Download Other Interesting Aspects of Astronomy

Other Interesting
Aspects of Astronomy
I. Formation of the Earth
• Around 4.7 billion years ago, a young nebula
in the middle of a Milky Way spiral arm
existed
• Nebulae are full of gas and dust, the
birthplace of stars
• A large clump of gas and dust coalesced in the
nebula and accreted more mass over time
• It began spinning, and pulled some matter
around it in a disk
Formation of the Earth
• The matter in the disk began accreting into
clumps
• Very large clumps attracted a lot of matter to
them and gained mass
• They became planets
• Less successful (smaller objects) included comets
and asteroids
• Eventually, as most of the mass went to the sun,
it spun up even faster and the objects in the disk
sped up and rotated too quickly for mass to
accrete. Then, collisions and ejection occurred.
Formation of the Earth
• The Earth became one of the inner (terrestrial)
planets that escaped ejection
• It formed around 4.6 billion years ago
• We estimate its age from meteorites, which are
largely unchanged from formation, as plate
tectonics on the Earth destroy most older rocks
• The Early earth was molten, with hydrogen and
helium in its atmosphere
• Moon formed by a Mars-sized object (“Theia”)
hitting earth 4.5 billion years ago and flinging a
lot of the mantle into space
Formation of the Earth
• The Earth had cooled since its formation and was
able to develop oceans beginning during the
heavy bombardment (3.8 – 4.1 billion years ago)
• Lighter gases (hydrogen and helium) had already
escaped Earth’s gravity and were lost to space
• Water vapor in the atmosphere from volcanic
outgassing and water vapor coming from asteroid
and comet impacts condensed in the atmosphere
• It precipitated very heavily and eventually the
Earth had oceans
II. Earth is Unique
• Basically, Earth has kept water in three phases (not
too hot like Venus or too small to keep it like Mars)
for most of the past 4 billion years, particularly
most of the past 1.5 billion years
• The sun is a single, very stable star, with a long life
• The moon has helped stabilize Earth’s axial tilt,
which greatly reduces climate fluctuations
• Jupiter is at just the right distance to deflect the
vast majority of comets and asteroids from earthapproaching orbits, and no gas giants have made it
more dangerous since the period of heavy
bombardment, and Jupiter is far enough that it
doesn’t disrupt Earth’s orbit
Earth is Unique
• Water can dissolve organic (carbon-based) compounds,
necessary for life
• Water has one of the highest specific heats of any
known substance and also high value of latent heat, and
this stabilizes climate
• Liquid water expands as it cools (rare occurrence), which
greatly reduces the speed of freezing
• Carbonic molecules can dissolve or stay intact in a water
solution; carbon can create covalent bonds with many
nonmetals, and, with water, can form carbohydrates,
import for other biochemical reactions
• No one has been able to think of a substance which can
support life nearly as well as water
Earth is Unique
• We are situated in a relatively calm part of the galaxy, with
minimal violence subjecting Earth from outside sources
• No nearby supernovae or close solar-system directed ray
bursts have roasted our planet for at least 4 billion years
• As such, the Earth has had an incredibly ideal period for
producing carbon-based life the past 4 billion years
• Massive enough planet to retain atmosphere and for iron and
heavy metals needed for skeletal structure and
support/protection of head and large brains
• Earth was able to store carbon dioxide in rocks, while
sufficient plants allow for adequate oxygen and ozone
production needed for cellular respiration
• We do not know exactly how rare Earth’s situation is in the
universe.
Earth is Unique
• In addition, assuming that life would try to occur
in any halfway conducive environment (big
assumption), evolution does not necessarily have
a “goal” regarding what type of life it creates
• Survival of the fittest does not mean that
intelligent beings capable of manual dexterity
(ability to use hands) to form technology is a goal;
there are a lot of intelligent vertebrates, and
remember vertebrate life is EXTREMELY fragile
• So, if life does exist on other planets (probably
quite likely), they are not necessarily beings able
to ponder and think in an objective, rational,
moral, transcendent manner and also utilize tools
for advanced technology
III. The Drake Equation
• The past few decades, attempts have been made to
quantify the likelihood of life with technology, such
as ourselves, capable of contacting other planets, or
being detected
• N = R x Fp x Ne x Fl x Fi x Fc x L
• N = number of civilizations in Milky Way that are capable of
communicating
• R = average rate of star formation in the Milky Way
• Fp = fraction of stars with planets
• Ne = average number of planets with potential to support
life per star having planets (Fp)
• Fl = Fraction of Ne that develop life
• Fi = Fraction of Fl that develop intelligent life
• Fc = Fraction of Fl that can release signals of their life into
space
• L = length of time Fc actually release such signals
wikipedia.org
The Drake equation
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•
•
•
•
•
•
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N = R x Fp x Ne x Fl x Fi x Fc x L
R ~ 10 stars per year formed in our galaxy
Fp ~ 0.5 ? (half of stars will have planets)
Ne ~ ?? (0.1?) planets capable for life
Fl ~ 0.5? Capable planets that develop life
Fi ~ ???? Life becomes intelligent (very small)
Fc ~ ???? Life able to communicate (very small)
L ~ 10,000 years (communication last for 10,000
years)
• Fc and especially Fi are probably tiny, just
that we don’t know how small (.001
each, or 1 x 10-12 each??)
wikipedia.org
What to take away
Beings with technological capabilities
similar to humans are a very rare
occurrence in the galaxy (and universe)
…It’s not what you see in science fiction!!
Most planets certainly do not have them
In fact, it may be possible that we are the only
such type of beings which exist on any planet
in the universe
IV. Meteor Showers
• Meteors are typically the size of sand grains
• They originate from comets and asteroids,
whose orbits happen to cross near Earth’s
orbit and have debris which burns into
atmosphere
• The small particles burn up in the ionosphere
and leave a brightly ionized trail that we see
• More particles earlier on in the solar system,
when it was a lot messier
Meteor Showers
• Favor Northern Hemisphere currently by
chance
• Most activity from mid-October through the
first week of January
• Interference of clouds or moon can be ruinous
• Particularly intense displays (> 1000/hour) are
called meteor storms– rare & incredible
Meteor Showers
• Meteors visible every clear night
• Sporadic meteors from random sources and
meteors from distinct sources
• Consistent high rates of meteors from distinct
sources create the most popular meteor
showers
• Meteor showers have meteoroids with
different ages, orbital periods, brightness
distributions, rates, angles of hitting earth,
speeds, mass distributions, total durations
Meteor Showers
Shower name
Peak dates
Peak Rate
Brightness
Ever storm?
Quadrantids
Jan 3
~120/hr
Bright
No
Lyrids
Apr 22
~15/hr
Faint
Barely
Eta Aquarids
May 4-6
~60/hr
Bright
None recorded
Southern Delta Aquarids
July 27-30
~18/hr
Faint
No
Perseids
Aug 12
~100/hr
Bright
Unsure- may later
Draconids
Oct 8
~2/hr median
Faint
Yes
Orionids
Oct 20-22
~25/hr
Average
No
Taurids
~Nov 3-10
~6/hr
Bright
No
Leonids
Nov 18
~20/hr median Varies a lot
Yes
Alpha Monocerotids
Nov 22
~2/hr median
Bright
Yes
Geminids
Dec 13
~130/hr
Bright
No
Ursids
Dec 22
~7/hr
Faint
Possibly
Combination of IMO rates, P. Jenniskens, E. Lyytinen, and my opinion
Meteor Shower
• To see a meteor shower well, get well away
from a city and its suburbs
• Do not want any clouds or moon in sky
(crescent moon is alright)
• Typically peak in darkness just before morning
twilight begins, when we are face-first in our
orbit
• Radiant must be high in order to see most of
meteors
Meteor Showers
• Best four overall for seeing lots of numbers in St
Louis area and Northern Hemisphere
midlatitudes are the Geminids, Perseids,
Quadrantids, and Orionids
• Geminid radiant is ideally placed in the sky and
the best bet of seeing a high rate
• Radiant is nearly overhead (maximum number of
meteors visible) and is highest well before dawn
• Also, a bright shower with fairly long maximum
V. Meteor Storms
• Some meteor showers can have intense outbursts
called meteor storms
• Most storms last typically 1/2 hour or so.
Occasionally longer-lived (Leonids and Draconids at
times). The center of a high density comet trail is
typically quite thin, so Earth plows through it quickly.
• The Leonids, Draconids, Alpha Monocerotids, and
Lyrids are all definitely capable. The June Bootids, Tau
Herculids, Ursids, and Aurigids may be. It is uncertain
whether the Sigma Ursids (next table) will evan
materialize in 2014 (and also possibly 2019).
• The Leonids and Draconids are the best known and
most consistent (frequent, regular) meteor showers
that produce meteor storms- at least for the past 100
to 200 years.
Possible upcoming meteor storms for
U.S. and Europe.
Shower
Dates
Likelihood
Where Visible
Moon Brightness
Sigma Ursids
5/24/2014
Uncertain
US
Fair
Bright
Draconids
10/9/2018
Doubtful
E US and W Atl
Good
Faint
Tau Herculids
5/30-31/2022 Maybe
US
Good
Bright
Draconids
10/8/2025
Doubtful
US and Pacific
Bad
Bright
Perseids
8/12/2028
Maybe
E US and W Atl
Bad
Faint
Leonids
11/18/2034
Good
Europe
Good
Faint
Leonids
11/19/2034
Maybe
Europe & E US
Good
Bright
Leonids
11/20/2035
Maybe
E Us and W Atl
Bad
Bright
Leonids
11/20/2035
Maybe
US
Bad
Bright
Leonids
11/20/2037
Good
Europe & Asia
Bad
Faint
A. Monocerotids
11/22/2043
Maybe
W. & Cent U.S.
Bad
Bright
June Bootids
6/22/2045
Maybe
W U.S.
Good
Very bright
Predictions based on P. Jenniskens, E. Lyytinen, J. Vaubaillon, M. Maslov, and S. Molau
Possible Future Meteor Storms
• Best Bets: 2034 Leonids (moonless) and 2037
Leonids
• Other decent chances: 2045 June Bootids
(moonless), 2022 Tau Herculids (moonless- this
one could be nothing or completely spectacular
or somewhere in between), 2035 Leonids, 2028
Perseids, and 2043 Alpha Monocerotids
• All in table worth a shot if you’re in the area
• Other storms possible, with some lesser
likelihood predictions (not shown) and unknown
sources the cause, the latter of which are
unfortunately not predictable at this time
Hope you enjoyed this special session!!