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The astrolabe, an instrument that has its origins in Hellenistic astronomy, is a predecessor of the modern planisphere. The term planisphere contrasts with armillary sphere , where the celestial sphere is represented by a three-dimensional framework of rings.
North African, 9th century CE, planispheric astrolabe. Khalili Collection. A modern astrolabe made in 2013, in Tabriz, Iran.. An astrolabe (Ancient Greek: ἀστρολάβος astrolábos, ' star-taker '; Arabic: ٱلأَسْطُرلاب al-Asṭurlāb; Persian: ستارهیاب Setāreyāb) is an astronomical instrument dating to ancient times.
Jost Bürgi and Antonius Eisenhoit: Armillary sphere with astronomical clock, made in 1585 in Kassel, now at Nordiska Museet in Stockholm. An armillary sphere (variations are known as spherical astrolabe, armilla, or armil) is a model of objects in the sky (on the celestial sphere), consisting of a spherical framework of rings, centered on Earth or the Sun, that represent lines of celestial ...
Kepler-1638b was thought to be a possibly habitable planet with a radius smaller than 2 R 🜨 after the validation. However based on the later measurement of host star parallax by Gaia, the radius of the planet was revised upward to 3.226 +0.201 −0.315 R 🜨, resulting in it being a ice giant like Neptune with poor prospect for habitability ...
In Greek antiquity the ideas of celestial spheres and rings first appeared in the cosmology of Anaximander in the early 6th century BC. [7] In his cosmology both the Sun and Moon are circular open vents in tubular rings of fire enclosed in tubes of condensed air; these rings constitute the rims of rotating chariot-like wheels pivoting on the Earth at their centre.
Pluto's reign. For decades, students learned the phrase "My Very Educated Mother Just Served Us Nine Pizzas" to remember the order of the planets in the solar system: Mercury, Venus, Earth, Mars ...
Composite image showing the round dwarf planet Ceres; the slightly smaller, mostly round Vesta; and the much smaller, much lumpier Eros. The IAU definitions of planet and dwarf planet require that a Sun-orbiting astronomical body has undergone the rounding process to reach a roughly spherical shape, an achievement known as hydrostatic equilibrium.
The roots of the equatorium lie in the astrolabe.The history of the astrolabe dates back to roughly 220 BC in the works of Hipparchus. [6] The difference between the two instruments is that the astrolabe measures the time and position of the sun and stars at a specific location in time. [7]