Courses
Courses for Kids
Free study material
Offline Centres
More
Store Icon
Store

Cosmology Astronomy

Reviewed by:
ffImage
hightlight icon
highlight icon
highlight icon
share icon
copy icon
SearchIcon

Introduction to Astronomy and Cosmology

Astronomy is derived from the Greek word ‘ἀστρονομία’, where ἀστρον or Astron means ‘star’ and νομία or nomia from νόμος (nomia), which literally means the law or culture of stars.

It is a science that studies the laws of the stars, i.e., everything outside the Earth’s atmosphere.

Cosmology is derived from the Greek word κόσμος, where kosmos mean "world" and -λογία, or -logia means "study of").

For studying the science behind the origination and development of the universe, we use the term ‘cosmology’. However, cosmology is a branch of astronomy that studies the Universe as a whole.


Cosmology Astronomy 

This page will provide the introduction to astronomy and cosmology, cosmology astronomy, basic astronomy and cosmology, astronomy astrophysics cosmology, and extragalactic astronomy and cosmology in detail.

Now, let’s understand astronomy and cosmology in detail:

Cosmology 

In 1656, the term cosmology was first employed in an English dictionary named Thomas Blount's Glossographia.

In the year 1731, the term ‘cosmology’ was carried to in Latin by a German philosopher named Christian Wolff, in Cosmologia Generalis.

Cosmology is focused on studying the origin and evolution of the universe, from the Big Bang to today and on into the future. It applies a scientific approach to study the origin, evolution, and eventual dismissal of the universe. 

One of the types of cosmology is Physical cosmology. It is the scientific study of the origin of the universe, its large-scale structures and dynamics, and its ultimate dismissal, as well as the laws of science that govern the areas mentioned above.


Astronomy

All the celestial objects residing in space have their significance and to study these, we use the term ‘astronomy’.We use astronomy word as terminology to study the science of celestial objects, space, and the physical universe. 

It is one of the oldest natural sciences that studies celestial objects and their processes. The objects may include all the planets, moons, stars, galaxies, nebulae, and comets. 

Astronomy uses mathematics, physics, and chemistry to explain their origin and evolution.

Astronomy allows astronomers to study various ongoing spatial phenomena, and these are as follows:

Supernova explosions, 

Gamma-ray bursts, 

Quasars, 

Blazars, 

Pulsars, and 

Cosmic microwave background radiation. More specifically, astronomy studies everything that originates outside the Earth's region.

However, cosmology is a term that takes into account the theory behind the building of the universe and modern cosmology is the next step after the Big Bang Theory.


Astrophysics Astronomy Cosmology

The ancient period recorded history made methodical observations of the dark sky; these include the following:

  • Babylonians

  • Greeks

  • Indians

  • Chinese

  • Egyptians

Maya, and many more ancient diligent Americans.

In the ancient period, astronomy involved various disciplines like celestial navigation, astrometry, observational astronomy, and the preparation of calendars. Nowadays, professional astronomy is said to be akin to astrophysics.

Professional astronomy is divided into two branches, viz: observational and theoretical. 

Observational astronomy focuses primarily on gathering data by observing astronomical or celestial objects and this data is then analyzed by using basic astronomy and cosmology principles of Physics. 

However, theoretical astronomy is centred on the development of computer or analytical models to study and describe astronomical objects and their phenomena. These two fields complement each other. This part tries to explain observational results and observations are used to affirm our theoretical results.

So, basic astronomy and cosmology talk about the things mentioned above. 


Astrophysics Astronomy Cosmology

“Astrophysics" and "Astronomy" are synonyms to each other. According to the dictionary definitions, "astrophysics" refers to the branch of astronomy that deals with "the behaviour, physical properties, and dynamic processes of celestial objects and phenomena, while "astronomy" is "the study of all the around the Earth's region and the study of their physical and chemical properties using Physics, Chemistry, and Mathematics. 


Extragalactic Astronomy and Cosmology

Extragalactic Astronomy and Cosmology is a book written by Peter Schneider. This book is very useful for Aeronautical Engineering students and also for those who have an interest in developing their knowledge in the field of Spacecraft and Space Engineering.


Observational Astronomy

Visible light is the main source of information about celestial bodies and their processes, or more specifically the electromagnetic radiation. 

Observational astronomy can be subdivided into fields according to the corresponding region of the electromagnetic spectrum on which the observations are made. We can observe a few parts of the spectrum from the Earth's surface, while other parts are observable from either great heights or outside the Earth's atmosphere. 

Specific information on the subfields of observational astronomy is given below.

Following are the types of observational astronomy:

  • Observational astronomy

  • X-ray astronomy

  • Radio astronomy

  • Infrared astronomy

  • Optical astronomy

One of the historical methods of astronomy is optical astronomy; let’s understand it in detail:

Historically, optical astronomy is also known as visible light astronomy. We call it one of the oldest forms of astronomy. Images of observations were initially drawn by hand; however, in the late 19th century and most of the 20th century, images were prepared using photographic equipment. 

At present, the images are made by using digital detectors, particularly charge-coupled devices or CCDs, and then recorded on modern mediums. Though visible light extends from approximately 400 nm to 700 nm, we can use the same equipment to observe some near-ultraviolet and near-infrared emissions.

FAQs on Cosmology Astronomy

1. What is the main difference between astronomy and cosmology?

The primary difference lies in their scope. Astronomy is the broad science that studies celestial objects such as stars, planets, and galaxies, including their positions, compositions, and movements. Cosmology, on the other hand, is a specialised branch of astronomy that focuses on the universe as a whole—its origin, evolution, large-scale structure, and ultimate fate. In short, astronomy studies the individual 'trees', while cosmology studies the entire 'forest'.

2. What fundamental questions does cosmology seek to answer?

Cosmology addresses some of the most profound questions about our existence. It investigates the origin of the universe through the Big Bang theory, explains its ongoing expansion, and explores the nature of its dominant but unseen components like dark matter and dark energy. It also studies the formation of large-scale structures, such as galaxy clusters, to understand the universe's past and predict its future.

3. What are the key branches of observational astronomy?

Observational astronomy is categorised by the portion of the electromagnetic spectrum used to view celestial objects. The main branches are:

  • Optical Astronomy: Uses visible light to study stars, planets, and galaxies, which is the oldest form of astronomy.
  • Radio Astronomy: Detects radio waves to observe phenomena like pulsars, quasars, and the cosmic microwave background radiation left over from the Big Bang.
  • Infrared Astronomy: Observes infrared radiation to penetrate cosmic dust clouds, studying star formation and the centres of galaxies.
  • High-Energy Astronomy: Uses space-based telescopes to detect UV, X-rays, and gamma rays from energetic events like supernovae, black holes, and neutron stars.

4. How does the Big Bang theory explain the origin and evolution of the universe?

The Big Bang theory is the leading scientific model describing how the universe began. It proposes that approximately 13.8 billion years ago, the entire universe was an infinitesimally small, extremely hot, and dense point. This point began to expand and cool rapidly. In the first moments, fundamental particles formed, which later combined to create atoms (mostly hydrogen and helium). Over billions of years, gravity pulled these atoms together to form stars, galaxies, and the vast cosmic structures we observe today. The ongoing expansion of the universe is a key piece of evidence supporting this theory.

5. What is the importance of studying extragalactic astronomy?

Extragalactic astronomy, the study of objects outside our Milky Way galaxy, is crucial for understanding the universe's scale and our place within it. By observing other galaxies, we can:

  • Test and refine models of galaxy formation and evolution.
  • Map the large-scale structure of the universe and how galaxies cluster together.
  • Study extreme phenomena like supermassive black holes and galaxy mergers that are not occurring in our own galaxy.
  • Measure the expansion of the universe more accurately by observing distant galaxies.

6. Why is looking at distant celestial objects equivalent to looking back in time?

This phenomenon occurs because light travels at a finite speed (approximately 299,792 km/s). When we observe a galaxy that is 10 million light-years away, we are seeing the light that left that galaxy 10 million years ago. The image we capture is not how the galaxy appears today, but how it appeared in the distant past. This makes powerful telescopes like the James Webb Space Telescope function as 'time machines', allowing astronomers to study the early universe and see how the first stars and galaxies formed.

7. What are dark matter and dark energy, and why are they crucial in cosmology?

Dark matter and dark energy are mysterious components that constitute about 95% of the universe.

  • Dark Matter: This is an invisible substance whose presence is inferred from its gravitational pull on visible matter. It doesn't emit or reflect light. It acts as the cosmic 'glue' that provides the extra mass needed to hold galaxies and galaxy clusters together.
  • Dark Energy: This is a hypothetical form of energy that acts as a repulsive force, counteracting gravity. It is believed to be the driving force behind the accelerated expansion of the universe. Understanding these two components is the biggest challenge in modern cosmology.

8. How do astronomers measure the vast distances to stars and galaxies?

Astronomers use a technique called the cosmic distance ladder, which involves several methods for different distance scales. For nearby stars, they use stellar parallax—the apparent shift in a star's position as Earth orbits the Sun. For more distant objects, they rely on 'standard candles,' which are objects with a known intrinsic brightness. By comparing this known brightness to how bright the object appears from Earth, they can calculate its distance. Key standard candles include Cepheid variable stars and Type Ia supernovae.