Is a comet always visible from the Earth?
A comet normally emits no light of its own and can be seen only when it reflects light from the Sun. since the comets are extremely tiny, they are not visible when they are far from the Sun. A comet, however, develops a vapour cloud for a short period when it is near the Sun, which enables it to reflect more of the Sun’s light and become more visible. The gases in the vapour cloud also emit light when the ultraviolet light from the Sun falls on them. Consequently most of the comets are visible from earth only during a portion of their total period of orbit. However, some short period comets like Encke are always visible through telescopes.
What is the shape of the solid portion of a comet?
The solid portion of a comet is of irregular shape, since its gravitation is too weak to make the material assume a spherical shape as in the case of the planets.
What comets are known as Sun grazers?
Sun grazers are comets that almost touch the Sun during their orbit. Some come perhaps as close as 27,000 km from the visible surface of the Sun. an example is comet Ikeya-Seki which grazed the Sun in 1965.
What are cometary gas jets?
Sometimes, some internal portions of a comet’s nucleus may vapourise due to the heat from the Sun. The gas then escapes through cracks on the surface of the nucleus in the form of gas jets.
What is a cometary corona?
The cometary vapour cloud is surrounded by a glowing halo or corona due to the breakdown of the water molecules by the Sun’s radiation. The halo is very faint and cannot be seen from Earth but only form space.
Does a comet spin on its axis?
The spinning motion of come upon it’s appears to be at random and the axis may keep on shifting. The gas jets also act like thrusters and produce changes in the rotation of the nucleus. Form past observations, it has been noted that period of spinning of comet Encke has not appreciably changed during the past 140 years. But, some other comets show marked changes.
How are comets named?
Comets are usually named after the person or persons who discovered them. For example, comet Ikeya-Seki is named after Kaoru Ikeya and Tsutomu Seki of Japan who discovered it.
Are there any known comets not named after their discoverers?
Yes. For example Halley’s Comet is named after Edmond Halley who did not discover the comet but accurately predicted the period of its orbit as 76 years.
Another one is Twefik’s comet discovered in Egypt in 1882 and named after the king of Egypt.
Which ancient civilization studied comets closely?
Chinese astronomers have kept detailed records of comets for 1,300 years.