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The temperature of the Sun is over 5，000degrees Fahrenheit at the surface，but it rises to perhaps more than 16million degrees Fahrenheit at the center.The Sun is so much hotter than the Earth that matter can exist only as a gas，except at the core.In the core of the Sun，the pressures are so great against the gases that，despite the high temperature，there may be a solid core.However，no one really knows，since the center of the Sun can never be directly observed.
Solar astronomers do know that the Sun is divided into five layers or zones.Starting at the outside and going down into the Sun，the zones are the corona，chromosphere，photosphere，convection zone，and finally the core.The first three zones are regarded as the Sun’s atmosphere.But since the Sun has no solid surface，it is hard to tell where the atmosphere ends and the main body of the Sun begins.
The Sun’s outermost layer begins about 10，000miles above the visible surface and goes outward for millions of miles.This is the only part of the Sun that can be seen during an eclipse such as the one in February 1979.At any other time，the corona can be seen only when special instruments are used on cameras and telescopes to shut out the glare of the Sun’s rays.
The corona is a brilliant pearly white，filmy light，as bright as the full Moon.Its beautiful rays are a sensational sight during an eclipse.The corona’s rays flash out in a brilliant fan that has wispy spike-like rays near the Sun’s north and south poles.The corona is thickest at the Sun’s equator.
The corona rays are made up of gases streaming outward at tremendous speeds and reaching a temperature of more than 2million degrees Fahrenheit.The rays of gas thin out as they reach the space around the planets.By the time the Sun’s corona rays reach the Earth，they are weak and invisible.

Considering that anxiety makes your palms sweat，your heart race，and your brain seize up like a car with a busted transmission，it’s no wonder people reach for the Xanax to vanquish it.But in a surlmse，re-searchers who study emotion regulation-how we cope，or fail to cope，with the daily swirl of feelings-are discovering that many anxious people are bound and determined （though not always consciously）to cultivate anxiety.The reason，studies suggest，is that for some people anxiety boosts cognitive performance.
In one recent study，psychologist Maya Tamir of Hebrew University in Jerusalem gave 47undergraduates a standard test of neuroticism，which asks people if they agree with such statements as ’I get stressed out easily.’She then presented the volunteers with a list of tasks，either difficult （giving a speech，taking a test）or easy （washing dishes），and asked which emotion they would prefer to be feeling before each.The more neurotic subjects were significantly more likely to choose feeling worried before a demanding task；non-neurotic subjects chose other emotions.Apparently，the neurotics had a good reason to opt for anxiety：when Tamir gave everyone anagrams to solve，the neurotics who had just written about an event that had caused them anxiety did better than neurotics who had recalled a happier memory.Among non-neurotics，putting themselves in an anxious frame.of mind had no effect on performance.
In other people，anxiety is not about usefulness but familiarity，finds psychology researcher Brett Ford of the University of Denver.She measured the ’trait emotions’（feelings people tend to have most of the time）of 139undergraduates，using a questionnaire that lists emotions and asks ’to what extent you feel this way in general.’She then grouped the students into those characterized by ’trait fear’（those who tended to be anxious，worried，or nervous），’trait anger’（chronically angry，irritated，or annoyed），and ’trait happy’（the cheerful，joyful gang）.Six months later，the volunteers returned to Ford’s lab.This time she gave them a list of emotions and asked which they wanted to experience.Not surprisingly，the cheerful bunch wanted to be happy.But in a shock for those who think anyone who is chronically anxious can’t wait to get thek hands on some Ativan （氯羟安定），those with ’trait fear’said they wanted to be worried and nervous-even though it felt subjectively unpleasant.（The ’trait angry’students tended to prefer feeling the same way，too.）Wanting to feel an emotion is not the same thing as enjoying that emotion，points out neuroscientist Kent Berridge of the University of Michigan，who discovered that wanting and liking aremediated by two distinct sets of neurotransmitters.
In some cases，the need to experience anxiety can lead to a state that looks very much like addiction to anxiety.’There are people who have extreme agitation，but they can’t understand why，’says psychiatrist Harris Stratyner of Mount Sinai School of Medicine in New York.They therefore latch on to any cause to explain what they’re feeling.That rationalization doubles back and exacerbates the anxiety.’Some people，’
he adds，’get addicted to feeling anxious because that’s the state that they’ve always known.If they feel a sense of calm，they get bored；they feel empty inside.They want to feel anxious.’Notice he didn’t say ’like.’