Common Assessment #10 The Sun And Other Stars

Fusion combination of two nuclei results in the formation of a heavier nucleus, along with a release of energy. example: when nuclei of two H atoms are brought close to each other, then they undergo fusion and form a He nucleus.

Transfer of Thermal (Heat) Energy Conduction: Transfer of thermal energy through direct contact. Convection: Transfer of thermal energy by the circulation or movement through a liquid or gas. Radiation: Transfer of thermal energy as electromagnetic waves.

The Sun is made up of… 70% hydrogen 28% helium 1.5% carbon, nitrogen and oxygen 0.5% all other elements Through the process of fusion, the sun combines H into He.

Solar Characteristics The Sun is 150 million kilometers (93 million miles) away from the Earth (this distance varies slightly throughout the year, because the Earth's orbit is an ellipse and not a perfect circle) It would take 110 Earths strung together to be as long as the diameter of the Sun. The Sun is neither a solid nor a gas but is actually plasma. The core extends about one quarter of the way from the center of Sun, where the temperature is around 15.7 million Kelvin (K), or 28 million degrees Fahrenheit to its surface, which is only 5778 K "cool" The Sun is about 4.5 billion years old Astrophysical theory predicts that the Sun will become a red giant in about five billion (5,000,000,000) years.

The Sun is not stationary Since the Sun is primarily very hot gas, the surface at the equator rotates once every 25.4 days. The rotation near the poles is around 36 days. The image to the right shows a planet orbiting a star. The planet causes the star to wobble to and fro. Using this information, scientists are able to detect whether or not a star has a planet orbiting it.

The image to the left is a diagram of the different layers of the Sun.

Characteristics of the Layers Core: This is the very center of the Sun, where temperatures and pressures are so high that fusion can happen. Radiative Zone: solar material is hot and dense enough that thermal radiation can transfer energy from the interior of the Sun Convective Zone: solar plasma isn’t dense enough to transmit energy through radiation. Instead, heat is moved through convection. Thermal columns carry heat to the surface of the Sun, cool back down and then fall back towards the center of the Sun. Photosphere: about 6,000 Kelvin, and gives off the yellow-white light that we see. Chromosphere: narrow layer above the photosphere that raises in temperature with height. Corona: where the solar wind originates, can be seen only during solar eclipses

Sunspots caused by intense magnetic activity Sunspots develop and persist for periods ranging from hours to months, and are carried around the surface of the Sun by its rotation

Solar Flares A solar flare is a large explosion in the Sun's atmosphere that can release as much as 6 × 1025 joules of energy (The energy level of a solar flare is equal to tens of millions of atomic bombs exploding at the same time!) Solar flares affect all layers of the solar atmosphere (photosphere, chromosphere, and corona) Storms on the sun that send out both rays and particles. Solar flares can impact radio and television signals transmitted on Earth. Solar Flare

The Sun's energy comes from thermonuclear reactions (converting hydrogen to helium) in the core, where the temperature is 15 to 25 million degrees. The energy radiates through the middle layer, then bubbles and boils to the surface in a process called convection. Charged particles, called the solar wind, stream out at a million miles an hour. Magnetic fields within the sun slow down the radiation of heat in some areas, causing sunspots, which are cool areas and appear as dark patches. Sunspot activity peaks every 11 years. The next peak is due in 2012. The magnetic field protects Earth from most of the harmful solar radiation, but extreme flares can disable satellites and disrupt communication signals. The charged particles also excite oxygen and nitrogen in the atmosphere to create the aurora borealis, or northern lights.

When viewing stars far away… Apparent magnitude refers to the brightness of stars as observed from Earth. Absolute magnitude refers to the brightness of stars as if they were all the same distance from the Earth Example: The Sun has an apparent magnitude of -26.74 but an absolute magnitude of 4.83 Sirius has an apparent magnitude of -1.46 but an absolute magnitude of -1.42 This means that from Earth, the Sun is a lot brighter, but if the Sun was replaced by Sirius, Sirius would be 25 times more luminous.

Nebula: Birthplace of stars interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases. Nebulae often form star-forming regions, such as in the Eagle Nebula. This nebula is depicted in one of NASA's most famous images, the "Pillars of Creation” (Below). In these regions the formations of gas, dust, and other materials "clump" together to form larger masses, which attract further matter, and eventually will become big enough to form stars. The remaining materials are then believed to form planets, and other planetary system objects.

Life Cycle of a Star

So…a Recap What is our sun classified as (What type of star?) In order for a star to go “supernova” what conditions must be present? What is the most important factor in determining a stars life cycle? Diameter, color or mass? What is the process of how our sun creates its fuel? What 2 elements are used?

HR Diagram