مدار الأرض
في فهم الفلك، المدار الأرضي، هوحركة الأرض حول الشمس، من متوسط مسافة 149.59787 مليون كم. المدار الكامل للأرض حول الشمس يحدث جميع 365.2563666 mean solar يوم (1 sidereal سنة). This motion gives an apparent movement of the Sun with respect to the stars at a rate of about 1°/day (or a Sun or Moon diameter every 12 hours) eastward, as seen from Earth. On average it takes 24 hours—a solar day—for Earth to complete a full rotation about its axis relative to the Sun so that the Sun returns to the meridian. The orbital speed of the Earth around the Sun averages about 30 km/s (108,000 km/h), which is fast enough to cover the planet's diameter (about 12,700 km) in seven minutes, and the distance to the Moon of 384,000 km in four hours.
Viewed from a vantage point above the north poles of both the Sun and the Earth, the Earth would appear to revolve in a counterclockwise direction about the Sun. From the same vantage point both the Earth and the Sun would appear to rotate in a counterclockwise direction about their respective axes.
المسافة التي يشغلها المدار
تاريخ الدراسة
التأثير على الأرض
أحداث في المدار
| epoch | J2000.0 |
| aphelion | 152,098,232 kiloمترs (4.99009948×1011 قدم) 1.01671388 AU |
| perihelion | 147,098,290 kiloمترs (4.8260594×1011 قدم) 0.98329134 AU |
| semimajor axis | 149,598,261 kiloمترs (4.90807943×1011 قدم) 1.00000261 AU |
| eccentricity | 0.01671123 |
| inclination | 7.155° to Sun's equator 1.578690° to invariable plane |
| longitude of the ascending node | 348.73936° |
| argument of periapsis | 114.20783° |
| الفترة | 365.256363004 يوم 1.000017421 yr |
| متوسط السرعة | 29.78 كيلومتر في الثانية (18.50 ميل/ث) 107,200 كيلومتر في الساعة (66,600 ميل/س) |
المستقبل
انظر أيضاً
- Barycentric coordinates (astronomy)
- دوار الأرض
- مدار متمركز حول الأرض – مدار أي جسم يدور حول الأرض، مثل القمر أوالسواتل الصناعية.
- ساتل
- محطة فضاء
الهوامش
- ^ A solar day (one rotation relative to the Sun) is on average 24 hours; it takes 365.256363 of these to orbit the Sun once in the sense of returning to the same position relative to the stars. Such an orbit relative to the stars is called a sidereal year.
- ^ All astronomical quantities vary, both secularly and periodically. The quantities given are the values at the instant J2000.0 of the secular variation, ignoring all periodic variations.
- ^ aphelion = a × (1 + e); perihelion = a × (1 – e), where a is the semi-major axis and e is the eccentricity.
- ^ The reference lists the longitude of the ascending node as −11.26064°, which is equivalent to 348.73936° by the fact that any angle is equal to itself plus 360°.
- ^ The reference lists the longitude of perihelion, which is the sum of the longitude of the ascending node and the argument of perihelion. That is, 114.20783° + (−11.26064°) = 102.94719°.
المصادر
- ^ Williams, David R. (2004-09-01). "Earth Fact Sheet". NASA. Retrieved 2007-03-17.
- ^ Standish, E. Myles; Williams, James C. "Orbital Ephemerides of the Sun, Moon, and Planets" (PDF). International Astronomical Union Commission 4: (Ephemerides). Retrieved 2010-04-03.CS1 maint: multiple names: authors list (link) See table 8.10.2. Calculation based upon 1 AU = 149,597,870,700(3) m.
- ^ Allen, Clabon Walter; Cox, Arthur N. (2000). . Springer. p. 294. ISBN .CS1 maint: multiple names: authors list (link)
- ^ Staff (2007-08-07). "Useful Constants". International Earth Rotation and Reference Systems Service. Retrieved 2008-09-23.
