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  2. Light-year - Wikipedia

    en.wikipedia.org/wiki/Light-year

    10 −3: 2.04 × 10 −3 ly: The most distant space probe, Voyager 1, was about 18 light-hours (130 au,19.4 billion km, 12.1 billion mi) away from the Earth as of October 2014. [29] It will take about 17 500 years to reach one light-year at its current speed of about 17 km/s (38 000 mph, 61 200 km/h) relative to the

  3. Observable universe - Wikipedia

    en.wikipedia.org/wiki/Observable_universe

    Dark matter (26.8%) Dark energy (68.3%) [ 6] The observable universe is a ball-shaped 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 ...

  4. List of Solar System objects by size - Wikipedia

    en.wikipedia.org/wiki/List_of_Solar_System...

    For example, if a TNO is incorrectly assumed to have a mass of 3.59 × 10 20 kg based on a radius of 350 km with a density of 2 g/cm 3 but is later discovered to have a radius of only 175 km with a density of 0.5 g/cm 3, its true mass would be only 1.12 × 10 19 kg. The sizes and masses of many of the moons of Jupiter and Saturn are fairly well ...

  5. Parsec - Wikipedia

    en.wikipedia.org/wiki/Parsec

    The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,265 astronomical units (AU), i.e. 30.9 trillion kilometres (19.2 trillion miles ). [ a] The parsec unit is obtained by the use of parallax and trigonometry, and is ...

  6. Galaxy - Wikipedia

    en.wikipedia.org/wiki/Galaxy

    The Milky Way is an example of a spiral galaxy. It is estimated that there are between 200 billion [7] (2 × 10 11) to 2 trillion [8] galaxies in the observable universe. Most galaxies are 1,000 to 100,000 parsecs in diameter (approximately 3,000 to 300,000 light years) and are separated by distances in the order of millions of parsecs (or ...

  7. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    A light-year is the distance light travels in one Julian year, around 9461 billion kilometres, 5879 billion miles, or 0.3066 parsecs. In round figures, a light year is nearly 10 trillion kilometres or nearly 6 trillion miles. Proxima Centauri, the closest star to Earth after the Sun, is around 4.2 light-years away. [89]

  8. Hercules–Corona Borealis Great Wall - Wikipedia

    en.wikipedia.org/wiki/Hercules–Corona_Borealis...

    15.049 to 17.675 billion light-years (present comoving distance ) [ 4 ] The Hercules–Corona Borealis Great Wall (HCB) [ 1 ] [ 5 ] or simply the Great Wall [ 6 ] is a galaxy filament that is the largest known structure in the observable universe , measuring approximately 10 billion light-years in length (the observable universe is about 93 ...

  9. Extraterrestrial liquid water - Wikipedia

    en.wikipedia.org/wiki/Extraterrestrial_liquid_water

    As of December 2015, the confirmed liquid water in the Solar System outside Earth is 25–50 times the volume of Earth's water (1.3 billion km 3), [10] i.e. about 3.25-6.5 × 10 10 km 3 (32.5 to 65 billion km 3) and 3.25-6.5 × 10 19 tons (32.5 to 65 billion tons) of water.