This video begins with a ground-based image of the Pleiades. It zooms into Merope, eventually settling on Hubble’s image of the reflection nebula that is being destroyed by the star’s radiation. [NASA]

By T.V. Venkateswaran | 2026-04-29

Across human history, there has been a persistent fascination with the cosmos. In this three-part series, BlueShift takes a deeper look at the way ancient civilizations in very different parts of the world interpreted the heavens.

On the night of August 7, step outside. Or pick September 3, October 28, or November 24. (* see below for optimal viewing times).

Find a dark spot. Tilt your head back and look up.

Next to the moon, you’ll notice a small, misty cluster of blue stars. Six, maybe seven of them, huddled together. Astronomers call it the Pleiades, or Messier 45 (M45). In India, it has always been Kṛttikā.

Stay with the sky for the next few evenings. Each evening, that cluster drifts a little farther from the moon. After about 27 days, the moon returns, right next to the same cluster of faint stars, drawn back as if on an invisible thread.

Ancient observers in India saw this rhythm.

They watched the stars appear fixed to the celestial vault. Rising and setting in the same patterns night after night, like clockwork.

The moon, however, never stayed still. It swam through the sea of stars, pausing each night in the "backyard" of one special star.

Observers counted 27 such stopping points. In Tamil, one of the world’s oldest living classical languages, these are nāḷ mīṉ – "stars of the day."

In Sanskrit, they became nakṣatra.

While much of the world eventually organized its calendars and star lore around 12 zodiac signs, India's astral sciences, called jyotiḥśāstra, rested on these 27 (sometimes 28) lunar mansions.

The word jyotiḥ simply means "light in the sky." It blended astronomy, mathematics, ritual, and divination into a single system.

So how did this evolve?

Let’s rewind.

Stars along the moon's path

Around 1,100 BCE, Mesopotamian-Babylonian sky-watchers placed 18 constellations along the moon's path. By 700 BCE, they had slimmed that number to 12, one for each month.

And by 500 BCE, the Babylonian "zodiac" became pure mathematics: each sign was a neat 30-degree arc of the ecliptic. This formed the basis of Western astral sciences.

India took a different road. The early Indian calendars were lunar. Months were named after the star near which the full moon appeared.

Caitra, for example, is the month when the full moon sits near the star Citrā (Spica, in modern terms). Attention stayed focused on stars lying close to the moon's path along the ecliptic, the ones the moon could occult or brush past.

The moon takes roughly 27.3 days to circle back to the same star. This gave the ancient observers a natural way to slice the sky into 27 lunar resting places, one for each night of its journey.

In time, the word nakṣatra itself changed. What once simply meant any "star" in the heavens slowly narrowed until it pointed only to these special lunar stations along the moon's path.

The earliest clear list of these nakṣatras appears in the Taittirīya Saṁhitā, a text likely composed between 600 and 500 BCE.

At first, the distances between nakṣatras were uneven, and one extra station, Abhijit, sometimes slipped in between Uttarāṣāḍhā and Śravaṇa, making 28. But 28 makes irregular gaps.

By the later Siddhāntic period (around 300 CE), mathematician astronomers standardized everything. Each nakṣatra became a precise arc of 13° 20′ along the ecliptic. The system turned mathematical, yet it never lost its older, poetic roots.

Here is where things get visual and a bit messy.

Multiple celestial stories

Contemporary illustrations often show each nakṣatra as a "connect-the-dots" figure, much like Greco-Roman constellations.

Each asterism is named after its brightest star, the yoga-tārā. For example, Aśvinī asterism is a group of three stars imagined as a horse’s head, located in the Zodiac of Aeris, and the yoga-tārā Aśvinī is most likely Alpha Arietis.

Kṛttikā is a group of six or seven tiny stars, the Pleiades. Citrā is a single star, Spica.

But even this identification is debated. In 1806, British orientalist and Sanskrit scholar Henry Thomas Colebrooke noted that many Indian paṇḍitas (scholars) pointed to the three bright stars in the head of Aries (α, β, γ) as Aśvinī asterism.

Yet Tamil astral literature insists Aśvinī has six stars, not three.

So which is correct? Perhaps both.

The shapes assigned to these asterisms were never rigid. The earliest text describing the shapes of these asterisms is the 11th century Jyotiṣaratnamālā by the mathematician-astronomer Śrīpati (1019–1066 CE).

He pictured Kṛttikā as a razor.

But an old Tamil caṅkam text, Puṟanāṉūṟu 229 (dated between 100 and 250 CE), offers a very different vision.

Kṛttikā, which Śrīpati saw as a razor, is described there as "smoldering sparks." Anuṣa, a welcome arch in Sanskrit texts, becomes a bent palmyra palm. Punarpūsam, a bow or quiver, is visualized as a pond.

Different communities across the subcontinent painted their own pictures.

For the Nicobarese, the Pleiades are the seat of ancestors. Banjaras see a forehead jewel. Kolams imagine one large bird followed by many small ones. Korku people recall minced cow meat; Gonds, stones hurled at birds.

The sky was never a single story.

By the time mathematical astronomy matured, the nakṣatras had quietly shifted in meaning. From around the 10th century onward, the meaning of nakṣatra shifted again, from a cluster of stars to an abstract 13°20′ arc along the ecliptic.

The visualizations became symbolic. Mathematics took over. Yet the human need to see stories in the stars never faded.

For centuries, Indian astrology revolved almost entirely around these lunar mansions. Rituals, weddings, and even the naming of children followed the moon's position among the nakṣatras.

Cultural blending

Then came a great shift around the middle of the second century CE.

A text called the Yavanajātaka (literally meaning, 'Greek Horoscopy') was translated into Sanskrit.

Its original author was probably a Greek-speaking scholar working in western India. The poet Sphujidhvaja translated this around 270 CE and introduced the notion of 12 zodiacal signs, beginning with Aries (translated as Meṣa).

Indian astronomers did not simply copy. They blended. The first point of Meṣa was tied with the first point of Aśvinī. Thus, the Indian 27 nakṣatras correspond to the 12 zodiacal signs. That worked out to nine quarters of a nakṣatra per sign.

The Greek influence is hard to miss; Sanskrit names for the rāśis were direct translations of the Greek ones. In some cases, the texts were phonetic transliterations; Greek words spelled out in Sanskrit.

But one difference is profound.

Western astrology later adopted the tropical zodiac, tied to seasons and the moving equinoxes. India kept a sidereal system (nirāyaṇa), fixed to the stars.

The initial point was set around 285 CE and does not drift with precession. Precession of the equinoxes is acknowledged but not allowed to shift the star-based coordinates.

Even today, many families consult a pañcāṅga, the traditional almanack, prepared using lunar stations, before fixing a wedding date or starting a new venture.

Many families still choose the first syllable of a newborn's name according to the moon's nakṣatra on the day of birth.

The nakṣatra system reminds us that long before telescopes or satellites, people across the world looked up, noted patterns, named them, and let those patterns order their temporal life.

They turned the sky into a calendar, a ritual guide and a shared storybook.

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Optimal viewing times to see the Kṛttikā star cluster, also known as Pleiades, Seven Sisters, and Messier 45 (M45), in close conjunction with the moon:

August 7, 06:23 UTC

September 3, 12:03 UTC

October 28, 01:11 UTC

November 24, 11:18 UTC

According to the Royal Observatory, Greenwich, the cluster is visible from the Northern Hemisphere between October and April, and all night during November and December.