Astronomy 3rd Midterm

How big is the Sun?

880,miles in diameter

How does a star begin?

Solar Nebula Theory

What are an "A.U." Light Year, Parsec?

1 Astronomical Unit = 149 597 871 kilometers. Distance from Earth to Sun. Light Year is a unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 1012 km (nearly 6 trillion miles) 186,000 miles a second. Parsec = Parallectic second of arc = 3.26 Light Years.

What is the Maunder Minimum?

1614-1715 mini ice age. period which no sun spots were visible.

What is C.M.E.? Coronal Mass ejection?

A coronal mass ejection (CME) is a massive burst of gas and magnetic field arising from the solar corona and being released into the solar wind, as observed in a coronagraph.

What is a planetary nebula? How is it formed?

A planetary nebula, often abbreviated as PN or plural PNe, is a kind of emission nebula consisting of an expanding glowing shell of ionized gas ejected from old red giant stars late in their lives.

What is the difference between absolute and apparent magnitude?

Apparent Magnitude: An approximation of distance based on brightness. Absolute Magnitude Scale: Measures brightness of stars based on distance at a standard distance of 10 parsecs away.

how is parallax used to determine the distance of stars?

Astronomers use the principle of parallax to measure distances to the closer stars. Here, the term "parallax" is the semi-angle of inclination between two sight-lines to the star, as observed when the Earth is on opposite sides of the Sun in its orbit.

What are different parts of the Sun? How does the temperate vary from core to outer layers?

Core, photosphere. chromosphere, solar wind, convective zone, radiative zone. Photosphere is 8000 F. Chromosphere is 18,000 F. Corona 15,000,000 F.

Why are dwarf stars difficult to find?

Dwarf stars are small and give of very little light. Which is what makes them so hard to find.

How would stars be plotted on the HR diagram as they reach the end of their lives?

Dwarves are below the main sequence and giants are above the main sequence

What is the crucial factor that determines what kind of star will be formed?

Has to do with the mass and gravity.

What is nucleosynthesis?

How we get heavier elements from lighter elements.

Which last longer: high or low mass stars?

Low mass stars because they use less energy

What is a red giant?

Massive star, lies above the main sequence.

What is a neutron star? What is a pulsar?

Neutron star is a dense ball of neutrons that remains at the core of a star after a supernova explosion. Pulsar is an object that emits radiation in the form of rapid pulses.

What are the spectral classes? Which are the hottest.. coolest?

O B A F G K M. The hottest are the bluest ones which are O and B. The cooler ones are K and M, red and orange.

How can flares affect the Earth?

Radiation, ruins magnetic field

What is color temperature, and what does it have to do with stars?

Red is the coolest, blue is the hottest. So we can determine the spectral class of a star.

What is a white dwarf?

Star near its end, smaller. Below the main sequence.

What is stellar parallax? What is the main limitiation of this distance-measurement technique?

Stellar parallax is parallax on an interstellar scale: the apparent shift of position of any nearby star (or other object) against the background of distant objects. If the stars are too far away, the parallax can be too small to measure accurately.

What are sunspots, prominences, flares?

Sunspots are magnetic storms. Sunspots form on the surface of the Sun and appear visibly as dark spots compared to their surroundings. A solar prominence (also known as a filament) is an arc of gas that erupts from the surface of the Sun. Prominences can loop hundreds of thousands of miles into space. Prominences are held above the Sun's surface by strong magnetic fields and can last for many months. At some time in their existence, most prominences will erupt, spewing enormous amounts of solar material into space. A solar flare is a magnetic storm on the Sun which appears to be a very bright spot and a gaseous surface eruption. Solar flares release huge amounts of high-energy particles and gases and are tremendously hot (from 3.6 million to 24 million °F). They are ejected thousands of miles from the surface of the Sun.

How do high-mass stars end their lives?

Supernova

What is the inverse-square law, and does it have to do with the intensity of starlight?

The inverse square law, the reason why stars appear dimmer if that its intensity decreases as energy moves farther from the star and covers more area.

What part of the Sun generates the solar wind? What does the solar wind consist of?

The solar wind is a stream of plasma released from the upper atmosphere of the Sun. It consists of mostly electrons, protons and alpha particles with energies usually between 1.5 and 10 keV. The stream of particles varies in density, temperature, and speed over time and over solar longitude.

HR Diagram. What are the two axis labeled? Where is the main sequence, dwarfs, and giants on the diagram? Where on the diagram are the hottest and coolest stars?

The two axis labeled in the HR diagram is Luminosity and Spectral Classes (Surface Temperate). Main sequence is in the middle (diagonal), dwarves below the sequence, giants above the sequence. Hottest are blues (O B), Coolest (K M) red.

Why are there a few massive stars?

They die out faster. They just explode.

How do low-mass stars end their lives?

They use up all of their fuel.

How does the Sun generate energy? What is its "fuel"? Where in the Sun does this happen?

Through fusion. It's made of plasma so it's electrically charged. Energy happens in the core of the sun.

What is a variable star, and where are they on the HR diagram?

Variable stars are stars that change brightness. The brightness changes of these stars can range from a thousandth of a magnitude to as much as twenty magnitudes over periods of a fraction of a second to years, depending on the type of variable star. There are just above the main sequence.

What are the different types of binary stars?

Visuals stars, where you see two of them. Spectroscopic (has two that follows each other, one is blue shifted, one is red shifted), Eclipsing (one big one and small one), shows brightness overtime

What is a nova?

a star showing a sudden large increase in brightness and then slowly returning to its original state over a few months.

What is a supernova?

a star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass.

Why doesn't the Sun collapse or explode?

the internal pressure of the plasma holds everything up (think fantastically dense gas in a ballon - wont collapse) The gravity field of the mass holds (almost) everything down - mass ejection can acheive escape velocity.