Star Regulus in constellation Leo but sign Virgo
This year, in 2012, the star Regulus, the brightest in the constellation Leo the Lion, passes out of the sign Leo and into the sign Virgo. According to the web site constellationsofwords.com, Regulus entered the sign Leo in 156 B.C. and the sign Virgo in 2012, staying within the sign Leo for 2,168 years.
The Sun is said to enter the sign Virgo whenever the Sun is 30o west of the northern hemisphere's autumn equinox point or 60o east of the northern hemisphere's summer solstice point. That explains why the Sun is now in conjunction with Regulus on or near August 23 - one month before the autumn equinox or two months after the summer solstice.
The signs stay fixed relative to the solstice and equinox points. However, the solstices and equinoxes move westward relative to the constellations or "fixed" stars (such as Regulus), going 30o westward in ecliptic longitude in about 2,160 years. Or another way of looking at it, the constellations and stars move eastward through the signs. Therefore, the star Regulus will mark the first point of the sign Libra (September equinox point) in another 2,160 or so years.
The sky chart below shows the constellation Leo as defined by the International Astronomical Union in 1930. I doubt that the ancient constellation boundaries were so precisely drawn, but I'd guess a lot of emphasis was given to key zodiacal stars, such as Regulus.
Sky chart of the constellation Leo
Dawning of the Age of Aquarius
At this CosmoQuest forum, someone named "tick54" had a very novel way of dating the start of the Age of Aquarius at the year 2012. Presuming that Regulus marked the border of the constellations Leo and Cancer when the constellations and their corresponding signs were in alignment in ancient times, or around 156 B.C., then 2012 marks the end of Regulus' passage through the sign Leo.
By tick54's reckoning, Regulus still marks the ancient border of the constellations Leo and Cancer, even as Regulus enters the sign Virgo. That being the case, the border between the constellations Pisces and Aquarius has to be 150o west of Regulus, with the Pisces/Aquarius border residing at the March equinox point - the First Point of Aries - in 2012. Tick54 is assuming that in ancient times, constellations and concordant signs both represent equal 30o divisions upon the zodiac.
copyright 2012 by Bruce McClure