Earth’s Place in the Cosmos:

Click to see a larger image – Image Source

As we’ve discussed previously, the Earth is nothing but a small, (albeit important), hunk of rock and water, orbiting a middle-age star in a large barred-spiral galaxy. Although it is the only known planet to harbor conscious life-forms, who can see and understand the universe we were born into, our planet is generally only a blip on an impossibly large radar. Heck; for the largest chunk of our existence, many people believed that our galaxy was all there is. Furthermore, others believed that our solar system was unique in the fact that it harbors planets. It wasn’t until the early 1990’s that the first extrasolar planet was confirmed, orbiting a pulsar

Click to see a larger image - Image Source
Click to see a larger image - Image Source

 Now, however, with the invention of the modern telescope, we know that the universe is much larger than we are capable of processing, as it has hundreds of billions of galaxies, each home to billions of stars. Even venturing off from dry land, heading away from our protected home, the closest objects seem, like our own moon, so far out of reach. Most of them will remain that way indefinitely.

So, lets take a peep at some of those distant trenches of the universe. Let me totally blow your mind here:


Earth & Our Solar System:


on a string, on a string (Image Source)

 We start out on Earth, the blue marble, our home planet, where you, your family, your friends and everyone you have ever known evolved on. Our planet is approximately 4.5 billion years old and orbits our parent star from a distance of about 150 million kilometers, with one full orbit occurring once every 365.242199 days. Earth is but one small oasis in the desert, starting out with the innermost rocky bodies (Mercury, Venus and Mars), with four large gas-giants that follow.

Overall, there are 8 primary planets (sorry Pluto), more than 200 moons, innumerable asteroids, comets and planetesimals, that all extend about with 2 light-years (or about 125,000 AU) in total. All of which, are gravitationally bound to the sun — a hot ball of superheated plasma, held together by the immense forces of gravity.


The Local Interstellar Cloud:


imagesOur parent star (and our solar system in general) is thought to be a small part of the local interstellar cloud, which stretches about 30 light-years across. Regions similar to this generally contain a plethora of materials, such as gas, interstellar dust, molecular clouds and plasma. Our solar system likely entered the cloud about 100,000 years ago and will remain there for the next 150,000 years, protected by a great magnetic bubble.

Our solar system is just a tiny portion of a much larger, much more chaotic place—a place which we call the Milky Way, our home galaxy. Overall, it spans more than 100,000 light-years in diameter, containing over 200 billion stars, innumerable planets, cosmic nebulae, supernovae remnants, open and globule clusters, with many neighboring satellite galaxies. Many of these neighboring galaxies have already merged with the Milky Way, kicking off new star formation activity. Perhaps these galactic mergers have sent super-massive black holes spiraling inward, ultimately merging with our own black hole (aptly named “Sagittarius A*). This celestial heavyweight contains the mass of 4.1 million suns.

Continuing on from our place in the cosmos, our galaxy is a part of the larger “Local Group,” which contains at least 54 galaxies, including the Andromeda galaxy (the largest member) and Triangulum. Mostly though, the local group is comprised of dwarf and satellite galaxies. Thus group stretched more than 10 million light-years in diameter.


Click to see a larger image – (Source)

The galaxies are held together by the gravity of dark matter that has entwined the galaxies together, with the gravitational center located between the Milky Way and Andromeda. Interestingly, the Andromeda galaxy is shifted toward the bluer wavelength, which indicates that the galaxy is traveling toward us, instead of away. Because of this, the two galaxies will eventually collide. In about 5 billion years, Andromeda will come hurling though the Milky Way, forming an elliptical galaxy and kick-starting an intense period of star formation, changing our galaxy forever.

Our planet, our solar system, our interstellar cloud, our galaxy, our galaxy’s dwarf-galaxies, Andromeda, and our local group belong to the Virgo Super-cluster, which stretches over a region of 33 megaparsecs (110 million light-years), containing between 1200 to 2000 galaxies)

The Virgo Super-cluster is but one entry in the Pisces-Cetus Super-cluster Complex. This complex is a colossal galactic filament, which has an estimated length of 1 billion light-years and an estimated width of 150 million light-year. Yes, 1 billion light-years. The size is simply astonishing. Also included in this complex are about 60 clusters, including the A151 cluster, IC 77, the Pegasus-Pisces Chain, the Perseus-Pegasus Chain, the Sculptor Region, and the Virgo-Hydra-Centaurus Super-cluster.

imagesAll of the structures we have mentioned can be seen in the “observable universe,” which has a radius of 13.7 billion light-years and a diameter of about 93 billion light-years. So even at this distance, we are only touching the tip of the iceberg. Contained within the observable universe, there are an estimated 10 million super-clusters, 350 billion large galaxies like the Milky Way, 25 billion galaxy groups, 7 trillion dwarf (or satellite) galaxies with about 30 billion trillion stars.

We are handicap in regards to seeing the universe that lies beyond the ‘light horizon‘ (the part of the universe we can see) as light travels at a finite speed, meaning that enough time must go by for the light from the most distant of these objects to travel through the interstellar medium before arriving here (where we can see and measure it).

The entirety of the whole universe, the mass of objects that live beyond the “observable” portion of the cosmos is unknown (as we can’t see it), but many physicists think the universe is infinite in size (due to spacetime itself extending with help from the elusive thing we know as “dark energy”) going onward forever.

To sum:

Earth → Solar System → Local Interstellar Cloud → Milky Way Galaxy → Local Group → Virgo Supercluster → Pisces-Cetus Supercluster Complex → Observable Universe → Universe

Jaime Trosper

About Jaime Trosper

Jaime is a freelance writer, who finds great joy in sharing the wonders of universe with others. She used this passion to launch "From Quarks to Quasars" in 2012.