The people asking this question aren’t asking for an answer from astronomy, but let’s just give the astronomical answer very quickly so its clear and out of the way.

The Astronomy Answer

• Rohini is a segment of sky based on a star (Aldebaran).
• Taurus is a segment of sky based on the equinoxes (segment 2 from the northerly equinox).

Due to the Earth’s rotational axis not being completely still, the relationship between the equinoxes and the stars changes gradually over a period of about 26 thousand years.

This is why the star-based segments (nakṣatra like rohiṇī) do not have a permanent location relative to the solstice-based segments (rāśī like vṛṣabha / Taurus), and visa-versa why the solstice-based segments do not have permanent location relative to the star-based segments.

“Ayanāṁśa” is a measure of the current discrepancy between a reference star (usually citrā/ Spica) and the referenced solstice-based location (usually the southerly equinox, i.e. 0° Libra).

The Astrology Answer

Now, let’s get to what people probably really want to know… “What Rohiṇī symbolizes matches what Taurus symbolizes, so how can it be elsewhere?”

Let’s put nakṣatra aside for a second. Are you familiar with the aṁśa of rāśī, like the navāṁśa? This is the concept that any zodiac sign is subdivided into 9 parts, each of which represents another zodiac sign. The first navāṁśa in Aries is Aries. The second is Taurus. The third, Gemini. Then Cancer, Leo, Virgo, etc.

It is very easy to imagine the Aries navāṁśa within Aries, because… well, because they are the same! So this is called the uttama-aṁśā a.k.a. vargottama – the “best amśa” – because it is completely harmonious with the sign it is in.

It is also pretty easy to imagine the Leo and Sagittarius amśās within Aries, because, like Aries, these are fire-signs.

But how about the Taurus amśā, how can that be in Aries? Or even stranger, Gemini?? or Cancer??? or, dear gods above and below, Virgo????? How on earth are we supposed to make sense of the Virgo section of Aries?

Anyone at all conversent in Vedic astrology will immediately reply, “Oi, my child! Don’t you see, this oddness is by design! Some aṁśas are identical to their rāśī. Others are favorable to it. Still others are unfavorable and even entirely incompatible with it. This accounts for the variations within any sign!”

Why am I talking about navāṁśa when the question is about nakṣatra?

Just re-read all the above and replace the “navāṁśa” with nakṣatra and you will have your answer! If you think Rohiṇī can’t be in Gemini, or Maghā can’t be in Virgo, ask yourself how Virgo can be in Aries as it’s amśa.

Rohini Specifically

Let’s look at Rohinī specifically, and I will ask you to use what you learn about this as a template for understanding not just Rohiṇī, but any and every nakṣatra.

First of all, Rohiṇī’s symbolic characteristics are not derived from Taurus! They are derived from the way the star and its cluster (“asterism”) looks, which then associates it with a particular god or goddess, who then invests the nakṣatra with his or her own characteristic śakti.

This explains why Kṛttikā and Mṛgaśīrṣa are also, supposedly, “in Taurus.” And it explains why some of Rohiṇīs traits are not exactly the same as Taurus’. For example Rohiṇī has a very active and ambitious aRohana-śakti – which means it is “aRousing”. In this it is more like Scorpio than Taurus.

Still, it is undeniable that Rohiṇī has many important things in common with Taurus: it is fertile, intelligent, creative, passionate, loving, and very beautiful. This is just like having a Taurus navāṁśa within the Taurus rāśī.

During the centuries when Rohiṇi coincides with Taurus (roughly between 2200 BCE ~ 1800 CE) we have zone in the sky that is similar to vargottama -perhaps we can coin the term nakṣatrottama – a zone where the symbolism of the nakshatra is very synergistic with the symbolism of the rāśī.

From 1800 onwards Rohiṇī precessed onwards into Gemini, with none of it at all remaining in Taurus. Since then, the Rohiṇī zone is in a rāśī that has some similarity and some dissimilarity with it. For example, Gemini is also very, very creative, sensual, an intelligent – so these qualities still come through very clearly. But Gemini definitely does not share Rohiṇī’s qualities of being dedicated, enduring, and faithful. Hence, from 1800 onwards we no longer have an area of the sky that very clearly represents ideal romantic relationships.

I am sure if you look at global marriage and divorce statistics, it will make a lot of sense on this timeline. Even the character of creative ingenuity has changed markedly since 1800, we no longer have long-term development of schools of thought. Rather we have rapid replacement of one technology with another, one system with another, one ideology with the next.