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Human presence in outer space began with the first launches of artificial object in the mid 20th century, and has increased to the point where Earth is orbited by a vast number of artificial objects and the far reaches of the Solar System have been visited and explored by a range of space probes.
An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists within the observable universe. [1] In astronomy , the terms object and body are often used interchangeably.
The physical universe is defined as all of space and time [a] (collectively referred to as spacetime) and their contents. [10] Such contents comprise all of energy in its various forms, including electromagnetic radiation and matter, and therefore planets, moons, stars, galaxies, and the contents of intergalactic space.
As the resolving power of telescopes increased, numerous objects that were thought to be a single object were found to be optical star systems that were too closely spaced in the sky to be discriminated by the human eye. This led to a third iteration, where numeric superscripts were added to distinguish those previously unresolved stars.
The Cherenkov telescopes do not detect the gamma rays directly but instead detect the flashes of visible light produced when gamma rays are absorbed by the Earth's atmosphere. [59] Most gamma-ray emitting sources are actually gamma-ray bursts, objects which only produce gamma radiation for a few milliseconds to thousands of seconds before ...
The observable universe is a spherical region of the universe consisting of all matter that can be observed from Earth or its space-based telescopes and exploratory probes at the present time; the electromagnetic radiation from these objects has had time to reach the Solar System and Earth since the beginning of the cosmological expansion.
Although people in the family are related to one another, the relations do not exist independently of the people. [13] Leibniz argued that space could not exist independently of objects in the world because that implies a difference between two universes exactly alike except for the location of the material world in each universe.
List of NGC objects. List of NGC objects (1–1000) List of NGC objects (1001–2000) List of NGC objects (2001–3000) List of NGC objects (3001–4000) List of NGC objects (4001–5000) List of NGC objects (5001–6000) List of NGC objects (6001–7000) List of NGC objects (7001–7840) List of IC objects; List of Messier objects; List of ...