Hemellichamen

Hemellichamen are natural objects that exist in space beyond Earth's atmosphere. The term covers a broad range of phenomena, from bodies that orbit the Sun to distant objects in interstellar space. They can be observed with the naked eye under favorable conditions, or with telescopes, spacecraft instruments, and other remote sensing methods.

Within the solar system, major categories include planets (including dwarf planets) and natural satellites such as moons. Smaller bodies include asteroids, comets, meteoroids, and interplanetary dust. Beyond the solar system lie other stars, their planetary systems, star clusters, nebulae, galaxies, and other cosmic structures.

Key properties used to describe hemellichamen are their orbits, distances, sizes, masses, compositions, and brightness. Distances are expressed in astronomical units or light-years; sizes in kilometers or astronomical units; brightness in apparent and absolute magnitudes. Observations rely on spectroscopy, photometry, astrometry, and, for nearby objects, radar ranging and spacecraft measurements.

Studying hemellichamen provides insight into the formation and evolution of planetary systems, stars, and galaxies. The field encompasses planetary science, stellar astrophysics, and cosmology, and it informs space missions, telescopic surveys, and theoretical modeling.