Cepheid | has period 1 to 50 days |  |
has prototype delta Cephei |  |
has spectral type F star, G star and K star |  |
has definition A yellow supergiant that pulsates, alternately brightening and dimming. Cepheids allow astronomers to measure distances, because the longer a Cepheid's period of variation, the greater the Cepheid's mean intrinsic brightness. To determine a Cepheid's distance, all an astronomer has to do is measure the Cepheid's period; comparing the star's mean intrinsic brightness with the star's mean apparent brightness then yields the distance. Cepheids are so bright that we can see them in other galaxies, allowing us to establish distances to entire galaxies beyond the Milky Way. |  |
has definition One of a group of very luminous supergiant pulsating stars. The luminosities of a Cepheid is proportional to its period, but a different P-L relation applies to each type. No Cepheid is near enough for an accurate trigonometric parallax (Polaris is the nearest). Cepheids are useful distance indicators to about 3 Mpc. |  |
has definition A type of variable star whose period of variation is tightly related to its intrinsic luminosity. |  |
has definition A class of stars named after Delta Cephei which vary in brightness over a regular period of time (typically a few days). The period of change is directly related to the true, average brightness or luminosity of the star. Once the period is known the true brightness can be calculated and the distance estimated by observing the "apparent" brightness of the object as seen from Earth. |  |
has definition Strictly periodic variables with periods 1-50 days, of spectral types F, G and K. |  |
is a kind of periodic variable |  |
variable | has name designated with - R, S, T, U, V, W, X, Y, or Z and the genitive of the latin constellation name
- RR, RS, RT, RU, RV, RW, RX, RY, or RZ and the genitive of the latin constellation name when the single letter designations are exhausted
- AA...AZ, BB...BZ, etc. (omitting J), which ends with QQ...QZ and the genitive of the latin constellation namewhen the RR...RZ designations are exhausted
- V 335, V 336, etc., when the double letter designations are exhausted
|  |
has observational problem some difficulty in distinguishing between various kinds |  |
has observable variation time scale within a period of decades |  |
has light curve |  |
has optical brightness variation 0.2 magnitudes or greater |  |
has amplitude |  |
star | has star surface temperature |  |
has V magnitude |  |
has B magnitude |  |
has U magnitude |  |
has position on celestial sphere from the point of view of Earth |  |
has parallax from the point of view of Earth's orbit |  |
has proper motion |  |
has radiation at surface which is diffused out from the hotter core |  |
has energy source gravitational contraction and or fusion |  |
has energy production which takes place primarily within the core |  |
has surface density which depends on luminosity class |  |
has surface temperature greater than 1000 Kelvin |  |
has apparent magnitude |  |
has absolute magnitude |  |
has age |  |
has catalog star catalog |  |
has material hydrogen, helium |  |
has velocity determined from proper motion and radial velocity |  |
has mass greater than 0.08 the sun's mass |  |
celestial body | has spectra |  |
physical object | has location or center of gravity |  |
has angular momentum |  |
has momentum |  |
has temperature |  |
has volume |  |
has extent |  |