Venus

-

Venus (planet), one of the planets in the solar system, the second in distance from the Sun. Except for the Sun and the Moon, Venus is the brightest object in the sky. The planet is called the morning star when it appears in the east at sunrise, and the evening star when it is in the west at sunset. In ancient times the evening star was called Hesperus and the morning star Phosphorus or Lucifer. Because of the distances of the orbits of Venus and Earth from the Sun, Venus is never visible more than three hours before sunrise or three hours after sunset.

When viewed through a telescope, the planet exhibits phases like the Moon. Maximum brilliance (a stellar magnitude of -4.4, 15 times as bright as the brightest star) is seen in the crescent phase when Venus is closer to Earth. Venus’s full phase appears smaller and dimmer because it occurs when the planet is on the far side of the Sun from Earth. The phases and positions of Venus in the sky repeat every 1.6 years (see Time; Year). Transits of Venus (when the planet moves across the face of the Sun as seen from Earth) are rare, occurring in pairs at intervals of a little more than a century. The next two transits will be in 2004 and 2012.

Topics:

Comments

Post a Comment

Popular posts from this blog

Characteristics of the Sun

-
Image
The distance between the sun and the earth varies because the earth travels in an elliptical rather than circular orbit. The distance is roughly 100 times the sun’s diameter. Turbulence in the photosphere forms granules of various sizes and sunspots. Temperature is a measure of kinetic energy . The dense plasma in the center of the sun is roughly 2500 times hotter than the surface. Gases in the corona have escaped from the sun’s surface and have a very high velocity. The sun’s spectral type, G2, indicates that it is composed of hydrogen , helium , calcium , iron and other metals.
Read more

Ecliptic

-
Ecliptic, in astronomy, the apparent great-circle annual path of the sun in the celestial sphere , as seen from the earth . It is so named because eclipses occur only when the moon is on or near this path. The plane of this path, called the plane of the ecliptic, intersects the celestial equator (the projection of the earth's equator on the celestial sphere) at an angle of about 23°27’. This angle is known as the obliquity of the ecliptic and is approximately constant over a period of millions of years, although at present it is decreasing at the rate of 48 seconds of arc in each century and will decrease for several millenniums until it reaches 22°54’, after which it will again increase. The two points at which the ecliptic intersects the celestial equator are called nodes or equinoxes. The sun is at the vernal equinox about March 21 and at the autumnal equinox about September 23. Halfway on the ecliptic between the equinoxes are the summer and winter solstices. The sun arrives a...
Read more

Galaxy

-
Image
Galaxy, a massive ensemble of hundreds of millions of stars, all gravitationally interacting, and orbiting about a common center. Astronomers estimate that there are about 125 billion galaxies in the universe. All the stars visible to the unaided eye from Earth belong to Earth’s galaxy, the Milky Way . The Sun , with its associated planets, is just one star in this galaxy. Besides stars and planets, galaxies contain clusters of stars; atomic hydrogen gas; molecular hydrogen; complex molecules composed of hydrogen, nitrogen, carbon, and silicon, among others; and cosmic rays (see Interstellar Matter ). Galaxy M100 The spiral galaxy M100 is located between 35 million and 80 million light-years from earth. The Hubble Space Telescope captured this image of the core of M100 after repairs were made to the telescope in December 1993. Galaxies M86 and M84 The elliptical galaxies M86 (center) and M84 (right) are members of the Virgo cluster of galaxies, located about 50 million light-years awa...
Read more