Sun

The Sun is the superstar at the centre of our Solar system. It is infrequently referred to as Sol to differentiate it from other "suns". Planet Earth orbits the Sun, as do many other bodies, together with other planets, asteroids, meteoroids, comets and dust. Its heat and light support almost all life on Earth.

The Sun has a mass of about 2×1030kg, which is to some extent higher than that of an average star. About 74% of its mass is hydrogen, with 25% helium and the respite made up of trace quantities of heavier elements. It is consideration that the Sun is about 5 billion years old, and is about half way through its main sequence evolution, during which nuclear fusion reactions in its core fuse hydrogen into helium. In about 5 billion years time the Sun will be converted into a planetary nebula.

Although it is the nearest star to Earth and has been intensively studied by scientists, many questions about the Sun hang about unanswered, such as why its outer atmosphere has a temperature of over 106 K when its visible surface (the photosphere) has a temperature of just 6,000 K.

Caution: Looking straight at the Sun can damage the retina and one's eyesight.

space missions

space missions are individuals using remote-controlled spacecraft.

The initial such mission was the Sputnik I mission, launched October 4, 1957. Some missions are more appropriate for unmanned missions rather than manned space missions, due to lower cost and lower risk factors.

Since the early 1970s, most unmanned space missions have been based on space probes with integral mission computers, and as such may be classified as embedded systems.

Most American unmanned missions have been coordinated by the Jet Propulsion Laboratory, and European missions by the European Space Operations Centre, division of ESA (the European Space Agency).

Seedless fruits

Seedlessness is an imperative feature of some fruits of commerce. Profitable cultivars of bananas and pineapples are examples of seedless fruits. Some cultivars of citrus fruits (especially navel oranges and mandarin oranges), table grapes, grapefruit, and watermelons are esteemed for their seedlessness. In some species, seedlessness is the result of parthenocarpy, where fruits locate without fertilization. Parthenocarpic fruit situate may or may not require pollination. Most seedless citrus fruits want a pollination stimulus; bananas and pineapples do not. Seedlessness in table grapes domino effect from the abortion of the embryonic plant that is produced by fertilization, a phenomenon known as stenospermocarpy which requires normal pollination and fertilization.

Multiple fruit

A multiple fruit is one formed from a group of flowers (called an inflorescence). Each flower produces a fruit, but these adult into a single mass. Examples of multiple fruit is the pineapple, edible fig, mulberry, osage-orange, and breadfruit.In a few plants, such as this noni, flowers are produced repeatedly along the stem and it is possible to see together examples of flowering, fruit development, and fruit ripening.

In the photograph on the right, stages of flowering and fruit development in the noni or Indian mulberry (Morinda citrifolia) can be observed on a single branch. First an inflorescence of white flowers called a top is produced. After fertilization, each flower develops into a drupe, and as the drupes expand, they develop into connate (merge) into a multiple fleshy fruit called a syncarpet.