comets comets hale-bopp and the andromeda galaxy
TRANSCRIPT
CometsComets
Comets
Hale-Bopp and the Andromeda galaxy
Comet miscellaneousComet miscellaneous
Discovered as faint, fuzzy patchesDiscovered as faint, fuzzy patches Travel in highly elliptical orbitsTravel in highly elliptical orbits Brightens and develops a tail as it Brightens and develops a tail as it
nears the Sunnears the Sun Emit no visible light of their ownEmit no visible light of their own A few dozen are discovered each A few dozen are discovered each
year, more go by unnoticedyear, more go by unnoticed
Comet miscellaneousComet miscellaneous
They are essentially ice left over They are essentially ice left over from the formation of the gas from the formation of the gas giantsgiants
Are named after their discoverers Are named after their discoverers – the first 2 people to report it– the first 2 people to report it
About half of all discoveries are by About half of all discoveries are by amateur astronomersamateur astronomers
The name comet comes from the The name comet comes from the Greek word Greek word kometeskometes, meaning , meaning “wearing long hair”“wearing long hair”
This comet appeared to pass in front of the Ring Nebula
An earlier view
Parts of a CometParts of a Comet
Nucleus: main solid bodyNucleus: main solid body– Typically only a few kilometers wideTypically only a few kilometers wide– The only part that remains when the The only part that remains when the
comet is far away from the suncomet is far away from the sun Coma: the halo around the nucleusComa: the halo around the nucleus
– Forms and becomes larger as the Forms and becomes larger as the comet comes toward the suncomet comes toward the sun
– Can become almost as large as Can become almost as large as Jupiter or SaturnJupiter or Saturn
Parts of a CometParts of a Comet
Hydrogen envelope: Surrounds Hydrogen envelope: Surrounds the cometthe comet– Invisible, stretches millions of km in Invisible, stretches millions of km in
spacespace Ion tail: straight, makes glowing Ion tail: straight, makes glowing
linear streamerslinear streamers Dust tail: broad and gently curvedDust tail: broad and gently curved
– Rich in dust that reflects sunlightRich in dust that reflects sunlight
Comets tails, cont.Comets tails, cont.
Always point away from the sun, Always point away from the sun, due to solar wind due to solar wind
Lies outside the comets orbitLies outside the comets orbit Is in front of the comet, once it Is in front of the comet, once it
goes around the sungoes around the sun
This picture of Hale-Bopp shows the white dust tail and the blue ion tail
Dust and ion tails of Comet NEAT
Physical PropertiesPhysical Properties
Its mass decreases with time (it Its mass decreases with time (it loses material as it goes around loses material as it goes around the sun)the sun)
Made of dust particles, methane, Made of dust particles, methane, ammonia, carbon monoxide, and ammonia, carbon monoxide, and water icewater ice
Long Period CometsLong Period Comets
Comets may go as far as 50,000 Comets may go as far as 50,000 A.U. from the sunA.U. from the sun
With very elliptical orbits, they slow With very elliptical orbits, they slow down, according to Kepler’s 2down, according to Kepler’s 2ndnd law law
Most take hundreds of thousands Most take hundreds of thousands (maybe millions) of years to (maybe millions) of years to complete an orbit. complete an orbit.
May be part of a huge cloud (Oort May be part of a huge cloud (Oort Cloud) orbiting far from the sunCloud) orbiting far from the sun
How many comets do you see?
Comet Bradford is to the left and Comet LINEAR to the right.
Short Period CometsShort Period Comets
Fewer in numberFewer in number Have orbital periods of less than Have orbital periods of less than
200 years200 years Do not venture far beyond the Do not venture far beyond the
orbit of Plutoorbit of Pluto Originate in the Kuiper beltOriginate in the Kuiper belt
Short v’s Long Period Short v’s Long Period CometsComets Short period comets orbit in Short period comets orbit in
roughly the same plane as the roughly the same plane as the planets (ecliptic)planets (ecliptic)
Long period comets orbit in all Long period comets orbit in all directionsdirections
Comet Encke returns every 3.3 years. Its orbit goes just outside of Mars and back!
Halley’s CometHalley’s Comet
British astronomer Edmund Halley British astronomer Edmund Halley realized that a comet seen in 1682 realized that a comet seen in 1682 was not a one time event.was not a one time event.
He calculated its path and found He calculated its path and found that it had an orbital period of 76 that it had an orbital period of 76 yearsyears
He predicted that it would He predicted that it would reappear in 1758reappear in 1758
He did not live to see it, but he He did not live to see it, but he was correctwas correct
Halley’s CometHalley’s Comet
Ancient cultures record Halley’s Ancient cultures record Halley’s comet in every pass since 240 B.C.comet in every pass since 240 B.C.
Was photographed in 1910 and Was photographed in 1910 and again in 1986again in 1986
In 1986, a Soviet craft, Vega 2, In 1986, a Soviet craft, Vega 2, traveled through its coma and was traveled through its coma and was only 8000 km away from its nucleusonly 8000 km away from its nucleus
Halley’s CometHalley’s Comet
A European spacecraft, Giotto, A European spacecraft, Giotto, came within 600 km of its nucleus came within 600 km of its nucleus to take picturesto take pictures
Found that the nucleus was Found that the nucleus was potato shaped (15 km x 10 km) potato shaped (15 km x 10 km) and is almost blackand is almost black
Will next be near us in 2061Will next be near us in 2061 When it passed in 837 AD, it was When it passed in 837 AD, it was
as bright as the crescent moonas bright as the crescent moon
Comet Halley’s nucleus
Hale-BoppHale-Bopp
Biggest comet to visit the solar Biggest comet to visit the solar system in more than 200 yearssystem in more than 200 years
Was visible to the naked eye for Was visible to the naked eye for more than a yearmore than a year
Will return…in 2,380 years…Will return…in 2,380 years…sorry!sorry!
Comet Hale-Bopp early after its discovery
Comet Shoemaker-Comet Shoemaker-Levy 9Levy 9 Discovered in 1993 orbiting Discovered in 1993 orbiting
JupiterJupiter Jupiter’s gravity ripped it into 21 Jupiter’s gravity ripped it into 21
piecespieces These pieces crashed into Jupiter These pieces crashed into Jupiter
a year latera year later
Shoemaker-Levy 9 impacting Jupiter
Comet Ikeya-Shang and the Northern Lights!
Comet Hyakutake and a cactus
Comet McNaught – 2007
Comet Holmes – Fall 2008
2010 – Comet Hartley2 and the Perseus Double Star Cluster