photosphere

American  

[foh-tuh-sfeer] / ˈfoʊ təˌsfɪər /

noun

1. a sphere of light or radiance.

2. Astronomy. the luminous visible surface of the sun, being a shallow layer of strongly ionized gases.

---

photosphere British  

/ ˌfəʊtəʊˈsfɛrɪk, ˈfəʊtəʊˌsfɪə /

noun

1. the visible surface of the sun, several hundred kilometres thick

---

photosphere Scientific  

/ fō′tə-sfîr′ /

1. The lowest visible layer of a star, lying beneath the chromosphere and the corona. Stars are made entirely of gas and thus have no surface per se, but the gas beneath the photosphere is opaque, so the photosphere acts as their effective visible surface; it is also the boundary from which the Sun's diameter is measured. The Sun's photosphere is a very thin layer made up of numerous granules (transient convective cells) where hot gases rise and give off light and heat. The photosphere of the Sun has a temperature of around 6,000°K and is the region in which sunspot activity is located.

---

Other Word Forms

• photospheric adjective

Etymology

Origin of photosphere

First recorded in 1655–65; photo- + -sphere

Example Sentences

It’s only during a total eclipse, when the Moon passes between Earth and the Sun and covers the photosphere that we are able to see the solar corona, the Sun’s outermost layer.

From BBC • Nov. 26, 2024

And last month the agency released the first-ever full-disk images of the Sun in wavelengths ranging from 200 to 400 nanometres, saying they provided "insights into the intricate details of the Sun's photosphere and chromosphere".

From BBC • Jan. 5, 2024

The spacecraft is equipped with seven payloads to study the sun’s corona, chromosphere, photosphere and solar wind, the Indian Space Research Organization said.

From Seattle Times • Sep. 1, 2023

The corona extends millions of kilometers above the photosphere and emits about half as much light as the full moon.

From Textbooks • Oct. 13, 2016

Wherever the telescope is turned all round the sun the lines of luminous gas are seen, showing that they form a complete layer outside the photosphere, or light-giving mass, of the sun.

From Through Magic Glasses and Other Lectures A Sequel to The Fairyland of Science by Buckley, Arabella B.