Deep space exploration (or deep-space exploration) is the branch of astronomy, astronautics and space technology that is involved with exploring the distant regions of outer space. However, there is little consensus on the meaning of "distant" regions. In some contexts, it is used to refer to interstellar space. The International Telecommunication Union defines "deep space" to start at a distance of 2 million km (approximately 0.01 AU) from the Earth's surface. NASA's Deep Space Network has variously used criteria of 16,000 to 32,000 km from Earth. Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

At present the farthest space probe humankind has constructed and launched from Earth is Voyager 1, which was announced on December 5, 2011, to have reached the outer edge of the Solar System, and entered interstellar space on August 25, 2012. Deep space exploration further than this vessel's capacity is not yet possible due to limitations in the propulsion technology currently available.

Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion. The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.

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