ASTROPHYSICS

UNIVERSE

ASTROPHYSICS

UNIVERSE

Know locationsKnow locations

The Solar SystemThe Solar System

The SunThe Sun

Mass: 1.99 x 1030 kg

Radius:6.96 x 108 m

Surface temperature: 5800 K

Mass: 1.99 x 1030 kg

Radius:6.96 x 108 m

Surface temperature: 5800 K

Planet Picture Distance to the Sun (km)

Radius (km) Orbital period

around its axis

Orbital period

Surface day temp

(ºC)

Density (water=1

)

Satellites

Mercury

58 million 4 878 km 59 days 88 days 167 5,43 0

Venus 108 million 12 104 km -243 days 225 days 464 5,24 0

Earth 149,6 million 12 756 km 23, 93 h 365,2 days 15 5,52 1

Mars 228 million 6 794 km 24h 37min 687 days -65 3,04 2

Jupiter 778 million 142 800 km 9h 50min 30s

12 years -110 1,32 +63

Saturn 1 427 million 120 000 km 10h 14min 29,5 years -140 0,69 +56

Uranus 2 870 million 51 800 km 16h 18min 84 years -195 1,27 27

Neptune

4 497 million 49 500 km 15h 48min 164 years -200 1,77 13

Pluto 5 900 million 2 400 km 6 days 248 years -225 2 1

Planets DataPlanets Data

Mercury and VenusMercury and Venus

Earth and MoonEarth and Moon

Mariner 10

Solar System FormationSolar System Formation1. Giant cloud of molecular Hydrogen gathered

together by gravity.2. Clumps of matter collapsed and heated up.3. Gas disc of young, spinning star evolved

planets (Estimated 4.6x109 years ago), asteroids & comets.

4. High temp. close to Sun allowed only the compounds with high condensation temperatures to remain solid – hence forming 4 terrestrial planets. (Mercury, Venus, Earth & Mars)

5. Further out, “gas giants” or “jovian,” planets form around cores of rock, metal and ice.

Earth and MoonEarth and Moon

MarsMars

Spirit Rover: Mars’ West Valley

MarsMars

MarsMars

Viking: Martian Face

ESA’s Mars Express: Cydonia Region

Know locationKnow location

Asteroid BeltAsteroid BeltCeres (480km): it was the first asteroid to be seen. Now it’s a dwarf planet.

Mathilde (52km)

Eros (13x13x33km

)

JupiterJupiter

Jupiter and its moons: Io, Europa, Ganymede and Callisto

Approximate size comparison of Earth and Jupiter

SaturnSaturn

A rough comparison of the sizes of Saturn and Earth

UranusUranus

Size comparison of Earth and Uranus

NeptuneNeptune

Size comparison of Neptune and Earth.

Other Solar System Objects

Other Solar System Objects

• Kuiper belt - Beyond Neptune• Source of many dwarf planets, asteroids and

short-period comets. • Larger than the asteroid belt.

• Asteroid belt – Between Mars & Jupiter• Possibly formed from a terrestrial planet that

was destroyed. • Rocky objects with irregular shapes for those

whose size < 300Km because they couldn’t form a sphere.

• Some could be called minor planets (Ceres d=106m).

• Comets – • Irregularly shaped bodies of ice & rock • Very elliptical orbits. • Comet tail: points away from sun, is vaporized

gases.

Star GroupsStar Groups• Binary Stars –Two stars around a center of mass• Stellar Cluster

• Close enough to be held together by gravity.• Few dozen to millions of stars.• All formed at the same time.Open Cluster: i.e. Pleides (≈500 stars)• Up to several 100 stars• Younger than 10 Billion years thus may still have

some dust & gas• In our galaxy so in a single plane.Globular Cluster• Many more stars & older than 11 billion

yrs.• Roughly spherical in shape – little or no dust or

gas.• Just outside Milky Way in “galactic halo.”

GalaxiesGalaxies

A galaxy is a collection of a very large number of stars mutually attracting each other through the gravitational force and staying together. The number of stars varies between a few million and hundreds of billions. There approximately 100 billion galaxies in the observable universe.

There are three types of galaxies:

- Spiral (Milky Way)

- Elliptical (M49)

- Irregular (Magellanic Clouds)

Spiral GalaxiesSpiral Galaxies

Spiral galaxies consist of a rotating disk of stars and interstellar medium, along with a central bulge of generally older stars. Extending outward from the bulge are relatively bright arms.

Milky Way

Spiral GalaxiesSpiral Galaxies

Andromeda

Spiral GalaxiesSpiral Galaxies

Sombrero Galaxy

Elliptical GalaxiesElliptical Galaxies

M49

Elliptical cross-section and no spiral arms.They range in shape from nearly spherical to highly flattened ellipsoids and in size from hundreds of millions to over one trillion stars.In the outer regions, many stars are grouped into globular clusters.

ESO 325-G004

Irregular GalaxiesIrregular Galaxies

Irregular galaxies have no specific structure. The Large and Small Magellanic Clouds, the nearest galaxies, are an example of irregular galaxies.

Small Magellanic Cloud Hoag's Object, a ring galaxy.

ConstellationsConstellations

A group of stars in a recognizable pattern that appear to be near each other in space.

Orion

PolarisPolaris

NebulaeNebulae

Nebula is an interstellar cloud of dust, hydrogen gas and plasma. It is the first stage of a star's cycle but it can also refer to the remains of a dying star (planetary nebula).

Originally nebula was a general name for any extended astronomical object, including galaxies beyond the Milky Way (some examples of the older usage survive; for example, the Andromeda Galaxy was referred to as the Andromeda Nebula before galaxies were discovered by Edwin Hubble).

Nebulae often form star-forming regions, such as in the Eagle Nebula.

NebulaeNebulae

Eagle Nebula and the Cone nebula:

star-forming regions

Cat’s Eye NebulaCat’s Eye Nebula

Planetary nebulae are nebulae that form from the gaseous shells that are ejected from low-mass giant stars when they transform into white dwarfs.

Eskimo nebulaEskimo nebula

?????? What is the difference between a

stellar cluster and a galaxy? How do constellations differ from

stellar clusters or galaxies? What are the two ways nebulae

can be formed? 1. Nuclei captured electrons

electrostatically forming dust & gas clouds of Hydrogen.

2. Matter ejected from a super novae.

What is the difference between a stellar cluster and a galaxy?

How do constellations differ from stellar clusters or galaxies?

What are the two ways nebulae can be formed? 1. Nuclei captured electrons

electrostatically forming dust & gas clouds of Hydrogen.

2. Matter ejected from a super novae.

SupernovasSupernovas

Eta Carinae Crab Nebula

Astronomical DistancesAstronomical Distances 1 ly 9.46x1015mlight year: Distance light can go in a

year traveling at 3E8ms-1

1 AU 1 AU 1.50x101.50x101111m m

Astronomical Unit: Average distance Astronomical Unit: Average distance between Earth and Sun.between Earth and Sun.

1 pc1 pc 3.26 ly= 3.09x103.26 ly= 3.09x101616mm

parsec: most commonly used parsec: most commonly used system of distance in astrophysics.system of distance in astrophysics.

1 ly 9.46x1015mlight year: Distance light can go in a

year traveling at 3E8ms-1

1 AU 1 AU 1.50x101.50x101111m m

Astronomical Unit: Average distance Astronomical Unit: Average distance between Earth and Sun.between Earth and Sun.

1 pc1 pc 3.26 ly= 3.09x103.26 ly= 3.09x101616mm

parsec: most commonly used parsec: most commonly used system of distance in astrophysics.system of distance in astrophysics.

?????? How many minutes does it take light

from the sun to reach the earth? about 8 minutes

Distances between stars in a galaxy are often given in kpc. What does this stand for? Kiloparsecs

How might you represent distances between galaxies? Mpc or Gpc

How many minutes does it take light from the sun to reach the earth? about 8 minutes

Distances between stars in a galaxy are often given in kpc. What does this stand for? Kiloparsecs

How might you represent distances between galaxies? Mpc or Gpc