Doppler Shift

Extra-solar Planets

Planet in Circular Orbit

51 Pegasi, Msin(i)=0.45, a=0.05AU, e = 0.014, d=50ly

A highly eccentric planet.

16 Cygni B: Msin(i)=1.5 MJ, a=1.7 AU, e=0.67, d=70ly

Multiple planet system

47 Usula Majoris: Planet 1: Msin(i)=2.5MJ, a=2.1AU,e=0.06, d=43ly

Planet 2: Msin(i)=0.8MJ, a=3.7AU,e=0.1

• Many extra-solar planets contain highly eccentric orbits

• Many extra-solar planets lie close to their Sun.

• Why is that? Is our Solar System exceptional? Or did many of the extra-solar planets form in a different way?

Extra-solar Planets – Their Orbital Characteristics

Summary• Changing electric fields produce changing magnetic fields,

which produce changing electric fields, which propagate as waves.

• These waves are called EM waves. • EM waves behave as particles & as waves• They are characterized by their wavelength.• The energy of light particles depends on the frequency:

E = hv• Light experiences scattering, refraction and absorption by

matter.• Light from a moving object is doppler shifted along the

direction of travel.• Light travels at 2.99x108 m/s in a vacuum.

The emission of EM radiation from objects: 2 results from Quantum

Mechanics

This topic is called black body radiation in quantum mechanics

All objects emit.

Wien’s Law*:The wavelength of the radiation depends on the body’s temperature.

L(m) = 0.003 / T(K)

L = wavelength of peak radiation

T = Temperature of the object

This is a result from Quantum Mechanics.

The Sun emits visible light.

Emission of the Sun.

The Sun’s surface temperature is 6000K. Thus it emits radiation at a wavelength of

(0.003 / 6000 ) meters

That is 0.5x10-6 m,

i.e. visible wavelengths

Earth emits IR radiation

Earth’s temperature is 300K, and thus radiates at a peak wavelength of:

L = (0.003 / 310)

L = 10x10-6 m

The hotter the more powerful

The power emitted from an object per unit area is:

P = sigma x T4

where sigma = 5.67 x 10-8 W/m2 K4

Another result from Quantum Mechanics.

Why do coals glow when they are hot?

And not when they are not hot?

The Greenhouse Effect

I thank you God for this most amazing day, for the leaping greenly spirits of

trees, and for the blue dream of sky and for everything which is natural, which is

infinite, which is yes.

- e.e. cummings

Our see-through atmosphere

• Our atmosphere is transparent to visible light.

• Sunlight reaches Earth’s surface with only some obstruction from clouds and dust.

• Sunlight is absorbed by the surface, which it heats thereby.

IR radiation & Earth’s atmosphere

• The Earth’s surface absorbs the sunlight and re-radiates the energy as infra-red radiation.

• Some of the gases in our atmosphere absorb IR radiation.

• Examples of such greenhouse gases are CO2, H2O, CH4, CO.

• Radiation emitted by Earth does not entirely escape to space, much of it is instead absorbed and re-radiated back to the surface.

The Greenhouse Effect

• Some of the re-radiated radiation goes up, and some goes down.

• This secondary radiation is absorbed and heats the atmosphere.

Heating Earth

• The more effective our atmosphere is at absorbing IR radiation, the hotter it will become.

• The addition of greenhouse gases renders Earth more absorbing to IR radiation.

• Gases such as CO2, H2O, CH4, CO cause the Earth to warm up.

Evidence that Earth is warming

Reconstruction of the Northern Hemisphere temperatures coral and ice-core proxy records (Mann et al. 1999, 1998, Jones & Briff 1992

The increase in CO2

Rising Ocean temperaturesThe Atlantic, Pacific and Indian oceans have warmed by 0.06 C in since 1955 (Science, 24 March 2000, pg 2225). This result was determined by compiling millions of measurements of the deep oceans made from 1948 to 1995. More recently (Science, 13 April 2001), climate calculations indicate that the anthropogenic rise in CO2 explains this sea warming.

Coral reefs are dying all around the world, likely as a result of the warming of the oceans.

Melting Polar Ice

The northeast passage is predicted to open up in 2050, allowing ships to sail from London to Japan along the coast of Siberia.

Wildlife is expected to suffer heavily from the loss of the ice sheet. Present research suggests that bears are having a harder time hunting seals.

Sea levels are rising

Present predictions based on glacial melt rates indicate that the sea level will rise 10-20 inches in the next century.

Runaway Effects

Note: • If we heat the Earth with greenhouse gases,

more water will evaporate.• Water, a strong greenhouse gas, will further

heat the Earth.• More water will evaporate• More heating will occur• More water will evaporate• And so on.

The presence of clouds, which reflect sunlight and therefore cool the planet add to the uncertainties in the ability for climate models to predict the future climate of Earth.

Yet these uncertainties are not insurmountable in the sense that we can predict the evolution of Earth for various educated assumptions regarding clouds.

Runaway Greenhouse

Summary

• Earth has warmed 1F in the last century

• The CO2 abundance has risen by 20% since 1950.

• The oceans have warmed 0.06 C since 1955.

• The sea level is rising 0.1 inches each year.

Kyoto Protocol

• In 1997 the Kyoto Protocol was formulated.• The treaty calls for the 38 largest industrial nations to

reduce emissions due to greenhouse gases.• But the Protocol would not take effect until it is ratified by

the nations emitting at least 55 percent of the greenhouse gases.

• In March of 2001, the USA rejected the Protocol on the grounds that it would hurt the economy.

• The USA, with 4% of the world population, produces 25% of the greenhouse gases. The protocol would require the USA to reduce the emissions by 7% by 2010.

• In June 2002, the European Union and many other countries, including Japan, proceeded to ratify the Protocol, without the USA. The union of countries produce almost 55% of the greenhouse gases.

Kyoto Protocol

Kyoto Protocol

The European Union's ratification of the Kyoto Protocol is a clear

indication that, with enough political will and collective social effort, the challenges of our time,

complex though they may be, can be addressed successfully through ... cooperation.

-- Environment Commissioner to the EU, Margot Wallstrom