50 Fun Facts About Betelgeuse

Betelgeuse lies in which constellation?

It is usually the tenth-brightest star in the night sky.

What type of star is Betelgeuse?

Its spectral classification is M1-2 Ia-ab: very large, luminous and cool.

What is Betelgeuse's Bayer designation?

Bayer probably ranked it first because its variability made it rival its usually brighter neighbour.

Which star is the only one in its constellation brighter than Betelgeuse?

John Herschel nonetheless saw Betelgeuse outshine it in October 1837 and again in November 1839.

Betelgeuse's apparent magnitude varies between +0.0 and roughly what?

Its main period of variation is near 400 days.

At which wavelengths is Betelgeuse the brightest star in the night sky?

Its cool surface pours out most of its energy as heat rather than visible light.

If Betelgeuse sat at the centre of the Solar System, its surface would lie beyond which zone?

It would swallow the orbits of Mercury, Venus, Earth and Mars.

Betelgeuse's radius is estimated at between 640 and how many times that of the Sun?

Estimates vary because the star is not spherical and pulsates.

Estimates of Betelgeuse's mass range from slightly under ten to a little over how many solar masses?

Modern modelling gives 9.5 to 21 solar masses; older studies ranged from 5 to 30.

Early-2020s estimates put Betelgeuse's distance at roughly how many light-years?

That is an unusually wide uncertainty for such a nearby star; a 2020 study gave about 548 light-years.

Betelgeuse is expected to explode as a supernova most likely within how long?

Despite headlines during the 2019-20 dimming, astronomers do not think the explosion is imminent.

When Betelgeuse finally detonates, it will shine about as bright as what for more than three months?

Life on Earth will be unharmed; the star is too far for its X-rays or ejecta to matter.

Which class of supernova is Betelgeuse expected to produce?

A small dense remnant, either a neutron star or a black hole, will be left behind.

Betelgeuse is younger than how many million years?

Its huge mass made it burn through its life at a furious pace.

Betelgeuse is a runaway star ejected from which stellar association, home to the three Belt stars?

It moves through the interstellar medium at 30 km/s, pushing a bow shock over four light-years wide.

In 1920, Betelgeuse became the first star beyond the Sun to have what measured?

A six-metre interferometer mounted on the Mount Wilson telescope did it.

Which two scientists' Mount Wilson interferometer first measured Betelgeuse's diameter?

They found 0.047 arcseconds, though limb darkening left the figure uncertain.

Which star took over from Betelgeuse as having the largest angular diameter of any star except the Sun?

It is much closer, about 200 light-years away, and physically only a third the size.

Which instrument captured the first direct image of another star's disk, Betelgeuse, in 1995?

Its Faint Object Camera took the ultraviolet picture, beating ground-based interferometers.

Starting in October 2019, Betelgeuse's brightness fell by roughly what factor by mid-February 2020?

It dropped from magnitude 0.5 to 1.7, out of the top 20 brightest stars.

What is the 2019-20 episode of fading commonly called?

The star returned to normal, peaking at magnitude 0.0 in April 2023.

What did a follow-up study conclude had caused the 2019-20 fading?

Material hurled millions of miles from the star cooled into dust that blocked its light.

Infrared data showed no significant change in Betelgeuse's luminosity over how many years?

That pointed to extinction around the star rather than anything happening inside it.

What name has been proposed for Betelgeuse's candidate companion star, meaning 'her bracelet' in Arabic?

The IAU Working Group on Star Names recognised it on 22 September 2025.

The name Betelgeuse comes from an Arabic phrase meaning 'the hand of' what?

A 13th-century misreading of one Arabic letter turned Yad into Bet, giving Europe its odd name.

Betelgeuse is often mistranslated as the '___ of the central one'.

Renaissance writers read the Arabic as Baţ al-Jauzā', though the real word for armpit is Ibţ.

Which 1988 film popularised the soft-g pronunciation of the star's name?

Michael Keaton's character is spelled like the star.

Which classical astronomer described the star's colour as hypókirrhos, 'more or less orange-tawny'?

Chinese astronomers three centuries earlier recorded it as yellow, hinting it may have been a yellow supergiant then.

Which astronomer first described Betelgeuse's variable brightness, in his 1836 Outlines of Astronomy?

Aboriginal groups in South Australia had told oral tales of the variability for far longer.

Which Japanese clan adopted Betelgeuse and its red colour as its symbol?

Their rivals took the white star at Orion's foot, so the two stars faced off across the Belt like the clans in their legendary war.

The Lakota people see Betelgeuse as a chief who has lost what?

Many cultures place the star at Orion's shoulder or hand.

What is the Sanskrit name for Betelgeuse that also names a lunar mansion in Hindu astrology?

It means 'the moist one'.

What did the Inuit call Betelgeuse, a name meaning 'large star'?

From Arctic latitudes its red colour and higher position made it seem the constellation's brightest star.

Together with Sirius and Procyon, Betelgeuse forms which asterism?

It also marks the centre of the larger Winter Hexagon.

A line drawn from Orion's foot star through Betelgeuse points towards which pair of stars?

Betelgeuse, Bellatrix and Saiph make up three corners of Orion's rough rectangle around the Belt.

Which asteroid was predicted to occult Betelgeuse on 12 December 2023?

Betelgeuse lies too far from the ecliptic to be occulted by planets, but asteroids pass in front of it fairly often.

Interferometry has revealed 'hotspots' on Betelgeuse thought to be caused by what?

Each may emit 5 to 10 per cent of the star's total light, confirming Martin Schwarzschild's decades-old theory.

Betelgeuse's complex envelope of ejected material extends to roughly how many times the size of the star?

Massive stars in this late phase can shed as much as a solar mass every 10,000 years.

Research from 2012 put Betelgeuse's luminosity at around how many times the Sun's?

The figure assumes a distance of 200 parsecs, which is itself uncertain.

Betelgeuse's rotation velocity of 5.45 km/s is much slower than which other red star, at 20 km/s?

Antares is Betelgeuse's rival red star in Scorpius, opposite it in the sky.

Betelgeuse's weak magnetic field was detected in 2010 with the Bernard Lyot Telescope at which observatory?

It suggests giant convective motions can trigger a small-scale dynamo even in a supergiant.

On the main sequence, before it swelled, Betelgeuse would have been a hot star of what spectral type?

Its original composition was about 70 per cent hydrogen and 28 per cent helium, slightly more metal-rich than the Sun.

Which 19th-century astronomer used Betelgeuse as a prototype for his Class III orange-to-red stars?

His scheme predates the modern spectral classes.

Which body's Working Group on Star Names formally approved the name Betelgeuse in 2016?

It appeared in the first bulletin of approved names in July 2016.

Who published the Uranometria star atlas in 1603, giving Betelgeuse its Greek-letter designation?

He labelled it alpha even though it is usually only the constellation's second-brightest star.

Which Hitchhiker's Guide character is from 'a small planet somewhere in the vicinity of Betelgeuse'?

Two US Navy cargo ships of World War II were also named after the star.

For the Inuit, the appearance of Betelgeuse and Bellatrix high in the evening sky marked what?

That happens in late February and early March as the days lengthen.

Betelgeuse's bow shock was first imaged in which year, late because the star itself is so bright?

The shock forms as the runaway star ploughs through interstellar gas at 30 km/s.

Which 1980s researcher's team found polarisation evidence for two companion stars around Betelgeuse?

The closer suspected companion had an orbital period of about 2.1 years.

Betelgeuse marks the centre of which large seasonal star pattern?

It is also one corner of the smaller Winter Triangle, and rises in the east just after sunset at the start of each January.