Ch 7 The Sun Questions

Explain why the presence of spectral lines of a given element in the solar spectrum tells us that the element is present in the Sun, but the absence of the lines would not mean that the element was absent from the Sun.

The absence of particular spectral lines of a given element could only mean that the conditions (such as temperature) aren't right to make the transition associated with that line very probable. This is because some lines require a limited temperature range to first get the atoms to an excited state, from which they then make the transition in question. For example, the hydrogen Balmer series lines cannot be seen (even if hydrogen is present) unless the temperature is not too hot, and not too cold. They are strongest for T near 10,000 K.

What is the source of the sun's energy?

nuclear fusion

Why does oxygen, which is abundant in the sun's atmosphere, have relatively weak spectral lines, while calcium, which is not abundant, has very strong spectral lines?

At these high temperatures, however, much of the hydrogen is ionized, so there are few intact hydrogen atoms to produce strong spectral lines. What's more, the few hydrogen atoms that have managed to retain their single electron are mostly in such highly excited states that their spectral lines are invisible.

Why can't you see deeper into the sun than the photosphere?

Because the light emitted by the external part of the sun is strong enough to mask anything behind it

how are granules and supergranules related? how do they differ?

Both are caused by convection. They differ in size.

Why does nuclear fusion in the sun occur only near the center?

Fusion requires a huge, huge amount of energy to get started, and the center of a star is where the gravitational energy is the greatest. Not only is there the strongest gravity, but there is also the pressure of the outer parts of the star making things even hotter and more energetic

What observations would you make if you were ordered to set up a system that could warn astronauts in orbit of dangerous solar flares? If such a warning system exists.

In fact, there is such a warning system, including data from ground based solar telescopes and from satellite observations. Mostly watch for coronal mass ejections, and then worry about those heading for Earth, as they are quite directional.

What evidence can you give that the solar corona is at a very high temperature?

It emits x-rays

How do astronomers think the solar chromosphere and corona gets heated to their high temperatures?

Magnetic fields carry heat outward from lower layers.

How did neutrino oscillation affect the detection of solar neutrinos?

Neutrino oscillation affected the detection of solar neutrinos because the equipment used to detect the neutrinos was generally designed to detect only 1 kind of neutrino. The "flavor" of the neutrinos scientists expected to be coming from the Sun's fusion reactions were electron-neutrinos, so great vats of fluids (water, chlorine or gallium) were placed deep underground where cosmic rays would not reach them, but electron-neutrinos would occasionally weakly interact with the atoms transmuting oxygen to fluorine, chlorine to argon, or gallium to germanium, and/or releasing photons of a certain energy level. The vats were lined with detectors looking for signs of transmuting nuclei and the expected photons. What they found was about 1/3 electron neutrinos were coming from the Sun than expected, and this was bizarre as solar fusion was a known process and quantity and the number of neutrinos detected should have matched calculations. Before this, most scientists thought neutrinos were massless (like photons) and traveling at the speed of light would not be able to oscillate to other flavors. This required some new hypotheses and testing. Some detectors were upgraded to also detect the other flavors of neutrino: muon and tau neutrinos. When the results came in it appears neutrinos from the same were changing flavors between electron, muon, and tau and the detector were recording the expected numbers of neutrinos. From this, a new theory developed describing neutrinos as have an tiny mass (hundreds of times less than an actual electron) and capable of oscillating between flavors and neutrinos travel slightly slower than light.

What does the spectrum of a solar prominence reveal? What does its shape reveal?

Prominences are arches of charged particles in the chromosphere and corona that are surrounded by magnetic fields. The shape shows how the magnetic field travels.

How does the Babcock model explain the sunspot cycle?

The Babcock model states that the rotational motion of charged particles deep within the sun produces the magnetic field. The sun's surface by the poles rotates slower than the equator, causing the magnetic field to tangle, and eventually the Sun must reverse polarity to untangle the magnetic field

Why does the sun go through 11 and 22 year cycles of activity?

The amount of magnetic flux that rises up to the Sun's surface varies with time in a cycle called the solar cycle. This cycle lasts 11 years on average. This cycle is sometimes referred to as the sunspot cycle. Near the minimum of the solar cycle, it is rare to see sunspots on the Sun, and the spots that do appear are very small and short-lived. During this "solar maximum", there will be sunspots visible on the Sun almost all the time (often there are more than 100 spots visible at a time!), and some of those spots will be very large (up to 50,000 km in diameter) and last several weeks. Magnetic properties of sunspots have a 22 year cycle.

what evidence can you give that the granulation is caused by convection?

The evidence for granulation being caused by convection is that convection is caused by the mottled appearance of the solar photosphere, caused by gases rising from the interior of the Sun.

how can astronomers detect structure in the chromosphere?

The structure of the chromosphere is studied primarily using filtergrams. Filtergrams are images of the sun taken through a filter that lets in a very narrow wavelength band of light, such as light emitted by the Hydrogen-alpha transition.

What would the spectrum of an auroral display look like? and why?

There are thousands of individual colours in the aurora, each resulting from a specific electron cloud energy transition of an excited atmospheric atom, molecule or ion returning toward a 'ground' (= lowest) energy state, but three are dominant. Near the lower border a green atomic oxygen emission generally dominates; at an altitude of 250 km a red emission from atomic oxygen dominates; throughout the aurora a violet emission from a molecular nitrogen ion is significant.

What evidence can you give that sunspots are magnetic?

With the use of a modified spectroheliograph he showed how the magnetic phenomena appeared in pairs of opposite polarity. Zeeman effect

how can solar flares affect earth

aurora borealis, communication blackouts

What are the dark sunspots?

cool spots on sun's photosphere w/ intense magnetic fields

What energy sources on Earth cannot be thought of as stored sunlight?

cosmic, nuclear

what can you learn about the sun by observing its surface and atmosphere?

its composition, temperature, and energy transport

How are astronomers able to explore the layers of the sun below the photosphere?

sunspots, prominences, solar flares, magnetic fields, sunquakes

Why does nuclear fusion require high temperatures

there's a Coulomb barrier, or resistance to collisions because of charge--so they must collide violently