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Schools Home > Festivals & Events > Space Day > Q & A - Planets, Dwarf Planets & Stars

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Space Day Q&A - Planets, Dwarf Planets & Stars

How many planets are there in our Solar System?

There are 8 planets and 3 dwarf planets.

Voyager 2 passing Jupiter










Dwarf Planets




What is the difference between a planet and a dwarf planet?

In order to be a planet, the space object must have 3 characteristics

  1. They must orbit the Sun
  2. They need to have enough gravity to pull themselves into a ball
  3. They need to have cleared out all other objects from their orbit.

A dwarf planet does not meet the last requirement.

Which planets look blue and why?

Neptune and Uranus both look blue, because their atmospheres contain methane gas, which absorbs red light and reflects back blue light.

Which planet has the hottest temperature?

Venus has surface temperature of over 460 degrees centigrade.

Which planet has the coldest temperature?

Uranus which has an average surface temperature of about -213 degrees centigrade.

Are there any other planets orbiting other stars?

Yes, so far, as of September 2010, scientists have found 490 planets orbiting other stars. These are called Exoplanets or Extrasolar planets.

Which planet has a red spot?

The Great Red Spot on Jupiter is a massive gaseous hurricane that has lasted for hundreds of years.

Which planet has the most Moons and how many?

Jupiter has 62 Moons.

Which planets have rings?

Jupiter, Saturn, Uranus, and Neptune all have rings. Saturn’s are the most spectacular. They were the first to be observed too – in 1610 by Galileo, using an early telescope.

What is the Sun?

It is the star at the centre of the Solar System around which Earth and the other 7 planets revolve.

Is the Sun the biggest star?

No, the Sun appears to be so large because it is the closest one to us. It is in fact a medium sized star.

What is the largest known star in the Universe?

The heaviest known star discovered in July 2010 is the R136a1. It is about 300 times heavier than the Sun, about 70 times wider, and about 8.5 million times brighter. The star with the largest diameter is called VY Canis Majoris, and is about 4000 times as wide as the Sun.

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