astronomy test 2

- **Solar Energy**:

Energy produced by the Sun, primarily through nuclear fusion in its core, which releases energy in the form of light and heat.It can be harnessed using technologies like solar panels and solar thermal systems.

- **The Proton-Proton Chain**

: A series of nuclear reactions in which hydrogen nuclei (protons) fuse to form helium, releasing energy in the form of light. It is the dominant energy-producing process in stars like the Sun.

- **E=mc²**:

Einstein's famous equation that shows the relationship between mass (m) and energy (E), where c is the speed of light. This equation explains how small amounts of mass can be converted into vast amounts of energy, as seen in nuclear reactions like those in the Sun.

- **Neutrinos**:

Subatomic particles produced during nuclear fusion in the Sun's core, which escape and travel through space. They are very difficult to detect but carry important information about the Sun’s internal processes.

- **Hydrostatic Equilibrium**:

A balance between the inward force of gravity and the outward pressure from the Sun's hot gases. This equilibrium keeps the Sun stable over time.

- **Core**:

Where nuclear fusion occurs.

- **Radiative Zone**:

Energy is transported outward by radiation.

- **Chromosphere**:

The layer above the photosphere, visible during solar eclipses as a red, thin layer.

- **Corona**:

The outermost part of the Sun’s atmosphere, visible during a total solar eclipse, much hotter than the surface.

- **Modeling the Interior of the Sun**:

Scientists use computer models to simulate the Sun's internal processes, such as fusion, temperature gradients, and energy transport, as direct observation is not possible.

- **Helioseismology**:

The study of the Sun's oscillations (sound waves) to infer its internal structure, similar to how seismology is used to study Earth's interior.

-sun Size**:

Diameter of approximately 1.4 million km.

- sun **Mass**:

About 1.99 × 10^30 kg.

- **suns Core Temperature**:

Around 15 million K.

- **sun Surface Temperature**:

About 5,500°C.

suns Composition**:

About 74% hydrogen, 24% helium, and 2% heavier elements.

- **Solar Atmosphere**:

Consists of the photosphere, chromosphere, and corona, each with different characteristics and temperatures.

- **Sunspots**:

Dark, cooler areas on the Sun's surface caused by magnetic activity. They are cooler than the surrounding photosphere and form due to magnetic fields

- **Sunspot Cycle**:

The periodic increase and decrease in sunspot activity, with a cycle length of about 11 years.

- **Solar Rotation (Differential Rotation)**:

The Sun rotates faster at the equator than at the poles, a phenomenon known as differential rotation.

- **Prominences**:

Large, loop-like eruptions of gas in the Sun’s atmosphere.

- **Solar Flares**:

Sudden bursts of energy and radiation from the Sun's surface that can affect space weather.

- **Solar Wind**:

A stream of charged particles (mainly electrons and protons) emitted by the Sun into space.

- **Coronal Mass Ejections (CMEs)**:

Large expulsions of plasma and magnetic field from the Sun's corona, which can affect Earth’s magnetic field and cause geomagnetic storms.

- **Parallax**:

The apparent shift in the position of a star when viewed from two different points of Earth’s orbit.

- **Parsec**:

A unit of distance used in astronomy, equivalent to 3.26 light-years, defined as the distance at which a star has a parallax angle of one arcsecond.

- **Proper Motion**:

The apparent movement of a star across the sky, measured in angular terms over time.

- **Luminosity**:

The total energy emitted by a star per second (its intrinsic brightness).

- **Apparent Brightness**:

The brightness of a star as seen from Earth, which depends on its luminosity and distance from Earth.

- **Wien’s Law**

states that the wavelength at which a star’s emission is strongest is inversely proportional to its temperature.

- **Brown Dwarfs//failed stars**:

not hot enough for hydrogen or nuclear fusion to take place ;
still more massive than planets

- **Indirect measurement**

uses luminosity and temperature to estimate size.

- **Main Sequence**:

A region on the H-R diagram where most stars, including the Sun, spend the majority of their lives, fusing hydrogen into helium.

- **Red Dwarfs**:

Smallest, cool stars in the lower right of the H-R diagram.

- **White Dwarfs**:

Small, hot stars in the lower left of the H-R diagram. not very luminous due to their size

- **Red Giants**:

Large, cooler stars in the upper right.

- **Blue Giants**:

Large, hot stars in the upper left.

- **Stellar Lifetime**:

The lifetime of a star depends on its mass; more massive stars burn their fuel more quickly and have shorter lifetimes.

- **Dark Nebulae**:

Dense clouds of gas and dust that block light from background stars.

- **Emission Nebulae**:

Clouds of gas that emit light due to nearby hot stars.

- **Reflection Nebulae**:

Clouds that scatter the light from nearby stars, making them appear blue.

- **Dust Emits Infrared Light**:

Dust grains in the interstellar medium re-emit absorbed starlight as infrared radiation.

- **ISM Composition**:

The interstellar medium consists of gas (mainly hydrogen) and dust, with regions of ionized gas (HII regions), neutral gas (HI), and molecular clouds.

- **Bipolar Jets**:

Jets of gas ejected from young stars along their rotation axis during formation.

- **Protostar on Hayashi Track**:

A phase in star formation where a protostar contracts and heats up, but still has a temperature gradient.

- **Protostar Energy from Gravity**:

Early energy in a protostar comes from gravitational contraction rather than fusion.

- **Triple-Alpha Process**:

A fusion process where three helium nuclei (alpha particles) fuse to form carbon.

- **White Dwarf**:

A small, dense remnant of a low-mass star after it has shed its outer layers.

nebula

gas and fuzzy stuff in the sky

stars move off the main sequence

when their cores stop producing energy

fragmentation:

a molecular cloud contracts and fragments into stars

 interstellar extinction 

 when dust makes a star appear fainter:

when dust makes a star redder:

interstellar reddening

interstellar medium

interstellar reddening

sun surface temp

5,500 celcius

sun core temp

15 million k

photosphere

most often visible layer of sun

granular convection cells that make up the suns photosphere are

1000 km wide

helium fusion occurs at

100 million degrees

nuclear fusion starts at

10 million degrees