Search results
Results from the WOW.Com Content Network
A multiple star system consists of two or more stars that appear from Earth to be close to one another in the sky. [dubious – discuss] This may result from the stars actually being physically close and gravitationally bound to each other, in which case it is a physical multiple star, or this closeness may be merely apparent, in which case it is an optical multiple star [a] Physical multiple ...
Hertzsprung noted that stars described with narrow lines tended to have smaller proper motions than the others of the same spectral classification. He took this as an indication of greater luminosity for the narrow-line stars, and computed secular parallaxes for several groups of these, allowing him to estimate their absolute magnitude. [2]
The average absolute magnitude of an RR Lyrae star is about +0.75, only 40 or 50 times brighter than the Sun. [8] Their period is shorter, typically less than one day, sometimes ranging down to seven hours. Some RRab stars, including RR Lyrae itself, exhibit the Blazhko effect in which there is a conspicuous phase and amplitude modulation. [9]
Solar-type stars show highly correlated behavior between their rotation rates and their chromospheric activity (e.g. Calcium H & K line emission) and coronal activity (e.g. X-ray emission) [4] Because solar-type stars spin down during their main-sequence lifetimes due to magnetic braking, these correlations allow rough ages to be derived.
The instability strip intersects the main sequence, (the prominent diagonal band that runs from the upper left to the lower right) in the region of A and F stars (1–2 solar mass (M ☉)) and extends to G and early K bright supergiants (early M if RV Tauri stars at minimum are included). Above the main sequence, the vast majority of stars in ...
RR Lyrae is a variable star in the Lyra constellation, figuring in its west near to Cygnus. [10] As the brightest star in its class, [11] it became the eponym for the RR Lyrae variable class of stars [3] and it has been extensively studied by astronomers. [7] RR Lyrae variables serve as important standard candles that are used to measure ...
Baade observed that bluer stars were strongly associated with the spiral arms, and yellow stars dominated near the central galactic bulge and within globular star clusters. [2] Two main divisions were defined as Population I star and population II , with another newer, hypothetical division called population III added in 1978.
In the most massive stars, the convection zone may reach all the way from the core to the surface. [2] In main sequence stars of less than about 1.3 solar masses, the outer envelope of the star contains a region where partial ionization of hydrogen and helium raises the heat capacity.