APOD: 100 Million Stars in the Andromeda... (2015 Jan 06)

[geckzilla]

Question: So I downloaded the 348 MB (!) TIFF file and zoomed in. In between the Milky Way foreground stars you can see hundreds of thousands of dots. Are these actually Andromeda's stars or digital noise?

Those are stars. It can be sort of hard to tell when the contrast is so high but here is a small slice at 100% zoom level with very little processing applied. The relative brightnesses of the individual stars is well-preserved, here. http://www.geckzilla.com/astro/m31_phat ... ostraw.jpg

[rgendler]

Question: So I downloaded the 348 MB (!) TIFF file and zoomed in. In between the Milky Way foreground stars you can see hundreds of thousands of dots. Are these actually Andromeda's stars or digital noise?

Yes those are fully resolved individual stars in M31's disk....117 million of them. It is not noise.

[Ron-Astro Pharmacist]

Besides Andromeda's star composition, could the data be used to detect disposition by forces inside or outside of the galaxy (such as gravity waves, unknown black holes, dark matter or energy)? I suspect this type of data has already been well studied in smaller sets and need not be redone in groups this large to see if changes occur over time. But it does seem a tempting target to see if changes in position occur en masse amongst so many small individual units – crudely, "Does the PHAT jiggle or wiggle oddly?"

e.g. Could a data set this large be used to detect subtle intrinsically or extrinsically -induced star movements that we've not noticed before if all or some data is re-examed at a later date for comparison. Obviously this was a huge undertaking and the results are spectacular. I'm just curious to see how it comes to bear fruit.