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Stellar dynamics also has connections to the field of plasma physics. [2] The two fields underwent significant development during a similar time period in the early 20th century, and both borrow mathematical formalism originally developed in the field of fluid mechanics.
Typical examples are the halo stars passing through the disk of the Milky Way at steep angles. One of the nearest 45 stars, called Kapteyn's Star, is an example of the high-velocity stars that lie near the Sun: Its observed radial velocity is −245 km/s, and the components of its space velocity are u = +19 km/s, v = −288 km/s, and w = −52 ...
The comoving distance from an observer to a distant object (e.g. galaxy) can be computed by the following formula (derived using the Friedmann–Lemaître–Robertson–Walker metric): = ′ (′) where a(t′) is the scale factor, t e is the time of emission of the photons detected by the observer, t is the present time, and c is the speed of ...
The Collisionless Boltzmann equation, also called the Vlasov Equation is a special form of Liouville' equation and is given by: [3] + = Or in vector form: + = Combining the Vlasov equation with the Poisson equation for gravity: =. gives the Jeans equations.
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In observational astronomy, culmination is the passage of a celestial object (such as the Sun, the Moon, a planet, a star, constellation or a deep-sky object) across the observer's local meridian. [1] These events are also known as meridian transits, used in timekeeping and navigation, and measured precisely using a transit telescope.
In this example the time measured in the frame on the vehicle, t, is known as the proper time. The proper time between two events - such as the event of light being emitted on the vehicle and the event of light being received on the vehicle - is the time between the two events in a frame where the events occur at the same location.
In orbital mechanics, Kepler's equation relates various geometric properties of the orbit of a body subject to a central force.. It was derived by Johannes Kepler in 1609 in Chapter 60 of his Astronomia nova, [1] [2] and in book V of his Epitome of Copernican Astronomy (1621) Kepler proposed an iterative solution to the equation.