I classified the central object as "Star or artifact"? SkyServer too says it is a star.
It was mentioned elsewhere in this site that 6004 galaxies were chosen for this project. Looks like a star sneaked in! 😃
The redshift is given as 0.326. I thought maybe a faint galaxy is lurking somewhere near the star. The Neighbors list shows two galaxies and neither is near the central object here.
It's a 'star' when analyzed by the SDSS DR8 photometric pipeline ('star' simply means that it's not an extended source). In particular, in PhotoObj - the long table you get when you click on the link of that name in the left-hand panel of the Explore tool - "probPSF_r" is 1 (ditto for the g and z bands; it's 0 for the u and i bands).
However, we have a spectrum, and the spectroscopic pipeline says this is a "GALAXY":
So, based on just the image, you (anyone) can't tell it's not a star; but when you look at the spectrum, there's no doubt it's got a redshift of 0.32569±0.0004 😃
There's more. 😮
Why was this object singled out? Why go to the trouble of taking its spectrum? Because it's a "QSO_HIZ" target, meaning that it looks like a
quasarstar (most quasars look like stars in SDSS images), but its colors are odd; perhaps it's a 'high z' (i.e. high redshift, greater than 3 perhaps) quasar?
And the spectrum is classic post-Q (a.k.a. E+A a.k.a. K+A): nice strong hydrogen Balmer absorption lines, getting stronger as you go from alpha to beta to ... with a continuum that is a nice mix of that of an ETG (early-type galaxy, a.k.a. elliptical, the "E" in "E+A") and an A star.
Thanks for the detailed reply. Lots in there for me to explore and learn.