The Sun Our Closest Star

Kevin S Mogk

The Sun A Cultural Look !   Many cultures have sun gods and the sun is seen as the giver of

life.

!   We feared the Sun would not return in the morning

!   We feared the Sun would continue to descent out of the sky at the winter Solstice.

CHARTRAND, 2011

A Word for Sun

!   Sun derives from the Proto-Germanic “sunne” (GARLICK, 2008)

!   We also use the roots !   “Sol” from Latin

!   “Helios” from Greek

!   (CHARTRAND, 2011)

!   And the symbol (CHARTRAND, 2011)

And in this Corner, The Sun!!

!   Angular diameter: 32 arc min.

!   Light distance to Earth: 8.32 light minutes

!   Radius: 696,000 km, or 109 Earth radii

!   Mass: 1.9891 x 1030 kg, or 3.33 x 105 Earth masses

!   Luminosity: 3.86 x 1026 Watts (Joules per second)

FREEDMAN and KAUFMANN III, 2005

Weighing in at:

!   Composition by mass:

!   74% Hydrogen

!   25% Helium !   1% other

!   Composition by N° of atoms

!   92.1% Hydrogen

!   7.8% Helium

!   0.1% other

FREEDMAN and KAUFMANN III, 2005

With a top speed of:

!   Rotation

!   At Equator: 25 days

!   Towards Poles: 35 days

!   Distance to Centre of Galaxy: 8000 pc, or 26,000 ly

!   Orbital period: 220 million years

!   Orbital speed 220 km/s

FREEDMAN and KAUFMANN III, 2005

How Do We Study the Sun? !   Carefully! It’s at a magnitude

of -26.7 (CHARTRAND, 2011)

!   With special telescopes and techniques

!   Helioseismology studies the vibrations in the sun. It is how we look inside the Sun.

!   Magnetic Field observations

!   Certain wavelengths !   Visible Light !   Hα !   Calcium k-lines

FREEDMAN and KAUFMANN III, 2005

How does the Sun “Burn”?

!   Mid 1800’s Kelvin-Helmholtz contraction model !   Gravity causes gasses to compress and heat up

!   Untrue because star would be larger in the recent past and our star would only be 25 million years old.

FREEDMAN and KAUFMANN III, 2005

A Chemical Model

!   Chemical burning release 10-19 J/atom

!   To generate the L  of  3.86  x  1026  W  we  need  3.9  x  1045  atoms/second  

!   Sun  Contains  1057  atoms  and  would  burn  out  in  about  9,500  years.

FREEDMAN and KAUFMANN III, 2005

Thermonuclear Fusion!

!   Energy released in atom fusion is about 4.3 x 10-12 J

!   To give the Sun’s luminosity, the Sun must convert 600 million tons of hydrogen each second.

!   At this rate Sun has been burning for about 4.6 billion years and can continue for another 6 billion or so.

FREEDMAN and KAUFMANN III, 2005

Proton, Proton … Neutrino!

!   How do we know the Sun works by fusion?

!   The proton, proton chain release neutrinos as well as energy.

!   These near massless particles are hard to detect, but have been detected with neutrino detectors far underground such as the Sudbury Neutrino Observatory.

McMILLAN and CHAISSON, 2011

Layers of the Sun !   Core

!   0 to 0.25 R Energy production

!   15 million k

!   Radiative zone !   0.25 to 0.71 R radiative

difusion of energy dominates

!   Convective zone !   0.71 to 1 R convection

dominates as means of spreading energy

FREEDMAN and KAUFMANN III, 2005

Or So We Thought

!   Press Release from Space Ref

!   Using the Solar Dynamic Observatory’s (SDO) Helioseismic and Magnetic Imager (HMI)

!   Looked at four different depths of the convective layer

!   Results didn’t match a single layer of circulation from equator to pole close to surface and a return at the bottom of the convective layer.

SpaceRef, 2013

Two is Better Than One

!   Instead two layers of circulation (or cells) one on top of the other.

SpaceRef, 2013

Layers of the Solar Atmosphere

!   Photosphere !   400 km thick !   5,800 to 4,400 k

!   Chromosphere !   Extends 2,000 km above

photosphere !   Temp. rise to 25,000 k

!   Corona !   Extends 10,000 km above

photosphere !   Temperature rise to 2 or

3 million k

FREEDMAN and KAUFMANN III, 2005

The Quiet Sun

!   Granule !   1,000 km wide

!   Supergranules !   35,000 km wide

!   Spicules !   Rising gas from edge of

granules

!   Solar Wind !   Stream of charged

particles from the Sun

The Active Sun !   Sunspots

!   Cooler regions of photosphere

!   Plages

!   Flares !   Large eruptions of gasses from

sunspots

!   Coronal Mass Ejections (CME) !   Huge solar eruptions

!   Filaments/prominences !   Long plasma arches wrapped

up in mag. field lines

The Sunspot Cycle

Image Credit: NASA/Marshal Space Flight Centre

FREEDMAN and KAUFMANN III, 2005

The Maunder Minimum

Image Credit: NASA/Marshal Space Flight Centre

Marshal Space Flight Centre, 2013

A New Look at the Maunder Min.

“Revisited Sunspot Data: A New Scenario for the Onset of the Maunder Minimum”

in The Astrophysical Journal Letters

!   José M. Vaquero, M.C. Gallego of Universidad de Extramadura, Spain

!   Ilya G. Usoskin of the University of Oulu, Finland

!   Gennady Kovaltsov of the Ioffe Physical-Technical Institute of RAS, Russia

VAQUERO et al., 2011

Why They Did It

!   Before the Maunder minimum there was a large spike in solar sunspot activity that could not be explained in dynamo models without serious bending and stretching of figures and models

!   They wanted to see if new data could improve the correlation between observed sunspots before the Maunder min. and solar models.

What They Did

!   Scrutinized old data for sunspot counts

!   Found new sources from that time period

!   Threw out erroneous data

!   Recalculated the sunspot numbers

What They Found

!   The spike disappears and there is a gradual falling into and climbing out of the Maunder minimum that correlates with current dynamo models of the Sun and its cycles.

How We Continue to Refine Our Image of the Sun

“Developing an Advanced Automated Method for Solar Filament Recognition and Its Scientific Application to

Solar Cycle of MLSO Hα Data”

In Solar Physics

!   Q. Hao, C. Fang and P. F Chen. of Nanjing University, China

HOA et al., 2013

Why They Did It

!   There are several algorithms to look at and sort full disk images of the Sun in Hα, but they often only pull out one or two pieces of data. They wanted to pull more data out with their algorithms.

!   They also wanted to see filament migration during a solar cycle.

What They Did

!   Wrote an algorithm that could scan images for certain features simultaneously and pull out the information into text files

!   Their system will recognize filaments and determine several features (position, area, spine, and other data).

!   It can also trace daily evolution of filaments.

The Test

!   They put their algorithm to the test looking at over 3,000 images from the MLSO Hα archives, between 1998 and 2009 (Solar cycle 23)

!   They wanted to pull out features, but also plot the emergence and migration of the filaments over that time period.

The Results

!   Amazing

!   84% accuracy in recognizing features and 80% accuracy in tracing movements.

!   They also found that from 1998-2001 (solar max.) the drift velocity of the filaments was quite fast.

!   From 2001-2006 the drift velocity was slower.

!   After 2006-2009 (solar min.) the drift migration is divergent.

Join in the Fun

!   Sketching or photographing sunspots is a great day time way to keep up with astronomy in the summer.

!   Counts sunspots with R=10g+s !   R is relative number of sunspots

!   G is sunspot groups

!   S is single sunspots

!   Submit your observations to the AAVSO website under the solar section!

HAY, 2013

Website

www.http://home.cc.umanitoba.ca/

~ummogk/sunresearch.html

Works Cited

!   CHARTRAND, Mark R. 2011. National Audubon Society Field Guide to the Night Sky. Toronto/New York: Alfred A: Knopf. 714 pp.

!   FREEDMAN, Roger; KAUFMANN III, William. 2005. Our Star, the Sun. In Universe. 18: 377-406. New York: W. H. Freeman Company. 693 pp. 7th ed.

!   GARLICK, Mark A. 2008. Astronomy: A Visual Guide. Sydney, Australia: Firefly Books. 302 pp.

!   HAY; Kim. 2013. Solar Observing. In Observer’s Handbook 2013. 186-188. Ed. David M. F. Chapman. Canada: Webcom Inc. 352 pp.

!   HOA, Q.; FANG, C.; CHEN P. F. 2013. SoPh. 286: 386-404

Works Cited (Cnt’d)

!   Marshal Space Flight Centre. 2013. The Sunspot Cycle. http://solarscience.msfc.nasa.gov/SunspotCycle.shtml Consulted 2013-10-06.

!   McMILLAN, Steve; CHAISSON, Eric. 2011. The Sun. In Astronomy Today. 16: 385-415. San Francisco: Pearson Addison-Wesley. 725 pp. 7th ed.

!   SpaceRef. 2013. Improving Predictions of the Sun’s Solar Cycle. http://spaceref.com/sun/improving-predictions-of-the-suns-solar-cycle.html Consulted 2013-09-26

!   VAGUERO, José M.; GALLEGO, M. C.; USOSKIN, Ilya G.; KOVALSTOV, Gennady A. 2011. ApJ 731: L24