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The Sun follows the solar circle (eccentricity e < 0.1) at a speed of about 255 km/s in a clockwise direction when viewed from the galactic north pole at a radius of ≈ 8.34 kpc [4] about the center of the galaxy near Sgr A*, and has only a slight motion, towards the solar apex, relative to the LSR. [5] [6]
Velocities for local objects are sometimes reported with respect to the local standard of rest (LSR)—the average local motion of material in the galaxy—instead of the Sun's rest frame. Translating between the LSR and heliocentric rest frames requires the calculation of the Sun's peculiar velocity in the LSR. [1]
This is because the distance between Earth and the Sun is not fixed (it varies between 0.983 289 8912 and 1.016 710 3335 au) and, when Earth is closer to the Sun , the Sun's gravitational field is stronger and Earth is moving faster along its orbital path. As the metre is defined in terms of the second and the speed of light is constant for all ...
Just before 7 a.m. on Dec. 24, the Parker Solar Probe passed within just 3.8 million miles of the sun’s surface — seven times closer to the burning ball of gas than any other mission has ...
The Earth's orbit is known with an absolute precision of a few meters and a relative precision of a few parts in 100 billion (1 × 10 −11). Historically, observations of Venus transits were crucial in determining the AU; in the first half of the 20th century, observations of asteroids were also important.
Average orbital speed of planet Earth around the Sun: 29 783: 97 713: 107 218: 66 623: The fastest recorded speed of the Helios probes: 70,220: 230,381: 252,792: 157,078: Recognized as the fastest speed achieved by a man-made spacecraft, achieved in solar orbit. Orbital speed of the Sun relative to the center of the galaxy: 251 000: 823 000: ...
The Hubble constant is most frequently quoted in km/s/Mpc, which gives the speed of a galaxy 1 megaparsec (3.09 × 10 19 km) away as 70 km/s. Simplifying the units of the generalized form reveals that H 0 specifies a frequency (SI unit: s −1 ), leading the reciprocal of H 0 to be known as the Hubble time (14.4 billion years).
Barnard's Star's transverse speed is 90 km/s and its radial velocity is 111 km/s (perpendicular (at a right, 90° angle), which gives a true or "space" motion of 142 km/s. True or absolute motion is more difficult to measure than the proper motion, because the true transverse velocity involves the product of the proper motion times the distance.