Ad: "Black Holes in the Universe"
The next seminar of the Balseiro Institute in Bariloche Atomic Centre will be delivered by Dr. Felix Mirabel.
Saturday, October 31, 2009
Dr. Mirabel is senior researcher at CONICET, having received his Ph.D. in astrophysics from the University of La Plata, and one in philosophy from the University of Buenos Aires. For his discoveries and research in the area of \u200b\u200bblack holes has received several distinctions, including Doctorate Honoris Causa from the University of Barcelona, \u200b\u200bthe Bruno Rossi Prize for High Energy Astrophysics of the Astronomical Association of North America, and the Scientific Award of the Atomic Energy Commission of France. He has authored nearly 500 publications and has participated in the discovery of numerous novel astronomical phenomena, such as microcuásars, superluminal motion in the Galaxy, ultraluminous infrared galaxies and tidal dwarf galaxies. Service is a member of Astrophysics Atomic Energy Commission of France, and the prestigious European Observatory of the Southern Hemisphere and has been the leading representative in Chile for several years.
Friday November 6, 2009, 1430 Bariloche Atomic Center
Felix Mirabel
Institute of Astronomy and Space Physics, Buenos Aires
Summary: Black holes are the most enigmatic objects in astrophysics. Its gravitational pull is so intense that no light leak, staying dark. For more than two centuries its existence was cause of mere speculation, but for two decades convincing evidence has accumulated on the existence of two types of black holes in the universe: 1) as corpses of massive stars that cosmic dance devour stars produce light, and 2) as objects more individual mass of the universe, with masses equivalent to millions of stars, concentrated in regions as small as the solar system. We will review the properties of cosmic objects and their role in the evolution of the universe, according to recent research in the world's most advanced observatories. Demonstrate its effects with images and animations, reaching key conclusions about our knowledge of the cosmos. 
Sunday, October 25, 2009
Is Keri Hilsons Hair A Weave
a planet's surface temperature, surface temperature
comes the end of our trilogy on the orbital temperature. In the first part
calculate In this third part (last !) the equilibrium temperature. We have already determined that every second the earth receives $ 1.74 \\ times 10 ^ {17} $ J. What does the Earth with this energy? In short, it is heated. And we know that a hot body radiates energy according to the Stefan-Boltzmann (radiated energy increases with the fourth power of the temperature!). Suppose that the Earth has a temperature $ T_ \\ Oplus $ and behaves as a black body (a more reasonable assumption at this level), then the power radiated into space (usually using the letter $ L $ per light) is:
where $ \\ sigma $ is the constant Stefan-Boltzmann and $ \\ left (4 \\ pi R_ \\ Oplus ^ 2 \\ right) $ is the Earth's surface (here we consider the total surface of the Earth and not only its cross section as in the case of the energy absorbed .)
The equilibrium occurs when the energy absorbed is equal to the radiated energy. If there is an imbalance, the parameters are adjusted so as to reach a new condition. Suppose for example that for some reason increases the solar luminosity $ L_ \\ odot $. In this case, the energy that Earth receives will be greater and this leads to an increase in temperature, which implies an increase in the radiated energy. This equilibrium condition is therefore stable. Then:
\\ [E_ {abs} = E_ {emit} \\]
remember the expression for $ E_ {abs} $ obtained in the first part
and since brightness is energy per unit time,
\\ [L_ {abs} = \\ frac {L_ \\ odot} {4} \\ left (\\ frac {R_ \\ Oplus} {R_ {UA} \\ right) ^ 2} \\]
Therefore, our equilibrium condition occurs when:
\\ [L_ {abs} = L_ {emit} \\]
\\ [ \\ frac {L_ \\ odot} {4} \\ left (\\ frac {R_ \\ Oplus} {R_ {UA} \\ right) ^ 2} = \\ Left (4 \\ pi R_ \\ Oplus ^ 2 \\ right) \\ sigma T_ \\ Oplus ^ 4 \\]
and then clearing the temperature $ T_ \\ Oplus $ we have:
\\ [T_ \\ Oplus = \\ sqrt [4] {\\ frac {L_ \\ odot} {16 \\ pi \\ sigma} \\ frac {1} {R_ {UA} ^ 2}} \\]
Before numbers forward some conclusions:
The temperature is independent of the size of the planet (note that $ R_ \\ $ Oplus canceled) increases with the fourth root of the solar luminosity, and decreases with square root distance. 
The equation is valid for any star-planet system, and is used inter alia to determine the "
\\ [T_ \\ Oplus = \\ sqrt [4] {\\ frac {3.85 \\ times 10 ^ {26} \\ mathrm {W}} {(16 \\ pi) (5.67 \\ times 10 ^ {-8} \\ mathrm {W} \\ mathrm {m} ^ {-2} \\ mathrm {K} ^ {-4}) (1.5 \\ times 10 ^ {11} \\ mathrm {m}) ^ 2}} \\] \\ [T_ \\ Oplus = 278 \\ mathrm {K} = 5 ^ \\ mathrm {o} \\ mathrm {C} \\]
comes the end of our trilogy on the orbital temperature. In the first part
, we calculate the solar energy that Earth receives, and the second part
, which would estimate the temperature of the Earth if the Sun was not where $ \\ sigma $ is the constant Stefan-Boltzmann and $ \\ left (4 \\ pi R_ \\ Oplus ^ 2 \\ right) $ is the Earth's surface (here we consider the total surface of the Earth and not only its cross section as in the case of the energy absorbed .)
The equilibrium occurs when the energy absorbed is equal to the radiated energy. If there is an imbalance, the parameters are adjusted so as to reach a new condition. Suppose for example that for some reason increases the solar luminosity $ L_ \\ odot $. In this case, the energy that Earth receives will be greater and this leads to an increase in temperature, which implies an increase in the radiated energy. This equilibrium condition is therefore stable. Then:
\\ [E_ {abs} = E_ {emit} \\]
remember the expression for $ E_ {abs} $ obtained in the first part
:
\\ [E_ {abs} = \\ frac {L_ \\ odot t} {4} \\ left (\\ frac {R_ \\ Oplus} {R_ {UA} \\ right) ^ 2} \\]
and since brightness is energy per unit time,
\\ [L_ {abs} = \\ frac {L_ \\ odot} {4} \\ left (\\ frac {R_ \\ Oplus} {R_ {UA} \\ right) ^ 2} \\]
Therefore, our equilibrium condition occurs when:
\\ [L_ {abs} = L_ {emit} \\]
\\ [ \\ frac {L_ \\ odot} {4} \\ left (\\ frac {R_ \\ Oplus} {R_ {UA} \\ right) ^ 2} = \\ Left (4 \\ pi R_ \\ Oplus ^ 2 \\ right) \\ sigma T_ \\ Oplus ^ 4 \\]
and then clearing the temperature $ T_ \\ Oplus $ we have:
\\ [T_ \\ Oplus = \\ sqrt [4] {\\ frac {L_ \\ odot} {16 \\ pi \\ sigma} \\ frac {1} {R_ {UA} ^ 2}} \\]
The temperature is independent of the size of the planet (note that $ R_ \\ $ Oplus canceled)
The equation is valid for any star-planet system, and is used inter alia to determine the "\\ [T_ \\ Oplus = \\ sqrt [4] {\\ frac {3.85 \\ times 10 ^ {26} \\ mathrm {W}} {(16 \\ pi) (5.67 \\ times 10 ^ {-8} \\ mathrm {W} \\ mathrm {m} ^ {-2} \\ mathrm {K} ^ {-4}) (1.5 \\ times 10 ^ {11} \\ mathrm {m}) ^ 2}} \\]
more impressive results, is not it?
Thursday, October 22, 2009
Franklin Mint Vase Butterflies
3rd part of a planet, part 2
say that sequels are never good, but we will make the attempt ...
In the first part say that sequels are never good, but we will make the attempt ...
calculate the amount of energy the Earth receives from the sun But what about that energy? In a nutshell, is used to warm the Earth. Which brings us to another question before continuing: What temperature is the empty space? 
course to answer this question we must first define what it means "Empty space." Strictly speaking, the empty space there. And for various reasons: cosmology, quantum and relativistic. Re-ask: At what temperature is a region of space with no stars or other energy sources nearby?
(yes, as the oven!), Which extend in the electromagnetic spectrum between 300 MHz and 300 GHz
Alpher and R.
Hermann
, and was discovered (by accident) in 1965 by Hermann
A. Penzias and R. Wilson (Nobel Prize winners in 1978 for this work) is actually a relic of the Big Bang to the time when the universe became transparent to radiation, or put another way, when finally electrons and photons allowed to interact and electrons began to form atoms with the baryons. From that moment (about 300,000 years after the Big Bang), the photons propagate through the expanding Universe with almost no interaction (the current density is 410 photons per cubic cm.)
And since the universe expands adiabatically (by definition, the universe is a closed system), the temperature of this background radiation decreases as time progresses. The current temperature of the background radiation was measured with extreme accuracy (parts per million) and is 2.725 K, and its distribution corresponds to that of a black body at that temperature.
We finally have our answer: if the sun suddenly disappeared, and if the Earth had no nuclear processes inside, the temperature of the Earth gradually fall to reach thermal equilibrium with the background, about 2.7 K (about -270 ° C).
continued ...
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