☙

erg

Convert between ergs and other major units of energy.

The unit of work in the centimeter-gram-second absolute system of units, 1 erg being the work done by a force of 1 dyne acting through a distance of 1 centimeter, = 10⁻⁷ joules. Symbol, erg.

A million ergs was sometimes termed a megalerg.

The name was first proposed by a committee of the British Association for the Advancement of Science.¹ It is based on the classical Greek word ergon (εργον), meaning work.

According to the current national standard in the United States², the erg is not to be used. The joule should be used instead. Nevertheless, in the 21^st century the erg continued to be used in certain fields, particularly by astrophysicists to describe luminosity (see source notes 2 and 3).

1. We provide the report here.

2. IEEE/ASTM SI10-02.
American National Standard for Use of the International System of Units (SI): The Modern Metric System.
New York: IEEE, 30 December 2002.

See Section 3.3.3.

sources

Son emploi n'a pas encore prévalu en pratique, où l'on fait usage de centimètres-grammes, grammètres et kilogrammètres.

It [the erg] has not yet been employed in practice, but gramme-centimètres, grammètres, kilogrammètres, and foot-pounds are used.

Édouard Hospitalier.
Formulaire Pratique de l'Electricien.
Paris: G. Masson, 1883.
Page 32. Translation (1884) by Gordon Wigan.

Flux (10⁻¹⁸ erg cm⁻² s⁻¹ Å⁻¹)

Legend for vertical axis of figure 1a, in
M. D. Lehnert, N. P. H. Nesvadba, J.-G. Cuby, A. M. Swinbank, S. Morris, B. Clément, C. J. Evans, M. N. Bremer and S. Basa.
Spectroscopic confirmation of a galaxy at redshift z ≈ 8.6.
Nature, vol 467, pages 940-942 (20 October 2010). Letter.
doi:10.1038/nature09462

The production rate of peta-electron volt electrons, 2.5 × 10³⁶ ergs per second, constitutes 0.5% of the pulsar spin-down luminosity, although we cannot exclude a contribution of peta-electron volt protons to the production of the highest-energy gamma rays. [page 425]

To explain the peta-electron volt γ-ray luminosity, L_γ ≈ 5 × 10³¹ ergs s⁻¹, the acceleration power of ~10-PeV parent protons would need to be Ẇ_p = W_p/t_esc = κ⁻¹L_γ˙ ≈ 10³⁶ ergs s⁻¹ or, in the case of a broad E⁻²-type proton spectrum, an order of magnitude larger. [Page 430]

The LHAASO Collaboration.
Peta-electron volt gamma-ray emission from the Crab Nebula.
Science, vol 373, issue 6553, pages 425-430. (23 July 2021).

The feature terminates in a bright [O III] knot with a luminosity of ≈1.9 × 10⁴¹ erg s⁻¹.

Pieter van Dokkum, Imad Pasha , Maria Luisa Buzzo, Stephanie LaMassa, Zili Shen, Michael A. Keim, Roberto Abraham, Charlie Conroy, Shany Danieli, Kaustav Mitra, Daisuke Nagai, Priyamvada Natarajan, Aaron J. Romanowsky, Grant Tremblay, C. Megan Urry, and Frank C. van den Bosch.
A Candidate Runaway Supermassive Black Hole Identified by Shocks and Star Formation in its Wake.
The Astrophysical Journal Letters, 946:L50 (14pp), 2023 April 1
DOI 10.3847/2041-8213/acba86