T
racking the planets in the night sky wasn't an easy task, but it has continued for centuries. The same discipline of stargazing gave birth to two different subjects. Does astrology really work, or is it just a made-up story? Hello and welcome to our blog, where we discuss stars, planets, galaxies, and everything that is found in space in accessible language. Today's article will tell you about the relationship between two sciences called astronomy and astrology. Let's begin.
Introduction:
It might feel awkward to you that an astronomy blog is mentioning astrology
and going to explain it. No, this is not an astrology-focused article, but
it will connect both disciplines since you might have heard from both
astronomers and astrologers that this planet is moving here, this one is
going there, and so on. What's the matter? This is what we'll talk about in
this post.
From time immemorial, our ancestors slept beneath the starry sky, of
course. It was natural to be used to seeing the same stars every night, and
they noticed some stars moved slowly, some were faster, or some were just
static or didn't seem to move or moved after a very long time.
Later on, they built some imaginary shapes inspired by what they could make
out of those tiny dots with their folklore and cultural stories. We call
them constellations; that's how they knew the first difference between
planets and stars.
Planets tend to move faster than stars, but hey, it's not the movement as
we see in the sun, which rises in the east and sets in the west; the
movement we are talking about is perceived after careful skywatching.
They found some dots rise or shine around the same constellation
periodically after months or years; that was the foundation of the
planets because a planet itself means a wanderer that starts
from moving and returns to the same place.
The term we will be talking about in this article is called astrometry,
which deals with measurements of planetary motion in the sky, their
position, and other aspects. It's not a new field created after scientific
advancements, but it's one of the oldest branches of astronomy; this is
where astronomy and astrology meet and analyze the position, time, and
movement.
Astrometry:
As its name suggests, this field is related to measurements of celestial
bodies. Since ancient cultures needed to estimate the time of their
agricultural activities, rituals, and other events like solstices,
equinoxes, eclipses, etc. Independent cultures developed their own methods
to track and estimate the movements of celestial bodies.
Even modern science must be certain of specific observations,
transits, eclipses, and other important periodic moments so that they can
prepare their tools and observatories to study the phenomenon. That's why
this ancient science still matters.
Let's know its basics. We know very well that in space nothing is tilted,
upside down, vertical, horizontal, forward, or backward; hence, the
directions and orientations we use on Earth render futile there. All
stars, planets, and celestial bodies are scattered in a 3D universe. Even
on our own planet's south pole or Antarctica, you always see land under
your feet, and the sky is at the top of your head.
Astrometry uses numerous terms to define a celestial object's location,
orientation, direction of its movement, and location within its orbit.
Let's see some static imaginary terms so that our universe doesn't appear
clueless and uniform to us.
Reference:
Because of the aforementioned reasons, we needed reference systems, and
our ancient astronomers used the fixed stars, constellations, and other
clues to anchor our planet and observation posts in this clueless
universe.
Reference means the anchor or origin point that you might use to
tell an object's position. For example, when you want your hat and send
a person in your room, you might say you can turn to the left side,
there is a cupboard, and my hat is inside. Here, the person will use his
current position while he enters the room; his current position around
the door is the reference.
Consider our ancestors and sky watchers were accustomed to seeing the same
stars every night; they could easily tell about certain stars and popular
constellations. They went one step further and divided most of the
night sky into constellations, even with certain seasons or times, and
they were well familiar with those imaginary shapes. Now let's see how the
reference systems started.
Planes:
In the above image, you can see the Earth has been arrested and
imprisoned behind bars; we've also made some weird things. Let's
see what they are. You know that Earth revolves around the Sun and takes
a year to complete one round; this supposed track or path is shown as
the orbital plane.
The differences in tilt between the rotation axis and the orbital plane
are shown as the axial tilt. For Earth, the orbital plane has no
tilt and is assumed to be a flat road-like path while Earth spins along
its axis by leaning around 23.5°, instead of being absolutely upright.
Celestial sphere:
Let's see why we imprisoned the Earth; there are
180 horizontal and 24 vertical bars. Vertical ones denote
the sidereal rotation of our planet, which means our Earth takes 23
hours 56 minutes to make a 360 rotation, but the next sunrise
occurs after 361° of rotation by the Earth; that's why the solar
day/night is about 24 hours while 23h 56m is the
sidereal day/night duration. The sphere denotes the celestial
sphere around the Earth or another planet.
The horizontal bars are exactly latitude lines of a geographic globe, but
projected onto the sky. This means your land and sky latitude would be the
same angle; the 0 to +90 degrees means north hemisphere, and the
northern geographic pole is at +90 degrees. From 0 to -90 degrees denotes
the southern hemisphere, with the southern geographic pole at -90°;
for both sky and land only two different directions: geographic would mean
towards the center of the Earth, while celestial latitude or pole points
toward the sky.
The celestial sphere and its components are used as a first line of
address of a planet other than the Earth, because they appear in our
skies, our celestial sphere. The Vertical lines or longitude are called
Right ascension or RA, measured in hours, minutes, and seconds. The
horizontal lines or latitude on this sphere are called
declination or Dec.
Now you can address a celestial object like RA- 18h 37min, Dec- +28.05.
Keep in mind, these are not the same hours and minutes you use in your
daily life; they are sidereal time units, whereas our clocks are basically
solar time-based tools.
Fixed Stars and Ecliptic plane:
|
| Sun appears to move through the constellations due to motion of the Earth |
We have added a path called the ecliptic plane, which denotes the
apparent path of the Sun as our planet moves around the Sun and the Sun
appears to move through the constellations found in this ecliptic belt.
Remember, the sidereal day, month, or year, the location of planets in
our solar system, and their movement are studied by taking the help of
fixed stars. You might ask which star is really fixed if everything in
our universe is moving?
The background stars that you see in space photos and videos, or
even the night sky stars, are almost 99% fixed stars because they don't
move as quickly as planets, only appear to move over a window of
hundreds of years, so they appear fixed to human timescales because of
their unimaginable distances.
Stars like Betelgeuse, Mintaka, Canopus, Aldebaran, Deneb, Meissa, Saiph,
Alnair, Alpharetz, Sirius, Vega, Algol, Altair, Bellatrix, and all the
commonly known stars act as anchors, and our ancestors used them in
astrometric observations, predictions, and analysis.
However, they used constellations for ease; this helped them from
confusions since they bunched up stars and created shapes.
As we said earlier, 88 constellations are distributed in every
direction on the Earth or our Solar System. Some would be located on the
top of the equator (near 0°) of the Earth or its celestial equator. Some
could be located around the tropics, poles, or in between.
Ancient astronomers concluded that our Sun appears to move through
equatorial constellations throughout every year. These 13 constellations
are: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius,
Ophiuchus, Sagittarius, Capricornus, Aquarius, and Pisces. This cycle
repeats every year.
You might ask, if the Sun illuminates the Earth and other stars are
hidden, then how could they know the Sun is moving from this to
that constellation in daytime?
Well, it's a topic of our next article, where we'll discuss how the
ancient observer knew the Earth moves, its shape, tilt, and other facts
that we are being taught in our school and but most of the commoners don't
even know in modern times about their observational tricks.
Orbital attributes:
Since planets are constantly moving around the Sun, it's better to have
some signposts, like how we should know whether a planet is about to
complete a cycle, or just completed one and is starting another round,
etc. To understand this, we need to get the basic idea of the paths of
planets, or simply orbits.
Planets move in elliptical orbits around the Sun, which is not a perfect
circle due to several reasons. For example, gravitational perturbations,
moons, distance from the Sun, neighborhood influence, etc. Hence, the
orbit is not a perfect circle, and the Sun is not at the exact center but
around the center. Such a circular path has the following properties:
a. An ellipse has one center and two foci (plural of focus).
b. Its longest diameter crossing through the center and both foci is
called the major axis.
c. The major axis's half is called the semi-major axis.
d. A perpendicular line to the major axis, running through the center
and connecting both closest points, is called the minor axis, and its
half is the semi-minor axis.
e. Eccentricity determines the deviation from the perfect circle where
the major and minor axes are equal to the radius. 0 means perfect, 1
elliptical, and larger than 1 denotes a hyperbola.
After we know the ellipsoidal orbit, let's assign the signposts for
planets:
|
| Checkpoints in a planet's orbit |
Pericenter
It's the closest point on the ellipse to the center. Located at 0° or
360° mean anomaly, it's the reset point where the planet is considered
to have completed an orbit. Around this point, the planet moves fastest
and travels more distance in equal time due to the gravitational effects
of its parent body. Also, the word pericenter is a geometric term and
applies strictly to an orbit rather than to constellations or other
clues.
Pericenter has specific names when we study special bodies; for the Earth,
this point is called perihelion (Helios = Sun). Because Earth is the
orbiting body, the Sun lies around the center of this elliptical path. For
Earth's Moon, it's called Perigee. While studying Saturn's moon, it's
called perichron, because Saturn has a name, Chronos or Kronos in Greek.
While Apocenter is just the opposite of the pericenter, which is the
farthest point from the center. Terms like Apogee, Apchron can also be
applied when studying such things. The farthest point is located at 180°
anomaly on an elliptical path.
The pericenter is defined by these parameters mainly; we need these
parameters because you can't always see the pericenter at the same point
from the same spot due to planetary movements and our Earth:
Argument of pericenter:
If you make an angle on the orbital plane (path of the planet) while
connecting the ascending node and pericenter, you will measure the
argument of pericenter. This is important for estimating the ellipse's
orientation and its pericenter; otherwise, you'd know the orbit's size
and tilt.
It also matters when we predict the transits or eclipses, or even the
spacecraft maneuvers. Remember that the argument of pericenter tells us
where the pericenter is located relative to the orbit's size and tilt.
In short, this tells us where the 0 ° anomaly is measured from the node.
Since Earth has no orbital inclination, therefore no ascending node and
argument of pericenter; it's defined by other reference systems.
Longitude of pericenter:
You see that we've defined the geometry of the elliptical path as if we
were hovering in the space around a planet's north pole, but in reality
we observe things far from such a system, and it's time-consuming as
well. Let's see another parameter with a similar name, which is called
the longitude of pericenter. It's measured on the reference
plane, like the celestial grid or sphere (imprisoned planet) or the
ecliptic (13 constellations). This is used to tell where the planet's
pericenter would be located in the Earth's sky through constellations.
Here's how you can understand the longitude of pericenter:
1. Imagine you stand on Earth facing toward the Aries constellation,
which is the reset point of this celestial clock. This is the clock's 12
o'clock position, or 0° on a compass.
2. Suppose you can see all 13 constellations around you in a 360° circle
within their boundaries.
3. If you turn counterclockwise or toward your left hand, then 0°= Aries
(front), 90°= Cancer (left), 180°= Libra (back), and 270°= Capricornus
(right) constellations would be located accordingly.
4. If a planet has a longitude of pericenter at 100°, it means
its pericenter would be located between 8 and 9 o'clock, which would set
the pericenter around the Leo or Cancer boundary from your and Earth's
perspective.
5. It simply means whenever the planet reaches this point, it would be
closest to the Sun according to its elliptical path geometry.
Also remember that conventional methods use Aries as the anchor point
because our Earth's 90° anomaly points to this constellation, so it's
easier to measure from Aries than to find the actual 90° anomaly of the
planet itself and tell us the address of the pericenter in the sky instead
of in orbit.
For example, Uranus' longitude of pericenter is 170 degrees, so its
pericenter would be around the Sagittarius/Capricornus constellation from
Earth's sky. Uranus' pericenter will stay in the foreground of the
Sagittarius-Capricornus constellations for thousands of years regardless
of Earth's motion because the planet's longitude of pericenter doesn't
change for a long time. Here we'll provide you with the table of this
parameter for all 8 planets, so you never miss them when you take
your telescope next time.
Anomaly:
This is the actual marker of the planet's position in its orbit. See,
even though orbits are not perfect circles, we still can apply the 360
rule. Meaning, the planet has to complete a whole 360 degrees in its
orbit. For ease in the image in the pericenter part, we've divided the
ellipse into 12 parts, each containing 30°; therefore, 30 × 12 = 360°.
The planet will be assumed to have completed one round when it reaches
back the periapsis or perihelion in the case of solar system planets,
and this cycle continues.
But don't estimate too soon because it's not like watching a clockface and
telling the time. We earlier said a star or sun doesn't really stay in the
center; instead, it can be found around the center of this geometric
ellipse. How?
One of the main reasons is gravity; the universe's bodies have gravity,
and they exert some amount of force on each other, but the one that has
less momentum gets affected easily. Our Sun's gravity is strong enough to
make everything in the solar system orbit around it.
Planets are lighter in mass, but that doesn't mean they don't do anything
to our Sun; instead, our Earth tugs the Sun about 0.09 m/s in about 430 Km
radius, whereas Jupiter is massive enough to tug the Sun in a radius of
about 800,000 km at a speed of 13 m/s, that's why star or sun can't remain
in exact center of the planetary orbits, if there are massive planets.
There are three types of anomalies, but two of them are used to
define the position of a planet mainly. The mean anomaly assumes the
planet moves counterclockwise from its reset point or periapsis and
increases equally with time; that's why we mapped 0, 30, 60, 90......360°
or 0°, meaning every 30° until a whole round. Mean anomaly is like numbers
on a gauge meter.
You know that planets don't move at a uniform speed; the reasons are
discussed earlier. Instead, they tend to move faster near the periapsis or
0°, and they move at the slowest speeds around apoapsis or 180°.
Mean anomaly doesn't account for variations like gravitation,
perturbation, neighborhood interaction, etc. That's why we need a
real-time marker, which is called the True anomaly. If the Mean
anomaly acts as a gauge marker, then its needle would be the True anomaly.
True anomaly is also an angle that is formed by these three
components: a. The star or sun around the center, b. the planet, and c.
the periapsis. When you connect these 3 and measure the angle at the
star as in the image, you get the true anomaly. If you choose the
geometric center instead of the star while keeping the other two the
same, you'd be measuring the eccentric anomaly.
This way, both Mean and True anomalies help us to measure the planet's
position, whereas commonly known checkpoints like equinoxes could be
assigned at 90 and 270 degrees as well.
Tilted orbits:
Let's now see the parameters for tilted orbits because most planets and
moons or orbiting bodies have tilted orbits rather than flat paths.
Since you know the previous parameters, for tilted ones we add a few
other terms. Let's see them briefly.
A - Inclination
This tells us how much the orbit is tilted as compared to the
parent object, measured in degrees, of course. Parent object means if
you are measuring it for Earth, then the Sun would be the parent, while
for the Moon, the Earth is the parent. For Titan, Saturn acts as the
parent.
Also remember that our Earth is considered to orbit in a flat plane, and
all the other planets' paths are measured relative to the
ecliptic plane (13 constellations).
You saw earlier in the animation of the sun's movement that it seemed to
be moving in a flat plane, not going up or down. That's why our Earth's
orbit has no tilt, at least considered this way.
B - Nodes
It's natural that at some points the orbiting body might go toward the
north pole of the parent or the south pole instead of orbiting around
the ecliptic plane (13 constellations).
The point where it seems to move toward the north pole is called the
Ascending Node, and the point when it appears to move the
southwards, it's called the Descending Node. This is seen as an
orbiting object moving toward the north celestial pole. Celestial here
means the latitude projected in the sky we discussed earlier when we
talked about Imprisoned Earth.
There is a parameter called the longitude of the ascending node,
which is the same as the pericenter's longitude but used to track the
ascending node in Earth's sky.
The ascending node is an important checkpoint for tilted orbits, and a
planet or object starts to move northward. Both ascending and descending
nodes are located 180° apart; if you draw a line to connect them, it would
be called the line of nodes.
Suppose in a tilted orbit, if the ascending node lies at 25° anomaly, then
the descending node should be at 205°. Here's the twist: if the nodes were
at 25-205 at one time, they can move to 26-206, 27-207, 28-208, and so on;
this happens due to gravitational effects and other factors.
This period is different for every entity that orbits in a tilted path,
and there is a specific period when the node pairs meet again at the same
anomalies while maintaining the 180° rule. For our Moon, it's about 19
years.
In school, you might have heard that when the Sun, Earth, and Moon align
in a straight line, it causes eclipses. It's partially true because our
Moon orbits in a path that is tilted at 5.15°. For an eclipse, the Sun,
Earth, and Moon must align with either of the nodes, and those 180° apart
points tend to move every year; that's why eclipses are so rare.
Epoch
This is one of the most important components of any ephemeris; without
it, all the key information and values would be useless. The report of
the planetary position is called an ephemeris (plural: ephemerides); it
mentions most of the aspects and directions that many of them we've
discussed here.
Just like any other report, the time of the observation is also
important; otherwise, reports would be futile. To address the time,
astronomers use the Julian epoch, which is valid for one century
mainly.
Current ephemerides use J2000 as the Julian epoch; it would be valid for
this century, then J2100 would begin. Don't assume you could derive a
Julian epoch for any given year just by adding J before a year like J2025,
J2026, or J2027. You could do that if you follow the official rules:
Step-1: Convert the desired date into a Julian date, which is a
continuous day count from 4713 BCE.
Step-2: Use a nearby epoch like J2000; if we convert it into Julian
dates, then we get 2451545.0 Julian days (JD). We use J2000 as a
reference epoch.
Step-3: Subtract the JD from the JD of your desired date. For
example, if we choose 1st Jan 2027, then its JD is 2461120, and we
subtract 2461120 - 2451545 = 9575 days.
Step-4: Divide the result by 365.25 because one Julian year consists of
365.25 days. We got 26.21, and we add this number to J2000; hence, 2000
+ 26.21 = J2026.21.
By the way, you don't need to estimate the Julian epoch of every single
day or year, because planets change their orbital properties over such a
long time. Differences even in 2-3 decades are minute for slow-moving
planets like Saturn, Uranus, or Neptune, or some other properties. The one
Julian epoch usually works for a century unless you want extreme
precision.
Since we live in a constantly changing universe and gravitational effects
or orbital factors affect many astrometric properties over a long time,
that's why the Julian epoch tells us which planet's which parameter was in
the ephemeris at which time (which is valid for roughly 100 years)
Now you've got the basic idea of orbital and celestial mechanics as well
as Astrometry's basic principles. Let's see what the relationship is with
astrology.
Astrology
It might seem weird since an astronomy blog is mentioning astrology, but
we cover anything that is related to the sky or space. Let's define the
terms here so that you won't be confused. Astronomy is the science that
deals with where planets, stars, or celestial bodies are located in the
sky. It uses planes, references, constellations, and measurements that
we talked about in the last section; it is referred to as Astrometry.
Astrology's main roots are hidden in one of the world's oldest
scriptures, called the Vedas. They presented the Reincarnation theory,
which assumes we get several lifetimes instead of just one according to
our actions. Karma is reactive; once you've done something, then its
result will sooner or later manifest whether you like it or not.
Since many actions can't produce results in one lifetime, ancient Vedics
needed to measure this result's manifestation, like how long after we'll
get the result of certain Karma. This is where Astrology began.
For example, you put raw dough in an oven; after some time, it'd be
cooked and ready to eat. If you overcook it, then it's also ready to
dispose of. Here, the time matters based on the flame, flour's quality,
and ingredients. You measure the time with the help of the Sun because
our day is determined by the Sun, and we divide it into seconds,
minutes, or hours for ease. Vedics used several time systems based on
the Moon, Mercury, Mars, Jupiter, or Saturn, even with the cycle of
equinoxes, to measure certain things.
They tied certain qualities or results to certain planets and their
alignments, like Justice, honesty, power, and leadership to Jupiter. The
movement of Jupiter or any of its combinations, no matter how the
astrologers say it's imminent, won't manifest if you didn't perform any
suitable action for that result. Mostly they were accurate.
But now, after centuries of distortions, reincarnation and karma
have been ripped out of astrology. Modern astrology just calculates the
motions of planets and analyzes certain combinations and charges on you.
If this and that planets are here, then they will ruin your life, your
job would be lost, and you'll wander from prison to prison. Regardless
of what you have done.
That's why you hear pointless facts from astrologers like a
beautiful crush, a high-earning job, buying properties, adversaries,
luxury, art, calm, and pleasure in life. Sometimes, they will declare
you a future president or future terrorist, because they only look at
the planet's motion and you and your actions ........ are excluded.
Sometimes, certain astronomical events like transits, eclipses, and
other spectacular things are treated as a time to loot others' money in
the name of deities, worship, or celestial forces. Come on, they are
just planets and stars, revolving as they should; they can't punish or
reward us.
Since karma could be good or bad, modern astrologers tell people what
they want to listen to. Obviously, people won't throw money to listen to
their bad luck even if it's correct or just a made-up story. That's why
modern astrology is not worth, it misleads because its roots and
original workflows have been distorted, and nobody practices the
original one because they are almost lost.
Also, don't be concerned about the future; just care for 10%
past, 80% present, and 10% future. Why should we
worry about that time that has passed or is uncertain? So, make first
priority to present; also, don't be too careless.
Have a nice day!