Whois & Analysis for cosmos4kids.com

The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly.

Of those objects that orbit the Sun directly, the largest eight are the planets, with the remainder being significantly smaller objects, such as dwarf planets and small Solar System bodies.

Of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury.

Astronomy (from Greek: αστρονομία) is a natural science that studies celestial objects and phenomena.

It applies mathematics, physics, and chemistry, in an effort to explain the origin of those objects and phenomena and their evolution.

Objects of interest include planets, moons, stars, galaxies, and comets; while the phenomena include supernovae explosions, gamma ray bursts, and cosmic microwave background radiation.

More generally, all astronomical phenomena that originate outside Earth's atmosphere are within the purview of astronomy.

A related but distinct subject, physical cosmology, is concerned with the study of the Universe as a whole.

A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.

The word galaxy is derived from the Greek ', literally "milky", a reference to the Milky Way.

Galaxies range in size from dwarfs with just a few billion stars to giants with one hundred trillion stars, each orbiting its galaxy's center of mass.

Galaxies are categorized according to their visual morphology as elliptical, spiral and irregular.

Many galaxies are thought to have black holes at their active centers.

The Milky Way's central black hole, known as Sagittarius A*, has a mass four million times greater than the Sun.

As of March 2016, GN-z11 is the oldest and most distant observed galaxy with a comoving distance of 32 billion light-years from Earth, and observed as it existed just 400 million years after the Big Bang.

A star is a luminous sphere of plasma held together by its own gravity.

The nearest star to Earth is the Sun.

Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth.

Historically, the most prominent stars were grouped into constellations and asterisms, the brightest of which gained proper names.

Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations.

However, most of the stars in the Universe, including all stars outside our galaxy, the Milky Way, are invisible to the naked eye from Earth.

Indeed, most are invisible from Earth even through the most powerful telescopes.

Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.