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One proposed model of dark energy has been named "quintessence" by its proponents, in honor of the classical element. [21] This idea relates to the hypothetical form of dark energy postulated as an explanation of observations of an accelerating universe. It has also been called a fifth fundamental force.
This system consisted of the four classical elements of air, earth, fire, and water, in addition to a new theory called the sulphur-mercury theory of metals, which was based on two elements: sulphur, characterizing the principle of combustibility, "the stone which burns"; and mercury, characterizing the principle of metallic properties.
List of NGC objects (2001–3000) List of NGC objects (3001–4000) List of NGC objects (4001–5000) List of NGC objects (5001–6000) List of NGC objects (6001–7000) List of NGC objects (7001–7840) List of IC objects; List of Messier objects; List of Caldwell objects; List of Herschel 400 objects; List of Melotte objects; List of ...
The units are length 2 time −2, i.e. velocity squared, or energy per mass. Every object in a 2-body ballistic trajectory has a constant specific orbital energy equal to the sum of its specific kinetic and specific potential energy: = = =, where = is the standard gravitational parameter of the massive body with mass , and is the radial ...
It is by far the most important source of energy for life on Earth. The Sun has been an object of veneration in many cultures. It has been a central subject for astronomical research since antiquity. The Sun orbits the Galactic Center at a distance of 24,000 to 28,000 light-years. From Earth, it is 1 astronomical unit (1.496 × 10 8 km) or ...
This list contains natural objects up to apparent magnitude 3.5. All objects are listed by their visual magnitudes, and objects too close together to be distinguished are listed jointly. Objects are listed by their proper names or their most commonly used stellar designation. This list does not include transient objects such as comets, or ...
Because of its increased surface area, the surface of the Sun will be cooler (2,600 K (4,220 °F) at its coolest) than it is on the main sequence. [30] The expanding Sun is expected to vaporize Mercury as well as Venus, and render Earth and Mars uninhabitable (possibly destroying Earth as well).
The following is a list of Solar System objects by orbit, ordered by increasing distance from the Sun. Most named objects in this list have a diameter of 500 km or more. The Sun, a spectral class G2V main-sequence star; The inner Solar System and the terrestrial planets. 2021 PH27; Mercury. Mercury-crossing minor planets; Venus. Venus-crossing ...