Explanation:
Why is there a line segment on the sky?
In one of the more precise alignments known in the universe, what is pictured above is actually a disk galaxy being seen almost perfectly edge on.
The image from the
Hubble Space Telescope is a spectacular visual reminder of just how
thindiskgalaxies can be.
NGC 4452, a galaxy in the nearby
Virgo Cluster of Galaxies,
is so thin that it is actually
difficult to determine what type of disk galaxy it is.
Its lack of a visible dust lane indicates that it is a low-dust
lenticular galaxy, although it is still possible that a view from on top would reveal spiral structure.
The unusual stellar line segment spans about 35,000
light years from end to end.
Near NGC 4452's center is a slight bulge of stars, while
hundreds of background galaxies
are visible far in the distance.
Galaxies that appear this thin are rare mostly because our Earth must reside (nearly) in the extrapolated
planes of their thin galactic disks.
Galaxies that actually are this thin are relatively common -- for example our own
Milky Way Galaxy is thought to be about this
thin.
