The phrase "a central mass" is correct and usable in written English.
It can be used in contexts where you are describing a significant or main body of material, substance, or energy in a particular setting, such as in science or literature.
Example: "The scientists focused their research on a central mass of dark matter that seemed to influence the galaxy's rotation."
Alternatives: "a core mass" or "a primary mass".
This mat is a gigantic single cell, called a plasmodium, which forages by sending out dozens of tendrils from a central mass.
Surgeons, believing this "centrifugal theory" — cancer's stainlike, outward spread from a central mass — advocated ever-widening surgical extirpations to eliminate cancer.
Among new surface features that were detected was one, called "the spider," formed by more than 100 trenches that radiate outward from a central mass complex.
Cleavage in insects and many other arthropods is superficial i.e., the entire surface layer of egg cytoplasm subdivides into cells, and the egg contains a central mass of uncleaved yolk.
Frontal chest radiograph shows a central mass.
Arrayed around a central mass, a murmuration of outspoken electrons, the affiliation and foci of which are clear, yet from which emerge mysterious patterns and strange attractors.
It is part of a central mountain mass that includes Kawaikini (5,243 feet [1,598 metres]), the island's highest peak, immediately south.
The island consists of a central mountain mass culminating in Snaefell (2,036 feet [621 m]) and extending north and south in low-lying agricultural land.
The objective of the present paper is to study the ballistic gravitational capture performed by the first primary in a system formed by three bodies: a large central mass, the primary, a second small body that is in orbit of the primary, the secondary, and a massless particle that is moving around the two primaries.
In this work it is discussed the possibility of a fine-tuneable contribution to the two way Doppler acceleration either towards, either outwards a given central mass by considering a background described by an expanding locally anisotropic (ELA) metric.
Greek-cross plan, church plan in the form of a Greek cross, with a square central mass and four arms of equal length.
