The Guide to Space

We all have already leaned about our solar system, Meteoroids & Meteorites, Asteroids & Comets in our school. now we are learning about some more interesting things in the space  

Quick revision 

         Our solar system is the one we know the most about. The Sun is at its center. Our solar system includes everything that orbits or goes around the Sun. Planets, moons, asteroids; comets and dust are all part of the solar system. Our solar system lies near the edge of the Milky Way galaxy. The Milky Way is shaped like a whirlpool. All the stars in the galaxy, including our Sun, orbit around the center of the Milky Way. With the discovery of Pluto in 1930, astronomers considered the Solar System to have nine planets. Pluto was classified as the ninth planet and it remained so for 75 years but in 2006, International Astronomical Union classified Pluto as a ‘dwarf planet’ due to its smaller mass. In view of this, our solar system now consists of eight planets. Mercury, Venus, Earth and Mars are known as the inner planets, as they are nearest to the sun. They form a group of rocky planets. The outer planets are Jupiter, Saturn, Uranus and Neptune. 

The Kuiper Belt and Beyond 

The Kuiper Belt and Beyond The Kuiper Belt (also called the Kuiper-Edgeworth Belt) is a doughnut-shaped region that extends between about three to eight billion miles (5 to 12 billion km) out from the Sun (its inner edge is about at the orbit of Neptune, while its outer edge is about twice that diameter).

Kuiper Belt Objects (KBOs) are, as their name implies, objects that originate from or orbit in the Kuiper Belt. Pluto is the only one KBO which was known for more than 60 years. Many KBOs have been discovered since 1992, however, the current estimate is that there are millions, if not billions, of KBOs. KBOs are basically comets without tails: icy dirt-balls that have collected together over billions of years. If they get large enough, such as Pluto did, they evolve as other massive planet like bodies do, forming dense cores that have a different physical composition than the mantle or crust above it. Most short-period comets, those with relatively short orbital times of a few years to a few centuries are thought to originate from the Kuiper Belt. 

BLACK HOLE

 A Black Hole is an extremely dense celestial body that has been theorized to exist in the universe. The gravitational field of a black hole is so strong, that nothing including electromagnetic radiation can escape from its vicinity. It is surrounded by a spherical boundary called the horizon, through which light can enter but not escape, it therefore appears totally black. 

The black hole concept was developed by a German astronomer in 1961 on the basis of Einstein’s General Theory of Relativity. According to General Relativity, Gravitation severely modifies space and time near a black hole. In 1994, astronomers used the Hubble Telescope to uncover the first convincing evidence that black holes exist. 

Hubble’s Law

 In 1929, Edwin Hubble discovered that the galaxies are moving away from each other. He presented his finding in the form of a law which is known as Hubble’s law. Tracing the expansion of the universe backward in time bring us to imagine an initial high-density, high-temperature state commonly called the big bang. 

A rough estimate of the age of the universe based on the presently observed expansion rate is called the Hubble time. The cosmic microwave background radiation is blackbody radiation with a temperature of about 2.73 Kelvin, spread nearly uniformly over the entire sky. This radiation is the light from the big bang. The background radiation is clear evidence that the universe began with a big bang

The Big Bang Theory 

During the earliest moments of the universe, matter and antimatter particles continually flashed in and out of existence. A slight excess of ordinary matter remained after most of the matter and antimatter particles annihilated each other. During the first three minutes of the big bang, nuclear fusion converted some of the hydrogen into helium but was unable to make many other heavy atoms because no stable nuclei exist with weights of 5 or 8. Now, hydrogen and helium are common in the universe, but heavier atoms are rare. For a period of hundreds of millions of years called the Dark Age, the universe expanded in darkness until the first stars came into existence.

 Astronomers have observed signs of re-ionization of the universe caused by that first generation of stars. The chemical composition of the oldest stars is about 75 percent hydrogen and 25 percent helium, which is what models of the big bang nuclear processes would predict. This is a further evidence supporting the big bang theory

The Inflation Theory 

The inflationary theory, a modification to the big bang theory, proposes that the universe briefly expanded dramatically, just a tiny fraction of a second after the big bang. The energy to drive inflation would have been released when the four forces of nature changed their respective properties as the universe cooled in its earliest moments. This “separation” of forces is predicted by grand unified theories (GUTs) that explain the forces of nature as being aspects of a single force, unified in particle interactions with very high energies. 

Properties of Universe 

The universe is isotropic and homogeneous. In other words, in its major features, the universe looks the same in all directions and in all locations. Isotropy and homogeneity lead to the cosmological principle, the idea that there are no special places in the universe. Except for minor local differences, every place is the same, and the view from every place is the same. There are three models about the fate of the Universe.

 • Closed universe models are finite in size, but their space-time is curved back on itself so they have no edge or center. 

• Open universe models have curved space-time, but it is not curved back on itself. Such universes are infinite.

 • Flat universe models have uncurved space-time and are infinite. Modern observations show that the universe is probably flat. 

Dark Matter 

component that does not radiate in the electromagnetic spectrum and, therefore, is not detected by means of telescopes is known as dark matter. In the 1930s, astronomer Fritz Zwicky (1898–1974) noticed that, in the Coma cluster of galaxies, many of the individual galaxies were moving around so fast that there had to be a tremendous amount of gravitational pull toward the centre of the cluster; otherwise, the galaxies would literally hurl themselves out of the cluster. 

The amount of matter that needed to exist in the cluster to produce that much gravity far exceeded the amount of matter observed in all the galaxies in the cluster put together. This extra matter became known as “dark matter.”

 After decades of further study, dark matter has now been confirmed as an important constituent of matter around galaxies, in clusters of galaxies, and throughout the universe as a whole. According to the latest measurements, about 80 percent of the matter in the universe is dark matter. 

Dark Energy 

When Albert Einstein and others were working on the nature of the universe in the early twentieth century, Einstein introduced a mathematical term into his equations to keep a balance between cosmic expansion and gravitational attraction. This term became known as the “cosmological constant,” and seemed to represent an unseen energy that emanated from space itself. 

After Edwin Hubble and other astronomers showed that the universe was indeed expanding, the cosmological constant no longer appeared to be necessary, and so it was not seriously considered again for decades. Then, starting in the 1990s, a series of discoveries suggested that the “dark energy” represented by the cosmological constant does indeed exist.

 Current measurements indicate that the density of this dark energy throughout the universe is much greater than the density of matter—both luminous matter and dark matter combined. 

Space Plasma

The universe is made of up of space plasma. Plasma is the word given to the fourth state of matter (solid, liquid, gas, plasma). A plasma is a gas that is so hot that some or all its constituent atoms are split up into electrons and ions, which can move independently of each other. Because they are made up of electrically charged particles, plasmas can be strongly influenced by electrostatic and electromagnetic fields and forces, which can lead to very complex and interesting behaviour.

Plasmas are found throughout the Solar System and beyond: in the solar corona and solar wind, in the magnetospheres of the Earth and other planets, in tails of comets, in the inter-stellar and inter-galactic media and in the accretion disks around black holes. There are also plasmas here on Earth, ranging from the inside of a nuclear fusion reactor to a candle flame.

In the Space Plasma Physics Group, we study plasmas in the Earth's magnetosphere and the solar wind, and what happens when they interact.

Nebula 

A nebula is a giant cloud of dust and gas in space. Some nebulae (more than one nebula) come from the gas and dust thrown out by the explosion of a dying star, such as a supernova. Other nebulae are regions where new stars are beginning to form. For this reason, some nebulae are called "star nurseries."

Nebulae exist in the space between the stars—also known as interstellar space. The closest known nebula to Earth is called the Helix Nebula. It is the remnant of a dying star—possibly one like the Sun. It is approximately 700 light years away from Earth.