International Astronomy Day 2018 Astronomy facts!

About International Astronomy Day

April 21st is International Astronomy Day!  International Astronomy Day happens two times a year: in spring and in fall. It is a day for public observatories, museums, planetariums and astronomical societies to organize events to spread public awareness about astronomy and its wonders. The next International Astronomy Day will be October 13, 2018. International Astronomy Day started in 1973 in California, and it is now celebrated around the world.

MindMint prepared this post full of astronomy facts to spark your curiosity about our universe.

Space is not that far away

If we could drive upwards at the same speed as we move on highways we could be in space in less than an hour. According to most international treaties and official regulations the frontier of outer space is called the Kármán lineand it is just 100 km away.

The moon is getting farther and farther away from us

Our moon is 384 km away from Earth, and this distance increases by 3.8 cm every year due to the gravitational interaction between the Moon and the Earth. Another effect of the interaction between Earth and the Moon is that Earth’s spin is slowing down by 2.3 milliseconds each century, which means our days get 2.3 milliseconds longer every century.

We’ve been to the moon 6 times

Most people know that humans have landed on the Moon’s surface, but not many people know that we’ve returned there a few times to conduct more scientific experiments, and to collect samples. Together, the six Apollo missions that landed on the Moon have brought to Earth almost 400 kg of lunar soil. Some of the debris from the visits can still be seen today by space probes passing by the moon. China, India and Japan have plans to send manned missions to the moon again before 2021.


Jupiter has ‘at least’ 69 moons

Jupiter has so many moons that only 53 of them have actual names, the others are simply identified by their dates of discovery. While 69 moons may sound like a lot for one planet, we must remember that we can fit 1300 Earths inside of Jupiter! In terms of proportions, we can expect Jupiter to have many more moons than Earth. Jupiter also has the largest moon in the Solar System: Ganymede. Ganymede is larger than the planet Mercury, and would be considered a dwarf planet if it wasn’t orbiting Jupiter.

Our solar system has 5 dwarf planets

In 2006 Pluto was stripped of its planetary title and demoted to the status of dwarf planet. According to this new definition of planet, our Solar System has 8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune) and 5 dwarf planets (Ceres, Pluto, Haumea, Makemake and Eris). The main difference between a planet and a dwarf planet is that the latter’s gravity is not strong enough to influence other objects along its orbit. Ceres, for example, is part of the Asteroid Belt between Mars and Jupiter, and for many years it was just considered to be a very big, round, asteroid. All the other dwarf planets, including Pluto, are located past Neptune’s orbit. These dwarf planets, together with many more objects, are called Trans-neptunian objects.

We may  have a 9th planet orbiting out there

In 2016, scientists found indirect evidence of a possible 9th planet as large as Neptune, moving around the sun in an elongated orbit past Pluto. The existence of the so-called Planet Nine (not an official name) is based on calculations of the orbits of Trans-neptunian objects. So far Planet Nine has not been directly observed, and not all astronomers agree that it exists. If Planet Nine is really out there, it wouldn’t be the first time that a planet has been discovered through the use of math; the existence of both Neptune and Pluto was predicted based solely on the motions of other planets before being observed directly.

 It took 35 years for a human-made object to leave the Solar System

Voyager 1, a probe launched in 1977, officially left our Solar System in 2012. If Voyager 1 was heading to the nearest star Proxima Centauri it would take approximately 76000 years to reach it.

Our sun is just an average star

The sun is 4.6 billion years old, has the size of a million Earths and contains 99.86% of all the mass in our solar system. The sun is also classified as a Yellow Dwarf, which is just an average star. The image below illustrates the size of other stars in our galaxy in comparison to the Sun. Our galaxy, the Milky Way, is estimated to have around 7 billion stars just like the Sun. Even more astonishing is the fact that almost all 200 billion stars in our galaxy have at least 1 planet orbiting them. And our galaxy is just one among hundreds of billions of galaxies in the universe.


Most galaxies have a black hole at their center

And no, we’re not going to be sucked into it. Stellar black holes are the remnants of dead supermassive stars, and they are fairly common in the universe. But in the central regions of galaxies, scientists often find evidence of supermassive black holes. These supermassive black holes are millions- or even billions- of times heavier than their stellar counterparts. Both supermassive and stellar black holes are so compact that gravity becomes too strong near their surface for light to escape, resulting in absence of emitted or reflected light, and that is how they have earned their name.  At a safe distance (which depends on the black hole’s mass), a black hole is no different than a dark star- or in the case of supermassive black holes, millions of stars, compressed into a small space.

The Milky Way and Andromeda will collide in about 4 billion years

Our galaxy and the galaxy Andromeda are bound to crash into each other in a few billion years. While it is unlikely that Earth or the Sun will collide with another solar system during this process, it is expected that our sky will appear brighter and brighter as the two galaxies approach each other.

Click on the image below to watch a video of how it may look:

For those of us  in the city of Groningen:

The University of Groningen regularly organizes engaging astronomical events with the Blaauw Observatory and DOT planetarium, and you can see the scheduled events below: 

About the Author:

Evandro Martinez Ribeiro is a 4th year PhD candidate at the Kapteyn Astronomical Institute. His research focus on studying the X-ray emission from around neutron stars and stellar black holes in interactive binary stellar systems. You can send him questions and comments at 

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