Closest star
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Closest Star to the Solar System
Proxima Centauri: The Nearest Star
Discovery and Parallax Measurements
Proxima Centauri, a red dwarf star, was identified as the closest star to the solar system by Innés, who measured its parallax to be 0.88 arcseconds. This measurement suggested that Proxima Centauri was closer than Alpha Centauri, which has a parallax of 0.76 arcseconds. However, subsequent measurements have varied, with Schlesinger's Catalogue providing a weighted mean parallax of 0.802 arcseconds, and more recent observations from the Yale Observatory and the Royal Observatory at the Cape of Good Hope reporting parallaxes of 0.783 and 0.758 arcseconds, respectively . Despite these variations, Proxima Centauri remains the closest known star to the solar system.
Stellar Characteristics and Activity
Proxima Centauri is a small red dwarf with an effective temperature of approximately 3,050 Kelvin, a luminosity of 0.15% that of the Sun, a radius of 14% of the Sun's radius, and a mass of about 12% of the Sun's mass. It is considered a moderately active star with a rotation period of about 83 days. Proxima Centauri also hosts an exoplanet, Proxima b, which has a minimum mass of about 1.3 Earth masses and orbits the star every 11.2 days. This exoplanet lies within the habitable zone, where conditions might allow for liquid water on its surface 26.
Stellar Flares and Habitability
One significant challenge for the habitability of planets around red dwarfs like Proxima Centauri is the frequent stellar flares. These flares can strip away a planet's atmosphere, making it difficult for life to sustain. Proxima Centauri is known to exhibit such stellar activity, which could impact the potential habitability of Proxima b .
Other Close Stellar Encounters
Historical Close Encounters
In addition to Proxima Centauri, other stars have had close encounters with the solar system. For instance, the K7 dwarf Gl 710 is predicted to pass within 0.0636 parsecs of the Sun in about 1.3 million years. Another close encounter involved the G3 dwarf HD 7977, which approached within less than 0.05 parsecs of the Sun approximately 2.8 million years ago .
Scholz’s Star and Other Past Flybys
Scholz’s star (WISE J072003.20-084651.2) is another notable close encounter, having passed within 0.330 parsecs of the Sun around 79,900 years ago. More recently, data from Gaia DR3 has identified UCAC4 237-008148 as having approached within 0.259 parsecs of the Sun about 1.158 million years ago .
Conclusion
Proxima Centauri remains the closest known star to the solar system, despite variations in parallax measurements. Its characteristics and the presence of an exoplanet in the habitable zone make it a significant object of study. However, the frequent stellar flares pose challenges for the habitability of its planets. Additionally, historical data reveals that other stars have had close encounters with the solar system, providing valuable insights into the dynamic nature of our galactic neighborhood.
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