Astrology in Harry Potter: the stars behind the names

The Black family is named after the night sky, the books are sharper about divination than they get credit for, and I've thought about this more than is dignified.

9 min read · Published 16 August 2026

In one paragraph

The Black family are named almost entirely after stars and constellations: Sirius is the brightest star in the sky and is in Canis Major, the great dog, which matches his Animagus form; Regulus is the brightest star in Leo and means 'little king'; Bellatrix is a bright star in Orion whose name means 'female warrior'; Draco, Andromeda and Cygnus are constellations. The books also take a sceptical position on Divination: Hogwarts teaches it, most of the sympathetic characters think it's nonsense, and the two real prophecies arrive from someone who isn't performing.

The Black family sky

I'd argue the naming is the best joke in the series, and it's a slow one. A pure-blood family obsessed with lineage names its children after fixed stars, the things in the sky that never move, and the family falls apart anyway.

Name	What it is in the sky	The fit
Sirius	The brightest star in the night sky, in Canis Major, the Great Dog	His Animagus form is a large black dog. Sirius is called the Dog Star.
Regulus	The brightest star in Leo; the name means 'little king'	The younger brother, who dies doing something quietly kingly.
Bellatrix	A bright star in Orion; the name means 'female warrior'	Voldemort's most committed fighter.
Draco	A constellation winding around the north celestial pole; the dragon	A Slytherin heir, in a house whose sigil is a serpent.
Andromeda	A constellation, and the galaxy within it; a princess in Greek myth	The sister who leaves the family: chained to a rock in the myth, rescued out of it.
Cygnus	The swan, a northern constellation containing Deneb	A recurring Black family name across generations.
Arcturus	The brightest star in Boötes, fourth brightest in the sky	Another recurring family name.
Alphard	The brightest star in Hydra; the name means 'the solitary one'	The uncle who was disowned: struck off the family tapestry, alone.

Alphard is the one that rewards attention. Its name means the solitary one, and the character it belongs to is the relative blasted off the family tree for helping Sirius. Nobody arrives at that by accident, and I'd stake a lot on Rowling having a star atlas open.

Several of these are in AsterNym's star catalogue as real objects with real coordinates. Sirius, Regulus, Bellatrix and Deneb are all bright enough to find on your first night out, which is more than most fictional families give you.

Why so many of those names are Arabic

Aldebaran, Altair, Deneb, Alphard, Rigel, Betelgeuse: a striking share of bright-star names in any European catalogue come from Arabic, and the Harry Potter names inherit that.

The reason is historical. Astronomers in the Islamic world did much of the careful cataloguing during the ninth and tenth centuries, and those names passed into Latin and then into English. Alphard is from *al-fard*, the solitary one. Deneb is from *dhanab*, tail, and it sits in the tail of the swan. I cover that history properly in astrology in Islam.

Rowling's sky names are the best thing in the books' worldbuilding, and I'd forgive Divination class for them.

What the books say about Divination

This is the part everyone misses, and it's sharper than the merchandise suggests.

Divination is taught at Hogwarts and treated by most of the sympathetic characters as rubbish. Hermione walks out. McGonagall is openly dismissive. The teacher spends years predicting Harry's death, incorrectly, every term. The students pass by inventing tragic-sounding predictions the night before, and it works, which is the funniest thing in the books about how horoscopes get written.

And yet two real prophecies occur, both from the same person, both delivered in a trance she can't remember, neither during a lesson. The structure is deliberate: the performance of divination is mocked throughout, and the real thing arrives unbidden from someone who isn't trying.

Whatever you think of astrology, that's a well-made distinction. It separates the ritual from the claim, which is roughly the distinction this whole journal keeps insisting on, and I'd argue a children's book made it more cleanly than most astrology books manage.

The centaurs read the sky differently

The centaurs are the books' real astrologers, and their method is nothing like a birth chart. They watch planetary movement over long periods and speak in decades and eras rather than individuals. Mars being bright tonight means war is coming, not that you'll have an argument.

They're also contemptuous of human divination, and specifically of reading the sky for personal fortune, which they treat as a trivial misuse of something vast. When Firenze takes over the Divination class he tells the students almost nothing about their own lives, and that's the point of the character.

It maps onto a real distinction. Mundane astrology, reading the sky for nations, eras and collective events, is a real branch and much older than the personal birth chart, which became the dominant form late. I'd argue the centaurs are the only characters in the series who practise astrology the way the Babylonians did.

Centaurs are themselves a constellation, Centaurus, which contains Alpha Centauri, the closest star system to the Sun.

The midwinter mistake

The books' sharpest joke about astrology is a small one. In the first Divination lesson, the teacher studies Harry and announces that he was born in midwinter. He was born on the thirty-first of July. She does not pause, and the lesson continues, and the reader has been shown in one exchange how a confident reading survives being wrong: nobody corrects her, and the next prediction arrives before the last one has been checked.

The same lesson has her reading tea leaves and finding the Grim, the death omen, in Harry's cup. The Grim is a large black dog who is his godfather, which is the book's other joke about omens: the sign was real and the reading was backwards. I have thought about that scene more than I have thought about some real astrology books, and it holds up better than most of them.

The Moon, the werewolf and the timetable

The third book runs on the lunar calendar without saying so. A character who becomes a wolf at every full moon has to be absent from lessons on a schedule, and the plot's key night is a full moon rising over the grounds at the wrong moment. Readers who checked found the phases were not kept consistently across the book, which is fair, because the author has said she did not track them. It is still the only children's novel most people have read in which the Moon's phase is a plot mechanism, and it sends a certain kind of child to a lunar calendar for the first time.

The Astronomy lessons are the other place the real sky appears. Fifth-year students sit their Astronomy practical at midnight on the tower, charting positions through telescopes while, below them, something happens in the grounds that they cannot look away from. The exam is the one part of the magical curriculum that is simply science, and the book treats it as hard.

What the books did to baby names

Luna was a rare name in English-speaking countries before 2003 and is now among the most common girls' names in the United States, Britain and much of Europe. The books are not the only cause, but the timing is hard to argue with. Sirius has appeared on birth registers where it never had. Draco has not, which tells you something about how readers judged him.

It is a small example of what the series did generally: it put a handful of real star names into ordinary use. A child called Luna is walking around named after the Moon in Latin, and if she asks why, the answer leads to a night sky. That is more than most fiction manages.

Finding the Black family tonight

Sirius. Follow the three stars of Orion's belt down and to the left, and the brightest star you reach is it. Winter evenings in the northern hemisphere; it twinkles in colours when low.
Bellatrix. The upper right shoulder of Orion, opposite the red star Betelgeuse. Same nights.
Regulus. The bright star at the bottom of the backwards question mark that forms the Lion's head, high in spring evenings.
Arcturus. Follow the curve of the Plough's handle away from the bowl and the first bright star is it, orange and unmistakable in spring and summer.
Deneb, in Cygnus. The tail of the Swan, one corner of the Summer Triangle overhead on August nights.
Alphard. Harder: the lone bright star in a large empty stretch of spring sky below Leo, so the Arabs called it the solitary one.

All six are in the star catalogue, with rise and set times for your location, and all six were named long before anyone put them in a novel.

Other sky names in the books

Luna Lovegood: luna is the Moon in Latin, and 'lunatic' comes from the same root, which is exactly the joke about how she's treated.
Remus Lupin: lupine rather than astronomical, tied to the Moon's cycle through what he is.
Merope Gaunt: one of the Pleiades. In the myth Merope is the sister who married a mortal and whose star is the faintest of the cluster; Voldemort's mother married a Muggle.
Orion Black: the hunter, one of the most recognisable constellations, and Bellatrix's own star sits in it.

The Merope one is the deepest cut in the series. A star that dimmed because she married a mortal, given to the character whose marriage to a Muggle destroyed her. I noticed it on a third reading and had to put the book down.

Which Harry Potter characters are named after stars?

Sirius (the brightest star in the night sky, in Canis Major), Regulus (the brightest star in Leo), Bellatrix (a bright star in Orion), Alphard (in Hydra), Arcturus (in Boötes), plus constellation names including Draco, Andromeda, Cygnus and Orion. Almost all belong to the Black family.

Why is Sirius Black named Sirius?

Sirius is the brightest star in the night sky and is in the constellation Canis Major, the Great Dog. It is commonly called the Dog Star. His Animagus form is a large black dog.

Does Harry Potter take divination seriously?

Largely not. Divination is taught but treated dismissively by most sympathetic characters, and the Divination teacher's predictions are consistently wrong. The two real prophecies come in trances she doesn't remember, outside of lessons, separating the performance from the claim.

What do the centaurs believe about astrology?

They read planetary movement for long eras and collective events instead of individual fortunes, and they're contemptuous of humans using the sky for personal prediction. This mirrors mundane astrology, a real branch concerned with nations and periods instead of birth charts.

What is the midwinter joke in Harry Potter?

In the first Divination lesson the teacher announces that Harry was born in midwinter. He was born on 31 July. Nobody corrects her and the lesson moves on, which is the book's demonstration of how a confident reading survives being wrong.

Did Harry Potter make Luna a popular name?

Luna was rare in English-speaking countries before 2003 and is now among the most common girls' names in the United States and Britain. The books are not the only cause, but the timing fits, and Sirius has appeared on birth registers too. Draco has not.

Can I find Sirius tonight?

On winter evenings in the northern hemisphere, follow the three stars of Orion's belt down and to the left. The brightest star you reach is Sirius, and it twinkles in colours when low. Bellatrix is Orion's upper right shoulder, opposite the red star Betelgeuse.