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harbinger | noun
har·bin·ger | \ˈhär-bən-jər\
1. one that initiates a major change: a person or thing that originates or helps open up a new activity, method, or technology; pioneer.
2. something that foreshadows a future event : something that gives an anticipatory sign of what is to come.
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Studying galaxies helps us understand the universe’s history, structure and evolution, opening us up to an extraordinary space that we often overlook in our daily lives.
Such knowledge is fundamental to understanding the universe, our place within it and the possibilities it holds. It could even help us identify habitable planets and environments where life could exist.
What is a galaxy?
A galaxy, sometimes called a star universe, is a group of billions of stars, with gas, dust and dark matter. The exact number of galaxies in the universe is not known, but current estimates suggest there could be around 100–200bn galaxies.
There are three basic types of galaxies: spiral, elliptical and irregular. Each galaxy has its own unique characteristics and history. The planet we live on and our solar system is called the Milky Way, which is estimated to be around 13.6 bn years old.
Edwin Hubble
The concept of galaxies as separate entities beyond our own Milky Way was first proposed by American astronomer Edwin Hubble in the 1920s. He also played a significant role in defining and classifying galaxies.
One of his key contributions was the use of Cepheid variable stars as distance indicators to make reliable measurements of large cosmic distances. By observing these stars in spiral nebulae (now known as galaxies), he was able to determine that they were much farther away than previously thought, establishing that they were separate entities outside of the Milky Way.
The Milky Way
The galaxy we live in is called the Milky Way because it appears as a milky band of light in the sky when seen in a really dark area. According to NASA, it is very difficult to count the number of stars in the Milky Way from our position inside the galaxy, but the best estimates tell us that it is made up of approximately 100bn stars.
The Milky Way galaxy spans about 100,000 light years across. At first, this may seem huge! Until we start comparing it to other galaxies. Our neighbouring Andromeda galaxy, for example, is some 220,000 light years across – more than twice as large as the Milky Way.
Other galaxies
The farthest galaxies from the earth, seen by us as only a few very faint red specks, appeared more than 13bn years ago, roughly 650mn years after the Big Bang. Soon, the James Webb Space Telescope will ensure completely new discoveries in our universe, tracing the formation and evolution of the very first galaxies.
We cannot actually see much of our own galaxy – even with a telescope. According to a study by Yale University, only 9,096 stars are visible to the naked human eye on a dark night. Without telescopes, we can only see three other galaxies; from the northern hemisphere we can see Andromeda, from the southern hemisphere, the Large and Small Magellanic Clouds.
16 year-old Sama is a passionate journalism student learning under the partnership of The Oxford School for the Future of Journalism and LEARN Afghan with aims to pursue a future career within the field while motivating other girls towards their dreams.
Sama is interested in science and journalism, and enjoys sharing her knowledge with Harbingers’ audience. She dreams of one day being a businesswoman or a doctor.
Sama speaks Dari and English.
Due to security concerns the authors image and surname have been omitted
Written by teenagers for teenagers, delivered every Friday afternoon to your inbox, with what’s best from the world’s youngest newsroom and its publisher, the Oxford School for the Future of Journalism
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