Tycho Brahe (Martian crater) Tycho Brahe (Martian crater) Tycho Brahe is a nearly ovular crater on Mars named after the Danish astronomer Tycho Brahe (1546–1601). It is located in the Cerberus hemisphere around 49.8° south and 213.9° west, in an area which is south of the Martz crater and east of the Hellas Basin. It measures approximately 105 kilometers in diameter from east to west. The name was adopted by IAU's Working Group for Planetary System Nomenclature in 1973. The crater is crossed by Eridania Scopulus, an escarpment. Other nearby named craters are Huggins to the east, far south is Vinogradsky and northwest is
Planetary nebula about 20% of planetary nebulae are spherically symmetric (for example, see Abell 39). A wide variety of shapes exist with some very complex forms seen. Planetary nebulae are classified by different authors into: stellar, disk, ring, irregular, helical, bipolar, quadrupolar, and other types, although the majority of them belong to just three types: spherical, elliptical and bipolar. Bipolar nebulae are concentrated in the galactic plane, likely produced by relatively young massive progenitor stars; and bipolars in the galactic bulge appear to prefer orienting their orbital axes parallel to the galactic plane. On the other hand, spherical nebulae are likely produced