Super-Earth are planets with a mass higher than Earth's but lower than Neptune's, and there is considerable debate as to their internal composition and nature. Some super-Earths may have rocky mantles and iron cores like Earth, while others may have thicker, Neptune like envelopes of volatiles above a rocky core. Whether the transition from rocky mantles to volatile-rich envelopes occurs at an exact planetary mass value is currently unknown, and various methods exist to distinguish rocky bodies from volatile bodies.

1. Density - 1g/cm^3 limit:

- Planets with a density <1g/m^3 are usually considered as volatile-dominated systems, while those with densities >1g/cm^3 are considered rocky.

- However, planets just below 1g/cm^3, are borderline cases and a precise differentiation is difficult.

2. Envelope mass fraction - 10% limit:

- Instead of using density as a metric, envelope mass fraction can be used. Bodies with volatile components making up less than 10% of their total mass are considered rocky.

3. Bulk composition modeling:

- The internal structure of super-Earths can be constrained using forward and inverse modeling techniques.

>Forward model: Assume a planet's mass and radius and calculate its internal structure and composition using reasonable equations of state.

>Inverse model: Use the mass, radius, and other information (such as gravitational moments if available) to invert the planet's composition.

4. Atmospheric signature:

- Depending on their interior, different types of super-Earths may have distinct atmospheric compositions. For example, rocky super-Earths may have thin, CO2-rich atmospheres or even no atmosphere, while volatile-rich super-Earths might have thicker atmospheres with water vapor and other volatiles.

5. Observational constraints:

- Observations from spacecraft such as the Hubble Space Telescope or NASA's Kepler mission can provide information about the radii and masses of transiting exoplanets allowing inferences to be made regarding the composition of objects.

By studying these various properties and comparing them to theoretical models, astronomers can gain a better understanding of the nature and composition of super-Earths and their place in the broader context of exoplanet diversity.