Top 10 Solar System facts so far…

10. The total number of stars in all the galaxies is comparable to the number of dry sand grains on all the beaches on Earth. There are about 100 billion galaxies and the total number of stars in all those galaxies is about 1000 billion per galaxy.

9. We are always in motion:

  • We spin around Earth’s axis at 1000 km/hr
  • We orbit the Sun at 100,000 km/hr
  • Our solar system moves randomly at 100,000 km/hr
  • Our solar neighbourhood orbits the centre of the Milky Way at 1,000,000 km/hr
  • Our galaxy moves randomly among our local group of galaxies at 300,000 km/hr

8. The Earth wobbles like a spinning top. The path the wobble carves out is called precession. It takes approx. 26,000 years for the Earth to complete one top wobble.


7. Solar eclipses happen because of coincidence. The Sun is 400 times larger than the Moon, and the Sun is also 400 times farther away. These 2 factors are such that the Moon can completely overlap the Sun. In the distant past the Moon used to be a lot closer to the Earth so eclipses were not possible. Also, the Moon is slowly drifting away from Earth at 1 cm per year, so in the distant future it will be too far away to block the Sun.

6. The names for the 7 days of the week come from the 7 known objects known to change their position: Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn. The names come from the Norse-Celtic barbarians that overthrew Rome.

  • Sun-day
  • Moon-day
  • Tiu (Mars) – day
  • Woden (Mercury) – day
  • Thor (Jupiter) – day
  • Freya (Venus) – day
  • Saturn – day


5. Astronauts orbiting the Earth are weightless because they are continuously falling toward the Earth, not because there is no gravity. There is plenty of gravity in space. Astronauts and the ISS are continually falling, but they never reach it, that is why they are weightless.

4. The human eye was the first astronomical detector, however, it can only detect 1 in every 1000 photons. Astronomy’s newest detector, the Charge-Coupled Device (CCD), captures 1 in every 1.1 photons.

3. The Sun contains about 99.9% of the total mass in the solar system.


2. Our solar system formed from the gravitational collapse of a large cloud of gas and dust. This theory is called Solar Nebular theory. As the cloud collapsed is flattened out into a disk. Our young protosun is at the middle of the disk, where the temperature is hotter than the outside. This determined the difference in the types of planets that formed, rocky terrestrial planets on the inside and gas giants on the outside. When the Sun finally turns on strong solar winds burn away left over material from the disk.

1. The Apollo 11 mission boot prints on the surface of the Moon will remain for around 200 million years due to the lack of erosion, due to very little atmosphere on the Moon.