I reckon ...
... that one of Johnny Fartpants ancestors happened to be visiting the system, and had a 'little' accident!
A rogue white dwarf star hurtling through the Milky Way may have freed itself from a binary system after it partially exploded as a supernova more than 40 million years ago. The star, snappily code-named SDSS J1240+6710, was discovered in 2015, and has odd properties scientists couldn’t initially explain. Unlike typical white …
Relative to the rest-frame of the galaxy in this case, I think. And in fact the numbers are even more frightening. If I've read the paper properly, it's moving about 250km/s against the rotation of the galaxy which is about 239km/s where it is, so it's motion relative to the stars it is near is something like 500km/s, or 1,800,000km/h.
Peculiar motion relative to the galactic rest frame. It's essentially one of the two standard frames for observations of things within the galaxy (the other being the Solar System centre of mass), found by taking the average motion of eveything in the galaxy.
Particularly notable, although for some reason not mentioned in the article, is that this star isn't just moving very fast, it's also going backwards.
Yes, sorry. Those responsible have been reprimanded. This one wasn't actually armed though: the live versions will be firing orbiting pairs of white dwarfs, very close to the point at which the larger one accretes enough from the smaller to become a type 1a supernova, timed to occur within the enemy's defensive screens. Fuzing has proved difficult however.
The white dwarf is just the recoil...
There's a magnetar flying out in the opposite direction, coupling (geddit) disruptive magnetic fields with a kinetic threat. And a dose of hard radiation.
Given that the white dwarf is travelling through the milky way it would appear that someone is repelling intergalactic invaders!
I wonder if this formerly binary system was close to merging, and the event happened before this merger was successful - also the two objects could have been circling each other at astounding speeds as well - but because one of them went NOVA just before the merger, somehow the angular velocity was preserved and imparted a nearly equal and opposite reaction, instead of simply merging and becoming another form of star, or even a black hole. I've never read that a binary system merging like that ever ended up changing from original direction before, so I'm assuming as a novice astrophysics fan, that something completely different had to happen like that. It would seem that much of the matter from both stars would have coalesced however, and just an expanding blast wave with left over gases was left at the event site. Also, I wonder if anyone is gathering data on what are the known universe's fastest objects (relatively speaking of course)
With that incredible speed, it would sure be fun, to watch at a safe distance and see this rogue dwarf slam into another mass of any type in the galactic plane!! Just the thought of that thing moving so fast against the grain of the galaxy would seem like at least doubling the chances of a collision - but the disappointing reality, is that entire galaxies probably pass right through each other with barely even one of such meetings.