Black Hole Winds Provide Clues to Early Galaxies

Startlingly powerful black hole jets are erupting in a nearby galaxy.

This composite image of the spiral galaxy M83 was assembled from observations made by NASA's Hubble Space Telescope and the Carnegie Institution of Washington's Magellan telescopes.

PHOTOGRAPH BY HUBBLE HERITAGE TEAM, NASA, EUROPEAN SPACE AGENCY

Dan Vergano

National Geographic

Published February 27, 2014

Surprisingly powerful x-ray jets blast out from a large black hole in a nearby galaxy, astronomers report.
Located in the M83 spiral galaxy (at 15 million light-years away, close by astronomical standards), the black hole likely resembles the powerful ones that filled the universe in the era of the first galaxies. Astronomers expect it will offer insight into the formation of the star-stuffed conglomerations that later grew into galaxies such as our own Milky Way. (Read "Star Eater" in National Geographic magazine.)

"The jets are cutting through the galaxy like bullets fired through a cloud," says astronomer Roberto Soria of Australia's Curtin University in Perth, who led the black hole study released by the journal Science. "It is a great opportunity to see up close the dynamics of really active black holes on galaxies."

The jets pack a punch 7.5 million times more powerful than the energy our sun releases every second, making it an "ultraluminous x-ray source" in astronomical terms. (See also: "Are We Living in a Black Hole?")

"This confirms and improves on previous results, and it is important, as it shows how [ultraluminous black holes] can impact on their host environment, which could be an important feedback mechanism in the history of galaxy evolution," says astronomer Andrew Sutton of the United Kingdom's Durham University, who was not on the study team.

Neighbors Coming Over for Dinner

Black holes are essentially collapsed stars, their gravity so strong that even light cannot escape their grasp. The black hole in M83 weighs about a hundred times as much as the sun. The team suggests that, most likely, the jets are erupting from the black hole as it devours gases from a nearby companion star.

The spinning disk of star stuff surrounding the black hole whips to nearly light-speed as it heads into the black hole's maw, which releases heat and energy that erupt as jets from the poles of the collapsed star.

"All of the power comes, ultimately, from everything falling into the gravity of this black hole, which is so powerful that it converts this motion into radiation," Soria says. (See also: "Behind the Cover: How Do You Show the Unshowable?")

X-Ray Survey

The black hole exists outside the center of the M83 galaxy, far from a much larger "supermassive" black hole at its center. Soria's team was actually looking for remnants of exploded supernova stars, which give off x-rays, when they discovered the black hole.

It stood out in their survey, which partly relied on NASA's Chandra X-ray Space Telescope, because its x-ray levels were ten times higher than normal. "We knew it had to be a black hole," Soria says.

Follow Dan Vergano on Twitter.

Source:NationalGeoghrapic.com

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Bullying black holes force galaxies to stay red and dead

Scientists discovered that black hole jets could prevent nearby gas from turning into stars.

By ESA, Noordwijk, Netherlands  |  Published: Wednesday, February 26, 2014

RELATED TOPICS: GALAXIES | HERSCHEL | BLACK HOLES

Multi-wavelength view of the elliptical galaxy NGC 5044.

Digitized Sky Survey/NASA Chandra/Southern Observatory for Astrophysical Research/Very Large Array (Robert Dunn et al. 2010)

The Herschel Space Observatory has discovered massive elliptical galaxies in the nearby universe containing plenty of cold gas, even though the galaxies fail to produce new stars. Comparison with other data suggests that while hot gas cools down in these galaxies, stars do not form because jets from the central supermassive black hole heat or stir up the gas and prevent it from turning into stars.

Giant elliptical galaxies are the most puzzling type of galaxy in the universe. Since they mysteriously shut down their star-forming activity and remain home only to the longest-lived of their stars — which are low-mass ones and appear red — astronomers often call these galaxies “red and dead.”

Up until now, it was thought that red-and-dead galaxies were poor in cold gas — the vital raw material from which stars are born. While cold gas is abundant in spiral galaxies with lively star formation, the lack of it in giant ellipticals seemed to explain the absence of new stars.

Astronomers have long been debating the physical processes leading to the end of their star formation. They speculated that these galaxies somehow expelled the cold gas, or that they had simply used it all to form stars in the past. Although the reason was uncertain, one thing seemed to have been established: These galaxies are red and dead because they no longer possess the means to sustain the production of stars.

This view is being challenged by a new study based on data from the European Space Agency’s (ESA) Herschel Space Observatory.

"We looked at eight giant elliptical galaxies that nobody had looked at with Herschel before, and we were delighted to find that, contrary to previous belief, six out of eight abound with cold gas," said Norbert Werner from Stanford University in California.

This is the first time that astronomers have seen large amounts of cold gas in red-and-dead galaxies that are not located at the center of a massive galaxy cluster.

The cold gas manifested itself through far-infrared emissions from carbon ions and oxygen atoms. Herschel's sensitivity at these wavelengths was instrumental to the discovery.

"While we see cold gas, there is no sign of ongoing star formation," said co-author Raymond Oonk from ASTRON, the Netherlands Institute for Radio Astronomy.

"This is bizarre: With plenty of cold gas at their disposal, why aren't these galaxies forming stars?"

The astronomers proceeded to investigate their sample of galaxies across the electromagnetic spectrum because gas at different temperatures shines brightly at different wavelengths. They used optical images to probe the warm gas, at slightly higher temperatures than the cold one detected with Herschel, and X-ray data from NASA's Chandra X-ray Observatory to trace the hot gas, up to tens of millions of kelvins.

"In the six galaxies that are rich in cold gas, the X-ray data show telltale signs that the hot gas is cooling," said Werner.

This is consistent with theoretical expectations: Once cooled, the hot gas would become the warm and cold gas that is observed at longer wavelengths. However, in these galaxies the cooling process somehow stopped, and the cold gas failed to condense and form stars.

In the other two galaxies of the sample — the ones without cold gas — the hot gas does not appear to be cooling at all. "The contrasting behavior of these galaxies may have a common explanation — the central supermassive black hole," said Oonk.

In some theoretical models, the level of a black hole's activity could explain why gas in a galaxy is able — or not able — to cool and form stars. And this seems to apply for the galaxies studied by Werner and his colleagues, too.

While the six galaxies with plenty of cold gas harbor moderately active black holes at their centers, the other two show a marked difference. In the two galaxies without cold gas, the central black holes are accreting matter at frenzied pace, as confirmed by radio observations showing powerful jets of highly energetic particles that stem from their cores.

The jets could be an effect of the hot gas cooling down and flowing toward the center of the galaxies. This inflow of cold gas can boost the black hole's accretion rate, launching the jets that are observed at radio wavelengths.

The jets, in turn, have the potential to reheat the galaxy's reservoir of cold gas or even push it beyond the galaxy's reach. This scenario can explain the absence of star formation in all the galaxies observed in this study and, at the same time, the lack of cold gas in those with powerful jets.

"These galaxies are red, but with the giant black holes pumping in their hearts, they are definitely not dead," said Werner.

"Once again, Herschel has detected something that was never seen before — significant amounts of cold gas in nearby red-and-dead galaxies," said Göran Pilbratt from ESA, "nevertheless, these galaxies do not form stars, and the culprit seems to be the black hole."

Source:Astronomy.com

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The Submillimeter Array telescope unveils how small cosmic seeds grow into big stars

The results show that high-mass stars aren’t born alone but in groups.

By Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts  |  Published: Thursday, February 27, 2014

RELATED TOPICS: STARS | STAR FORMATION | NEBULA

These two panels show the Snake Nebula as photographed by the Spitzer and Herschel space telescopes. At mid-infrared wavelengths (the upper panel taken by Spitzer), the thick nebular material blocks light from more distant stars. At far-infrared wavelengths, however (the lower panel taken by Herschel), the nebula glows due to emission from cold dust. The two boxed regions, P1 and P6, were examined in more detail by the Submillimeter Array (SMA).

Spitzer/GLIMPSE/MIPS, Herschel/HiGal, Ke Wang (ESO)

New images from the Smithsonian’s Submillimeter Array (SMA) telescope provide the most detailed view yet of stellar nurseries within the Snake Nebula. These images offer new insights into how cosmic seeds can grow into massive stars.

Stretching across almost 100 light-years of space, the Snake Nebula is located about 11,700 light-years from Earth in the direction of the constellation Ophiuchus. In images from NASA’s Spitzer Space Telescope, it appears as a sinuous dark tendril against the starry background. It was targeted because it shows the potential to form many massive stars (stars heavier than eight times our Sun).

“To learn how stars form, we have to catch them in their earliest phases, while they’re still deeply embedded in clouds of gas and dust, and the SMA is an excellent telescope to do so,” said Ke Wang of the European Southern Observatory (ESO).

The team studied two specific spots within the Snake Nebula, designated P1 and P6. Within those two regions, they detected a total of 23 cosmic “seeds” — faintly glowing spots that will eventually birth one or a few stars. The seeds generally weigh between five and 25 times the mass of the Sun, and each spans only a few thousand astronomical units — the average Earth-Sun distance. The sensitive high-resolution SMA images not only unveil the small seeds, but also differentiate them in age.

Previous theories proposed that high-mass stars form within massive isolated “cores” weighing at least 100 times the mass of the Sun. These new results show that that is not the case. The data also demonstrate that massive stars aren’t born alone but in groups.

“High-mass stars form in villages,” said Qizhou Zhang of the Center for Astrophysics in Cambridge, Massachusetts. “It’s a family affair.”

The team also was surprised to find that these two nebular patches had fragmented into individual star seeds so early in the star formation process.

They detected bipolar outflows and other signs of active, ongoing star formation. Eventually, the Snake Nebula will dissolve and shine as a chain of several star clusters.

Source:Astronomy.com

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Super Earths May be a dead world

Scientists find that planets that form from less massive cores can become benign habitats for life, whereas the larger objects instead end up as “mini-Neptunes” with thick atmospheres and probably stay sterile.

By Royal Astronomical Society, United Kingdom  |  Published: Thursday, February 27, 2014

RELATED TOPICS: EXOPLANETS | KEPLER | SUPER EARTHS

The mass of the initial rocky core determines whether the final planet is potentially habitable. On the top row of the diagram, the core has a mass of more than 1.5 times that of Earth. The result is that it holds on to a thick atmosphere of hydrogen (H), deuterium (H2) and helium (He). The lower row shows the evolution of a smaller mass core, between 0.5 and 1.5 times the mass of Earth. It holds on to far less of the lighter gases, making it much more likely to develop an atmosphere suitable for life.

NASA/H. Lammer

In the last 20 years, the search for Earth-like planets around other stars has accelerated with the launch of missions like the Kepler space telescope. Using these and observatories on the ground, astronomers have found numerous worlds that at first sight have similarities with Earth. A few of these are even in the “habitable zone” where the temperature is just right for water to be in liquid form and so are prime targets in the search for life elsewhere in the universe.

Now, a team of scientists has looked at how these worlds form and suggest that many of them may be a lot less clement than was thought. They find that planets that form from less massive cores can become benign habitats for life, whereas the larger objects instead end up as “mini-Neptunes” with thick atmospheres and probably stay sterile.

Planetary systems, including our solar system, are thought to form from hydrogen, helium, and heavier elements that orbit their parent stars in a so-called protoplanetary disk. Dust and rocky material is thought to clump together over time, eventually forming rocky cores that go on to be planets. The gravity of these cores attracts hydrogen from the disk around them, some of which is stripped away by the ultraviolet light of the young star they orbit.

Helmut Lammer of the Space Research Institute (IWF) of the Austrian Academy of Sciences and his team modeled the balance of capture and removal of hydrogen for planetary cores between 0.1 and 5 times the mass of Earth, located in the habitable zone of a Sun-like star. In their model, they found that protoplanets with the same density of Earth, but less than half its mass will not capture much gas from the disk.

Depending on the disk and assuming that the young star is much brighter in ultraviolet light than the Sun is today, planetary cores with a similar mass to Earth can capture but also lose their enveloping hydrogen. But the highest-mass cores, similar to the “super-Earths” found around many stars, hold on to almost all of their hydrogen. These planets end up as mini-Neptunes with far thicker atmospheres than our home planet.

The results suggest that for some of the recently discovered super-Earths, such as Kepler-62e and -62f, being in the habitable zone is not enough to make them habitats.

“Our results suggest that worlds like these two super-Earths may have captured the equivalent of between 100 and 1,000 times the hydrogen in Earth’s oceans, but may only lose a few percent of it over their lifetime,” said Lammer. “With such thick atmospheres, the pressure on the surfaces will be huge, making it almost impossible for life to exist.”

The ongoing discovery of low (average) density super-Earths supports the results of the study. Scientists will need to look even harder to find places where life could be found, setting a challenge for astronomers using the giant telescopes that will come into use in the next decade.

Source:Astronomy.com

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Surprise: Elephants Comfort Upset Friends

Asian elephants recognize distress and offer a helping trunk, study says.

Asian elephants (pictured) caress each other when stressed.

PHOTOGRAPH BY ZSSD, MINDEN PICTURES/CORBIS

Jennifer S. Holland

for National Geographic

Published February 18, 2014

The short list of animals that console stressed-out friends just got longer … and heavier.

Asian elephants, like great apes, dogs, certain corvids (the bird group that includes ravens), and us, have now been shown to recognize when a herd mate is upset and to offer gentle caresses and chirps of sympathy, according to a study published February 18 in the online journal PeerJ.

Joshua Plotnik, a behavioral ecologist at Mahidol University in Kanchanaburi, Thailand, and primatologist Frans de Waal, director of Emory University's Living Links Center, have shown through a controlled study what those who work with elephants have always believed: The animals, in this case captive Asian elephants (Elephas maximus), offer something akin to humans' sympathetic concern when observing distress in another.

Intimate Gestures

The scientists studied 26 elephants of varying ages at the Elephant Nature Park in the Mae Tang district of Chiang Mai Province, Thailand. (Adult male elephants were excluded for safety reasons.)

It would be unethical to set up stressful situations, so they instead waited patiently for such moments to occur naturally.

A stress-inducing situation might be a dog walking by or a snake rustling the grass, or the roar or just the presence of a bull elephant. Sometimes the stressor was unknown. Regardless, scientists know elephant distress when they see it: erect tails and flared ears; vocalizations such as trumpeting, rumbling, or roaring; and sudden defecation and urination tell the story.

Over the course of a year, they spent up to two weeks per month and three hours daily observing the animals.

During these observations, the scientists witnessed bystander elephants—those not directly affected by a stressor—moving to and giving upset elephants physical caresses, mostly inside the mouth (which is kind of like a hug to elephants) and on the genitals. (Also see "African Elephants Understand Human Gestures.")

Bystanders also rumbled and chirped with vocal offerings that suggested reassurance. Sometimes the empathetic animals formed a protective circle around the distressed one.

There was also evidence of "emotional contagion," when herd mates matched the behavior and emotional state of the upset individual. In other words, seeing a "friend" in distress was distressing to the observers. Those animals also consoled one another.

"With their strong bonds, it is not surprising that elephants show concern for others," says de Waal, who describes empathy as a "general mammalian trait."

"They get distressed when they see others in distress, reaching out to calm them down, not unlike the way chimpanzees or humans embrace someone who is upset."

Still, "I was surprised at how consistent the elephants' consolation behavior was," says Plotnik, who is also the founder of the nonprofit Think Elephants International.

"Whenever an elephant showed signs of distress, a reassuring friend was sure to come console them. The number of times when elephants showed distress without a response from others was very rare."

Empathetic Elephants

Elephants, whose herds are headed by a matriarch and consist most often of females, babies, and immature males, have long been known to bond strongly with their kind.

They celebrate births and mourn the dead. (Watch a video of elephants grieving.) Females will "allomother" (help to raise another's baby) and respond fully and quickly to cries from other mothers' young.

Elephants will also aid a weaker animal—such as by helping the injured along—a sign of being able to consider and empathize with another's perspective.

Still, points out de Waal, "many people are impressed by elephant intelligence, but actual hard data are scarce. We need to study them just as carefully as we do primates, dogs, or corvids." (Read "Elephants Use Their Trunks to Ace Intelligence Tests.")

Keeping the peace is certainly valuable to all animals in a group, so one animal "making up" with another after a conflict makes sense for all. But bystander empathy—just being a concerned friend—takes things to a different emotional level.

The Road to Kindness

Plotnik says not only is this work fascinating from the "what other animals are capable of" perspective, it's also a wonderful example of convergent evolution, which occurs when similar traits or behaviors (in this case empathy/consolation) evolve separately (for example, in apes and elephants) as a result of similar environmental pressures.

"I find this very exciting, because it suggests that the buck does NOT stop with us humans when it comes to smarts!" he says. (Read "Inside Animal Minds" in National Geographic magazine.)

Also, "the more we learn about how elephants think; make decisions; and see, hear, and smell their worlds, the better perspective we will have when trying to find ways to mitigate conservation problems," he says.

In the meantime, it will require more studies to figure out exactly how both givers and receivers benefit from this caring display by elephants. But the nonhuman road to kindness appears to be reaching new lengths.

Jennifer S. Holland has written about animal empathy in her two books Unlikely Friendships and Unlikely Loves. Follow her on Twitter.

Source:NationalGeoghraphic.com

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