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From an observation of a transit of Venus in 1032, the Persian astronomer and polymath Ibn Sina concluded that Venus was closer to Earth than the Sun. [186] In 1677, Edmond Halley observed a transit of Mercury across the Sun, leading him to realize that observations of the solar parallax of a planet (more ideally using the transit of Venus ...
Type Escape velocity Mass Volume ()Lowest Highest Lowest Highest Lowest Highest Star: 617.7 km/s Sun [11]332,830 M Earth Sun [26] [27]695,000 km Sun [27]Major planet: 4.3 k m/s Mercury
The subsolar point on a planet is the point at which its Sun is perceived to be directly overhead (at the zenith); [1] that is, where the Sun's rays strike the planet exactly perpendicular to its surface. It can also mean the point closest to the Sun on an astronomical object, even though the Sun might not be visible.
Similarly, when the Sun is at the highest point on the analemma, near its top-left end, (on 15 June) the earliest sunrise of the year will occur. Likewise, at sunset, the earliest sunset will occur when the Sun is at its lowest point on the analemma when it is close to the western horizon, and the latest sunset when it is at the highest point.
The lowest point on land not covered by liquid water is the canyon under Denman Glacier in Antarctica, with the bedrock being 3,500 m (11,500 ft) below sea level. [32] [33] The shore of the Dead Sea in Israel. The lowest point on dry land is the shore of the Dead Sea, shared by Israel and Jordan, 432.65 m (1,419 ft) below sea level. As the Dead ...
The term can also be used to represent the lowest point that a celestial object reaches along its apparent daily path around a given point of observation (i.e. the object's lower culmination). This can be used to describe the position of the Sun, but it is only technically accurate for one latitude at a time and only possible at the low latitudes.
The Sun reaches the observer's zenith when it is 90° above the horizon, and this only happens between the Tropic of Cancer and the Tropic of Capricorn. In Islamic astronomy , the passing of the Sun over the zenith of Mecca becomes the basis of the qibla observation by shadows twice a year on 27/28 May and 15/16 July.
The Stonyhurst heliographic coordinate system, developed at Stonyhurst College in the 1800s, has its origin (where longitude and latitude are both 0°) at the point where the solar equator intersects the central solar meridian as seen from Earth. Longitude in this system is therefore fixed for observers on Earth.