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Epsilon Tucanae
Epsilon Tucanae (ε Tuc, ε Tucanae) is a solitary star in the southern constellation of Tucana. With an apparent visual magnitude of +4.50, it is faintly visible to the naked eye. Based upon an annual parallax shift of 8.74 mas as seen from Earth, it is located around 373 light years from the Sun. Levenhagen and Leister (2008) classified this star as B8 V, indicating a blue-white hued B-type main sequence star. However, Hiltner, Garrison, and Schild (1969) listed it with a classification of B9 IV, suggesting it may be a more evolved subgiant star. It is a rapidly rotating Be star that is an estimated 78% of the way through its main sequence lifetime. The projected rotational velocity is 300 km/s, which is giving it an oblate shape with an equatorial bulge that is an estimated 36% larger than the polar radius. It has a weak magnetic field with a strength of . It is the last star in the Hipparcos catalogue, HIP 118322, from the Hipparcos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
J2000
In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a celestial body, as they are subject to perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit. The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics (for predicting orbital paths and positions for bodies in motion under the gravitational effects of other bodies) can be used to generate an ephemeris, a table of values giving the positions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
B-type Main Sequence Star
A B-type main-sequence star (B V) is a main-sequence (hydrogen-burning) star of spectral type B and luminosity class V. These stars have from 2 to 16 times the mass of the Sun and surface temperatures between 10,000 and 30,000 K. B-type stars are extremely luminous and blue. Their spectra have neutral helium, which are most prominent at the B2 subclass, and moderate hydrogen lines. Examples include Regulus and Algol A. This class of stars was introduced with the Harvard sequence of stellar spectra and published in the ''Revised Harvard photometry'' catalogue. The definition of type B-type stars was the presence of non-ionized helium lines with the absence of singly ionized helium in the blue-violet portion of the spectrum. All of the spectral classes, including the B type, were subdivided with a numerical suffix that indicated the degree to which they approached the next classification. Thus B2 is 1/5 of the way from type B (or B0) to type A. Later, however, more refined sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
