It already has a 64, 000km-long tail of dust and gas that will become visible to the naked eye later in the year - a trail scientists will study closely.

BBC: Comet Ison caught on film by Deep Impact craft

As a comet gets closer to the sun, the sun's heat causes these elements to melt, spewing out dust and gas in a brilliant tail.

CNN: Welcome to the year of the comet (we hope)

At the tail end of the global economic boom, when concerns about the environment were widely voiced, large "gas-guzzling" sports utility vehicles (SUVs) became objects of loathing and ridicule.

BBC: Business