planetesimal

American  

[plan-i-tes-uh-muhl] / ˌplæn ɪˈtɛs ə məl /

noun

1. one of the small celestial bodies that, according to one theory planetesimal hypothesis, were fused together to form the planets of the solar system.

---

adjective

1. of or relating to a planetesimal or planetesimals.

planetesimal Scientific  

/ plăn′ĭ-tĕs′ə-məl /

1. Any of innumerable small bodies of accreted gas and dust thought to have orbited the Sun during the formation of the planets.

2. ◆ The theory that explains the formation of the solar system in terms of the aggregation of such bodies is known as the planetesimal hypothesis. According to this theory, first proposed in 1900, the planetesimals formed within a spiral disk of dust and gas surrounding a central nucleus. Their gravitational attraction eventually caused the planetesimals to coalesce into protoplanetary disks from which larger objects such as planets, asteroids, and satellites were formed, while the nucleus coalesced into the Sun.

---

Etymology

Origin of planetesimal

First recorded in 1900–05; planet + (infinit)esimal

Example Sentences

"It will be important to search for mound-like structures on the planetesimals these missions observe to see how common this phenomenon is, as a further guide to planetesimal formation theories," Stern said.

From Science Daily • Oct. 3, 2023

"In this model, 'Oumuamua began as an icy planetesimal that was irradiated at low temperatures by cosmic rays during its interstellar journey, and experienced warming during its passage through the Solar System."

From Salon • Mar. 26, 2023

“This provides further support that Oumuamua originated as a planetesimal relic broadly similar to solar system comets.”

From New York Times • Mar. 22, 2023

“I’m confident in this being a major advance in our understanding of planetesimal formation, but someone will probably ask, ‘Well, this is just one object.

From Scientific American • Feb. 20, 2020

The evidence, except as to the asteroids and Mercury, is not favorable to the planetesimal hypothesis, unless we make special assumptions as to the distribution of materials in the spiral nebulae.

From Popular Science Monthly Oct, Nov, Dec, 1915 — Volume 86 by Anonymous