Sky and Telescope - January 2016 - 60

OBSERVING

Going Deep

the process that made it supermassive.
Finally, there's a faint foreground star tucked in near
where the northern spiral arm connects with the central
bar, and I've mistaken it for a supernova more than once.
There's an even fainter star right at the point where the
bar really does connect with the spiral arm, but it took
the 48-inch scope to see it.

The Core
"Dim but distinct - the deﬁnitive barred spiral. The arms
are more distinct than the bar, with the nucleus the brightest
of all." September 21, 1998, 20" f/5, 282×
"My ﬁrst thought was 'supernova!' but a quick check of last year's
sketch shows the same star enclosed by the spiral arms. Oh well,
it's still a cool sight. The arms are subtle but the core is blazing."
October 8, 2002, 20" f5, 375×

Composite drawing of NGC 1365 made by combining the author's
sketches from his 20-inch and 28-inch telescopes and those
made from Jimi Lowrey's 48-inch.

like the 2002 sketch above - that looks like the spiral
arms aren't attached to the core.
Usually, though, the bar appears as a rather broad and
evenly illuminated connection to the core. More precisely, the bar is in two sections, east and west. Although
visually faint - I have yet to detect any detail within
the bar itself - recent ﬁndings suggest gas and dust
from the spiral arms is being funneled through the bar
toward the core, forming new stars along the way. This
may also feed the central black hole and could be part of
60

Januar y 2016 sky & telescope

". . . (Note the split core!)" November 2, 2013, 48" f/4, 375×,
21.28 SQM
Aside from the spectacularly curved spiral arms, the
egg-shaped core was obviously split by a dark lane in the
48-inch scope, and under poor conditions no less.
Nonetheless, the core appears oblong and at somewhat of an angle to the brightest, straighter portions of
the spiral arms. But as more of the arms become visible
the more obvious it is that the major axis of the core
lines up with the overall shape of 1365.
This is the brightest part of the galaxy, and inside
lives the relativistically spinning two million-solar-mass
supermassive black hole I mentioned earlier - whirling
at 84% the speed of light.
. . . Wait - what? 1365's supermassive black hole is
spinning at 84% the speed of light?
Apparently so. Think about that for a moment.
It can't be seen visually, of course, but just knowing
it's there - and trying to imagine the relativistic environment around it - is fascinating in the most delightfully mind-boggling way.
Aside from the outrageously twisted spacetime this
implies, it also suggests the black hole has grown in a
fairly orderly manner, because random growth would
tend to slow its spin. Perhaps it's spinning so fast
because of how the bar funnels gas and dust toward the
core from the spiral arms, but that's unclear just yet.
Still, it's tempting to speculate that 1365 is shaped the
way it is because of how it feeds the black hole.
However, the fact that you can see the core that
surrounds this beast with your own telescope - not to
mention the bar and spiral arms that might be fueling
it - is nearly as amazing as a relativistically spinning
supermassive black hole existing in the same universe
as we do.
Keep this in mind the next time you observe 1365,
and regardless of how much you see I guarantee it will
look more interesting.
Can you imagine? ✦

Sky and Telescope - January 2016

Table of Contents for the Digital Edition of Sky and Telescope - January 2016