Big Questions Answered

Our astronomer Radmila spoke to year 7 pupils at St Mary’s Catholic School in Bishop’s Stortford about the search for exoplanets (planets that orbit other stars) and life beyond the Earth. They had lots of fantastic questions which are answered below:


How hot is the Sun? – The surface temperature is 5500 degrees Celcius which makes it yellow. Really hot stars are blue and cooler stars are red. The core of the Sun is 15 million degrees Celsius!


How did the planets form? – Our solar system formed 4.5 billion years ago from a vast rotating cloud of gas and dust called a nebula. This nebula came from the supernova explosion of other stars. The cloud started to spin and it eventually flattened out (like spinning pizza dough) – a lot of material clumped together under gravity to form the baby Sun in the centre of the nebula and the rest of the cloud swirled around the young Sun. This swirling disc eventually formed the planets, moons, asteroids and comets. All of the elements on Earth were formed in the core of a very big star or stars  - the parents of the Sun and solar system!


How long would it take to go round the Moon? – The Apollo missions in the 60s and 70s had command modules that orbited the Moon in around 2 hours. The time it takes to orbit the Moon depends on how far away you are from the surface (the size of your orbit).


Why isn't there life on the Moon? – There is no liquid water on the Moon, the temperature varies from -183 degrees Celcius at night to 106 degrees Celcius during the day. Scientists believe liquid water is necessary for the evolution of life.


Will we visit the Moon again soon? – Possibly, but not anytime soon. We could mine the Moon for useful resources.


What is your most interesting planet? – I like Mars, there are so many bits of Mars that look like the Earth. I also like Saturn – I think it’s a really beautiful, majestic planet with interesting moons (I particularly like Titan). We don’t yet know enough about the exoplanets that have been discovered so far, for me to form an opinion about them.


How long does it take to get to Pluto? – NASA’s New Horizons spacecraft was launched in 2006 and took 9 years to reach Pluto, travelling at an approximate speed of 16 km per second or 36370 mph and covering a distance of 5 billion km. There were no people on board!


Why was Pluto removed? – It hasn’t been removed, it’s still there but we don’t call it a planet anymore - it is now a dwarf planet. It was reclassified as a dwarf planet in 2006.


Why are there hot and cold planets? – A planet’s temperature depends on its distance from the star and the nature of its atmosphere. Mercury is the closest planet to the Sun, the temperature on the day side is 427 degrees Celsius (hot enough to melt metal) and on the night side it plummets to -173 degrees Celsius. Venus is farther away from the Sun but its average temperature is a whopping 462 degrees Celsius – this is because its atmosphere is very thick and is mostly carbon dioxide which traps heat.


Why won’t we go to Mars? – Humans will go to Mars in the future, maybe 20-30 years from now. We just don’t have the right technology at the moment (especially as we would like astronauts to return to Earth).


Who names the planets? – The International Astronomical Union

Our planets are named after Roman gods apart from Uranus which is the Greek god of the sky.


Are there earthquakes on other planets? – The Moon has very weak moonquakes and Mars and Venus may also have very weak quakes, they don’t have geological activity.


I was told a planet will crash into Earth is this true? – No, all the planets are in stable orbits. It is possible a large asteroid will hit us many years in the future. Hopefully we will have devised a defence mechanism by then.


Will we become extinct? – Maybe, an asteroid might wipe us out or the Earth’s climate might change drastically making it difficult for us to survive. Hopefully the human race will work out ways to continue living on the Earth and maybe colonise Mars or an exoplanet.


Why will the Sun explode? – The Sun won’t explode but stars at least 8 times more massive than the Sun undergo a supernova explosion at the end of their lives. Our Sun will die in a more gradual way. In about 5 billion years it will expand and turn from yellow to red (we call this a red giant star). Then it will slowly lose its outer layers of gas over a period of around 10 000 years, eventually becoming a small white dwarf.


How did life on Earth begin? – Scientists aren’t entirely sure, one theory is that the first organisms were formed at the bottom of oceans.


Why do we look for other planets? – To find out more about our planet and to see if there might be life on other worlds. Also finding out how other planets compare with the planets in our solar system is really interesting.


Do you believe there is life on other planets? – Yes – there are 2 trillion galaxies in the Universe and most of them have around 100 billion stars. Most of those stars have their own planets. There are so many exoplanets I believe that there must be life elsewhere.


Why do we want to find other humans? – To learn more about our origins and origins of life. To compare life on Earth with life on other worlds. They might be more advanced than us – we could learn a lot from them.


When will we visit other planets? – Humans will travel to Mars in the next 20 or 30 years, but to travel beyond the solar system to a potentially habitable world would exceed our lifetime. The nearest potentially habitable world is called Proxima b and it would take 70 000 years to get there with current technology.


Do you think aliens are trying to get to us and are they on their way? – Good question - maybe, maybe not! If we were invaded by aliens I don’t think it would be pleasant, I think they would want to take over the Earth and push us out. I very much hope they’re not on their way!


What do other things/people look like on other planets/Are all aliens green? – Astrobiologists believe that if we find intelligent beings on an exoplanet like the Earth they will look like humans! Who knows what other species there may be on these other worlds. There are lots of things to consider like the strength of gravity (if the exoplanet has stronger gravity than ours the people there might be much shorter than us), the temperature, the length of day, the weather/climate.


Is there food on other planets? – Not in our solar system but there might be food on exoplanets that are habitable (have water and the right conditions for life). There might be exoplanets that are covered in plants, there may also be other organisms eating the plants. There might be intelligent beings creating their own recipes like we do!


Is there something outside of the Universe? – No we don’t think so. The Universe may be infinite and have no actual boundary. It might have more than 3 dimensions (height, length, width) which no human on Earth can imagine! The current size of our universe (there may be other universes) is 93 billion light-years – that means a text message would take 93 billion years to travel across our universe. We're not sure what it’s expanding into – maybe this question is irrelevant and we’ll never be able to understand it!


How many people work with you? – I am an astronomer and teacher at the Royal Observatory and I work with 10 full-time staff. We have lots of part-time staff including university students who help us teach schools and the public about astronomy and science.


How long have you worked at your job/ Why did you choose your job? – I have been at the Observatory for 7 years. In that time I have spoken to hundreds of thousands of people about astronomy, I have written a book called Stargazing: the beginner’s guide to astronomy, I have done lots of press interviews (newspapers, radio and TV) and I have given lots of talks across the country in schools, astronomy clubs, science fairs and also music festivals. It’s a very cool job and I love meeting new people! Before this job I was a teacher in a secondary school and before that I was doing my PhD in astrochemistry at the University of Nottingham, where I obtained data from professional telescopes situated in Hawaii and Chile. I highly recommend following a career in astrophysics – there are lots of different jobs you can do and it’s really interesting!


How do you know all this? – A big part of my job is to read the latest discoveries in space science, you can do this too by visiting the following websites:



Latest discoveries and missions

Astronomy photos and tips for young people


How long did it take you to become an astronomer? – I did well in my science and maths GCSEs (I loved these subjects the most) – this took 2 years and then I did A-levels in maths, physics and biology (2 years). I went to the University of Birmingham to do a degree in Physics with Astrophysics (4 years) and then did a PhD in astrochemistry (molecules in space) at the University of Nottingham (3-4 years). That’s a total of 12 years!


Would you like to live on another planet? – Only if it is like the Earth! Also the journey time to an exoplanet is too long, I would be dead before I arrive there! The journey time to Mars with current space rockets is around 6-7 months.


Do you want to go into space? – Not sure - it’s a bit scary. It would be lovely to see the Earth from the International Space Station, you can see videos taken by the astronauts on board below:

Earth from the ISS