M dwarfs dominate the stellar population, accounting for three of every four stars, the nearest of which is Proxima Centauri, the closest destination beyond our Solar System. These cool stars span large ranges in luminosities (one ten-thousandth to 6% L⊙) and temperatures (2,100–3,900 K) and have spectra dominated by absorption bands of titanium oxide (TiO) and, for the latest spectral types, vanadium oxide (VO). They have masses that span 0.075 to 0.61 M⊙, a factor of eight, which is comparable with a spread in masses for dwarf types mid-B through K. Unlike these more massive stars, in the age of the Universe no M dwarfs have evolved in any significant way. M dwarf systems are multiple roughly one-quarter of the time, with the closest binaries found in orbits that have been circularized via tides for orbital periods of about one week. Unlike any other type of main sequence star, there is a gap in the distribution of M dwarfs near masses of 0.35 M⊙ that pinpoints the separation of partially and fully convective stars, yet both types of M dwarfs are often active, showing both Hα in emission and flares. Many planets are found orbiting M dwarfs, and most of them are terrestrial or neptunian in size, rather than jovian, yet much more work remains to be done to characterize the exoplanet population. Overall, the Solar Neighborhood is dominated by M dwarfs that are likely orbited by many small, as yet unseen, planets—some of which may harbor life very near to that in our Solar System. ▪ M dwarfs account for three of every four stars. ▪ M dwarf counts increase all the way to the end of the main sequence. ▪ M dwarfs are partially radiative at high masses and fully convective at low masses.

中文翻译：

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M小矮人的性格


M矮星在恒星总数中占主导地位，占恒星总数的四分之三，其中最近的是比邻星，它是太阳系之外最近的目的地。这些冷恒星的光度（万分之一到 6% L⊙）和温度（2,100–3,900 K）范围很大，并且其光谱以氧化钛 (TiO) 的吸收带为主，对于最新的光谱类型，氧化钒的吸收带占主导地位。 （画外音）。它们的质量跨度为 0.075 到 0.61 M⊙，是 8 倍，与 B 至 K 中矮类型的质量分布相当。与这些质量更大的恒星不同，在宇宙时代，没有 M 型矮星演化出来。以任何重要的方式。 M型矮星系统大约四分之一的时间是多重的，最近的双星系统被发现在轨道上，这些轨道通过潮汐而形成圆形，轨道周期约为一周。与任何其他类型的主序星不同，质量为 0.35 M⊙ 附近的 M 矮星分布中存在一个间隙，精确定位了部分对流恒星和完全对流恒星的分离，然而两种类型的 M 矮星通常都很活跃，显示出 Hα 都在排放和耀斑。人们发现了许多围绕 M 矮星运行的行星，其中大多数的大小是类地或海王星的，而不是木星的，但仍有大量工作要做来描述系外行星种群的特征。总体而言，太阳邻域主要由 M 型矮星主导，它们的轨道上可能有许多尚未被发现的小型行星，其中一些行星可能拥有与我们太阳系非常接近的生命。 ▪ M 矮星占每四颗恒星中的三颗。 ▪ M 矮星计数一直增加到主序列末尾。 ▪ M 矮星在高质量时部分辐射，在低质量时完全对流。