THE UNIVERSE PART-2

THE UNIVERSE PART-2

The universe is at least 99.99% empty space. Floating in this vast, dark void. There are all sorts of different objects, which astronomers call celestial bodies; they range from grains of dust to planets, stars, and galaxies. Our planetary group incorporates a star, the sun, and an enormous group of planets and moons that are framed by the very haze of gas that brought forth the sun. In recent years, Planets have been seen around hundreds of other stars, showing that our solar system maybe one of billions in our galaxy.

Rocky lumps left over from the formation of the solar system are called asteroids. They range in size from stones to bodies near the size of a bantam planet.

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These are chunks of ice from the outer reaches of the solar system. Some develop long tails of gas and residue as they approach the sun and are warmed by it.

A moon, also called a natural satellite, is a body that orbits a planet. Earth has only one moon, but the planet Jupiter has 67, including Lo.

Dwar planets are larger than steroids but smaller than planets. Like planets, they are round in shape. Pluto is best known as a dwarf planet.

It is a large and nearly spherical object that orbits a star and has swept its orbital path clear of debris. The solar system has 8 planets.

These brilliant bundles of gases, for example, the sun, sparkle by producing their own atomic power, and stars arrive in many kinds, temperatures, and sizes.

A glowing cloud of gas and dust in space is known as a nebula. Some nebulae are clouds of wreckage created by dying stars; others give birth to new stars.

LOOKING BACK IN TIME

THE UNIVERSE: Because light takes time to travel, when we look into space, we are looking back in time. the most distant objects visible are galaxies photographed by the Hubble Telescope. We saw them as they were 30 billion years ago. The universe extends far beyond these, but it is impossible to see objects much further because their light has not had time to reach them.

The light from the faintest galaxies in this photo from the Hubble Telescope took 3 billion years to reach Earth.

THE UNIVERSE: The elements hydrogen and helium make up 98 percent of the matter we can see in the universe. But there does not seem to be enough matter to account for the way stars and galaxies are pulled by gravity. As a result, astronomers think galaxies contain dark matter, which we cannot see. There is likewise an obscure power that makes the universe extend, known as dull energy.

One of the biggest questions in science is whether life is unique to Earth or has arisen in other worlds. And if life has appeared elsewhere, could intelligent beings have evolved? Scientists have set up a project to watch and listen for signals from extraterrestrials, and messages have been sent to the stars to inform any aliens out there of our existence.

THE UNIVERSE: In 1974, scientists used the giant Arecibo Radio Telescope in Puerto Rico to broadcast a radio message towards the star cluster M13. The message contains a symbol (right) to represent human beings, our base-10 counting system, DNA molecules, and the solar system. This is more of a publicity stunt than a serious attempt to contain aliens; the broadcast will take 25,000 years to reach M13, and a reply will take 25,000 years to return.

The robotic spacecraft pioneers 10 and 11 visited the planets Jupiter and Saturn in 1973–74 and then flew off into deep space. If aliens ever discover a craft drifting through interstellar space, they will find a gold-planet plaque engraved with a message from Earth.

Astronomers involved in the Seti (search for extraterrestrial intelligence) project used powerful radio telescopes to scan the skies in search of artificial radio signals broadcast by alien civilizations. The SETI project has been running starting around 1960, however it has up to this point tracked down no convincing proof of outsider signs, regardless of a few misleading problems.

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