CONCEPTS

What is an orbit?

We explain what an orbit is and what is its meaning in the area of ​​chemistry. What is an elliptical orbit and the orbits of the Solar System.

  1. What is an orbit?

In physics , orbit refers to the path described by a body around another , around which it revolves by the action of a central force, such as the gravitational force in the case of the celestial stars . In less words, it is the trajectory that an object traces when moving around a center of gravity by which it is attracted, in principle without ever impacting it, but also not moving away from it at all.

The orbits are from the seventeenth century, when Johannes Kepler and Isaac Newton formulated the basic physical laws that govern them, an important concept for the understanding of movement in the universe , especially as regards celestial stars, and also chemistry subatomic

An orbit can have various shapes, either elliptical, circular or elongated , and can be parabolic (parabola-shaped) or hyperbolic (hyperbola-shaped). In any case, every orbit comprises the following six Keplerian elements:

  • Tilt of the plane of the orbit (represented by the sign i).
  • Length of the ascending node (represented by the Ω sign).
  • Eccentricity or degree of deviation of a circle (represented by the sign e).
  • Axis semi-major axis, or half the longest diameter (represented by the sign a).
  • Argument of the perihelion or periastro, the angle that goes from the ascending node to the periastro (represented by the sign ω).
  • Mean anomaly of the time, or the fraction of orbital time elapsed and represented as an angle (represented by the sign M0).
  1. Orbit in chemistry

atomic orbital
Each atomic orbital is expressed with a number and a letter.

In chemistry , there is talk of orbits about the movement of electrons around the nucleus of atoms , around which they are attracted by the difference in electromagnetic charges they present (negative in electrons and positive in the nucleus of protons and neutrons ). These electrons do not have a defined trajectory, but they are known to trace different orbits known as atomic orbitals, depending on the degree of energy they harbor.

Each atomic orbital is expressed with a number and a letter . The number (1, 2, 3… until 7) denotes the energy levels with which the particle moves, while the letter (s, p, dyf) denotes the shape of the orbital.

  1. Elliptical orbit

An elliptical orbit is one that, instead of a circle, draws an ellipse, that is, a flat and elongated circle . This figure, the ellipse, has two foci, where the central axes of each of the two circles that compose it would be; In addition, this type of orbit has an eccentricity greater than zero and less than one (0 is equivalent to a circular orbit and 1 to a parabolic).

Every elliptical orbit has two notable points:

  • Periapsis The closest point of the orbital path to the central body around which the orbit is drawn (and located in one of the two foci).
  • Apoapsis The furthest point of the orbital path to the central body around which the orbit is traced (and located in one of the two foci).
  1. Solar System Orbits

Mercury - orbit
The planet Mercury is the most eccentric orbit, perhaps because it is closer to the Sun.

The orbits described by the stars of our solar system are, as in most planetary systems, of a more or less elliptical type . In the center of it is the star of the system, our sun, whose gravity keeps the planets in motion ; while comets in their respective parabolic or hyperbolic orbits around the Sun do not have a direct bond with the star. On the other hand, the satellites of each of the planets also trace orbits around each one, as does the Moon with the Earth .

However, the stars also attract each other, generating mutual gravitational disturbances, causing the eccentricities of the orbits to vary with time and with each other. For example, the planet Mercury is the most eccentric orbit , perhaps because it is closer to the Sun, but it is still on the Mars list, much further. Venus and Neptune, on the other hand, have the least eccentric orbits of all.

  1. Earth orbit

The Earth, like its neighboring planets, orbits the Sun in a slightly elliptical path , which takes approximately 365 days (one year) and we call translational motion . This displacement occurs at about 67,000 kilometers per hour.

At the same time, there are four possible orbits around the Earth, for example, for artificial satellites:

  • Low orbit (LEO). From 200 to 2,000 km of the planetary surface.
  • Middle orbit (MEO). From 2,000 to 35,786 km of the planetary surface.
  • High orbit (HEO). From 35,786 to 40,000 km of the planetary surface.
  • Geostationary Orbit (GEO). At 35,786 km of the planetary surface. This is the orbit synchronized with the Earth’s equator, endowed with zero eccentricity and to which an object looks motionless in the sky for Earth observers.

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