You can look through a list of the planets' orbits to see which one has the smallest eccentricity, and the answer is Venus, 0.006787.
But if you are an astronomer wanting to find it out by observing the planets in the sky, you need to have five accurate positions for each planet, spaced out across a good fraction of the orbit, and then you can calculate the 'elements' of the orbit. One of the elements is the eccentricity.
The eccentricity and the semimajor axis determine the shape and size of the orbit. Then there is the longitude of perihelion, which sets the orientation of the major axis of the ellipse. Two more are the inclination of the plane of the orbit to the plane of the Earth's orbit, and then the longitude of the ascending node, which defines the line of intersection of the two planes. Finally the longitude at the Epoch and the date of the Epoch are required because they set the starting conditions for the model.
I can tell you that it is not a circle.
The Earth makes an elliptical orbit around the Sun, not a circular orbit. The names Earth and Sun are proper names for our planet and star, so they usually get a capital letter. What is one complete orbit called? A "siderial period". And the time it takes: one year.
The word orbit can be either a noun, in which case it means the path taken by one object (such as a planet) as it circles around another object (such as the sun) or it can be a verb, meaning to follow such a path.
Earth's orbit is not highly elliptical; it has a modest eccentricity of 0.0167. An eccentricity of zero defines a perfectly circular orbit. Pluto's eccentricity is 0.248, and Mercury's is 0.2056. Neptune's largest moon, Triton, has as perfectly circular an orbit as can currently be measured. See link for more.
You tell me
The planet will orbit the sun, while moons orbit the planet.
I can tell you that it is not a circle.
A planet is in direct orbit around a central star, while a moon is in orbit around a large body (a planet) rather than in a direct orbit around a star. The moon orbits the planet, while the planet orbits the sun.
It takes five good observations to find the orbital elements for a planet. The observations need to be taken over enough time for the planet to cover a good fraction of the orbit. That allows an ellipse to be fitted to the measurements.
The semi-major axis (size) and the eccentricity (shape).
A planet with an at-most-fear (get it?) will have sort-of a grayish white cloud surrounding it.
Unfortunately, not all clocks are circular. The reason that most clocks are circular is because of convenience. As clocks rely on the rotation of the hands to tell time, it is simply easier for the numbers to be arranged in a circular formation around it.
a galaxy is a collection of Stars and planets while a planet is simply a large mass of rock, in orbit round a star. If you wanted to be able to distinguish the two from each other by simply looking at them in the sky, this is impossible.
The Earth makes an elliptical orbit around the Sun, not a circular orbit. The names Earth and Sun are proper names for our planet and star, so they usually get a capital letter. What is one complete orbit called? A "siderial period". And the time it takes: one year.
There are two ways you can tell if a star may have a planet around it. One way is that the star would have a slight wobble in its motion across our sky. This is caused by the planet's gravitational pull on the star which would cause a slight movement or shift in its alignment. More easily detectable by modern telescopes would be a periodic reduction in the level of light coming from the star. The key is the period in which the light reduction occurs, which would offer a clue as to the period of the orbit of the planet around the star as it blocks light during its orbit.
It means the sun has a massive gravitational pull.
Today's knowledge is limited. Hold this question for 100000 years. We may tell 1%right answer. Because we know only gravity, repulsion, attraction,...., but future is one orbit may be the other planet outer most orbital.