Physics 320: Astronomy and Astrophysics – Lecture X

NJIT

Physics 320: Astronomy and Astrophysics – Lecture X

Carsten DenkerPhysics DepartmentCenter for Solar–Terrestrial Research

November 5th, 2003NJIT Center for Solar-Terrestrial Research

Problem 9.9

photon2 2

2 2photon

photon

Electron is initially at rest in reference frame.

1 if 0 1 0!

ee e e

e e

Em v

m vc m c m ccE m c m c

v v Ec


Problem 9.12

0

2 23 3

sds

At wavelength where the opacity is greatest, the value of s is smallest. If the temperature of the star’s atmosphere increases outward, than a smaller value of s corresponds to looking at a higher temperature and a brighter gas. At wavelength where the opacity is greatest, you would therefore emission lines.


Problem 9.13A large hollow spherical shell of hot gas will look like a ring if you can see straight through the middle of the shell. That is, the shell must be optically thin, and an optically thin hot gas produces emission lines. Near the edges of the shell, where your line of sight passes through more gas, the shell appears brighter and you see in a ring. In 1992 a tremendous explosion occurred in the

constellation of Cygnus. Dubbed Nova Cygni 1992. Astronomers hypothesize that this system's white dwarf had so much gas dumped onto it's surface that conditions became ripe for nuclear fusion. The resulting thermonuclear detonation blasted much of the surrounding gas into an expanding shell.


Exhibition Title Contest Ian

Journey to the Center of our/your Universe

Voyage to the Center of our Solar System

The Sun: More than a Reason to Skip Class

Our Sun: What can it do for you?

Brick City Sun The Key to Live on Earth: The

Sun Our Sun: The Orb of Life The Giant Nuclear Reactor:

The Sun

John The Sun: Our

Closest Star The Sun: A Look

inside our Closest Star

Gerardo, Matthew, & Mike Sunbelievable

Solar Sciene


The SunThe Solar Interior

Mass Luminosity Radius Effective Temperature Surface Composition

The Solar AtmosphereThe Solar Cycle


Sun – OverviewMass (kg) 1.989e+3

0Mass (Earth = 1) 332,830

Equatorial radius (km) 695,000

Equatorial radius (Earth = 1) 108.97

Mean density (gm/cm3) 1.410

Rotational period (days) 25-36

Escape velocity (km/sec) 618.02

Luminosity (ergs/sec) 3.827e33

Magnitude (Vo) -26.8

Mean surface temperature 6,000°C

Age (billion years) 4.5

Principal chemistry

Hydrogen Helium Oxygen Carbon Nitrogen Neon Iron Silicon Magnesium All others

92.1%7.8%

0.061%0.030%0.0084%0.0076%0.0037%0.0031%0.0024%0.0030%


Evolution of the Sun and its InteriorStandard Solar Model:

X: 0.71 0.34

Y: 0.27 0.64

Sun–Earth Connection?


pp–Chain

Solar Neutrino Problem!


Interior Structure


Convection Condition

ln 2.5lnd Pd T

The Sun is purely radiative below r/R = 0.71 and becomes convective above that point. Physically this occurs because the opacity in the outer layers of the Sun becomes large enough to inhibit the transport of energy.


Differential Rotation and Magnetic Fields


Helioseismology


Photosphere


Sunspots – Umbra and Penumbra


Active Regions

Active region 9169 was the host of the largest sunspot group observed so far during the current solar cycle. On 20 September 2000, the sunspot area within the group spanned 2,140 millionths of the visible solar surface, an area a dozen times larger than the entire surface of the Earth!


Spectrum of Granulation

“Wiggly” spectral lines in the solar photosphere inside and outside a region of activity, reflecting rising and sinking motions in granulation. Over the central one third of the spectrogram height, the slit crossed a magnetically active region. Here, the velocity amplitudes are much reduced, demonstrating how convection is disturbed in magnetic areas.


Model of Convection

3D animation of convection. The animation shows temperature fluctuations in a layer of unstable, turbulent gas. (Courtesy of Andrea Malagoli, University of Chicago)


Supergranulation


Photospheric Magnetic Fields


Sunspots – Pores & Filigree


Thin Flux Tube Model


Magnetic Carpet


Chromosphere


Mercury Transit November 15th, 1999

The images were taken 20 seconds apart from 21:11 (first contact) to 22:10 UT (last contact). The image were captured with a Kodak MegaPlus 4.2 CCD camera. The spatial resolution is about 1 per pixel. Here, we show only a small portion of the full disk images near the solar north pole. The field of view is approximately 470 170 or 340,000 km 125,000 km on the Sun.


Prominences

The SoHO EIT full sun image, taken on 14 September 1999 in the He II line at 304 Å shows the upper chromosphere/lower transition region at a temperature of about 60,000 K. The bright features are called active regions. A huge erupting prominence escaping the Sun can be seen in the upper right part of the image. Prominences are “cool” 60,000 K plasma embedded in the much hotter surrounding corona, which is typically at temperatures above 1 million K.


Filament Evolution

Temporal evolution in H center line of a sigmoidal filament in active region NOAA 8668 during August 2000.

(a) Videomagnetogram , (b) CaI line wing filtergram, (c) Ha – 0.6 Å filtergram, and (d) Ha center line filtergram.


Filament Eruption


Sympathetic Flare


Transition Region & Corona


Corona – EIT 304 Å


Corona – EIT 171 Å


Corona – LASCO C2


Corona – LASCO C3


Corona and Planets


Coronal Mass Ejection – LASCO


Coronal Mass Ejection & Comet


Coronal Mass Ejection – TRACE


Space Weather


Space Weather – Sun Earth Connection


Space Weather – Bow Shock


Space Weather Effects on Earth


Solar Cycle – Butterfly Diagram


Solar Cycle


Solar Cycle – Synoptic Map


Big Bear Solar Observatory


Telescopes and Control Room


BBSO – Instruments


Optical Lab and Parallel Computer


Homework Class Project Continue improving the PPT presentation. Use the abstract from the previous assignment

as a starting point for a PowerPoint presentation.

The PPT presentation should have between 5 and 10 slides.

Bring a print-out of the draft version to the next class as a discussion template for group work

Homework is due Wednesday November 12th, 2003 at the beginning of the lecture!

Exhibition name competition!


HomeworkHomework is due Wednesday November

12th, 2003 at the beginning of the lecture!

Homework assignment: Problems 11.1, 11.2, and 11.8!

Late homework receives only half the credit!

The homework is group homework!Homework should be handed in as a text

document!

Documents

Physics 320: Astronomy and Astrophysics – Lecture X