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April 25, A schematic of the binary stars in Spica, showing four stages of an orbital period. Massive binary stars often have a "mass discrepancy problem," meaning that the masses derived from orbital and evolutionary methods disagree. Credit: A. Tkachenko et al. Provided by Harvard-Smithsonian Center for Astrophysics.
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. First observation of an inhomogeneous electron charge distribution on an atom 1 hour ago. Reading Paper on Earth Occultation Technique 15 hours ago.
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These so-called Doppler shifts are what astronomers picked up in , suggesting that Spica A had a companion. Visually, though, the pair merges into a single point. Why is this? Distance is partially responsible, as Spica is more than light-years from us. But the other reason is that the two stars are extremely close together, separated by a tight 11 million miles, or 0.
The stars revolve rapidly around each other with an orbital period of only four days. Even though the two stars are separated by a distance greater than that between Earth and the Moon, they are also quite massive so they exhibit a strong gravitational pull on each other.
From Earth's point of view, the pair pass over each other just slightly in a grazing eclipse , which adds another source of variability.
The association with spring is interesting as well, as Virgo first becomes visible in the evenings right around the spring equinox. In the s B. The star is a fast spinner, with a projected rotational velocity of Its estimated age is It is one of the nearest stars to the solar system that is massive enough to be a Type II supernova candidate. The primary component is classified as a Beta Cephei variable, a star showing small, rapid fluctuations in brightness as a result of pulsations of its outer layers.
It varies in brightness with a period of 0. Alpha Virginis B is cooler, smaller and less massive, with a temperature of 20, K, a radius 3. It is a main sequence star of the spectral type B2V. It has a luminosity 2, times that of the Sun. Its projected rotational velocity is This is known as the Struve-Sahade effect.
Both stars rotate more rapidly than their orbital period, and the lack of synchronization, coupled with the highly elliptical orbit, may indicate that the star system is still young.
A study published in revealed that Spica is a polarimetric variable. The two stars were the first to have their geometric albedo reflectivity measured. A study published in yielded geometric albedos of 3. Even though the stars reflect very little of the incident light, the reflected light is highly polarized. Spica is one of the 58 bright stars selected for navigation.
Navigational stars play a special role in the field of celestial navigation because they are some of the brightest and most identifiable stars in the sky. Spica is the only navigational star in the constellation Virgo. Spica lies only 2. The last occultation by a planet occurred on November 10, , when the planet Venus passed in front of the star.
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