Module 3: Formation of Stars and Planets Flashcards
Composition of the Universe
Dark Energy, Dark Matter, (Visible) Matter
Cosmic Microwave Background
Validates the composition of the universe
CMB Analyser
shows the energy signature varies as some of the more important input parameters of our universe are modified
composition of the universe:
Atoms
(Cold) Dark Matter
Dark Energy
Hubble constant
Reionization Redshift
Spectral Index
Hubble Constant
indicates how fast the universe is currently expanding (in units of kilometres per sec per Megaparsec).
It is a measure of how fast an object is moving away from us based upon its distance from the Earth today.
Reionization Redshift
The era when the first stars formed, expressed in redshift units.
The radiation produced by the first stars stripped electrons off hydrogen atoms in the surrounding gas.
Spectral Index
Describes the initial density ripples in the universe.
A smaller spectral index means the ripples with longer wavelengths are stronger and with shorter wavelengths weaker.
% composition of the universe
Atoms: 4%
Cold Dark Matter: 22%
Dark Energy: 74%
Hubble Constant: 73
Reionization Redshift: 11
Spectral Index: 0.95
What could be one of the reasons why there is an uneven distribution of matter?
clue: Influence of one of the fundamental forces
Stellar Evolution
A description of the way that stars change with time.
The primary factor determining how the star evolves is its mass as it reaches the main sequence.
Hertzsprung-Rusell Diagram
the most important tools in the study of stellar evolution.
1900s
Ejnar Hertzsprung and Henry Norris Russell
it plots the temperature of star against their luminosity
Low-mass Stars
<8 solar masses
High-mass stars
> 8 solar masses
(Solar) Nebular Hypothesis
formation of our solar system
- Large bodies in the solar system have orderly motions.
- There are two types of planets: terrestrial and Jovian planets
- Asteroids and comets ecist in certain regions of the solar system
- Notable exceptions to these trends stand out( unusual rotation axis tilts, large moons, unusual orbits)
Terrestrial Planets
smaller size and mass
higher density
solid surface
few moons and rings
closer to the sun
Mercury, Venus, Earth, Mars
Jovian Planets
large size and mass
lower density (H and He)
no solid surface
rings and many moons
farther to the sun
Jupiter, Saturn, Uranus, Neptune
Two Principle in Nebular Theory
- Newton’s Law of Gravity (Gravitational potential energy ➡️heat)
- Conservation of Angular Momentum (rotational motion is conserved)
Solar Nebula
Is the cloud of gas from which our own Solar System formed.
Formation of Planets
- Cloud Collapse
- Formation of Protoplanetary disk
- Growth of planets
evidences of the nebular theory were observed through cosmic event in the neighboring galactic nebula, M16
Why Pluto is no longer considered as a planet
three criteria waits
It is a type of matter which does not interact with the electromagnetic force. This means that it does not absorb, reflect, or emit light, making it extremely hard to detect.
Dark Matter
What percentage of visible matter (the matter we know that makes up all stars and galaxies) is present in the universe?
5%
What percentage is the composition of dark matter in the whole universe?
27%
It is the very first generation of stars which do not have any metal at all.
Population III stars
These are old, metal-poor stars.
Population II stars
These are stars rich in atoms heavier than helium; nearly always a relatively young star found in the disk of the galaxy.
Population I stars
This is the minimum mass that a clump of gas must have to collapse under its gravity which is proportional to the square of the gas temperature and inversely proportional to the square root of the gas pressure.
Jeans mass
It is defined by the Oxford English Dictionary as a state of “violent commotion, agitation, or disturbance,” with a turbulent fluid further defined as one “in which the velocity at any point fluctuates irregularly.” It plays a dual role, both creating overdensities to initiate gravitational contraction or collapse, and countering the effects of gravity in these overdense regions.
Turbulence
This hypothesis posits that a giant cloud of molecular gas and dust underwent gravitational collapse, possibly due to shock waves from a nearby supernova explosion. Pockets of dust and gas began to collect into denser regions. As the denser regions pulled in more and more matter, conservation of momentum caused it to begin rotating, while increasing pressure caused it to heat up. Most of the material ended up in a ball at the center while the rest of the matter flattened out into a disk that circled around it. While the ball at the center formed the Sun, the rest of the material would form into the protoplanetary disk.
Nebular hypothesis
The formation of the planets is believed to follow a sequence of these steps.
- Gravitational collapse
- From dust to planetisimals
- From planetisimals to protoplanets
- From protoplanets to giant planets
- From protoplanets to terrestrial planets
- Orbital migration
These planets include Mercury, Venus, Earth, and Mars — are closer to the Sun and they consist of a core composed mostly of iron, a mantle composed of rock (mostly silicates), and an atmosphere whose mass is a negligible fraction of the total mass of the planet.
Terrestrial planets
These planets include Jupiter and Saturn are 300 and 100 times more massive than the Earth, respectively, and are mostly composed of a mixture of hydrogen and helium in the same proportion as is found in the Sun.
Gas giants
These planets include Uranus and Neptune are at the outer edge of the solar system, are roughly 15 times more massive than the Earth, and are composed of roughly equal parts each of rock, ice, and a hydrogen-helium mix.
Ice giants
What are the different categories of exoplanets seen so far?
▪ Hot Jupiters
▪ Giant planets with eccentric orbits
▪ Super-Earths
These exoplanets are Jupiter-like planets orbiting very close to their stars with periods of only a few days.
Hot Jupiters
These exoplanets are generally found in compact systems of two to four planets each, orbiting their stars at distances from 0.006 to 1 au in periods ranging from more than 100 days down to hours. Although there are no super-Earths in our Solar System, they orbit at least 40% of all nearby Sun-like stars, which makes them the most common type of planet found.
Super-Earths
