CELESTIAL BODIESA History of Planetary Discovery

PART I: CLASSICAL PLANETSO Venus, beauty of the skies,

To whom a thousand temples rise, Gaily false in gentle smiles, Full of love-perplexing wiles;

O goddess, from my heart remove The wasting cares and pains of love.

- Sappho, Greece, ~600 BCE

asteres planetai

Ancient Greek: wandering stars

Apparent MagnitudeVisible to the typical human eye

Apparent magnitude

Brightness relative to Vega

Number of stars brighter than apparent magnitude

Yes -1.0 250% 1

0 100% 4

1 40% 15

2 16% 48

3 6.30% 171

4 2.50% 513

5 1.00% 1602

6 0.40% 4800

6.5 0.25% 9096

No 7 0.16% 14000

8 0.06% 42000

9 0.03% 121000

10 0.01% 340000

Mars AM: -3.0 to +1.6 Orbital period: 686 days

Saturn AM: -0.24 to +1.47 Orbital period: 29.5 years

Jupiter AM: -2.94 to -1.6 Orbital period: 11.9 years

Mercury AM: -2.6 to +5.7 Orbital period: 88 days

Venus AM: -4.9 to -3.8 Orbital period: 224 days

Venus The Morningstar and Eveningstar Brightest objet in the sky, after the moon Overtakes Earth every 584 days, moving

from being visible in the morning to the evening

Mayan astronomy

Mayans Chack ek - the Great Star Thought to influence life on Earth;

wars and other important events timed based on its position

Mayans Dresden Codex included an almanac showing full cycle in five sets of 584 days each

Yolngu (Northern Australia) Barnumbirr In the early hours before dawn, Venus draws a rope of light attached

to Earth Along this Morning Star Pole, the people can communicate with their

ancestors

Babylonian Astronomy

Babylonian Venus Tablets Ammisaduqua, 7th century BCE Babylonians were first recorded civilization to recognize

astronomical phenomena as periodic and apply math Venus tablets recorded rising and setting of Venus over 21

years Babylonian astrologers laid foundation for western

astrology

Ancient Greece Developed mathematical models for

predicting the paths of planets Named planets after gods; Roman

interpretations give todays names 2nd century Almagest provided

geocentric model that was astronomical standard for 1,200 years

PART II: MODERN PLANETSLe Verrierwithout leaving his study, without even looking at the skyhad found the unknown planet

[Neptune] solely by mathematical calculation, and, as it were, touched it with the tip of his pen!

Franois Arago, France, 1846

Nicolaus Copernicus De revolutionibus orbium coelestium, 1543 First to propose heliocentric (sun) model

for universe

Galileo Galilei Father of modern astronomy Made significant advances to telescope Recorded phases of Venus Discovered 4 moons of Jupiter Controversially advocated for

heliocentricsm; jailed by the inquisition

Johannes Kepler Laws of planetary motion, 1621 Stated that the orbit of a planet is an

ellipse with the Sun at one of the two foci.

Isaac Newton Philosophi Naturalis Principia Mathematica, 1687 Laid foundation for classical mechanics Outlined law of universal gravitation:

Any two bodies in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them

Sir William Herschel Observed Uranus on March 13, 1781 Noted its movement; initially reported it

to be a comet Within the year, circular orbit had been

identified and it was noted to be a planet

Uranus Apparent Magnitude: 5.9 to 5.32 Orbital period: 84.0 years Aphelion: 20.09 AU Perihelion: 18.28 AU Equatorial radius: 4.01 earths Moons: Numerous Ice giant, with more ices (water, ammonia,

methane in its atmosphere than S/J) Coldest planetary atmosphere in the

solar system (minimum temperature of 49 K)

Aberrations in Uranus Orbit

Discovery of Neptune September 23-24, 1846 Urbain Le Verriers work predicted

position of new planet Johann Galle found new planet within 1

degree of predicted position Dramatic confirmation of Newtonian

gravitational theory

Neptune Apparent Magnitude: 8.02 to 7.78 Orbital period: 165 years Aphelion: 30.33 Perihelion: 29.8 Equatorial radius: 3.9 Earths Moons: 14 Densest of gas giants (also known as an

ice giant)

But what about pluto?

There goes the neighborhood

Eris was discovered in January 2005 and found to be 27% more massive than Pluto.

Estimated number of dwarf planets in our solar system:

>10,000

PART III: EXOPLANETS[I]f our solar system is not unusual, then there are so many planets in the universe that, for

example, they outnumber the sum of all sounds and words ever uttered by every human who has ever lived. To declare that Earth must be the only

planet with life in the universe would be inexcusably bigheaded of us.

Neil deGrasse Tyson

Radial Velocity Detecting minor orbit of star caused by orbiting planet

Transit Detecting decrease in light when planet transits in front of star

Direct Imaging Only possible for large planets that are far away from dim stars

Gravitational Lensing Detecting minor changes in light from source star from lensing planet

Timing variations Orbiting planets cause changes in periodic phenomena

2M1207

TrEs-3b Orbits the star GSC 03089-00929 Has an orbital period of just 31 hours;

undergoing orbital decay Has nearly twice the mass of Jupiter Found with transiting survey; mass

confirmed with radial velocity measurements of host star

TrEs-3b (artists interpretation)Jupiter (really)

Kepler Mission Launched March 7, 2009 Spacecraft equipped with photometer to find transiting planets

Studies 145,000 stars in a fixed position in the Milky Way

Kepler-20f Closest radius to Earth of any

exoplanet discovered Surface temperature is 705K

(a little too hot for liquid water)

(still just an artists interpretation)

Estimated number of solar systems in our galaxy:

>100 Billion