ENCORE In astronomy, the rule of thumb was simple: If you can’t see it with a telescope, it’s not real. Seeing is believing. Well, tell that to the astronomers who discovered dark energy, or dark matter … or, more recently, Planet 9. And yet we have evidence that all these things exist (although skepticism about the ninth – or is it tenth? – planet still lingers).
Find out how we know what we know about the latest cosmic discoveries – even if we can’t see them directly. The astronomer who found Planet 9 – and killed Pluto – offers his evidence.