THE MILKY WAY AND VOYAGER

THE UNIVERSE
Scientists estimate there are about 10,000 stars for every grain of sand on Earth’s beaches. Astronomers calculate that the observable universe holds roughly 200 billion trillion stars (that’s a 2 followed by 23 zeros). In comparison, all the sand on every beach and desert on Earth adds up to around 7.5 quintillion grains (7.5 × 10¹⁸).
Why So Many Stars? The universe is vast. Our own galaxy, the Milky Way, has around 100–400 billion stars, and that’s just one galaxy among an estimated 2 trillion galaxies in the observable universe. Each galaxy carries billions or even trillions of stars.

THE MILKY WAY
When we look up at the night sky, every star visible to the naked eye belongs to our own galaxy, the Milky Way. Despite the galaxy containing hundreds of billions of stars spread across a vast spiral structure, our view is limited to only a tiny fraction of them, those relatively close to our solar system. The vast majority of stars remain far beyond our sight without telescopes. This means that when we gaze at the heavens, we are not seeing the whole galaxy but just a small local neighbourhood of stars, giving us only a glimpse of the true immensity of our galactic home.

Each galaxy holds billions of stars and trillions of worlds making Earth’s place in the cosmos unbelievably tiny. What seems like everything to us is, in truth, an almost invisible speck in a universe so immense that human imagination can barely scratch its surface. Every star you can see with the naked eye is within this yellow circle.

ANDROMEDA GALAXY
For those who say we can see the Andromeda Galaxy with the naked eye, it appears as a faint, blurry patch of light, not as distinct as stars like those in the Milky Way. You are NOT seeing individual resolved stars in Andromeda,
In about 4.5 billion years our Milky Way galaxy will collide and merge with the neighboring Andromeda Galaxy. Though galaxies seem vast and distant, gravity is slowly pulling these two giants together at incredible speeds. When they finally meet, stars, planets and cosmic clouds will be reshaped into a massive new “super galaxy”. Surprisingly the chances of individual stars colliding are very small, since galaxies are mostly empty space. Instead, their structures will stretch, twist and swirl in a spectacular cosmic dance that will last billions of years. The night sky of future Earth, if it still exists will be filled with breathtaking views of colliding star systems marking one of the most dramatic events in the history of the universe

THE SIZE OF THE MILKY WAY GALAXY
To answer this question, a spaceship moving at 100 percent of light speed across the Milky Way Galaxy which is huge, stretching 100,000 light-years across. Hence, it will take us 100,000 years to travel from one edge of the Milky Way Galaxy to another. Our home galaxy is packed with 100-400 billion twinkling stars, and probably just as many planets spinning around them, ranging from 800 billion up to 3.2 trillion.
At the center, a giant supermassive black hole called Sagittarius A* sits, as heavy as 4 million suns, swallowing anything nearby. Smaller black holes hide in the galaxy’s twisty arms. Even though it’s so wide, the Milky Way is super thin, only 1,000 light-years thick—like a cosmic pancake! So if we should travel through it’s thickness, it will take us only 1,000 light years to escape our home galaxy. The Milky Way is just one spiral galaxy, out of over 2 trillion galaxies that make up the observable Universe.
And even if we decide to get fly across it with our spaceship, we will never get to the end of Universe as our cosmos is expanding faster than the speed of light.
It takes our Sun 250 million years to orbit the Milky Way. Our solar system is located about 26,000 light-years away from the center of the galaxy.

RELATIVE SIZE OF THE MILKY WAY 

If the Sun were reduced to the size of a white blood cell the Milky Way would span the size of the continental United States. This comparison shows how immense our galaxy truly is stretching about 100,000 light-years across and containing hundreds of billions of stars. Despite the Sun being incredibly large compared to Earth it becomes almost insignificant on the galactic scale. This perspective emphasizes both the vastness of the Milky Way and the small place our solar system occupies within it. 

FORMATION OF ELEMENTS
Earth may be around 4.5 billion years old, but the story of its gold is far older. Gold, along with other heavy elements like platinum and uranium, was not created on Earth itself. Instead, it was forged in the hearts of massive stars and during the explosions known as supernovas.
In these cataclysmic events, the extreme temperatures and pressures allowed lighter elements, like hydrogen and helium, to fuse into heavier ones. When these stars exploded, they scattered those precious elements across the universe. Over time, this stardust merged into clouds of gas and dust that eventually formed our solar system.
That means every piece of gold on Earth, whether in jewelry, electronics, or buried deep underground, was created billions of years before our planet even existed. In a way, gold is a reminder that we are made of the universe’s oldest and most powerful events.

WATER
The Sun formed about 4.6 billion years ago making it older than Earth which came into existence shortly after at around 4.5 billion years ago. However the water on our planet tells a much older story. The hydrogen atoms in Earth’s water were created in the Big Bang nearly 13.8 billion years ago while the oxygen atoms were forged in the hearts of massive stars that lived and died long before our solar system was born. These ancient elements combined in interstellar space to form water molecules which were carried to the young Earth by comets and asteroids. This means that the water flowing in our oceans, rivers and even within us is billions of years older than the Sun itself connecting us directly to the earliest moments of the universe

OXYGEN
Many people believe that trees are the primary source of the oxygen we breathe but the truth is more fascinating. While forests especially rainforests do play an important role in producing oxygen and balancing carbon dioxide, the majority of Earth’s oxygen actually comes from the ocean. Tiny marine organisms called phytoplankton carry out photosynthesis, just like plants on land and they are responsible for producing around 50–80% of the oxygen in our atmosphere. These microscopic life forms float near the ocean’s surface, absorbing sunlight and carbon dioxide and in the process, they release vast amounts of oxygen that sustain life on Earth.

STAR S62
At the heart of the Milky Way lies Sagittarius A*, a supermassive black hole around which one of the universe’s fastest known stars is racing. This star, named S62, has stunned astronomers with its incredible orbital speed, reaching 8% of the speed of light over 15 million miles per hour.

Such extreme conditions create powerful distortions in space-time. S62 doesn’t just move quickly; it experiences time differently, running slower compared to the rest of the universe. This effect, known as gravitational time dilation, is a direct demonstration of Einstein’s general relativity in action. Watching S62 is like seeing Einstein’s ideas unfold before our very eyes.

The discovery of S62 proves that black holes are not only mysterious giants but also perfect laboratories for testing the deepest laws of physics. Every orbit this star makes helps scientists confirm the strange yet elegant truth of how space and time really work.

Source: European Southern Observatory (ESO), NASA, LiveScience

The observable universe is approximately 13.8 billion years old. Yet astrophysical models suggest it has access to hydrogen fuel for star formation for up to 100 trillion years. That means the universe has only lived through about 0.0138% of its star-forming potential; a mere embryonic phase in cosmic terms.

This staggering realization reframes our place in the cosmos. Far from being latecomers, humanity may be among the first intelligent civilizations to emerge. The vast majority of stars, and potentially trillions of habitable planets, have yet to be born. As long as hydrogen remains abundant, new stellar systems will continue to form, each with the possibility of nurturing life.

The implications are profound. If intelligent life arises even rarely, the future could host trillions of civilizations, each with its own culture, science, and story. Our existence may be a preview of what’s to come; a whisper before the cosmic symphony begins.

This perspective challenges human intuition. We often view the universe as ancient and ourselves as late arrivals. In truth, we are pioneers in a universe that is just beginning to awaken. The age of stars is young. The age of minds has barely begun.

Is light the fastest thing ? 
The expansion of the universe presents a fascinating phenomenon that aligns with Einstein’s theory of relativity while challenging intuitive notions about speed. Special relativity establishes that no object can move through space faster than the speed of light, approximately 299,792 km/s in a vacuum. However, the universe’s expansion as described by general relativity, involves space itself stretching rather than objects moving through it. Observations since Edwin Hubble’s work in the 1920s reveal that distant galaxies recede from us at speeds proportional to their distance governed by Hubble’s constant (around 70 km/s per megaparsec). For galaxies beyond roughly 14 billion light-years, this recession speed surpasses that of light. This doesn’t contradict relativity because the galaxies aren’t traveling through space; the space between them is expanding, carrying them apart. This effect was especially pronounced during the inflationary epoch shortly after the Big Bang, when the universe underwent rapid, exponential expansion. Today, the observable universe, spanning about 93 billion light years continues to grow, driven by dark energy which makes up approximately 68% of the universe’s energy density and accelerates this expansion. As a result, distant regions move apart at speeds exceeding light, rendering them causally disconnected from us. This stretching of space itself, rather than motion within it, allows the universe to expand in ways that transcend the limits of light speed, offering profound insights into the nature of the cosmos.

Voyager 1 is a space probe launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and the interstellar space beyond the Sun’s heliosphere. It was launched 16 days after its twin, Voyager 2. It communicates through the NASA Deep Space Network (DSN) to receive routine commands and to transmit data to Earth. At a distance of 166.40 AU (24.9 billion km; 15.5 billion mi) as of May 2025, it is the most distant human-made object from Earth. Voyager 1 is also projected to reach a distance of one light day from Earth in November of 2026.

The probe made flybys of Jupiter, Saturn, and Saturn’s largest moon, Titan. NASA had a choice of either conducting a Pluto or a Titan flyby. Exploration of Titan took priority because it was known to have a substantial atmosphere. Voyager 1 studied the weather, magnetic fields, and rings of the two gas giants and was the first probe to provide detailed images of their moons.

As part of the Voyager program and like its sister craft, Voyager 2, the spacecraft’s extended mission is to locate and study the regions and boundaries of the outer heliosphere and to begin exploring the interstellar medium. Voyager 1 crossed the heliopause and entered interstellar space on August 25, 2012, making it the first spacecraft to do so. Two years later, Voyager 1 began experiencing a third wave of coronal mass ejections from the Sun that continued to at least December 15, 2014, further confirming that the probe is in interstellar space.

In 2017, the Voyager team successfully fired the spacecraft’s trajectory correction maneuver (TCM) thrusters for the first time since 1980, enabling the mission to be extended by two to three years.^[13] Voyager 1‘s extended mission is expected to continue to return scientific data until at least 2025, with a maximum lifespan of 2030 when its radioisotope thermoelectric generators (RTGs) may supply enough electric power to return engineering data until 2036.

Voyager 1 was built by the Jet Propulsion Laboratory (JPL). It has a bus shaped like a decagonal (ten-sided) prism. It has 16 hydrazine thrusters, three-axis stabilization gyroscopes, and referencing instruments to keep the probe’s radio antenna pointed toward Earth. Collectively, these instruments are part of the Attitude and Articulation Control Subsystem (AACS), along with redundant units of most instruments and eight backup thrusters.The spacecraft also included 11 scientific instruments to study celestial objects such as planets as it travels through space.
The radio communication system of Voyager 1 was designed to be used up to and beyond the limits of the Solar System. It has a 3.7-meter (12 ft) diameter high-gain Cassegrain antenna to send and receive radio waves via the three Deep Space Network stations on Earth. When Voyager 1 is unable to communicate with Earth, its digital tape recorder (DTR) can record about 67 kilobytes of data for later transmission. As of 2023, signals from Voyager 1 took more than 22 hours to reach Earth.
Power. Voyager 1 has three radioisotope thermoelectric generators (RTGs) mounted on a boom. Each MHW-RTG contains 24 pressed plutonium-238 oxide spheres.The RTGs generated about 470 W of electric power at the time of launch, with the remainder being dissipated as waste heat. The power output of the RTGs declines over time due to the 87.7-year half-life of the fuel and degradation of the thermocouples, but they will continue to support some of their operations until at least 2025.
Computers.
The Attitude and Articulation Control Subsystem (AACS) controls the spacecraft orientation. It keeps the high-gain antenna pointing towards Earth, controls attitude changes, and points the scan platform. The custom-built AACS systems on both Voyagers are the same.

Scientific Instruments