A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of the region from which no escape is possible is called the event horizon. Although the event horizon has an enormous effect on the fate and circumstances of an object crossing it, no locally detectable features appear to be observed. In many ways a black hole acts like an ideal black body, as it reflects no light.
The idea of a body so massive that even light could not escape was briefly proposed by astronomical pioneer and English clergyman John Michell in a letter published in November 1784. Michell’s simplistic calculations assumed that such a body might have the same density as the Sun, and concluded that such a body would form when a star’s diameter exceeds the Sun’s by a factor of 500, and the surface escape velocity exceeds the usual speed of light.
At the center of a black hole, as described by general relativity, lies a gravitational singularity, a region where the spacetime curvature becomes infinite. For a non-rotating black hole, this region takes the shape of a single point and for a rotating black hole, it is smeared out to form a ring singularity that lies in the plane of rotation. In both cases, the singular region has zero volume. It can also be shown that the singular region contains all the mass of the black hole solution. The singular region can thus be thought of as having infinite density.
Scientists think the smallest black holes formed when the universe began.
Stellar black holes are made when the center of a very big star falls in upon itself, or collapses. When this happens, it causes a supernova. A supernova is an exploding star that blasts part of the star into space.
Scientists think supermassive black holes were made at the same time as the galaxy they are in.
Supermassive black holes, which can have a mass equivalent to billions of suns, likely exist in the centers of most galaxies, including our own galaxy, the Milky Way. We don’t know exactly how supermassive black holes form, but it’s likely that they’re a byproduct of galaxy formation. Because of their location in the centers of galaxies, close to many tightly packed stars and gas clouds, supermassive black holes continue to grow on a steady diet of matter.
A black hole can not be seen because strong gravity pulls all of the light into the middle of the black hole. But scientists can see how the strong gravity affects the stars and gas around the black hole.
Scientists can study stars to find out if they are flying around, or orbiting, a black hole.
When a black hole and a star are close together, high-energy light is made. This kind of light can not be seen with human eyes. Scientists use satellites and telescopes in space to see the high-energy light.
On 11 February 2016, the LIGO collaboration announced the first observation of gravitational waves; because these waves were generated from a black hole merger it was the first ever direct detection of a binary black hole merger. On 15 June 2016, a second detection of a gravitational wave event from colliding black holes was announced.
Simulation of gravitational lensing by a black hole, which distorts the image of a galaxy in the background
Animated simulation of gravitational lensing caused by a black hole going past a background galaxy. A secondary image of the galaxy can be seen within the black hole Einstein ring on the opposite direction of that of the galaxy. The secondary image grows (remaining within the Einstein ring) as the primary image approaches the black hole. The surface brightness of the two images remains constant, but their angular size varies, hence producing an amplification of the galaxy luminosity as seen from a distant observer. The maximum amplification occurs when the background galaxy (or in the present case a bright part of it) is exactly behind the black hole.
Black holes do not go around in space eating stars, moons and planets. Earth will not fall into a black hole because no black hole is close enough to the solar system for Earth to do that.
Even if a black hole the same mass as the sun were to take the place of the sun, Earth still would not fall in. The black hole would have the same gravity as the sun. Earth and the other planets would orbit the black hole as they orbit the sun now.
The sun will never turn into a black hole. The sun is not a big enough star to make a black hole.
More posts about black holes
Source 1, 2 & 3
“Dark matter should drive the formation of structure on all large scales, with every galaxy consisting of a large, diffuse halo of dark matter that is far less dense and more diffuse than the normal matter. While the normal matter clumps and clusters together, since it can stick together and interact, dark matter simply passes through both itself and normal matter. Without dark matter, the Universe wouldn’t match our observations.
But this branch of science truly got its start with the revolutionary work of Vera Rubin. While many, including me, will deride the Nobel committee for snubbing her revolutionary science, she truly did change the Universe. On what would have been her 91st birthday, remember her in her own words:
“Don’t let anyone keep you down for silly reasons such as who you are, and don’t worry about prizes and fame. The real prize is finding something new out there.”
50 years later, we’re still investigating the mystery Vera Rubin uncovered. May there always be more to learn.”
Today, dark matter is practically accepted as a given, owing to an overwhelming suite of evidence that points to its existence. Without adding dark matter as an ingredient, we simply can’t explain the Universe, from gravitational lensing to large-scale structure to Big Bang nucleosynthesis to the cosmic microwave background and much more. But throughout the 1930s, 40s and 50s, no one would even give the idea a second thought. Until, that is, Vera Rubin came along and changed everything.
Today would have been her 91st birthday, and it’s about time you got the scientific story to celebrate what she taught us all.
Now that the MarCOs — a pair of briefcase-sized interplanetary CubeSats — seem to have reached their limit far beyond Mars, we’re looking forward to an expanding era of small, versatile and powerful space-based science machines.
Here are ten ways we’re pushing the limits of miniaturized technology to see just how far it can take us.
MarCO, short for Mars Cube One, was the first interplanetary mission to use a class of mini-spacecraft called CubeSats.
The MarCOs — nicknamed EVE and WALL-E, after characters from a Pixar film — served as communications relays during InSight’s November 2018 Mars landing, beaming back data at each stage of its descent to the Martian surface in near-real time, along with InSight’s first image.
WALL-E sent back stunning images of Mars as well, while EVE performed some simple radio science.
All of this was achieved with experimental technology that cost a fraction of what most space missions do: $18.5 million provided by NASA’s Jet Propulsion Laboratory in Pasadena, California, which built the CubeSats.
WALL-E was last heard from on Dec. 29; EVE, on Jan. 4. Based on trajectory calculations, WALL-E is currently more than 1 million miles (1.6 million kilometers) past Mars; EVE is farther, almost 2 million miles (3.2 million kilometers) past Mars.
MarCO-B took these images as it approached Mars in November 2018. Credit: NASA/JPL-Caltech
CubeSats were pioneered by California Polytechnic State University in 1999 and quickly became popular tools for students seeking to learn all aspects of spacecraft design and development.
Today, they are opening up space research to public and private entities like never before. With off-the-shelf parts and a compact size that allows them to hitch a ride with other missions — they can, for example, be ejected from the International Space Station, up to six at a time — CubeSats have slashed the cost of satellite development, opening up doors to test new instruments as well as to create constellations of satellites working together.
CubeSats can be flown in swarms, capturing simultaneous, multipoint measurements with identical instruments across a large area. Sampling entire physical systems in this way would drive forward our ability to understand the space environment around us, in the same way multiple weather sensors help us understand global weather systems.
Ready to get started? Check out NASA’s CubeSats 101 Guide.
Engineer Joel Steinkraus uses sunlight to test the solar arrays on one of the Mars Cube One (MarCO) spacecraft at NASA’s Jet Propulsion Laboratory. Credit: NASA/JPL-Caltech
The size and cost of spacecraft vary depending on the application; some are the size of a pint of ice cream while others, like the Hubble Space Telescope, are as big as a school bus.
Small spacecraft (SmallSats) generally have a mass less than 400 pounds (180 kilograms) and are about the size of a large kitchen fridge.
CubeSats are a class of nanosatellites that use a standard size and form factor. The standard CubeSat size uses a “one unit” or “1U” measuring 10x10x10 centimeters (or about 4x4x4 inches) and is extendable to larger sizes: 1.5, 2, 3, 6, and even 12U.
The Sojourner rover (seen here on Mars in 1997) is an example of small technology that pioneered bigger things. Generations of larger rovers are being built on its success.
Not unlike a CubeSat, NASA’s first spacecraft — Explorer 1 — was a small, rudimentary machine. It launched in 1958 and made the first discovery in outer space, the Van Allen radiation belts that surround Earth. It was the birth of the U.S. space program.
In 1997, a mini-rover named Sojourner rolled onto Mars, a trial run for more advanced rovers such as NASA’s Spirit, Opportunity and Curiosity.
Innovation often begins with pathfinder technology, said Jakob Van Zyl, director of the Solar System Exploration Directorate at NASA’s Jet Propulsion Laboratory. Once engineers prove something can be done, science missions follow.
NASA is continually developing new technologies — technologies that are smaller than ever before, components that could improve our measurements, on-board data processing systems that streamline data retrievals, or new methods for gathering observations. Each new technology is thoroughly tested in a lab, sometimes on aircraft, or even at remote sites across the world. But the space environment is different than Earth. To know how something is going to operate in space, testing in space is the best option.
Sending something unproven to orbit has traditionally been a risky endeavor, but CubeSats have helped to change that. The diminutive satellites typically take less than two years to build. CubeSats are often a secondary payload on many rocket launches, greatly reducing cost. These hitchhikers can be deployed from a rocket or sent to the International Space Station and deployed from orbit.
Because of their quick development time and easy access to space, CubeSats have become the perfect platform for demonstrating how a new technological advancement will perform in orbit.
RainCube is a mini weather satellite, no bigger than a shoebox, that will measure storms. It’s part of several new NASA experiments to track storms from space with many small satellites, instead of individual, large ones. Credit: UCAR
A few recent examples from our home world:
RainCube, a satellite no bigger than a suitcase, is a prototype for a possible fleet of similar CubeSats that could one day help monitor severe storms, lead to improving the accuracy of weather forecasts and track climate change over time.
IceCube tested instruments for their ability to make space-based measurements of the small, frozen crystals that make up ice clouds. Like other clouds, ice clouds affect Earth’s energy budget by either reflecting or absorbing the Sun’s energy and by affecting the emission of heat from Earth into space. Thus, ice clouds are key variables in weather and climate models.
Rocket Lab’s Electron rocket lifts off from Launch Complex 1 for the NASA ELaNa19 mission. Credit: Trevor Mahlmann/Rocket Lab
A series of new CubeSats is now in space, conducting a variety of scientific investigations and technology demonstrations following a Dec. 17, 2018 launch from New Zealand — the first time CubeSats have launched for NASA on a rocket designed specifically for small payloads.
This mission included 10 Educational Launch of Nanosatellites (ELaNa)-19 payloads, selected by NASA’s CubeSat Launch Initiative:
CubeSat Compact Radiation Belt Explorer (CeREs) — High energy particle measurement in Earth’s radiation belt
Simulation-to-Flight 1 (STF-1) — Software condensing to support CubeSat implementations
Advanced Electrical Bus (ALBus) — Advances in solar arrays and high capacity batteries
CubeSat Handling Of Multisystem Precision Time Transfer (CHOMPTT) — Navigation plans for exo-planetary implementation
CubeSail — Deployment and control of a solar sail blade
NMTSat — Magnetic field, high altitude plasma density
Rsat — Manipulation of robotic arms
Ionospheric Scintillation Explorer (ISX) — Plasma fluctuations in the upper atmosphere
Shields-1 — Radiation shielding
DaVinci — High School to Grade School STEM education
CubeSat technology is still in its infancy, with mission success rates hovering near 50 percent. So, a team of scientists and engineers set out on a quest. Their goal? To build a more resilient CubeSat — one that could handle the inevitable mishaps that bedevil any spacecraft, without going kaput.
They wanted a little CubeSat that could.
They got to work in 2014 and, after three years of development, Dellingr was ready to take flight.
Read the Full Story: Dellingr: The Little CubeSat That Could
Artist’s concept of Lunar Flashlight. Credit: NASA
There are a handful of proposed NASA missions could take CubeSat technology farther:
CUVE would travel to Venus to investigate a longstanding mystery about the planet’s atmosphere using ultraviolet-sensitive instruments and a novel, carbon-nanotube light-gathering mirror.
Lunar Flashlight would use a laser to search for water ice in permanently shadowed craters on the south pole of Earth’s Moon.
Near-Earth Asteroid Scout, a SmallSat, would use a solar sail to propel it to do science on asteroids that pass close to Earth.
All three spacecraft would hitch rides to space with other missions, a key advantage of these compact science machines.
Expedition 56 Flight Engineer Serena Auñón-Chancellor installs the NanoRacks Cubesat Deployer-14 (NRCSD-14) on the Multipurpose Experiment Platform inside the Japanese Kibo laboratory module. The NRCSD-14 was then placed in the Kibo airlock and moved outside of the space station to deploy a variety of CubeSats into Earth orbit. Credit: NASA
Even if they’re never revived, the team considers MarCO a spectacular success.
A number of the critical spare parts for each MarCO will be used in other CubeSat missions. That includes their experimental radios, antennas and propulsion systems. Several of these systems were provided by commercial vendors, making it easier for other CubeSats to use them as well.
More small spacecraft are on the way. NASA is set to launch a variety of new CubeSats in coming years.
“There’s big potential in these small packages,” said John Baker, the MarCO program manager at JPL. “CubeSats — part of a larger group of spacecraft called SmallSats — are a new platform for space exploration affordable to more than just government agencies.”
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You know what the Mexicans say about the Pacific? They say it has no memory. That’s where I want to live the rest of my life. A warm place with no memory. Open up a little hotel right on the beach. Buy some worthless old boat and fix it up new. Take my guests out charter fishing. Zihuatanejo. In a place like that, I could use a man that knows how to get things.
The Shawshank Redemption (1994) dir. Frank Darabont
He faced all this for you, for you to be loved, blessed, glorified, exalted, satisfied, accepted, freed and resurrected.
(Source)
‘’A God’s Eye View of the Universe’‘
Credit: SpaceRip
When we think about what makes a planet habitable, we’re often talking about water. With abundant water in liquid, gas (vapor) and solid (ice) form, Earth is a highly unusual planet. Almost 70% of our home planet’s surface is covered in water!
But about 97% of Earth’s water is salty – only a tiny amount is freshwater: the stuff humans, pets and plants need to survive.
Water on our planet is constantly moving, and not just geographically. Water shifts phases from ice to water to vapor and back, moving through the planet’s soils and skies as it goes.
That’s where our satellites come in.
Look at the Midwestern U.S. this spring, for example. Torrential rain oversaturated the soil and overflowed rivers, which caused severe flooding, seen by Landsat.
Our satellites also tracked a years-long drought in California. Between 2013 and 2014, much of the state turned brown, without visible green.
It’s not just rain. Where and when snow falls – and melts – is changing, too. The snow that falls and accumulates on the ground is called snowpack, which eventually melts and feeds rivers used for drinking water and crop irrigation. When the snow doesn’t fall, or melts too early, communities go without water and crops don’t get watered at the right time.
Even when water is available, it can become contaminated by blooms of phytoplankton, like cyanobacteria . Also known as blue-green algae, these organisms can make humans sick if they drink the water. Satellites can help track algae from space, looking for the brightly colored blooms against blue water.
Zooming even farther back, Earth’s blue water is visible from thousands of miles away. The water around us makes our planet habitable and makes our planet shine blue among the darkness of space.
Knowing where the water is, and where it’s going, helps people make better decisions about how to manage it. Earth’s climate is changing rapidly, and freshwater is moving as a result. Some places are getting drier and some are getting much, much wetter. By predicting droughts and floods and tracking blooms of algae, our view of freshwater around the globe helps people manage their water.
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In October 1980 the Voyager probe discovered three small moons of Saturn, Pandora, Atlas and Prometheus. (source & images)