Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20 Tom Burbine

Course Course Website: – 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 owebcthttps://spark.oit.umass.edu/webct/logonDisplay.d owebct 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: for updated information There's a map to the observatory on the website.

Final Monday - 12/14 4:00 pm Hasbrouck 20

HW #9 Due today

HW #10 Due Oct. 29

Exam #2 Average was a 75 Grades from 100s to a Average (80% exams, 20% HW) for people who took both exams is ~81

32 Extrasolar planets were just announced The new alien planets, which bring the known count beyond 400, were found with the HARPS spectrograph on the European Southern Observatory's 3.6-m telescope in La Silla, Chile. Some just five times the mass of Earth Others five times heftier than giant Jupiter _and_science-space/

Radioactive Decay

What are the assumptions to get an age?

What are the assumptions? No loss of parent atoms –Loss will increase the apparent age of the sample. No loss of daughter atoms –Loss will decrease the apparent age of the sample. No addition of daughter atoms or if daughter atoms was present when the sample formed –If there was, the age of the sample will be inflated These can possibly be all corrected for

Basic Formula Number of daughter atoms formed = number of parent atoms consumed If there were daughter atoms originally there D – D o = n o - n Remember: n = n o e -λt so n o = n e λt D- D o = n e λt – n D = D o + n (e λt – 1)

Commonly Used Long-Lived Isotopes in Geochronology Radioactive Parent (P) Radiogenic Daughter (D) Stable Reference (S) Half-life, t½ (10 9 y) Decay constant, l (y -1 ) 40K40Ar 36Ar x Rb87Sr86Sr x Sm143Nd144Nd x Th208Pb204Pb x U207Pb204Pb x U206Pb204Pb x10 -10

How do you determine isotopic values?

Mass Spectrometer

It is easier To determine ratios of isotopic values than actual abundances

Example 87 Rb  87 Sr + electron + antineutrino + energy Half-life is 48.8 billion years 87 Sr = 87 Sr initial + 87 Rb (e λt – 1) Divide by stable isotope 87 Sr = 87 Sr initial + 87 Rb (e λt – 1) 86 Sr 86 Sr 86 Sr

Example Formula for line 87 Sr = 87 Sr initial + (e λt – 1) 87 Rb 86 Sr 86 Sr 86 Sr y = b + m x

= (e λt – 1)

Carbon-14 99% of the carbon is Carbon-12 1% is Carbon % is Carbon-14 The half-life of carbon-14 is 5730±40 years. It decays into nitrogen-14 through beta-decay (electron and an anti-neutrino are emitted).

Due to Carbon-14’s short half-life, can only date objects up to 60,000 years old

Plants take up atmospheric carbon through photosynthesis

When something dies, it stops being equilibrium with the atmosphere

Why is Carbon-14 still present if it has such a short half-life?

Cosmic rays impact Nitrogen-14 and create Carbon-14 Cosmic rays are energetic particles (90% are protons) originating from space. From the Sun (solar cosmic rays) or outside the solar system (galactic cosmic rays) n + 14 N → 14 C + p

bomb_spike.svghttp://en.wikipedia.org/wiki/Image:Radiocarbon_ bomb_spike.svg

Composition of the Planets

Different bodies have different densities Density = Mass/Volume M = 4  2 d 3 /GP 2 V =4/3  R 3

Life of a Star A star-forming cloud is called a molecular cloud because low temperatures allow Hydrogen to form Hydrogen molecules (H 2 ) Temperatures like K

Region is approximately 50 light years across

Condensing Interstellar clouds tends to be lumpy These lumps tend to condense into stars That is why stars tend to be found in clusters

Protostar The dense cloud fragment gets hotter as it contracts The cloud becomes denser and radiation cannot escape The thermal pressure and gas temperature start to rise and rise The dense cloud fragment becomes a protostar

When does a protostar become a star When the core temperatures reaches 10 million K, hydrogen fusion can start occurring

Formation of Solar System Solar Nebula Theory (18 th century) – Solar System originated from a rotating, disk-shaped cloud of gas and dust Modern theory is that the Solar System was born from an interstellar cloud (an enormous rotating cloud of gas and dust)

Composition ~71% is Hydrogen ~27% is Helium ~2% are other elements (Fe, Si, O) in the form of interstellar grains

Show animation

Dust grains collide and stick to form larger and larger bodies. When the bodies reach sizes of approximately one kilometer, then they can attract each other directly through their mutual gravity, becoming protoplanets Protoplanets collide to form planets –Asteroids such as Ceres and Pallas are thought to be leftover protoplanets

Condensation – conversion of free gas atoms or molecules into a liquid or solid Volatile – Elements or compounds that vaporize at low temperatures

Show animation

Form atmosphere and oceans Show animation

Any Questions?