Beyond the solar system: Have a tour to our known universe.

Astronomers, astrophysicists, and scientists have done tremendous work in space observation. Different space telescopes and observatories made scientists perform more proactive studies on exoplanets and other objects beyond the solar systems of the universe.

NASA’s Kepler Space Telescope, since its launching on 7th march 2009 has discovered thousands of objects beyond solar systems. NASA’s Hubble Space Telescope(launched on 24th April 1990) and Spitzer Space Telescope (launched in 2003 and ceased to work on 30th January 2020) contributed a lot to the purpose.

The expanding universe is vast and infinite and whatever new things are discovered by astronomers and researchers about the universe are encouraging but a long way to go. However, all the discoveries beyond the solar system are amazing, interesting, and fascinating for the inquisitive. Let us discuss the celestial bodies and elements beyond the solar system in a precise manner.

Dark matter and dark energy

Normal matter is visible due to the presence of charged particles like electrons and protons. Activities like reflection, refraction, absorption, etc are integral parts of visible matter. But dark matter is a celestial body and a property of the Universe & occupies space. It is an invisible and dense body other than known matter. It is composed of particles that don’t absorb, reflect or emit light but light can pass through it. Unlike other known matter, it can’t be detected by electromagnetic radiation or touched. Scientists assume that dark matter consists of WIMPS (Weakly Interacting Massive Particles ).

The strange matter has gravitational force, which keeps the stars and galaxies together in the universe. It is presumed that about 26.8 % of dark matter constitutes the universe, whereas normal matter’s contribution is about 4.9 % and dark energy constitutes the rest 68.3 %. Albert Einstein was the first on Earth to observe that empty space in the universe is not empty. It has some energy and the energy is the property of space, which is believed to be expanding the Universe.

The universe originated 13.4 billion years back out of nothing for an unknown reason, infinitely beginning with smaller than an atom and it expanded infinitely within a few seconds, this unusual event is a BIG BANG. At the advent of the Universe, Cosmic Microwave Background (CMB) radiation was also created and is present till now.

In the earliest, the entire Universe was filled with hot clouds of normal matters and dark matters. In due course of time normal matter settle down in stars, planets, satellites, comets, asteroids, etc. Dark matter was created, with the creation of the universe left unattended due to its unknown characteristics. It is scattered unevenly throughout the Universe without being detected till Zwicky’s discovery. Dark matter has gravitational force and mass but is not affected by temperature and pressure although light can pass through it.

Galaxies:

Galaxies are bigger collections of gas, dust, and stars, and their planetary systems, are held together by gravity, dark matter, and the dark energy of the universe. Every galaxy has some shape like a spiral, elliptical and irregular, etc. Smaller galaxies may host a few hundred million stars, whereas the largest galaxies contain up to one hundred trillion stars. Astronomers and researchers have estimated very huge numbers, such as two trillion galaxies in our known universe. The galaxies have been classified on the basis of their shapes captured in telescopes and observatories, such as-

• Spiral galaxies: The spiral galaxies look like flat disk shapes of rotating stars, gas, and dust. Such types of galaxies were first described in detail by Edwin Hubble in 1936. Further, the spiral galaxies are divided into a normal spiral and barred spiral groups. In the case of normal spirals, the arms appear to emanate from the nucleus whereas in barred spiral contains a bright linear structure known as a bar that straddles the nucleus. Almost all spiral galaxy’s centers of their bulge host a supermassive black hole. Researchers estimated that spiral galaxies are formed about 1.4 billion years after the Big Bang in our universe. Some examples of these types of galaxies are our own galaxy milky way, M 74/NGC 628, and neighbor Andromeda galaxy.

• Elliptical galaxies: Elliptical galaxies appear like large spherical or elliptical patterns of stars and some are cigar-shaped. They have little gas and dust consisting of low-mass old red stars, having no nucleus or bulge at the center. It is not clear how they are formed, however, scientists believe that they have been formed due to galactic collisions. Further, it was apprehended that they were once spiral and reduced to such forms. At the center of the galaxy, it appears very bright and gradually fades to the outer edges of galaxies. Example-K87, Hercules A, ESO 325-G004, etc.

• Peculiar galaxies: Peculiar galaxies have no specific shape or composition and are formed due to collisions of two or more galaxies as suggested by scientists. Such types of galaxies have a more active nucleus at the center which signals the presence of massive black holes in the centers. They are two types, including interacting and active galactic nuclei (AGN). Example-ESO 162-17.
• Irregular galaxies: The galaxies which are not coming under any of the above categories are called irregular galaxies. They are small and dwarfs contain fewer stars in comparison to other galaxies having no nuclear or bulge at the center. Mostly contain hydrogen gas and scientists thought they were once spiral or elliptical and not classified in the Hubble classification system. May be formed due to the collision of galaxies. Many of these galaxies are satellites or companions to larger galaxies. Example- Large Magellanic cloud, the satellite galaxy of the milky way.

Black holes:

A black hole is a mystery in our universe.” A black hole is an area of such immense gravity that nothing-not even light can escape from it,” says NASA. Further, it can be defined that, a black hole is a cosmic or celestial body of very strong gravity, from which no matter even electromagnetic radiation can escape and it emits no light.

Astronomers and scientists believe that black holes are formed at the death of massive stars. When the fuels of the stars are exhausted, the binding energy of stars disappears causing the collapse of the mass itself, which gives rise to a huge explosion and is compressed into a very small dark body compare to its original shape.

A black hole with a mass, ten times more than Sun, then its radius would be 30km or 18.6 miles, the astronomers say. A large black hole can have tens to millions of times the mass of the Sun, compressed to a very smaller one. Only the stars having more than three solar masses (one solar mass is equivalent to 1.989 x 10³⁰ kilograms) become black holes at their death.

The circular surface of the black hole is known as the “event horizon “and the center of the event horizon is called “singularity.” The radius of the event horizon is known as the Schwarzschild radius, after the German astronomer Karl Schwarzschild. Schwarzschild in the year 1916, predicted the existence of collapsed stellar bodies, which did not emit light.

The length of the Schwarzschild radius is proportional to the mass of the dead star. Every black hole has an accretion disk, a disk-like flow of gas, plasma, and dust particles around the event horizon, and a relativistic jet.(Stream of magnetized plasma produced by a black hole)

The black holes are unlikely to observe directly due to their smaller size and characteristics of not emitting radiation. However, they can be observed by the effect of their gravitational fields on nearby objects. When a solar mass comes within the purview of the gravitational field of a black hole, it runs so fast into the event horizon of the black hole that it radiates X-rays before disappearing forever.

Black holes are ice-cold inside, but incredibly hot just outside. On the basis of their nature and physical properties, scholars have classified black holes into four categories, such as stellar, nonstellar, supermassive, and intermediate-mass black holes.

White holes:

A white hole is a theoretical phenomenon, in the universe in view of the general theory of relativity proposed by Einstein. It is viewed as the opposite characteristic of a black hole. As black hole exists scientists have imagined the existence of a white hole in the known universe but have not been observed to date.

Stephen Hawking and others have proposed that like supermassive black holes white holes exist and have properties like mass, charge, and angular momentum. A ring of gas and dust may be there around the event horizon. They attract matters however the matters attracted towards white holes would never reach the event horizon of white holes.

However, objects from white holes and energy can come out and visit the universe. As per the quantum mechanism black holes are opposite to white holes. But how it is formed is not clear. The existence of white holes is further strengthened by Russian cosmologist Igor Novikov in 1964. He proposed that a black hole links to a white hole that exists earlier.

Wormholes:

In our universe, a wormhole is a theoretical concept, which connects two distant points in space or time. Einstein’s theory of general relativity is connected with the concept of a wormhole. It is a type of connectivity that reduces the distances between two points substantially.

However, till now it is a hypothetical realm. Wormholes are the legitimate solution to the theory of relativity but scientists are still at dark, regarding the physical presence of the same in real space.

The wormhole solution was proposed by Albert Einstein and Nathan Rosen in 1935 for which wormholes are sometimes referred to as “Einstein-Rosen bridge”. They proposed that as a black hole has an event horizon and singularity, a hypothetical white hole has also singularity and event horizon but both works differently.

Further, they found theoretically that, every black hole is paired with one white hole because two holes would exist in separate places in space and a wormhole is an underground connectivity that joins both. But so far the characteristics of the black hole and white holes are concerned this hypothesis is likely to be failed.

Another point is that suppose a single photon or particle of light, that passes through the wormhole would provide so much energy to the system that would destroy the wormhole channel, as per European Southern Observatory. The only thing which can stabilize the “Einstein-Rosen bridge” is negative mass, which is not yet found. Scientists believe that wormholes might occur naturally at the microscopic level in quantum form but not like connecting tunnels.

Neutron stars:

Neutron stars are formed when giant stars die in a supernova causing the protons and electrons to melt together to form neutrons in our universe. They are stellar objects of dense mass, about 1.4 times of our Sun.

As per space.com, one teaspoon of neutron star would weigh a billion tons. They can spin as fast as 43,000 times per minute and gradually slow down over the period. The gravity of the neutron stars is also very strong, which is estimated to be 2 billion times stronger than the gravity of our earth on average.

They are incredibly hot when formed and have a surface temperature may be around 6,00,000K and magnetic fields are between 108 and 1015 times stronger than earth’s magnetic field. They are the smallest and densest among the known stellar objects.

Some neutron stars emit beams of electromagnetic radiation. Jocelyn Bell Burnell and Antony Hewish in 1967 proved that neutron stars exist in the true sense. Hubble Space Telescope detected Rx -J185635-3754, the first neutron star in 1990. Furthermore, such stars have been detected which were emitting radiations.

White dwarf:

A white dwarf is considered a dead star, in the universe, as all the fuel inside the object is exhausted leaving zero nuclear fusion and shedding its outer layer. But the objects still shine due to their inherited high temperature but gradually they will cool down to vanish from sight. White dwarfs are important for scientific research, as their structure and composition contain the records of the final stages of stellar evolution.

When a star dies it leaves some remnant, which becomes a white dwarf, neutron star, or black hole depending on the mass of the star. White dwarf once was the core of the dead star of the universe.

During a star’s lifetime, nuclear fusion goes on to the core causing the core temperature extremely high, (which may be as extreme as 100 million degrees in the case of helium and 15 million degrees in the case of hydrogen). For when a star of low mass dies shedding its outer layer and leaving its core as a white dwarf, it remains hot at around a 100million degrees.

The name “white dwarf” was coined by Willem Luyten in 1922. White dwarfs are said to be the end product of the evolutionary process. The mass of the star is not enough to become a neutron star or black hole. When a white dwarf is there we may think about a black dwarf, however, no such object has been identified to date. The nearest known white dwarf-Sirius B is at 8.611 light years away, being the smallest component of the Sirius binary star.

Nebula:

In Latin nebula means cloud. On earlier occasions when astronomers look at the sky through early telescopes found many indistinct, irregular clouds called a nebula. A nebula is a giant cloud of dust and gas (hydrogen and helium) in space, normally tens to hundreds of light years across. A nebula is one of the constituents of the galaxy in the universe.

Some nebulas are formed due to the explosion of dying stars. Other nebulas are referred to as “star nurseries” as new stars begin to groom in the region. “Pillar of creation” in the Eagle Nebula is a bright example of such a region. Some nebulas are visible to the earth to the naked eye.

The term nebula was originally used to describe and diffuse astronomical objects including galaxies beyond the milky way. A nebula appears where the interstellar medium has become so dense enough to form clouds. Nebulas are classified on the basis of their physical properties; such as

• Emission nebula; They emit their own light and stars are formed in this region. Example-Orion nebula
• Reflection nebula; Reflects light from nearby stars and the stars are not powerful enough to ionize the nebula’s gas.
• Planetary nebula; As resembles, planets earn the name. Example-Helix nebula
• Supernova remnants; Consist of remnants of stars that exploded in a supernova. Example- Crab nebula
• Absorptive nebulae; Also referred to as black nebulas are clouds of dust and gas, that don’t emit or reflect light further, however, block light coming from behind.

Conclusion:

Our known universe is so vast that we can’t imagine its actual size and how much space is filled with stellar objects and cosmic elements. Whatever is achieved in space discoveries by our researchers and scientists is minimal but commendable. New things are coming up to the limelight as a result of the consistent hard work of researchers and scientists.

The nebulas are the region where new stars are formed and white dwarfs are the end products of the stars The universe is expanding and unlimited like our unlimited mind. The known elements beyond the solar systems have been discussed here in a precise manner for a better understanding of the inquisitive.