Dark Energy

Dark Energy is the energy that helps the Universe to accelerate and to move galaxies to move away from each other. Dark Energy is one of the most believed theory which explains the expansion of the Universe at a high rate.
In short, Dark Energy helps in the functioning of the Universe.

At the early stages of The Big Bang, the explosion should have been slowed down by the force of gravity. But, the Hubble Telescope noted significant increase in the speed of expansion of the present Universe when compared to the early stages.

So what's causing the acceleration in the expansion of the Universe? Yeah, some call it Dark Energy. 

Dark Matter

Much like it's name suggests, it's filled with dark stuff. Yeah, we haven't seen it. We just know it exists.

In our Universe, we have 4.9% of matter (You, me, stars, planets, blackholes etc), 26.8% Dark matter (Baryon based clouds, etc) and 68.3% dark energy.

Dark Energy is like, anti-gravity. Gravity pulls objects closer but the Dark Energy pushes two galaxies away from each other.

Neighbours across the outer space :

Comet

Mars

Venus 

Near Earth Objects

Proxima Centauri

Cannis Major Dwarf 

Our planet Earth is not alone. It has many neighbours in the outer space.
The nearest neighbour to Earth is it's very own natural satellite, the Moon.

The second nearest neighbour to Earth is the planet Venus (At times) which is at a distance of about 38 million kilo meters at the closest point and 261 million kilo meters at the farthest point.

On the other hand, Earth is also surrounded by Mars, which is at a distance of 54 million kilo meters at the closest point and 401 million kilo meters on the farthest point,

Planet Earth also has millions of Near Earth Objects (NEO's) as it's neighbours.

The nearest star to Earth is our Sun.The closest distance between Earth and Sun is about 147 million kilo meters at the closest point.

The second nearest Star to Earth is the Proxima Centauri which is 4.23 light years i.e., around 4*10^16 meters.

Our planet is located in the Milky way Galaxy. The nearest Galaxy to Earth is the Cannis Major Dwarf (Located within Milky way itself. A galaxy within a Galaxy) (Yes, not Andromeda) which is about 25,000 light years from Earth.

The nearest Black hole to Earth : The V4641 Sagittarii, a micro-quasar which is about 1,600 light years from Earth.
(Some say that the speculations on the distance of V4641 Sagittarii are wrong and it is at a distance of about 25,000 light years).

Apart from all these celestial neighbours, we've even got comets.

Moon

Brightest Object in the Universe :

The Brightest Star in the night sky is, undoubtedly Sirius star system.
But, the brighest objects of the Universe are the Quasars. Quasars draw their energy from the blackholes, i.e., Quasars are powered by the Blackholes. Quasars are known to emit energy thousands of times the energy released by an entire galaxies. Quasars are immensely bright and immensely powerful. 

The 3C 273 Quasar, located in the constellation Virgo is the brightest Quasar.
The light from 3C-273 easily outshines the light coming from the stars of our Galaxy.
The Quasar is located at a distance of 2.5 billion light years. It was discovered by Allan Sandage. The Quasar, 3C-273 is about 4 trillion times brighter than our Sun!
Quasars are not just bright, but also huge! The mass of the Quasar is estimated to be around 886 ± 187 solar masses. 
The name 3C-273 indicates that it is the 273'd object in the third Cambridge Catalogue of radio sources.

ISRO Mangalyaan Mission :

India's maiden mission to the red planet was launched successfully yesterday at 2:38 PM with Polar Satellite Launch Vehicle C-25 (PSLV C-25).

ISRO (Indian Space Research Organisation) had successfully injected Mangalyaan-Mangal : Mars, yaan: aircraft- Orbiter into the Earth from Sriharikota.

The Mangalyaan Mission holds the record for the lowest mission to Mars.The cost of Mangalyaan Mission costed about 450 Crores(USD 75 Million).

The main objective of Mangalyaan would be to look for the presence of Methane gas on the surface of Mars which would be an indicator for life to exist on it.
The PSLV C-25 was launched precisely into the elliptical orbit around Earth where it would stay for around 25 days extending it's range from 250 km to 23,500 km, slowly moving towards Mars.
The probe is said to reach Mars after a 10 month journey in mid-September.

The Mangalyaan Mission is estimated to be around one-tenth of the cost of NASA's mission to Mars (671 Million USD)

If the probe successfully reaches Mars, it would make India the first Asian Country to successfully send a probe to Mars, the fourth country to successfully send a mission to Mars, after United States, Russia and Europe.

The satellite would travel a distance of over 200 Million km's to reach Mars.


Scientists at ISRO are still worried about the mission as only 21 missions of 51 missions sent to Mars have been successful.

The Probe is equipped with five instruments :
1) Lyman Alpha Photometer.
2)Methane Sensor for Mars. (To search for existence of life)
3)Mars Exospheric Neutral Composition Analyser (MENCA)
4)Mars Colour Camera (MCC)
5)Thermal Infrared Imaging Spectrometer.
On the 1st of December, 2013, the space craft is gonna leave the earth's sphere of influence.

Hottest Star in the Universe :

Ever wondered what the hottest star in the Universe is?

The Eta Carinae is the hottest star found till now.
The Eta Carinae is present at a distance of about 7,500 light years from Sun in the constellation Carina. The Eta Carinae is a stellar star system (Two stars orbiting each other) consisting of a luminous blue variable that has 150 times the mass of sun and a hot super giant that has 30 times the mass of sun.

Eta Carinae was first catalogued by Edmond Halley in 1677.
It got it's name from the constellation it was present in and because Nicolas Louis de Lacaille assigned the star the Greek letter Eta.
When Eta Carinae was first observed in 1677, it was a 4th magnitude star but in the Mid 18th century, it's brightness increased and it turned into a second-magnitude star.
And

But because of the massive size of the star, it's life tends to burn up short. The star is slowly loosing away most of it's mass.
The Eta Carinae is also surrounded by the Homunculus Nebula and they combined have a luminosity of five million suns!

Eta Carinae will soon collapse into a supernova or a hypernova. And, the blast would disintegrate everything surround it.

The Surface temperature of Eta Carinae is about 72,000 degrees!

W26 Super Giant :

The W26 Red Super giant of the Westerlund 1, of the Milky Way is about 1,500 times wider than our Sun.
The Westerlund 1 is probably the largest collection of stars in the Milky Way galaxy. The W26 Red Super giant is about 16,000 light-years away from Earth.
The second coolest thing about W26 is that it's the only red super giant which is surrounded by an ionised nebula. The ionised hydrogen gas present around W26 glows in green causing it to be special.

The W26 red super giant is at the end of it's life and would probably turn into a supernova soon.
Stars with such his masses tend to live a short and quick life.

Coldest Place in the Universe :

Ever wondered what the coldest place in the Universe would be?

The answer is the Boomerang Nebula.

The Boomerang Nebula is located about 5,000 light-years away from Earth in the constellation Centaurus.The temperature in Boomerang Nebula is estimated to be at around -272.15 C or -457F making it the natural coolest place in the Universe.Boomerang reaches -272C when the lowest limit of temperature is -273C. The Boomerang Nebula is commonly known as a Bow Tie Nebula and is catalogued as PGC 3074547. It is a
It was observed first in 1980 by Keith Taylor and Mike Scarrott and in 1998, it was photographed by the Hubble Space Telescope.
Apart from the CMB cold spot, the Boomerang Nebula is the only object with temperature lower than the background radiation.

Image of Boomerang Nebula by Hubble. 

Quarks :

Quarks are elementary sub-atomic particles and a fundamental constituent of matter.
Quarks combine to form protons, neutrons and mesons.Particles formed by the combination of Quarks are hadrons.
Hadrons are of two types :
1)Baryons.
2)Mesons.
Particles consisting of 3 quarks come under Baryons.Protons and Neutrons come under the baryon family.
Particles consisting of a quark and an anti-quark come under the Meson family.
Assumptions on the existence of other hadrons like tetraquarks (Exotic mesons) and Pentaquarks(Enotic baryons) have been made but their hardly exists any evidence to support the fact.
Quarks are divided into six types which are known as the six flavours : up, down, strange, charm, bottom and top.
Up Quark and Down Quark are the most stable of all the Quarks and are also the most commonly found quarks. They also hold the lowest masses of all the quarks.

If a particles exists, it's anti-particle is sure to be found.  Every quark has a corresponding anti-particles known as the antiquark. Quarks and Antiquarks differ only in few properties. They posses same magnitude but have the opposite signs.

The Quark Model was proposed by Murray Gell-Mann and George Zweig in 1964.

Of all the quarks, top quark was the last to be discovered.

A proton, a part of the Baryon family has 3 quarks. Two up quarks and one down quark and a Neutron posses two down quarks and one up quark. 

Types of Quarks. 

Neutron

Proton

Chandrasekhar Limit :

Subrahmanyan Chandrasekhar

Wilhelm Anderson

Chandrasekhar Limit was proposed by Wilhelm Anderson and E.C. Stoner who named it after Subrahmanyan Chandrasekhar, the renowed Indian-American Astrophysicist who made modifications on the calculations in 1930. Chandrasekhar Limit is actually the maximum mass of a stable white-dwarf star. The currently accepted value of the limit is about 1.44 solar masses or 2.864 x 10³⁰ kg.
 Stars exceeding the limit would eventually collapse under their own weight and become neutron stars or black holes.Stars below the limit would be prevented from collapsing by the degeneracy pressure exerted by the electrons. 

Edmund Clifton Stoner 

Units of distance in space :

Distance in space is not measured the same way as distance is measured on Earth. Using distances like meters or kilo meters in outer space is like using a scale to radius of the Earth. Distances in space are seriously high.

Light Year :

The most prominent and common unit to measure distance in space is the light-year.
A light-year is the distance travelled by a light ray in one year in vacuum.
Light travels at an amazing speed of about 300,000 kilometres per second.

So, in an year, light travels the distance of 9.4605284 × 10¹⁵ meters.

The second nearest star to Earth (Proxima Centauri) is at a distance of 4.3 light-years.
Andromeda, our nearest galaxy is at a distance of 2.3 million light-years from us.

Astronomical Unit (A.U.) :
An astronomical unit (A.U.) is one of the smallest unit of cosmic-measurements. An Astronomical Unit in other words is the distance between the Earth and the Sun that is, about 93 million miles.
A.U. are usually used to measure distances just within our solar system.Mercury is 1/3rd of an A.U. from the Sun and Pluto is about 40 A.U. from the Sun. 

Parsecs : 
To measure distances longer than a light year, astronomers use the Parsec unit (pc).
One parsec is equivalent to 3.26 light-years. A parsec stands for "Parallax of one arc second".
A parsec is 3.08567758 × 10¹⁶ meters.

Kilo parsec : 

A kilo parsec or a kpc is one-thousand parsecs. A kiloparsec is 3.08567758 × 10¹⁹ meters.
Megaparsec : 

A megaparsec or mpc is one million parsecs. 3.08567758 × 10²² meters.