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Astronomy
#1
Third largest dwarf planet found.


Quote:“Astronomers have found that a previously overlooked rocky body that lies in the Kuiper belt beyond Neptune is far larger than previously thought, making it the third largest dwarf planet in our solar system, after Pluto and Eris”
http://iopscience.iop.org/article/10.384...ld.iop.org

"We present the first comprehensive thermal and rotational analysis of the second most distant trans-Neptunian object (TNOs) (225088) 2007 OR10. We combined optical light curves provided by the Kepler Space TelescopeK2 extended mission and thermal infrared data provided by the Herschel Space Observatory. We found that (225088) 2007 OR10 is likely to be larger and darker than derived by earlier studies”…
 … whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things. Phil 4:8 (ESV)
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#2
Noted just for fun.

Quote:http://www.space.com/32888-dying-stars-m...anets.html
“”When most stars reach old age and begin to run out fuel, they swell up to hundreds of times their normal size, engulfing planets that orbit too close. But can planets that escape this fiery demise still support life? In this state, can planets around the dying star host life? New research says yes.
In about 7.5 billion years, the sun will have begun its march to the grave and will start expanding. Eventually it will swell to about 200 times its current size. It will swallow Mercury and Venus, and make Earth uninhabitable. But currently frigid locations in the solar system, like the icy moons of Saturn and Jupiter, might become just the right temperature for life”…

…”There were other complicating factors that needed to be factored in, such as the fact that as the star loses mass, its gravitational grip on the planets is reduced. As a result, the orbit of a planet around a star will expand as the star becomes a red giant. (For this reason, the Earth will escape being engulfed by the sun, according to Kaltenegger).

Researchers have worked on the question of habitability around old stars before, but Kaltnenegger said no work has ever been done using models that can reveal details about how both the star and planets will evolve together through such a drastic change to the system.”…

- See more at: http://www.space.com/32888-dying-stars-m...iUQjC.dpuf
 … whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things. Phil 4:8 (ESV)
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#3
There's some controversy about whether the Earth would remain in existence or get pulled into the bloated-but-dying Sun. All orbits would move away from the Sun, but the expanding Sun would still catch up at the least with Mercury and Venus. The Earth is borderline on whether it would be consumed.

If the outermost layer of the solar atmosphere reaches the Earth, then frictional drag will pull what remains of the Earth. Volatile substances like water itself, sulfur, phosphorus compounds, and the carbon dioxide that gets released from rocks will have long gone. Silica will melt and evaporate and vanish with the solar wind, leaving the heavy, hot, iron-rich core with perhaps some metal oxides (calcium, magnesium, aluminum, and titaniaum oxides, largely) behind.

If frictional drag from the Sun's gases should get in the way of the Earth's core, then the Earth's core will spiral into the Sun. As it vaporizes it will be assimilated into the Sun and likely sink into the core of the Sun due to its density. Metal oxides will of course disintegrate, along with such refractory material as diamonds and graphite.
"The fool doth think he is wise, but the wise man knows himself to be a fool" -- William Shakespeare, As You Like It, V.i


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#4
(05-18-2016, 07:25 AM)pbrower2a Wrote: There's some controversy about whether the Earth would remain in existence or get pulled into the bloated-but-dying Sun. All orbits would move away from the Sun, but the expanding Sun would still catch up at the least with Mercury and Venus.  The Earth is borderline on whether it would be consumed.

If the outermost layer of the solar atmosphere reaches the Earth, then frictional drag will pull what remains of the Earth. Volatile substances like water itself, sulfur, phosphorus compounds, and the carbon dioxide that gets released from rocks will have long gone. Silica will melt and evaporate and vanish with the solar wind, leaving the heavy, hot, iron-rich core with perhaps some metal oxides (calcium, magnesium, aluminum, and titaniaum oxides, largely) behind.

If frictional drag from the Sun's gases should get in the way of the Earth's core, then the Earth's core will spiral into the Sun. As it vaporizes it will be assimilated into the Sun and likely sink into the core of the Sun due to its density. Metal oxides will of course  disintegrate, along with such refractory material as diamonds and graphite.

There are different views that are both controversial and probably irrelevant( not sure anyone will be around to observe). However this article presents a new model of what might happen that is interesting to me anyway.



Quote:... "Researchers have worked on the question of habitability around old stars before, but Kaltnenegger said no work has ever been done using models that can reveal details about how both the star and planets will evolve together through such a drastic change to the system. 

"This is the first time where we link the model of the star to the model of the planet and see what it does," she said. "The devil is really in the details. The first stabs at it were great work because the idea got started, but it's a lot of work to do, and [Ramirez] actually hunkered down and did it.""

- See more at: http://www.space.com/32888-dying-stars-m...xRRje.dpuf
 … whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things. Phil 4:8 (ESV)
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#5
One exoplanet, a "giant Jupiter" was discovered racing around its host star, trailing something resembling the tail of a comet. The stellar wind was apparently blasting away material from that planet, most likely from its outer and lightest layers. If Jupiter is any indication, then the first materials to blow away would be hydrogen, helium, and then the lighter hydrogen compounds like methane, ammonia, and water. Then -- it is your guess both on the composition of Jupiter and the chemistry of a dying planet. Such atmosphere as there is might offer some insulation, but it is clear: that planet doesn't have much of an existence left.

Nobody will be around long enough or close enough to see what happens. As the sun bloats the doomed Earth will itself get hot enough to radiate visible light (technically speaking, the Earth does radiate some electromagnetic radiation, and if some distant and intelligent civilization has its radiation detectors pointed at us it will find our planet anomalously hot due to radio waves from our broadcasts until it figures that there is information in those broadcasts, even if they are of Rush Limbaugh).
"The fool doth think he is wise, but the wise man knows himself to be a fool" -- William Shakespeare, As You Like It, V.i


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#6
Recent analysis on  history of our solar system.

How the sun abducted dwarf planets from an alien solar system

https://www.newscientist.com/article/mg2...ar-system/
The weird orbits of some bodies in the outer solar system reveal they are booty from an interstellar smash and grab raid, says astronomer Simon Portegies Zwart

… “not in the Kuiper belt or the Oort cloud, but in that mysterious gap between the two. The long-period comets are evidence that the orbits of smaller bodies in the Oort cloud are not static….Typically perturbed by the outermost giant planets, Uranus and Neptune, they adopt inclined, highly elliptical – “eccentric” – orbits that tend to end up in sync with the giants’ orbits.”…“Mike Brown of the California Institute of Technology in Pasadena and his team discovered the dwarf planet Sedna. …Sedna’s orbit is curious … It is very elongated”….

… “What emerges is a close brush between our solar system and that of a star almost twice as massive as the sun.  …For smaller bodies,the jolt was felt as far in as about 40 AU, ripping out any planetesimals beyond that point into interstellar space – in other words, producing the Kuiper cliff (Monthly Notices of the Royal Astronomical Society, vol 453, p 3157).”…"Apart from having reshaped the solar system’s outer regions, the simulations show that more than 2000 planetesimals orbiting the other star would have become bound to the young sun,”…about half ending up in orbits similar to that of Sedna.”…
 … whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things. Phil 4:8 (ESV)
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#7
(06-10-2016, 04:20 PM)radind Wrote: Recent analysis on  history of our solar system.

How the sun abducted dwarf planets from an alien solar system

https://www.newscientist.com/article/mg2...ar-system/
The weird orbits of some bodies in the outer solar system reveal they are booty from an interstellar smash and grab raid, says astronomer Simon Portegies Zwart

… “not in the Kuiper belt or the Oort cloud, but in that mysterious gap between the two. The long-period comets are evidence that the orbits of smaller bodies in the Oort cloud are not static….Typically perturbed by the outermost giant planets, Uranus and Neptune, they adopt inclined, highly elliptical – “eccentric” – orbits that tend to end up in sync with the giants’ orbits.”…“Mike Brown of the California Institute of Technology in Pasadena and his team discovered the dwarf planet Sedna. …Sedna’s orbit is curious … It is very elongated”….

… “What emerges is a close brush between our solar system and that of a star almost twice as massive as the sun.  …For smaller bodies,the jolt was felt as far in as about 40 AU, ripping out any planetesimals beyond that point into interstellar space – in other words, producing the Kuiper cliff (Monthly Notices of the Royal Astronomical Society, vol 453, p 3157).”…"Apart from having reshaped the solar system’s outer regions, the simulations show that more than 2000 planetesimals orbiting the other star would have become bound to the young sun,”…about half ending up in orbits similar to that of Sedna.”…

Paywall, again. Sad
#MakeTheDemocratsGreatAgain
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#8

.pdf   How the sun abducted dwarf planets from an alien solar system | New Scientist.pdf (Size: 1.74 MB / Downloads: 4)
pdf file
 … whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things. Phil 4:8 (ESV)
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#9
(06-11-2016, 10:34 AM)radind Wrote: pdf file

Thanks!
#MakeTheDemocratsGreatAgain
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#10
Yes, There Have Been Aliens

Quote:LAST month astronomers from the Kepler spacecraft team announced the discovery of 1,284 new planets, all orbiting stars outside our solar system. The total number of such “exoplanets” confirmed via Kepler and other methods now stands at more than 3,000.

This represents a revolution in planetary knowledge. A decade or so ago the discovery of even a single new exoplanet was big news. Not anymore. Improvements in astronomical observation technology have moved us from retail to wholesale planet discovery. We now know, for example, that every star in the sky likely hosts at least one planet.

But planets are only the beginning of the story. What everyone wants to know is whether any of these worlds has aliens living on it. Does our newfound knowledge of planets bring us any closer to answering that question?

A little bit, actually, yes. In a paper published in the May issue of the journal Astrobiology, the astronomer Woodruff Sullivan and I show that while we do not know if any advanced extraterrestrial civilizations currently exist in our galaxy, we now have enough information to conclude that they almost certainly existed at some point in cosmic history.

Among scientists, the probability of the existence of an alien society with which we might make contact is discussed in terms of something called the Drake equation. In 1961, the National Academy of Sciences asked the astronomer Frank Drake to host a scientific meeting on the possibilities of “interstellar communication.” Since the odds of contact with alien life depended on how many advanced extraterrestrial civilizations existed in the galaxy, Drake identified seven factors on which that number would depend, and incorporated them into an equation.

The first factor was the number of stars born each year. The second was the fraction of stars that had planets. After that came the number of planets per star that traveled in orbits in the right locations for life to form (assuming life requires liquid water). The next factor was the fraction of such planets where life actually got started. Then came factors for the fraction of life-bearing planets on which intelligence and advanced civilizations (meaning radio signal-emitting) evolved. The final factor was the average lifetime of a technological civilization.

Drake’s equation was not like Einstein’s E=mc2. It was not a statement of a universal law. It was a mechanism for fostering organized discussion, a way of understanding what we needed to know to answer the question about alien civilizations. In 1961, only the first factor — the number of stars born each year — was understood. And that level of ignorance remained until very recently.

That’s why discussions of extraterrestrial civilizations, no matter how learned, have historically boiled down to mere expressions of hope or pessimism. What, for example, is the fraction of planets that form life? Optimists might marshal sophisticated molecular biological models to argue for a large fraction. Pessimists then cite their own scientific data to argue for a fraction closer to 0. But with only one example of a life-bearing planet (ours), it’s hard to know who is right.

Or consider the average lifetime of a civilization. Humans have been using radio technology for only about 100 years. How much longer will our civilization last? A thousand more years? A hundred thousand more? Ten million more? If the average lifetime for a civilization is short, the galaxy is likely to be unpopulated most of the time. Once again, however, with only one example to draw from, it’s back to a battle between pessimists and optimists.

But our new planetary knowledge has removed some of the uncertainty from this debate. Three of the seven terms in Drake’s equation are now known. We know the number of stars born each year. We know that the percentage of stars hosting planets is about 100. And we also know that about 20 to 25 percent of those planets are in the right place for life to form. This puts us in a position, for the first time, to say something definitive about extraterrestrial civilizations — if we ask the right question.

In our recent paper, Professor Sullivan and I did this by shifting the focus of Drake’s equation. Instead of asking how many civilizations currently exist, we asked what the probability is that ours is the only technological civilization that has ever appeared. By asking this question, we could bypass the factor about the average lifetime of a civilization. This left us with only three unknown factors, which we combined into one “biotechnical” probability: the likelihood of the creation of life, intelligent life and technological capacity.

You might assume this probability is low, and thus the chances remain small that another technological civilization arose. But what our calculation revealed is that even if this probability is assumed to be extremely low, the odds that we are not the first technological civilization are actually high. Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first.

To give some context for that figure: In previous discussions of the Drake equation, a probability for civilizations to form of one in 10 billion per planet was considered highly pessimistic. According to our finding, even if you grant that level of pessimism, a trillion civilizations still would have appeared over the course of cosmic history.

In other words, given what we now know about the number and orbital positions of the galaxy’s planets, the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational.

In science an important step forward can be finding a question that can be answered with the data at hand. Our paper did just this. As for the big question — whether any other civilizations currently exist — we may have to wait a long while for relevant data. But we should not underestimate how far we have come in a short time.
#MakeTheDemocratsGreatAgain
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#11
(06-11-2016, 12:54 PM)Odin Wrote: Yes, There Have Been Aliens

Quote:LAST month astronomers from the Kepler spacecraft team announced the discovery of 1,284 new planets, all orbiting stars outside our solar system. The total number of such “exoplanets” confirmed via Kepler and other methods now stands at more than 3,000.

This represents a revolution in planetary knowledge. A decade or so ago the discovery of even a single new exoplanet was big news. Not anymore. Improvements in astronomical observation technology have moved us from retail to wholesale planet discovery. We now know, for example, that every star in the sky likely hosts at least one planet.

But planets are only the beginning of the story. What everyone wants to know is whether any of these worlds has aliens living on it. Does our newfound knowledge of planets bring us any closer to answering that question?

A little bit, actually, yes. In a paper published in the May issue of the journal Astrobiology, the astronomer Woodruff Sullivan and I show that while we do not know if any advanced extraterrestrial civilizations currently exist in our galaxy, we now have enough information to conclude that they almost certainly existed at some point in cosmic history.

Among scientists, the probability of the existence of an alien society with which we might make contact is discussed in terms of something called the Drake equation. In 1961, the National Academy of Sciences asked the astronomer Frank Drake to host a scientific meeting on the possibilities of “interstellar communication.” Since the odds of contact with alien life depended on how many advanced extraterrestrial civilizations existed in the galaxy, Drake identified seven factors on which that number would depend, and incorporated them into an equation.

The first factor was the number of stars born each year. The second was the fraction of stars that had planets. After that came the number of planets per star that traveled in orbits in the right locations for life to form (assuming life requires liquid water). The next factor was the fraction of such planets where life actually got started. Then came factors for the fraction of life-bearing planets on which intelligence and advanced civilizations (meaning radio signal-emitting) evolved. The final factor was the average lifetime of a technological civilization.

Drake’s equation was not like Einstein’s E=mc2. It was not a statement of a universal law. It was a mechanism for fostering organized discussion, a way of understanding what we needed to know to answer the question about alien civilizations. In 1961, only the first factor — the number of stars born each year — was understood. And that level of ignorance remained until very recently.

That’s why discussions of extraterrestrial civilizations, no matter how learned, have historically boiled down to mere expressions of hope or pessimism. What, for example, is the fraction of planets that form life? Optimists might marshal sophisticated molecular biological models to argue for a large fraction. Pessimists then cite their own scientific data to argue for a fraction closer to 0. But with only one example of a life-bearing planet (ours), it’s hard to know who is right.

Or consider the average lifetime of a civilization. Humans have been using radio technology for only about 100 years. How much longer will our civilization last? A thousand more years? A hundred thousand more? Ten million more? If the average lifetime for a civilization is short, the galaxy is likely to be unpopulated most of the time. Once again, however, with only one example to draw from, it’s back to a battle between pessimists and optimists.

But our new planetary knowledge has removed some of the uncertainty from this debate. Three of the seven terms in Drake’s equation are now known. We know the number of stars born each year. We know that the percentage of stars hosting planets is about 100. And we also know that about 20 to 25 percent of those planets are in the right place for life to form. This puts us in a position, for the first time, to say something definitive about extraterrestrial civilizations — if we ask the right question.

In our recent paper, Professor Sullivan and I did this by shifting the focus of Drake’s equation. Instead of asking how many civilizations currently exist, we asked what the probability is that ours is the only technological civilization that has ever appeared. By asking this question, we could bypass the factor about the average lifetime of a civilization. This left us with only three unknown factors, which we combined into one “biotechnical” probability: the likelihood of the creation of life, intelligent life and technological capacity.

You might assume this probability is low, and thus the chances remain small that another technological civilization arose. But what our calculation revealed is that even if this probability is assumed to be extremely low, the odds that we are not the first technological civilization are actually high. Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first.

To give some context for that figure: In previous discussions of the Drake equation, a probability for civilizations to form of one in 10 billion per planet was considered highly pessimistic. According to our finding, even if you grant that level of pessimism, a trillion civilizations still would have appeared over the course of cosmic history.

In other words, given what we now know about the number and orbital positions of the galaxy’s planets, the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational.

In science an important step forward can be finding a question that can be answered with the data at hand. Our paper did just this. As for the big question — whether any other civilizations currently exist — we may have to wait a long while for relevant data. But we should not underestimate how far we have come in a short time, has existed for only about e.


We need remember that human civilization (and there has been no non-human civilization) has existed for only about two millionths of the existence of the Earth. A technological civilization capable of giving interesting signals has existed for but a century.

Serious question exists about whether an advanced technological civilization keeps sending interesting signals into space. Two things can happen -- the end of such a civilization (self destruction through thermonuclear warfare?) or the purposeful cessation of transmission of interesting signals into space. A civilization might find the transmission of signals into space inefficient as some other technology appears, or that civilization might choose to avoid doing something to call attention to an aggressive civilization that sees technology a couple thousand years behind its technology and ripe for conquest or a slave trade.

So as important as whether we are looking at the right planet, are we looking at the right planet at the right time?
"The fool doth think he is wise, but the wise man knows himself to be a fool" -- William Shakespeare, As You Like It, V.i


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#12
Gravitational wave detection #2.

Quote:http://www.scientificamerican.com/articl...W_SPC_NEWS

… "Gravitational waves have struck again. Scientists who in February announced their landmark discovery of these ripples in spacetime revealed on Wednesday that they had detected more—again caused by a pair of crashing black holes. The gargantuan gravitational forces involved when two such incredibly dense objects ram into each other are so catastrophic that they wrench spacetime out of shape, curving it in powerful waves that travel clear across the cosmos. This second find shows that the initial discovery was not a rare windfall, but rather a preview of many more to come, ushering in an era where astronomers can use gravitational waves, rather than light, to “see” black holes and other invisible components of the hidden universe.”…
 … whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things. Phil 4:8 (ESV)
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#13
NASA announced Earth may have another moon. It’s much, much smaller than our original moon. Astronomers spotted it at the asteroid survey telescope in Haleakala, Hawaii.

http://www.businessinsider.com/earth-sec...ho3-2016-6

It (2016HO13) a captured asteroid, it has apparently been in a gravitational dance with the Earth for about a century and it could remain in that dance for centuries to come. It is from 38 to 100 times as far from the Earth as the moon, and it's not large -- about 100 meters or 300 feet, roughly the distance between two goal lines on an American football field and much smaller than some space satellites. It is beyond the usual range of space satellites in Earth orbit, some of which can be visible in a small telescope.
"The fool doth think he is wise, but the wise man knows himself to be a fool" -- William Shakespeare, As You Like It, V.i


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#14
Black holes are apparently excellent (if destructive) housekeepers.  -- pb

Supermassive black holes, with their immense gravitational pull, are notoriously good at clearing out their immediate surroundings by eating nearby objects. When a star passes within a certain distance of a black hole, the stellar material gets stretched and compressed -- or "spaghettified" -- as the black hole swallows it.

A black hole destroying a star, an event astronomers call "stellar tidal disruption," releases an enormous amount of energy, brightening the surroundings in an event called a flare. In recent years, a few dozen such flares have been discovered, but they are not well understood.
Astronomers now have new insights into tidal disruption flares, thanks to data from NASA's Wide-field Infrared Survey Explorer (WISE). Two new studies characterize tidal disruption flares by studying how surrounding dust absorbs and re-emits their light, like echoes. This approach allowed scientists to measure the energy of flares from stellar tidal disruption events more precisely than ever before.
"This is the first time we have clearly seen the infrared light echoes from multiple tidal disruption events," said Sjoert van Velzen, postdoctoral fellow at Johns Hopkins University, Baltimore, and lead author of a study finding three such events, to be published in the Astrophysical Journal. A fourth potential light echo based on WISE data has been reported by an independent study led by Ning Jiang, a postdoctoral researcher at the University of Science and Technology of China.

Flares from black holes eating stars contain high-energy radiation, including ultraviolet and X-ray light. Such flares destroy any dust that hangs out around a black hole. But at a certain distance from a black hole, dust can survive because the flare's radiation that reaches it is not as intense.

After the surviving dust is heated by a flare, it gives off infrared radiation. WISE measures this infrared emission from the dust near a black hole, which gives clues about tidal disruption flares and the nature of the dust itself. Infrared wavelengths of light are longer than visible light and cannot be seen with the naked eye. The WISE spacecraft, which maps the entire sky every six months, allowed the variation in infrared emission from the dust to be measured.

Astronomers used a technique called "photo-reverberation" or "light echoes" to characterize the dust. This method relies on measuring the delay between the original optical light flare and the subsequent infrared light variation, when the flare reaches the dust surrounding the black hole. This time delay is then used to determine the distance between the black hole and the dust.
Van Velzen's study looked at five possible tidal disruption events, and saw the light echo effect in three of them. Jiang's group saw it in an additional event called ASASSN-14li.

Measuring the infrared glow of dust heated by these flares allows astronomers to make estimates of the location of dust that encircles the black hole at the center of a galaxy.


"Our study confirms that the dust is there, and that we can use it to determine how much energy was generated in the destruction of the star," said Varoujan Gorjian, an astronomer at NASA's Jet Propulsion Laboratory, Pasadena, California, and co-author of the paper led by van Velzen.

Researchers found that the infrared emission from dust heated by a flare causes an infrared signal that can be detected for up to a year after the flare is at its most luminous. The results are consistent with the black hole having a patchy, spherical web of dust located a few trillion miles (half a light-year) from the black hole itself.

"The black hole has destroyed everything between itself and this dust shell," van Velzen said. "It's as though the black hole has cleaned its room by throwing flames."

JPL manages and operates WISE for NASA's Science Mission Directorate in Washington. The spacecraft was put into hibernation mode in 2011, after it scanned the entire sky twice, thereby completing its main objectives. In September 2013, WISE was reactivated, renamed NEOWISE and assigned a new mission to assist NASA's efforts to identify potentially hazardous near-Earth objects.
For more information on WISE, visit:
http://www.nasa.gov/wise

[/url]
[url=http://www.nasa.gov/wise]
http://www.nasa.gov/feature/jpl/studies-find-echoes-of-black-holes-eating-stars
"The fool doth think he is wise, but the wise man knows himself to be a fool" -- William Shakespeare, As You Like It, V.i


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#15
The Five-hundred-meter Aperture Spherical radio Telescope (FAST; Chinese: 五百米口径球面射电望远镜), nicknamed Tianyan (天眼, lit. "Heavenly Eye" or "The Eye of Heaven"), is a radio telescope located in the Dawodang depression (大窝凼洼地), a natural basin in Pingtang County, Guizhou Province, south China.[4] It consists of a fixed 500 m (1,600 ft) dish constructed in a natural depression in the landscape. It is the world's largest filled-aperture radio telescope,[5] and the second-largest single-dish aperture after the sparsely-filled RATAN-600 in Russia.[2][6]

It has a novel design, using an active surface for pointing and focusing, rather than only correcting residual errors,[7] and suspending the receiver on a computer-controlled winch system without any rigid connection to the primary.
Construction on the FAST project began in 2011 and it achieved first light in September 2016. It is currently undergoing testing and commissioning.

The telescope was first proposed in 1994. The project was approved by the National Development and Reform Commission (NDRC) in July 2007.[8][7] A 65-person village was relocated from the valley to make room for the telescope[9] and an additional 9,110 people living within a 5 km radius of the telescope were relocated to create a radio-quiet area.[9][10]
On 26 December 2008, a foundation laying ceremony was held on the construction site.[11] Construction started in March 2011,[12][13] and the last panel was installed on the morning of 3 July 2016.[9][13][14][15]

Originally budgeted for CN¥700 million,[2]:49[12] the final cost was CN¥1.2 billion (US$180 million).[9] Significant difficulties encountered were the site's remote location and poor road access, and the need to add shielding to suppress radio-frequency interference from the primary mirror actuators.[7] There are still ongoing problems with the failure rate of the primary mirror actuators.[7]

Testing and commissioning began with first light on 25 September 2016.[16] The first observations are being done without the active primary reflector, configuring it in a fixed shape and using the Earth's rotation to scan the sky.[7] Subsequent early science will take place at lower frequencies[17] while the active surface is brought to its design accuracy;[18] longer wavelengths are less sensitive to errors in reflector shape. It will take three years to calibrate the various instruments so it can become fully operational.[16] Once it does, it will likely require hundreds of astronomers. However, due to the shortage of astronomers, the telescope will not operate at full capacity for a long time.[19][verification needed]

Local government efforts to develop a tourist industry around the telescope are causing some concern among astronomers worried about nearby mobile telephones.[20]

The primary driving force behind the project[7] is Nan Rendong (南仁东), a researcher with the Chinese National Astronomical Observatory, part of the Chinese Academy of Sciences. He holds the positions of chief scientist[15] and chief engineer[7] of the project.

The basic design of FAST is similar to the Arecibo Observatory radio telescope. Both are fixed primary reflectors installed in natural hollows, made of perforated aluminum panels with a movable receiver suspended above. There are, however, four significant differences in addition to the size.[22][26][27]

First, Arecibo's dish is fixed in a spherical shape. Although it is also suspended from steel cables with supports underneath for fine-tuning the shape, they are manually operated and adjusted only for maintenance.[22] It has a fixed spherical shape and two additional reflectors suspended above to correct for the resultant spherical aberration.[28]

Second, Arecibo's receiver platform is fixed in place. To support the greater weight of the additional reflectors, the primary support cables are static, with the only motorised portion being three hold-down winches which compensate for thermal expansion.[22]:3 The antennas are mounted on a rotating arm below the platform.[22]:4 This smaller range of motion limits it to viewing objects within 19.7° of the zenith.[29]

Third, the FAST dish is significantly deeper, contributing to a wider field of view. Although 64% larger in diameter, FAST's radius of curvature is 300 m (980 ft),[13]:3 barely larger than Arecibo's 270 m (870 ft),[29] so it forms a 113° arc[13]:4[dubiousdiscuss] (vs. 70° for Arecibo). Although Arecibo's full aperture of 305 m (1,000 ft) can be used when observing objects at the zenith, the effective aperture for more typical inclined observations is 221 m (725 ft).[22]:4

Fourth, Arecibo's larger secondary platform also houses several transmitters, making it one of only two instruments in the world capable of radar astronomy.[citation needed] The NASA-funded Planetary Radar System allows Arecibo to study solid objects from Mercury to Saturn, and to perform very accurate orbit determination on near-earth objects, particularly potentially hazardous objects. Arecibo also includes several NSF funded radars for ionospheric studies, the 430 MHz at 2.5 TW[citation needed], 47 MHz at 300 MW[citation needed], and 8 MHz at 6 MW. FAST's smaller receiver platform makes radar studies of the ionosphere impossible, so it will not be able to participate in planetary defense.[citation needed]

The Arecibo observatory has the advantage of location closer to the equator, so the Earth's rotation scans a larger fraction of the sky. Arecibo is located at 18.35° N latitude, while FAST is sited about 7.5° farther north, at about 25.80° N.[citation needed] FAST's wider field of view more than makes up for this.[citation needed]

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"The fool doth think he is wise, but the wise man knows himself to be a fool" -- William Shakespeare, As You Like It, V.i


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#16


"I close my eyes, and I can see a better day" -- Justin Bieber

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Eric M
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#17
The first observation of a neutron star merger in gravitational waves – as well as gamma rays, visible light, and other forms of electromagnetic radiation – is announced.
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GW170817 is a gravitational wave (GW) signal observed by the LIGO and Virgo detectors on 17 August 2017. The GW was produced by the last minutes of two neutron stars spiralling closer to each other and finally merging.
Unlike all previous GW detections, which were of merging black holes not expected to produce a detectable electromagnetic signal,[2][3][a] the aftermath of the merger was also seen by many conventional telescopes, marking a significant breakthrough for multi-messenger astronomy.[5][6][7][8][9]

Technically, there are three separate observations, and strong evidence that they come from the same astronomical source:
  • The gravitational wave signal, which had a duration of approximately 100 seconds, and shows the characteristics expected of the inspiral of two neutron stars. Using three detectors (two LIGO and one VIRGO), an approximate sky position could be computed.
  • The short gamma-ray burst GRB 170817A[10][11] detected by the Fermi and INTEGRAL spacecraft 1.7 seconds after the GW signal ended. These detectors have very limited directional sensitivity, but indicated a large area of the sky which overlapped the gravitational wave position. It has long been theorized that short gamma-ray bursts are caused by neutron star mergers.
  • The optical transient AT 2017gfo, found 11 hours later in the galaxy NGC 4993[12] during a search of the region indicated by the GW detection. This was observed by numerous telescopes, from radio to X-ray wavelengths, over the following days and weeks, and shows the characteristics (a fast-moving, rapidly-cooling cloud of neutron-rich material) expected of debris ejected from a neutron-star merger.
The event was officially announced on 16 October 2017[10][11] at press conferences at the National Press Club in Washington, D.C. and at the ESO headquarters in Garching bei München in Germany.[12]

The first public information about the event was tweeted by astronomer J. Craig Wheeler of the University of Texas at Austin on 18 August 2017. He later deleted the tweet and apologized for scooping the official announcement protocol. Other people followed up on the rumor, and reported that the public logs of several major telescopes listed priority interruptions in order to observe NGC 4993, a galaxy 40 Mpc (130 Mly) away in the Hydra constellation.[13][14] The collaboration had earlier declined to comment on the rumors, not adding to a previous announcement that there were several triggers under analysis.[15][16]

he first electromagnetic signal detected was GRB 170817A, a short gamma ray burst, detected 1.74±0.05 s after the merger time and lasting for a few seconds.[11][13]

GRB 170817A was discovered by the Fermi gamma-ray telescope, with an automatic alert issued just 14 seconds after the GRB detection. After the LIGO/Virgo circular 40 minutes later, manual processing of data from the INTEGRAL gamma-ray telescope also detected the same GRB. The difference in arrival time between Fermi and INTEGRAL helped to improve the sky localization.
This GRB was relatively faint given the proximity of NGC 4993, possibly due to its jets not being pointed directly toward Earth, but rather at an angle of about 30 degrees to the side.[12][20]

series of alerts to other astronomers were issued, beginning with a report of the gamma-ray detection and single-detector LIGO trigger at 13:21, and a three-detector sky location at 17:54 UTC.[18] These prompted a massive search by many survey and robotic telescopes. In addition its expected large size (about 150 times the area of a full moon), this search was challenging because the search area was near the Sun in the sky and thus visible for only an hour after twilight for any given telescope.
In total six teams (SSS, DLT40, VISTA, Master, DECam, Las Campanas Observatory (LCO) Chile) imaged the same new source independently in a 90-minute interval.[1]:5 The first to detect optical light associated with the collision was the Swope Supernova Survey, which found it in an image of NGC4993 taken 10 hours and 52 minutes after the event[11][1][21] by the 1 meter (3 ft 3 in) diameter Swope Telescope operating in the near infrared at LCO, Chile. They were also the first to announce it, naming their detection SSS17a in a circular issued 12h 26min post-event. The new source was later given an official International Astronomical Union (IAU) designation of AT 2017gfo.

The SSS team surveyed all galaxies in the region of space predicted by the gravitational wave observations, and identified a single new transient.[20][21] By identifying the host galaxy of the merger, it is possible to provide a more accurate distance than based on gravitational waves alone. The detection of the optical/near-infrared source provided a huge improvement in localisation, reducing the uncertainty from several degrees to 0.0001 degree; this enabled many large ground and space telescopes to follow-up the source over the following days and weeks. Within hours after localization, many additional observations were made across the infrared and visible spectrum.[21] Over the following days, the color of the optical source changed from blue to red as the source expanded and cooled.[20]
Numerous optical and infrared spectra were observed; early spectra were nearly featureless, but after a few days, broad features emerged indicative of material ejected at roughly 10 percent of light speed.

Nine days later, the source was detected in X-rays by the Chandra X-ray Observatory (after non-detections at earlier times). Sixteen days after the merger event, the source was detected in radio with the Karl G. Jansky Very Large Array (VLA) in New Mexico.[12] More than 70 observatories covering the electromagnetic spectrum observed the event.[12]

No neutrinos consistent with the source were found in follow-up searches.[5][1] A possible explanation for the non-detection of neutrinos is because the event was observed at a large off-axis angle i.e. the outflow jet was not directed toward Earth.[22]

(an outflow jet directed at the Earth would have been extremely troublesome -- my comment).

The gravitational wave signal indicated that the gravitational wave event was associated with the collision of two neutron stars[13][14][16][23] with a total mass of 2.82+0.47


−0.09 times the mass of the sun (solar masses).[5] If low spins are assumed, consistent with those observed in binary neutron stars that will merge within a Hubble time, the total mass is 2.74+0.04
−0.01
 M.

The masses of the component stars have greater uncertainty. The larger (m1) has a 90% chance of being between 1.36 and 2.26 M☉, and the smaller (m2) has a 90% chance of being between 0.86 and 1.36 M☉.[24] Under the low spin assumption, the ranges are 1.36 to 1.60 M☉ for m1 and 1.17 to 1.36 M☉ for m2.
The chirp mass, a directly observable parameter which may be very roughly equated to the geometric mean of the masses, is measured at 1.188+0.004
−0.002
 M☉.[24]

The neutron star merger event is thought to be followed by a kilonova. Kilonovae are candidates for the production of half the chemical elements heavier than iron in the Universe.[12] A total of 16,000 times the mass of the Earth in heavy elements is believed to have formed, including approximately ten Earth masses just of the two elements gold and platinum.[25]
It is not known what object was produced by the merger. It could be either a neutron star heavier than any known neutron star, or a black hole lighter than any known black hole.[20]


Scientific interest in the event was enormous, with dozens of preliminary papers (and almost 100 preprints[26]) published the day of the announcement, including eight letters in Science,[27] six in Nature, and 23 in a special issue of The Astrophysical Journal Letters devoted to the subject.[6]

This is not the first observation that is known to be of a neutron star merger; GRB 130603B was the first observed kilonova. It is however, by far the best observation, making this the strongest evidence to date to confirm the hypothesis that mergers of binary stars are the cause of short gamma-ray bursts.[5]

The event also provides a limit on the difference between the speed of light and that of gravity. Assuming the first photons were emitted between zero and ten seconds after peak gravitational wave emission, the difference between the speeds of gravitational and electromagnetic waves, vGW − vEM, is constrained to between −3×10−15 and +7×10−16 times the speed of light.[24] In addition, it allowed investigation of the equivalence principle (through Shapiro delay measurement) and Lorentz invariance.[5] The limits of possible violations of Lorentz invariance (values of 'gravity sector coefficients') are reduced by the new observations, by up to ten orders of magnitude.[24] GW170817 also excluded some alternatives to general relativity, including variants of scalar–tensor theory, Hořava–Lifshitz gravity[28][29][30] and bimetric gravity.[31]

Gravitational wave signals such as GW170817 may be used as a standard siren to provide an independent measurement of the Hubble constant.[32][33]

Electromagnetic observations helped to support the theory that the mergers of neutron stars contribute to [url=https://en.wikipedia.org/wiki/R-process]r-process nucleosynthesis.[21]
"The fool doth think he is wise, but the wise man knows himself to be a fool" -- William Shakespeare, As You Like It, V.i


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