The universe and solar system pt. 1

• The smallest planet in our solar system is Mercury
• Pluto was previously considered the 9th planet in our solar system
• In 2006, the International Astronomical Union (IAU) declared that Pluto is not a planet
• Criteria for a celestial body to be considered a planet

  • Revolve around the sun

  2. Be spherical in shape

  3. Have cleared the area around its orbit of any equivalent or bigger celestial bodies
• Pluto was reclassified as a 'dwarf planet'
• The understanding of the origin, evolution, structure, and fate of the universe is called Cosmogeny.
• Galaxy: a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction.
• Galaxy is a cluster of billions of stars, planets, asteroid or other bodies in the accompanying planetary systems.
• In between cluster is practically an empty space.
• The Milky Way is a spiral galaxy with a disk of stars and a central bulge.
• The Milky way is a large group of stars, gas, and dust held together by gravity.
• The universe is 13.8 billion years old.
• The diameter of the universe is possibly infinite.
• The universe should be at least 93 billion light years or more.
• 1 light year = $\ 9.4607 *$$(10)^12 km$
• The astronomers estimated the age of the universe by looking at oldest stars.
• The farther away from earth an object is, the longer it has taken light from the object to travel across space and reach earth
• Velocity is the rate of expansion of the universe.
• Distance is the estimated diameter of the universe.
• The Big Bang Theory suggests that the universe expanded rapidly during its first few moments.
• Hubble's law states that galaxies are moving away from us at speeds proportional to their distance from us
• Velocity = Distance / TIme
• The Big-bang Theory is the prevailing cosmological model for the universe from the earliest known periods through its subsequent large-scale evolution.
• The Big Bang Theory Postulates that around 13.8 billion years ago, the universe expanded from a tiny, dense, and hot mass of energy (singularity) to its present size and much cooler state.
• Singularity signifies the idea of a single, tiny point, which was postulated as the origin of the universe.
• There is no "bang" in the Big Bang Theory.
• In the Big Bang Theory, there was no explosion, rather it is an expansion.
• The Big Bang theory was proposed by the Belgian physicist and Catholic priest Georges Lemaître.
• Edwin Hubble's observations of the redshift of distant galaxies provided evidence supporting the idea of an expanding universe, which lent further support to the concept of the Big Bang.
• The term "Big Bang" was coined by the British astrophysicist Fred Hoyle during a BBC radio broadcast in 1949
• Georges Henri Joseph Édouard Lemaître is the full name of Georges Lemaitre
• The Big Bang Theory is the most accepted because of Hubble's Law
• Redshift indicates that the astronomical body being observed is moving away very fast relative to an observation, for example station on earth.
• Light from most distant galaxies was shifted to red end of the electromagnetic spectrum.
• The longer the light travels, the more it gets redshifted.
• Hubble noticed that the further away the galaxy, the greater the redshift of its spectral lines.
• The Doppler effect, named after the Austrian physicist Christian Doppler who first proposed it in 1842, is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source.
• Spectroscope or Spectograph gathers light from the object and then passes it through a prism to separate the colors.
• In a series of spectroscopic observation of light from a star a shift in the color bands of the spectrum may be seen.
• The lines of the spectra of a distant star is shifted to the red end of the spectrum (redshift)