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Perihelion

Astronomy  Perigee  Perihelion distance

Perihelion
A planet in an elliptical orbit around the Sun is closest to the Sun at perihelion.
For a planet, comet or other celestial body moving around the Sun in an elliptical orbit, the distance between the object and the Sun changes throughout the orbit.


Perihelion!
Does the Sun look a little brighter to you? Maybe that's because at nine minutes after midnight (UT) tonight, January 2/3, the Earth will be at perihelion, the closest point on its elliptical orbit to the Sun.

perihelion at HighBeam Research
perihelion on Wikipedia
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Pictures from Google Image Search ...

Aphelion - the point in an orbit that is farthest from the sun.
Perihelion - the point in an orbit that is closest to the sun.
Sun - the star in our Solar System.
Planet - a large celestial body that orbits a star.

perihelion The closest approach to the Sun of any object in orbit about it.
period The time needed for an orbiting body to complete one revolution about another body.

Perihelion Distance
The distance between the orbiting body and the sun at it's closest approach.

~ - The point in an object’s orbit when it is closest to the sun. At this point in the orbit, the planet is moving at its maximum speed (Kepler's Second Law). The perihelion refers specifically to orbits around the Sun, and is equivalent to the periapsis of a general orbit.

~ -- the point in the orbit of the Earth that is closest to the Sun. Currently the Earth reaches ~ in early January.
prominence -- a large-scale gaseous formation above the surface of the Sun.

~
All of the planets in our Solar System move around the Sun in elliptical orbits. An ellipse is a shape that can be thought of as a "stretched out" circle or an oval as in the diagram below. The Sun is not at the centre of the ellipse, as it would be if the orbit were circular.

~
The point in the orbit of an object orbiting the Sun where it is closest to the Sun's center of mass. Earth's perihelion occurs early in January.
Period ...

~
The point in an object's orbit when it is closest to the Sun (Helios = Sun). Earth is at perihelion each year on about Jan. 3.
Period
The time an object takes to complete a certain motion and return to its original state, e.g. period of revolution.

~- a planet or comet's closest approach to the sun
Periodic time- (see sidereal period)
Perturb- to cause a planet or satellite to deviate from a theoretically regular orbital motion ...

~ The position in a heliocentric orbit at which the orbiting object is at its least distance from the Sun.
Phase The percentage illumination, from the observer's perspective, of an object (normally planet or Moon).

~
The point in its orbit where a planet is nearest the Sun.
period-luminosity relation
A relationship between the period and average density of a pulsating star.

~
The point in its orbit where a planet is at its closest to the Sun. Opposite of aphelion.
period-luminosity relationship
The predictable relation between the pulsation period and changes in luminosity of a Cepheid variable star.

~
The point in its orbit where a planet is closest to the Sun. when referring to objects orbiting the Earth the term perigee is used; the term periapsis is used for orbits around other bodies. (opposite of aphelion) ...

~
the point in the orbit of a planet or other body where it is closest to the Sun.
Perturb
to cause a planet or satellite to deviate from a theoretically regular orbital motion.

~: Point in the elliptical orbit of a comet about the Sun in which it passes closest to the Sun.

~: The orbital point of closest approach to the sun.
period-luminosity relation: The relation between period of pulsation and intrinsic brightness among Cepheid variable stars.
permitted orbit: One of the energy levels in an atom that an electron may occupy.


~
The perihelion is a planet or comet's closest approach to the Sun. The Earth is at perihelion (the Earth is closest to the Sun) in January.
...

~:
The point on an orbit nearest the sun.
Planet:
Large spherical object shining by a star. Our planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto (+Charon ?) ...

~ and Aphelion are the planet's closest and furthest distances from the Sun, measured in Astronomical Units (AU). 1 AU is defined by the average distance from the Earth to the Sun.
The globes of the planets ...

~
When the orbit of a planet takes it to the point closest to the Sun.
Planet ...

~
When an object which revolves around the Sun is at the closest point it gets to the Sun.
Perturbations ...

~ -- The point in the path of a planet, asteroid, comet, or other body that is closest to the sun.
Proteus -- In Greek mythology, the son of Poseidon. Personification of the shifting winds and moods of the sea.

~ - (n.)
The near point to the sun of the orbit of a body orbiting the sun.
periodic table - (n.) ...

At ~, when the Earth is closest to the sun, the Earth has a greater angular speed (by Kepler's second law), so the sun has a greater angular speed relative to the Earth.

After perihelion, Comet ISON will fade rapidly, and will keep brighter than magnitude +2 or +3 for just a few days. This is about as bright as the stars in Orion's belt. Although not very bright, Comet ISON will display a spectacular tail, 30 or even 45 in length.

2.74 at perihelion
*This table is mainly from the 1965 edition of the Dictionary of Technical Terms for Aerospace Use (NASA SP-7).
Links ...

Aphelion / Perihelion is an object's orbital point (in distance and time) around a star where the object's distance (on its elliptical orbit) from its parent star is farthest / closest.

At present, perihelion occurs during the Southern Hemisphere's summer, and aphelion is reached during the southern winter. Thus the Southern Hemisphere seasons are somewhat more extreme than the Northern Hemisphere seasons, when other factors are equal.
[edit] Orbital inclination ...

~ That point in a solar orbit which is nearest the sun. That orbital point farthest from the sun is called aphelion. The term ~ should not be confused with parhelion, a form of halo. period 1. The interval needed to complete a cycle. 2. = orbital period. 3.

perigee ~ point in the path of a body orbiting the Sun where it is closest to the Sun. period period table period-luminosity relation perturbation disturbance in the normal movement of an orbiting body arising from an external force, usually gravitational.

~---point on a planet's orbit that is closest to the Sun. It is on the major axis.
Aphelion---point on a planet orbit that is farthest from the Sun. It is on the major axis directly opposite the ~ point. The aphelion + ~ = the major axis.

That is an ellipse with ~ P (point closest to the Sun) at the orbit of Earth and aphelion A (point most distant from the Sun) at the orbit of Mars (drawing). A similar transfer ellipse, between low Earth orbit (say, r = 1.1 RE = 1.1 Earth radii) and the synchronous orbit at 6.

2616 light years penumbra the incomplete part of a shadow surrounding the umbra perigee the innermost point of a terrestrial orbit ~ the innermost point of a solar orbit phase the fracton of the illuminated part of the Moon or other planetary object as seen by the observer ...

(opposite of ~) arcuate having the form of a bow; curved; arc-shaped Arago, Dominique François Jean 1786 - 1853 French astronomer and physicist and Director of the Paris Observatory, who discovered the phenomenon of the production of magnetism by rotation d'Arrest, ...

0 au, and ~ distances qSee also: Asteroid, Aten asteroids, ~ distance, Semimajor axis Asteroid One of a number of objects ranging in size from sub-km to about 1000 km, most of which lie between the orbits of Mars and Jupiter; also called 'minor planet'.

This is because approximately four days prior to ~, Mercury's angular orbital velocity exactly equals its angular rotational velocity so that the Sun's apparent motion ceases; at ~, Mercury's angular orbital velocity then exceeds the angular rotational velocity.

Aphelion is when it is furthest from the Sun and ~ is when it is closest to the Sun. The distance between the Earth and the Sun is always changing. If that is the case, how can you answer a question like "How far is the Sun from the Earth"?

It was known well before Einstein that these effects cause the axis of the orbit of Nercury to rotate slowly, so that its point of closest approach to the sun, the ~, moves or precesses from orbit to orbit, as shown in the figure to the right from NCSA's Relativity site.

Mean distance from Sun 149,598,500 km (8.3 lt-min): ~ distance (early January) 147,100,000 km; aphelion distance 152,100,000 km; vorb 29.78 km s-1; orbital period 365d.2564; e = 0.0167, i = 0; obliquity (1973) 2326'34". Albedo 0.

Hale-Bopp is a long-period comet that was discovered in 1995 and that reached ~ in Spring, 1997.

In terms of orbital elements, NEOs are asteroids and comets with a ~ (q) distance less than 1.3 times the Earth-Sun distance (AU). Near-Earth Comets (NECs) are further restricted to include only short-period comets -- that is, with an orbital period (P)less than 200 years.

" Perihelic means Mars is near ~--its closest distance to our Sun. Remember that the orbit of Mars, like that of all planets, is an ellipse, so the distance between the Sun and Mars changes as it goes around its orbit.

Pluto has an atmosphere when it is close to ~; the atmosphere may freeze out as Pluto moves farther from the Sun. It is thought by some that Pluto shares its atmosphere with its moon. Pluto was determined to have an atmosphere from an occultation observation in 1988.

The cosmological constant will also cause a precession of the ~ of a planet.

Apollo asteroids have semimajor axes (a) that are greater than or equal to 1 AU and ~ distances that are less than or equal to 1.0 AU; thus, they cross the Earth's orbit when near the perihelia of their orbits.

149,597,870 km ~
0.983 AU Aphelion
1.017 AU Eccentricity
0.01671022 Orbital period
365.25636 days Avg. Orbital Speed
29.7859 km/s Inclination
0.00005 Satellites
1 (the Moon) Satellite of
Sun Physical characteristics Equatorial diameter
12,756.3 km Surface area
5.10072108 km2 Mass
5.

It is at ~ on January 2, at a distance 3% closer than aphelion in July. Climatic changes are closely linked to temperature variations. A lowering of temperature creates more ice which increases albedo and reflects more radiation, reinforcing the cold.

In terms of orbital elements, NEOs are asteroids and comets with ~ distance q less than 1.3 AU. Near-Earth Comets (NECs) are further restricted to include only short-period comets (i.e., orbital period P less than 200 years). The vast majority of NEOs are asteroids (NEAs).

Asteroids belonging to the class most distant from Earth-those asteroids that can cross the orbit of Mars but that have ~ distances greater than 1.3 AU-are dubbed Mars crossers. This class is further subdivided into two: shallow Mars crossers (~ distances no less than 1.

Records of observations of Mars indicate that dust storms occur around the time of southern Summer Solstice (270 Ls), soon after ~ passage (250 Ls).

After the comet reaches ~ on November 28 and swings around the Sun, that's the end of the show for deep-southern observers. ISON will only become visible in the northern hemisphere from then onward.

For example, if we consider an orbit just like that in the standard position, but with "~" pushed back a degree, see that then the line of nodes will be on the y axis. "~" will be 90 from the line of nodes and the ascending node will be -90 from north. Thus: ...

Mercury is in a highly eccentric orbit around the Sun. At its closest (~), it is only 28.6 million miles from the Sun while, at its most distant (aphelion), it is 43.5 million miles. Its orbit ~ moves backward (precesses) around the Sun at a very slow rate.

When Mars is at opposition and also near ~ (Mars' closest approach to the Sun) -- as it was in August of 2003 -- the Martian opposition is especially close.

"We completed our first ~ passage from orbit on Sunday, our first Mercury year in orbit on Monday, our first superior solar conjunction from orbit on Tuesday, and our first orbit-correction maneuver on Wednesday.

Asteroid, Apollo: Asteroids with a semi-major axis greater than 1 AU but ~ less than 1.017 AU.
Asteroid, Aten: Asteroids with a semi-major axis less than 1 AU.
Asteroid, Centaur: Asteroids that lie between the orbit of Jupiter and Neptune.

Orbital Eccentricity
PlanetOrbital EccentricityPerihelion
(Point in Orbit Closest to Sun)
measured in AU'sAphelion
(Point in Orbit Farthest from Sun)
measured in AU's
Mercury ...

anomaly ((astronomy) position of a planet as defined by its angular distance from its ~ (as observed from the sun))
periapsis; point of periapsis ((astronomy) the point in as orbit closest to the body being orbited) ...

The point at which a planet is closest to the sun is called ~. The farthest point is called aphelion. Image Credit: NOAA
View Larger Image → ...

It was known that it correctly accounted for the "anomalous" precession of the ~ of Mercury and on philosophical grounds it was considered satisfying that it was able to unify Isaac Newton's law of universal gravitation with special relativity....
and frame-dragging ...

Periodic comets, also called short-period comets, have orbital periods of less than 200 years or which have been observed during at least one ~ passage. Tail debris from some comets are what cause certain annual meteor showers.

See also: See also: What is the meaning of Sun, Orbit, Earth, Planet, Solar?

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