Beasts of the Stellar Zoo [Slide Show]
From yellow dwarfs to blue supergiants, stars continue to challenge astronomers' understanding of the universe
![Beasts of the Stellar Zoo [Slide Show]](https://www.scientificamerican.com/sciam/cache/file/D2804DED-2641-4268-A68ABA2004679B8D.jpg?w=590&h=393)
Beasts of the Stellar Zoo [Slide Show]
- FIRST BROWN DWARF: Gliese 229 B was the first known brown dwarf, a failed star that looks roughly like a scaled-up version of Jupiter. It is about the same size as the giant planet, but 20 to 50 times as massive. With a low temperature (for a star) of about 1,000 kelvins, it is classified as a type-T star, falling off the right side of most published Hertzsprung–Russell diagrams. Left photo: T. Nakajima (Caltech), S. Durrance (JHU); right photo: S. Kulkarni (Caltech), D.Golimowski (JHU) and NASA
- EARTH-SIZE DWARF: The existence of this white dwarf star, a binary companion of the bright star Sirius, was first inferred in 1844; Sirius B was directly observed in 1862. It is about as massive as the sun, but about the same size as Earth, giving it a density of about a ton per cubic centimeter. NASA, H. E. Bond and E. Nelan (Space Telescope Science Institute, Baltimore, Md.); M. Barstow and M. Burleigh (University of Leicester, U.K.); and J. B. Holberg (University of Arizona)
- CAT'S EYE NEBULA: This dramatic planetary nebula is created by gas ejected from a red giant star in its death throes. The red giant's hot core, seen at the center of this image, causes the gas to glow. As the core cools and fades, it becomes a white dwarf star. X-ray: NASA/CXC/SAO; Optical: NASA/STScI
- FRENETIC FORMATION: This nebula is remarkable for its frenetic star formation and huge variety of stars. To the upper right of center is a blue supergiant; near the center are massive, hot O-type stars; embryonic stars lie to the lower left of the central cluster and in the dark clouds at the upper right. Wolfgang Brandner (JPL/IPAC), Eva K. Grebel (Univ. Washington), You-Hua Chu (Univ. Illinois Urbana–Champaign), and NASA
- HYPERGIANTS OF TARANTULA: Some of the most massive stars ever observed are found in the Tarantula Nebula, located in one of the satellite galaxies, known as the Large Magellanic Cloud, that orbits our Milky Way. One cluster of stars, designated R136, has a star 265 times as massive as the sun and nine million times as luminous. In the same general area astronomers recently found another stellar heavyweight, VFTS 682. Strangely, it does not appear to be part of a cluster. Ultraviolet light emitted by all these stars lights up—and burns off—surrounding clouds of gas and dust. ESO/M.-R. Cioni/VISTA Magellanic Cloud survey. Acknowledgment: Cambridge Astronomical Survey Unit
- BIG BETELGEUSE: Betelgeuse, a red supergiant, is a high-mass star that has already consumed the hydrogen in its core and has bloated to enormous size. In fact, it is as big as the solar system out to the asteroid belt—making it one of the few stars that astronomers see as a disk rather than a mere point. Andrea Dupree (Harvard-Smithsonian CfA), Ronald Gilliland (STScI), NASA and ESA
- STABLE SUN: Our sun, like most others, is classified as a main-sequence star. Powered by the fusion of hydrogen nuclei at its core, it is generally stable—but hardly uneventful. This ultraviolet image from the Solar Dynamics Observatory satellite shows a solar flare (whitish area, upper left) in August 2010. NASA/SDO/AIA
