Important years for astronomy
Example problem:Halley’s comet has an orbital period of 76 years and itsfurthest distance from the Sun is 35.3 AU.•How close does Halley’s comet come to the Sun?P2 = a3•How does this compare to the Earths distance from theSun?•What is its eccentricity?
Halley’s comet has an orbital period of 76 years and itsfurthest distance from the Sun is 35.3 AU.•How close does Halley’s comet come to the Sun?P2a3P2perihelion2aphelion3perihelionaphelion2P3 2perihelion2P3 2aphelionperihelionperihelion2763 235.335.8 35.3 0.5AU•How does this compare to the Earths distance from theSun?The average Earth - Sun distance is 1AU .. So the Comet crosses our orbit!•What is its eccentricity?.eeaphelion34.835.820.97periheliona
ProblemAn asteroids closest approach to the Sun(perihelion) is 2 AU, and farthest distance from the Sun(aphelion) is 4 AU.•What is the semi major axis of its orbit?•What is the period of its orbit?•What is it’s eccentricity?
A Universe of Matter and Energy“The eternal mystery of the world is itscomprehensibility. The fact that it iscomprehensible is a miracle.”Albert Einstein (1879 – 1955)Physicist
What are Matter and Energy?matter – is material such as rocks, water, air.energy – is what makes matter move!Energy is measured in many different units.The metric unit of energy used by scientists is:JouleEnergy (Joules)4,184 Joules = 1 kilocalorie= 1 “food” calorie
•kineticThree Basic Types of Energy– energy of motion•potential– stored energy•radiative– energy transported by lightEnergy can change fromone form to another.
Potential Energy getsconverted to Kinetic
Kinetic Energy•Amount of kinetic energy of a moving object=1/2 mv2[if mass (m) is in kg & velocity (v) is in m/s, energy is inJoules]•On the microscopic level– the average kinetic energy of the particles within asubstance is called the temperature.– it is dominated by the velocities of the particles.