суббота, 30 ноября 2019 г.

Scientists inch closer than ever to signal from cosmic dawn

Around 12 billion years ago, the universe emerged from a great cosmic dark age as the first stars and galaxies lit up. With a new analysis of data collected by the Murchison Widefield Array (MWA) radio telescope, scientists are now closer than ever to detecting the ultra-faint signature of this turning point in cosmic history.

Scientists inch closer than ever to signal from cosmic dawn
The Murchison Widefield Array radio telescope, a portion of which is pictured here, is searching
 for a signal emitted during the formation of the first stars in the universe
[Credit: Goldsmith/MWA Collaboration/Curtin University]
In a paper on the preprint site ArXiv and soon to be published in the Astrophysical Journal, researchers present the first analysis of data from a new configuration of the MWA designed specifically to look for the signal of neutral hydrogen, the gas that dominated the universe during the cosmic dark age. The analysis sets a new limit -- the lowest limit yet -- for the strength of the neutral hydrogen signal.

"We can say with confidence that if the neutral hydrogen signal was any stronger than the limit we set in the paper, then the telescope would have detected it," said Jonathan Pober, an assistant professor of physics at Brown University and corresponding author on the new paper. "These findings can help us to further constrain the timing of when the cosmic dark ages ended and the first stars emerged."

The research was led by Wenyang Li, who performed the work as a Ph.D. student at Brown. Li and Pober collaborated with an international group of researchers working with the MWA.

Despite its importance in cosmic history, little is known about the period when the first stars formed, which is known as the Epoch of Reionization (EoR). The first atoms that formed after the Big Bang were positively charged hydrogen ions -- atoms whose electrons were stripped away by the energy of the infant universe. As the universe cooled and expanded, hydrogen atoms reunited with their electrons to form neutral hydrogen. And that's just about all there was in the universe until about 12 billion years ago, when atoms started clumping together to form stars and galaxies. Light from those objects re-ionized the neutral hydrogen, causing it to largely disappear from interstellar space.

The goal of projects like the one happening at MWA is to locate the signal of neutral hydrogen from the dark ages and measure how it changed as the EoR unfolded. Doing so could reveal new and critical information about the first stars -- the building blocks of the universe we see today. But catching any glimpse of that 12-billion-year-old signal is a difficult task that requires instruments with exquisite sensitivity.

When it began operating in 2013, the MWA was an array of 2,048 radio antennas arranged across the remote countryside of Western Australia. The antennas are bundled together into 128 "tiles," whose signals are combined by a supercomputer called the Correlator. In 2016, the number of tiles was doubled to 256, and their configuration across the landscape was altered to improve their sensitivity to the neutral hydrogen signal. This new paper is the first analysis of data from the expanded array.

Neutral hydrogen emits radiation at a wavelength of 21 centimeters. As the universe has expanded over the past 12 billion years, the signal from the EoR is now stretched to about 2 meters, and that's what MWA astronomers are looking for. The problem is there are myriad other sources that emit at the same wavelength -- human-made sources like digital television as well as natural sources from within the Milky Way and from millions of other galaxies.

"All of these other sources are many orders of magnitude stronger than the signal we're trying to detect," Pober said. "Even an FM radio signal that's reflected off an airplane that happens to be passing above the telescope is enough to contaminate the data."

To home in on the signal, the researchers use a myriad of processing techniques to weed out those contaminants. At the same time, they account for the unique frequency responses of the telescope itself.

"If we look at different radio frequencies or wavelengths, the telescope behaves a little differently," Pober said. "Correcting for the telescope response is absolutely critical for then doing the separation of astrophysical contaminants and the signal of interest."

Those data analysis techniques combined with the expanded capacity of the telescope itself resulted in a new upper bound of the EoR signal strength. It's the second consecutive best-limit-to-date analysis to be released by MWA and raises hope that the experiment will one day detect the elusive EoR signal.

"This analysis demonstrates that the phase two upgrade had a lot of its desired effects and that the new analysis techniques will improve future analyses," Pober said. "The fact that MWA has now published back-to-back the two best limits on the signal gives momentum to the idea that this experiment and its approach has a lot of promise."

Source: Brown University [November 27, 2019]

* This article was originally published here

Researchers show how feathers propel birds through air and history

New research from an international team led by USC scientists set out to learn how feathers developed and helped birds spread across the world. Flight feathers, in particular, are masterpieces of propulsion and adaptation, helping penguins swim, eagles soar and hummingbirds hover.

Researchers show how feathers propel birds through air and history
A Taiwan blue magpie in flight [Credit: Shao Huan Lang]
Despite such diversity, the feather shares a common core design: a one-style-fits-all model with option trims for specialized performance. This simplicity and flexibility found in nature holds promise for engineers looking for better ways to build drones, wind turbines, medical implants and other advanced materials.

Those findings, published in Cell, offer an in-depth look at the form and function of a feather based on a comparative analysis of their physical structure, cellular composition and evolution. The study compares feathers of 21 bird species from around the world.

"We've always wondered how birds can fly in so many different ways, and we found the difference in flight styles is largely due to the characteristics of their flight feathers," said Cheng-Ming Chuong, the study's lead author and a developmental biologist in the Department of Pathology at the Keck School of Medicine of USC. "We want to learn how flight feathers are made so we can better understand nature and learn how biological architecture principles can benefit modern technology."

To gain a comprehensive understanding of the flight feather, Chuong formed a multi-disciplinary international team with Wen Tau Juan, a biophysicist at the Integrative Stem Cell Center, China Medical University in Taiwan. The work involved experts in stem cells, molecular biology, anatomy, physics, bio-imaging, engineering, materials science, bioinformatics and animal science. The bird species studied include ostrich, sparrow, eagle, chickens, ducks, swallow, owl, penguin, peacock, heron and hummingbird, among others.

They compared feathers using fossils, stem cells and flight performance characteristics. They focused on the feather shaft, or rachis, that supports the feather much like a mast holds a sail, bearing the stress between wind and wing. They also focused on the vane, the lateral branches astride the shaft that give the feather its shape to flap the air. And they examined how evolution shaped the barbs, ridges and hooks that help a feather hold its form and lock with adjacent feathers like Velcro to form a wing. The goal was to understand how a simple filament appendage on dinosaurs transformed into a three-level branched structure with different functions.

For birds such as ducks, eagles and sparrows that fly in different modes, the scientists noted significant differences in the feather shaft compared to ground-hugging birds. On the rigid exterior, the shaft cortex was thinner and lightweight, while the interior was filled with porous cells resembling bubble wrap, aligned into bands of various orientations and reinforced with ridges that operate like tiny lateral beams. Together, it forms a light, hollow and buoyant structure to enable flight. Cross-sections of feather shafts of different birds show highly specialized shapes and orientations of the inner core and outer cortex.

Researchers show how feathers propel birds through air and history
This picture shows a the asymmetric vane and tapering main shaft of a single flight feather
from a goshawk [Credit: Hao Howard Wu & Wen Tau Juan]
"The flight feather is made of two highly adaptable architectural modules, light and strong materials that can develop into highly adaptable configurations," Chuong said.

The researchers discovered two different molecular mechanisms guiding feather growth. Cortex thickness was governed by bone morphogenetic proteins, which are molecular signals for tissue growth. The porous feather interior, or medulla, relied upon a different mechanism known as transforming growth factor beta (TGF-b). Both components originate as stem cells in the bird's skin.

By contrast, feathers in flightless birds were simpler, consisting of a dense cortex exterior that is more rigid and sturdy with fewer internal struts and cells found in flying birds. The features were especially pronounced for penguins, which use wings as paddles under the water.

As part of the study, the researchers looked at nearly 100 million-year-old feathers, found embedded in amber in Myanmar. These fossils show early feathers lacked one key feature that modern birds have. Specifically, the researchers report how fossil feathers had barb branches and barbules, which form a feather vane by overlapping, but not hooklets. The hooklets, which act like clasps to turn fluffy feathers into a tight flat plane for high-performance flight, evolved later. The scientists also identified WNT2B, another growth factor, as the agent that controls hooklet formation. These also originated from epidermal stem cells.

Taken together, the findings show how feathered dinosaurs and early birds could form a primitive vane by overlapping barbule plates, although that wasn't aerodynamically fit to carry much load. As more complex composite features occurred in the wing, it got heavier, so feather shafts became stronger yet more lightweight, which led to stiffer feathers and sturdy wings that powered flight to carry birds around the world.

"Our findings suggest the evolutionary trends of feather shaft and vane are balanced for the best flight performance of an individual bird and become part of the selective basis of speciation," the study says. "The principles of functional architectures we studied here may also stimulate bio-inspired designs and fabrication of future composite materials for architectures of different scales, including wind turbines, artificial tissues, flying drones."

Source: University of Southern California [November 27, 2019]

* This article was originally published here

2019 November 30 Star Trails for a Red Planet Image Credit...

2019 November 30

Star Trails for a Red Planet
Image Credit & Copyright: Dengyi Huang

Explanation: Does Mars have a north star? In long exposures of Earth’s night sky, star trails make concentric arcs around the north celestial pole, the direction of our fair planet’s axis of rotation. Bright star Polaris is presently the Earth’s North Star, close on the sky to Earth’s north celestial pole. But long exposures on Mars show star trails too, concentric arcs about a celestial pole determined by Mars’ axis of rotation. Tilted like planet Earth’s, the martian axis of rotation points in a different direction in space though. It points to a place on the sky between stars in Cygnus and Cepheus with no bright star comparable to Earth’s north star Polaris nearby. So even though this ruddy, weathered landscape is remarkably reminiscent of terrain in images from the martian surface, the view must be from planet Earth, with north star Polaris near the center of concentric star trails. The landforms in the foreground are found in Qinghai Province in northwestern China.

∞ Source: apod.nasa.gov/apod/ap191130.html

* This article was originally published here

Castlehowe Scar Prehistoric Stone Circle, Shap, Cumbria, 30.11.19.

Castlehowe Scar Prehistoric Stone Circle, Shap, Cumbria, 30.11.19.

* This article was originally published here

Iron Age site discovered in Oman

Archaeologists discovered an Iron Age settlement and burial site with 45 tombs in Oman’s Al Sharqiyah governorate.

Iron Age site discovered in Oman
Credit: Omani Ministry of Heritage and Culture
Oman’s Ministry of Heritage and Culture, working with Germany’s Heidelberg University on a project to study Iron Age settlements in North Al Sharqiyah found the new site in Al Mudhaibi. The ministry said the tombs are “very well preserved” and cover a 50 to 80-square metre area.

The tombs are 700 metres from a settlement that the team believes dates from the beginning of the Iron Age and may have been home to people who worked in copper mining.

It is believed there was copper mining at the site during the Iron Age and continued until early in the Islamic era.

Iron Age site discovered in Oman
Credit: Omani Ministry of Heritage and Culture
“It is the most preserved sites of its components, where stone buildings and tombs resembling huts are retained by nature for more than 3,000 years, and reflect the method of burial,” the Ministry of Heritage and Culture said.

“It features the social status of the deceased through the length of the tomb and archaeological artefacts buried with him.”

Al Sharqiyah site is one of many archaeological finds discovered in Oman over the past decade. Many were discovered by a team from the archaeology department at Sultan Qaboos University, which works with the Ministry of Heritage and Culture to find, protect and preserve sites of interest.

Iron Age site discovered in Oman
Credit: Omani Ministry of Heritage and Culture
Oman’s ancient sites have also been recognised by the UN. In 1988, Bat, Al Khutm and Al Ayn were certified as World Heritage Sites. The three ancient settlements in Al Dhahira Governorate of north-west Oman are the most complete of their kind from the Iron Age.

In January 2018, the largest trove of Iron Age weapons in the region was discovered at Mudhmar East. It contained more than 3,000 arrows, daggers and axes.

Author: Taylor Heyman | Source: The National [November 26, 2019]

* This article was originally published here

Space Station Science Highlights: Week of November 25, 2019

ISS - Expedition 61 Mission patch.

Nov. 29, 2019

Current scientific research conducted aboard the International Space Station includes investigations on maintaining human health in space, the body’s circatidal cycle and growing moss in microgravity. Crew members prepared for the third in a series of spacewalks to repair the Alpha Magnetic Spectrometer (AMS-02), scheduled to be conducted by Luca Parmitano of the ESA (European Space Agency) and NASA’s Andrew Morgan on Dec. 2. In addition, the crew made ready for the arrival of additional scientific experiments aboard the 19th SpaceX Commercial Resupply Services (CRS-19), scheduled to blast off from Cape Canaveral Air Force Station, Florida, on Dec. 4, 2019.

Image above: NASA astronaut Christina Koch and ROSCOSMOS cosmonaut Oleg Skripochka assisted NASA astronaut Andrew Morgan and ESA astronaut Luca Parmitano with their second spacewalk to repair the Alpha Magnetic Spectrometer. Image Credit: NASA.

The space station is now in its 20th year of continuous human presence. Learning to live and work in space is one of the biggest challenges of long-duration spaceflight, and experience gained on the space station supports Artemis, NASA’s program to go forward to the Moon and on to Mars.

Here are details on some of the science under way on the orbiting lab:

Measuring how the body adapts to space

Standard Measures captures an ongoing, optimized set of measures from crew members in order to characterize how their bodies adapt to living in space. Ground teams perform analyses for metabolic and chemistry panels, immune function, microbiome, and other measures to create a repository of the data. This repository enables high-level monitoring of the effectiveness of countermeasures and more meaningful interpretation of health and performance outcomes. The investigation also supports future research on planetary missions. The crew performed pre-sleep questionnaire data collection.

Testing microgravity’s effects on the 12-hour body clock

Image above: This image taken from the space station shows the Mediterranean Sea looking toward the Gulf of Suez. Scientists use images of Earth such as this one for research in a variety of fields. Image Credit: NASA.

Throughout the week, crew members performed Rodent Research-14 science sessions. This investigation uses mice to examine the effects of microgravity on the body’s circatidal rhythm or sleep/wake cycle on a cellular and key organ level. The body’s 12-hour clock is an important mechanism for controlling stress-responsive pathways. The space station makes it possible to expose cellular systems in mice to the stress of microgravity and study both cellular adaptation and organismal behavior responses to that stress.

Tiny plants, big potential

Image above: These Mizuna mustard greens growing aboard the International Space Station support development of food production in space agriculture to provide fresh food for crews on deep space missions. The Veg-04B investigation focuses on the effects of red-to-blue lighting on the plants. Image Credit: NASA.

The Japan Aerospace Exploration Agency (JAXA) Space Moss investigation grows mosses aboard the space station, and simultaneously on Earth, to determine how microgravity affects their growth, development, gene expression, photosynthetic activity and other features. Tiny plants without roots, mosses grow in a very small area, which represents an advantage for their potential use on long space voyages and future bases on the Moon or Mars. Crew members prepped the Plant Observation Dishes, which incubate for one, two and three days and then are placed in the JAXA Fluorescence Microscope for observation. Teams on the ground control all observations and downlink image data.

Other investigations on which the crew performed work:

- Analog-1 tests operating an exploration rover on Moon-like terrain on Earth from the space station. It is part of the METERON project, an ESA (European Space Agency) initiative to help prepare for human-robotic exploration on future missions.

- Food Acceptability examines changes in the appeal of food aboard the space station during long-duration missions. “Menu fatigue” from repeatedly consuming a limited choice of foods may contribute to the loss of body mass often experienced by crew members, potentially affecting astronaut health, especially as mission length increases.

- Veg-04B, part of a phased research project to address the need for fresh food production in space, focuses on the effects of light quality and fertilizer on a leafy crop, Mizuna mustard greens. The final harvest for this investigation occurred on Thanksgiving Day, Nov. 28.

- NutrISS, an investigation by the Italian Space Agency (ASI), assesses the body composition of crew members during spaceflight using a device that measures long-term energy balance modification over time. Adjusting diet to maintain a near-neutral energy balance and/or increasing protein intake may limit microgravity-induced bone and muscle loss.

2225 views   52 likes   6 dislikes  

Channel: Terry's Theories  

This video was taken by an ROV (remotely operated vehicle) at a depth of 3753 ft in the Indian Ocean within close proximity to a drill wellhead.This video was taken off the East coast of Africa.This video was taken by CaptanJRD
Source video https://www.youtube.com/watch?v=BaX6BK66v9A

Video length: 2:28
Category: Science & Technology

Oracle Bones for Divination, Shang Dynasty, The National Museum of Scotland, Edinburgh, 24.11.19.

Oracle Bones for Divination, Shang Dynasty, The National Museum of Scotland, Edinburgh, 24.11.19.

* This article was originally published here

The CleanSpace One Selected by ESA

ClearSpace logo / EPFL - Space Center - eSpace logo.

Nov. 29, 2019

ClearSpace, a Swiss start-up, spin-off of the EPFL Space Center (eSpace), wants to clean up nearby Space (Low Earth Orbit), which is starting to be seriously cluttered with old, broken satellites and debris of all kinds.

The CleanSpace One Project. The space cleanup satellite will deploy a conical net to capture the small SwissCube satellite before destroying it in the atmosphere. It’s one of the solutions being tested for eliminating dangerous debris orbiting the Earth.

"There has been much debate among scientists about what conditions led to this extinction event," said lead author Dr Frederik Saltre, Research Fellow and Coordinator of the Global Ecology Lab at Flinders University.

"Resolving this question is important because it is one of the oldest such extinction events anywhere after modern human beings evolved and left Africa", he added.

The findings, published in Nature Communications, are the result of analysis and complex modelling based on data including more than 10,000 fossils and archaeological records. Using high-quality fossil data and archaeological evidence of human activity, the researchers were able to map regional patterns of megafauna extinction.

They developed sophisticated models to test the impact of factors including climate, water availability, and human activity on localised patterns of megafauna extinction.

People and climate led to Australia's megafauna extinction
Credit: Flinders University
The extinction pattern could only be explained by the combination of people sharing the environment and the reduced of availability of freshwater due to climate change.

"The regional patterns in extinction are best explained by the hypothesis that people migrated across Australia, exploiting lakes and other sources of drinking water connecting the drier regions in between," said co-investigator Professor Corey Bradshaw of the Global Ecology Lab at Flinders University.

"It is plausible that megafauna species were attracted to the same freshwater sources as humans, thus increasing the chance of interactions."

The new insight that human pressure and climate change work together to trigger species extinction is a "stark warning" for the immediate future of the planet's biodiversity facing even stronger climate and habitat disruption, Dr Saltre concluded.

Source: Flinders University [November 27, 2019]

* This article was originally published here


494 views   16 likes   0 dislikes  

Channel: Terry's Theories  


Video length: 3:28
Category: Science & Technology

10 Questions You Might Have About Black Holes

NASA logo.

November 29, 2019

A black hole is an extremely dense object in space from which no light can escape. While black holes are mysterious and exotic, they are also a key consequence of how gravity works: When a lot of mass gets compressed into a small enough space, the resulting object rips the very fabric of space and time, becoming what is called a singularity. A black hole's gravity is so powerful that it will be able to pull in nearby material and "eat" it.7

Image above: This artist concept illustrates a supermassive black hole with millions to billions times the mass of our Sun. Supermassive black holes are enormously dense objects buried at the hearts of galaxies. Image credits: NASA/JPL-Caltech.

Here are 10 things you might want to know about black holes:

Image above: Galaxy NGC 1068 is shown in visible light and X-rays in this composite image. High-energy X-rays (magenta) captured by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, are overlaid on visible-light images from both NASA's Hubble Space Telescope and the Sloan Digital Sky Survey. The X-ray light is coming from an active supermassive black hole, also known as a quasar, in the center of the galaxy. This supermassive black hole has been extensively studied due to its relatively close proximity to our galaxy. Image Credits: NASA/JPL-Caltech/Roma Tre Univ.

1. How can we learn about black holes if they trap light, and can't actually be seen?

No light of any kind, including X-rays, can escape from inside the event horizon of a black hole, the region beyond which there is no return. NASA's telescopes that study black holes are looking at the surrounding environments of the black holes, where there is material very close to the event horizon. Matter is heated to millions of degrees as it is pulled toward the black hole, so it glows in X-rays. The immense gravity of black holes also distorts space itself, so it is possible to see the influence of an invisible gravitational pull on stars and other objects.

Image above: In 2015, researchers discovered a black hole named CID-947 that grew much more quickly than its host galaxy. The black hole at the galaxy’s center is nearly 7 billion times the mass of our Sun, placing it among the most massive black holes discovered. The galaxy’s mass, however, is considered normal. Because its light had to travel a very long distance, scientists were observing it at a period when the universe was less than 2 billion years old, just 14% of its current age (almost 14 billion years have passed since the Big Bang). Image credits: M. Helfenbein, Yale University / OPAC.

2. How long does it take to make a black hole?

A stellar-mass black hole, with a mass of tens of times the mass of the Sun, can likely form in seconds, after the collapse of a massive star. These relatively small black holes can also be made through the merger of two dense stellar remnants called neutron stars. A neutron star can also merge with a black hole to make a bigger black hole, or two black holes can collide. Mergers like these also make black holes quickly, and produce ripples in space-time called gravitational waves.

More mysterious are the giant black holes found at the centers of galaxies — the "supermassive" black holes, which can weigh millions or billions of times the mass of the Sun. It can take less than a billion years for one to reach a very large size, but it is unknown how long it takes them to form, generally.

Image above: Scientists obtained the first image of a black hole, seen here, using Event Horizon Telescope observations of the center of the galaxy M87. The image shows a bright ring formed as light bends due to the intense gravity around a black hole that is 6.5 billion times more massive than our Sun. Image credits: Event Horizon Telescope Collaboration.

3. How do scientists calculate the mass of a supermassive black hole?

The research involves looking at the motions of stars in the centers of galaxies. These motions imply a dark, massive body whose mass can be computed from the speeds of the stars. The matter that falls into a black hole adds to the mass of the black hole. Its gravity doesn't disappear from the universe.

Image above: This animation illustrates the activity surrounding a black hole. While the matter that has passed the black hole's event horizon can't be seen, material swirling outside this threshold is accelerated to millions of degrees and radiates in X-rays. Image credits: CXC/A.Hobart.

4. Is it possible for a black hole to "eat" an entire galaxy?

No. There is no way a black hole would eat an entire galaxy. The gravitational reach of supermassive black holes contained in the middle of galaxies is large, but not nearly large enough for eating the whole galaxy.

Image above: This illustration shows a glowing stream of material from a star disrupted as it was being devoured by a supermassive black hole. The black hole is surrounded by a ring of dust. When a star passes close enough to be swallowed by a black hole, the stellar material is stretched and compressed as it is pulled in, releasing an enormous amount of energy. Image credits: NASA/JPL-Caltech.

5. What would happen if you fell into a black hole?

It certainly wouldn't be good! But what we know about the interior of black holes comes from Albert Einstein's General Theory of Relativity.

For black holes, distant observers will only see regions outside the event horizon, but individual observers falling into the black hole would experience quite another "reality." If you got into the event horizon, your perception of space and time would entirely change. At the same time, the immense gravity of the black hole would compress you horizontally and stretch you vertically like a noodle, which is why scientists call this phenomenon (no joke) "spaghettification."

Fortunately, this has never happened to anyone — black holes are too far away to pull in any matter from our solar system. But scientists have observed black holes ripping stars apart, a process that releases a tremendous amount of energy.

Image above: NASA’s Chandra X-ray observatory detected record-breaking wind speeds coming from a disk around a black hole. This artist's impression shows how the strong gravity of the black hole, on the left, is pulling gas away from a companion star on the right. This gas forms a disk of hot gas around the black hole, and the wind is driven off this disk at 20 million mph, or about 3% the speed of light. Image credits: NASA/CXC/M.Weiss.

6. What if the Sun turned into a black hole?

The Sun will never turn into a black hole because it is not massive enough to explode. Instead, the Sun will become a dense stellar remnant called a white dwarf.

But if, hypothetically, the Sun suddenly became a black hole with the same mass as it has today, this would not affect the orbits of the planets, because its gravitational influence on the solar system would be the same. So, Earth would continue to revolve around the Sun without getting pulled in — although the lack of sunlight would be disastrous for life on Earth.

Image above: The central region of our galaxy, the Milky Way, contains an exotic collection of objects, including a supermassive black hole, called Sagittarius A*, weighing about 4 million times the mass of the Sun, clouds of gas at temperatures of millions of degrees, neutron stars and white dwarf stars tearing material from companion stars and beautiful tendrils of radio emission. The region around Sagittarius A* is shown in this composite image with Chandra data (green and blue) combined with radio data (red) from the MeerKAT telescope in South Africa, which will eventually become part of the Square Kilometer Array (SKA). Image credits: X-Ray: NASA/CXC/UMass/D. Wang et al.; Radio: SARAO/MeerKAT.

7. Have black holes had any influence on our planet?

Stellar-mass black holes are left behind when a massive star explodes. These explosions distribute elements such as carbon, nitrogen and oxygen that are necessary for life into space. Mergers between two neutron stars, two black holes, or a neutron star and black hole, similarly spread heavy elements around that may someday become part of new planets. The shock waves from stellar explosions may also trigger the formation of new stars and new solar systems. So, in some sense, we owe our existence on Earth to long-ago explosions and collision events that formed black holes.

On a larger scale, most galaxies seem to have supermassive black holes at their centers. The connection between the formation of these supermassive black holes and the formation of galaxies is still not understood. It is possible that a black hole could have played a role in the formation of our Milky Way galaxy. But this chicken-and-egg problem — that is, which came first, the galaxy or the black hole? — is one of the great puzzles of our universe.

Image above: This artist's concept shows the most distant supermassive black hole ever discovered. It is part of a quasar from just 690 million years after the Big Bang. Image credits: Robin Dienel/Carnegie Institution for Science.

8. What is the most distant black hole ever seen?

The most distant black hole ever detected is located in a galaxy about 13.1 billion light-years from Earth. (The age of the universe is currently estimated to be about 13.8 billion years, so this means this black hole existed about 690 million years after the Big Bang.)

This supermassive black hole is what astronomers call a “quasar,” where large quantities of gas are pouring into the black hole so rapidly that the energy output is a thousand times greater than that of the galaxy itself. Its extreme brightness is how astronomers can detect it at such great distances.

Image above: The central region of this image contains the highest concentration of supermassive black holes ever seen and about a billion over the entire sky. Made with over 7 million seconds of Chandra observing time, this 2017 image is part of the Chandra Deep Field-South. With its unprecedented look at the early universe in X-rays, it offers astronomers a look at the growth of black holes over billions of years starting soon after the Big Bang. In this image, low, medium and high-energy X-rays that Chandra detects are shown as red, green, and blue respectively. Image credits: NASA/CXC/Penn State/B.Luo et al.

9. If nothing can escape from a black hole, then won't the whole universe eventually be swallowed up?

The universe is a big place. In particular, the size of a region where a particular black hole has significant gravitational influence is quite limited compared to the size of a galaxy. This applies even to supermassive black holes like the one found in the middle of the Milky Way. This black hole has probably already "eaten" most or all of the stars that formed nearby, and stars further out are mostly safe from being pulled in. Since this black hole already weighs a few million times the mass of the Sun, there will only be small increases in its mass if it swallows a few more Sun-like stars. There is no danger of the Earth (located 26,000 light years away from the Milky Way's black hole) being pulled in.

Future galaxy collisions will cause black holes to grow in size, for example by merging of two black holes. But collisions won't happen indefinitely because the universe is big and because it's expanding, and so it's very unlikely that any sort of black hole runaway effect will occur.

Image above: In this illustration of a black hole and its surrounding disk, gas spiraling toward the black hole piles up just outside it, creating a traffic jam. The traffic jam is closer in for smaller black holes, so X-rays are emitted on a shorter timescale. Image credit: NASA.

10. Can black holes get smaller?

Yes. The late physicist Stephen Hawking proposed that while black holes get bigger by eating material, they also slowly shrink because they are losing tiny amounts of energy called "Hawking radiation."

Hawking radiation occurs because empty space, or the vacuum, is not really empty. It is actually a sea of particles continually popping into and out of existence. Hawking showed that if a pair of such particles is created near a black hole, there is a chance that one of them will be pulled into the black hole before it is destroyed. In this event, its partner will escape into space. The energy for this comes from the black hole, so the black hole slowly loses energy, and mass, by this process.

Hawking radiation

Eventually, in theory, black holes will evaporate through Hawking radiation. But it would take much longer than the entire age of the universe for most black holes we know about to significantly evaporate. Black holes, even the ones around a few times the mass of the Sun, will be around for a really, really long time!