It sounds like something right out of a good SiFi book, but NASA believes it has identified the cause of the mass extinction of the dinosaurs.

AN invisible star responsible for the extinction of dinosaurs may be circling the Sun and causing comets to bombard the Earth, scientists said.

The brown dwarf – up to five times the size of Jupiter – could be to blame for mass extinctions that occur here every 26 million years.

The star – nicknamed Nemesis by NASA scientists – would be invisible as it only emits infrared light and is incredibly distant. Nemesis is believed to orbit our solar system at 25,000 times the distance of the Earth to the Sun.

As it spins through the galaxy, its gravitational pull drags icy bodies out of the Oort Cloud – a vast sphere of rock and dust twice as far away as Nemesis.

These “snowballs” are thrown towards Earth as comets, causing devastation similar to the asteroid that wiped out the dinosaurs 65 million years ago.

Yes, that’s right, we have an brown dwarf throwing snowballs at us. You know, when you put it like that, it just doesn’t sound as threatening does it?

NASA hopes to find it using a new heat-seeking telescope. Apparently the first clue that Nemesis was out there was the discovery of another dwarf:

Scientists’ first clue to the existence of Nemesis was the bizarre orbit of a dwarf planet called Sedna. Scientists believe its unusual, 12,000-year-long oval orbit could be explained by a massive celestial body.

Mike Brown, who discovered Sedna in 2003, said: “Sedna is a very odd object – it shouldn’t be there.

“The only way to get on an eccentric orbit is to have some giant body kick you – so what is out there?”

Nemesis – the dark star, of course.

Yeah, much better.

~McQ