I see no difference between detecting a dark nebula due to a marked absence of faint stars, and detecting a loose open cluster because of a statistically significant increase in star density
at the cluster's plotted position.
These galaxies are often too faint for images, so scientists use maps of star density
Mussel recruitment and sea star density
. - We observed that the abundances of juvenile Mytilus spp.
The three levels of star density
make this a worthy target that I've enjoyed on many nights.
Hubble's blurred vision (SN: 7/7/90, p.4) can resolve only the very beginning of a rise in star density
; the density might level off farther into the core.
It's a beautiful sight in a 4-inch reflector at 45x, and the star density
holds up well enough to make it spectacular even in the largest of amateur instruments despite overflowing the field of view.
Indeed, Lauer says, the actual star density
may well exceed this estimate, which is based on Hubble's current optical images.
The galaxy's characteristic spiral arms are zones of higher star density
within the thin disk.
But certain other, smaller parts of the sky have an even higher star density
It shows a very large halo nearly 20' across with an abrupt increase in star density
I have seen the patchiness in other telescopes and have never known whether I was observing nebulosity or variations in star density
, or both.
If we aim haphazardly at a location more than 20 [degrees] from the galactic equator, where the average naked-eye star density
is only [Lambda] = 0.056 star per square degree, the computer program shows that the chance of not finding any naked-eye stars within the ring is 50 percent - just as likely as heads on a coin flip.