A Look At Our Solar System And Beyond

A Look At Our Solar System And Beyond

Our Solar System

Our Solar System

• the Sun• the eight planets • more than 130 satellites of the planets• a large number of small bodies (the comets

and asteroids)• and the interplanetary medium• (There are probably also many more

planetary satellites that have not yet been discovered)

The Sun

• Our Sun is a normal main-sequence G2 star, one of more than 100 billion stars in our galaxy.

• Diameter: 1,390,000 km• Mass: 1.989 x 1030 kg• Temperature: 5800 K

(surface) 15,600,000 K (core)

The Sun

• The Sun is by far the largest object in the solar system. It contains more than 99.8% of the total mass of the Solar System– (Jupiter contains

most of the rest)

The Sun

• It is often said that the Sun is an "ordinary" star. That's true in the sense that there are many others similar to it. But there are many more smaller stars than larger ones; the Sun is in the top 10% by mass.

• The median size of stars in our galaxy is probably less than half the mass of the Sun.

The Sun

• The Sun is, at present, about 70% hydrogen and 28% helium by mass everything else ("metals") amounts to less than 2%.

• This changes slowly over time as the Sun converts hydrogen to helium in its core.

The Sun

• The Sun's energy output (386 billion billion megawatts) is produced by nuclear fusion reactions.

• Each second about 700,000,000 tons of hydrogen are converted to about 695,000,000 tons of helium and 5,000,000 tons of energy in the form of gamma rays

The Inner Planets

Mercury

Mercury

• Orbit: 57,910,000 km (0.38 AU) from Sun

• Diameter: 4,880 km

• Mass: 3.30 x 1023 kg

• Temperature variations on Mercury are the most extreme in the solar system ranging from 90 K to 700 K

Mercury

• Mercury has a small magnetic field whose strength is about 1% of Earth's

• Mercury has no known satellites

Mercury

• Mercury has been visited by only one spacecraft, Mariner 10.

• It flew by three times in 1974 and 1975.• Only 45% of the surface was mapped

(and, unfortunately, it is too close to the Sun to be safely imaged by HST).

• A new discovery-class mission to Mercury, MESSENGER was launched by NASA in 2004 and will orbit Mercury starting in 2011 after several flybys

Venus

Venus

• Orbit: 108,200,000 km (0.72 AU) from Sun• Diameter: 12,103.6 km• Mass: 4.869 x 1024 kg

• Venus is sometimes regarded as Earth's sister planet. In some ways they are very similar: – Venus is only slightly smaller than Earth (95% of

Earth's diameter, 80% of Earth's mass). – Both have few craters indicating relatively young

surfaces. – Their densities and chemical compositions are similar.

Venus• Because of these similarities, it was

thought that below its dense clouds Venus might be very Earthlike and might even have life.

• But, unfortunately, more detailed study of Venus reveals that it may be the least hospitable place for life in the solar system.

Venus• The pressure of Venus'

atmosphere at the surface is 90 atmospheres.

• That’s about the pressure at a depth of 1 km of below ocean!!

• It is composed mostly of carbon dioxide.

• There are several layers of clouds many kilometers thick composed of sulfuric acid

Venus• The dense atmosphere produces

a greenhouse effect that raises Venus' surface temperature by about 400 degrees to over 740 K (hot enough to melt lead)

• Venus' surface is actually hotter than Mercury's despite being nearly twice as far from the Sun.

Image from Pioneer Venus

Akna Mountains and Crater Wanda

7 Pancake Volcanoes

Photos from Soviet Venera 13 Spacecraft

Earth

Earth• Orbit: 149,600,000 km (1.00 AU) from Sun• Diameter: 12,756.3 km• Mass: 5.972 x 1024 kg

• It was not until the time of Copernicus (the sixteenth century) that it was understood that the Earth is just another planet!!

Earth

• The core is probably composed mostly of iron (or nickel/iron) though it is possible that some lighter elements may be present, too.

• Temperatures at the center of the core may be as high as 7500 K, hotter than the surface of the Sun.

• We know most of this only from seismic techniques.

• Crust divided into several plates• Plates float on top of mantle• Surface recreated every 500,000,000 years• Oldest rocks 4 billion years old• Rocks older than 3 billion are rare• Oldest fossils are 3.9 billion years old (algae)

Earth

• 71 Percent of the Earth's surface is covered with water

• The Earth's atmosphere is 77% nitrogen, 21% oxygen, with traces of argon, carbon dioxide and water

Strait of Gibraltar from Shuttle

Earth• Earth has a modest

magnetic field produced by electric currents in the outer core.

• The interaction of the solar wind, the Earth's magnetic field and the Earth's upper atmosphere causes the auroras!! (Northern Lights)

Moon

•First landed on moon in July 1969

•Last went to moon in 1972

•Less than 10 people have ever walked on the moon

Moon

• Orbit: 384,400 km from Earth

• Diameter: 3476 km

• Mass: 7.35 x 1022 kg

Moon - Tides

• The gravitational forces between the Earth and the Moon cause some interesting effects.

• The most obvious is the tides. The Moon's gravitational attraction is stronger on the side of the Earth nearest to the Moon and weaker on the opposite side.

Moon - Tides

• Since the Earth, and particularly the oceans, is not perfectly rigid it is stretched out along the line toward the Moon.

• From our perspective on the Earth's surface we see two small bulges, one in the direction of the Moon and one directly opposite.

Mars

Mars

• Orbit: 227,940,000 km (1.52 AU) from Sun

• Diameter: 6,794 km• Mass: 6.4219 x 1023 kg• Temperature: 140 K (-207

F) at the pole in winter, 300 K (80 F) at equator in summer.

• Has two moons - Phobos & Deimos

Mars

• The first spacecraft to visit Mars was Mariner 4 in 1965.

• Several others followed including Mars 2, the first spacecraft to land on Mars and the two Viking landers in 1976.

• Ending a long 20 year hiatus, Mars Pathfinder landed successfully on Mars on 1997 July 4.

• In 2004 the Mars Expedition Rovers "Spirit" and "Opportunity" landed on Mars sending back geologic data and many pictures; they are still operating after more than a year on Mars.

Mars

• Three Mars orbiters (Mars Global Surveyor, Mars Odyssey, and Mars Express) are also currently in operation.

• Olympus Mons--78,000 ft high, about the area of Arizona

• Valles Marineris--System of canyons, 4000 km long, 2-7 km deep

Candor Chasma in Valles Marineris on Mars

The Outer Planets

• Several hundred thousand known asteroids• 26 larger than 200 km wide• Total mass of all asteroids less than mass of

moon• Largest: 1 Ceres--988 km in diameter, accounts

for 25% of all asteroid mass in solar system.• Asteroid belt exists between Mars and Jupiter,

about 2-4 AU from sun

Jupiter

• Orbit: 778,330,000 km (5.20 AU) from Sun

• Diameter: 142,984 km (equatorial)

• Mass: 1.900 x 1027 kg • Jupiter is more than

twice as massive as all the other planets combined (the mass of Jupiter is 318 times that of Earth)

• Jupiter was first visited by Pioneer 10 in 1973 and later by Pioneer 11, Voyager 1, Voyager 2 and Ulysses.

• The spacecraft Galileo orbited Jupiter for eight years.

• It is still regularly observed by the Hubble Space Telescope.

• The gas planets do not have solid surfaces, their gaseous material simply gets denser with depth

• Our knowledge of the interior of Jupiter (and the other gas planets) is highly indirect and likely to remain so for some time. (The data from Galileo's atmospheric probe goes down only about 150 km below the cloud tops.)

• Jupiter probably has a core of rocky material amounting to something like 10 to 15 Earth-masses.

• Jupiter and the other gas planets have high velocity winds which are confined in wide bands of latitude.

• The winds blow in opposite directions in adjacent bands.

• The colors correlate with the cloud's altitude: blue lowest, followed by browns and whites, with reds highest.

• Sometimes we see the lower layers through holes in the upper ones.

• The Great Red Spot (GRS) has been seen by Earthly observers for more than 300 years

• Infrared observations and the direction of its rotation indicate that the GRS is a high-pressure region whose cloud tops are significantly higher and colder than the surrounding regions

• Jupiter has a huge magnetic field, much stronger than Earth's

• Jupiter has 63 known satellites (as of Feb 2004): the four large Galilean moons plus many more small ones some of which have not yet been named.

Io

• Similar to terrestrial planets• Active volcanoes

Europa

• Very young surface• Surface strongly resembles a sea of ice• Possible water 50 km deep• Life?

Ganymede

Callisto

Saturn

• Orbit: 1,429,400,000 km (9.54 AU) from Sun• Diameter: 120,536 km (equatorial)• Mass: 5.68 x 1026 kg

• Saturn was first visited by NASA's Pioneer 11 in 1979 and later by Voyager 1 and Voyager 2.

• Cassini (a joint NASA / ESA project) arrived on July 1, 2004 and will orbit Saturn for at least four years.

• Like Jupiter, Saturn is about 75% hydrogen and 25% helium with traces of water, methane, ammonia and "rock”

• Saturn's interior is similar to Jupiter's consisting of a rocky core, a liquid metallic hydrogen layer and a molecular hydrogen layer.

• Saturn's interior is hot (12000 K at the core) and Saturn radiates more energy into space than it receives from the Sun. Most of the extra energy is generated by the Kelvin-Helmholtz mechanism as in Jupiter

• Saturn’s rings look continuous from the Earth, but they are actually composed of innumerable small particles each in an independent orbit.

• They range in size from a centimeter or so to several meters.

• A few kilometer-sized objects are also likely.

• Saturn's rings are extraordinarily thin: though they're 250,000 km or more in diameter they're less than one kilometer thick.

• Despite their impressive appearance, there's really very little material in the rings

• If the rings were compressed into a single body it would be no more than 100 km across.

• The ring particles seem to be composed primarily of water ice, but they may also include rocky particles with icy coatings.

• Saturn has 34 named satellites• Mimas reveals evidence of a major impact

Uranus

• Pronunciation:

• Not to be confused with “urine us” or “your anus”

• Orbit: 2,870,990,000 km (19.218 AU) from Sun• Diameter: 51,118 km (equatorial)• Mass: 8.683 x 1025 kg

• Uranus has been visited by only one spacecraft, Voyager 2 on Jan 24 1986

• Uranus rotates on its sides… so the poles point directly towards the sun.

• However, the equator is still the hottest?!

• Uranus also has rings

Neptune

• After the discovery of Uranus, it was noticed that its orbit was not as it should be in accordance with Newton's laws.

• It was therefore predicted that another more distant planet must be perturbing Uranus' orbit

• Because Pluto's orbit is so eccentric, it sometimes crosses the orbit of Neptune making Neptune the most distant planet from the Sun for a few years.

• Neptune has been visited by only one spacecraft, Voyager 2 on Aug 25 1989. Much of we know about Neptune comes from this single encounter

• Like a typical gas planet, Neptune has rapid winds confined to bands of latitude and large storms or vortices. Neptune's winds are the fastest in the solar system, reaching 2000 km/hour

• Neptune's most prominent feature was the Great Dark Spot (left) in the southern hemisphere.

• A small irregular white cloud zips around Neptune every 16 hours or so - now known as “The Scooter”.

• It may be a plume rising from lower in the atmosphere but its true nature remains a mystery

Pluto

• Orbit: 5,913,520,000 km (39.5 AU) from the Sun (average)

• Diameter: 2274 km• Mass: 1.27 x 1022 kg• Pluto has a satellite,

Charon

New Horizons

• Early Cruise: The first 13 months include spacecraft and instrument checkouts, instrument calibrations, trajectory correction maneuvers, and rehearsals for the Jupiter encounter.

• Jupiter Encounter: Closest approach occurred Feb. 28, 2007. Moving about 47,000 miles per hour (about 21 kilometers per second), New Horizons would fly 3 to 4 times closer to Jupiter than the Cassini spacecraft, coming within 32 Jupiter radii of the large planet.

• Interplanetary Cruise: activities during the approximately 8-year cruise to Pluto include annual spacecraft and instrument checkouts, trajectory corrections, instrument calibrations and Pluto encounter rehearsals.

• You need pretty large antennas to send data over billions of miles - and fortunately, NASA has them.

The New Horizons mission operations team will communicate with the spacecraft through NASA's Deep Space Network (DSN) of antenna stations.

Information on the mission can be found at:http://pluto.jhuapl.edu/index.php

Asteroid or Planet?

• There are some who think Pluto would be better classified as a large asteroid or comet rather than as a planet

• Further complicating the situation, one such object (2003UB313) was recently discovered that is almost certainly larger than Pluto. Should it, too, be classified as a planet?

• Dwarf Planet?

Kuiper Belt

• Distance: 30-100 AU from sun• Consists of small, icy objects

• Dirty snowballs• 878 known comets• Highly elliptical orbits• Dust tail--particles blasted off comet by sun;

always point away from sun• Stardust mission approached comet in 1/04,

will return sample to Earth

Hubble Telescope

• The colors in Hubble images, which are assigned for various reasons, aren't always what we'd see if we were able to visit the imaged objects in a spacecraft. We often use color as a tool, whether it is to enhance an object's detail or to visualize what ordinarily could never be seen by the human eye.

• http://hubblesite.org

Galaxies

• Spirals: They have a central bulge with a flattened disk, normally depicting spiral arms.

• Barred Spirals: Almost same as spirals but for the existence of a bar in the central region.

• Ellipticals: They are roundish non-flattened galaxies. They generally have very little gas and dust when compared with spiral galaxies. They have few young stars, stars that were just formed, with no spiral structure.  

• Irregulars: Whatever galaxies that do not fall into the first three classifications are hereunder. 

• The Milky Way is the galaxy which is the home of our Solar System together with at least 200 billion other stars (more recent estimates have given numbers around 400 billion) and their planets, and thousands of clusters and nebulae.

• As a galaxy, the Milky Way is actually a giant, as its mass is probably between 750 billion and one trillion solar masses, and its diameter is about 100,000 light years.

• The Halo consists of the oldest stars known, including about 146 Globular Clusters.

• The disk of the Galaxy is a flattened, rotating system which contains the Sun and other intermediate-to-young stars.

• The sun sits about 2/3 of the way from the center to the edge of the disk

• The sun revolves around the center of the galaxy about once every 250 million years

• The Milky Way Galaxy belongs to the Local Group, a smaller group of 3 large and over 30 small galaxies, and is the second largest (after the Andromeda Galaxy M31) but perhaps the most massive member of this group.

The Majestic Sombrero Galaxy (Messier 104)

Barred Spiral Galaxy NGC 1300

Andromeda Galaxy

The Universe…Where did it come from?

• The Universe means all there is!

• The Big Bang Theory:– It’s a model used to describe the creation of

the universe– The universe was created in a violent event 10-

13 billion years ago– As a result, the universe is still expanding…

Evolution of the Universe

• Cosmologists are scientists who study the evolution of the universe– At the start: a dense fireball – a single point– 3 minutes after the Big Bang: 500,000,000

degrees F or 277,777,760 degrees Celsius. H & He form

– 50,000 yrs after Big Bang: atoms start to form– 300,000,000 yrs after Big Bang: the universe

expands and is cool enough for galaxies to form

Proof for the Big Bang

• Remember the Doppler Effect with sound?

• It works for light too!

• Light can shift it’s frequency depending on the motion of the object that is emitting light

Proof for the Big Bang

•Edwin Hubble saw other galaxies in the 1920’s•He noticed that the light from these galaxies was shifted to the red end of the spectrum.•This means that all galaxies are moving away from each other•The universe is expanding

Proof for the Big Bang

• Cosmic Background Radiation

• light left over from the Big Bang shifted to microwave wavelengths

• the whole universe has this after glow

Cosmic Background Radiation

The Future is Uncertain

• 1) The universe will expand forever

• 2) The expansion will slow down and the universe will reach its limit

• 3) The universe will stop expanding and fall back

• ** GRAVITY pulls in, EXPANSION pulls out

Nebula

• A planetary nebula is created when a star blows off its outer layers after it has run out of fuel to burn.

• These outer layers of gas expand into space, forming a nebula which is often the shape of a ring or bubble.

• At the center of a planetary nebula the glowing, left-over central part of the star from which it came can usually still be seen.

Hourglass Nebula

Red Supergiant Star V838 Moncerotis

• Black holes are the evolutionary endpoints of stars at least 10 to 15 times as massive as the Sun.

• With no outward forces to oppose gravitational forces, the remnant will collapse in on itself. The star eventually collapses to the point of zero volume and infinite density

• HDE 226868 is a B0 supergiant with a surface temperature of about 31,000 K.

• Spectroscopic observations show that the spectral lines of HDE 226868 shift back and forth with a period of 5.6 days.