomeda. And the night sky of Earth billions of years from now will be completely unrecognizable.
Our descendants, if there are any, will see something from Earth that no human has ever seen.
The most disturbing fact: when you look at the Andromeda Galaxy tonight, you are not seeing M31 as it is now. You are seeing light that left there 2.54 million years ago. At that moment, the first members of the genus Homo, our direct ancestors, were already walking on Earth. Agriculture was still 2.53 million years away. That light left the Andromeda Galaxy when the first human beings were just beginning to form on our planet, traveled all that time through intergalactic space, entered Earth’s atmosphere, passed through your pupils, and ended up on your retina. You are the end point of that light’s journey.
When and from where to see it:
In the northern hemisphere, the Andromeda Galaxy is prominent from August to January, peaking in autumn. In October it reaches nearly the zenith at midnight from Mexico and Central America. In November it can be seen well from nightfall without waiting until midnight.
From the southern hemisphere the situation changes. The Andromeda Constellation is visible only north of 40 degrees south latitude. From Mexico City, Bogota, Lima, Caracas, or San Jose de Costa Rica it’s easy to see. From Buenos Aires or Santiago it’s also visible, but lower on the northern horizon and for fewer hours per night.
How to find it:
Look for the Great Square of Pegasus: four bright stars forming a large square toward where the Sun sets in autumn. From the upper left corner of the square, follow a chain of stars toward the northeast. The second bright star in that chain is Mirach, an orange-tinted red giant. From Mirach, move perpendicularly northward two star-hops. One hop equals roughly the width of your closed fist held at arm’s length, which covers about 10 degrees of sky. It’s the same tool navigators have used for centuries and requires no equipment at all. There you’ll find M31, the Andromeda Galaxy: a blurry elongated smudge, like a brushstroke of diffuse light, best seen by not looking directly at it but slightly to the side. That trick is called averted vision and it works because the most light-sensitive receptors are at the edges of the retina, not the center.
With the naked eye under a dark moonless sky, the Andromeda Galaxy appears as a faint but unmistakable oval smudge. It is the farthest object the human eye can reach unaided.
The next level reveals what the naked eye cannot. With the ZWO Seestar S50 (Mexico | United States | Spain), the experience changes completely: in a single night of image stacking it reveals the spiral structure of M31, the dark dust lane crossing its disk, the luminosity differences between the compact core and the outer arms, and the satellite galaxies M32 and M110 as objects with their own shape and structure.
For those who want to go further, the aperture jump completely changes the experience. With the SKY-WATCHER FlexTube 300P (Mexico | United States | Spain), M31’s outer halo starts becoming visible on nights of excellent transparency, along with regions of higher stellar density in the spiral arms. It is one of those objects that grows with every millimeter of aperture you give it.
M32 and M110. The companions nobody mentions.
The Andromeda Galaxy doesn’t come alone. It brings at least 14 satellite galaxies in its entourage. The two most accessible are M32 and M110, flanking the central core of M31.
M32 is the most compact and brightest. A dwarf elliptical galaxy orbiting so close to M31 that astronomers have evidence they collided directly in the past. Not a gentle merger: a real impact that stripped away its stellar disk and left visible scars on the structure of both. M32 survived. But it is no longer what it was.
M110 is larger and more diffuse, with an oval shape extending to the northwest of M31’s core. With the ZWO Seestar S50 after several hours of stacking, M110 begins to reveal its own internal structure. Even galaxies have scars, and with the right equipment you can see them.
NGC 404, Mirach’s Ghost. The galaxy hiding behind a star.
While looking for the Andromeda Galaxy following the star hop from the Square of Pegasus, you pass Mirach, the orange red giant that serves as a reference point. If you have a telescope, it’s worth stopping there before continuing.
Just 7 arcminutes to the northwest of Mirach, hidden behind its glare, is a dwarf galaxy called NGC 404. Astronomers call it Mirach’s Ghost, and the name couldn’t be more accurate. Mirach shines brightly enough to produce flares and reflections in the eyepiece that are constantly confused with the galaxy. For years, NGC 404 didn’t even appear on some star maps because the star’s symbol would have covered it completely.
It’s a challenging but possible object with a visual telescope. The trick is to place Mirach just outside the edge of the field of view and use high magnification to increase the contrast between the galaxy and the star’s glare. When NGC 404 appears, it does so as a round, faint disk with a slightly brighter nucleus. It looks like a ghost peering around the corner the moment the flashlight stops pointing directly at it.
The ZWO Seestar S50 handles this object well because its stacking software compensates for Mirach’s brightness more effectively than the human eye at the eyepiece.
NGC 891, the Silver Sliver Galaxy. What our galaxy looks like from outside.
3.5 degrees east of Almach, the third brightest star in Andromeda, is a galaxy that amateur astronomers know as the Silver Sliver: NGC 891.
NGC 891 is oriented almost perfectly edge-on toward us, which means that instead of seeing its spiral shape from above, we see it as a thin line of light with a dark dust lane bisecting it exactly and symmetrically down the center. It is one of the most perfect edge-on galaxies in the entire sky.
And there is a detail that makes it especially fascinating: NGC 891 is very similar to the Milky Way in size and luminosity. What you are seeing when you observe NGC 891 is, with reasonable accuracy, what our own galaxy would look like if you could step outside it and view it from 27 million light-years away. You can’t see the Milky Way edge-on from the inside. But you can see NGC 891 and get a very precise idea of what kind of galaxy you live in.
It was so visually important that when the Large Binocular Telescope at the Mount Graham Observatory in Arizona took its first test image in 2005, it chose NGC 891 as the target. When you want to prove your telescope works, you point it at the best available object.
With the ZWO Seestar S50 on a good night, NGC 891 appears as a thin needle of light with the dark dust lane already visible after several hours of stacking. With the SKY-WATCHER FlexTube 300P under a dark sky, the dust lane bisecting the galaxy is evident, and on nights of excellent transparency variations in density within that lane begin to appear.
A princess, a galaxy, and an ending worth waiting for
Andromeda has been chained in the sky for more than two thousand years, depending on who tells the story. A mother with boundless ego, a father who made the darkest decision of his life, a betrothed who chose silence, and a princess who decided for herself when no one else was capable. All of that is up there, turned into stars, every autumn night.
Tonight you can step outside, find the Square of Pegasus, follow the chain of stars to the northeast, and see with your own eyes the farthest light the human eye can reach. You don’t need a telescope. You don’t need experience. You just need a dark sky and to know where to look.
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What is the Andromeda Constellation?
The Andromeda Constellation is a northern hemisphere constellation named after the princess Andromeda from Greek mythology. It is the 19th largest constellation in the sky and is famous for containing the Andromeda Galaxy (M31), the farthest object visible to the naked eye from Earth, located 2.54 million light-years away.
Where is the Andromeda Galaxy in the sky?
To find the Andromeda Galaxy (M31), look for the Great Square of Pegasus, four bright stars forming a large square in the autumn sky. From the upper left corner of the square, follow a chain of stars to the northeast until you reach Mirach, a bright orange star. From Mirach, move perpendicularly northward two star-hops. One hop equals the width of your closed fist at arm’s length, about 10 degrees of sky. There M31 appears as a blurry elongated smudge of light.
Can you see the Andromeda Galaxy without a telescope?
Yes. The Andromeda Galaxy (M31) is the farthest object visible to the naked eye from Earth. Under a dark moonless sky away from light pollution, it appears as a faint but unmistakable oval smudge. The trick is to use averted vision: look slightly to the side instead of directly at it, because the most light-sensitive receptors are at the edges of the retina.
How far away is the Andromeda Galaxy?
The Andromeda Galaxy (M31) is approximately 2.54 million light-years from Earth. That means the light you see tonight left there 2.54 million years ago, when the first members of the genus Homo, our direct ancestors, were already walking on Earth.
Is it true that Andromeda is going to collide with our galaxy?
Yes. The Andromeda Galaxy (M31) is traveling toward us at 110 kilometers per second and in approximately 4.5 billion years it will merge with the Milky Way. It won’t be a violent collision: the space between stars is so enormous that few will collide directly. The result will be a new elliptical galaxy astronomers already call Milkomeda.
What months is Andromeda best visible in the sky?
The best time to observe the Andromeda Constellation and the Andromeda Galaxy (M31) is from August to January, peaking in October and November. In October, M31 reaches its highest point in the sky at midnight from the northern hemisphere. In November it can be seen well from nightfall without waiting until midnight.
From which countries can you see the Andromeda Galaxy?
The Andromeda Galaxy (M31) is visible from anywhere north of 40 degrees south latitude. That includes all of Mexico, Central America, the Caribbean, Colombia, Venezuela, Ecuador, Peru, and northern Brazil. From Buenos Aires and Santiago it is also visible but lower on the northern horizon. From latitudes beyond 40 degrees south it becomes very difficult or impossible to see.
What equipment do I need to observe M31?
The Andromeda Galaxy (M31) requires no equipment: it is visible to the naked eye under a dark sky. With the ZWO Seestar S50 in a single night of stacking, M31 reveals its spiral structure, dark dust lane, and satellite galaxies M32 and M110 as independent objects. With the SKY-WATCHER FlexTube 300P, the outer halo and luminosity variations in the spiral arms start becoming visible on nights of excellent transparency.
What are M32 and M110?
M32 and M110 are the two brightest satellite galaxies of the Andromeda Galaxy (M31). M32 is a compact, bright dwarf elliptical galaxy orbiting very close to M31, with evidence of having collided with it in the past. M110 is larger and more diffuse, with an oval shape visible to the northwest of M31’s core. Both are visible with the ZWO Seestar S50 in a single night of stacking.
Who discovered M31?
The Persian astronomer Abd al-Rahman al-Sufi was the first to document the Andromeda Galaxy (M31) in 964 AD, describing it as “the little night cloud” in his Book of Fixed Stars. He didn’t know what it was, but he saw it, drew it, and recorded it with enough precision for modern astronomers to identify it without doubt. It is the first documented description of a galaxy in the history of humanity.
Is Andromeda part of the zodiac?
No. The Andromeda Constellation is not part of the zodiac. The zodiacal constellations are those located along the ecliptic, the Sun’s apparent path throughout the year. Andromeda sits well north of that band, which is why Maya and Aztec cultures, very focused on the ecliptic, did not incorporate it into their main astronomical systems.
What will the sky look like when M31 and the Milky Way merge?
When the Andromeda Galaxy (M31) and the Milky Way merge in approximately 4.5 billion years, they will form a new elliptical galaxy called Milkomeda. The process won’t be violent: the space between stars is so enormous that few will collide directly. But Earth’s night sky will become completely unrecognizable, with the new galaxy dominating the horizon in all directions.
Sources and further reading
Burnham, R. (1978). Burnham’s Celestial Handbook: An Observer’s Guide to the Universe Beyond the Solar System. Dover Publications.
Al-Sufi, A. (964 AD). Kitab suwar al-kawakib (Book of Fixed Stars). Available in facsimile at the Library of Congress.
NASA/ESA Hubble Space Telescope. Images and data for M31, M32, M110, NGC 891, and NGC 404. hubblesite.org
Wilkins, J. & Dunn, R. (2006). 300 Astronomical Objects: A Visual Reference to the Universe. Firefly Books.