The Universe is estimated to have 200 billion trillion stars. There are approximately 100 billion stars in each galaxy. That’s a pretty awe-inspiring fact, but what surprises many people is just how far away the stars are from Earth.
Because stars are visible in the night sky, it’s easy to assume they are closer than they actually are.
However, we can see the stars from Earth because they emit incredibly bright light in every direction. Also, there’s not enough matter between the stars and our planet to block that light.
While some stars are much closer to the Sun than others, they are so far away from us that it can be difficult to comprehend.
It is important to remember that every star that you see in the night sky is contained in the Milky Way. That doesn’t mean that we can not see objects outside of our galaxy. On the contrary, there are a number of objects that are visible to the naked eye that exist outside of our galaxy. As an example, the core of the Andromeda galaxy is easily visible to the eye under dark skies. In the southern hemisphere, the two Magellanic clouds are a beautiful sight. These are two dwarf galaxies that orbit our own.
If you’ve ever asked yourself, ‘how far away are stars?’, you’ll find the answers in this guide!
What Is The Closest Star To The Sun?
The nearest star to the sun is Proxima Centauri, which is roughly 4.24 light-years away from Earth (NASA). Proxima Centauri is one of 3 stars that make up the Alpha Centauri triple-star system. The system is located roughly 4.37 light-years from us.
4.24 might not sound like a particularly large number. However, it’s important to remember that a single light-year measures about 5.88 trillion miles (9.46 trillion km). If you are still a bit fuzzy on this, hang on; soon we will explain further.
We can succinctly express the distance between Proxima Centauri and the sun as 2.4925372 x 1013 miles (4.1104 x 1013 km). 1013 is equal to a 1 followed by 13 zeros (i.e. 10,000,000,000,000). The distance to the nearest is 24,925,372,000,000 miles (41,104,000,000,000 km). Those are big numbers! It is easy to see why distances between stars are expressed in light-years.
So, although Proxima Centauri may be the closest star to the sun, it’s still extremely far away. It would take approximately 6,300 years to travel to it using current technology.
After Proxima Centauri here is a list of stars in distance order: Centauri A, Centauri B, Barnard’s Star, Wolf 359, Lalande 21185, Sirius A, Sirius B, and Luyten 726-8 A.
Which Star Is Furthest From The Sun?
If the star closest to our solar system’s sun is still many trillions of miles away, the star furthest from the sun is much farther in distance.
The Hubble Space Telescope has discovered the farthest star. The star has been named Earendel. It’s a whopping 28 billion light-years away from our solar system. We believe that it died about 13 billion years ago. It is believed to have been between 50 and 500 times more massive than the Sun.
This star is so far away that it was located via an effect called gravitational lensing. Gravitational lensing occurs when a large cluster of galaxies bends and focuses light. The lensing allows us to view objects behind the cluster that would not otherwise be visible. It is a fortunate alignment that enables us to see this star.
Earendel formed approximately 4 billion light-years away. With time, the space between the Earth and it has expanded. As a result, we are only now receiving the light from it. Another observation is that the light from it is very red. This is not because the star was red. It is rather that as the intervening space has expanded the wavelength of the light has become longer. The stretching of light in this manner is aptly named red-shift.
How Are Star Distances Calculated?
Wondering how we calculate the distance between us and the stars? Well, for a start, we use a unit known as light-years, which we’ve mentioned several times throughout this article.
A light-year is different from a year on Earth. We use the term ‘year’ to define how long it takes for our planet to complete an orbit around the sun, which is 365.25 days.
However, a light-year is not a unit of time, but of distance. It refers to how far light can travel in a vacuum in one year.
One light-year is equal to 5.9 trillion mi (9.5 trillion km). Light travels very fast, but as we have seen, distances are huge between stars.
However, when you use cosmic scales, light travels quite slowly.
Astronomers use distance units that are alien to many. We touched on what a light-year and now I wish to introduce another. Astronomers often use Parsecs.
A parsec (pc) is defined as the distance at which the average distance that Earth orbits the Sun subtends an angle of one arc second. That is quite a mouthful and may be difficult to understand so let’s break it down.
We need to define what an arc second is. We divide the sky into 360 degrees. Each of these degrees can be divided into 60 minutes. Like with time each minute is divided into 60 seconds. Therefore, one arc second is 1/3600th of a degree. Yes, it is a small angle and a small part of the sky.
A parsec is a distance at which the angle between the Sun and Earth is 1/3600th of a degree (i.e. 1 arc second). The distance at which this occurs is 3.26 light-years.
If you are a little confused, don’t worry. It is a complex concept. Just remember that a parsec is an astronomical unit of distance and that it is equivalent to 3.26 light-years.
Star Parallax
Parallax in stars is the apparent movement of close-by stars against the background of more distant stars. The more distant the star, the less movement will be observed.
We use parallax every day without knowing it. Having two eyes at a distance apart provides our brains with two slightly different views. Our brains can use this to determine the relative distance to the objects around us.
To determine the distance to a close-by star, we must first record the relative position of the star with more distant stars. The relative position is again recorded when Earth is on the opposite side of the Sun (i.e. six months later).
The amount of apparent movement is used to calculate the star’s distance.
Using this method, we can measure stars that are up to about 100 parsecs away. Beyond this, the apparent movement is too small to determine a distance accurately. Therefore we must utilize other methods.
Standard Candle Calculations
Standard candles are astronomical objects that have a known brightness. If we know the object’s intrinsic brightness, we can determine its distance. We can determine the distance as the amount of dimming is directly proportional to the distance the light travels.
For example, if you place a light just in front of your face, it is very blinding. Move the same light across a park, and it appears dimmer.
To measure astronomical distances the objects most commonly used are RR Lyrae variables, Cepheid variables and type 1a supernovae.
RR Lyrae variables are low-mass stars that are commonly found in globular clusters. The period of their variations is directly proportional to their luminosity. In effect, they advertise how bright they are. As they are small and dim, they are only reliable to about 100kpc. For farther objects, we must use other objects.
We can use Cepheid variable stars to measure distances up to about 50Mpc. These variables are large bright stars. As with RR Lyrae variables, their variability period is directly related to their brightness.
The most dramatic of the standard candles considered here are type 1a supernovae. This type of supernova occurs in binary systems. In this situation, one of the two objects orbiting is the remains of a type of dead star called a white dwarf (our Sun will end up as a white dwarf) and the other a normal star.
White dwarfs are compact objects. If the mechanics are correct mass is transferred from the normal star to the white dwarf. The material will accrete onto the white dwarf’s surface. Nuclear fusion will initiate once enough material has been deposited, and a supernova will result.
The mass at which a white dwarf goes supernova is considered to be consistent. Therefore, so is the brightness. Like with RR Lyrae and Cepheid variable stars, the amount of dimming is measured to determine the distance. Distances of up to one billion light years have been measured using this technique.
Final Thoughts
The closest star to Earth is Proxima Centauri, which is 4.24 light-years away. The further star from the Earth to have been discovered has been named Earendel, and this star is a massive 28 billion light-years from our solar system.
Distances between the Earth and the stars can be expressed in light-years or in parsecs.
The parallax method (an angle calculation done using the positioning of the Earth from the relevant star 6 months apart) is used to measure the distance of close-by stars.
However, the standard candle method is used for further away stars. These methods use luminosity and/or variability rates.
Hi, my name is Jason Anderson, and I am a Physics Professor. Ever since I was a kid, I’ve been fascinated with space, the universe, the moon, you name it. I spent hours and hours at the planetarium close to my hometown, wondering what else could be out in the universe.
Since then, I’ve been an avid stargazer and astronomer, and love nothing more than spending my time charting stars, observing planets, and finding constellations.
This is why I decided to start Telescope Guru. I only wish to share this fun pastime with the world. With this site, I hope to answer all of your questions relating to astronomy, telescopes, and stargazing.
