Assignment 1 (Week 2) Dec 29

[Head Mistress]

Post all answers below. Thanks

IBC- O 30 points
Jessica - O 30 points
Phillip- O 30 points
Flore - 30 points

[ibc]

well...what i kno about the photosjpere is that it is an astronomical object and the photoshpere is the region where an oject stops being tranparent to ordinary light and uhh...the suns photosphere has a temepature of about 5800 kelvins which means the temapature is absolute zero
and its circle

[jessica]

The Photosphere is the part of the star where you finally see visible light. It is often referred to as the surface of the star.

Complements of Winkipedia.

A picture of where exactly it is located is shown above.
Since stars are believed to have no actual solid surface, this region is typically used to describe the Sun or another Star’s visual surface. This region of the star has a temperature of 5800 Kelvins. The photosphere is composed of granules. These granules are about the size of an earth continent but live much shorter. They usually last a few minutes only to be replaced by a new granule. A process called granulation is evidence of convection on the sun. The photosphere is really just gas, denser at the bottom then at the top. In the photosphere, granulation, supergranulation, faculae, and sunspots are seen.
The photosphere is also a thin layer, producing radiation transmitted into space. It is about 100 kilometers. Temperatures range from 6600 Kelvin to 4300 Kelvin. The density is 1 hundred millionth of water, and pressure is one hundredth of an atmosphere. In the photosphere, negatively ionized hydrogen is formed which is an effective scatterer. Then the negatively ionized hydrogen drops off rapidly above the photosphere. Absorption lines are also formed at the photosphere. They form at different heights in the atmosphere, so they can be used to map different layers in the photosphere, velocity along the line can be deduced by line broadening.

[Phillip]

The photosphere of an astronomical object is the region at which the optical depth becomes one for a photon of wavelength equal to 500 nanometers. (Photo means light, hence the term photosphere.) In other words, the photosphere is the region where an object stops being transparent to ordinary light. Because stars are believed to have no solid surface, the photosphere is typically used to describe the Sun or another star's visual surface.

The Sun's photosphere has a temperature of about 5800 kelvins; other stars may have hotter or cooler photospheres. The Sun's photosphere is composed of convection cells called granules—firestorms each approximately 1000 kilometers in diameter with hot rising gas in the center and cooler gases falling in the narrow spaces between them. Each granule has a lifespan of only about eight minutes, resulting in a continually shifting "boiling" pattern. Amid the typical granules are supergranules up to 30,000 kilometers in diameter with lifespans of up to 24 hours. It is unknown whether these features are typical of other stars.

The Sun's visible atmosphere has other layers above the photosphere: the 10,000 kilometer-deep chromosphere (typically observed by filtered light, for example H-alpha) lies just between the photosphere and the much hotter but more tenuous corona. Other "surface features" on the photosphere are solar flares and sunspots.

[flore]

Photosphere
The apparent, visible surface of the Sun. The photosphere is a gaseous atmospheric layer a few hundred miles deep with a diameter of 864,000 mi (1,391,000 km; usually considered the diameter of the Sun) and an average temperature of approximately 5800 K (10,500°F). Radiation emitted from the photosphere accounts for most of the solar energy flux at the Earth.

Convective cells give the photosphere a granular appearance with bright cells (hot rising gas) surrounded by dark intergranular lanes (cool descending gas). A typical granule is approximately 600 mi (1000 km) in diameter. Measurements of horizontal velocity reveal a larger convective pattern, the supergranulation; the horizontal motion of individual granules reveals intermediate-scale convective flows

[Phoenixtears]

[glow=red,2,300]The Photosphere of a Star[/glow]

The visible surface of the Sun, the photosphere, is the layer below which the Sun becomes opaque to visible light. Above the photosphere visible sunlight is free to propagate into space, and its energy escapes the Sun entirely. The change in opacity is because of the decreasing overall particle density: the photosphere is actually tens to hundreds of kilometers thick, being slightly less opaque than air on Earth. Sunlight has approximately a black-body spectrum that indicates its temperature is about 6,000 K (10,340°F / 5,727 °C), The photosphere has a particle density of about 1023 m−3 (this is about 1% of the particle density of Earth's atmosphere at sea level).

During early studies of the optical spectrum of the photosphere, some absorption lines were found that did not correspond to any chemical elements then known on Earth. In 1868, Norman Lockyer hypothesized that these absorption lines were because of a new element which he dubbed "helium", after the Greek Sun god Helios. It was not until 25 years later that helium was isolated on Earth.

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[Hannah]

What I know about the photosphere is:-

That the Sun has basically the same chemical elements as found on Earth. However, the Sun is so hot that all of these elements exist in the gaseous state.

There is not really a "surface" to the Sun. Think of it this way: the Sun is a bunch of gas which gets denser and denser as you move from space toward the solar core. The photosphere would then represent the depth at which we can see no deeper toward the core. Think of what a thick cloud looks like when you look down on it from an airplane - it looks solid, but it isn't.

The Photosphere


The Parts of a Star

The Sun's atmosphere changes from being transparent to being opaque over a distance of only a few hundred kilometers. This is remarkable given the size of the Sun, and represents such a huge change that we often think of it as a true boundary. When we speak of the size of the Sun, we usually mean the size of the region surrounded by the photosphere. The photosphere is slightly different from one place on the Sun to another, but in general is has a pressure about a few hundredths of the sea-level pressure on Earth, a density of about a ten-thousandth of the Earth's sea-level atmospheric density, and a temperature in the range 4500-6000 Kelvin.