Orion’s Belt: The Alluringly Famous Constellation

Orion’s Belt is one of the sky’s best-known star groupings within the constellation of Orion. You can see its three bright stars with your naked eyes, making them one of the first sightings for excited children and adults learning about astronomy.

Orion’s Belt creates a line of three stars at the center of Orion and is the constellation’s most recognizable star pattern or asterism. It represents the belt around the waist of Greek mythology’s hunter. In depictions, Orion often also has a sword hanging from his belt. And in addition, he has a club or weapon in one raised hand and either an animal hide or a shield in his other, according to the other stars’ positions within the constellation.

Orion Constellation

Since the Orion Constellation resides on the celestial equator, it is visible across the planet. Add to that its striking beauty, even when seen without a telescope, and you can understand how this star pattern inspires legends throughout human history.

Orion's Constellation
Image: NASA and Chandra

How Did Orion and Orion’s Belt Get Their Names?

Orion has origin stories in several cultures, including Greek mythology, ancient India & Egypt, and Arab countries. They recognized the star pattern as a human figure. And since Orion sits on the Celestial Equator, you can see it from many places on Earth.

Native Americans saw the pattern as a sky king shot through with an arrow (Orion’s belt.) Arabians saw the figure of a sky giant, while ancient Egyptians believed the stars in Orion’s belt were the resting place for the god Osiris’ soul.

But the current name for the constellation comes from Greek mythology about a great hunter, Orion. One story says Orion boasted about the number of animals he could kill, so the gods banished him to the skies. 

Orion chases other constellations representing animals, but he and his hunting dogs, Canis Major and Minor, can never catch them. At Orion’s feet, the dogs chase a rabbit (the Lepus Constellation.) And finally, Orion fights a bull, as represented by Taurus, a nearby constellation.

Orion and Scorpius

In addition, there are multiple legends of how Orion’s birth, life, or death led him toward an eternity in the skies. From him being the son of a widowed bee-keeper to Orion being stung to death by a scorpion, many stories exist across nearly every ancient culture.

In the scorpion version, after Orion said he would kill every animal, Gaia, the Earth Goddess, urged Scorpius the Scorpion to kill him. So Orion and Scorpius became enemies. And that’s why Zeus banned them to different portions of the skies where they could never meet. 

As a result, you won’t see these two constellations in the sky together. Scorpius sets before Orion rises and vice versa. So if you see Scorpius at its peak in July or August summer skies, you’ll know Orion will show up in the east just before the Sun rises.

Orion and Scorpius
Image: behance.net

And finally, Orion’s Belt got its name from the three bright stars in the middle of the constellation. They’ve been called an arrow, a belt, and a resting place for gods.

When Was Orion First Cataloged?

The image below depicts Orion in Johannes Hevelius’ Uranographia in 1690. But Orion’s exact origin remains unknown since the ancients knew it. In the 9th or 8th century BC, Homer mentioned Orion in connection with the star pattern, which may be one of the first recorded connections.

Image: NASA/Chandra/Uranographia

Below Orion’s belt are three stars in a curved line representing the hunter’s sword. But the middle star isn’t a star; instead, it’s a nebula. The Orion Nebula (Messier 42) is a giant stellar nursery about 25 light-years across.

Galileo cataloged the nearby Orion Nebula in 1610, and he believed that a more powerful telescope could resolve the cloudy, nebulous region within it into “groups of small stars wonderfully arranged.”

Below is his sketch of Orion’s Belt and the stars surrounding it.

Orion's Belt
Image: Octavo Corporation and Warnock Library

As it turns out, Orion’s Nebula is a massive dust and gas cloud that is a star nursery. But it can not resolve into individual stars with a better telescope, as Galileo thought. Instead, at only 1,300 light-years away, it is one of the closest nebulae to Earth, this cloudy birthplace of thousands of stars.

Gravity collapses the cloud clumps of dust and gas to squeeze them smaller, causing them to heat up. And eventually, the centers get hot enough to ignite a nuclear reaction to form a new star.

Below, NASA’s Spitzer Space Telescope uses infrared light to capture the Orion Nebula, and you know that Galileo would have loved the opportunity to see this incredible image. 

NASA’s Spitzer Space Telescope
Image:  NASA and JPL-Caltech with T. Megeath

Orion’s Belt Location

The celestial equator passes close to the uppermost star in Orion’s Belt, Mintaka. As a result, half the constellation is in the Southern hemisphere, while the other is up in the Northern one. And that makes Orion’s Belt visible from around the world.

Find it at these coordinates: Right Ascension – 05h and Declination of -05º.

And for clarity, right ascension corresponds to east and west lines, like longitude on Earth’s surface. However, right ascension measurements are in seconds, minutes, and hours because we see different parts of the sky at various times throughout the night as the Earth rotates.

Declination measurements are in units of arcseconds, arcminutes, and degrees since it tells you how high a celestial object rises in the night sky. It is more similar to Earth’s latitude. So there are 60 arcseconds in an arcminute and 60 arcminutes in a degree.

When Can You See Orion’s Belt

In the Northern Hemisphere, you can see Orion’s Belt on clear nights in winter. November to February offers the best viewing opportunities. Southern Hemisphere viewers see the Orion’s Belt best in the summertime. But it appears upside down. No matter your location, Orion’s Belt is one of the most accessible night sky objects.

The best way to find the hunter, Orion, is to look for three close together, bright stars in an almost straight row. They are Orion’s Belt. Look north to see two bright stars marking the hunter’s shoulders. And then drop your gaze to the south to see the two stars representing his feet.

The NASA illustration below shows Orion’s stars with a drawing of the Greek hunter. 

Orion's Belt
Image: NASA and STScI

To see the stellar nursery in Orion’s sword, look to the skies on clear nights in January. It will look like a fuzzy star area with binoculars or a smaller telescope.

Stars In Orion’s Belt

Like those in Orion’s Belt, massive stars are rare but have huge impacts on the galaxy around them. For example, these giants have such brightness that their radiation creates intense stellar winds. Those winds blow stellar material away from the star, altering the galaxy’s gases and changing its physical and chemical properties.

The stellar winds also impact the star’s lifecycle, as they’ll eventually strip away enough material that the star explodes into a supernova. Then only a black hole or a neutron star remains.

Before we look at the individual stars, here’s a word about magnitude. How bright a celestial object appears from Earth is called its magnitude. And the lower the number, the brighter the thing. So a star with a 0.12 magnitude appears brighter than one with a 3.2 magnitude.

Alnitak (Zeta Orionis)

Alnitak is a triple star system located at the eastern end of Orion’s belt. It is about 700 light-years distant and shines with a magnitude of 1.72. The primary star component is approximately twenty times larger than the Sun. It’s also about 10,000 times brighter and more luminous.

In addition, the primary is a second-magnitude, while its companion is a fourth-mag. They orbit one another at almost three arcseconds distance over about 1,500 years.

Alnitak comes from the Arab word “an-niṭāq,” meaning the girdle or belt. Furthermore, the Chinese name is Shēn Xiù yī meaning the “First Star of Three Stars.”

Image: Wikipedia

Alnilam (Epsilon Orionis)

Orion’s Belt’s central star is Alnilam. It is a blue supergiant about 2,000 light-years away. This star is so gigantic that it dwarfs the Sun by 40 to 44 times. Estimates also put Alnilam at 275,000 to about 832,000 times more luminous than the Sun. That makes it the fourth brightest star in Orion and the 29th brightest star in all the heavens.

Its spectrum is a stable anchor point in the spectral class B0Ia star classifications. In other words, it has set the standard for the class since 1943. Alnilam is slightly variable, with a magnitude from 1.64 to 1.74. And its spectrum varies, which scientists attribute to its losing surface mass.

You can best see this central star in Orion’s Belt on December 15th around midnight, at its highest point in the night sky. This bright supergiant serves as one of the 58 designated stars in celestial navigation.

Alnilam gets its name from the Arabic word al-niẓām, which means an arrangement or string of pearls. That seems fitting since it is the central star in the line of Orion’s belt. And the Chinese name is Shēn Sù èr or the “Second Star of Three Stars.”

Image: Wikipedia

Delta Orionis

The westernmost star in Orion’s Belt is officially designated Delta Orionis. However, it has a long history of observations, so it also goes by the name Mintaka (Arabic: manṭaqa.) The ancients knew and studied this and the other two stars in Orion’s Belt.

Delta Orionis is one of the brightest stars in the night sky, easily observable without a telescope. But it is actually a complex multiple-star system rather than a single star. This small group contains five stars within three components.

  • Delta Ori A – triple star with a vital X-ray source
  • Delta Ori B – single star with small X-ray amounts
  • Delta Ori C – single star with small X-ray amounts
Delta Orionis
Delta Ori A Star System Illustration: NASA, M.Weiss, and CXC

Interestingly, two Delta Ori A stars closely orbit one another every 5.7 days. But the third star orbits the close pair only once every 400 years. In addition, of the two close stars, the primary one has about 25 times the Sun’s mass. And the secondary star is less massive, at only about ten times the Sun’s mass.

This stellar pair is an eclipsing binary, which means from our view on Earth, one passes in front of the other during each orbit. And that eclipse gives scientists the ability to measure their size and mass.

Chandra and Mintaka

NASA’s Chandra Xray Observatory studied the eclipsing binary for almost six days. And the Chandra image below shows an inset ground-based telescope optical view of Orion.

Chandra and Mintaka
Image: NASA, M.Corcoran et al, CXC, GSFC/M. Corcoran et al., and Eckhard Slawik

Scientists observe the stellar pair to understand better the relation between star properties they see from optical observations and the wind properties revealed through X-ray emission.

They’ve learned that the secondary star has faint X-rays and a weak wind. And by watching the pair through Chandra, astronomers know the smaller star blocks part of the giant star’s winds. And that helps them see what is happening with the X-ray-emitting gases surrounding the primary star.

Chandra helped answer the question of where that gas formation occurs, showing scientists that the X-ray emission comes from a massive star’s wind. They believe it stems from collisions between swift-moving gas clumps in the wind. The collisions produce shocks which then produce X-ray emissions.

Chandra scientists also applied optical data from MOST (Microvariability and Oscillation of Stars Telescope) and the Canadian Space Agency. MOST researchers showed evidence of tidal interactions between the eclipsing binary causing oscillations in the primary star. 

So the two groups of scientists helped rectify inconsistencies in theories of how stars evolve. They continue learning much about the lifecycles of stars through observing this eclipsing binary.

Stars In The Orion Constellation

In addition to the well-studied stars within Orion’s Belt, the constellation itself contains some monstrous beauties. Most are young blue supergiants, while Betelgeuse is a red supergiant.

Betelgeuse (Alpha Orionis), Red Giant In Orion

Betelgeuse forms the hunter’s right shoulder. It is an orange-red-hued variable red supergiant with a magnitude of 0.42, making it between 7,500 and 14,000 times brighter than the Sun. And even though it is massive and luminous, it isn’t all that hot. Betelgeuse has a surface temperature of around 6,000 degrees Fahrenheit (about 3,300 degrees Celsius). And that’s about 4,000 degrees cooler than the Sun’s surface.

Below is a NASA Hubble Space Telescope photograph of Betelgeuse, the first direct image of any star besides the Sun.

Image: ESA, NASA, Andrea Dupree (Harvard-Smithsonian CfA), and Ronald Gilliland (STScI)

Betelgeuse is also much younger than our Sun at only 10 million years, compared to an approximately five billion-year-old Sun.

Betelgeuse has a future destiny as a supernova blast, possibly within our lifetimes (a tiny chance, but still a minute possibility.) And if it did explode in our lifetime, Earth is not threatened since the star is 550 light-years away. But it would be a spectacular show!

The star was recovering from a late 2019 dimming when it blew off part of its surface. The illustrations below show Betelgeuse during the dimming. The first two panels depict the ejection of hot plasma from a convection cell on the supergiant’s surface. 

Panel three shows the gas expanding outward, similar to a volcanic eruption. And then, the fourth panel depicts an enormous dust cloud blocking light to Earth, thus resulting in our dimmer view of Betelgeuse.

Image: ESA, NASA, and E. Wheatley (STScI)

Bellatrix (Gamma Orionis)

Another blue-white giant star in the Orion constellation is Bellatrix. It forms the left of Orion’s shoulders. She lies 240 light-years away and has a visual magnitude of 1.64. Bellatrix is 6,400 times brighter than the Sun and eight times more massive.

Rigel (Beta Orionis)

Rigel is a triple star system with a magnitude of 0.12, making it 85,000 times brighter than our Sun. It lies 860 light years from Earth and is about 17 times more massive than the Sun, 70 times its width. Rigel represents Orion’s left foot and is the brightest star in the constellation.

Rigel is another young star, around 8 million years old. But its surface is hotter than Betelgeuse by thousands of degrees. So that makes it blue-white instead of red. And it is so bright that you can even see its colors from Earth.

Saiph (Kappa Orionis)

Orion’s last blue supergiant star is Saiph, which forms the hunter’s right leg. It is about 720 light-years from Earth and has a magnitude of 2.06. This supergiant is around 16 times the Sun’s mass and shines about 18,000 times brighter. So you can see that the stars in Orion are truly gigantic compared to the Sun.

Image: EarthSky and Chelynne Campion 

Use Orion’s Belt To Find Other Sky Objects

Since Orion’s Belt is so bright on clear, moonless nights in the winter, you can use it to find other stars and sky objects.

First, use Orion’s Belt to find Betelgeuse to the north and bright Rigel to the south during early to mid-evening. These two stars within the constellation of Orion will fill your telescope with wondrous sights. Betelgeuse appears as a ruddy orange color while the blue-white heat of Rigel shines through.

Image: Astronomy Trek

Then, later in the night, sometime around midnight, Orion reaches its highest point to stand tall and proud. So you can use stars in Orion’s Belt to locate other notable celestial objects. For example, draw an imaginary line through the belt to the northeast and find Aldebaran in the Taurus constellation.

And once you’ve satisfied your curiosity, point your telescope in the opposite direction. Use Orion’s Belt to point toward Canis Major (The Greater Dog), where you’ll find the bright star, Sirius. It is sometimes called the Dog Star and is one of the most luminous stars in the night sky, with a magnitude of -1.46. 

Sirius is nearly twice the Sun’s radius, with a surface temperature of about 4,000 kelvins hotter at about 9,940 kelvins. In addition, the Dog Star is “close” to the Earth at around 8.6 light-years away. Sirius gets its name from Greek words meaning sizzling or scorching.

Image: AstronomyTrek.com

Locate Orion’s Nebula By Finding Orion’s Belt

In addition, use Orion’s Belt to locate the second “star” in the hunter’s sword. Orion’s Nebula offers stunning views of the closest stellar nursery to Earth. Depending on your telescope’s capability, you may see a fuzzy-looking star. Or you may also see some of the cloudy, celestial dust that becomes the elements within star births.

Exoplanets Near Orion’s Belt

In addition to some of the brightest stars in the heavens and a stellar nursery, you’ll find exoplanets (planets outside the solar system) near Orion’s belt. For example, astronomers discovered a giant gas planet about three times more massive than Jupiter.

Scientists estimate that each star in the galaxy has at least one planet orbiting it. When you think about our Sun having eight planets and one dwarf, it puts into perspective how many worlds could be out there.

Wrap-Up: Orion’s Belt

Look into the heavens on a clear and cloudless night for the best views of the three bright stars making up Orion’s Belt. They appear in a relatively straight line, making them one of the easiest objects to find. 

Orion’s Belt acts as a gateway to celestial observations, helping you find and view the closest stellar nursery to Earth. You can also use the belt to find some of the brightest and most massive stars in the sky, like the enormous red supergiant Betelgeuse.

So grab a pair of binoculars or set up your telescope because Orion’s Belt offers incredible views. You’re in for a wild night of star gazing!