How do you condense the cosmos into knowable facts? This guide on cool and interesting astronomy facts comes pretty close! Discover mind-blowing and fascinating titbits on our Solar System, Milky Way Galaxy, and the universe on the grandest scale.
Sunny Solar System
The Solar System is our humble abode in the great cosmos. Planets, dwarf planets, comets, and asteroids all orbit the Sun in a neighbourhood that stretches some 2 light years across.
- Mercury is not such a hot shot: Mercury orbits closer to the Sun than any other body, making it a hostile and sweltering environment. Yet the title for hottest planet goes to Venus, where the thick atmosphere traps in all the heat. Nevertheless, Mercury can get as hot as 427°C, so the last thing you would expect to find there is ice. NASA’s MESSENGER spacecraft stumbled upon exactly that. Mercury is tidally locked to the Sun, meaning it takes the same amount of time to rotate on its axis as it does to fully orbit the Sun. The result is one side of the planet is always bathed in hot sunlight, while the other half remains permanently dark and cold. The ice was found at the planet’s North Pole in craters which never receive any sunlight, and is thought to originate from comets.
- Moonless Worlds: Pluto is so tiny it was declassified as a planet (there were other grounds for its demotion too). Even this diminutive world has natural satellites. Most of the planets in the Solar System, and even some dwarf planets have moons. This makes it a strange fact that Mercury and Venus do not have their own. Astronomers have not solve the mystery of these moonless worlds, but do have evidence to suggest Venus may have had a moon in the past.
- Mars on Earth: The early Solar System was a hostile and destructive place. Massive asteroids regularly crashed into planets in devastating impacts. When such events occurred on Mars, Martian rocks were ejected into space. Most of the debris and rocks would have simply landed back on the planet’s surface, but some were also flung into space and landed right here on Earth. These Martian meteorites are called SNCs (Shergottites, Nakhlites, and Chassignites depending on the composition). Analysing SNCs shows they are identical to samples collected from Mars by NASA’s Viking space prober.
- Jupiter’s Mammoth Ocean: Earth may be the blue planet, but the Jupiter technically has the biggest ocean. The Jovian ocean is not one of water, but of metallic hydrogen. The planet’s composition and mass results in extremely high pressures that make hydrogen act as a liquid. Jupiter does not only have the largest ocean of any Solar System planet, but also the deepest ocean. Computer models show that the ocean is possibly 40 000 kilometres deep.
- Rings of Mystery: Saturn’s rings are the standout feature of the Solar System; a real wonder to behold even through small telescopes. Their mysterious origins make the rings even more fascinating. Scientists are not sure if Saturn’s rings are old or new. Some theories suggest that the rings are 4.5 billion years or the age of the Solar System, having formed from left over debris of the solar nebula. The planet’s great mass would have acted on the rings and prevented them from coalescing into a moon. Other models leave open the chance that the rings could be as young as 100 million years, formed by an icy moon that was torn apart by the planet’s gravity.
- Chilled Uranus: Just as Mercury is the closest planet to the Sun but not the hottest, Neptune is the furthest major planet from the Sun but not the coldest. Neptune is 4.5 billion kilometres from the Sun and Uranus is only 2.88 billion kilometres from the Sun, but Uranus still beats out its giant neighbour as being the iciest major planet. The average ‘surface’ temperature on Uranus is -197.2 ° C, but it can dip down to as low as -226° C. The planet gives off less heat than it absorbs. Whereas Jupiter and Saturn have hot cores that radiate infrared radiation, Uranus has a cool core that does not radiate much energy.
- Supersonically Stormy: Neptune is home to some of the most extraordinary weather. High wind speeds on Earth can cause extreme devastation. The highest recorded wind speeds on Earth were in Australia in 1996; a gust of 408 kilometres per hour that was associated with a cyclone. Neptune’s winds make this look like child’s play as they blow at more than 1770 kilometres per hour. That is faster than the speed of sound on Earth at sea level. Astronomers are a little stumped at what could be powering these high wind speeds, as the planet lies too far away from the Sun for it to cause such strong winds.
- USA – Bigger than a Planet: Pluto may not technically be a planet, but it is still hard to believe that it is dwarfed not only by other bodies in the Solar System, but also by countries on Earth. The diminutive world measures 2371 kilometres in diameter, according to data gathered by New Horizons space probe in 2015. Meanwhile, the United States is 4700 in diameter. No wonder Pluto was demoted!
- The Sun is Our Home: It seems obvious to say that the Sun is our home since we belong to the Solar System, but it does go a little deeper than that. We actually live in the Sun… while, within its atmosphere at least. The outer atmosphere is called the heliosphere, and is thought to extend 6 billion kilometres – far beyond the outer major planets and out to the Oort Cloud.
- Precious Elements: You wouldn’t think that the sodium in your table salt or the calcium in your veggies and milk is precious. The reality is that the vast majority of all elements on Earth are rare including the sodium, calcium and other elements such as silicon, magnesium, sulphur, nickel and aluminium. While we do find these elements scattered across the universe, they are the exceptions. Hydrogen is the most abundant element in the universe, followed by helium. All other elements are merely trace elements when compared to the amount of hydrogen and helium present.
- To Infinity and Beyond: Mankind has some pretty amazing achievements under its collective belt, and one of the first examples that springs to mind are the Voyager Voyager 1 and Voyager 2 were both launched in 1977 to spend several years exploring the Solar System and providing invaluable information before ultimately setting off into deep space. Voyager 1 is now the furthest made man object in space, having completely left the Solar System in 2013 and entering interstellar space. The spacecraft also took the iconic photographic of Earth from the edge of the major planets titled The Pale Blue Dot.
- Far Reaches of Space: On that note, what exactly do we mean by edge of the Solar System, and by Voyager 1 having left the Solar System? Pluto was once the limit of what we knew about what orbits the Sun, but more and more Trans-Neptunian Objects (TNOs) and Kuiper Belt Objects (KBOs) have been discovered with each year. These objects located at the far reaches of the Solar System can be 1,000 times farther away than Pluto. This includes the Oort Cloud, a reservoir of comets thought to lie in a halo about half a light year to two light years away from the Sun.
Magnificent Milky Way
The Milky Way Galaxy is home to our Solar System, as well as a myriad other stars, planets and extraordinary bodies.
- The Centre of It All: The centre of our galaxy is a busy hub of activity. The huge galactic bulge that is the heart of our galaxy is packed with stars, gasses and dust. Also tucked away at the galaxy’s centre is a supermassive black hole called Sagittarius A* (pronounced Sagittarius A star). The Sun lies approximately 25 000 – 30 000 light years out from the central black hole and takes about a quarter of a million years to make one revolution around the Milky Way.
- On the Heavy Side: Calculations show that the Milky Way is between 100 to 400 billion times the mass of our Sun, with upper estimates placing it at over 900 billion solar masses. This is no surprise considering that our galaxy contains well over 250 billion stars, and not forgetting all the material that orbits the stars as well as interstellar dust and gasses. Despite the enormity of the Milky Way, it is considered an average sized galaxy. The largest known galaxy, IC 1101, contains an estimated 100 trillion stars, while dwarf galaxies like the Small Magellanic Cloud contain as little as only 10 billion stars. Revelations on the size of the Milky Way are important as it helps determine the amount of ordinary matter compared to dark matter in our galaxy.
- Funny Looking: The Milky Way is a barred spiral galaxy with a disk spanning over 150 000 – 200 000 light years across. You would see a central bulge encompassed by four spiral arms wrapping around it if you viewed the galaxy from above. There is a bar across the galaxy’s central region, two major arms that extend from the bulge, two minor arms, as well as two spurs (minor structures). The Solar System lies within one of these spurs (called the Orion Arm) 25 000 – 30 000 light years away from the centre. The disk is actually warped rather than flat, which probably has to do with the Large Magellanic Cloud and Small Magellanic Cloud (smaller galaxies that orbit the Milky Way) engaged a sort of gravitational tug of war on the Milky Way’s gas and dust, and possibly dark matter.
- Not Born this Way: It is tempting to assume that the Milky Way has always been as it is, but there would have been a time when it as certainly less massive and sizable than it is now. The Milky Way actually got its current shape and size by cannibalizing smaller neighbouring galaxies, and it continues to do so. In fact, it is currently stealing stars and matter from the closest dwarf galaxy to us, the Canis Major Dwarf Galaxy. Past victims include the Sagittarius Dwarf Galaxy.
- No Spring Chicken: It can be tempting to think of the universe as being much older than anything we are so familiar with, but our very own galaxy is surprisingly well on in years. The current age of our universe is 13.8 billion years old, and there is evidence to show that some of the oldest objects in the Milky Way are 13.6 billion years. Of course, there isn’t really an even distribution of how old everything is in the galaxy. The oldest stars found in globular clusters are over 13 billion years old, whereas the disk and bulge of the Milky Way are likely only 10 – 12 billion years old. New stars are also constantly being formed.
- Community of Galaxies: The Milky Way is part of a larger network of galaxies. The Milky Way, its satellite galaxies the Large Magellanic Cloud and Small Magellanic Cloud, the Andromeda Galaxy and a sprinkling of about 50 other neighbouring galaxies form a galactic cluster known as the Local Group. The Local Group is a small community that belongs to a bigger structure comprised of several galaxy clusters called the Virgo Supercluster. The Virgo Supercluster extends for approximately 110 million light years in diameter. Despite its incomprehensible size, the supercluster itself is thought to belong to an even grander structure known as Laniakea.
- Racing Onward: Cosmic Microwave Background (CMB) radiation is the left over radiation of the Big Band that permeates the universe. CMB radiation was integral evidence for the Big Band theory and is also a perfect reference point for determining the velocity of large objects such as galaxies and galaxy clusters. Our Local Group is moving at some 600 kilometres per second which adds to a head spinning 2.2 million kilometres per hour relative the CMB! This is another excellent example of how everything is truly relative as we speed along on our cosmic journey.
- Dusty Not Dirty: Stating that gas and dust are the foundation of our galaxy would not be far off from the truth. Dust and gas make up 10 – 15% of all the visible matter that we see in our galaxy, while the rest is generally compromised of stars and their systems. There is so much dust in the Milky Way that we can only see about 6000 light years into the galaxy’s 150 000 – 200 000 diameter disk in the visible spectrum. The plentiful dust obscures the light of countless stars as we only ever see about 2500 stars on best nights. You can even see this dense band of dust across the sky on a very dark night from the right location. We can of course see further into our galaxy and get a fuller picture of the Milky Way by using specialized instruments to make observations in X-ray, gamma ray, microwave and infrared.
- Teaming with (Possible) Life: It is natural not to want to be alone, and so it comes as no surprise that astronomers have spent decades searching the galaxy for life on other planets. It is a real consideration considering the billions of stars and exo-planets our galaxy hosts. Scientists refine the search by scouring the galaxy for so called “Goldilocks Planets”, planets that are not too hot or cold, but just right for life. Such a planet lies in the habitable zone of its sun system. The planet would also be home to the right combination of chemical compounds.
- Drunk on Clouds: There is a giant cloud of alcohol in a vast molecular cloud of dust and gas near the centre of the Milky Way called Sagittarius B. The cloud of alcohol is 150 light years across in diameter and contains a billion billion billion litres of alcohol. It isn’t all fun and games: the vinyl alcohol found in the cloud is actually an important molecule in the formation of life-forming substances.
Not-so-unknowable Universe
The cosmos is all of space, time, energy and matter. Our universe formed 13.8 billion years ago and continues to expand. Cosmologists seek to provide evidence to some of life’s greatest mysteries, and open up many doors to even greater questions.
- Look at the Beginning: The universe makes itself visible in the most curious ways. We can see the afterglow of the heat of the Big Bang in Cosmic Microwave Background radiation: the remnants of an extremely hot soup of hydrogen plasma and gamma ray bursts from when our universe began billions of years ago. There is another way to view CMB radiation without any special instruments – your television. The black and white fuzz and static white noise is a glimpse of CMB radiation which causes about 1% of the interference you are viewing.
- Race of Revolutions: Neutron stars are dense remnants of stars which died in violent supernova events. They are comprised entirely of neutron material all packed tightly into a small space. These compact objects typically form from stars that were 1000s of solar masses which then shrunk into spaces as small as a city. They are incredibly heavy: a teaspoon of neutron star material would weigh 1 billion tonnes. Neutron stars that emit beams of radiation are called pulsars. They are the fastest spinning objects in the universe, with top rotation speeds clocking in at 70 000 kilometres per second (24% the speed of light)!
- Grand Architect: There are giant structures in the universe that show an incredible scale of design, and gamma ray bursts (GRB) are the little crumbs that point to their existence. A gamma ray burst is an intense release of a high energy, so it isn’t surprising that they are quite well spaced throughout the universe. However, there are regions of space with much higher concentrations of similarly distanced gamma ray bursts, suggesting that they are part of the same larger super structure. The largest of these possible structures is termed the Hercules–Corona Borealis Great Wall. If it does exist, the wall would be 6 – 10 billion light years in size.
- Sci-fi Dimension: Wormholes are often portrayed as life sized vortexes that allow humans to time travel by entering through one end and magically appearing on another. Mathematics actually proves that wormholes could exist, but the reality is a far cry from science fiction movies. They would exist in the quantum world, be smaller than an atom, and nearly impossible to stretch out enough to fit a human being. Such a grand feat would require manipulating an unthinkable amount of matter and energy, and the portal would also be highly unstable. One may be transported to a strange dimension with no chance of returning, or simply be killed by the volatile wormhole. Black holes are often linked to wormholes due to how they distort surrounding space-time fabric.
- Infinite universes: For everything we know about the cosmos, there are a lot of basics that we are only guessing at for now. For example, we cannot say for certain how space-time is shaped (though the leading theory is that it is flat and goes on forever). The predicament leaves open the possibility that there are many other universes in existence. It is possible that there are dimensions that do not even have the same laws of physics and may remain forever undetectable. Universes may also repeat given a long enough period of time, as particles can only be arranged in so many different ways. There could even be another you in a different dimension leading a similar life! It may seem like the ramblings of conspiracy theorists and sci-fi novelists, but scientists take the answers to these intriguing questions very seriously.
- Cosmic Crash: The space between stars within a galaxy is much greater relative to the space between galaxies. Stars will rarely collide, whereas it is a more common occurrence for galaxies to meet and merge. The Milky Way Galaxy and its neighbour the Andromeda Galaxy are currently on such a path. The pair are set to merge into one galaxy in approximately 3 billion years from now. The high activity of such an event would trigger mass star formation, while most of the existing stars will settle without colliding.
- Total Darkness: We have always known that the universe is expanding. The two most logical and expected outcomes were that expansion would either halt and the universe would collapse, or expansion would continue but the rate would drastically slow over time. The fact that our universe is expanding more rapidly than ever is baffling to astronomer. The force driving the expansion is called dark energy, and we have no further idea of its nature. The expanding universe also has another quirky characteristic: most of its mass comes from something we cannot see or detect directly, and is not made of any type of matter or antimatter of which we know. It is called dark matter for this reason.
As we see, the universe is rife with strange occurrences and magnificent creations. Possibly the most intriguing element to the cosmos is human existence: the universe come to life to study itself and be forever amazed.