Other Celestial Bodies in Space

Last Updated on 09/08/2020 by FilipiKnow

Given the vastness of the universe, it is no surprise to find that we have other celestial neighbors aside from other planets. 

Go back to the main page: The Ultimate UPCAT Reviewer (w/ Free Practice Tests and Answer Keys)


1. Stars.

Stars are considered as the building blocks of galaxies. Without stars, elements that are essential to the formation of life would not exist.

Much like the formation of the Sun, stars form from interstellar clouds of dust and gas that condense due to gravitational pull.

Nuclear fusion is the driving force behind the life of a star. At the very core of a star, hydrogen undergoes nuclear fusion to form helium, producing an outflow of energy that keeps a star from collapsing under its own weight.

A star nears the end of its life when it exhausts its fuel supply, leading to collapse and then a spectacular explosion in the form of a supernova. The materials produced by a supernova may be reused again in the formation of another star, repeating the cycle.

Stars are classified according to the relationship between their absolute luminosities or magnitudes and temperatures in a diagram called the Hertzsprung-Russell diagram (HR diagram). Depending on the star, it may be plotted along the middle diagonal line called the Main Sequence or fall above it (giants and supergiants) or below it (white dwarfs).

As mentioned in the previous chapter, our Sun falls on the Main Sequence and is classified as a Yellow Dwarf.

astronomy reviewer 26
Hertzsprung-Russell Diagram. Credit: ESO/Creative Commons

2. Comets.

astronomy reviewer 27
Image of Comet NEAT captured by the Kitt Peak National Observatory in Arizona. Credit: NASA

Comets are small space bodies composed of dust, ice, and frozen gases. When comets come close to the Sun, it starts to heat up and releases gas through a process called outgassing, leaving long trails of gas and dust as it moves.

Comets have different orbital periods (the time it takes for a comet to complete one orbit around the Sun). Some famous comets are Halley’s Comet (76-year orbital period), Comet Hale-Bopp (2,533-year orbital period), and Comet Hyakutake (113,782-year orbital period).


3. Asteroids.

astronomy reviewer 28
Image of the asteroid Ida taken by NASA’s Galileo spacecraft. Credit: NASA/JPL-Caltech

These are small rocky bodies (planetesimals) that are left-overs from the formation of the Solar System. Most asteroids in the solar system can be found in a region called the asteroid belt. They are irregularly shaped and greatly vary in diameter. 

When located in space, they are called asteroids (when more than one meter in diameter) or meteoroids (when less than a meter in diameter). When it enters the Earth’s atmosphere, it becomes a meteor. If it reaches the Earth’s surface, it is then called a meteorite.


4. Galaxies.

astronomy reviewer 29
The different types of galaxies. Credit: A. Feild/STScI

Galaxies are large clusters of stars, solar systems, gas, and dust held together by gravity. Using the Hubble Space Telescope, astronomers estimate that there may be 100 billion galaxies and probably more.

Galaxies are classified based on their morphology and are divided into three major categories: elliptical, spiral, and irregular galaxies. As mentioned in previous chapters, we live in the Milky Way galaxy, a spiral type galaxy. However, a lot of galaxies also appear in unusual forms, usually a combination of the main morphologies.

Galaxies tend to be bundled together in groups, clusters, and superclusters. For example, the Milky Way galaxy is part of the Local Group galaxy group which is part of the Virgo Supercluster, which is part of the even greater Laniakea Supercluster.


5. Blackholes.

astronomy reviewer 30
Image of a blackhole named Cygnus X-1 pulling in matter from its blue star neighbor. Credit: NASA/CXC/M.Weiss

A blackhole refers to a region in space where the force of gravity is strong enough that even light cannot escape.

This is the result of matter being compressed beyond a certain density. Blackholes are sometimes the result of extreme compression that happens when a star dies. Many galaxies are believed to contain massive blackholes at their centers.

The Milky Way’s very own massive blackhole is called the Sagittarius A* (pronounced as “Sag A star”).

Previous topic: The Motions of the Moon

Return to the main article: The Ultimate Astronomy Reviewer

Ruth Raganit

Ruth Raganit is an aspiring geologist who obtained her Bachelor of Science degree in Geology from the University of the Philippines – Diliman. Her love affair with Earth sciences began when she saw a pretty rock and wondered how it came to be. She also likes playing video games, doing digital art, and reading manga.

One thought on “Other Celestial Bodies in Space

  1. Pingback: Astronomy Reviewer for LET, UPCAT, and Entrance Exams

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Recent Content