Equation 4 · Part 12 · A Neutron Star Is a Redshift Standard

Denominator: Rc^2

z_s = \left(1 - \frac{2GM}{Rc^2}\right)^{-1/2} - 1

Rc^2

What this part means

The complete quantity below the fraction bar; it must be nonzero for this division.

Its job in the formula

R $c^2$ occurs below the fraction bar. The quantity above the bar is divided by this expression; zero is excluded as a denominator.

Full expressionDenominator: Rc^2Article meaning

The passage around this formula

The relation itself is old and simple. For a spherical, non-rotating exterior, the surface redshift $z_s$ follows from the mass M and radius R as $z_s = \left(1 - \frac{2GM}{Rc^2}\right)^{-1/2} - 1$ . — a function of the star’s compactness alone, so that whatever fraction of a percent of uncertainty NICER puts on M and R propagates directly into the redshift. The paper works through six NICER-mapped pulsars this way, and two of them mark the range worth remembering. PSR J0740+6620, the most massive precisely-timed neutron star known, comes in at roughly 2.07\, $M_\odot$ with a radio-timing mass fixed independently by Shapiro delay to 2.08 $\pm$ 0.07\, $M_\odot$ [ 4 ] , giving a compactness near 0.25 and a surface redshift $z_s$ $\simeq$ 0.40…

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Learn the underlying idea

A fraction a/b means a divided by b. The top number is the numerator; the bottom number is the denominator, and it cannot be zero.

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Sources cited in the surrounding passage

These citations provide research context; check each source for the exact claim it supports.