The origin of the solar system Credit: ESO/NASA/ESA/Ardila et al. The origin of the solar system HW 11 being passed out today. Be sure to hand in 10 to Steven in back of room if haven’t already (extension). (btw I stole “Origins” from X-Men: Origins, Wolverine.) HW11 is not only 1 point each this time (but don’t worry, still easy compared to 1st half of semester) – ignore directions at bottom, forgot to fix. Mention planet/plant common typo joke. Szydagis 04.22.2015 This artist’s impression shows the formation of a gas giant planet in the ring of dust around the young star HD 100546. This system is also suspected to contain another large planet orbiting closer to the star. The newly-discovered object lies about 70 times further from its star than the Earth does from the Sun. This protoplanet is surrounded by a thick cloud of material so that, seen from this position, its star almost invisible and red in color because of the scattering of light from the dust. Credit: ESO/L. Calçada

Proplyds in the Orion Nebula Even so (on last point) we also know of THOUSANDS of exoplanets now. NASA/ESA Hubble Space Telescope, 2009 Protoplanetary disks or proplyds are everywhere all around us, actually being more common than even the most hard-core science fiction fan would have ever dreamt, not in their wildest dreams This implies that planets themselves, which are much more difficult to spot than these showy disks, are extremely common as well, including earth-like ones too probably, but due to size even more difficult to spot

We think that this is how our very own solar system most likely looked, ~4.6 billion years ago A common theme: remember spiral/lenticular galaxies, and bottom-up galaxy formation model In the modern default model, young stars (protostars) are the ones that form planets, so they come early on When dating our own solar system at the very least, this is definitely true (Sun, Earth, other planets, all the same age roughly, to within few millions of years: that’s “nothing”) Can also see in observation of stellar planetary systems forming right now as speak… A Closer-Up Look Protoplanetary disc around HL Tauri* See, this is why planets all in 1 plane (think bulging/flattening of rotating objects again). Age from ratios of radioactive elements (explain beauty of not needing to know total original amounts, and about cross-checks with multiple different elements). Mention stellar vs. solar. ALMA (ESO/NAOJ/NRAO) * Remember “T Tauri” protostars?

Accretion Model, and Gas Collapse Model: 2 different ways of viewing possible planetary system formations Either way, all planets start out their lives as just clouds of gas (just as the stars do) Some become gas giants, remaining all gas or nearly so, like the 4 we have in our own system: Jupiter, et al. Others, depending on the exact temperatures and pressure conditions, and the exact details and degree of the collapse, can become (small) rocky worlds (solid – liquid is a bit trickier) Accretion disks: black holes! More and more inter-connections amongst everything that we have learned. On gas giants: become vs. remain (size – why gas giants big?) By liquid, I don’t mean all liquid, although there are some exoplanets which we think have all-ocean (H2O) surfaces potentially (how do we know that? Ask Kev K. next week!) Credit: NASA/ESA and A. Feild (STScI)

Speaking of Liquid…

More Reasons Why Disks Why a disk? The reason is same as reason that Saturn's rings form a disk Particles which are NOT in regular, circular, equatorial orbits will collide and will either break up or be forced to conform to a regular orbit Collision processes can act both to confine material to a thin disk (what we now call the ecliptic) as well as cause the orbits of the surviving objects to be regular circles/ellipses that are spaced apart, so that there are no further collisions (major, often) Note all planets orbit the Sun in same direction, the direction Sun rotates! Recall the scientific method, of theories in cycles. Is this a perfect explanation? No, but nothing ever is. http://lasp.colorado.edu/~bagenal/1010/SESSIONS/11.Formation.html

Activity: Making Connections What concepts that you might have originally thought were quite disparate turned out to be similar in nature after you learned more, upon taking this course Examples from today were: solar and black hole accretion, and gravitational self-attraction and spherical collapse of gas clouds in general (protostar, protoplanet, protogalaxy, all starting out many times larger…) This should help you review for the 05.13 final exam, by finding what is the same from across entire semester Please use something other than the examples which I have provided above if possible, and doesn’t have to be stuff you knew partially before, but new connections ----- Meeting Notes (4/22/15 12:27) ----- Kyle, Neal, Shin, Mohammad, Nick

Individual Planets A & S article: magnetism plays role too, not just gravity Helps address question of how the clumpiness randomly started on its own Remember how electricity and magnetism MUCH stronger than gravity, which compensates: BIG things Just like sun and stars, a planet can have rich internal structures concentrically Crust, mantle, cores: not just earthly concepts! On last point, give brick and moon analogy about heavenly and earthly matter, recalling Aristotle. Mention inner, outer cores (arbitrary?) http://lasp.colorado.edu/~bagenal/1010/SESSIONS/11.Formation.html

(We are Not Only Game in Town Anymore) This lecture already looks a heck of a lot different than a same one would have even just 10-20 years ago (new!) Note guest lecture from Kevin Knuth coming next week devoted entirely to just this topic (exoplanets.) (NOT an excuse to skip class: you will be tested on the material. Unlike with Oleg, I will be here too. This is occurring just for fun this time around, and not because I am gone.) Credit: NASA/Ames/JPL-Caltech.

Something fun: back to the kitchen cosmos from NPR

Homework New written one (#11) is (still) due on Monday “Reading”: for this Friday, research the planets. Just Google them -- studying them, looking up some facts Group activity will be: report on one of 7 (not Earth) Need to start thinking seriously about how and when you will study for the final, coming up very fast Speaking of googling, please refrain from it in class, though. Also, on planets, not Pluto; I’d like to even though already did discuss it, but we won’t have enough groups.