Red Dwarf

Introduction: 

        A red dwarf is the smallest and coolest kind of star on the main sequence. Red dwarfs are by far the most common type of star in the Milky Way,  at least in the neighborhood of the Sun, but because of their low luminosity, individual red dwarfs cannot be easily observed. Proxima Centauri is the nearest star of our Sun. Which is a red dwarf Star.  The coolest red dwarfs near the Sun have a surface temperature of ~2,000 K and the smallest have radii of ~9% that of the Sun, with masses about ~7.5% that of the Sun. Red Dwarf stars are much cooler. So the habitable planets of this star is much closer to our Sun. From Earth, not even a single star that fits the strict definition of a red dwarf can be seen with the naked eye. Red dwarfs are expected to live much longer because they do not use their fuel quickly. A new study using NASA’s Chandra X-ray Observatory and Hubble Space Telescope examined the red dwarf called Barnard’s Star, which is about 10 billion years old, more than twice the current age of the Sun. Young red dwarfs, with ages less than a few billion years, are known as strong sources of high-energy radiation, including blasts of ultraviolet light and X-rays. However, scientists know less about how much damaging radiation red dwarfs give off later in their lifetimes.

List of some red dwarf:

 ● Lacaille 8760 (First discovered)

 ● Gliese 876 (First discovered with planet(s)

 ● Proxima Centauri (Named for being the closest neighboring star to Earth's Sun)

 ● Barnard's Star

● Lacaille 8760 : Lacaille 8760 (AX Microscopii) is a red dwarf star in the constellation Microscopium. It is one of the nearest stars to the Sun at about 12.9 light-years distance. Mass of Lacaille 8760 is 0.60 M_☉ (solar mass). Radius of Lacaille 8760 is 0.51  R_☉ (Solar radius). Lacaille 8760 orbits around the galaxy with a relatively high ellipticity of 0.23. Its closest approach to the Sun occurred about 20,000 years ago when it came within 12 light-years (3.7 parsecs). Due to its low mass (60% of the Sun), it has an expected lifespan of about 75 billion (7.5 × 1010) years, seven times longer than the Sun's.

● Gliese 876 : Gliese 876 is a red dwarf approximately 15 light-years away from Earth in the constellation of Aquarius. It is one of the closest known stars to the Sun. Mass of Gliese 876 is 0.37 M_☉ (solar mass). Radius of Gliese 876 is 0.3761±0.0059  R_☉ (Solar radius).

    ➤The Gliese 876 planetary system

        ⏩ Gliese 876 d : Gliese 876d, discovered in 2005, is the innermost known planet. With an estimated minimum mass only 5.88 times that of the Earth, it is possible that it is a dense terrestrial planet.

        ⏩ Gliese 876 c : Gliese 876 c, discovered in 2001, is a giant planet at 0.62 Jupiter-mass planet. It takes 30.340 days to orbit it's host star.   

       ⏩ Gliese 876 b : Gliese 876 b, discovered in 1998 is around twice the mass of Jupiter and revolves around its star in an orbit taking approximately. It takes 61 days to orbit it's host star. it is at a distance of only 0.208 AU from it's host star. which less than the distance from the Sun to Mercury.

       ⏩ Gliese 876 e : Gliese 876 e, discovered in 2010, has a mass similar to that of the planet Uranus and its orbit takes 124 days to complete.

● Proxima Centauri : Proxima Centauri is a small, low-mass red dwarf star located 4.2465 light-years away from the Sun in the southern constellation of Centaurus. It was discovered in 1915 by Robert Innes and is the nearest-known star to the Sun. Proxima Centauri is a member of the Alpha Centauri star system, being identified as component Alpha Centauri C. Mass of Proxima Centauri is 0.1221±0.0022 M_☉ (solar mass). Radius of Proxima Centauri is 0.1542±0.0045  R_☉ (Solar radius)

● Barnard's Star : Barnard's Star is a red dwarf about six light-years from Earth in the constellation of Ophiuchus. It is the fourth-nearest-known individual star to the Sun after the three components of the Alpha Centauri system. Mass of Barnard's Star is 0.144 M_☉ (solar mass). Radius of Barnard's Star is 0.196 ± 0.008 R_☉ (Solar radius)

Habitability of red dwarf systems

        According to scientist that planets in red dwarf systems are extremely unlikely to be habitable. planets in red dwarf systems has long lifespans but there are several factors which may make life difficult on planets around a red dwarf. First, planets in the habitable zone of a red dwarf would be so close to the parent star that they would likely be tidally locked. This would mean that one side would be in perpetual daylight and the other in eternal night. This could create enormous temperature variations from one side of the planet to the other. Such conditions would appear to make it difficult for forms of life similar to those on Earth to evolve.