50 Fun Facts About Sirius

In which constellation is Sirius the brightest star?

Its formal designation is Alpha Canis Majoris.

What is Sirius's popular nickname?

Canis Major and Canis Minor are pictured following Orion the hunter across the sky.

What does the Greek word behind the name Sirius mean?

Its earliest recorded use is in Hesiod's Works and Days in the 7th century BC.

Which star is the second-brightest in the night sky, roughly half as bright as Sirius?

Canopus is a distant supergiant, whereas Sirius owes its brilliance mostly to being close.

Roughly how far from Earth is the Sirius system?

It contains two of the eight nearest stars to the Sun.

What kind of object is Sirius B?

It is nicknamed the Pup and was once the more massive of the pair.

How long do Sirius A and B take to orbit each other?

Their average separation of about 20 AU is roughly the Sun-Uranus distance.

Which astronomer deduced in 1844 that Sirius had an unseen companion?

He read the wobble in the star's path across the sky.

Who first observed Sirius B, in January 1862, while testing a new telescope lens?

The 18.5-inch refractor he was testing was then the largest telescope in the United States.

For which observatory was the 18.5-inch refractor that revealed Sirius B built?

The sighting was confirmed with smaller telescopes that March.

Who observed the spectrum of Sirius B in 1915 and showed it was a faint white star?

That made it the second white dwarf ever identified, after 40 Eridani B.

Roughly what is the diameter of Sirius B?

Packing a solar mass into an Earth-sized ball makes it one of the most massive white dwarfs known.

Which Egyptian goddess was identified with Sirius?

She was later merged with Isis, while her husband Sah, the constellation Orion, was linked to Osiris.

Which annual event did the heliacal rising of Sirius herald in ancient Egypt?

At Cairo the rising fell on 19 July in the Julian calendar, just before the flood.

How long was Sirius absent from the Egyptian sky each year, seen as an underworld journey?

Egyptian mummification traditionally took the same 70 days.

How long is a Sothic cycle, after which Sirius's rising realigns with the civil calendar?

The 365-day civil year drifted a quarter-day a year against the star's rising.

Which season's 'dog days' did the ancient Greeks tie to the reappearance of Sirius?

Anyone suffering its effects was said to be star-struck, astrobólētos.

Which animal did the Romans sacrifice to Robigo at the heliacal setting of Sirius?

The English phrase dog days is a direct translation of the Latin dies caniculares.

Which Aegean island's people sacrificed to Sirius and Zeus for cooling breezes?

Third-century BC coins from the island show dogs and stars with radiating rays.

Which season did the rising of Sirius mark for the Māori, who called it Takurua?

In Hawaii its culmination at the winter solstice was celebrated under the name Ka'ulua, Queen of Heaven.

Which Pacific archipelago at 17°S sits directly under Sirius's path each day?

Polynesian navigators used bright stars as latitude markers.

In the Polynesian 'Great Bird' constellation Manu, which part did Sirius form?

The bird split the sky into two halves.

Who discovered in 1717 that Sirius and other 'fixed' stars had moved since antiquity?

Sirius had shifted about half a degree, roughly the width of the Moon.

Sirius was the first star to have its velocity measured, in 1868. Who did it?

He got the sign wrong; Sirius is actually approaching the Sun at about 5.5 km/s.

Which ancient astronomer described Sirius as reddish in his Almagest?

Chinese records consistently called Sirius white, and the redness is best explained by atmospheric effects near the horizon.

Which two stars join Sirius to form the seasonal triangle seen on northern cold nights?

Procyon, at 5.24 light-years from Sirius, is its closest large neighbour.

North of which latitude can Sirius not be seen at all?

South of 73° S it never sets, making it circumpolar there.

Around what year will Sirius become the southern pole star?

It will come within 1.6 degrees of the south celestial pole.

Which star will eventually replace Sirius as the brightest in Earth's night sky?

Sirius is currently drawing nearer and will peak at magnitude -1.68.

Roughly how much more luminous than the Sun is Sirius A?

It is about twice as massive as the Sun with a surface near 9,940 K.

Which spacecraft is expected to pass within 4.3 light-years of Sirius in the far future?

It is the only probe to have visited Uranus and Neptune.

Which name did Chaucer use for Sirius in his Treatise on the Astrolabe?

The name comes from Arabic and was common on medieval European astrolabes.

Which Norse trickster is Sirius named after in the Scandinavian name Lokabrenna?

In Sanskrit it is Mrgavyadha, the deer hunter, representing Rudra.

Which West African people were said to hold impossible knowledge of Sirius's companion?

Doubts have been raised about the work of anthropologist Marcel Griaule, whose reports started the claim.

Which star was the first of Sirius B's stellar type to be identified, in 1910?

White dwarfs are held up by electron degeneracy pressure, as Chandrasekhar showed in 1931.

Which US broadcaster took its name in November 1999 from the brightest star in the sky?

It merged with XM in 2008 to form SiriusXM.

Which Harry Potter character named after the star turns into a huge dark dog?

He is Harry's godfather and the title prisoner of Azkaban.

Sirius A is classed as an Am star. What does its spectrum show an excess of?

Sirius B may have dumped enriched material on it during its red-giant phase.

Which star was once the more massive of the pair?

The system began as two bluish stars orbiting every 9.1 years.

Which stellar association did Ejnar Hertzsprung suggest Sirius belonged to in 1909?

It may instead belong to a proposed Sirius Supercluster with Beta Aurigae and others.

Which planet always outshines Sirius as seen from Earth?

Under ideal high-altitude conditions Sirius can be seen with the naked eye in daylight.

Which star in the Greater Dog is the night sky's brightest source of extreme ultraviolet?

Ancient Chinese astronomers saw a bow and arrow spanning Canis Major and Puppis.

In Chinese astronomy, Sirius is known as the star of which 'celestial' animal?

Tiānláng sits in the Mansion of Jǐng, and the ancient Chinese saw a giant bow and arrow in Puppis and Canis Major aimed at it.

In Zoroastrian and Persian mythology, Sirius appears as Tishtrya, a divinity of what?

Tishtar survives in New Persian poetry, and the star is praised in one of the hymns of the Avesta.

Sirius is mentioned by name in which surah of the Qur'an?

The surah's title means 'The Star'; the Arabic name ash-shi'rā gave rise to Johann Bayer's old Western name Aschere.

Which avant-garde composer wrote a piece called Sirius and claimed to come from a planet there?

To him Sirius stood for 'the place where music is the highest of vibrations'.

Olaf Stapledon's 1944 novel Sirius imagines the life of what kind of title character?

The original cover used the stars of Orion to form the body of a dog with its nose pointing at Sirius.

HMS Sirius was the flagship of which famous voyage in 1788?

Seven Royal Navy ships have carried the name since the 18th century; the star also sits on Macquarie University's coat of arms.

What is the estimated surface temperature of Sirius A, a main-sequence star of early spectral type A?

The white dwarf Sirius B is far hotter still at around 25,200 K, yet is one of the most massive white dwarfs known.

Which Senegalese people call Sirius Yoonir and hold it among their most sacred stars?

The Serer religion is practised in Senegal, the Gambia and Mauritania, including by some Cangin-language speakers.