Astronomy is the science or study of objects beyond the earth’s atmosphere. In Astronomy, we study stars, planets, asteroids, galaxies, black holes, space, etc. It is a very broad field with a lot to offer. The word comes from the Greek root “Astron” meaning star and “nomos” meaning arrangement or law. Together it means the law and order of the stars as astronomy began with the fascination towards the night sky.
Astronomy is a vast subject covering a range of fields with all of them further divided into multiple branches. Astronomy is mainly divided into Observational and Theoretical Astronomy which are both used in various further divisions within Astronomy.
Observational Astronomy
It is the use of telescopes, satellites, and other instruments to collect data about various objects and processes happening in space to increase our understanding and to derive useful results. Galileo Galilei is the founder of observational astronomy as he was the first man to ever look deep into space through a telescope which we now call the Galileo-scope. Since then the field has greatly advanced. Observational Astronomy can be divided into two categories:
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Optical Astronomy: deals with collecting data in visible light.
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Non-Optical Astronomy: deals with collecting data in x-rays, gamma-rays, radio, infrared, etc. Mainly data apart from the visible part of the electromagnetic spectrum.
Theoretical Astronomy
It is the use of models and analytical tools to uncover the nature of astronomical objects and events. Many scientists work year-round on many theoretical models to predict and verify existing believes in astronomy and also try to predict how various entities in space will behave in the future. When Einstein gave his famous theory of relativity he used theoretical models to conclude how every observer perceives objects around him differently.
Further divisions
These fields are interconnected. All the fields together help astronomers in understanding the vastness of space better.
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Cosmology: This field studies the universe as a whole mainly to understand how the universe was formed, how it is evolving, and how it might come to an end. Cosmologists answer questions like, was it the big ■■■■ or something else that formed the universe? And, will the universe contract back causing another big ■■■■?
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Planetary Astronomy: It deals with the study of how planetary systems are formed like our own solar system. It explores planets, moons, and asteroids, natural satellites, etc. which are all part of planetary systems. An astronomer working in this area will investigate the reasons that led to the formation of our solar system and how it is changing with time.
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Stellar Astronomy: It deals with the study of the sun and other stars, their birth, evolution, characteristics, atmosphere, dynamics, etc. In stellar astronomy, we study the life cycle of stars and predict the possible demise of these objects. A scientist working in this area may study old stars to understand how elements in the universe were formed and evolved. The oldest star ever discovered was the “Methuselah star,” formally called HD 140283. Its age was calculated to be 14.5 billion years which is older than the universe’s age thus raising questions whether the universe’s age is wrong or the star is younger.
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Solar physics: It deals with the study of the sun specifically, processes on its surface, its evolution, cycles, etc. Our sun is estimated to be 4.6 billion years old and is predicted to grow into a red giant expected to eat up our planet earth, during its expansion phase.
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Galactic Astronomy: It is the study of the Milky Way galaxy and everything that is a part of it. Studying stellar evolution, debris disks, chemical evolution and the massive black hole at the center provide useful insights into the dynamics of how our galaxy is transforming.
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Extra-Galactic Astronomy: It studies everything outside the Milky Way. Extragalactic astronomy allows scientists to study phenomena that can’t be studied at a galactic scale, like gravitational-waves.
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Astrobiology: It is the study of extraterrestrial life in the universe, its possibilities, origin, and detection. The Discovery of building blocks of life on other planets is the task Astro-biologists encounter. The discovery of the fact that glycine (an important building block of life and the simplest form of amino acid) might exist under harsh conditions in space is one of the many discoveries in this field. Studying galaxies best suited for life and how life may occur or can be supported across the universe is the job of an Astrobiologist. Scientists suspect that dwarf galaxies with heavy elements and calmer environments like the “Large Magellanic cloud” are promising areas in the universe to support life.
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Archeoastronomy: It deals with how ancient civilizations perceived, understood, and transferred the information observed from the sky e.g. the sun, moon, and stars into their cultures, religion, society, etc. Through the remains of the old civilizations, we can explore how astronomy played a role in their lives. The pyramids of Giza aligned with the stars in the Orion constellation indicate the importance of astronomy to the ancient minds.
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Astroecology: It is the study of the interaction of living organisms with space. It tries to uncover the prospects of life on other planets and celestial objects and how it may flourish. The discovery of the fact that Martian soil has fertility to some extent is one of the breakthroughs in Astro-ecology.
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Cosmoecology: It extends the borders of astrogeology to wide stretches across the universe hoping to understand more about the survival of life across the universe.
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Astrochemistry: It is the merger of chemistry and astronomy where we study molecular interactions, reactions, formations, etc. in space. The discovery and analyses of chemicals e.g. cyclopropenylidene on Titan (Saturn’s moon) comes under the realm of Astrochemistry.
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Astrophysics: It is the use of laws of physics to describe the nature, formation, and working of astronomical objects. Studying the physical explanations behind systems e.g. the creation of elements in the universe through nuclear reactions in stars comes under astrophysics.
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High Energy Astrophysics: It is the study of high energy events related to stars, black holes, neutron stars lying at the high end of the electromagnetic spectrum. These events include supernovae, gamma-ray bursts, mergers, etc.
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Spectroscopy: It is the study or we can say a tool used in astronomy to understand how matter interacts with electromagnetic radiation based on the wavelength characteristics of that radiation. Studying the structure, composition, and temperature of stars is made possible through studying the spectral lines coming from those stars.
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Photometry: It is the study of flux or intensity of light arriving from astronomical entities to study those entities and to understand their internal mechanisms. Brightness, luminosity, and distances of stars can be found by employing photometric techniques.
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Astroseismology: It mainly focuses on studying stellar oscillations which affect different parts of the star differently helping to resolve its internal structure better.
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Helioseismology: It is like Astroseismology but it focuses only on the sun. Periodic oscillations on the sun’s surface are very diverse and help scientists study the inside of the sun and its dynamics.
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Helio-physics: It deals with the sun and its effects on all the other bodies in the solar system. Sun takes up 99% of the mass in the solar system and is the closest star to earth thus it is an ideal lab to explore stellar properties and how they set systems like our solar system.
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Astrometry: It is the study of measurements of the positions and the calculation of movements of celestial objects like the stars, planets, etc**.** A researcher working in this field might have the task of tracking positions, movements, and distances of asteroids and comets to prevent collision with earth. Apart from that understanding, the location of objects helps in understanding how the universe is working.
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Exoplanetology: It is the study and exploration of exoplanets which are planets outside the solar system. A scientist working on exoplanets will use techniques like the transit method to detect and study a star as it crosses its parent star, dimming the star and making it possible for us to study it.
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Astrogeology: It is concerned with the geological aspects of the celestial bodies. An Astrogeologist might be working on a task like the volcanic activity on Io (Jupiter’s moon) and its rule on the geological development of the surface of Io.
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Selenography: It is concerned with the mapping of the moon’s surface. Studying its craters, mountain ranges, poles, etc. helps scientists understand its topology and will help in building future labs on the surface.
Astrology vs. Astronomy
Astronomy is the science of the objects, systems, and processes outside the earth’s atmosphere while astrology is more towards the non-scientific explanations about how every human being has a birth star and how it affects your life and future. Astronomy is extremely different from astrology so to treat them as one is a huge mistake. Astrologers can predict your future and help you lead a life that suits your purpose but Astronomy uncovers the cosmos and helps a man look beyond what is visible through thinking, research, teamwork, and experimentation.