150 Cool Space Facts: The Ultimate Guide To The Universe


Have you ever looked up at the night sky and caught yourself wondering how many stars are there?

Or how many people have been on the Moon? How long did they stay?

Maybe you want to know what is the biggest, or fastest, thing we discovered so far?

Do you know which man-made object is currently farthest from Earth?

Space is really, really big. (“Not as big as yo mama!” is heard somewhere in the background). Naturally, that means that there is a mind-boggling amount of interesting and awe-inspiring stuff that we have discovered about it.

Some of the facts you can find here are so unbelievable, you could almost swear that somebody’s messing with you!

But I assure you, we are not. The universe is crazy enough that it really doesn’t need our help in that department.

Intrigued? First, let’s crunch some numbers and talk about size for a bit:

Some general facts about the universe

1. Light year is a measure of distance, not time. It is the distance that light travels during one Earth year ( The speed of light is 300,000km/s, which means that this is a very, tremendously, amazingly huge distance of over 9.5 trillion km)

2. AU, or astronomical unit is the distance between the Sun and the Earth, and it measures 8 light minutes and 19 light seconds, or 149.597 million kilometers in humans-can-achieve-it units.

3. To top it off, a unit called parsec is even longer than a light year. Measuring 3.26 light years, it is a function of an astronomical unit and a parallax angle of 1 degree. Its name is derived from “parallax of one arcsecond

4. The biggest known star currently is UY Scuti, a bright red supergiant, located 9500 light years away in the Scutum constellation. It is more than 1,708 times the size of the Sun.

If UY Scuti was placed in our system instead of the Sun, it would engulf everything up to the orbit of Saturn.

See this video of size comparison:

5. The most massive star, and one of the hottest that we know of, is the RMC 136a1, with the mass of 315 Suns and the temperature of over 50000 K! It is just a brisk walk away of 163,000 light-years, sitting in the Large Magellanic cloud.

6. Universe is estimated to be 13.82 billion years old.

Even though we know its age we don’t really know its size since it’s always expanding, so the light actually didn’t have time to reach us yet from the furthest reaches of space.

Current estimates, based on a phenomenon called redshift, are that it is at least 46 billion light years across.

This image, captured with the NASA/ESA Hubble Space Telescope, is the largest and sharpest image ever taken of the Andromeda galaxy — otherwise known as M31.
This image, captured with the NASA/ESA Hubble Space Telescope, is the largest and sharpest image ever taken of the Andromeda galaxy — otherwise known as M31.

7. Galaxies can collide. In fact, our own milky way is due a collision with Andromeda galaxy. Not to worry though, this is going to happen in over 4 billion years from now, and even when it happens, galactic distances are so vast that the chances of a star or a planet hitting each other are almost non-existent.

8. There are over 100 billion galaxies in the universe, by current estimates made by Hubble space telescope, but that number is probably to rise as we develop better telescope technology.

UPDATE: The newest estimates made by a computer simulation suggest that there are over 500 billion galaxies in the universe!

9. There are over 300 billion stars in our galaxy, the Milky Way. In the observable universe the estimate is that there are 70 billion trillion (7 x 1022) stars. Don’t even try to wrap your head around that number.

10. A popular comparison that can illustrate these numbers is this: There are more stars in the universe than there are grains of sand on all the beaches and deserts on Earth.

Tweet this space fact:

There are more stars in the universe than there are grains of sand on all the beaches and deserts on Earth. Click to Tweet

11. Milky Way is our home galaxy. It’s a spiral galaxy, with the supermassive black hole in its center and it spans between 100-200 thousand light-years. (It’s kinda hard to measure such distances, so the current estimates are really rough).

12. Milky Way has two major spiral arms that start at the central bar of stars, and slowly taper off. Our Solar system is located in one minor spiral arm called the Orion arm.

This diagram shows the structure of the Milky Way galaxy, including its major and minor spiral arms. Our solar system is in the Orion Spur (shown below the yellow bar that marks the galaxy's center), a relatively short arm that contains some of the brightest stars in our night sky.
This diagram shows the structure of the Milky Way galaxy, including its major and minor spiral arms. Our solar system is in the Orion Spur (shown below the yellow bar that marks the galaxy's center), a relatively short arm that contains some of the brightest stars in our night sky.
Via StarDate.org

13. The biggest galaxy is over 30 times bigger than our own modest Milky Way. The IC 1101 is a supergiant elliptical galaxy and it spans over 5.8 million light years, with more than a 100 trillion stars that call it home.

The Largest Galaxy In the Known Universe: IC 1101
The Largest Galaxy In the Known Universe: IC 1101.
Via Futurism.com

14. Galaxies come in different sizes, but also different shapes.

The three main types of galaxies are elliptical, spiral and irregular. The Hubble classification is a bit more complex – Elipticals, spirals, lenticulars and irregulars, of which each category has subcategories.

15. The first spiral galaxy we discovered, besides our own, is the Whirlpool Galaxy (M51). It is estimated to be 23 million years away from the Milky Way.

Whirlpool Galaxy (M51)
Whirlpool Galaxy (M51).
Via Wikipedia.org

16. Measuring distances to galaxies is tricky. We try to find a single star in that galaxy and measure the distance to it.

If the galaxy is too far away to distinguish individual stars, astronomers find supernovae, which are much brighter than ordinary stars, and measure that distance.

I’ll let you sit on all those numbers for a while.

I dont know gif

Think about it:

We can’t even begin to comprehend most of these numbers and sizes. There is literally nothing in our everyday life that we can compare it to.

Ok, let’s move a bit closer to home now.

If we are to scale back from these ridiculous vast galactic distances and numbers, we will find a cozy little system with a little yellow Sun smack dab in the middle of it.

Then, if one were to count, one, two, three, there we are! The third rock is where we call home.

Here’s some fun and interesting space facts about our home system:

The Solar system facts

17. There are 8 planets in our solar system. In order, from the closest to the Sun to the furthest, they are:

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Solar system illustration with planets and Sun

18. For a long time the little, distant Pluto was listed as a planet, but it has its own classification now: a dwarf planet.

19. The planets are separated into the planets of the inner solar system, and the outer system. There is a huge difference between these planets, both in their size and their composition. The planets of the outer system are known as the giant planets (or Jovian planets), while the inner planets are called the terrestrial planets.

20. The inner planets are fairly small, with the Earth being the biggest among them. They are pretty dense, with a rocky composition, iron-nickel cores and few or no satellites. Each of these has some sort of surface features, such as impact craters, volcanoes and canyons.

21. Revolution is what we call one complete circle that a planet makes around the Sun, and rotation is a single full circle around the planet’s axis. Earth’s rotation is what we call a day, and its Revolution is one year.

22. Mercury is the planet closest to the Sun. It has a year of 88 days, and a day that lasts almost 60 Earth days. On the side that is facing towards the Sun it has a scorching surface temperature of over 700K (423 C), but on the other side it’s surprisingly freezing with temperatures below 0 C.


23. The reason for this huge temperature difference is because of Mercury’s long day. The dark side is so cold that there are even hints that there might be actual traces of water ice.

24. Even though the Mercury is the planet nearest to the Sun, Venus is actually the hottest. That is because Venus has an extremely dense carbon-dioxide atmosphere, which creates the strongest green-house effect known to man.

25. The pressure on the surface of Venus is as high as it is at the depth of 1 kilometer in Earth’s oceans. The temperature is at least 735 K (462 °C), and its surface features look as what we normally think Hell looks like.

26. The Earth is actually closest to the Sun during January and farthest during July. The seasons we experience are due to the tilt of the Earth’s axis, which makes certain areas get more sunshine at the different parts of its revolution.

27. Earth’s orbit starts at an altitude of 2000 km.

If we were to build a staircase from the sea level to orbit, it would take two weeks to climb.

28. The only natural satellite that orbits the Earth is Moon. It is one of the largest and densest satellites, but it doesn’t have any atmosphere. The Moon is in synchronous orbit around the Earth, which means that we always see the same side of the Moon.

29. Distance to the Moon from Earth is 384,402 km (238,856 mi).

You could fit all the planets of our system in there, with room to spare.

Earth-Moon distance to scale
Earth-Moon distance to scale.
Via Wikipedia.org

30. Moon gravity is 1/6 of Earths.

If there was a pool on the Moon, swimmers could jump out of the water like dolphins, launching themselves more than a meter high.

31. There is no dark side of the Moon. The side that we don’t see is illuminated by the Sun as often as the side that we face.

32. Every year there are at least 2 lunar (Moon) eclipses, but it can happen that there are no solar eclipses. While the solar eclipses are rare, they still occur at least once every 18 months. The reason why we feel it’s much rarer than that is because they can be seen only from a fairly small area on the Earth.

33. Lunar eclipse happens when the Moon passes into the Earth’s umbra (shadow), which means that Earth is blocking the sunlight that usually falls on the Moon. This event can happen up to four times per year.

34. During the lunar eclipse, we still see the Moon, but it has a weak reddish tint. We sometimes call it the Blood Moon.

Super Lunar Blood Moon Eclipse
Blood Moon during the lunar eclipse.

35. A Blue Moon is not really blue. It’s just a name for a second full moon that happens in one month, every now and then.

36. The solar eclipse occurs when the Moon passes right in front of the Sun, and it casts its shadow on Earth. The area of Earth that is in the Moon’s shadow is the only part on Earth where that particular eclipse can be seen. This is the only time when we can see the Sun’s corona from the Earth.

37. Mars is the fourth planet from the Sun, and it is the second smallest planet in our solar system. It has much weaker gravity than Earth:

with the gravity of 38%, a 100 kg person would weight only 38kg on Mars!

38. The red planet is also known for having some of the most impressive surface features. It is the home of Olympus Mons, the largest volcano in the solar system, and Valles Marineris a vast network of Canyons, second only to the rift valleys on Earth.

39. Olympus Mons is almost 22 km high, more than 2.5 times as tall as our highest mountain Mont Everest.

Vertical comparison of Olympus Mons with Mount Everest (shown sea-level-to-peak) and Mauna Kea on Earth (measurement is sea-level to peak, not base to peak).
Vertical comparison of Olympus Mons with Mount Everest (shown sea-level-to-peak) and Mauna Kea on Earth (measurement is sea-level to peak, not base to peak).
Via Wikipedia.org

40. Mars has two tiny moons: Phobos and Deimos. It is believed that these moons are actually asteroids that have been caught up in the Mars’s asteroid field. The names of these satellites mean Fear and Dread, which is very suitable for the companions of the roman god of war.

41. The outer planets are Jupiter, Saturn, Uranus and Neptune. These humongous planets are also known as Jovian planets, in honor of Jupiter, the biggest of them. These planets together make up 99% of the mass that is orbiting the Sun.

42. Jupiter and Saturn are made of primarily hydrogen and helium, while the Uranus and Neptune have more icy components – a reason why these two are often called the ice giants.

43. Each of the outer planets has rings around it, but only the Saturn’s’ are visible to us from Earth. These rings are composed of small chunks of ice and rock, and they are surprisingly thin (less than a kilometer thick).

If Saturn’s rings were a meter long, they would be 10000 times thinner than a razorblade.

In this simulated image of Saturn's rings, color is used to present information about ring particle sizes in different regions based on the measured effects of three radio signals.
In this simulated image of Saturn's rings, color is used to present information about ring particle sizes in different regions based on the measured effects of three radio signals.

44. The Saturn has seven distinct rings. It is unknown why these rings are so prominent, but it is believed that it has something to do with the large number of moons that orbit Saturn. The rings have a radius of about 250000 km.

If one was to drive a car on one of the Saturn’s rings, at the speed of 100 km/h, it would take over 14 weeks to finish one lap.

45. The biggest moon that is orbiting Saturn is Titan. It is the only natural satellite that has dense atmosphere, mostly composed of nitrogen. Due to its low surface temperature of 94 K (−179.2 °C), it has lakes of methane, which makes it the only celestial body that we know of that has surface liquid, besides the Earth.

46. Jupiter is the biggest planet in our system, over 300 times bigger than Earth. It is so big that it is sometimes considered a failed star.

In fact, it emits more energy than it receives from the Sun.

47. Jupiter has a huge perpetual storm that rages in its upper layers, known as the Great Red Spot. It is so big that the whole Earth could fit into it. Gas giants have a very turbulent atmosphere, so storms such as this are fairly common. True enough, both Neptune and Saturn have their own spots, called the Great Dark Spot and the Great White Spot, respectively.

Jupiter's Great Red Spot compared to Earth
Jupiter’s Great Red Spot is a cyclone that’s presently about 1.2 times as big as Earth. As recently as 1979, it was twice Earth’s diameter as illustrated here.
Via Michael Carroll

48. Jupiter has 67 natural satellites (or moons), the highest number of all the planets in the solar system. The largest and most famous are IoEuropaGanymede and Callisto.

49. Pluto is not the only dwarf planet in our system. Besides Pluto there are four other dwarf planets in our system: Ceres, Haumea, Makemake and Eris.

50. All the dwarf planets, except Ceres, are called the Plutoids in honor of the ex-planet Pluto. This designation is reserved for all the dwarf planets that orbit the Sun beyond Neptune.

51. The definition of a planet has been set at an astronomical conference in Prague, Czech Republic, in the summer of 2006. The new definition states that the planet:

  • Is in orbit around the Sun.
  • Has sufficient mass to assume a nearly round shape.
  • Has cleared the neighborhood around its orbit. (This means that there are no other celestial bodies of similar size in its orbit path.)

52. The main difference between a planet and a dwarf planet is that the dwarf planets have not cleared their neighborhood. Dwarf planets tend to orbit in zones shared with similar objects that can cross their path around the Sun, such as the asteroids. Dwarf planets are also smaller than the planet Mercury, the smallest planet.

53. There is an asteroid belt that orbits Sun between Mars and Jupiter. It is believed that these asteroids are remnants of a planet that failed to form during the solar system creation.

Asteroids can vary in size from a few meters to hundreds of kilometers.

54. Contrary to the movies and popular belief, the asteroid belt is fairly easy to maneuver in a spacecraft. Even though there are over a million asteroids estimated in the belt, they populate such a huge area of space that the distances between individual asteroids are at least several kilometers.

55. The crown of the asteroid belt is Ceres, recently classified a dwarf planet. Ceres has a radius of around 950km, and strong enough gravity that it pulled itself into a roughly spherical shape, granting it the almost-planet title.

56. The solar wind is a combination of particles, mostly ionized atoms from the stars corona, and magnetic fields produced by the star. It bathes our planet constantly, and the radiation would be deadly, if we were not protected by Earth’s magnetic field.

57. The area behind Neptune is called the Kuiper belt. It is a disc shaped region of comets, asteroids and dwarf planets, including Pluto. There are estimated thousands of bodies larger than 100 km and trillions of comets. Even the big bodies are not typical asteroids, but frozen liquids and gasses such as methane, ammonia and water.

58. Comets are space snowballs, composed of frozen water and gasses, rock and dust. The nucleus of a comet is usually not bigger than 10 km, but as the comet approaches the Sun and the frozen gases begin to evaporate, the nucleus can expand to over 80 000km.

59. The tail of a comet appears when it gets close enough to Sun and starts to melt. It is caused by the radiation pressure from the Sun which “blows” away some of the matter from the evaporating comet nucleus, which is why the tail always faces away from the Sun. These tails can be even millions of kilometers long.

60. The earliest recorded comet is the Halley comet, which was first observed in ancient china in 240 B. C. It makes one orbit around the Sun every 75 years.

Famous writer, Mark Twain, was born on the year when the Halley comet passed, and died on the year when it went by again. Both times he had missed it.

61. Exoplanets are the planets we found that are outside our solar system. These extrasolar planets are very hard to detect, and only in the past 10 years or so have we been able to regularly find new ones. We have so far discovered over 2000 exoplanets.

62. The smallest recorded exoplanet is twice the size of the Moon, while the most massive has almost 30 times the mass of Jupiter. This gas giant is so big that is uncertain whether it’s a planet, or a brown dwarf (the smallest type of a star).

The never-ending curiosity of the human race made as achieve an amazing feat:

We have been to space!

In fact, as you read this, there are several people that are floating up there, and a whole bunch of our rockets and satellites.

But our road to the stars is still a long and thorny one, and it’s going to take quite some time before we can visit other systems.

Here is some of the stuff we did achieve (continue on next page):

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