You wait ages for an interstellar comet to arrive and then three come along at once. Or at least over the space of a decade. The latest interloper from another star system is the 3I/Atlas comet, which was first detected in July. As space agencies track the speeding object, here’s what we know so far.
What are comets?
Comets are made from material left over when star systems form. In the solar system, that means dust and ice that dates back 4.6bn years. At the heart of a comet is a central, solid nucleus, or “dirty snowball”, made of frozen water, dust and volatile substances such as carbon dioxide, carbon monoxide, methane and ammonia.
