... Just for laughs,
if it happens, caring wouldn't do much good.
Actually interesting aspects but a correction on the scale of things is "they assume it has a size twice of Jupiter" is wrong and should read "mass twice that of Jupiter"
Now mass in this case is far more dangerous than size if it passes at 0.25 AU as they also say it will since it affects our gravitational fields. However towards the shift October/November it should pass out of our solar system across our orbit approx. 4 days (96 hours) ahead of our passing the same place, at approx. 88,000 kph which places the whole thing at some 8,5 million (not 34 million) km distance in the tail of the icy tail.
On the other hand, the comets, which is NOT a dwarf star and coming much closer to us are 1) HONDA, approx 1/3 of the distance away and 2) yet another comet called something doomsday like, assumed to passing in 2014-2024 just outside our atmosphere, and then returning mid 2030's possibly crashing.
The later one is approx. 250 meter in diameter and would offset an equivalent 1,000 kT nuclear blast.
Now as for Elenin, it would be interesting if they could make up their minds in the peer review circles weather or not the dwarf star is 450 meters or 5425 Kilometers in diameter. (the latter being approx. 75% of the size of Planet Earth) since it is also dragging along some three or four orbiting moons which could smash into just about anything as well.
In the greater perspective, solar flares are far more dangerous than any of this, unless a giant solar flare sets off when Elenin passes between us and the sun in direct alignment, in which case the "tail blast" of molten ice and rock would blast in our immediate direction as is common for comets, causing meteors and possible meteorites to head for our little blue rock in the sky.
Lots of reading and lots of info needs to be analyzed before believing any and all doomsday prophecies. :study: