Question

What is NGC 7664 distance from the Earth?

Answer 1

In astrophysics, we usually use redshift to measure distances (or time ago). This is due to Hubble's Law (the discovery that the universe is expanding, basically). The redshift for NGC7664 is
\[z=0.01159\] source: http://www.wolframalpha.com/input/?i=ngc+7664
and using a redshift calculator (since the conversion from redshift to distance depends on a whole bunch of things), we find that this z-score pertains to a comoving distance of 160 million light years, or 49.2 Mpcs.

Answer 2

what ahout the distance to NGC 4378?? it has a redshift of 0.008536

Answer 3

and NGC 1620??

Answer 4

A good resource in general is the site I mentioned earlier: wolframalpha.com. They also have a cosmological distance calculator: http://www.wolframalpha.com/input/?i=redshift&a=*C.redshift-_*Formula.dflt-&a=FSelect_**LookbackTimeFromRedshift-.DopplerRedshift.RelativisticRedshiftFormula.RedshiftWavelengthFormula.GravitationalRedshiftFormula-&f3=0.01159&f=LookbackTimeFromRedshift.z_0.01159&a=*FVarOpt.1-_**-.***LookbackTimeFromRedshift.OmegaLambda-.*LookbackTimeFromRedshift.OmegaMatter-.*LookbackTimeFromRedshift.OmegaRadiation--.**LookbackTimeFromRedshift.UniverseName--.**LookbackTimeFromRedshift.H0---.*--

If you're good at calculus and have explored a bit more in cosmology, you can try to do these calculations by hand, using the Lambda-Concordance Dark Matter Model, and subbing in omega-values in the formulae here: http://en.wikipedia.org/wiki/Distance_measures_(cosmology). Otherwise,