Stars and Exoplanets

<p>A <strong>star</strong> is an <a title= "Astronomical object" href= "https://en.wikipedia.org/wiki/Astronomical_object">astronomical object</a> comprising a luminous <a title="Spheroid" href="https://en.wikipedia.org/wiki/Spheroid">spheroid</a> of <a title="Plasma (physics)" href= "https://en.wikipedia.org/wiki/Plasma_(physics)">plasma</a> held together by <a title="Self-gravitation" href= "https://en.wikipedia.org/wiki/Self-gravitation">self-gravity</a>. The <a title="List of nearest stars and brown dwarfs" href= "https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs">nearest star</a> to <a title="Earth" href= "https://en.wikipedia.org/wiki/Earth">Earth</a> is the <a title="Sun" href= "https://en.wikipedia.org/wiki/Sun">Sun</a>. Many other stars are visible to the naked eye at <a title="Night sky" href= "https://en.wikipedia.org/wiki/Night_sky">night</a>, but their immense distances from Earth make them appear as <a title= "Fixed stars" href= "https://en.wikipedia.org/wiki/Fixed_stars">fixed</a> points of light. The most prominent stars have been categorised into <a title="Constellation" href= "https://en.wikipedia.org/wiki/Constellation">constellations</a> and <a title="Asterism (astronomy)" href= "https://en.wikipedia.org/wiki/Asterism_(astronomy)">asterisms</a>, and many of the brightest stars have <a class="mw-redirect" title="Proper name" href= "https://en.wikipedia.org/wiki/Proper_name">proper names</a>. <a title="Astronomer" href= "https://en.wikipedia.org/wiki/Astronomer">Astronomers</a> have assembled <a title="Star catalogue" href= "https://en.wikipedia.org/wiki/Star_catalogue">star catalogues</a> that identify the known stars and provide standardized <a class="mw-redirect" title= "Stellar designation" href= "https://en.wikipedia.org/wiki/Stellar_designation">stellar designations</a>. The <a title="Observable universe" href= "https://en.wikipedia.org/wiki/Observable_universe">observable universe</a> contains an estimated <span class= "nowrap">10²²</span> to <span class= "no