Chapter 4: Formation of the Solar System AND Chapter 5: Exoplanets (Lecture Notes)

Exo-Planets and Other Planetary Systems: On average, how many of the stars in the night sky contain planets orbiting around them?

"On average, all of them (1 per star)" -Sara Seager, MIT [There could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of Sun-like stars just within the Milky Way Galaxy]

refer to background on pluto >>>

"We used to think of Pluto a remote frigid rock, but since the New Horizons visit, it's vying for the title of the solar system's most interesting (ex-) planet. An earlier study showed that its core is warm enough to support a liquid water ocean, and now we've learned that it might be huge -- at least 100km deep." - New Horizons

Habitable Zone - Liquid Water: 273< T <373K (or 0°C< T <100°C)

(pic of orbital difference vs planet temp & labeled habitable zone - liquid water)

refer to info on Asteroid 2012 DA14 >>>

45 meters across (nearly 150 feet across), with an estimated mass of about 130,000 metric tons. It approached to within 17,200 miles of Earth. If it were to hit the Earth, it would produce the equivalent of 2.4 megatons of TNT. It would not destroy Earth, but it could flatten a city. (Tanguska, 1909). vaporized itself, exploded itself in the air - thought to be a lot smaller than originally thought

How many planets do we have?

8 planets, no longer have Pluto

refer to why Pluto is not a full planet >>>

A dwarf planet (Pluto!) fulfills conditions (1) and (2), but not (3) of the classification of a planet!

refer to pic of planets in our solar system drawn to scale >>>

A montage of the planets in our solar system presented in correct relative sizes. The orbits in the background are also drawn to scale.

Explain how the Crab Nebula was created.

A supernova is the most powerful known mechanism for a star to shed mass.

Explain how the Dumbbell Nebula was created.

After the death of a star, strong stellar winds are expelling large quantities of gas and dust, creating this nebula. The scattering of starlight off this material makes it appear especially bright.

what does the kuiper belt consist of?

It consists mainly of small bodies that are remnants from the Solar System's formation. Although some asteroids are composed primarily of rock and metal, most Kuiper belt objects are composed largely of icy objects.

why didn't a planet form between Mars & Jupiter in the asteroid belt?

Jupiter's gravitational influence kept disturbing the motions of the planetesimals, breaking them up, and ejecting some from the solar system, or toward the Sun.

what are the jovian planets?

Jupiter, Saturn, Uranus and Neptune

What are trans-Neptunian objects? what does this mean?

KBOs (Kuiper belt objects) and Oort cloud objects; they orbit farther from the Sun than the outermost planet Neptune.

what are the terrestrial planets?

Mercury, Venus, Earth and Mars

How are Gas Nebulae created in general?

Older stars explode and eject the material into space

How far does the oort cloud extend? the kuiper belt?

Oort Cloud -- Extends out to 50,000AU Kuiper Belt - Just Beyond Neptune ~ 50-100AU

What are the two different types of planets? key characteristic for each?

Terrestrial planets are Rocky Jovian planets are Gaseous

what is the kuiper belt?

The Kuiper belt is a region just beyond the planets, extending from the orbit of Neptune at 30AU to approximately 50AU from the Sun.

which dwarf planets are located in the kuiper belt?

The Kuiper belt is home to at least three dwarf planets: Pluto, Haumea, and Makemake.

Formation of the Solar System: The four inner planets formed through....

The four inner planets formed through the collisions of Moon-sized bodies, probably after the outer four planets were formed. The terrestrial planets are relatively small, have high average densities, and are composed primarily of rock and metal.

how long is the frost line?

The frost line of the Solar System is around 5 AU from the Sun This distance is between Mars and Jupiter

what does the "frost line" refer to?

The frost line refers to a particular distance from the central protosun where it is cold enough for gaseous hydrogen compounds to freeze into solid ice grains.

Formation of the Solar System: The gas giants were initially .....

The gas giants were initially worlds of rock and metal that pulled onto themselves large amounts of hydrogen and helium, along with some water.

refer to more info about the frost line >>>

The lower temperature in the nebula beyond the frost line makes many more solid grains available for accretion into planetesimals, which in turn results in much larger planets being formed

refer to pic of the formation of planets in our solar system >>>

This computer simulation shows the formation of the inner planets over time.

refer to description/pic of Young Circumstellar Disks of Matter >>>

This is the heart of the Orion Nebula as seen through the Hubble Space Telescope. The four insets are false-color images of proto-planetary disks within the nebula. A recently formed star is at the center of each disk. Our solar system is drawn to scale in the lower left image.

refer to info on Vesta in the asteroid belt >>>

This picture of the asteroid Vesta was taken in 2011 by the DAWN spacecraft. Vesta is the brightest asteroid, due to it being closer than the larger Ceres. The asteroid is comprised of rocky silicates with a small iron core. It has a mean diameter of 525km. The DAWN spacecraft visited the largest asteroid, Ceres, in late 2015.

refer to pic of Trappiste-1 Solar System (2016) >>>>

Trappiste-1 M*=0.09

refer to another pic of the Trappiste-1 Solar System (2016) >>>

Trappiste-1 solar system shows orbit & can get temperature too

Neptune's a = 30 AU which means it is...

at the edge of the solar system

why does an object oscillates?

because something (gravity) is pulling on it - planet's gravity on the star

Collapsing gas and dust heat through collisions and most of the material falls to the _____ to form the _____. The Sun forms in the_____, and planets form in an ____ ____.

center; sun center; outer disk

Materials moving in the same rotating orbit "rub shoulders" with other materials. These materials _____ and _____ together forming planetesimals, which continue to grow.

collide and stick

A planet and its star both orbit around their......, always staying on opposite sides of that point.

common center of mass

what method is used to discover new planets/objects in the sky?

doppler method

asteroids can fall out of orbit & get close to ____

earth

stars go through cycles. they live for a while then ____

explode

The bigger the planet, the ____ the star moves.

faster

the frost line is the ____ point

freezing

How are Planetary nebulae formed?

from the gaseous shells that are ejected from dying low-mass stars.

To Form a Star/Planets, we need .....

gas/dust

Forming Planetesimals by Accretion: ____ pulls objects together

gravity

what is the KEY/driving force to form the solar system?

gravity!

what does the amount of wobble has to do with a star?

has to do with size & closeness of planet

What does a planet's temperature depend on?

how far away it is from the sun

The sun is almost entirely made up of...

hydrogen

jovian planets have a lot of.... why?

hydrogen & helium; They began as bits of rock and ice that reached 15 Earth masses, and being so massive allows them to capture hold onto hydrogen and helium gas directly.

Comparative Planetology: Comets are debris that contain both ____ & ____.

ice & rock

what kind of materials does the asteroid belt contain?

icy & sometimes rocky objects - smaller objects, not planets but asteroids - in between zone of rocky planets & gaseous planets

For smaller stars, the Habitable Zone moves....

in closer to the star

Astronomers hypothesize that solar systems like ours form from ....

interstellar gas and dust clouds (Nebulae)

What is the largest planet in the solar system?

jupiter

Most of the exoplanets that have been discovered have _____ masses, roughly equal to the mass of Jupiter, and orbit ____ to their stars.

large; close

What's the problem with the transit method?

only works with a specific kind of orbit (refer to pic); images are virtually impossible

Trappiste-1 Solar System shows ____ & can also get the ____ too

orbits; temperature

Comparative Planetology: Pluto, once considered the smallest planet, has a size, density, and composition consistent with ....

other large Kuiper belt objects (KBOs).

The period of the star's motion is the same orbital period of the _____. What can be used to determine the planet distance a?

planet; Kepler's 3rd law can be used then to determine the planet distance a.

why is gravity key to form the solar system?

planets do not collide, don't form collisions & turn into bigger planets

exo planets are....

planets orbiting other stars

What are the two categories of planets?

rocky, gaseous

Comparative Planetology: Meteoroids are ____ pieces of such debris.

smaller (i.e.) smaller than 1 km/asteroids)

what does the frost line separate?

smaller terrestrial planets from the much larger Jovian planets in our solar system.

What is used to measure the doppler shift of the star's light?

spectroscopy, which produces a light spectrum

As a planet moves toward or away from us, its ____ moves in the opposite direction.

star

exo-planets orbit around the ____ , not ___

star; sun

why is the transit method a poor technique?

stars should look the same at all time, possible that planet orbiting will get right in front - periodic dips

Stars are not _____ when planets orbit them

stationary

jovian planets are gaseous like the ____ but much ____

sun; smaller

Using spectroscopy, we can measure the Doppler shift of the star's light, which reveals .....

the effects of the unseen planet or planets.

Both the planet & its star move in response to.... & both the planet and star orbit about their....

the gravity from the other object; Center of Mass

what does the oort cloud contain?

the material swarming around that never got absorbed/pulled in - not planets, objects!

what is an oort cloud?

the stuff circling outside the solar system -- a theoretical cloud of predominantly icy planetesimals proposed to surround the Sun; where comets are thought to be

Outer parts cool off more than the inner parts, because....

the temperature and density depend upon the distance from the proto-Sun

The closer to its star a planet it.....

the warmer the planet will be

what is the period of late heavy bombardment?

when a lot of debris & collisions were going on

how are exoplanets discovered?

Exoplanets are discovered indirectly as a result of their effects on the stars they orbit.

refer to info on the exo-planet, Gleise 581g >>>

Gliese 581g is an extrasolar planet claimed to orbit the red dwarf star Gliese 581, 22 light-years from Earth in the constellation of Libra. It is the sixth planet discovered orbiting the star. Gliese 581g has attracted attention because it is near the middle of the habitable zone of its parent star. That means it could sustain liquid water on its surface and could potentially host life similar to that on Earth. If it is a rocky planet, favorable atmospheric conditions could permit the presence of liquid water, a necessity for all known life, on its surface. With a mass 3.1 to 4.3 times Earth's, Gliese 581g is considered a super-Earth and is the planet closest in size to Earth known in a habitable zone. This makes it the most Earth-like Goldilocks planet found outside the Solar System and the exoplanet with the greatest recognized potential for harboring life. The supposed detection of Gliese 581g after such a short period of searching and at such close proximity has led some astronomers to hypothesize that the proportion of stars with habitable planets may be greater than ten percent.

terrestrial planets are low in.... why?

Hydrogen & Helium; because their low masses and gravity can't keep these gases from leaking into space.

refer to summary of the formation of the solar system >>>

Hydrogen, Helium, and traces of Lithium, the three lightest elements, were formed shortly after the formation of the universe (Big Bang). The heavier elements were produced much later by stars and are cast into space when stars died and exploded. By mass, 98% of the observed matter in the universe is Hydrogen and Helium. The solar system formed 4.6 billion years ago from a swirling, disk-shaped cloud of gas, ice, and dust called the solar nebula. The planets and other debris in the solar system today formed from gas, ice, and dust in the solar nebula orbiting the protosun. The outer solar system, beyond the frost line, had both dust and ice (including Hydrogen and Helium), while inside the frost line, such ices were vaporized by the protosun. The Sun formed at the center of the solar nebula. After about 100 million years, the temperature at the protosun's center was high enough to ignite thermonuclear fusion reactions. For 800 million years after the Sun formed, impacts of asteroid like objects on the young planets dominated the history of the solar system (Period of Late Heavy Bombardment).

Describe the Transit Method

If a planet happens to move in a plane that takes it across its star (that is, the planet transits the star), as seen from Earth, then the planet will hide some of the starlight, causing the star to dim. This change in star brightness will occur periodically and can reveal the presence of a planet.

Comparative Planetology: Asteroids are rocky and metallic debris in the solar system, are larger than about ____ in diameter, and are found primarily between the orbits of Mars and Jupiter, in the ____ _____

1 km ; asteroid belt

*Different Classifications of Solar System Objects: A planet is an object that....

1) Orbits the Sun. 2) Has enough mass so that its own gravitational attraction causes it to be essentially spherical. 3) Has enough gravitational attraction to clear its neighborhood of other orbiting debris.

What were the steps that led to the formation of our solar system?

1. The solar system is believed to have formed from a cloud of gas and dust in a process known as ACCRETION 2. As the gas cloud collapses its slight rotation increases, due to conservation of angular momentum.

refer to more info on exo-planets >>>

Astronomers have observed a few disks of gas and dust orbiting young stars. More than 3500 exoplanets have been discovered orbiting other stars.

refer to more info on the Categories of Solar System Objects >>>

Astronomical objects smaller than the eight planets are classified as dwarf planets or small solar system bodies (SSSBs). KBOs and Oort cloud objects are trans-Neptunian objects—they orbit farther from the Sun than the outermost planet Neptune. At least 1500 KBOs have been observed. A few potential Oort cloud objects have also been identified.