The central and brightest of the three stars in Orion's Belt and the fourth brightest star in the whole of Orion. Alnilam is a blue-white supergiant star.

Like most supergiants, Alnilam is rapidly shedding mass. A powerful stellar wind blows from its surface at speeds up to 2,000 km/s, carrying way about two millionths of a solar mass per year (20 million times the rate lost by the Sun). Although only about four million years old, Alnilam is already fusing heavy elements in its core and is doomed to explode, in the next million years or so, as a supernova. (1)

One of the monsters of the Milky Way, Alnilam, is blowing into space a so great quantity of hot gas that this, in a million years, could to make two stars as heavy as the Sun.
 Being a supergiant, Alnilam it's about 40 times as massive as the Sun, tens of thousands of degrees hotter, and hundreds of thousands of times brighter. So intense radiation, in fact, pushes a dense "wind" of charged particles from the surface of Alnilam out into space at millions of miles an hour.

The most impressive member of the Orion's belt, Alnilam it's the brightest of the three stars, even though it's hundreds of light-years farther than the other two. And while each of the others actually consists of two stars, Alnilam moves through the galaxy alone.
Although Alnilam is only a few million years old, it's rapidly nearing the end of its life. Over the next few million years, it will "burn" through a series of heavier elements forged in its core its original hydrogen fuel. That process, Alnilam won't be able to sustain any longer. Its core will collapse, while its outer layers will blast into space as a supernova -- briefly outshining most of the other stars in the galaxy combined.

There's a diagram that was drawn by Juan Santa Cruz Pachacuti Yamqui Salcamayhua, a native of the Andes, writer who was born in the early 1600s and made the manuscript, obviously, some years after the conquest of the Spaniards (1533).
His chronicle presents information on Inca Astronomy that was not documented by european writers. The drawing proved invaluable in the understanding of the Inca stellar astronomy.
Among the drawings of the Sun and Moon and other stars and constellations as the Southern Cross, for example, there is a line of three stars.

The line of the three stars is known as ‘Orcorara’ (2) which means ‘three stars all equal’. There is a story about these three stars. The two stars at the end are called the Patá (which are known as The Marys) and the star in the middle is the thief and villain. The Moon wanted to punish him, so she sent the two stars to capture him and hand him over to vultures which are the buzzards formed by the four stars below Patá.
Much probably these five stars represent the stars of the Orion. The three stars in the row are Orion’s belt. Orion’s belt is unique because the three star making up the belt, namely: Alnitak (the girdle) Alnilam (the string of pearls) and Mintaka (the belt) forms a straight alignment and are roughly the same in brightness. The perpendicular star to the belt and below it is Betelgeuse which is the eighth brightest star while the star which lies equal distance above the line is Rigel and this is the seventh brightest star in the sky.
Using the Coricancha temple as the center, we can extend the ceques ( that means “straight” or “ahead” in Quechua) as imaginery lines outwards to the to the horizon then you can locate the rise and set points of certain stars.

I'd prefer to accept the 'theory' that seems the most likely to be astronomically accepted (apparently there are those who think otherwise) is that the four imaginary lines that crosses the Coricancha temple are determined by the main star of Orion's belt, Alnilam, that focuses exactly over the city of Cuzco (ancient capital of the Incas), that was the center of the world, in March 21, in solstice of winter. So, from Anilam, the Tahuantinsuyo (the Inca Empire), was divided by two ceques into four suyos, namely: Collasuyo, Chinchaysuyu, Antisuyo, Contisuyo.

(1) A molecular cloud, NGC 1990, surrounds Alnilam and is partly illuminated as a reflection nebula by the star's intense radiation.
(2) Chaccana. Three stars called Three Mary (Orion's Belt).