Velocidade Orbital da Terra

Earth's orbital speed by date

On average Earth moves around the Sun at roughly 29.78 km/s, which is about 107,000 km/h. The speed at any given moment comes from the vis-viva equation, v² = GM·(2/r − 1/a). Here GM is the Sun's gravitational parameter, r is the current Earth–Sun distance, and a is the semi-major axis (1 AU). Around perihelion in early January, r drops to about 0.983 AU and Earth picks up to roughly 30.3 km/s. At aphelion in early July, with r near 1.017 AU, it eases back to about 29.3 km/s. That swing of close to 1 km/s is just Kepler's second law showing up: equal areas swept in equal times.

Applications

Mission planners pick launch windows that borrow Earth's prograde velocity to throw a probe toward the outer planets. The same numbers feed gravity-assist trajectories such as Voyager's Jupiter slingshot, the JWST insertion at L2, and the delta-v budgets behind any interplanetary mission. It also makes a handy teaching example, since the answer changes with the calendar date.

FAQ

Does this include the Sun's motion through the galaxy? No. The figure is the orbital speed measured against the Sun. The Solar System as a whole circles the Milky Way at around 230 km/s, which is a separate motion entirely.

Why does Earth speed up at perihelion? Because angular momentum stays constant. When Earth is nearer the Sun and r shrinks, the tangential velocity has to rise to keep L = m·v·r the same.

How is this useful for a launch? A spacecraft sent off eastward already carries Earth's ~29.78 km/s with it. That head start cuts down a lot of the propellant you would otherwise burn to climb out of the Sun's gravity.