The degree, which almost nobody publishes
A sun sign is a thirty degree band. Saying someone is Aquarius narrows their solar position to one twelfth of the zodiac and stops there, which is why every page about this date reads the same. The degree narrows it much further. On 9 February the Sun has always been found within a degree and a half of the same spot, whichever year you pick between 1930 and 2035.
That stability is not a coincidence. The Gregorian calendar was designed to track the tropical year, and the leap day resets the small annual drift every four years. The date and the orbit stay in step, so a given calendar date keeps returning the Sun to nearly the same longitude for centuries at a time.
Knowing the degree also changes what can be said about aspects. A planet at nineteen degrees of Libra is in trine to a Sun at twenty degrees of Aquarius, whereas one at five degrees is not, and no amount of knowing the sign alone will tell you which case applies.
Sitting on the seam between two decans
Each sign divides into three bands of ten degrees called decans. Twenty degrees is the line where the second decan of Aquarius ends and the third begins, and this date lands right on it. In most years the Sun has crossed into the third decan by noon, but in the earliest years of a leap cycle it is still a fraction of a degree short.
In the Chaldean order that runs through the planets in sequence, the third decan of Aquarius is assigned to the Moon and the second to Mercury. Tradition reads the Moon decan of Aquarius as the reflective end of the sign, where the detachment turns inward rather than outward. That is interpretation rather than measurement, and it is worth marking as such.
What the date does not decide
The Moon moves through a sign in about two and a half days, so on any 9 February it occupies one of two signs, occasionally three if the day catches a change near midnight. Two people born on this date twenty hours apart can have lunar placements with nothing in common.
The rising sign moves faster still. It turns through the whole zodiac in a day, so it depends on the hour and the latitude of birth and can be any of the twelve. The Sun is the slowest of the personal placements and therefore the least individual thing in a chart, which is an odd fact given how much weight popular writing puts on it.
House placements move with the horizon, so the same Sun can sit at the top of the chart for one birth and near the bottom for another a few hours later. That difference is usually read as more telling than the sign itself.
Using the widget above
The widget above takes your year, your birth time and your birthplace and returns the Sun's longitude to the degree and minute for that exact moment, rather than the noon approximation used here. It also reports how far you were born from the nearest sign boundary, which on this date will come back as a comfortable margin of about eleven days.
If your birth time is unknown, the calculation defaults to noon. For a date this far from a boundary that costs you nothing at the level of the sign, though it does leave the degree uncertain by up to half a degree and the rising sign entirely open.
Questions people ask about this
What sign is 9 February?
Aquarius, in every year on record. The date sits about eleven days after the Sun enters the sign and about ten before it leaves, so no year in the modern calendar has moved it across a boundary.
What degree of Aquarius is the Sun on this date?
Between about nineteen and a half and twenty one degrees, depending on the year and the hour. The widget above gives the exact figure once it has your birth details.
Which decan does 9 February fall in?
Usually the third decan of Aquarius, which runs from twenty to thirty degrees and is assigned to the Moon in the Chaldean scheme. In a few years the Sun is still a fraction short of twenty degrees at noon, which places it at the very end of the Mercury decan.
Does the sign change from year to year?
No. The Sun's position on a fixed calendar date wanders by roughly a degree and a half across a century, and that is nowhere near enough to reach either edge of Aquarius from this point.
Am I on a cusp?
No. Cusp is a word people use when they do not know their exact position, and this date is not close to a boundary in any year.
Do I still need my birth time?
Not for the sun sign, but yes for everything else. The rising sign changes roughly every two hours and the houses move with it, so without a time the chart is missing its frame.