Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20 Tom Burbine email@example.com. Course. Course Website: http://blogs.umass.edu/astron101-tburbine/ Textbook: Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny .
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Astronomy 101The Solar SystemTuesday, Thursday2:30-3:45 pmHasbrouck 20Tom Burbinetomburbine@astro.umass.edu
Course • Course Website: • http://blogs.umass.edu/astron101-tburbine/ • Textbook: • Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny. • You also will need a calculator.
Office Hours • Mine • Tuesday, Thursday - 1:15-2:15pm • Lederle Graduate Research Tower C 632 • Neil • Tuesday, Thursday - 11 am-noon • Lederle Graduate Research Tower B 619-O
Homework • We will use Spark • https://spark.oit.umass.edu/webct/logonDisplay.dowebct • Homework will be due approximately twice a week
Astronomy Information • Astronomy Help Desk • Mon-Thurs 7-9pm • Hasbrouck 205 • The Observatory should be open on clear Thursdays • Students should check the observatory website at: http://www.astro.umass.edu/~orchardhill for updated information • There's a map to the observatory on the website.
Final • Monday - 12/14 • 4:00 pm • Hasbrouck 20
HW #10 • Due today
HW #11 • Next Tuesday
If you want to find life outside our solar system • You need to find planets • http://exoplanet.eu
Extrasolar Planets • Today, there are over 400 known extrasolar planets
Star Names • A few hundred have names from ancient times • Betelgeuse, Algol, etc. • Another system: • A star gets name depending on what constellation it is in • With a Greek letter at the beginning • Alpha Andromeda, Beta Andromeda, etc. • Only works for 24 brightest star
Star Names now • Stars are usually named after the catalog they were first listed in • HD209458 is listed in the Henry Draper (HD) Catalog and is number 209458 • HD209458a is the star • HD209458b is the first objects discovered orbiting the star
Our Solar System has basically two types of planets • Small terrestrial planets – Made of Oxygen, Silicon, etc. • Large gaseous giants – Made primarily of hydrogen and a little helium • Jupiter - 90% Hydrogen, 10% Helium • Saturn – 96% Hydrogen, 3% Helium • Uranus – 83% Hydrogen, 15% Helium • Neptune – 80% Hydrogen, 20% Helium
Things to Remember • The Milky Way has at least 200 billion other stars and maybe as many as 400 billion stars • Jupiter’s mass is 318 times than the mass of the Earth
Question: • How many of these stars have planets?
What is the problem when looking for planets? • The stars they orbit are much, much brighter than the planets
Infrared image of the star GQ Lupi (A) orbited by a planet (b) at a distance of approximately 20 times the distance between Jupiter and our Sun. • GQ Lupi is 400 light years from our Solar System and the star itself has approximately 70% of our Sun's mass. • Planet is estimated to be between 1 and 42 times the mass of Jupiter. • http://en.wikipedia.org/wiki/Image:GQ_Lupi.jpg
So what characteristics of the planets may allow you to “see” the planet
So what characteristics of the planets may allow you to “see” the planet • Planets have mass • Planets have a diameter • Planets orbit the star
Jupiter • H, He • 5.2 AU from Sun • Cloud top temperatures of ~130 K • Density of 1.33 g/cm3 • Hot Jupiters • H, He • As close as 0.03 AU to a star • Cloud top temperatures of ~1,300 K • Radius up to 1.3 Jupiter radii • Mass from 0.2 to 2 Jupiter masses • Average density as low as 0.3 g/cm3
10 100 1,000 (lightyears)
Some Possible Ways to detect Planets • Pulsar Timing • Radial Velocity (Doppler Method) • Transit Method • Direct Observation
Pulsars • Rotating Neutron Stars • Have densities of 8×1013 to 2×1015 g/cm³
Center of Mass • Distance from center of first body = distance between the bodies*[m2/(m1+m2)] • http://en.wikipedia.org/wiki/Doppler_spectroscopy
Radial Velocity (Doppler Method) http://www.psi.edu/~esquerdo/asp/shifts.jpg
Bias • Why will the Doppler method will preferentially discover large planets close to the Star?
Bias • Why will the Doppler method will preferentially discover large planets close to the Star? • The gravitational force will be higher • Larger Doppler Shift
Transit Method • When one celestial body appears to move across the face of another celestial body
When the planet crosses the star's disk, the visual brightness of the star drops a small amount • The amount the star dims depends on its size and the size of the planet. • For example, in the case of HD 209458, the star dims 1.7%. • http://en.wikipedia.org/wiki/Extrasolar_planets#Transit_method
One major problem • Orbit has to be edge on
Eclipse • Planet passes in back of a star • http://www.news.cornell.edu/stories/March05/Planet-eclipse-Plot.mov • Because the star is so much brighter than a planet, the dip in brightness is smaller during an eclipse than a transit • Usually to maximize the effects of an eclipse, astronomers observe these eclipses at infrared wavelengths
Direct Observation • Infrared Image
http://www.news.cornell.edu/stories/March05/extrasolar.ws.htmlhttp://www.news.cornell.edu/stories/March05/extrasolar.ws.html • http://nai.nasa.gov/library/images/news_articles/319_1.jpg Visible Infrared
How did these Hot Jupiters get orbits so close to their stars? • Formed there – but most scientists feel that Jovian planets formed far from farther out • Migrated there - planet interacts with a disk of gas or planetesimals, gravitational forces cause the planet to spiral inward • Flung there – gravitational interactions between large planets
Kepler Mission • Kepler Mission is a NASA space telescope designed to discover Earth-like planets orbiting other stars. • Using a space photometer, it will observe the brightness of over 100,000 stars over 3.5 years to detect periodic transits of a star by its planets (the transit method of detecting planets) as it orbits our Sun. • Launched March 6, 2009
Kepler Mission http://en.wikipedia.org/wiki/File:Keplerpacecraft.019e.jpg