Facts About The Sun: Information, Fun Facts, History & More
What Is The Milky Way Exactly?
Our Sun. The Sun, as seen from the Solar Orbiter. (Credit: NASA/ESA)
Andrea Minoia June 25, 2021
So, you like astrophotography. You spend money and time to photograph the many wonders of the universe to try to get the best images you can.
But do you really know what it is that you are photographing?
We are so often caught up in technical details, all worried about using the right equipment and technique, that we may forget the very nature of what we are trying to capture.
Today we introduce a new type of article, to uncover together the nature of the things that keep us up all night.
But let’s begin with a target that is very special to us, the only target that keeps astrophotographers busy photographing in the daytime.
The galaxy that we live in is known as the Milky Way galaxy. It consists of a collection of stars and planets that are gravitationally bound together in a swirling spiral. One of those planets is earth.
According to a NASA report, our galaxy is only one in about 2 trillion galaxies. Groups of these galaxies are combined into clusters; the group we belong to is creatively known as the “Local Group.”
As you can see in the many images of the Milky Way, you will see a dim, milky looking glow circling the outer edge. This is caused by the countless bright burning stars that surround it.
In ancient times, the Romans would call it “via lactea,” which, when translated, roughly means “milky way/road.”
While the most common name we call it is the Milky Way, it is interesting to note that different cultures have given it their own name over time.
For example, the Hindi given name is ‘Aakaash-Ganga ‘– which means (Ganges river of Heaven). Germans call it ‘Milchstrasse”, Norwegians gave it the name ‘Melkeveien ‘and the Chinese name when translated into English means “silver river.”
Finding out what does the milky way look like is not hard these days, thanks to the dedicated astrophotographers who have spent many hours to capture some breathtaking night sky images.
The milky way is usually the main attraction in many astro images, but below you find out that what we can see with a digital camera is not all there is to the mysterious Milky Way.
Our general view of the milky way is from a side angle, but when viewed from a top-down perspective, you will notice the Milky Way is a round swirl. The best way to describe the shape is a disk-like shape.
If we were to measure the shape, the Milky Way length would be between a hundred thousand light-years and one hundred and twenty thousand light-years in diameter.
But only around one thousand light-years in thickness (top to bottom).
It’s not entirely flat though, the edges are somewhat curved, giving the Milky Way a warped shape.
From the top perspective, you see that it is round in shape, actually more like a spiral. It contains a center, ironically called the “bulge” which scientists estimate it measures approximately 25,000 light-years in thickness. The remainder of the spiral is suns, planets, and compressed gases and dust. The brighter the white haze, the more concentrated it is.
Until recently, it was believed that if viewed from above, the Milky Way consisted of four primary spiral arms that were part of the disk.
But new research has revealed that it seems to only consist of just two called Carina–Sagittarius and the other Scutum–Centaurus.
Because of where we are inside of the galaxy and the Milky Way, we will always have a viewing angle of “side-on” for the Milky Way.
To put it into perspective, say you’re standing out the front of your house, having never walked out further than the front door.
If you look left you can see what’s there and if you look right you can see what’s there, but you can’t see the street as a whole. Nor can you see the whole street from above.
That’s somewhat our situation from earth. We can’t see the Milky Way from the outside in. We will always be looking at it from the inside “on our front door.”
If you have ever seen some of the stunning images that astrophotographers have captured of the Milky Way, you will notice the milky band at the edges of the milky way.
The milky edge is a concentrated buildup of millions and millions of bright stars all shining so bright that it looks like a brilliant white edge of the Milky Way.
Another reason we see quite a lot of the white edge is because of the angle that we’re positioned to the milky way, we are viewing it “side-on” which gives the Milky Way a flat look.
The white milky edges are a buildup of millions and millions of bright stars.
While there and many galaxies out there deep in space, the Milky Way is the galaxy that we call home. In this section we’ll discuss measurements, so we truly appreciate how big our galaxy actually is.
Its size is so large, it’s almost hard to comprehend. The diameter of the disk of the Milky Way ranges in diameter between 100,000 to 120,000 light-years, end to end.
To get a little perspective, one light-year equals 5.878625 trillion miles (or 9.461 trillion kilometers). Using the word massive is almost a little underwhelming when describing how enormous the milky way is.
Due to its humongous size, the Milky Way is home to many other celestial bodies. It’s been estimated that within the vast range of the Milky Way, it houses 100 billion planets at least.Add in around 100-400 billion stars and probably billions of other objects, and you start to get an idea of how big it is.
While that does sound huge (and it is), it still makes us the little brother to our next-door neighboring galaxy – Andromeda galaxy. It is estimated the Andromeda galaxy is estimated at 220,000 light-years, end to end. Making it close to double our size.
A light-year (the distance the light travels in a year) is the most common way we use to measure objects in the universe. To put that into perspective in everyday terms, a light-year speeds along at 186,000 miles per second (or 300,000 km second).
There are 31,536,000 seconds in a year, so if we times that by the speed of light per second, we get 5.8 trillion miles (9.5 trillion kilometers) is the distance of a light-year.
Because we are part of the Milky Way system, it is relatively easy for us to photograph the Milky Way. With a little planning and some practice, relatively new photographers can capture some stunning images of the Milky Way.
Most photographers like to capture the galactic center of the Milky Way as it is the brightest and most exciting part to shoot.
Depending on where you are located, northern or southern hemisphere, the main part of the Milky Way (galactic core) is only visible at certain times of the year. Also known as the Milky Way seasons.
If you want to learn more about photographing this fantastic part of the universe, we have written a full guide on how to capture images of the Milky Way here.
Landscape astrophotography – using the milky way as the background scenery.
Of all the galaxies in our universe, they can be categorized into one of 3 types of galaxies. It wasn’t always the case that we had a category or even knew about them all. We can thank Edwin Hubble, who back in the history books in 1926 created a classification and documented the various types of galaxies.
The criteria for categorizing them is based on their shape and the way they look, which makes them easily identifiable just by looking at them.Of the three types of galaxies, two of them are further subdivided into subsections of their parent category, known as the turning fork model. Below are an example of the three types:
The kind of galaxy that we classify the Milky Way is a Barred Spiral. A standard spiral galaxy is easy to identify due to the three main components, a disk, a bulge and a halo.
A barred spiral galaxy (which is the shape of the Milky Way) is very similar to a spiral galaxy, they have the three main parts of a spiral, but they also have a concentrated bar of bright stars that connect from the centre bulge all the way out to the outer disk
Our galaxy is no different from most other galaxies, most other galaxies contain a supermassive black hole (also known as a SMBH).
In 1971, two astrophysicists from the University of Cambridge presupposed the Milky Way center contains a black hole. Further testing showed a radio source at the galactic center, which from our solar system is around 26,000 light-years away.
The radio wave source is believed to be a black hole (named Sagittarius A) which spans a distance of 14 million miles wide. Put into perspective this measures about the same as the size of Mercury’s orbit.
A black hole.
Everything in the universe is moving through space, and the Milky Way is no exception. While we know the Earth rotates around the Sun, and the Sun rotates around the Milky Way, the Milky Way (as part of the Local Group) is also moving.
The way speed is measured in space is using the Cosmic Microwave Background (CMB), the radiation that remains from the Big Bang.
Using the CMB is a convenient way to calculate how fast everything is moving. The Local Group is estimated to be speeding along at 2.2 million km/h.
There are between 100-400 billion stars in the Milky Way, that sounds like a lot but the Milky Way sits mid range compared to other galaxies.
Even with that many stars in the sky, you can only visually see up to around 2,500 stars from a single location on earth.
You can only see a maximum of 2,500 stars from a single location.
Many believe that the Andromeda Galaxy is our closest galaxy, but that’s actually not the case.
While Andromeda is our closest “spiral” galaxy, it’s not the overall closest, not even close.
The name of the closest galaxy to the Milky Way is the Canis Major Dwarf Galaxy (the Canis Major Overdensity). Situated about 42,000 lightyears from the Milky Way’s galactic center, making it our closest neighbor.
Andromeda Galaxy – is double the size of our Milky Way
We are part of a collection of galaxies known as the Local Group. Some of these other galaxies are so prominent that they are visible on a clear sky. Which means some of these other galaxies are quite well known with amateur astronomers when finding objects in the sky.
The biggest galaxy in the Local Group is called the Andromeda Galaxy or M31Coming in second in size is our own Milky Way and third on the list is the Triangulum Galaxy, also known as M33.
It is believed that in approximately 4 to 5 billion years, the two largest galaxies (Milky Way and Andromeda) will collide into each other.
There shouldn’t be any need for worrying though, even though our galaxy (Milky Way has approximately 400 billion stars) and Andromeda probably has more, not even one star should collide with another due to the amount of space in each galaxy.
The Milky Way is fascinating to see, and we always recommend if you do get a chance, go out to a dark location and away from light pollution.
Appreciate the marvel that it is (and don’t forget to capture some pics of it too).
