How does our solar system orbit the Milky Way, and why does it take 250 million years to complete one orbit?

 The solar system orbits the Milky Way galaxy at an average speed of about 828,000 kilometers per hour (515,000 miles per hour), taking approximately 230 million years to complete one full orbit around the galaxy's center. This journey is often referred to as a "galactic year."

If you could teleport instantly thousands of light years outside our galaxy and look down upon it with supertelescoping vision you might see something like this:

The Milky Way galaxy spins like water going down a drain with our local group in one arm halfway between the core and the outside edge at a distance of around 27,000 light years.

Our solar system orbits with the Sun dragging the other planets in tow, making the solar system look like it is flying sideways, always moving up since the solar system is tilted that way.

What are some interesting facts about the Milky Way?

 1. The Milky Way is very old

At present, the scientific community believes that the age of the universe is about 13.7 billion years. However, scientists have also discovered that the Milky Way may be one of the earliest galaxies formed in the universe. This is based on the discovery of a 13.5-billion-year-old star in the galaxy (number J0815 + 4729) It is calculated that the star should also be one of the earliest formed stars in the universe. The heavy elements contained in the star through spectral analysis turned out to be only one millionth of the sun, indicating that this star was almost not in the universe when it was formed. Heavy elements.

2. The Milky Way is annexing small galaxies

Scientists have discovered that there are two smaller satellite galaxies on the edge of the Milky Way-the large and small Magellanic Clouds. There is reason to believe that many stars in these two galaxies are being attracted by the gravitational field of the Milky Way. Scientists believe that the size of the large and small Magellanic Clouds It used to be much larger than it is now, but due to the weak gravitational field of the galaxy, its own stars are constantly detached. Understanding the evolution of the large and small Magellanic Clouds can know the future changes of the Milky Way.

3. 200 billion stars are unobservable

In the universe, the Milky Way is only a medium-sized galaxy. Scientists have calculated that there may be 200 to 400 billion stars in the Milky Way, but humans can only observe about 250 billion stars at most. Most of the stars cannot be directly detected because of their orbits. Observed, but most of these stars are obtained by the Milky Way through the merger of other small galaxies, and the galaxies are also used to maintain enough material to produce stars.

4. The Milky Way is distorted

In the photos of the Milky Way we have seen, it is a plate-shaped spiral galaxy. Now, astronomical observations have found that the Milky Way is not a plane from the side, but a somewhat twisted shape at both ends. At the center of the galaxy, a large number of stars have formed. A highlight of the core area.

5. "Bubble" in the center of the galaxy

Scientists have only recently discovered that there are large structures called "Fermi bubbles" at both ends of the Milky Way, formed by the supermassive black hole "Sagittarius A *" in the center of the galaxy, extending up and down about 20,000 light-years. The reason for the formation of these eruptions is still unknown, but it must be related to the large amount of black hole engulfing material.

6. A galaxy merger is taking place in the Milky Way

Mergers between galaxies in the entire universe are very common. The Milky Way is also close to the nearby Andromeda galaxies. In the future, the two galaxies will collide and merge into a larger galaxy. The size of the Andromeda galaxies far exceeds the Milky Way. With one trillion stars, this process of galaxy fusion will continue for billions of years, and the galaxies after fusion will continue to move closer to other galaxies.

7. The position of the Milky Way in the universe

Although the size of galaxies is large enough for humans, the Milky Way is actually only one member of a large-scale galaxy cluster. There are thousands of galaxies around the Milky Way, including the fairy galaxies, to form a larger room. The female galaxy cluster, the entire Virgo galaxy cluster is moving at a speed of 1180 kilometers per second. It can be said that the Milky Way galaxy is not conspicuous in this huge galaxy cluster, and can only be regarded as one of the oldest members.

Understanding the Milky Way can see the operation mechanism of the entire universe. Although the distance between galaxies is far away from each other, they are constantly merging.

What are some interesting facts about the Milky Way?

 

The Milky Way is one of the most studied topics in human history, and for good reason.

It is one of the few observable features that pre-modern humans in particular could observe regardless of their nationality, culture, and education.

Over the centuries more theories have come about regarding the status of our galaxy, its place in the universe, and… whether or not it is made of milk!

FACT NUMBER ONE — It takes 100,000 light years to travel across the Milky Way

Light travels at 186,000 miles, or 299,792 kilometres per second — the equivalent of going around the Earth nearly eight times.

And even at that speed, it would take 100,000 years of non-stop travel just to go from one side of the Milky Way to the other.

FACT NUMBER TWO — There are 400 billion stars and 3.2 trillion planets in the galaxy

Some estimates are more modest at 100 billion stars and under one trillion planets, but even with the more conservative figures, we would be talking about more stars in the Milky Way than the number of humans who ever existed, and more planets than one each for every second of human recorded history… times five!

FACT NUMBER THREE — The Milky Way is puny compared to other galaxies

Even though the Milky Way is larger than most galaxies, it still pales in comparison to other competitors, such as IC 1011, which is said to take approximately six million light years to travel, making its width sixty times larger — and this does not even include the height and depth.

FACT NUMBER FOUR — 100 million black holes populate the Milky Way

Aside from the countless millions of black holes just in our Milky Way Galaxy, a particularly large one known as Sagittarius A resided near its centre, approximately 50,000 light years from Earth.

FACT NUMBER FIVE — Our Solar system orbits the Milky Way every 250 million years

Much like Earth, even the Milky Way orbits a centre of mass that is itself a giant black hole (Sagittarius A).

Of course, since we are still 50,000 light years away from this epicentre, we do not need to worry about being sucked into its gravity any time in the future!

FACT NUMBER SIX — There are over 2 trillion galaxies in the observable universe

There are as many galaxies in the observable universe as there are planets in the Milky Way — an area spanning approximately 93 billion light years.

In addition, the non-observable universe is estimated to be 15,625,000 times larger — gives one an idea of just how much is left to be seen.

FACT NUMBER SEVEN — Over six billion Earth-like planets exist in the Milky Way

There are almost as many Earth-like planets as there are humans currently inhabitating this planet, and many of them are even larger than this rock, with Kepler-452 in particular being nearly two-thirds larger, with a diameter of over 14,000 kilometres compared to the 12,742 kilometres.

FACT NUMBER EIGHT — Cultures around the world saw the Milky Way as a pathway for deceased souls

From the Indigenous cultures of the Americas, to the Greeks and Romans of Europe, the Egyptians and Persians of Africa and the Middle East, and even the Chinese, Koreans, and Japanese of the Far East, the Milky Way was interpreted as a roadway for souls.

Quite impressive, considering the fact that there is no way that any of these peoples were talking to one another when these recordings came up several millennia ago.

FACT NUMBER NINE — The Milky Way is producing more stars

Despite the fact that its most dramatic creation phase has long passed, the Milky Way still continues to create at least seven stars per year, meaning that in an average human lifetime, nearly 600 stars are being created — many of them far larger than the sun — plus hundreds of new solar systems and thousands of new planets to go with it, some of which may one day possess life much like ours.

FACT NUMBER TEN — The Milky Way will live for 100 trillion years

The Milky Way is estimated to have a lifespan of 100 trillion years, meaning that if we consider the fact that the universe itself is only 13,800,000,000 years, then its lifespan will be nearly 8,000 times longer — if the Milky Way’s lifespan were compared to that of a normal human lifespan, then it would only be three days old!

Whether or not the Milky Way will produce new galaxies after its demise is unknown at this time, though astronomers estimate that in four billion years the Milky Way and Andromeda will become one, and who knows what other members of the Burger Cluster will join this family.

BONUS — The Milky Way is not made out of milk

As disappointing as it is for some to realise, the Milky Way cannot produce milk the way humans, cows, and other mammals can.

Then again, seeing as so many cultures saw the lights of the Milky Way as a heavenly pathway to a better life, perhaps more milk than we could ever care to consume will be waiting for us on the other side of this dimension.

VY CANIS MAJORIS, one of the largest stars in the Milky Way

 When the French astronomer Jérôme Lalande first observed VY Canis Majoris in 1801, he described it as a seventh magnitude star like many others. Certainly, Lalande did not expect that this faint dot was actually a very bright red hypergiant and one of the largest stars in our Galaxy.

VY Canis Majoris is a star still shrouded in many mysteries, whose physical properties are little known.

One of the few well-known aspects is its variability: the star indeed varies its brightness over a cycle of 956 days, going from an apparent magnitude of 9.6 to one of 6.5, at the limit of visibility to the naked eye.

As for the distance, the value is very uncertain, but the best estimates suggest it is located 4000 light-years away from us.

From the spectrum of VY Canis Majoris, it has been found that it is an M-type star with a surface temperature below 4000 Kelvin, in addition to some information on the atmospheric composition.

From visible and infrared photometry, it has been derived that the star should be 350,000 times more luminous than the Sun, thus making it one of the most luminous stars in the entire Milky Way. The star, however, is surrounded by a shell of gas expelled in the past, which absorbs much of the radiation making it invisible to the naked eye from Earth.

According to the most recent estimates, the star is indeed expelling about 0.01 solar masses per year into space. Consequently, its current mass, estimated at 17 solar masses, is much lower compared to its original mass.

The estimate of the diameter of VY Canis Majoris is strongly influenced by the values assumed for the other stellar parameters and by the presence of the shell that surrounds it. Estimates of its size vary between 1400 and 2000 solar diameters, placing it in any case among the largest stars in the Milky Way.

In this artistic representation, the size of VY Canis Majoris is compared to that of the Sun and Earth's orbit.

Image Credit: Oona Räisänen.

Are there any areas in the Milky Way that are unlikely to have life?

 

As noted in the answer by Tom Nathe, the galactic core is too tightly packed with stars to have conditions that would be conducive to life. The proximity of stars to each other means that the orbits any planets around these stars would be disturbed by gravitational interactions with other stars, and thus would likely not have stable orbits.

Because the core of the galaxy is not usually thought to be a good place for habitable worlds, some astrobiologists identify a “galactic habitable zone” (GHZ), which is an habitable zone for the entire galaxy, analogous to the habitable zone around a given star, which latter is then referred to as a “circumstellar habitable zone” (CHZ). Any planetary system outside the GHZ would be considered an unlikely place to find life.

Globular clusters—small mini-galaxies of thousands to millions of stars that orbit larger galaxies—are similarly closely packed with stars and so pose problems for planetary habitability. A recent paper examined this: “Habitability in the Omega Centauri Cluster” by Stephen R. Kane and Sarah J. Deveny.

Another problem with globular clusters—a problem from the perspective of being clement to life—is that the processes of galactic ecology that work in the main body of the galaxy do not work in globular clusters. Galactic ecology is what we call the recycling of material from stars that explode in a supernova, scattering their remnants, which are then later incorporated into later generations of stars, which as a consequence have a higher level of heavier elements (both due to nucleosynthesis while the former star was fusing elements in its core, as well as new elements created by the supernova event itself). Planetary systems that incorporate more heavy elements (i.e., are higher in metallicity) are likely to be more minerologically and hence more geologically complex, and it is likely that geological complexity plays a role in the emergence of life.

An important caveat to the above: it should be observed that conventional conceptions of habitability have been questioned recently as we have learned that moons in our solar system (and probably also planets elsewhere in our galaxy) have large subsurface oceans under kilometers of ice exposed to the cold and vacuum of space. It is possible that life could arise in subsurface oceans, in which case the requirement of a planet being in a CHZ where liquid water could be found on its surface may be too narrow a criterion for searching for life and for the definition of a habitable zone.

If we reconfigure the idea of a habitable zone to allow for life in subsurface oceans, and perhaps also to allow for kinds of life radically different from life on Earth, the GHZ may be much larger than in the illustration above, and it may, in fact, include all regions of our galaxy.

Biggest Stars of our Milky Way Galaxy

 Imagine the biggest star we know, called UY Scuti. This star is so huge that if we placed it at the center of our solar system instead of the Sun, its outer layer, called the photosphere, would stretch all the way out to where Jupiter orbits. In other words, it would be even bigger than the Sun and would engulf space up to Jupiter's orbit, which is really far from the center of our solar system.

But that is not all, there are various factors taken into consideration while determining the size of a star, and some of them are.

1. Mass: The amount of matter a star contains is a crucial factor in determining its size. Stars with more mass tend to be larger.

2. Age: As stars age, they can change in size. Some stars expand as they evolve, becoming larger as they reach different stages of their life cycles.

3. Composition: The elements and gases that make up a star also play a role. Stars with different compositions can have varying sizes.

4. Temperature: The temperature of a star's core can affect its size. Higher core temperatures can lead to more intense nuclear reactions, which can either cause a star to expand or contract.

5. Gravity: The gravitational force acting on a star can influence its size. Stars with stronger gravity tend to be more compact, while weaker gravity can allow a star to expand.

6. Internal Pressure: The balance between the gravitational force pulling a star's matter inward and the pressure from nuclear reactions pushing outward determines its size. When these forces are in equilibrium, a star has a stable size.

These factors interact in complex ways, leading to a wide variety of star sizes and shapes in the universe.

If stars were the size of atoms, how much space would the Milky Way Galaxy take up?

The sun is a medium size star. If the sun were as small as an atom, and the the other stars are proportionately as small, how big the Milky-Way galaxy would be? YOu know Sun is a medium sized star. We will use Sun for the comparison.

• Diameter of Sun 1.4 million KM
• Diameter of Milky-Way 100,000 light years

From this, we can compare the size difference between the Sun and the Milky-Way. One light year is 9.46 Trillion kilometers. Which is 9,460,000 million KM. So, in a distance of 1 light year, you can fit (9,460,000/1.4) 6,757,143 Suns.

Now, let is see, how many Suns can fit inside the Milky-Way. With 100,000 light years across, the Milky-Way can fit (6,757,143x100,000) 6,757,143,000,000 Suns.

So, when the sun is as small as an atom, the Milky-Way galaxy would be as big as 6,757,143,000,000 atoms. Let us see, how big space those many atoms can take. One centimeter contains 100,000,000 atoms. So, 6,757,143,000,000 atoms will take a length of ( 6,757,143,000,000/100,000,000) 67,571 centimeters. That is 676 meter (approx.).

When the sun is as small as an atom, the Milky-Way galaxy will be as big as a circle that have a diameter of 676 meter. That circle will have an area of 358,726 square meters. Which is roughly as big as a football stadium.

If the space were microscopic size, if the stars were as small as atom, the galaxies would still be as big as stadiums.

Theoretically, how would one travel out of the Milky Way?

 

Interesting question! According to Albert Einstein, traveling at or exceeding the speed of light isn't possible. But let's imagine for a moment that we have a spaceship capable of light-speed travel and want to visit the Andromeda Galaxy, our nearest spiral galaxy.

The Andromeda Galaxy is close by cosmic standards—only 2.5 million light years away. To put it into perspective, a light year is the distance light travels in one year, roughly 5.88 trillion miles (9.46 trillion kilometers). So, even at light speed, it would still take 2.5 million years to get there.

The vast distances in space are truly mind-boggling. Andromeda is just our nearest neighbor; there are galaxies hundreds of millions or even billions of light years away. Even at the ultimate speed limit set by physics—the speed of light—reaching these distant galaxies would take an unimaginably long time. It’s safe to say that, for now, intergalactic travel remains firmly in the realm of science fiction.

Which is too bad because wouldn’t it be cool to explore the great expanse between the Milky Way and Andromeda galaxies, where there are very few stars, but there’d be great views of both galaxies? This intergalactic space, often thought of as an empty void, is actually a realm in outer space filled with subtle wonders. While it's true that the density of stars and other celestial bodies drops off dramatically in these regions compared to the bustling interior of a galaxy, the space between galaxies—called the intergalactic medium—still holds fascinating mysteries.

Imagine traveling through this vast, near-empty expanse. With galaxies like Andromeda and the Milky Way dominating the view on opposite horizons, the vista would be breathtaking. The sky wouldn't just be a dark canvas speckled with stars—it would be punctuated by the grand spirals of entire galaxies, shining faintly but majestically.

There are stars between galaxies, though they are relatively rare. These stars, known as intergalactic stars or intracluster stars, exist outside the boundaries of any particular galaxy. They are scattered across the vast expanse of space between galaxies, often within galaxy clusters. Galaxies frequently interact gravitationally. These interactions can eject stars from their parent galaxies, flinging them into intergalactic space. I wonder if any of them have exoplanets in habitable zones. The view at night for those aliens would be much different than our view inside the Milky Way.

This space is also home to the mysterious phenomenon of dark matter and dark energy. The gravitational pull of dark matter helps bind galaxies together in clusters, while dark energy drives the universe’s accelerated expansion. Exploring the intergalactic void might offer insights into these cosmic puzzles, which remain some of the greatest mysteries in physics.

Intergalactic space is not entirely devoid of matter. It’s filled with tenuous gas, primarily hydrogen, and scattered particles that were either ejected from galaxies or left over from the early universe. This medium might seem insignificant, but its sheer volume across the cosmos means it plays a crucial role in the universe’s structure and evolution.

Our current technology isn’t even close to achieving light-speed travel. The fastest spacecraft we've built to date, the Parker Solar Probe, zips around the Sun at about 430,000 miles per hour (700,000 kilometers per hour). But at that pace, it would still take billions of years to reach Andromeda.

To put this into perspective, even if we aimed to reach the nearest exoplanet, Proxima Centauri b, it would take approximately 6,634 years traveling at 430,000 mph. And that's just within our galaxy, which contains billions of planets orbiting billions of stars.

Beyond speed, intergalactic travel has some other difficulties. We would need sustainable life support systems, protection from cosmic radiation, and an immense amount of energy for propulsion, and that’s simply the tip of the iceberg.

While the idea of traveling to another galaxy is fascinating and a staple of science fiction, the reality is that, with our current understanding of physics and technology, intergalactic travel is not just improbable—it’s impossible. The sheer vastness of space and the constraints imposed by the speed of light make such journeys unattainable not only in one human life, but even the spaceship would break down after thousands of years. For now, we can only look, not touch.

Another fun layer of complexity is time dilation. At speeds approaching the speed of light, time would pass much slower for the travelers than for those left behind. A trip to Andromeda at near-light speed might feel like a few years for the crew, but millions of years would pass back on Earth. They'd return (if ever) to a world unrecognizably changed. A spacecraft would need to travel at approximately 99.999999995% of the speed of light for passengers to experience only 25 years of travel time between the Milky Way and Andromeda galaxies, due to relativistic time dilation. This highlights the extreme velocities required to achieve such significant effects. This wouldn’t violate the laws of physics, but getting to that speed would. We have no technology to even get to 1% the speed of light, what to speak of 99.999999995% of the speed of light. But it’s a fun thought.

Sadly, perhaps, the only journeys to other galaxies will be in our minds, through science fiction, or as a distant dream for civilizations far more advanced than ours. It’s a reminder of the scale of the universe and how small we are in comparison. Dream on.