UNIVERSE - PART 4

(UPSC & TNPSC Important Notes)

DWARF PLANETS:
Pluto, Charon, Ceres, Eris were newly grouped as “Dwarf Planets” in the year 2008. They also revolves around the sun. They also revolve around the sun. They are very small in size. Their Size is smaller than our Moon. So they are called DWARF PLANETS.
   
ASTEROIDS:
Thousands of Asteroids are found between Mars and Jupiter. Asteroids are Clusters of Celestial Bodies which Includes tiny Stones and big rocks which can measure upto 300 to 400 km in Diametre.

METEOROIDS:
The Sudden Streaks of light seen on a starry night is called as METEOROIDS. This can be seen when the remains of the rocky parts of the comets strike the Earth’s atmosphere and streaks of light are generated. They are not stars that fall down.

COMET:
•    It is exciting to see a comet in a Night Sky. A Comet is not a star.
•    It is a Rock made of Dust and Ice.
•    The long tails is seen because, as the comet comes near the sun, the ice melts and reflects the light of the sun.
•    The tail of the comet is seen in the opposite direction of the sun.
•    The tail of the comet appears because minute particles from the sun strike the gaseous part emitted from the comet.

BLACK HOLE:
•    Black holes are not physically large regions of space.
•    But when you include their mass, they are among the top competitors for the largest things in the universe.
•    And quasar OJ287 is the largest black hole we’ve spotted.
•    It’s estimated to be 18 billion times the mass of our sun and is a supermassive black hole located in the center of a galaxy.
•    To put that in perspective, it’s an object larger than our entire solar system. Just how big can a black hole get? According to scientists, there is no theoretical upper limit.

MOON :
•    The moon is not a Planet.
•    Moon does not revolve around the sun directly.
•    It revolves around the Earth. Hence it is called as a Satellite.
•    The Moon is the Satellite of the earth.

DARK MATTER :
•    Dark matter is a hypothetical kind of matter that is invisible to the entire electromagnetic spectrum, but which accounts for most of the matter in the Universe.
•    The existence and properties of dark matter are inferred from its gravitational effects on visible matter, radiation, and the large-scale structure of the Universe.
•    Other than neutrinos, a form of hot dark matter, dark matter has not been detected directly, making it one of the greatest mysteries in modern astrophysics.
•    Dark matter neither emits nor absorbs light or any other electromagnetic radiation at any significant level.
•    Dark matter is estimated to constitute 26.8% of the total mass–energy and 84.5% of the total matter in the Universe.

DARK ENERGY :
•    Two proposed forms for dark energy are the cosmological constant, a constant energy density filling space homogeneously, and scalar fields such as quintessence or moduli, dynamic quantities whose energy density can vary in time and space.
•    Contributions from scalar fields that are constant in space are usually also included in the cosmological constant. The cosmological constant can be formulated to be equivalent to vacuum energy. Scalar fields having only a slight amount of spatial in homogeneity would be difficult to distinguish from a cosmological constant.

Layers Of Atmosphere
•    An atmosphere (atmos meaning ‘vapour’), and  (sphaira, meaning ‘sphere’) is a layer or a set of layers of gases surrounding a planet or other material body, that is held in place by the gravity of that body.
•    An atmosphere is more likely to be retained if the gravity it is subject to is high and the temperature of the atmosphere is low.

The atmosphere of Earth is composed of :
Nitrogen (about 78%) – nitrogen is fixed by bacteria and lightning to produce ammonia used in the construction of nucleotide.
Oxygen (about 21%) – Oxygen is used by most organisms for respiration
Argon (about 0.9%)
Carbon dioxide, Methane, Rare (inert) gases(about 0.1%)

Layers of the atmosphere :
The atmosphere is composed of discrete layers. Atoms and molecules travel rapidly within a layer but only very slowly between layers. The layering results from temperature variations of the gas molecules.
•    Troposphere
•    Stratosphere
•    Mesosphere
•    Thermosphere
•    Exosphere
•    Ionosphere

LAYERS OF ATMOSPHERE 

1. Troposphere
•    The troposphere is the lowest layer of our atmosphere.
•    Starting at ground level, it extends upward to about 10 km (6.2 miles or about 33,000 feet) above sea level.
•    We humans live in the troposphere, and nearly all weather occurs in this lowest layer.
•    The standard lapse rate for the troposphere is a decrease of about 6.5 degrees Celsius (C) per kilometer (km) (or about 12 degrees F).
•    Near the surface, the lapse rate changes dramatically from hour to hour on clear days and nights.
•    Sometimes the temperature does not decrease with height, but increases. Such a situation is known as a temperature inversion.
•    Most clouds appear here, mainly because 99% of the water vapor in the atmosphere is found in the troposphere.
•    Air pressure drops, and temperatures get colder, as you climb higher in the troposphere.

2. Stratosphere
•    The next layer up is called the stratosphere.
•    The stratosphere extends from the top of the troposphere to about 50 km (31 miles) above the ground.
•    The infamous ozone layer is found within the stratosphere.
•    The standard inverse lapse rate for the Stratosphere is about 6.5 degrees Celsius (C) per kilometer (km) (or about 12 degrees F).
•    Ozone molecules in this layer absorb high-energy ultraviolet (UV) light from the Sun, converting the UV energy into heat.
•    Unlike the troposphere, the stratosphere actually gets warmer the higher you go.That trend of rising temperatures with altitude means that air in the stratosphere lacks the turbulence and updrafts of the troposphere beneath.
•    Commercial passenger jets fly in the lower stratosphere, partly because this less-turbulent layer provides a smoother ride.
•    The jet stream flows near the border between the troposphere and the stratosphere.

3. Mesosphere
•    Above the stratosphere is the mesosphere.
•    It extends upward to a height of about 85 km (53 miles) above our planet.
•    Most meteors burn up in the mesosphere.
•    Unlike the stratosphere, temperatures once again grow colder as you rise up through the mesosphere.
•    The coldest temperatures in Earth’s atmosphere, about –90° C (-130° F), are found near the top of this layer.
•    The air in the mesosphere is far too thin to breathe; air pressure at the bottom of the layer is well below 1% of the pressure at sea level, and continues dropping as you go higher.

3. Thermosphere
•    The layer of very rare air above the mesosphere is called the
•    High-energy X-rays and UV radiation from the Sun are absorbed in the thermosphere, raising its temperature to hundreds or at times thousands of degrees.
•    However, the air in this layer is so thin that it would feel freezing cold to us. In many ways, the thermosphere is more like outer space than a part of the atmosphere.
•    Many satellites actually orbit Earth within the thermosphere.
•    Variations in the amount of energy coming from the Sun exert a powerful influence on both the height of the top of this layer and the temperature within it.
•    Because of this, the top of the thermosphere can be found anywhere between 500 and 1,000 km (311 to 621 miles) above the ground.
•    Temperatures in the upper thermosphere can range from about 500° C (932° F) to 2,000° C (3,632° F) or higher. The aurora, the Northern Lights and Southern Lights, occur in the thermosphere.

4. Exosphere
•    Although some experts consider the thermosphere to be the uppermost layer of our atmosphere, others consider the exosphere to be the actual “final frontier” of Earth’s gaseous envelope.
•    As you might imagine, the “air” in the exosphere is very, very, very thin, making this layer even more space-like than the thermosphere.
•    In fact, air in the exosphere is constantly – though very gradually – “leaking” out of Earth’s atmosphere into outer space.
•    There is no clear-cut upper boundary where the exosphere finally fades away into space. Different definitions place the top of the exosphere somewhere between 100,000 km (62,000 miles) and 190,000 km (120,000 miles) above the surface of Earth. The latter value is about halfway to the Moon.

5. Ionosphere
•    The ionosphere is not a distinct layer like the others mentioned above.
•    Instead, the ionosphere is a series of regions in parts of the mesosphere and thermosphere where high-energy radiation from the Sun has knocked electrons loose from their parent atoms and molecules.
•    The electrically charged atoms and molecules that are formed in this way are called ions, giving the ionosphere its name and endowing this region with some special properties.