Unit 2Unit 2The Earth in SpaceThe Earth in Space

The Solar SystemThe Solar System

Origin of Our Solar SystemOrigin of Our Solar SystemToday, most astronomers believe our solar Today, most astronomers believe our solar system is a by-product of the origin of the system is a by-product of the origin of the sun.sun.

The most accepted explanation is the The most accepted explanation is the Nebular HypothesisNebular Hypothesis Immanuel Kant, a German philosopher first Immanuel Kant, a German philosopher first

proposed in 1755proposed in 1755

Terms Related to the HypothesisTerms Related to the Hypothesis

Nebula which is an immense cloud of gas Nebula which is an immense cloud of gas and dust particlesand dust particles

Planetesimals which are small rocky Planetesimals which are small rocky objects that rotate around a starobjects that rotate around a star

Accretion is the process of growth by Accretion is the process of growth by accumulationaccumulation

Protosun was the predecessor of the SunProtosun was the predecessor of the Sun

Nebular HypothesisNebular Hypothesis5 billion years ago 5 billion years ago The solar system was believed to have consisted of a The solar system was believed to have consisted of a

nebulanebula This nebula was slowly rotating and due to some unknown This nebula was slowly rotating and due to some unknown

cause, it began to contract under its own gravitational pull.cause, it began to contract under its own gravitational pull. The largest mass accumulated in the center, attracting The largest mass accumulated in the center, attracting

more dust particles and gas. The areas left behind more dust particles and gas. The areas left behind formed a series of whirlpoolsformed a series of whirlpools

The center area grew smaller (matter packed in) and the The center area grew smaller (matter packed in) and the spinning increased.spinning increased.

Example: Think of a figure skater who pulls their arms into a spin. Example: Think of a figure skater who pulls their arms into a spin. What happens when they extend their arms? What happens when they extend their arms?

The result: The cloud was flattened into a disk-like shapeThe result: The cloud was flattened into a disk-like shape

The collapsing, spinning nebula begins to flatten into a rotating pancake

Nebular Hypothesis cont’dNebular Hypothesis cont’d100 million years later100 million years later Majority of mass accumulated in centerMajority of mass accumulated in center In the whirlpools areas, planetesimals were forming In the whirlpools areas, planetesimals were forming

through the process of accretion. As dust and gas through the process of accretion. As dust and gas were pulled inward, these planetesimals grew in were pulled inward, these planetesimals grew in size increasing in gravitational pull.size increasing in gravitational pull.

This pull was strong enough to hold lighter gases like This pull was strong enough to hold lighter gases like hydrogen and heliumhydrogen and helium

This process took about 10 to 30 million years to form the This process took about 10 to 30 million years to form the present size of today’s planets present size of today’s planets

Nebular Hypothesis cont’dNebular Hypothesis cont’dThe pressure of the center mass increased to such The pressure of the center mass increased to such levels that the inner temperature of the levels that the inner temperature of the PROTOSUNPROTOSUN reached 11 million reached 11 million ooCC

Result: Result: Thermonuclear explosion which was the lighting of the Thermonuclear explosion which was the lighting of the

Sun’s inner coreSun’s inner core T. Tauri Wind, a solar wind of charged particlesT. Tauri Wind, a solar wind of charged particles

Traveled at speeds of 3.3 million km/h throughout the solar system Traveled at speeds of 3.3 million km/h throughout the solar system for 9 million yearsfor 9 million years

Swept away all gas and dust particles between the planets Swept away all gas and dust particles between the planets

Stripped the inner planets of their first atmosphereStripped the inner planets of their first atmosphere

The outer planets held their helium and hydrogen atmospheresThe outer planets held their helium and hydrogen atmospheres

Nebular Hypothesis cont’dNebular Hypothesis cont’dIn the last 4.5 billion yearsIn the last 4.5 billion years The planetesimals continued to collide with other planets The planetesimals continued to collide with other planets

and moons adding to their massesand moons adding to their masses It’s important to recognize that only the largest of these It’s important to recognize that only the largest of these

planetesimals could survive the high-energy collisions planetesimals could survive the high-energy collisions from meteorites (lower mass planetesimals)from meteorites (lower mass planetesimals)

These traveled at 30,000 to 75, 000 km/hThese traveled at 30,000 to 75, 000 km/h Asteroids are considered to be left-over planetesimalsAsteroids are considered to be left-over planetesimals Why didn’t these asteroids make up a planet?Why didn’t these asteroids make up a planet?

The Asteroid Belt between Mars and Jupiter is thought The Asteroid Belt between Mars and Jupiter is thought to be remnants of material that made up the solar to be remnants of material that made up the solar system. It’s placement is such that there is competing system. It’s placement is such that there is competing pull between Jupiter and the Sunpull between Jupiter and the Sun

Nebular Hypothesis: Nebular Hypothesis: Explains Major Features of Solar SystemExplains Major Features of Solar System

1.1. Explains regular motions of the planets and moonsExplains regular motions of the planets and moons• All revolve in the nearly the All revolve in the nearly the same planesame plane, in , in nearly circular nearly circular

orbitsorbits, and , and nearly all rotate in the nearly same directionnearly all rotate in the nearly same direction as the as the Sun too Sun too

2.2. Explains all major differences between terrestrial and Explains all major differences between terrestrial and gaseous (jovian) planetsgaseous (jovian) planets

• Mass, distance from Sun, composition, moon and ring Mass, distance from Sun, composition, moon and ring systems systems

3.3. Explains small bodies Explains small bodies • Asteroids and comets, both short- and long-period Asteroids and comets, both short- and long-period

4.4. Explains exceptions to the trendsExplains exceptions to the trends • Terrestrial moons, axial tilts, non-coplanar jovian moons, Terrestrial moons, axial tilts, non-coplanar jovian moons,

TritonTriton

Nebular Hypothesis: Nebular Hypothesis: Current Challenges to the Nebular HypothesisCurrent Challenges to the Nebular Hypothesis

1.1. Missing mass in Kuiper BeltMissing mass in Kuiper Belt• Icy bodies found beyond orbit of NeptuneIcy bodies found beyond orbit of Neptune

2.2. Capture process for TritonCapture process for Triton• Largest moon of Neptune orbits in opposite Largest moon of Neptune orbits in opposite

directiondirection

3.3. Sideways rotation of UranusSideways rotation of Uranus4.4. Discovered “hot Jupiter” exoplanetsDiscovered “hot Jupiter” exoplanets

• These planets are much closer to their parent star These planets are much closer to their parent star then our own Jupiterthen our own Jupiter

5.5. Discovered exoplanets in binary and trinary Discovered exoplanets in binary and trinary stellar systemsstellar systems

• Planets with two / three parent starsPlanets with two / three parent stars

Kuiper BeltKuiper Belt

Difficult to ProveDifficult to ProveIt’s important to remember that this hypothesis is It’s important to remember that this hypothesis is the best explanation to date for the formation of the best explanation to date for the formation of a solar system.a solar system. It is not yet possible to observe the formation of the It is not yet possible to observe the formation of the

other stars to verify the steps outlined (Think other stars to verify the steps outlined (Think distance)distance)

No one was around for the first oneNo one was around for the first one

It is believed that if this hypothesis is true that all It is believed that if this hypothesis is true that all solar systems would form the same way – use solar systems would form the same way – use the same patternthe same pattern

Ways of proving this is through technologyWays of proving this is through technology

Nebular HypothesisNebular Hypothesis

http://www.youtube.com/watch?http://www.youtube.com/watch?v=PL3YNQK960Yv=PL3YNQK960Y

InstrumentationInstrumentationExpanding our Knowledge of the Solar SystemExpanding our Knowledge of the Solar System

To improve our understanding of the Solar To improve our understanding of the Solar System technological developments System technological developments include:include: 1919thth Century Century

Optical telescopesOptical telescopes 2020thth Century Century

Radio telescopesRadio telescopes

RocketryRocketry

TelescopesTelescopes HubbleHubble

TechnologyTechnology(4 minutes)(4 minutes)

Videos\Videos\Space_Travel__The_International_SpaceSpace_Travel__The_International_Space_Station.asf_Station.asf

Hubble Space TelescopeHubble Space Telescope(2 minutes)(2 minutes)

Videos\Videos\Understanding_the_Universe__The_HubblUnderstanding_the_Universe__The_Hubble_Space_Telescope.asfe_Space_Telescope.asf

The HST must be able to talk with controllers The HST must be able to talk with controllers on the ground to relay data from its on the ground to relay data from its observations and receive commands for its next observations and receive commands for its next targets. targets. To communicate, the HST uses a series of To communicate, the HST uses a series of relay satellites called the relay satellites called the Tracking and Data Tracking and Data Relay Satellite System (TDRSS)Relay Satellite System (TDRSS), which is the , which is the same system used by the International Space same system used by the International Space Station. Station.

Hubble Space Telescope (HST)Hubble Space Telescope (HST)

Photo courtesy NASA / STScICommunications system used by the Hubble Space Telescope.

Hubble Space Hubble Space TelescopeTelescope

Sequence of Events: Sequence of Events: Incoming light from an object gets received by the HST (2) and converted to Incoming light from an object gets received by the HST (2) and converted to digital data. The data is then sent to the TDRSS in orbit (3), which then digital data. The data is then sent to the TDRSS in orbit (3), which then transmits it to the Ground Receiving Station at White Sands, N.M. (4). The transmits it to the Ground Receiving Station at White Sands, N.M. (4). The White Sands Facility transmits the data to NASA's Goddard Spaceflight White Sands Facility transmits the data to NASA's Goddard Spaceflight Control Center (5), where HST operations are centered. The data are then Control Center (5), where HST operations are centered. The data are then analyzed by scientists at the nearby Space Telescope Science Institute in analyzed by scientists at the nearby Space Telescope Science Institute in Baltimore, MD. (6). Most of the time, commands are relayed to the HST in Baltimore, MD. (6). Most of the time, commands are relayed to the HST in advance of a planned observing run; however, real-time commands are advance of a planned observing run; however, real-time commands are possible when necessary.possible when necessary.

Recent Hubble Space Telescope observations shed Recent Hubble Space Telescope observations shed considerable light on the birth of stars and associated considerable light on the birth of stars and associated

planetary systems. planetary systems.

Regions in the Orion Regions in the Orion Nebula where solar Nebula where solar systems appear to be systems appear to be formingforming

1500 light years from 1500 light years from EarthEarth

Middle star in the Middle star in the sword of the sword of the constellation Orionconstellation Orion

This image shows This image shows several protoplanetary several protoplanetary disks.disks.

Think AboutThink About

Voyager 2 SatelliteVoyager 2 Satellite Gone 12 yearsGone 12 years Jupiter, Saturn, Uranus, NeptuneJupiter, Saturn, Uranus, Neptune Information doubled what was known about Information doubled what was known about

the solar systemthe solar system ProblemProblem

It will take decades to get through all the It will take decades to get through all the informationinformation