Monday, August 21, 2017

Solar Eclipse 2017 - inside the science of the rare event

Scientists are able to observe layers of the Sun's atmosphere during a solar eclipse that they cannot image otherwise.The corona,the outermost layer of the Sun,is a halo of gas streaming out from the Sun's surface in plumes and loops.Eclipse observing will help to solve the question of why the corona is hotter than the Sun's surface.Remember that it is cooler the farther away you get from a stove;that is not the case with the Sun,where the opposite is occurring.The photosphere surface of the Sun that emits sunlight is an average of 5500 degrees Centigrade;but the corona above it is up to millions of degrees C.Studying the corona during an eclipse and measuring how quickly the coronal gas oscillates can help distinguish between the general classes of ideas about this problem or perhaps ascertain that both processes are occurring:
1.The nanoflame hypothesis is a model that suggests that millions of tiny explosions could combine to heat up the corona.Millions of the flares going off per second ,each with a billionth as much energy as a large flare,would keep the corona broiling hot.
2.Magnetic or Alfven waves propagate through coronal loops,interacting with one another and dissipating some of their energy,either in the lower ends of the loop or throughout the corona.*
Rapid readouts with Charge-Coupled Devices,or CCDs,on ground-based telescopes will capture images several times per second-much faster than space telescopes can.*
NASA is funding 11 proposals:six for coronal studies and five for the response of Earth's atmosphere to dramatic eclipse cooling.A variety of observations from ground and space will provide the most comprehensive study ever made of the infrared corona,its spectrum and its polarisation.*
Combining ground-based observations with those from satellites in the visible,UV,X-ray and radio parts of the spectrum will provide the most complete view of the solar atmosphere ever obtained.*
A small group of scientists will use the small pixels and precise calibration of CCD detectors to test Einstein's theory of relativity by looking for evidence that the Sun's mass is bending the light of distant stars behind it,an effect caused by the relativistic warping of space-time.
First,the telescopes will be calibrated by measuring several nighttime star images.Because of the ESA's newly-released catalog of star positions,we know their positions with very high precision,so we can look for any deflections caused by the Sun more easily,with fewer calibrations of the telescopes.