13 March 2009

Six impossible galaxies before breakfast

Here, we have Stephan's Quintet, a bunch of five galaxies which hang around together.

Or do they?

Some people became curious, so they did a little research, & discovered that NGC 7320 (lower left in image) has a redshift of about 800km/sec versus roughly 6000 for the other four. The indication is that 7320 is much closer than the others.

Unfortunately for any triumphalism which this may invoke, 7320 (& 7319, upper left) has faint but continuous gas/dust tails leading to another galaxy, 7319C, illustrating that they’re all connected, so at roughly the same distance. Oops...

Meanwhile, 7319 has a quasar (QSO) within it. Interacting with the dust near the core of the galaxy. With a massively higher redshift, indicating that it is much more distant than the galaxy it rests in (over 90 times more).

All of this is of course impossible. But it exists, it is still happening. We can see it. We can point to it. Never mind...

Oh, one other little impossibility: as well as being wildly different from adjacent galaxies, QSO redshifts appear to be quantised (at a factor of 1.3-fold per step) how many was that, now...?

1 comment:

yiri said...

James Dumay linked me to this, glad he did.

Awesome post!