Whirlpool Galaxy

• Distance From Earth: 23.16 To 31 Million Lightyears
• Number Of Stars: 100 Billion

Other than the Milky Way, it is likely the Whirlpool Galaxy is the most well-known for us Earthlings. It happens to be between 20 to 30 million lightyears away from Earth. However, we can see it with basic binoculars. It’s so beautiful that it is considered literally a “grand design spiral galaxy.” These are galaxies with well-defined arms that clearly extend around the galaxy with many radians. Only 10% of all known galaxies are like this. The Whirlpool Galaxy is also so large it interacts with another galaxy. The nearby NGC 5195 dwarf galaxy is called Whirlpool’s “companion.” They interact but don’t disturb the other.

Depending on the exact distance, those alien worlds in Whirlpool could see an interestingly developing Earth. About 34 million years ago, Gondwanaland finished breaking apart. This meant Australia and South America completely separated from Antarctica. The big guy took it pretty hard, as this land then became covered in ice as it moved further south by 24 million years ago. Interestingly, during this same timeframe, grasslands began to form. This was incredibly important as new species would pop up and rule the grasslands just a few million years later.

Eye Of Sauron Galaxy

• Distance From Earth: 50 To 61.97 Million Years
• Number Of Stars: Estimated 10 Million

If you’ve ever seen NGC 4151, you’d likely say it looks like a giant eye. Many astronomers ended up giving it the infamous nickname of the “Eye of Sauron.” The distance it happens to be from Earth is disputed somewhat. Some claim it is roughly 50 million lightyears away while others say it’s a little over 60 million lightyears away. Regardless, this is still a Seyfert Galaxy, otherwise known as one of the two largest groups of galaxy types. We now know it is one of the closest galaxies to the Milky Way with its own supermassive black hole. In fact, while the numbers are disputed, this black hole is still growing.

Depending on the exact light-year distance, they would be seeing a heavily changing Earth. Roughly 60 million years ago, an infamous asteroid hit modern-day Mexico. This caused the extinction of the dinosaurs, but also roughly 50% of all living creatures. On top of this, we had a global Ice Age that lasted for millions of years. Yet by the 50 million mark, modern-day India ended up colliding with Asia. That slowly began to form the Himalayas. Thus, anyone on alien worlds within the Eye of Sauron would be seeing a lot of crazy change. Yet they might assume Earth to be a cold planet like we see Pluto today.

Backward Galaxy

• Distance From Earth: 111 Million Lightyears
• Number Of Stars: Estimated 200 to 400 Billion

Initially called NGC 4622, this galaxy eventually was given the name: “Backward Galaxy.” Why was this? We initially thought spiral arms trailed in spiral galaxies with those arms winding away from the center in the direction of the disk’s orbital rotation. For this galaxy, the outer arms are the leading arms, and the tips of spiral arms point toward the direction of disk rotation. It also has a single inner trailing spiral arm. Basically, it spins backward, which defied the knowledge of the time. Of course, due to this, the galaxy would be given its now infamous name. It is also part of the massive Centaurus Cluster.

Roughly 3 million years before this, the world began to change from the violent hellscape it was for many years prior. It began to slowly cool down, which allowed the first modern mammals to form. That includes some in the sea, but many others began to appear on land. Things like apes and whatnot did not exist at this point, but they were slowly coming after this. If alien worlds in the Backward Galaxy saw the Earth, they’d be seeing an Earth that appeared like it does today. Yet life would be sparse and spread out, likely harder to see.

Sculptor Galaxy

• Distance From Earth: 11.42 Million Lightyears
• Number Of Stars: 22 Known (But Millions Are Assumed Present)

Also known as the Silver Star Galaxy, the more commonly known Sculptor Galaxy is pretty amazing. Astronomers refer to it as a “starburst galaxy.” These are galaxies that are forming numerous new stars, with systems popping up around them. The Milky Way produces roughly 3 million new stars in an Earth year. Yet starburst galaxies like the Sculptor have a star formation rate of 33 times that. You can actually see it with binoculars, as Sculptor is only a little over 11 million lightyears away. Due to many new stars popping up, it might get its name honestly. However, this only helps it to produce more light for us to see it.

We only know of about 22 main stars that we can see. Yet 6 of them have planets, proving alien worlds could be looking at Earth too. What version of Earth are they seeing? Geologically, we’d be in the Tortonian period. This era saw the Messian Event, where lakes dried up. This includes the Mediterranean Sea, which would not fill back up for a long time. Plus, several ice ages began, resulting in the East Antarctic Ice Sheet. If that is not enough, separation slowly began to happen between the human and chimpanzee ancestors. Quite a lot went down roughly 11.5 million years ago.

Ursa Major I Dwarf Galaxy

• Distance From Earth: 330,000 Lightyears
• Number Of Stars: Over 100 Million

Ursa Major I is a dwarf galaxy that is actually a satellite galaxy to the Milky Way, found in the Ursa Major Constellation. This is likely why it is so close at just 330,000 lightyears from Earth. It is fairly new to us as it was only discovered in 2005. It likely took so long because the system is relatively faint and hard to see. Thus, we had to wait for technology to advance. Ursa Major Dwarf II would be discovered in 2006. Both have stars that are likely dying off. We have seen a little over 100 stars and most are around 10 billion years old. Interestingly, 21 of the stars we’ve seen have planets around them with habitable alien worlds.

If they saw Earth as it looked around 300,000 years ago, they would be seeing the Neanderthal group of early humans. They were considered relatively dumb compared to other ancient humans. Yet they were the ones who drew on caves, made incredible early tools, understood fires, developed small societies, and more. We were in the Chibanian period or truly late Middle Pleistocene. While not a technical ice age, glacial temperatures were commonplace for several early humans. Alien worlds would see an icy Earth, with spots of early humans trying not to freeze to death.

Sombrero Galaxy

• Distance From Earth: 31.1 Million Lightyears
• Number Of Stars: Over 100 Billion

We can say that at least the Sombrero Galaxy gets its name honestly. This galaxy certainly appears to look like a sombrero, which is pretty awesome. It is somewhat larger than the Milky Way, roughly 0.3x. Astronomers love to study this galaxy due to it being so close and easier to see. A little over 31 million lightyears away, we’ve been able to find out a lot about it. For example, scientists love to point to its numerous globular clusters. These are spherical, tight collections of stars. The galaxy has about 2,000 of these clusters. It is estimated to have more than 100 billion stars in total, several with planets around them.

What might these alien worlds be seeing 31 million lightyears away? We know this was a period of large extinction, the Grand Coupure to be exact. Most victims were aquatic, which made sense due to the widespread glaciation that took place. What came next was pretty important. Mammals popped up, but more importantly, different types of fauna overall came about. In fact, this was when many of our modern types of flowering plants started to form. In spite of arctic conditions, these plants found a way to last, and continue to survive until today.

Cartwheel Galaxy

• Distance From Earth: 500 Million Lightyears
• Number Of Stars: Several Billion

The Cartwheel Galaxy is quite beautiful for people to see. It is referred to as a “lenticular galaxy.” They fall in between the elliptical and spiral galaxy types. Thus, they have large-scale discs but do not have large-scale spiral arms. These types of galaxies, due to being disc galaxies only, have sadly lost most of their interstellar matter. This means they do not have much new star formation. The Cartwheel Galaxy among other lenticular galaxies has very old stars. This is actually one of 4 galaxies, with Cartwheel being the dominant one. Thus, the others work alongside it as companion galaxies.

This galaxy is about 500 million lightyears from Earth, meaning the alien worlds here are likely seeing quite a crazy Earth. The first animals, period, showed up just 100 million years before this. We would be in the heart of the Cambrian period, one of the most notable in Earth’s history. This is the first we saw of prokaryotes, protists, algae, fungi, and other single-cell organisms. All of which still exist today. Pangea broke apart before this, but some continents remained or came together such as Gondwana. Reefs began to form in our oceans, allowing for even more life to come in the aquatic environment.

Large Magellanic Cloud

• Distance From Earth: 158,200 Lightyears
• Number Of Stars: 30 Billion

While some have often been critical of adding the Large Magellanic Cloud to galaxy lists, it certainly belongs. This is also a satellite galaxy to the Milky Way, and one of the five closest to us. Officially, this is a “magellanic galaxy.” They are special dwarf galaxies that contain one single spiral arm. Of course, we only know they exist due to the LMC discovery. These galaxies are often seen as the intermediate or middle between dwarf spiral galaxies and irregular galaxies. Typically, they’ll orbit larger galaxy formations, just like LMC.

Due to its closeness, we know it contains hundreds of thousands of giant and supergiant stars. Complete with 60 globular clusters, 400 planetary nebulae, and 700 open clusters. Alien worlds here are likely seeing an exciting Earth at just under 160,000 lightyears away. While it is yet another glacial period, we are toward the end of it here. Neanderthals were beginning to phase out as we’d be moving into the first modern humans too. Of course, this period for humans was immense, with hunting taking off, along with the invention of several tools.

Small Magellanic Cloud

• Distance From Earth: 200,000 Lightyears
• Number Of Stars: Over 100 Million

A lot like its cousin, the Small Magellanic Cloud is found right outside the Milky Way. It is the smaller of the two, clearly, and it happens to be further out. Yet they work the same way and look quite similar. It’s true that 200,000 lightyears is still very far away, but it’s close enough for us to see this galaxy with the naked eye. On a clear night, you can look up and likely see it pretty easily. If not, average binoculars could help. There are hundreds of millions of stars here that offer enough luminosity to view it from anywhere on our planet.

Due to being 200,000 lightyears away, it is put in roughly the same time period as the LMC. Any of the alien worlds within this galaxy are going to be seeing a ton of life popping up. Sure, we’re still in a cold period with only small areas where our human ancestors could be. Yet if they stick with Earth for a while, they are going to see it warm up over the next 100,000 Earth years and present something quite impressive. Who knows what might be seen from Earth each day for them during this period in our existence? It is an exciting time in Earth’s history, as life was slowly beginning to flourish.

Lindsay-Shapley Ring

• Distance From Earth: 300 Million Lightyears
• Number Of Stars: Potentially Billions

The Lindsay-Shapley Ring has an incredible story in how it formed. You might be seeing the yellowish center in the image we added, right? It looks beautiful, but this ring actually took that yellowish nucleus as its own. It was part of a normal spiral galaxy, yet the ring took it as its own after it potentially collided with that other galaxy. The ring is 150,000 in diameter and was not always a ring. Thus, when it collided with the other galaxy, it just punched through it. Gravitational forces caused dust in the galaxy to condense, leading to the formation of stars. Then the full expansion happened, leading to the ring forming too.

Our Earth 300 million years ago was going through quite a big change. The first amphibians and reptiles began to form after a large extinction period that killed off 70% of the world’s species just a few million years beforehand. Many of the world’s winged insects began to form in this time. Life burst out possibly due to the highest-recorded atmospheric oxygen level for the Earth. Not just animals came from this, new species of plants and trees came too. This includes coal forests, scale trees, ferns, giant horsetails, and even corals in the seas and oceans.

Sagittarius Dwarf Spheroidal Galaxy

• Distance From Earth: 70,000 Lightyears
• Number Of Stars: Hundreds Of Millions

The Sagittarius Dwarf Spheroidal Galaxy is pretty unique. Astronomers classify it as an “elliptical loop-shaped satellite galaxy,” which is quite the mouthful. Elliptical galaxies are known for offering a crisp, spherical shape that offers a nearly featureless image. While Sagittarius does this, it also happens to be looped more than perfectly spherical. The Milky Way and its gravity might be whose to blame for that. While it is roughly 50,000 lightyears from the center of the Milky Way, we rest near the outer banks. That means it needs another 20,000 lightyears to reach us. They are still one of our closest galaxies.

While we only know of a little over 80 stars, we know several of their stars contain potential alien worlds. If they were looking at Earth, they’d be seeing a really interesting time for us 70,000 lightyears away. Homo sapiens officially began to populate the Middle East. We’d slowly move into Africa over the next few thousand years. This was very late into the Pleistocene too. Oxygen levels were much lower by this point, so a lot of the megafauna became extinct. The Würm glaciation took place in this time, leading to the European Alps becoming glacial.

Virgo Quasar (3C 273)

• Distance From Earth: 2.9 Billion Lightyears
• Number Of Stars: Unknown

While some have called it the Virgo Quasar, astronomers and other scientists simply refer to it as 3C 273. This happens to be the first-ever quasar discovered. The discovery initially took place in the 1950s but would not be confirmed until the 1960s. A quasar is pretty interesting too. They are simply galactic nuclei powered by a black hole. It seems odd that we’d see anything near a black hole, but we did see 3C 273. It’s one of the brightest quasars ever discovered. Due to having a galactic nucleus, it is at least possible alien worlds are within it. However, the presence of a black hole may throw off timelines somewhat.

If alien worlds were looking at Earth from here, they’d see a very young planet. The first known continent formed around this time. That was not Pangea, as that was a supercontinent. We’re saying that this timeframe saw the first landmass continent, period. It is still debated what else took place at this time. Many scientists believe that oxygenic photosynthesis took place at this point. It’s interesting to note that photosynthetic life was retinal-based rather than chlorophyll-based. Thus, the Earth likely looked purple rather than blue and green during this time period.

Hoag’s Object

• Distance To Earth: 612.8 Million Lightyears
• Number Of Stars: 8 Billion

Likely everyone by now knows about the unique Hoag’s Object. It is a galaxy unlike most that we’ve ever come across. Most astronomers have been amazed by it for years. While this is a ring galaxy or a galaxy with a circular appearance, we did not know much more upon its discovery in 1950. Found by Arthur Hoag, he could not decide if it was a planetary nebula or a peculiar galaxy. It’s kind of both, technically. We know this ring, which spans 100,000 lightyears, has roughly 8 billion stars within it. This almost ensures alien worlds are present, but they are over 600 million lightyears away from Earth.

If they saw Earth 600 million years ago, what would they see? Some of the first animals already formed. This came after millions of years being what is essentially a snowball Earth. Multi-celled animals began to flourish at this point, including worms and sponges. Taconic orogeny, or mountain building, began at this time in North America and did not end for another 200 million years. Plus, the Aravalli Range in India’s subcontinent also formed along with the Australian continent. Before Antarctica began to get cold, mountains began to form on its landmass during this time period as well.

Reticulum II

• Distance From Earth: 97,847 Lightyears
• Number Of Stars: Unknown

Reticulum II is one of the few galaxies that are less than 100,000 lightyears from Earth. While scientists did not discover this dwarf galaxy until 2015, it’s actually a pretty old galaxy. It has been very hard to see, which is why it took analyzing images using the Dark Energy Survey. Initially, scientists believed it was a globular cluster but it was far too large for that. The galaxy contains both a blue horizontal and a red giant branch of stars. This means it likely has some very unusual elements and enrichment, as well as high radiation. Some think the uniqueness of the galaxy is due to the collision of two neutron stars.

It is unknown exactly how many stars this galaxy has, we have found five stars with confirmed planets. Thus, alien worlds could be present. It is a little over 97,000 lightyears from Earth. At this point, homo sapiens were beginning to populate the planet. A land bridge eventually formed from modern-day Siberia to Alaska, which resulted in early homo sapiens eventually traveling across it to become the Native Americans we know today. That land bridge went away, sadly. Meaning Native Americans would be isolated from the rest of the world, like indigenous people in Australia and New Zealand.

Medusa Merger Galaxy

• Distance To Earth: 130 million lightyears
• Number Of Stars: 100 Billion+

Medusa Major is an interesting place in our universe. This is an area where there are several interacting galaxies. It is hard to keep up with them all so we won’t even go there. Over 500 lightyears of space exist in the center, often referred to as the Eye of Medusa. While it is the central, gas-rich region of Medusa Merger, it is also the place where extreme star formation has been taking place. That results in stars forming relatively close, making the local galaxies interact more.

With this area being 130 million lightyears from us, we know alien worlds will not see the best Earth possible. Yet they will see one in major development. This might be the Late Cretaceous period, but it’s geologically known as the Cenomanian. Around this point, an anoxic recent happened. That is a period in which a lot of the Earth’s oceans began to lose oxygen. Remember, water is H2O. Without oxygen, it is simply hydrogen and thus toxic. That led to a nearly worldwide extinction event for several aquatic/marine species. It is now referred to as the Cenomanian-Turonian Boundary Event.

Mayall’s Object

• Distance From Earth: 450 Million Lightyears
• Number Of Stars: Classified As Emerging Galaxy (Star Number Uncertain)

A peculiar galaxy, Mayall’s Object is technically the result of two different galaxies colliding at some point within the Ursa Major constellation. It was discovered by Nicholas U. Mayall, resulting in its name. The galaxies that collided seemed to do a lot of damage. Since the galaxy is ring-shaped with a tail emerging, it is believed a shockwave must have taken place. That would have drawn matter into the center, leading to the emergence of the ring we see today. It is possibly one of the most beautiful collisions we’ve ever seen. Though uncertain, alien worlds are thought to be present here.

If so, they’d see the Earth 450 million years in its past. The Ordovician-Silurian Extinction took place at this point. Most then living marine species died out. Second, the Old Rest Sandstone Continent began to form. This came as a result of Baltica and Laurentia. While Baltica is merely a paleocontinent, Laurentia would go on to form most of the ancient geological core of North America. Laurentia was often its own continent or supercontinent. This led to run-ins with others. Thus, part of it would go on to form a large portion of Greenland and the northwestern portion of modern-day Scotland.

Ophiuchus Galaxy Cluster

• Distance From Earth: 390,000 Lightyears
• Number Of Stars: Untold Millions (We’ve Seen 37 So Far)

The Ophiuchus Galaxy Cluster happens to form the far wall of the Ophiuchus Void. Although, it is also connected, at least in a filament, with both the Pavo-Indus-Telesopium and Hercules Superclusters too. It resides in the center of the cD cluster, which has roughly two more galaxy clusters and four more galaxy groups. Plus, several more field galaxies too. It is like they have teamed up to have their own United Federation of Planets! The cD Galaxy of NeVe 1 is a site in this supercluster that erupted, triggered by an ejection of ~270 million solar masses from the supermassive black hole in NeVe 1.

It is the largest explosion in the universe since the Big Bang, and opened up a 1.5 million lightyear wide cavity in the Ophiuchus Supercluster! This is scary to think about, as Ophiuchus is just 390,000 lightyears away. On Earth at that time, we saw the Hoxnian Interglacial period, which led to the true formation of the British Isles. Humans then began to settle there after a while. However, during this period in history, the Homo Sapien had not come about. Rather, it was our Neanderthal ancestors that popped up at this point.

Triangulum I Galaxy

• Distance From Earth: 3 Million Lightyears
• Number Of Stars: 40 Billion

Among the “local group” of full galaxies, Triangulum I is the third largest. In fact, it is considered the furthest universal body that can be seen with the naked eye. Roughly 3 million lightyears away, it is believed to be one of Andromeda’s satellite galaxies. Yet some scientists think it’s actually coming out of a previous interaction with another galaxy. Then as it reached the massive Andromeda and its gravitational pull, it had no choice but to become a satellite. Interestingly, Triangulum I has an H II nucleus. Which is simply a nucleus made of ionized atomic hydrogen.

If alien worlds viewed Earth from here, they’d be seeing some changes. First, they would be seeing the North Pole start to become glacial. We’d also begin to see some animals pop up that are often assumed to be part of the dinosaurs. Species like the saber-toothed tiger and wooly mammoth were both common in this timeframe. Both even lived long enough to come in contact with early humans. Neither are dinosaurs, obviously, but they are still part of the prehistoric species list. Not only this, but other megafauna popped up in this time, including several much larger plants.

Canis Major Dwarf Galaxy

• Distance From Earth: 25,000 Lightyears
• Number Of Stars: 1 Billion

Noted as an irregular dwarf galaxy, many have disputed the idea of it holding the “galaxy” tag for a while. This is why some actually refuse to call it that and instead use the name “Canis Major Overdensity.” What everyone agrees on is that it possesses a ton of red giant stars. These stars are naturally in their latter lifecycle, meaning this area will eventually be home to a large percentage of supernovas or they could be hijacked by others, such as vampire stars. All in all, in spite of the red giant stars, Canis Major is home to roughly a billion stars.

It is also just about 25,000 lightyears away, making it very close to us. About 10,000 years before this is when our modern calendar takes place. It is also when the extinction of the Neanderthals came to pass. A few thousand years after this is when the oldest cave paintings were traced back to. This is at least one of the last glacial periods, so alien worlds would likely see a cold planet but nothing compared to beforehand. While animal and society changes are incredibly different, this is the closest version of “Earth” itself that alien worlds could view.

Malin 1 Galaxy

• Distance From Earth: 1.19 Billion Lightyears
• Number Of Stars: Unknown (Trillions Estimated)

Malin 1 is the largest spiral galaxy science has ever discovered as of this writing. We do not have a lot of information on the galaxy due to it being a little over one billion lightyears away from us. Most of our images are even blurred, making it hard to really get an idea about their star count. Due to the distance, the light it emits is not very bright. Weirdly, we assume the distance is the problem entirely. However, we’ve seen other galaxies just as far away that are much brighter. This is why some scientists naturally assume Malin 1 has a lot of older stars that are losing their luminosity.

If alien worlds in this galaxy looked at Earth, they might scoff a bit at what we looked like to them. The first known plants came to be just a few million years before the 1.19 billion mark. Shortly after, the first supercontinent, Rodinia, formed that would be huge for the development of future species. This means the landmass we’d later see, especially a lot of the glacial periods, has not happened yet. The Earth was still very much in a very hot, dense period. It would be another 200 million years before we saw the snowball Earth. Something almost opposite to the Earth from even 1 billion years ago.

Messier 87 Galaxy

• Distance From Earth: 53 million Lightyears
• Number Of Stars: 1 Trillion+

While Messier 87 is a supergiant galaxy with more than one trillion stars, it is seemingly in a backyard compared to the distance of other galaxies. It’s a little over 50 million lightyears from Earth. Which is pretty close compared to other galaxies out there. Scientists used this closeness to their advantage a short time ago. The galaxy has a supermassive black hole at its center, like many other galaxies. Scientists managed to capture an image of this black hole, the very first image of a true black hole ever! Their black hole happens to be 6.5 billion times the mass of our sun, which is crazy to think about.

Being roughly 53 million lightyears from us, alien worlds present there would be seeing the Earth in one of its best periods of change. India collided with Asia, leading to the formation of the Himalayas. The Azolla Event happened around this time as well. This was a period in which freshwater fern Azolla bloomed in the Arctic Ocean. The Azolla sank to the seafloor, becoming incorporated in the sediment there. That led to carbon dioxide reducing, taking away the “Greenhouse Earth.” Palm Trees and amphibians could now properly live at the poles. However, the North and South Poles would turn glacial in the “Icehouse Earth.”

Cosmos Redshift 7

• Distance From Earth: 12.9 Billion Lightyears
• Number Of Stars: Unknown

The Cosmos Redshift 7 Galaxy is one of the oldest galaxies astronomers have ever discovered. It is believed to have formed roughly 800 million years after the Big Bang took place. While it randomly got its name from soccer legend Cristiano Ronaldo, the two do not really have anything in common except the number. CR7 is a high-redshift, Lyman-alpha emitter galaxy. In simple terms, this means it is a distant galaxy that emits Lyman-alpha radiation from neutral hydrogen. CR7 also increases the wavelength of electromagnetic radiation while reducing its frequency. All of this then combines with photon energy.

What would alien worlds see if they looked in our direction? While they might have advanced equipment that we could not fathom, if they did not get closer to us then they’d never know we existed. The Earth did not come about until just under 5 billion years ago. However, our entire solar system did not exist before that time roughly. If that is not enough for you, the entire Milky Way galaxy did not form until 14 billion years ago. Thus, CR7 worlds would be seeing a slowly forming galaxy that would not include us for over ten billion years!!

Butterfly Nebula

• Distance From Earth: 3,000 to 6,000 Lightyears
• Number Of Stars: 1

The Butterfly Nebula is technically within the Milky Way and not a galaxy unto itself. However, it almost seems like its own galaxy due to its appearance. Scientists claim it is the most complex planetary nebulae ever discovered. With only one central star, it has to emit extreme heat to allow for such beautiful light to be seen. It is estimated to be one of the hottest stars ever discovered, with a surface temperature of 250,000 degrees Celcius or 450,032 degrees Fahrenheit. The interesting part? The star is a White Dwarf! The Hubble Space Telescope discovered it in 2009, and scientists were blown away.

The possible alien worlds here are likely seeing a developed Earth being between 3,000 to 6,000 lightyears away. Societies had already formed, along with several languages on top of early writing. The Pyramid of Giza among other man-made structures from the old world was built in this period. While several periods such as the Bronze and Iron Age happened during this period, the planet itself did not change massively on a geological end. However, several animals popped up or went extinct in this timeframe. Mankind was also a bit smaller than it would go on to become.

Where do we find this Stuff? Here are our Sources:

National Aeronautics & Space Administration (NASA)

European Space Agency (ESA)

National Science Foundation (NSF)

Public Broadcasting Company (PBS)

Cornell University

University of California – Berkley

University of California – Riverside

Cambridge University

California Institute Of Technology

University of Hawaii

New York Times

Britannica

Slate

Live Science