Heaven and Earth

Earth, sun and solar system
 Formed 4.6 billions years ago.
 Sun and all planets were born together from the
collapse of a giant molecular cloud.
 Vast majority of the system's mass is in the Sun, with
most of the remaining mass contained in Jupiter.

Earth, sun and solar system
 Mercury, Venus, Earth and Mars - four smaller inner “terrestrial”
planets - primarily composed of rock and metal.
 Then, we have the asteroid belt.
 Jupiter, Saturn, Uranus, Neptune - four outer planets, or the gas giants
 Jupiter and Saturn - composed mainly of hydrogen and helium.
 Uranus and Neptune - composed of “iced” gases - water, ammonia and
methane
 All planets have almost circular orbits that lie within a nearly flat disc
called the ecliptic plane.

Beyond Neptune
 Beyond Neptune's orbit lie the Kuiper belt and scattered disc - trans-
Neptunian objects composed mostly of ices.

Beyond Neptune
 Several dozen to more than 10,000 objects may be
large enough to have been rounded by their own
gravity - dwarf planets.
 Asteroid Ceres and the trans-Neptunian objects Pluto,
Eris, Haumea, and Makemake.
 Comets, centaurs and interplanetary dust freely travel
between regions.

Oort cloud
 Hypothesized
spherical cloud of
comets - nearly a
light-year, from the
Sun.
 A quarter of the
distance to Proxima
Centauri, the nearest
star to the Sun

Oort cloud
 The outer limit of the Oort cloud defines the
cosmographical boundary of the Solar System and the
region of the Sun's gravitational dominance.
 Sedna is a large trans-Neptunian object, which is about
three times as far from the Sun as Neptune.

Solar system completed
 The Solar System is located within one of the outer arms of Milky Way
galaxy, which contains about 200 - 400 billion stars.

Nearest stars
 Proxima Centauri - a red dwarf star about 4.24 light-
years distant from Sun.
 Too faint to be seen with the naked eye.
 Second- and third-nearest stars - the bright binary
Alpha Centauri
 Proxima Centauri may be part of a triple star system
with Alpha Centauri A and B.

Milky Way
 The Milky Way
is the galaxy
that contains
our Solar
System.

Milky Way - Facts
 A spiral galaxy 100,000–120,000 light-years in diameter
 Containing 200–400 billion stars - may contain at least as many planets.
 Center is marked by an intense radio source named Sagittarius A* which is likely to be a
supermassive black hole.
 Rotates differentially, faster towards the center and slower towards the outer edge.
 The rotational period is about 200 million years at the position of the Sun.
 The Galaxy as a whole is moving at a velocity of 552 to 630 km per second.
 It is estimated to be about 13.2 billion years old, nearly as old as the Universe.
 Surrounded by several smaller satellite galaxies, the Milky Way is part of the Local Group
of galaxies, which forms a subcomponent of the Virgo Supercluster.

Virgo Supercluster
 Contains the Virgo Cluster in
addition to the Local Group,
which in turn contains the
Milky Way and Andromeda
galaxies.
 At least 100 galaxy groups and
clusters are located within its
diameter of 33 megaparsecs
(110 million light-years).
 It is one of millions of
superclusters in the observable
Universe.

Nearest Galaxy
 Andromeda Galaxy

Andromeda
 Approximately 2.5 million light-years from Earth.
 Contains one trillion (1012) stars: at least twice the number
of stars in the Milky Way.
 Visible at naked eye.
 The two galaxies are expected to collide in 3.75 billion
years, eventually merging to form a giant elliptical galaxy.
 There are probably more than 170 billion (1.7 × 1011)
galaxies in the observable Universe.

Furthest galaxies
 MACS0647-JD - a candidate for the farthest known
galaxy from Earth and is at 13.3 billion light-years away.
 It formed 420 million years after the Big Bang. It is less
than 600 light-years wide.

Quasars, pulsars and neutron stars
 Pulsar - is a highly magnetized, rotating neutron star
that emits a beam of electromagnetic radiation. Acts as
a light house.

 Neutron stars - is a type of stellar remnant that can result
from the gravitational collapse of a massive star.
 Composed almost entirely of neutrons.
 Very dense - A typical neutron star has a mass between
about 1.4 and 3.2 solar masses with a corresponding radius
of about 12 km - approximately equivalent to the mass of a
Boeing 747 compressed to the size of a small grain of sand.
 Some neutron stars rotate very rapidly and emit beams of
electromagnetic radiation as pulsars.

 Quasar - is a very energetic and distant active galactic
nucleus.
 The most luminous, powerful, and energetic objects
known in the universe.
 A compact region in the center of a massive galaxy
surrounding its central supermassive black hole.

Quasars
 They tend to inhabit the very centers of active young
galaxies and can emit up to a thousand times the
energy output of the Milky Way.
 When combined with Hubble's law, the implication of
the redshift is that the quasars are very distant—and
thus, it follows, objects from much earlier in the
universe's history.

Universe
 Commonly defined as the totality of existence,
including planets, stars, galaxies, the contents of
intergalactic space, and all matter and energy.
 At least 93 billion light years in diameter.
 Has been governed by the same physical laws and
constants throughout most of its extent and history.
 Big Bang Theory - about 13.7 billion years ago.

Observable Universe
 Some parts of the universe may simply be too far away
for the light emitted from there at any moment since
the Big Bang to have had enough time to reach Earth
at present, so these portions of the universe would
currently lie outside the observable universe.
 In the future the light from distant galaxies will have
had more time to travel, so some regions not currently
observable will become observable in the future.

Dark matter and dark energy
 Dark matter
 hypothesized to account for a large part of the total mass
in the universe.
 cannot be seen directly with telescopes; evidently it
neither emits nor absorbs light or other electromagnetic
radiation.
 inferred from its gravitational effects on visible matter,
radiation, and the large scale structure of the universe.

Dark matter and dark energy
 Dark energy
 hypothetical form of energy that permeates all of space
and tends to accelerate the expansion of the universe.
 is the most accepted hypothesis to explain that the
universe is expanding at an accelerating rate.

Theories about the end of the universe
 Big Freeze or heat death
 Big Rip
 Big Crunch - This scenario allows the Big Bang to be
immediately after the Big Crunch of a preceding
universe - cyclic model of oscillatory universe.
 Big Bounce
 False vacuum
 Cosmic uncertainty
 Multiverse

Multiverse
 the hypothetical set of
multiple possible
universes (including the
historical universe we
consistently experience)
that together comprise
everything that exists and
can exist: the entirety of
space, time, matter, and
energy as well as the
physical laws and
constants that describe
them. The various
universes within the
multiverse are sometimes
called parallel universes.

Fermi Paradox
 The Sun is a young star. There are billions of stars in the galaxy
that are billions of years older;
 Some of these stars likely have Earth-like planets which, if the
Earth is typical, may develop intelligent life;
 Presumably some of these civilizations will develop interstellar
travel, as Earth seems likely to do;
 At any practical pace of interstellar travel, the galaxy can be
completely colonized in just a few tens of millions of years.
 Where is everybody?

Heaven and Earth

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