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Comparative sizes of planets and stars

Comparative sizes of the terrestrial planets

 Automatic translationAutomatic translation Category: Planets and dwarf planets
Updated June 01, 2013

Our Universe is really vast and empty, though a few grains of matter dotting the cosmic void, from small dust grains to the biggest stars. Between small planets in the solar system and the biggest stars, the size difference is enormous, for example, the diameter of the star Betelgeuse is 141,863 times larger than the diameter of the Earth.
This page shows pictures of some comparisons between the sizes planets and between stars. In the solar system, the Sun captured 99.86% of the total mass of dust and gas from the original nebula.

 

Jupiter, the largest planet in the system, has captured 71% of the remainder. The other planets are shared the residue of the gravitational evolution, i.e. 0.038% of the total mass. The four terrestrial planets represent only 11.17% of the total mass of the solar system planets.

Image: Comparative sizes of 4 terrestrial planets, Mercury left, Venus, Earth and Mars. These four terrestrial planets represent only 11.17% of the total mass of the solar system planets.

 comparative sizes of the terrestrial planets

Size comparison of planets with Earth

    
Size comparison of dwarf planets with Earth 

A dwarf planet, since the new definition of August 2006, is a celestial body orbiting the Sun that has sufficient mass for its self-gravity to outweigh the cohesive forces of the solid body and assumes a hydrostatic equilibrium (in a nearly spherical shape), and which is not a satellite, but does not clear up in its orbital neighborhood.

Image: Comparative sizes of trans-Neptunian objects, located in the Kuiper Belt, compared to the size of the Earth (left).

Neptune is in the outer solar system, 4.5 billion km. Neptune is four times larger than the earth.

Image: Compare the size of Neptune with the Earth. In this picture you can see the dark blue anticyclone, comparable to the Great Red Spot of Jupiter, that it is twice as large (pictured right).

 Neptune size compared to the size of the Earth

Comparison of the sizes of stars

    
size of giant stars relative to the sun 

Image: Comparative sizes of some super giant stars like Antares, Betelgeuse, Rigel, Aldebaran and some white dwarfs as Arcturus, Pollux, Sirius and the Sun (left). It is thanks to the Stefan-Boltzmann law, which astronomers can easily calculate the radii of the stars (see note below). In 1879, the Austrian physicist Josef Stefan, who is interested in radiation from hot bodies, discovers that the total energy emitted by an object is proportional to the 4th power of its absolute temperature. Antares has a diameter of ≈ 700 times that of the Sun, or about 1 billion kilometers. Betelgeuse has a diameter ≈ 1300 times that of the Sun. Aldebaran has a diameter ≈ 45 times that of the Sun. Rigel has a diameter of about 116 million km, ≈ 35 times that of the Sun. Arcturus is 20 times bigger than the sun. Pollux is ≈ 8 times larger than the sun.

nota: Thanks to the Stefan-Boltzmann law, astronomers can calculate the radii of the stars. The brightness of a star is: L = 4πσR2T4
L is the brightness, σ is the Stefan-Boltzmann constant, R the radius of the star and T the temperature.
 size of the Earth compared to a white dwarf

Image: Size of the Earth compared to the size of a white dwarf (left). White dwarfs are stars off residues. This is the penultimate phase of the evolution of stars whose mass is between 0.3 and 1.4 times that of the Sun. The density of a white dwarf is very high. A white dwarf of about one solar mass has a radius of the order of that of the Earth.

Video on the size of planets and stars

    
 

Our Sun is very small, compared to some stars. The planets are as dust compared to blue and red Giant of our universe. This video on YouTube, the relative sizes of the planets and stars are made ​​of the smallest to the largest.
The video shows first, our Moon, the planets of our arranged in order of increasing size solar system and the Sun. Then go scrolled, the biggest stars of our galaxy. Their approximate sizes were calculated from their brightness, their temperatures, they even deducted from their colors, and their distances.

 

Video: Comparative sizes of some giant and supergiant stars like Antares, Betelgeuse, Rigel, Aldebaran, Pistol star Antares A Mu Cephei, the red hypergiant VY Canis Majoris and some white dwarfs as Arcturus, Pollux, Sirius and the Sun. credit & Copyright: morn1415 (YouTube)

nota: VY Canis Majoris (VY CMa) is a red star hypergiant type, which is located in the constellation Canis Major, at 5000 light years from our Sun. VY Canis Majoris is the largest known star and one of the brightest.

Apparent size of the Moon and the Sun

    

Distance from the Sun varies throughout the year between 147,098,074 km and 152,097,701 km, it is a function of the eccentricity of Earth's orbit and hence its apparent size as seen from Earth also varies. The distance of the Moon varies during the month between 363,104 and 405,696 km, it is a function of the eccentricity of the lunar orbit and hence its apparent size as seen from Earth also varies. When the Moon is at its apogee, that is farthest from the Earth, its apparent diameter is smaller than that of the sun at this point of its orbit is too small to completely cover the solar disk. When the Moon is at perigee, i.e. closer to the Earth, its apparent diameter is larger than that of the Sun, at this point in its orbit is large enough to completely cover the solar disk. Two or three times a year, Solar Dynamics Observatory of NASA observed the moon passing in front of the sun, as the right image taken on October 7, 2010.

 Size comparison between Earth and the Moon

Image: Comparison of diameters of the Earth and the Moon. File created by NASA in the public domain.

 Apparent size of the Moon and the Sun

Image: Apparent size of the Moon and the Sun. Credit: NASA/SDO/LRO/GSFC

Size of Earth relative to Sun

    

Earth is small compared to the Sun, in the volume of the Sun could put more than a million Earths (1,305,620). Its average diameter is ≈ 12 742 km and that of the Sun, ≈ 1,392,684 km (≈ 109 times larger). The image shows the size ratio Earth / Sun, if the Earth stood on the same plane, very close to the Sun. Since April 2010 the mission of the Space Telescope SDO is to examine the sun's magnetic field, it allows a better understanding of the solar atmosphere and the role Sun plays on climate and atmospheric chemistry of the Earth. The telescope has 10 CCDs high quality in visible light which are also designed for the detection of light in the extreme ultraviolet. SDO located on the geosynchronous orbit, provides images with 10 times better than HDTV clarity.

nota: The GSO or geosynchronous orbit is a geocentric orbit in which a satellite moves in the same direction as the Earth (west to east) and whose orbital period is equal to the sidereal rotation period of the Earth (approximately 23 h 56 min 4.1 s). This orbit has a semi-major axis of about 42 200 km. If the orbit is in the plane of the equator, the satellite appears as a fixed point in the sky. It is then called "geostationary orbit". The geostationary orbit is a geosynchronous orbit which has an inclination and a zero eccentricity. If the orbit is inclined to the plane of the equator, the satellite discloses an analemma in the sky when viewed from a fixed point on the surface of the Earth.

 
  Mean radius
(km)
Number of planets in
one solar volume
     
Mercury 2 440 23 251 902
Venus 6 052 1 523 400
Earth 6 371 1 305 620
Mars 3 390 8 670 834
Jupiter 69 911 988
Saturn 58 232 1 710
Uranus 25 362 20 697
Neptune 24 622 22 620
Sun 696 342 1

Table: number of planets, contained in a solar volume. How many Earths contains the volume of the Sun?
response: 1 305 620 Earths (Volume of a sphere = 4πR3/3).

Image:  Approximate size of the Earth relative to the Sun if it is located on the same plane. This spectacular solar image taken by SDO telescope (Solar Dynamics Observatory) shows in detail a huge eruption that caused this large bulge matter around March 30, 2010. In this beautiful ring of light, we could put 100 Earths. Image Credit: NASA/SDO/AIA.

 Size of Earth relative to Sun
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