ASTR 1120 ASTR 1120 General Astronomy: General Astronomy: Stars - PowerPoint PPT Presentation

ASTR 1120 ASTR 1120 General Astronomy: General Astronomy: Stars & Galaxies Stars & Galaxies � NNOUNCEMENTS FIRST MIDTERM THIS THURSDAY, 09/17 THIS THURSDAY, 09/17 FIRST MIDTERM � ex � observing night Tue 09/22. � econd homework on mas � ring as � onomy due o � � UESDAY, 09/22, by 5pm.

The SUN The SUN � ast Tim � How far is the Sun? What is the Sun made of? How does the Sun produce its energy? (and how do we know?) Why is the Sun stable? What is the structure of the Sun?

Clicker Question Clicker Question In the core, what is the main wavelength wavelength In the core, what is the main of photons present? of photons present? A. Radio waves Radio waves A. B. Gamma Rays Gamma Rays B. C. Visible Visible C. D. Infrared Infrared D. E. X-rays X-rays E.

Clicker Question Clicker Question In the core, what is the main wavelength wavelength In the core, what is the main of photons present? of photons present? A. Radio waves Radio waves A. B. Gamma Rays Gamma Rays B. C. Visible Visible C. D. Infrared Infrared D. E. X-rays X-rays E.

Clicker Question Clicker Question At the photosphere, what is the main At the photosphere, what is the main wavelength of photons present? wavelength of photons present? A. Radio waves Radio waves A. B. Gamma Rays Gamma Rays B. C. Visible Visible C. D. Infrared Infrared D. E. X-rays X-rays E.

Clicker Question Clicker Question At the photosphere, what is the main At the photosphere, what is the main wavelength of photons present? wavelength of photons present? A. Radio waves Radio waves A. B. Gamma Rays Gamma Rays B. C. Visible Visible C. D. Infrared Infrared D. E. X-rays X-rays E.

How do we know what’s inside the Sun? Helioseismology: Helioseismology: Millions of sound Millions of sound waves available to probe solar interior waves available to probe solar interior Some waves bounce Some waves bounce just below the surface just below the surface Others almost make it Others almost make it to the center to the center All excited by turbulent All excited by turbulent granulation visible in granulation visible in photosphere photosphere ACOUSTIC WAVES ACOUSTIC WAVES

SOLAR SOLAR OSCILLATION OSCILLATION MODES MODES One of millions of modes, each with a different tone!

Sunspots Sunspots • Darker Darker = cooler cooler • – Still ~4,000 K • Sunspot pictured at the bottom left covers the area of 15 Earths! – Taken with the Solar and Heliospheric Observatory (SOHO)

Sunspots Caused By Magnetic Sunspots Caused By Magnetic Fields Fields • Magnetic fields entrain gas in huge bubbling loops • Cooler areas at “liftoff” cause dark sunspots

But What Causes the Magnetic But What Causes the Magnetic Field Lines to Lines to Stick Out Like That? Stick Out Like That? Field • Differential Rotation Differential Rotation • – The Sun rotates differently at different latitudes. • The Sun winds itself up

This Solar “ “Wind Up Wind Up” ” Leads Leads This Solar To The Sunspot Cycle To The Sunspot Cycle

During the Sunspot Cycle Sunspots During the Sunspot Cycle Sunspots Form At Different Latitudes Form At Different Latitudes

Complex Interplay of Convection, Magnetism and Complex Interplay of Convection, Magnetism and Differential Rotation. Differential Rotation.

Clicker Question Clicker Question What is believed to be the main cause of the What is believed to be the main cause of the sunspot cycle? sunspot cycle? A. Temperature changes between the equator and poles of the Sun B. Twisting of magnetic fields lines in the Sun due to a rotation rate varying with latitude. C. Variability in the Sun’s brightness every 11 years D. Interaction between the Sun and the orbits of the innermost planets E. A variation of the fusion rate occurring in the core of the Sun.

Clicker Question Clicker Question What is believed to be the main cause of the What is believed to be the main cause of the sunspot cycle? sunspot cycle? A. Temperature changes between the equator and poles of the Sun B. Twisting of magnetic fields lines in the Sun due to a rotation rate varying with latitude. C. Variability in the Sun’s brightness every 11 years D. Interaction between the Sun and the orbits of the innermost planets E. A variation of the fusion rate occurring in the core of the Sun.

If we see the If we see the sunspot edge-on, sunspot edge-on, it’ ’s called a s called a it PROMINENCE PROMINENCE

When Prominences Go Bad When Prominences Go Bad • Occasionally the Occasionally the • magnetic field lines magnetic field lines in a prominence in a prominence “snap snap” ” “ – Energy & Light is released • Flares Flares • – Charged particles are spewed out into space • Coronal Mass Coronal Mass • Ejections Ejections

Coronal MASS MASS Ejections Ejections Blast Blast Coronal Out Charged Particles Out Charged Particles • PROTONS! – Can: • Damage satellites • Harm astronauts • Induce currents on Earth and destroy electric transformers on the ground • Cause swelling in the Earth’s atmosphere

Coronal Mass Ejections Movie Coronal Mass Ejections Movie from from Solar and Heliospheric Heliospheric Observatory Observatory Solar and http://sohowww sohowww. .nascom nascom. .nasa nasa. .gov gov/ / http://

Protons interacting with the Protons interacting with the Earth’ ’s magnetic field produce aurora s magnetic field produce aurora Earth

Chromosphere Chromosphere • Temperature goes back UP! • T � 6,000-10,000 K 6,000-10,000 K • Very thin density Very thin density • • Heated by energy Heated by energy • twisting and spilling twisting and spilling around magnetic field around magnetic field lines lines

Outside the chromospere chromospere, the , the Outside the temperature spikes up again! temperature spikes up again!

Corona Corona • T � 1,000,000 K 1,000,000 K • Extremely thin Extremely thin • density density • X-rays X-rays • • More magnetic More magnetic • heating heating

X-ray image of the Sun X-ray image of the Sun

Solar Eclipse: Sun’ ’s light s light Solar Eclipse: Sun blocked by the Moon blocked by the Moon Corona becomes clearer in visible light without glare from the rest of the Sun

Solar Wind Solar Wind • At the top of the corona, • At the top of the corona, gas is hot enough (and gas is hot enough (and far enough) to escape far enough) to escape the gravity of the Sun the gravity of the Sun • In effect, the corona is • In effect, the corona is “evaporating evaporating” ” “ – Bu But replenished from t replenished from – below below • Solar wind carries about a million tons of solar million tons of solar matter per second!! matter per second – Yet the sun has only lost 0.1 percent of its mass!