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cragwolf
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Oops, I didn't see this last page, Marcus. OK, Labguy is right, and can ask the next question.
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The object is a binary star pair, one partner being a neutron star. The other partner expands to the point where material from its outer layers can flow over and accrete onto the surface of the neutron star.
this process itself must release energy in various forms including xray, but this energy from the gradual buildup of material is not the "burst" people talk about.
The burst happens when a critical mass of hydrogen, in a thick enough layer, builds up on the surface of the neutron star. The hydrogen layer suddenly fuses into helium----a thermonuclear explosion involving the dense plasma "atmosphere" of the neutron star.
If I remember right, fusion at the sun's core makes
X-rays roughly 1000 eV and up because the temperature is 1000-plus eV. So that is what naked fusion yields (luckily for us, the energy gets softened as it percolates out to the sun's surface). So xray is to expected in this case, but with no surrounding material to buffer it.
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What figure is used for the "peak absolute magnitude" of a Type Ia supernova?
Briefly sketch the process leading up to a supernova of that type.
Why do they all have about the same luminosity----allowing them to be used as a standard candle for estimating distance?
Briefly sketch the process leading up to a supernova of that type.
Why do they all have about the same luminosity----allowing them to be used as a standard candle for estimating distance?
Science Advisor
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Peak absolute magnitude for a type Ia supernava is at the top (brightest) point on the light curve after the explosion. By number, it is defined as MIa= -19.5 (+/-)0.2 Mag.
A Type Ia supernova is from a binary star system consisting of a white dwarf with a red giant companion, where the white dwarf accretes enough material to place it above the "Chandra's Limit". When this happens, the total mass of the white dwarf collapses and all material explodes in a huge nuclear fusion process and the Type Ia supernava occurs, leaving no "stellar remnant" behind. IOW, there is no Neutron Star or Black Hole remnant. About 99% of the energy is emitted as neutrinos, but that still leaves enough for the huge amount of visable light that can be detected; brighter than any other class of supernova.
The luminosity of Type Ia Supernovae is always nearly equivalent because the process of the explosion, and the chemical composition of the White Dwarf, must always meet nearly identical conditions. Most texts will say that the limit is the famous 1.44 Solar Masses (Sm), but in fact, the limit reached by the White Dwarf is somewhat less at 1.38 Sm. This is because the process (explosion) is the result of "Carbon deflagration" which must propagate throughout the star at a speed near, but not above, the speed of sound in that medium. Not all accreting white dwarfs, in fact very few, meet these conditions of size and composition, so Type Ia Supernovae are very rare, but very much a consistent "standard candle"
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Pleased to say this told me more than I knew before about type Ia SN.
The figure of -19.5 was what I was looking for, plus the something about the process.
BTW since the sun is abs. magnitude 4.8 this must mean that the supernova at peak is 24-some steps of visual magnitude more luminous than the sun...
Anyway, your go, Labguy
The figure of -19.5 was what I was looking for, plus the something about the process.
BTW since the sun is abs. magnitude 4.8 this must mean that the supernova at peak is 24-some steps of visual magnitude more luminous than the sun...
Anyway, your go, Labguy
screwball
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In 1929 by E. Hubble. On the Mount Wilson Observatory? not sure...
screwball
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Originally posted by Labguy
(1) No.
(2) No.
(3) No.
Keep trying folks...
Hubble was wrong? the date too? ok
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I want to comment even though I have no guess about the answer. this is an interesting question because it does not mention the LINEAR RELATION between distance and redshift which Hubble discovered and is known for.
Hubble used cepheids (and luminosity of the whole galaxy) to estimate the distance. So he could plot an approximately linear relation. But someone else at some other observatory could have
previously discovered the redshift-----apparently according to Labguy they did----and simply not related it to distance in a pattern. Neat question because of the element of surprise.
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In 1922 the astronomer Vesto Slipher, at Lowell Observatory, published his findings about the redshifts of galaxies.
He had found that they are mostly redshifted rather
than blueshifted.
The first redshift measurement he made was in 1912, I
believe, and he eventually compiled a list of 41 extragalactic
objects nearly all of which were redshifted.
Slipher (1875-1969) was born in Indiana. A history of Lowell Observatory (Flagstaff Arizona) says that Vesto's middle name was Melvin, and that his measurements of the 41 extragalactic redshifts was from 1912 to 1917.
He became director of the Observatory in 1916 and helped to find Pluto.
He had found that they are mostly redshifted rather
than blueshifted.
The first redshift measurement he made was in 1912, I
believe, and he eventually compiled a list of 41 extragalactic
objects nearly all of which were redshifted.
Slipher (1875-1969) was born in Indiana. A history of Lowell Observatory (Flagstaff Arizona) says that Vesto's middle name was Melvin, and that his measurements of the 41 extragalactic redshifts was from 1912 to 1917.
He became director of the Observatory in 1916 and helped to find Pluto.
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screwball
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ok i looked it up and found this in one of my old high school astronomy books:
"In 1913 V. M. Slipher at Lowell Observatory reported on the spectra of faint, nebulous objects in the sky. Their spectra seemed to be composed of a mixture of stellar spectra: some had Doppler shifts that suggested rotation, most had red shifts as if they were receding, and the faintest had the largest red shifts. Within two decades, astronomers concluded that the faint objects were galaxies similar to our own Milky Way and that the galaxies are indeed receding from us in a general expansion."
that was a good question very interesting to realize Hubble wasnt the first to observe red shift but just the one to put it all together.
"In 1913 V. M. Slipher at Lowell Observatory reported on the spectra of faint, nebulous objects in the sky. Their spectra seemed to be composed of a mixture of stellar spectra: some had Doppler shifts that suggested rotation, most had red shifts as if they were receding, and the faintest had the largest red shifts. Within two decades, astronomers concluded that the faint objects were galaxies similar to our own Milky Way and that the galaxies are indeed receding from us in a general expansion."
that was a good question very interesting to realize Hubble wasnt the first to observe red shift but just the one to put it all together.
screwball
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lol u beat me to it
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A)What is the peak luminosity of a Type Ia supernova expressed as a wattage?
Don't count other ways the supernova might be releasing energy, like neutrinos, I guess that's implicit when one asks about the luminosity.
B)What is the luminosity of the sun expressed also expressed as a wattage?---the total output of light in all directions.
C)What is the approximate ratio of the two wattages? By what factor is a Ia SN brighter than the sun?
My handbook gives the sun's luminosity in ergs per second.
I'm asking for the answer in watts (one watt = 10^7 ergs per second) because that's more conventional although ergs still seem to be current in a good deal of astronomical writing.
Don't count other ways the supernova might be releasing energy, like neutrinos, I guess that's implicit when one asks about the luminosity.
B)What is the luminosity of the sun expressed also expressed as a wattage?---the total output of light in all directions.
C)What is the approximate ratio of the two wattages? By what factor is a Ia SN brighter than the sun?
My handbook gives the sun's luminosity in ergs per second.
I'm asking for the answer in watts (one watt = 10^7 ergs per second) because that's more conventional although ergs still seem to be current in a good deal of astronomical writing.
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Nobody else feels like answering this so I will. Labguy pointed out a few posts back that the peak Ia absolute magnitude is conventionally taken to be -19.5. And the sun's is 4.8. So the difference is 24.3. Multiplyby 2/5 and you get 9.72 (I will round off later).
C) The wattage ratio, SN versus sun, is 10^9.72 = 5.25 billion.
B) The sun's wattage (standard handbook figure) 3.8E26 watts.
A) Peak supernova luminosity is 5.25 billion times the sun's or
2E36 watts.
2 x 10^36 watts was what I was looking for in the answer.
Since I had to answer my own question the next askership is up for grabs.
The first person who can think of an appropriate-to-the-game type of question to which he/she knows the answer can ask it.
J-Man
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How nice, thanks.
If the Sun's orbital velocity around the center of the Milky Way is 220 km s-1 [220 km/sec], roughly how many orbits has it completed since it formed, 4.5 billion years ago? Explain how you arrived at your estimate. You may assume that the Sun's distance from the Galactic center is 8000 pc [parsecs], and that it is following a circular orbit.
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Too easy.
It's completed roughly 21 orbits in those 4.5 billion years.
The orbit length l = pi * 2 * 8000 pc.
Divide l (in km) by v = 6937920000 km/year to arrive at an orbit period of 222 million years.
Divide 4.5 billion by 222 million to arrive at roughly 21 orbits.
- Warren
It's completed roughly 21 orbits in those 4.5 billion years.
The orbit length l = pi * 2 * 8000 pc.
Divide l (in km) by v = 6937920000 km/year to arrive at an orbit period of 222 million years.
Divide 4.5 billion by 222 million to arrive at roughly 21 orbits.
- Warren
J-Man
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Sorry it took so long to get back...
But you are correct (I got between 20 and 21 orbits). Your turn.
Nicool003
hey guys! I was planning on coming back after vacation but there are tons of exams and tests and quizes and projects... well you can read all about it in general discussion
Anyways chroot it is your question.
Anyways chroot it is your question.
schwarzchildradius
Does chroot ask a question?
Nicool003
He seems to not be coming to this thread anymore so how about you ask schwartz? I don't want to take it because I haven't been able to come to PF as much as you guys so I haven't been to this thread in a while either.
schwarzchildradius
OK, how do you measure the distance to the moon using lunar eclipse? What other observation of the moon must be made to find the distance to the sun?
schwarzchildradius
BTW here's a freeware orrery and lunar eclipse predictor that works pretty well..
astropro orrery
astropro orrery