KnowSoda
ScienceEarth & Space
Stars & Galaxies: fun facts and quiz
The essentials in 7 ideas, with fun facts, an illustrated story and a quiz to see how much you know.
The essentials
What Stars Are
Stars are giant balls of hot gas that shine by fusing hydrogen into helium in their cores. The Sun is a fairly ordinary star.
Key fact
The nearest star after the Sun, Proxima Centauri, is about 4.2 light-years away.
Light-Years
A light-year is the distance light travels in a year: about 9.5 trillion km. It measures distance, not time.
Key fact
Looking at stars is looking back in time.
Constellations
Constellations are patterns of stars named long ago, like Orion and the Great Bear. Astronomers officially recognise 88 of them.
Key fact
Stars in a constellation can be at very different distances from us.
The Milky Way
Our Sun is one of 100 to 400 billion stars in the Milky Way, a spiral galaxy about 100,000 light-years across.
Key fact
The Sun takes about 230 million years to orbit the galaxy’s centre.
The Life of a Star
Stars are born in clouds of gas and dust. Sun-like stars swell into red giants and end as white dwarfs; the most massive explode as supernovae.
Key fact
The Sun is about halfway through its life, some 4.6 billion years in.
Galaxies
The observable universe holds hundreds of billions of galaxies, perhaps more. Our nearest big neighbour, Andromeda, is about 2.5 million light-years away.
Key fact
Andromeda is approaching the Milky Way at about 110 km per second.
The Big Bang
The universe began about 13.8 billion years ago in the Big Bang, and it’s still expanding. Faint leftover heat from it fills all of space.
Key fact
That leftover glow is called the cosmic microwave background.
Fun facts
Energy made in the Sun’s core takes tens of thousands of years to reach its surface, then just 8 minutes to reach us.
Moonlight takes about 1.3 seconds to reach Earth, so you always see the Moon as it was a moment ago.
The Big Dipper isn’t a constellation: it’s an asterism, a star pattern inside the Great Bear.
The word “galaxy” comes from the Greek for milk: the Milky Way looks like milk spilled across the sky.
The gold in jewellery was forged in exploding or colliding stars.
Some galaxies are so far away that the light we see from them set off over 13 billion years ago.
A little of the static on old analogue TVs came from the Big Bang’s leftover glow.
Story: The Pigeons in the Antenna
The Pigeons in the Antenna
1964, New Jersey. Arno Penzias and Robert Wilson can’t get rid of a faint hiss in their giant horn-shaped radio antenna. It comes from every direction.
They blame the pigeons nesting inside. They scrub out the droppings and send the birds away. The hiss stays.
It was the leftover glow of the Big Bang, filling all of space. Their pigeon problem won them the 1978 Nobel Prize in Physics.
True or false?
Tap your answer to see if you got it, and why.
-
Question 1 of 10
Stars shine by nuclear fusion.
Show the answer
True. Fusing hydrogen into helium.
-
Question 2 of 10
A light-year measures distance.
Show the answer
True. How far light travels in a year.
-
Question 3 of 10
Orion is a constellation.
Show the answer
True. Named after a hunter in Greek myth.
-
Question 4 of 10
The Milky Way is a spiral galaxy.
Show the answer
True. With arms curling out from the centre.
-
Question 5 of 10
Very massive stars can end as supernovae.
Show the answer
True. Huge explosions that can outshine a galaxy.
-
Question 6 of 10
Andromeda is heading towards the Milky Way.
Show the answer
True. They may merge in several billion years.
-
Question 7 of 10
The universe is still expanding.
Show the answer
True. Galaxies are moving apart.
-
Question 8 of 10
Stars are made mostly of rock.
Show the answer
False. They’re made mostly of hydrogen and helium gas.
-
Question 9 of 10
A light-year is a unit of time.
Show the answer
False. Despite the name, it’s a distance.
-
Question 10 of 10
Stars in a constellation are always close together in space.
Show the answer
False. They only look close from Earth.
Keep going in the app
KnowSoda learns what you know and brings back what you’re about to forget. Stars & Galaxies has 6 more ideas at the Advanced and Expert levels.
