Tau Ceti . (τ Cet / τ Ceti) It is a star in the constellation Cetus similar to the sun in mass and spectral type. Just under 12 light-years distant from the solar system, it is a relatively close star. It is a star with a low metallic content, from which its low probability of harboring terrestrial planets in its system is deduced. Astronomical observations have detected more than 10 times the amount of objects and stardust surrounding the star relative to the solar system. The star appears to be stable, with small stellar variations.
Summary
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- 1 Movement
- 2 Rotation
- 3 Metallicity
- 4 Brightness and variability
- 5 Neighborhood
- 6 Source
Movement
The proper motion of a star is the amount of motion through its celestial sphere, determined by comparing its position relative to the farthest background object. Tau Ceti is considered a star of high own movement, since its annual change of position is of two seconds of arc. Movement of more than one degree of arc requires several thousand years. A high own mobility is indicative of its proximity to the sunSince neighboring stars can traverse a celestial angular arc more quickly than distant ones, and are good candidates for parallax studies. In the case of Tau Ceti, the parallax measurement indicates a distance of 11.9 light years, which makes it one of the closest stars to the solar system, and the closest within the spectral type “G” after Alpha Centauri.
Rotation
The period of rotation of Tau Ceti was measured thanks to periodic variations in the H and K absorption lines of ionized Calcium . Such lines are closely associated with surface magnetic activity. therefore, the measurement of the periods of variation considers the time required by the sites of magnetic activity to complete a complete revolution on the star. By this method the turnover has been estimated at 34 days. Due to the Doppler effect , the speed of rotation affects the width of the absorption lines of the spectrum, so by analyzing such lines it is possible to estimate the speed of rotation.
Metallicity
The chemical composition of a star provides important clues about its evolutionary history, including its age. The interstellar medium of dust and gas from which the stars were generated is composed primarily of hydrogen and helium, with traces of heavier elements. As neighboring stars continue to evolve and die, they seed the interstellar medium with increasing proportions of heavy elements. Consequently, younger stars will tend to have a higher proportion of heavy elements than older ones. Astronomers call this portion of the heavy elements metallicity.
Brightness and variability
The luminosity of Tau Ceti is equivalent to only 55% of the solar. A terrestrial planet would have to orbit the star at a distance slightly less than 0.7 astronomical units in order to achieve Earth’s level of solar illumination. This represents less than the average distance between Venus and our sun.
The Tau Ceti chromosphere – the portion of the stellar atmosphere above the light-emitting photosphere – generally shows little or no magnetic activity, indicating that it is a stable star. A nine-year study of temperature, granulometry, and chromosphere did not show significant variations: Calcium ion emissions around the infrared H and K bands showed a possible 11-year cycle, much like the sun. It has also been suggested that it may be in a period of low activity analogous to a Maunder minimum.
Neighborhood
Tau Ceti is a star in the southern hemisphere, in the constellation Cetus (Whale): assuming perfect visual conditions, it is visible over latitude 75 ° N. The constellation is large, located just south of the celestial equator. Other visible stars are the variable Mira and others that despite being in the same direction from the earth, are not physically close to each other: for example the orange giant Beta Ceti, the brightest in the constellation, is approximately 100 years away. sunlight, almost 10 times farther than Tau Ceti. Most of the stars near Tau Ceti are faint and cannot be seen with the naked eye, including YZ Ceti and Luyten 726-8 .
