Our Solar system

The Solar System^[a] is the gravitationally bound planetary system of the Sun and the objects that orbit it, either directly or indirectly.^[b] Of the objects that orbit the Sun directly, the largest are the eight planets,^[c] with the remainder being smaller objects, such as the five 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.^[d]

The Big Bang theory is the prevailing cosmological model for the observable universe^[1][2][3] from the earliest known periodsthrough its subsequent large-scale evolution.^[4][5][6] The model describes how the universe expanded from a very high-density and high-temperature state,^[7][8] and offers a comprehensive explanation for a broad range of phenomena, including the abundance of light elements, the cosmic microwave background (CMB), large scale structure and Hubble’s law (the farther away galaxies are, the faster they are moving away from Earth).^[9] If the observed conditions are extrapolated backwards in time using the known laws of physics, the prediction is that just before a period of very high density there was a singularitywhich is typically associated with the Big Bang. Physicists are undecided whether this means the universe began from a singularity, or that current knowledge is insufficient to describe the universe at that time. Detailed measurements of the expansion rate of the universe place the Big Bang at around 13.8 billion years ago, which is thus considered the age of the universe.^[10] After its initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, and later simple atoms. Giant clouds of these primordial elements (mostly hydrogen, with some helium and lithium) later coalesced through gravity, eventually forming early stars and galaxies, the descendants of which are visible today. Astronomers also observe the gravitational effects of dark matter surrounding galaxies. Though most of the mass in the universe seems to be in the form of dark matter, Big Bang theory and various observations seem to indicate that it is not made out of conventional baryonic matter (protons, neutrons, and electrons) but it is unclear exactly what it is made out of.

Earth is the third planet from the Sun, and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago.^[24][25][26] Earth’s gravity interacts with other objects in space, especially the Sun and the Moon, Earth’s only natural satellite. Earth orbits around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.^{[n 5]}

Earth’s axis of rotation is tilted with respect to its orbital plane, producing seasons on Earth.^[27] The gravitational interactionbetween Earth and the Moon causes tides, stabilizes Earth’s orientation on its axis, and gradually slows its rotation.^[28]Earth is the densest planet in the Solar System and the largest and most massive of the four terrestrial planets.^[29]

Earth’s lithosphere is divided into several rigid tectonic plates that migrate across the surface over many millions of years. About 71% of Earth’s surface is covered with water, mostly by oceans.^[30] The remaining 29% is land consisting of continents and islands that together contain many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earth’s polar regions are covered in ice, including the Antarctic ice sheet and the sea ice of the Arctic ice pack. Earth’s interior remains active with a solid iron inner core, a liquid outer core that generates the Earth’s magnetic field, and a convecting mantle that drives plate tectonics.

Within the first billion years of Earth’s history, life appeared in the oceans and began to affect the Earth’s atmosphere and surface, leading to the proliferation of aerobic and anaerobic organisms. Some geological evidence indicates that life may have arisen as early as 4.1 billion years ago. Since then, the combination of Earth’s distance from the Sun, physical properties, and geological history have allowed life to evolve and thrive.^[31][32] In the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species^[33]that ever lived on Earth are extinct.^[34][35] Estimates of the number of species on Earth today vary widely;^[36][37][38] most species have not been described.^[39] Over 7.6 billion humans live on Earth and depend on its biosphere and natural resources for their survival.^[40] Humans have developed diverse societies and cultures; politically, the world has about 200 sovereign states.

https://www.space.com/16080-solar-system-planets.html

Ever since the discovery of Pluto in 1930, kids grew up learning about the nine planets of our solar system. That all changed starting in the late 1990s, when astronomers began to argue about whether Pluto was a planet. In a highly controversial decision, the International Astronomical Union ultimately decided in 2006 to call Pluto a “dwarf planet,” reducing the list of “real planets” in our solar system to eight.

However, astronomers are now hunting for another planet in our solar system, a true ninth planet, after evidence of its existence was unveiled on Jan. 20, 2016. The so-called “Planet Nine,” as scientists are calling it, is about 10 times the mass of Earth and 5,000 times the mass of Pluto. [The Evidence for ‘Planet Nine’ in Our Solar System (Gallery)]

Did You Know? Three of the planets in the solar system are currently visible in the night sky in June 2017. They are: Venus, Jupiter and Saturn. You can find out how and when to see the brightest planets in June’s night sky here: The Brightest Planets in June’s Night Sky: How to See them (and When)

Here’s the order of the planets, starting nearest the sun and working outward through the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune — and Planet Nine.

Solar System Pictures: A Photo Tour

If you insist on including Pluto, then that world would come after Neptune on the list; Pluto is truly way out there, and on a wildly tilted, elliptical orbit (two of the several reasons it got demoted). Interestingly, Pluto used to be the eighth planet, actually. More on that below.

Our planet is our home and we have to take care of it !!!

https://www.youtube.com/watch?v=0Puv0Pss33M