Transcript "Asteroids attack the Earth – myth, speculation, or real danger?"

Asteroids attack the Earth – myth,
speculation, or real danger?
Ruslana Glazman, Sharet school/ASTROTOP, Netanya, Israel
Main questions in the project:
• How do we find asteroids in the sky?
• How do we estimate the orbit of discovered asteroids?
• What are asteroids and comets, and what is the
difference between them?
• Where do asteroids live? Do they live in the same area as
comets? How do they arrive here?
• What is the probability that an asteroid impact will
cause a disaster in the very near future? Is the
probability different depending on the amplitude of the
catastrophe (affecting a region, country, or the whole
planet)?
• When was the last accident caused by asteroid or comet?
Asteroids: How to find asteroids in the sky?
Data sources.
• Method - permanent survey of a sky region by numerous groups
in the world: NEO – Near Earth Objects search.
• Sources of my observational matter: Eudoxos Obs., Cephalonia,
Greece: D-Space network of robotic telescope (1) ; Wise Obs.,
Mitspe Ramon, Israel, with David Polischuk (2)
(1)
(2)
Asteroids: How do we find asteroids in the sky?
Data analysis and identification of objects.
EUDOXUS (D-Space) – Asteroid 2017
Mitspe Ramon – NEO search ( 3 clicks)
How do we estimate the orbit of
discovered asteroids or comets?
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Orbit is an ellipse
Parameters: a, b, i, ω,  a 2  b 2
ε
Eccentricity:
a
Aphelion = farthest distance = Ra,
Perihelion = nearest distance = q = Rp
Observing the asteroid over time in
several positions gives the parameters
of its orbit:
α1,δ1,t1
α2,δ2,t2
α3,δ3,t3
………..
αn,δn,tn
 
a
b
i
ω
Ω
Ra
1
2
3
4
What are asteroids and comets, and
what are differences between them?
• Asteroids are stones (up to
1000 km). Asteroids have no
tails. Meteorites are asteroids,
falling to Earth. Their chemical
contents are carbonaceous
chondrite (~93%), iron (4%).
• Comets are lumps of ice and
frozen snow, covered by dark
dirty spots of dust. The dark
spots heat up when near the
Sun, eject gas and dust, and
form tails (two tails of dust and
gas, separated by the pressure
of solar wind)
Where do asteroids live? Do they
live in the same area as comets?
• We studied the distribution of all asteroids and comets by distance (a) ,
inclination to ecliptic (i), and eccentricity (ε)
(source: http://ssd.jpl.nasa.gov/?sb_elem, “Small-Body Orbital Elements”, catalog of Jet
Propulsion Laboratory, NASA & CALTECH)
Examples:
Num
Name
Asteroids
a (AU)
i (˚)
Comets
e
Num Name
Epoch
q (AU)–
perihelion
e
i (˚)
0.96
18.9
0.18
1
P/Halley
46480
0.59
0.04
162.2
Ra-Shalom
0.832
15.7
0.43
2
P/Encke
52560
0.34
0.12
11.77
2340
Hathor
0.843
5.85
0.44
4
P/Faye
51320
1.66
0.14
9.05
5381
Sekhmet
0.94
48.9
0.29
6
P/d'Arrest
52320
1.35
0.14
19.50
3554
Amun
0.97
23.3
0.28
7
P/PonsWinnecke
52640
1.26
0.15
22.28
5590
1990 VA
0.98
14.1
0.27
8
P/Tuttle
49520
1.00
0.17
54.69
9
P/Tempel 1
51920
1.50
0.18
10.54
2062
Aten
2100
10563
Izhdubar
1.00
63.4
0.26
Where do asteroids live? Do they
live in the same area as comets?
Conclusions:
1. Orbits of asteroids are localized in belts. Main belt - between
Mars and Jupiter in interval between 2 AU and3.5 AU.
Secondary narrow belt is on Jupiter’s radius 5 AU – “Jupiter
Trojans”. Scattered external belt is on the same distance as
Pluto (Kuiper belt) – is Pluto one of them?
2. The asteroid orbits in the main belt are near ecliptic plane
with low inclination (i<30) and are circle-like (low eccentricity).
3. The main belt is fragmented on its inner side and splits
(possible result of resonance with gravitational disturbances of
planets and proper instability of the asteroid’s belt).
4. Inner asteroids (Near Earth) are rare and are scattered
randomly in space from Venus to the Main belt (where they are
ejected from the Main Belt as a result of collisions).
5. Comet’s orbits are divided in two groups:
– External comets up to thousands AU with high eccentricity
and high inclination (“hedgehog” distribution) – “Oort cloud”
– Inner comets with perihelion > 4 AU with low eccentricity
and inclination (“disc” distribution) like the asteroids
These locations originate from a sequence of
different stages in the Solar System’s origin
from a primary gas-dust cloud to its present
state
Location of planets and asteroids and the law of TitiusBode
1. The law of Titius Bode explains the range of
distances between the Sun and the planets:
Dn ( AU )  0.4  0.3 * 2 n with n  -, 1,2,3,...
•Explanation – resonance orbits, stable opposite
to gravitational disturbances
N=- – Mercury, N=1 – Venus, N=2 – Earth
N=3 – Mars, N=5 –Jupiter, N=6 – Saturn
N=7 – Uranus, N=8 – Pluto, N=9 – Sedna
Main Asteroid Belt is in position n=4 exactly.
2. What is it – remnant from former planet’s explosion
(Phaeton) or primary blocks for future planet building?
3. Now, astronomers reject Phaeton’s hypothesis
(deficit summary mass, chemical content of meteorites,
Jupiter influence).
Answer – asteroids and comets are “junk” of
primary matter, remained after construction
of the solar system.
What is the probability to have a disaster
from asteroid impact in the near future?
• Data for analysis comes from craters from past impacts. Source of data: database
of asteroid craters identified on Earth:
http://www.unb.ca/passc/ImpactDatabase/CIDiameterSort2.htm
Asteroid impact and its sequences
1. Velocity of asteroid in collision– 10-20 km/sec
2. Energy of explosion comes from the kinetic energy of a
stopped asteroid = mV2/2. Correspondent energy of
explosion convert to:
–
–
–
–
Heating and evaporation of the asteroid/comet matter
(chondrites / ice)
Emission of overheated gas
Shock wave and mass ejection into atmosphere and
space
Plastic deformation of the Earth matter with earth
quakes and strong seismic waves
Distribution of impact craters
by amplitude and ages
Planetary Catastrophe events (craters about 100
His to ry o f imac ts (0 - 3 miliards ye ars )
400
300
200
100
0
0
100
200
300
400
500
age in m illions years
km -
disaster region 10,000 km)
Power: Million Megaton TNT
The largest crater - 800 km, 3 million years - Africa.
Another example- 300 km, 65 million years, Chicxulub, Mexico Dinosaur’s killer (?)
The last event - million years ago – Sweden – 130 km
Mean time interval – 50-100 million years
History of imacts (0-100 millions year)
50
Regional Catastrophe events (craters about 10 km, disaster
diameter in km
40
30
20
10
0
0
10
20
30
40
50
60
70
80
90
100
region 100-1000 km)
Power: Million Megaton TNT
The last event – 13,000 years ago – Iraq
Mean time interval –1-3 million years
age in millions years
diameter in km
History of imacts (0-10,000 years)
0.500
0.400
0.300
0.200
0.100
0.000
Local Catastrophe events (craters 100 m - 1 km, disaster
0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010
age in millions years
regions - ten kilometers)
Power: 100-1000 Megaton TNT
The last event – 100 years ago – Siberia, Tunguska (atmospheric
explosion with disaster region - 40 km)
Mean time interval - about thousands years
Conclusions
• Asteroids and comets are stone and ice remnants of building
junk from the period of the solar system construction.
• They are situated in belts and clouds.
• A small part of them were scattered from their belt as a result
of a collision with another one and entered Earth orbit.
• A small part of these guests has the probability to collide with
the Earth.
• Possible impact may be from Planetary catastrophe (one in tens
millions of years), regional catastrophe (one in a few millions of
years, and local catastrophe (one in a thousand – tens thousands of
years)
• Last local event was in 1908 in empty region in the East Siberia,
“Tunguska”. Region of destruction – 40 km. Now more then
30,000 people live in this region (!). Where can we find a place for
the next impact with minimum negative sequences?
• Asteroid attack is real source of danger for a period of
thousand years.
Who is waited to be the next visitor?
•NEO – Near Earth Objects program = permanent
monitoring of the all sky by network of telescopes for
timely discovery and identification of potentially
dangerous asteroids/comets
•Apophis = 2004 MN4: size 400 m, disasters region = 100
kilometers, expected probability of impact = 1/1000 years
It was discovered June 19, 2004 as a near-Earth asteroid that
caused a brief period of concern in December 2004 because
initial observations indicated a large probability that it would
strike the Earth in 2029 (3%) = class 4 in Torino Scale of
Impact hazards. Later (2006) orbit was calculated more
exactly and possibility of impact in this transition was
excluded (minimal distance about 30,000 km = just below
the altitude of geosynchronous satellites (!!!), but without
capture.
•Data of the next transition is April 13, 2029, Apophis will
be observed by naked eye.
•Gravitational disturbances of Apophis orbit during transition
near the Earth may shift it in new orbit with high probability
of the impact. Next transition in 2036 may be dangerous.
Apophis in Mitspe Ramon observation
[David Polischuk (2004)]
?
?
One from the possible scenarios of impact
catastrophe from “Deep Impact” (God forbid !!!)