J. K. Rowling drew upon star lore to name some of her characters, and this seems like a great excuse to talk about a few of the sky’s wonders while also basking in literary symbolism.

Sirius Black is the “Prisoner of Azkaban,” said to be a dark wizard who killed thirteen people with a single curse. As the plot unfolds, however, he turns out to be an enemy of Voldemort, a capital fellow, and Harry’s godfather. Sirius is a bright star in a literary sense and definitely a bright star in the sky, second only to the sun in perceived brightness by us earthlings. It is the brightest star in Canis Major (greater dog constellation) and often is called the dog star. In a literary nod to this, Sirius Black can transform himself into a dog.

Astrophysically, Sirius is a main sequence star like the sun. It’s about twice the sun’s mass, but only modestly larger in size. Its surface temperature is about 9900 Kelvin, compared with 5800 K for the sun, making it a blue-white color in comparison. Sirius has a companion. First suspected by F. W. Bessell in 1944, Sirius B was observed by telescope-maker Alvan Graham Clark in 1862 as he was testing the optics of a new telescope. Sirius B (affectionately nicknamed the Pup) is a white dwarf star, no longer fusing any fuel, but gradually cooling over time.

Historically, Sirius is everywhere. As the brightest star, every culture named it and made stories about it. Egyptian astronomers looked for the “heliacal rising” of Sirius before dawn. When they could spot Sirius in the predawn sky, they knew that the Nile would shortly flood, refreshing the Nile valley’s fertile fields with new nutrients. A common American phrase, “the dog days of August” derives from this.

A region of sky containing Canis Minor and Orion, featuring also character names Sirius and Bellatrix. Somehow, J. K. Rowling passed over Betelgeuse for a character name.

Bellatrix Black Lestrange is one of the juiciest baddies in the Harry Potter series. Indeed, she murdered her cousin Sirius! Bellatrix the star marks one shoulder of Orion the hunter constellation. Occasionally referred to as the Amazon Star in Europe since the 13th century, Bellatrix also has leonine connotations, being called the “roaring conqueror” or the “conquering lion” star from older Arabic sources (see Allen’s book).

Astrophysically, Bellatrix is a barnstormer. It’s about nine suns of matter, fusing hydrogen but somewhat evolved from the main sequence. It’s huge (6x the sun), bright (9000x the sun), and hot (4x the sun’s surface temperature). It’s a good thing this beast of a star is distant. Intrinsically, it outshines Sirius by a factor of 360. Although it has begun to exhaust its hydrogen fuel, it is young, roughly 25 million years (compared to the sun’s 4,500 million).

Stepping to constellations for a moment, Orion Black is mentioned in the Harry Potter books, as is Cygnus Black, Andromeda Black Tonks, Cassiopeia Black, Draco Malfoy, and Draco’s son Scorpius. There is nothing astrophysical about constellations. They are convenient groupings of stars as seen from earth. We name them and make up stories about them because we are human. Astronomers use them as boundaries on the sky. By international convention, there are exactly 88 constellations. Each constellation outline is a jagged affair that conforms to the equatorial grid used by astronomers for sky coordinates.

The astronomical boundaries of constellation Draco, for instance, are especially torturous. But it’s still a useful shorthand to have some constellation home for every sky object. Otherwise, we’d have objects between constellations.

Draco, in particular, seems to fit the character Draco Malfoy, a particularly snaky Slytherin. Draco the constellation snakes its way between the dipper asterisms, around the little dipper, and then curls up with its head at the feet of Hercules.

Draco means “dragon.” Despite its sky position near Hercules, it seems not to be associated with his mythology. Instead, mythologists have it as the monster killed by Cadmus at the fount of Mars. Cadmus then sowed the dragon’s teeth in the ground, and they sprouted armed warriors. This story lives on in the phrase “sowing dragon’s teeth,” referring to people whose evil actions beget future evil consequences.

The remainder of the fictional Black family named after constellations aren’t as metaphorically apt as Draco. In mythology, Orion is a hunter, Cygnus is a swan, Andromeda is the chained maiden of Ethiopia, and Cassiopeia is her vain mother. Scorpius is a monstrous scorpion, the beast that slew Orion in one legend (again, see Allen).

Back to individual stars, the Black family is large. We also have Regulus Arcturus Black (both Regulus and Arcturus are stars). For true Potterheads, several other astronomically-related Blacks can be found in the family tree, such as a couple more Sirius Blacks, some Regulus Blacks, some Arcturus Blacks, Pollux Black, and Alphard Black.

RegulusThe brightest star in Leo, the lion. It is a quadruple star system! Its brightest member is a hot, evolved star about 300 times more luminous than the sun. Its closest companion is only detected through its gravity, but it is also orbited by a K dwarf and an M dwarf, both less massive than the sun.
ArcturusThe brightest star in Bootes, the herdsman. It’s an evolved star called a red giant. Slightly metal poor compared to the sun, it is also 1000x more luminous. It’s enormous in size but cool at the surface.
PolluxAlthough designated “beta Geminorum” instead of “alpha Geminorum,” Pollux is the brightest star in Gemini, the twins. It is a red giant like Arcturus, but not as extreme. It does hold the distinction of being the closest such red giant to us.
AlphardThe brightest star in Hydra, one of several celestial snakes. Called by the Arabs “the solitary one,” Alphard is about three times the sun’s mass, but also evolved to a red giant like Arcturus, but not deficient in metals.
Pleiades star cluster.
The Pleiades star cluster, with star Merope marked. The “fluff” is what astronomers call a reflection nebula. Dusty gas mixed with the stars reflects starlight to us.

The Pleiades, or “seven sisters” is a nearby star cluster about 100 million years old. One of the stars, Merope, was used to name Merope Gaunt, the mother of Tom Riddle, who eventually styled himself Lord Voldemort and caused considerable havoc before he came, as Lucius Malfoy put it, to a sticky end.

NASA’s DISCOVR mission snapped this series of images showing the side of the moon we earthlings don’t see. The actual name of the moon is Luna.

And, finally, one of my favorite characters is Luna Lovegood, a whimsical personality even more quirky than typical Harry Potter characters.

Luna is the name of the moon used by astronomers. Cynthia and Selene have also been used by past writers. Luna is the root of lunatic, meaning crazed, and it is almost certainly this connotation that informed J. K. Rowling’s name choice for the (barking mad) Luna Lovegood.


Star Names, Their Lore and Meaning, by Richard Hinckley Allen, 1899, reprinted by Dover Publications, New York, NY 1963.

Also, Wikipedia and an old Decoded Science post.

I might have missed a character or two. Did I? Let me know.

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