When the mass of an orbiting body is small enough to ignore, the same value of K can be used for all small objects orbiting around the same central body. In other words, given the orbital period of one satellite, it's easy to calculate the periods of others. This is also known as "Kepler's Third Law. The location of the greatest distance between the orbiting body and the central body when the orbit is an ellipse.
The apocenter is diametrically opposite the pericenter on the major axis of the orbit. The angle from the ascending node to the pericenter , measured in the plane of the orbit. Nobody knows why it's called "Argument". A measure of how elongated the orbit is. As planets are discovered and removed by the community within the literature and within the astronomical community, the exact number and disposition of the planets many change.
The light curves of known planetary transits were contributed by a number of astronomers. The proper motion of a star is the vector motion i. It is usually provided in the Equitorial coordinate system as the proper motion in the Right Ascension direction and the proper motion in the Declination direction. The stellar radial velocity is the velocity of a star along the observer's line of sight. Negative radial velocities imply motion towards the observer.
Radial velocity curves of known planetary transits were contributed by a number of astronomers. References for individual radial velocity curves are given on the respective page. Selecting the 'Output' box will show the radial velocity curves available for a given transiting planet.
Selecting the 'Include Stars with No Value' box will find those stars for which there are no radial velocity curves in the Exoplanet Archive database. The stellar radial velocity is the velocity of a star in the direction along the line of sight.
The Radial Velocity Wobble is the magnitude by which a companion body to the star will perturb the radial velocity of the star. The Radial Velocity Wobble depends on the distance between the star and the companion body, the mass of the star, the mass of the companion body, and the inclination of the companion's orbit with respect to the observer's line of sight.
For an Earth-like planet, the values stored in the Exoplanet Archive are calculated by placing a one earth mass planet at the center of the Habitable Zone and assuming an inclination angle of 33 degrees for the planet's orbital plane relative to our line of sight.
The stellar radius is defined as the distance between the center of the star and its surface. The Exoplanet Archive stores both published and calculated values of the stellar radius. Calculated values of the stellar radius come from the relationship between the radius R in cm , the effective temperature T eff in K and the luminosity L in erg sec -1 of the star:. Published values of the stellar radius come from direct interferometric measurements. The Rossby number is a dimensionless number defined to parameterize the level of stellar magnetic activity.
In a star, the magnetic dynamo mechanism operates in a highly conductive plasma which is subject to convective and rotational motions. The Rossby number is the ratio of the characteristic time scales of rotation rotational period and convection convective turnover time :.
The rotation period of a star is the amount of time the star takes to complete one rotation about its axis. The Exoplanet Archive stores the rotation period values in units of days. The Observed Semi-Major Axis is the orbital semi-major axis, typically inferred from Keplerian orbital fits to radial velocity data, direct imaging, or fits to micro-lensing light curves. The space motion describes the composite motion of a star in the Galaxy relative to the Sun and is derived from the star's distance, proper motions, and mean radial velocity.
It is usually expressed with three space velocity components U, V, W in a right-handed Galactic system, with U pointing towards the Galactic center, V in the direction of rotation, and W towards the north Galactic pole. The space motion describes the composite movement of a star in the Galaxy and is derived from the star's distance, proper motions, and mean radial velocity.
It is usually expressed with three space velocity components U, V, W in a right-handed Galactic system, with U pointing towards the Galactic center, V in the direction of rotation of the disk of the galaxy, and W towards the north Galactic pole. For the calculated space motions, we refer the motion to the Local Standard of Rest i. The high-resolution optical spectra have been donated by the California Planet Search, the N2K project, and the M2K project, while the infrared spectra comes from the publications referenced below.
Spectra are categorized by optical and infrared. The spectral type of a star, brown dwarf, or lower-mass objects is a classification scheme based on spectral features. It is a purely empirical quality that relies only on the measured spectrum; for stars, spectral types are primarily related to the surface temperature.
The allowed spectral types in the Exoplanet Archive are listed below. In order to provide a more complete coverage of the spectral types for our objects, we have included spectral types from the HD catalog. These spectral types while not as accurate as the MK types noted above include nearly all the stars in our database including the bright northern stars. The spectral type of a star is usually accompanied by its luminosity class and additional qualifiers.
The rotational velocity of a star is the rate at which it spins about its axis of rotation. In Astronomy rotational velocity is typically measured from the Doppler broadening of spectral features, which depends also on the inclination of the star's axis relative to the observer's line of sight.
This is commonly referred to as V Sin i. If a planet in orbit around the star passes between the observer and the star, the apparent brightness of the star is reduced for a brief period. The depth of the planetary transit depends upon the radius of the planet and the radius of the star and so can be used to induce the size of the planet. The relative change in flux is then the square of the ratio of the planetary and stellar radii respectively.
Two values for the calculated transit depth for each planet are stored in the Exoplanet Archive: one assuming an Earth radius and one assuming a Jupiter radius. The transit depth is dimensionless. The variability types used in the Exoplanet Archive taken from the Hipparcos catalog. The following codes are used to describe the variability type in the Exoplanet Archive.
These are taken from the Hipparcos catalog description Table 2. Documentation Index Kepler Documentation. Social Media Subscribe to email updates Contact Us.
The Exoplanet Archive stores the following activity indicators: S-Index: The flux ratio of two bandpasses centered on the H The S-Index includes contributions from both the photosphere and the chromosphere of the star. The Exoplanet Archive uses the Mt. Wilson S-Index. References The data are taken from the following sources: Wright et al. Age The age of a star is defined as the time it has spend in the main sequence hydrogen burning phase.
Currently, there are no published stellar age values in the Exoplanet Archive. Age Calculated The age of a star is defined as the time it has spend in the main sequence hydrogen burning phase. Currently, there are no calculated stellar age values in the Exoplanet Archive. Amateur Light Curve These light curves were donated by amateur astronomers, created using their personal equipment, and subsequently curated and processed by Bruce Gary, webmaster of the Amateur Exoplanet Archive AXA.
As more light curves are contributed, these holdings will be updated. References The data are taken from the following sources: Tanner et al. Astrometric Wobble Predicted The presence of a planetary companion will induce a cyclical perturbance on the observed motion of the parent star.
References The data are calculated by the Exoplanet Archive. Coordinate Calculated The Ecliptic and Galactic coordinates displayed on the Overview page are generated by the Exoplanet Archive from Equatorial J coordinates values.
Eccentricity The Observed Eccentricity is the orbital eccentricity. References The Planet Properties page for each individual star with planets includes references for the observed orbit properties. Effective Temperature Calculated The effective temperature T eff is defined as the temperature that a blackbody would have if it emits the same amount of total energy per unit area as the star.
About Us. Earth's equator projected on the celestial sphere. The Equatorial latitude is more commonly known as Declination, which is sometimes abbreviated as Dec. Johnson et al. Bessell Bessel PASP, , The Tycho-2 Catalog. Cousins a.
Cousins b. In the case of man-made satellites, it is often practical to relate the parameters to what we measure from Earth, and not some arbitrary empty point in space. Generally, the point where the satellite is the closest to the central body is called the periapsis, with the length to the central body usually denoted as. The point where the satellite is the farthest away is called the apoapsis, and has the associated length.
The semi-major axis is on the line segment between the periapsis and the apoapsis, and it is half of the distance between them, that is. This is given by the second orbital parameter, the eccentricity. It can be defined from and , and is quite simple to calculate.
For an elliptical orbit it is given as. It does not matter what units the two radii are given in as the eccentricity is unitless. As an example, what is the eccentricity of a circle?
Since a circle has constant radius, we must have that making the eccentricity. An ellipse will have an eccentricity from up to but not including. What kind of orbits we get for even higher eccentricities, we will come back to shortly. Ellipses with different eccentricities are shown in figure 2.
In figure 1 we can see that the radius r is given from the central body to the center of the satellite. The angle is the angle between the semi-major axis and the line between the central body to the satellite and varies in time when the satellite orbits the central body. When the satellite is at perigee the angle is and when it is at apogee the angle is. The angle is most often called the true anomaly and is the third orbital parameter.
It describes the orbital position of the satellite at any specific time. Now we have found the first three parameters describing the orbit and the satellite position in it.
The following expression. We states previously that ellipses has eccentricities from 0 up to 1, and for these cases the radius will be well defined for all angles as can easily be seen. The other two anomalies are called the eccentric anomaly and mean anomaly, and they are used to relate the position of the satellite from the true anomaly to the time since passing of the perigee.
The eccentric anomaly is an actual angle shown in figure 3. The position of the satellite is at the point P with true anomaly. The blue largest circular orbit has a constant radius equal to the semi-major axis of the satellite orbit shown in red in the figure. The relation between the true anomaly and the eccentric anomaly is.
The mean anomaly is not a true angle.
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