Exploring the Universe

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Nuclear Fusion Noun

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[noo-klee-er fyoo-zhun]

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Nuclear Fusion

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The process where less massive atomic nuclei combine to form more massive nuclei, releasing an enormous amount of energy.

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Example: This diagram shows two light atomic nuclei (isotopes of hydrogen) combining, or fusing, to form a heavier nucleus (helium), releasing a large amount of energy.

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Core Noun

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[kor]

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Core

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The central region of a star, such as the sun, where extreme temperature and pressure allow nuclear fusion to occur.

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Example: This diagram shows the Earth's core, which is divided into a solid inner core and a liquid outer core, located beneath the mantle.

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Photosphere Noun

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[foh-tuh-sfeer]

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Photosphere

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The innermost layer of a star's atmosphere that is visible to observers and is considered its apparent surface.

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Example: This diagram shows the Sun's layers, identifying the photosphere as the thin, visible surface located between the inner convective layer and the outer chromosphere.

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Corona Noun

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[kuh-roh-nuh]

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Corona

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The outermost, extremely hot, and low-density layer of a star's atmosphere, visible during a total solar eclipse.

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Example: This diagram shows the layers of the Sun, identifying the corona as the outermost, wispy layer of its atmosphere, visible around the main body.

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Solar Wind Noun

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[soh-ler wind]

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Solar Wind

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A continuous stream of electrically charged particles that flows outward from the sun's corona through the entire solar system.

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Example: The Sun releases a stream of charged particles called the solar wind, which travels through space and is deflected by Earth's magnetic field.

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Sunspot Noun

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[sun-spot]

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Sunspot

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A temporary, cooler, and darker region on the sun's photosphere caused by intense magnetic field activity interfering with convection.

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Example: This image shows dark, cooler areas on the Sun's surface called sunspots and compares their massive size to the size of the entire planet Earth.

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Solar Flare Noun

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[soh-ler flair]

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Solar Flare

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A sudden and intense eruption of energy from the sun's surface, often near sunspots, releasing radiation and charged particles.

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Example: This image shows a massive, bright eruption of energy and light from the sun's surface, which is a solar flare.

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Light-Year Noun

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[lite-yeer]

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Light-Year

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An astronomical unit of distance equal to the distance that light travels in a vacuum in one Julian year.

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Example: This diagram shows that a light-year is a unit used to measure the vast distance between stars, such as the 4.2 light-years between our Sun and Proxima Centauri.

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Parallax Noun

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[par-uh-laks]

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Parallax

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The apparent shift in the position of a nearby object against a distant background when viewed from different locations.

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Example: This diagram shows how a nearby star appears to shift its position against distant background stars when viewed from Earth at different times of the year.

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Apparent Brightness Noun

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[uh-pair-ent brite-ness]

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Apparent Brightness

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The measure of a star's brightness as it is observed from Earth, which depends on its luminosity and distance.

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Example: As light from a source (S) travels farther away, it spreads over a larger area. This makes the source's apparent brightness decrease with distance.