Kate, an eight year old Indian girl, attended school in Texas. She lived with her parents and her older sister Sam. Her father was a  cosmologist. Kate had always admired her father's work and aspired to follow in his footsteps by one day  becoming a cosmologist herself.

Kate's school held a 2nd grade Science Fair every year. She was determined to make her effort the best because the first-place winner received tickets to the Space Center Houston. She wanted to win because she was a fierce competitor, she wanted her parents to be proud of her because her sister Sam always won every competition she entered, and she wanted to impress her friends too. Kate decided to do her research on the universe because she was familiar with the subject and her father is a cosmologist who could assist her.

Kate had a dilemma. Since the universe was so broad, which topic within the universe was she going to do her project on. Kate thought about what topic to do,  black holes, galaxies, dark matter, formation and ending of the universe, the whole day at school, her friends and teacher noticed she was distracted. On her way home she told her father her dilemma and her father found an easy solution to her problem. He advised her to conduct a review/tour of the universe, which would cover all of the things she had in mind.

Kate got right to work as soon as she arrived home. She started by jotting down what she previously knew about the universe. She opted to do her assignment in the form of a book only pointing out key topics of the universe. She'd have summaries of each topic, and she'd be on hand to clarify anything further.

She began by stating that cosmologists believe the universe began roughly 13.8 billion years ago and with the notion of The Big Bang. The Big Bang theory, which asserts that the universe and everything it contains arose from an incredibly hot single point that "exploded," is the most widely accepted idea on how the universe began. Technically, the universe did not explode, but rather expanded, and it continues to do so right now. There were galaxies within seconds of there being nothing but space. The universe was so hot after the Big Bang that no particle could form because the heat prevented it. Thousands of years later, atoms like hydrogen and helium began to develop and enter the universe. Protostars, the first stars, formed 400 million years after the Big Bang. Protostars are gas clouds that comprise 75% hydrogen, 25% helium, and dust and are thought to grow into stars. Protostars will eventually undergo nuclear fusion in their centers and begin to shine. The solar system was formed by clouds of gas and dust about 9 billion years after the Big Bang.

Galaxies are collections of gas, dust, trillions of stars, and dark matter held by gravity. Atoms collide to make stars and stars collide to make galaxies. Galaxies are divided into three types: elliptical, spiral, and irregular galaxies.

An elliptical galaxy is one with a smooth, nearly featureless image. In contrast to flat, spiral galaxies with organization and structure, elliptical galaxies are more 3D and lack structure almost looking like ovals. Their stars orbit the center in somewhat random orbits. Elliptical galaxies are mostly made up of old stars, with little hot gas and dust. Elliptical galaxies come in a variety of sizes. When two galaxies collide they form an elliptical galaxy. Elliptical galaxies can contain up to a trillions of stars making them abundant and longer than the others. There are the more common galaxies, 75% of galaxies are elliptical. Ellipticals are classified by how elliptical they are. Stars in elliptical galaxies orbit in many different directions, maintaining the elliptical shape. An elliptical galaxy can be a dwarf galaxy or a giant galaxy.

Spiral Galaxies are spiral or disk-shaped galaxies. The bulge is a bulging center in spiral galaxies. The bulge contains old stars. The galaxy is referred to as a "face-on spiral" if the spiral shape can be clearly seen.  Some spiral galaxies have a bright line or bar running through them. These are known as barred spiral galaxies. The Milky Way, the galaxy in which we live, is a spiral galaxy. About 20% of galaxies are spiral and they appear the brightest galaxies in the universe. Spirals are classified by how bright the central bulge is and how tightly wound the arms are. Spiral galaxies have a  forming in spiral galaxies. 

Irregular galaxies share few characteristics. Many are the result of galaxy collisions or close calls. Irregular galaxies are most commonly found in groups or clusters.  Astronomers are confused as to why a few irregular galaxies appear so strange. Galaxies that are neither type are called irregular galaxies. Approximately 5% of galaxies are irregular.

A black hole is an area of space in which neither matter nor light can evade gravity's attraction. The singularity of a black hole is the moment at which all matter has condensed to one point. It's a bottomless, infinitely dense well in the fabric of spacetime. If a neutron star's mass exceeds 3 million Suns, it will collapse into a black hole. A Type II supernova (if massive enough) or accretion by a neutron star in a binary system can both produce black holes. A black hole's escape velocity is larger than the speed of light, therefore not even light can escape its gravitational pull. 

The gravitational effects of black holes are what lead to their discovery.

Black holes are mysterious, invisible objects that gobble up stars, planets, and even galaxies are points in space where gravity is so strong that it sucks in everything including light. A black hole is everything but an empty hole. It is an area that packs a huge amount of material , or mass, into a very small space, creating an unbelievably dense object. Black holes form when a huge star burns out, it is squeezed so tightly by its own gravity that all of its matter is crushed into a tiny point before it vanishes. Black holes are considered to be the last evolutionary stage of a star. The first black hole to be discovered was Cygnus X-1. 

Despite the fact that astronomers have learnt a lot about the universe, issues such as dark matter and dark energy still exist. Atoms make up matter, which takes up space and has mass. Everything in the universe is made out of matter. Dark matter, an extra source of gravity that does not produce light, must exist. Dark matter makes up the majority of a spiral galaxy's mass, accounting for around 95% of its total mass. Dark matter is distributed throughout the galaxy in a massive dark matter halo. Elliptical galaxies are also dominated by dark matter. Dark matter is both chilly and massive. It isn't visible or palpable. Dark matter makes up around 27%.Normal matter, such as protons, electrons, atoms, and molecules, interacts with it only very weakly.