Galaxy

Our Galaxy

The name of our galaxy is Milky Galaxy.It called so because  its appearance as a dim milky  glowing band arching across the night sky. The Milky Way appears like a band because it is a disk-shaped structure being viewed from inside..It was proven in 1610  by  Galileo Galilei used his telescope.. 

                          

The Milky Way is a barred spiral galaxy 100,000–120,000 light-years in diameter containing 200–400 billion stars. The Galaxy as a whole is moving at a velocity of 552 to 630 km per second, depending on the relative frame of reference. It is estimated to be about 13.2 billion years old, nearly as old as the Universe consists of a bar-shaped core region surrounded by a disk of gas, dust and stars.

Solar System

Our solar system consists of the Sun, Mercury ,Venus ,Earth ,Mars ,Saturn ,Uranus ,Neptune ,and Pluto .However Pluto considered a planet until August 24, 2006, when the International Astronomical Union (IAU) defined conditions for planets that Pluto did not meet.

Sun

Its is the star located in the center of solar system.

Diameter of about 1,392,000 km, about

Mass (about 2×1030 kilograms

Composition: Hydrogen 73.46%,Helium 24.85%,Oxygen  0.77%,Carbon 0.29%,Iron 0.16%,Neon  0.12%,Nitrogen 0.09%,Silicon 0.07%,Magnesium 0.05%,Sulfur 0.04% 

Surface temperature : approximately 5778 K (5505 °C

Distance from earth:: 149.6 million km (93 million miles)

Mercury

 First planet in our solar system

Distance from Sun: 35,983,047 miles (57,909,100 km)

Mass: 1.805E24 kg (0.3022 Earth mass)

Gravity: 3.7 m/s²

Length of day: 58d 15h 30m

Density: 5.43 g/cm³

Length of year: 88 days

Distance from earth: 91.7 million km (57 million miles)    

Venus 

Second planet from the Sun

Distance from Sun: 67,237,912 miles (108,208,930 km)

Gravity: 8.87 m/s²

Mass: 29.08E24 kg (4.868 Earth mass)

Length of day: 117d 0h 0m

Density: 5.20 g/cm³

 Length of year :224.7 Earth days

Distance from earth: 41.4 million km (25.8 million miles)

Earth 

Our home..Third planet from the Sun.

Mean radius:6,371.0 km

Circumference:40,075.017 km 

Length of year :366.26 time

Distance from Sun: 149.6 million km (93 million miles)

Mars

Fourth planet from the Sun i

Distance from Sun: 141,634,790 miles (227,939,100 km)

Mass: 3.833E24 kg (0.6418 Earth mass)

Length of day: 1d 0h 43m

Density: 3.93 g/cm³

Orbital period: 687 days

Distance from Earth :78.3 million km (48.6 million miles) 

Jupiter

 Fifth planet from the Sun and also largest planet in our Solar System

Distance from Sun: 483,766,802 miles (778,547,200 km)

Gravity: 24.79 m/s²

Density: 1.33 g/cm³

Length of day: 0d 9h 56m

Length of year: 12 year

Distance from earth: 624.4 million km (390.6 million miles)

Saturn

Sixth planet from the Sun and the second largest planet in the Solar System.

Distance from Sun: 890,704,144 miles (1,433,449,370 km)

Mass: 3.395E27 kg (568.5 Earth mass)

Gravity: 10.44 m/s²

Density: 687.00 kg/m³

Length of day: 0d 10h 39m

Distance from Earth : 1.25 billion km (777 million miles)

Uranus 

Seventh planet from the Sun. Uranus was the first planet discovered since ancient times. William Herschel discovered it in 1781. Herschel was a British astronomer, a scientist who studies planets and stars. Scientists have learned much about Uranus from the flight of the United States spacecraft Voyager 2. The spacecraft flew close to Uranus and took pictures. It sent these pictures back to Earth.

Distance from Sun: 1,787,485,511 miles (2,876,679,082 km)

Gravity: 8.69 m/s²

Mass: 86.81E24 kg (14.54 Earth mass)

Discovered: March 13, 1781

Density: 1.27 g/cm³

Distance from earth: 2.72 billion km (1.69 billion miles)

Neptune 

 Eighth planet from the Sun in the Solar System. 

Distance from Sun: 2,798,310,157 miles (4,503,443,661 km)

Gravity: 11.15 m/s²

Mass: 611.7E24 kg (102.4 Earth mass)

Density: 1.64 g/cm³

Distance from Earth : 4.35 billion km (2.7 billion miles) from Earth

Pluto

Although Pluto located within our galaxy,it is  not a planet. A planet is an object that orbits the sun and is large enough to have become round due to the force of its own gravity. In addition, a planet has to dominate the neighborhood around its orbit.Pluto has been demoted because it does not dominate its neighborhood. Charon, its large moon, is only about half the size of Pluto, while all the true planets are far larger than their moons.So sad..

Distance from Sun: 5,913,520,000 km

Distance from Earth: 149,600,000 km

Mass :1.3 x 1022kilograms

Density : 1.92 to 2.06 gm/cc 

Surface composition : H2O, N2, CH4, CO ices 

Atmospheric composition :N2, CH4, CO 

Surface temperature : 40 Kelvin (= -233 C) 

Spin period : 6.39 days 

Orbital period of Charon around Pluto :6.39 days 

Orbital period of Pluto around Sun:248 years 

Black hole

A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space.Once inside, nothing can escape a black hole's gravity, not even light.This can happen when a star is dying.  

Because no light can get out, people can't see black holes. They are invisible. Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other 

Black holes can be big or small. Scientists think the smallest black holes are as small as just one atom. These black holes are very tiny but have the mass of a large mountain .Another kind of black hole is called "stellar." Its mass can be up to 20 times more than the mass of the sun. There may be many, many stellar mass black holes in Earth's galaxy. Its sounds so scary right??

The largest black holes are called "super massive." These black holes have masses that are more than 1 million suns together. Scientists have found proof that every large galaxy contains a super massive black hole at its center. The super massive black hole at the center of the Milky Way galaxy is called Sagittarius A. It has a mass equal to about 4 million suns and would fit inside a very large ball that could hold a few million Earths.

 According to Nasa formed when the universe began. Stellar black holes are made when the center of a very big star falls in upon itself, or collapses. When this happens, it causes a supernova. A supernova is an exploding star that blasts part of the star into space. Scientists think super massive black holes were made at the same time as the galaxy they are in.Nasa also stated that Black holes do not go around in space eating stars, moons and planets. Earth will not fall into a black hole because no black hole is close enough to the solar system for Earth to do that. Even if a black hole the same mass as the sun were to take the place of the sun, Earth still would not fall in.

 The black hole would have the same gravity as the sun. Earth and the other planets would orbit the black hole as they orbit the sun now. The sun will never turn into a black hole. The sun is not a big enough star to make a black hole. Is that true??We can’t predict how far true is this…Lets just wait and see..

Watch this video about black hole if you'r free.Until then take care..

Black Hole

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Source:Nasa

By Lakdhes