A new study suggests that Earth's gravity stretched the moon into its odd shape early in its lifetime. During eclipses, the moon, Earth and sun are in a straight line, or nearly so. A lunar eclipse takes place when Earth gets directly or almost directly between the sun and the moon, and Earth's shadow falls on the moon. A lunar eclipse can occur only during a full moon. A solar eclipse occurs when the moon gets directly or nearly directly between the sun and Earth, and the moon's shadow falls on us.
A solar eclipse can occur only during a new moon. Solar eclipses are rare in a given location because the shadow of the moon is so small on the Earth's surface. The last total solar eclipse in the United States happened in Aug. The Earth's axis of rotation is tilted in relation to the ecliptic plane, an imaginary surface through Earth's orbit around the sun. This means the Northern and Southern hemispheres will sometimes point toward or away from the sun depending on the time of year, varying the amount of light they receive and causing the seasons.
The tilt of Earth's axis is about As such, the moon virtually has no seasons. This means that some areas are always lit by sunlight, and other places are perpetually draped in shadow.
Some ancient peoples believed the moon was a bowl of fire, while others thought it was a mirror that reflected Earth's lands and seas, but ancient Greek philosophers knew the moon was a sphere orbiting the Earth whose moonlight reflected sunlight. The Greeks also believed the dark areas of the moon were seas while the bright regions were land, which influenced the current names for those places — "maria" and "terrae," which is Latin for seas and land, respectively.
The pioneering astronomer Galileo Galilei was the first to use a telescope to make scientific observations of the moon, describing in a rough, mountainous surface that was quite different from the popular beliefs of his day that the moon was smooth. In , the Soviet Union sent the first spacecraft to impact the moon's surface and returned the first photographs of its far side. This spurred a series of uncrewed missions by both the Soviet Union and the United States to observe the moon's surface.
Many of these first probes were failures or only partially successful. However, over time, these early probes returned information about the moon's surface and geological history.
Luna 2 was the first spacecraft to impact the moon in The first soft landing was achieved in , by Luna 9. The United States sent astronauts to the moon's orbit and surface in the s and s. The first mission to the moon was in , when the Apollo 8 astronauts orbited it. In , Apollo 11 landed the first astronauts on the moon , undoubtedly the most famous of NASA's achievements, followed by five more successful missions and one, Apollo 13, that didn't make to the moon.
Their efforts returned lbs. It remains the only extraterrestrial body that humanity has ever visited. Scientists continue to study the rocks, and have made new discoveries as technology improved. For example, in , water was found in samples from Apollo 15, 16 and 17 — an interesting find given that previous analyses showed these rocks were quite dry. While crewed lunar missions concluded in , robotic exploration continued. The Soviet Union remained active in robotic lunar exploration through the s and s, even as the Apollo astronauts landed there.
The first lunar sample return mission took place with Luna 16 in September , after multiple failed attempts with other missions. The Soviets also deployed the first robotic lunar rover, called Lunokhod 1, just two months later. Original Greek name:. Hesperos "evening one" , Phosphoros "light-bearing one" or Eosphoros "bringer of the dawn". Greek goddess: Aphrodite.
Venus is by far the easiest planet to see with the naked eye. It is the brightest planet in the night sky; when visible, it outshines all the other planets - and indeed all the other stars in the night sky - at which time only the Sun and the Moon are brighter.
When seen through a telescope , Venus shows phases much like the Moon to understand why the phases of Venus appear as they do when seen from Earth orbit, refer to the ' Inferior Planets ' section of the Planet Movements page. Venus' thin crescent phase can be discerned in good quality binoculars when it is in the nearer part of its orbit to the Earth i. However, Venus' brilliance produces considerable glare when seen against a dark sky, so when using optical aid, it is best observed in bright twilight. When shining at its greatest brilliancy, Venus can cast faint shadows at night, and it can even be glimpsed in daylight given a clear, haze-free sky and provided that the planet is well clear of the Sun.
The best way to see Venus in daylight is when it is a 'Morning Star', when it can be continually observed through to sunrise and beyond. Its brilliance is largely due to the high reflectivity albedo of its clouds, which perpetually obscure the view of the planet's extremely hot surface. Ephemeris Its greatest brilliance occurs about 5 weeks after greatest Eastern elongation evening apparition and about 5 weeks before greatest Western elongation morning apparition.
In the following list, greatest elongation details are given in brackets in the format "Solar elongation, Constellation". Star map showing the path of Venus through the zodiac constellations during the first part of its evening apparition between October and January History of Telescopic Observation. The phases of Venus were first observed telescopically by Italian astronomer, philosopher and physicist Galileo Galilei in , using one of the world's first telescopes the first telescope is believed to have been made by Dutch spectacle maker Hans Lipperhey around In Galileo's time, the 'Ptolemaic' system - which put the Earth at the centre of the Solar System - was the widely held view.
Iove Jove. King of the Gods. Apparent Magnitude:. Phaethon "glittering one". Greek god: Zeus.
Jupit e r appears bright white and is a very obvious sight in the night sky. Viewed from the Earth, Jupiter is seen to move through about one zodiac constellation ca.
This concept has little relevance for either dry or aquaplanets, but might become relevant on a planet with both land area and oceans. Next we turn to simulations of convection and magnetism in stellar interiors, highlighting both some peculiarities of field generation in different types of stars and some unifying physical processes that likely influence dynamo action in general. Its equilibrium temperature is within the range where water could be liquid on its surface. See Sects. Such a statistical theory could be combined with direct numerical simulations of planet trajectories in the context of planet formation, which is likely to be a chaotic process. These planets are located between 0.
The four moons are brighter than the typical naked eye limiting magnitude ca. Small telescopes will show Jupiter as a pale white or cream-colour. They will also reveal the planet's two most prominent cloud belts: the North and South Equatorial Belts , and with patience, Jupiter's most famous feature - its Great Red Spot. Jupiter is fainter than Venus because of its much greater distance from the Earth. Like Venus, Jupiter can also cast faint shadows at night when it is shining at its brightest and is observed under very dark skies. Jupiter's four brightest moons were first seen telescopically by Galileo in ; for this reason they are often referred to as the 'Galilean satellites' or simply the 'Galileans'.
Marte ,. God of War. Pyroeis "fiery one".
Greek god: Ares. Although it is popularly called ' The Red Planet ', it rarely appears red to the naked eye; in fact, it varies from pale orange-yellow to orange-red, depending upon its distance from the Earth and therefore, its brightness. The reddish colour is caused by the presence of iron oxide rust on the planet's surface. Occasional global dust storms on Mars, such as those which happened in and , can however make it appear decidedly yellowish.
For about six weeks either side of opposition, Mars can clearly be seen in twilight; at its brightest, Mars outshines Sirius the brightest star in the night sky but even at its more distant oppositions it outshines the star Arcturus magnitude When it is on the far side of its orbit from the Earth i.
Through a telescope , Mars typically appears amber or salmon-pink in color. Mars has two asteroid-like moons, Phobos and Deimos. A device known as an occulting bar can be used to conceal Mars from view in the telescopic eyepiece, allowing the moons to be spotted with greater ease. Star map showing the path of Mars through Aquarius, Pisces, Aries and Taurus from May to March click for full-size image, a detailed description of the apparition and Moon nearby dates for the period.
The first telescopic observation of Mars was by Galileo in Mars' polar caps were first observed by Giovanni Cassini in When Italian astronomer Giovanni Schiaparelli turned his telescope on Mars in , he saw what he believed to be a series of linear features criss-crossing the planet, which he named 'canali' Italian for 'channels', though it was incorrectly translated into English as 'canals'.
His observations were supported by other astronomers, the most notable being Percival Lowell founder of Flagstaff Observatory in Arizona but the idea was rejected by numerous others, who were unable to see the features that Schiaparelli had claimed to see. The 'canals on Mars' controversy was finally resolved when the first spacecraft were sent to take close-up pictures of the planet in the s. No canals were found to exist on Mars, and what Schiaparelli had probably seen were the result of telescopic defects or tricks of the eye.
Schiaparelli had also believed that the dark regions on Mars were caused by vegetation growth an idea first suggested by French astronomer E.
Liais in In , partly inspired by Schiaparelli and Lowell's ideas, English writer H. Naval Observatory in Washington, DC in The logic behind their idea seems to have been that, since the Earth had one moon and Jupiter was known to have four moons, Mars must have had an intermediate number, i. Mercurius ,. Messenger of the Gods. Stilbon "shining one". Greek god: Hermes. Consequently it can only be seen with the naked eye when it is low down in twilight shortly after sunset or before sunrise and it is never seen in fully dark skies.
Mercury typically makes three morning appearances and three evening appearances each year, though for any given location on Earth, Mercury will only be well placed for viewing on about half of these occasions because of the length of local twilight and the angle of the ecliptic to the local horizon. Around greatest elongation in the evening, binoculars will help to locate it - in the general direction of the sunset - around 45 minutes or so after sundown the exact time to start looking depends upon the length of local twilight after which its position should be easily pinpointed with the naked eye.
For the same reason, Mercury appears to scintillate twinkle more readily than the other bright planets.