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 FIRST MIDTERM THIS THURSDAY, 09/17 THIS THURSDAY, 09/17

ex observing night Tue 09/22. econd homework on masring asonomy 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?

In the core, what is the main In the core, what is the main wavelength wavelength

• f photons present?
• f photons present?

A.

• A. Radio waves

Radio waves B.

• B. Gamma Rays

Gamma Rays C.

• C. Visible

Visible D.

• D. Infrared

Infrared E.

• E. X-rays

X-rays Clicker Question Clicker Question

In the core, what is the main In the core, what is the main wavelength wavelength

• f photons present?
• f photons present?

A.

• A. Radio waves

Radio waves B.

• B. Gamma Rays

Gamma Rays C.

• C. Visible

Visible D.

• D. Infrared

Infrared E.

• E. X-rays

X-rays 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.

• A. Radio waves

Radio waves B.

• B. Gamma Rays

Gamma Rays C.

• C. Visible

Visible D.

• D. Infrared

Infrared E.

• E. X-rays

X-rays 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.

• A. Radio waves

Radio waves B.

• B. Gamma Rays

Gamma Rays C.

• C. Visible

Visible D.

• D. Infrared

Infrared E.

• E. X-rays

X-rays Clicker Question Clicker Question

Helioseismology: Helioseismology: Millions of sound

Millions of sound waves available to probe solar interior waves available to probe solar interior

ACOUSTIC WAVES ACOUSTIC WAVES

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

How do we know what’s inside the Sun?

SOLAR SOLAR OSCILLATION OSCILLATION MODES MODES

One of millions

• f 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 Field Lines to Lines to Stick Out Like That? Stick Out Like That?

• Differential Rotation

Differential Rotation

– The Sun rotates differently at different latitudes.

• The Sun winds itself up

This Solar This Solar “ “Wind Up Wind Up” ” Leads Leads 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.

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.

Clicker Question Clicker Question

If we see the If we see the sunspot edge-on, sunspot edge-on, it it’ ’s called a s called a 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 Coronal MASS MASS Ejections Ejections Blast Blast 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 Solar and Heliospheric Heliospheric Observatory Observatory

http:// http://sohowww sohowww. .nascom nascom. .nasa nasa. .gov gov/ /

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

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 Outside the chromospere chromospere, the , 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 Solar Eclipse: Sun’ ’s light s light 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!