Showing posts with label galaxies. Show all posts
Showing posts with label galaxies. Show all posts

Sunday, December 11, 2016

Erik Verlinde's New Theory Of Gravity Tries To Explain Dark Matter

Collage of six cluster collisions with dark matter maps. The clusters were observed in a study of how dark matter in clusters of galaxies behaves when the clusters collide Photo: wikipedia.org
Although gravity is the most familiar force of the universe, it is a thorny problem for theoretical physicists as it has long defied its inclusion in quantum mechanics. Another problem is dark matter only interacts with gravity and also defies the standard model of particle physics.

Professor Erik Verlinde, a researcher from the Delta Institute for Theoretical Physics in Amsterdam, believes that gravity is not an actual force of the universe but an effect due to the increasing entropy of the universe. In his latest paper, which is available on arXiv but is yet to be peer-reviewed, the scientist claimed that this “emergent” (and not real) force of gravity has a dark component that behaves like dark matter.


Mysterious Universe: Super Force Mysterious Universe

Photo: quantumdiaries.org

"We have evidence that this new view of gravity actually agrees with the observations," said Verlinde in a statement. "At large scales, it seems, gravity just doesn't behave the way Einstein's theory predicts."



Erik Verlinde, Theoretical Physicist at Amsterdam

Quite the bold statement from the researcher, especially since it has been shown that Einstein’s general relativity agrees quite well with large-scale observations. In the paper, Verlinde admits that the idea of this dark gravitational component needs to answer several questions before it is able to be as successful at explaining the early universe and large scale cosmology as the current theory of gravity.


The theory of entropic gravity was first proposed by Verlinde in a paper in 2010 and published in the Journal of High Energy Physics in 2011. The proposed idea was welcomed by some as a novel approach to the problem of gravity in quantum mechanics.


Verlinde's new theory of gravity passes first test Phys.org

Others were more skeptical and devised ways to see if gravity could really be an emergent phenomenon. In 2011, Archil Kobakhidze of the University of Melbourne looked at how gravity affects fundamental particles. His findings strongly support the idea that gravity is a real force.

Entropic gravity is appealing because it is able to reproduce the laws of Newtonian gravitation and Einstein field equations from the first thermodynamics and quantum mechanical principles, but the theory itself doesn’t make predictions so it can’t be falsified.

Einstein’s general relativity is constantly being tested, and discoveries like gravitational waves have only strengthened its role as the best theory of gravity we currently possess.


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The above post is reprinted from materials provided by IFL Science . Note: Materials may be edited for content and length.

Friday, December 9, 2016

Astronomers issued a shocking theory about the universe: 'The Universe is Flat!'



































The local geometry of the universe is determined by whether the density parameter Ω is greater than, less than, or equal to 1.


From top to bottom: a spherical universe with Ω > 1, a hyperbolic universe with Ω < 1, and a flat universe with Ω = 1. Note that these depictions of two-dimensional surfaces are merely easily visualizable analogs to the 3-dimensional structure of (local) space. photo: wikipedia.org

The universe is flat, has said recently, but there are many subtleties behind this assertion. How can we tell the Universe form? It means that a 3D object to be flat? May be other interesting things to say?

Hubble Eyes Hanny's Voorwerp - Universe Today

For starters, we must define the notion of "flat". Screen that look is flat and the earth is curved, for example, but we can calculate mathematically how this? A plausible answer refers to the parallel lines, for as you draw two parallel on a sheet of paper and will continue, they will be forever parallel, it is the more common definition of parallel lines. 



43K Galaxies: Most Complete 3D Map of the Universe Ever

However, this exercise must be repeated in relation to the Earth's surface, each heading towards the north, and the shape of the curve of the Earth makes them meet at a time. Earth curbaţiei opposite that of a saddle, the surface of which parallel lines move away from each other. So you can measure "flat" structure using only parallels.


Slices through the Sloan Digital Sky Survey 3-dimensional map of the distribution of galaxies with the Earth at the center, an example of an experimental attempt to catalog the observable universe. photo: wikipedia.org

However, determining the shape of the universe is a matter of cosmology, and he has a plurality of deformation, there are masses of energy and there is a close correlation between time and space. Have you ever wondered what the difference between a sphere and a cylinder? Use your schools which have drawn two parallel lines and manufactured a cylinder. Meanwhile observed parallel lines: they remain, indeed, parallel to the cylinder is flat.


This happens because there is a clear distinction between geometry and topography, and as he studied the geometry of the universe is very careful, not topography. But if the universe is indeed flat, this is met in a very distant place, which can not be observed by astronomers, because they never observed galaxies and the CMB identical intersecting.

The universe is flat, has said recently, but there are many subtleties behind this assertion. How can we tell the Universe form? It means that a 3D object to be flat? May be other interesting things to say?



For starters, we must define the notion of "flat". Screen that look is flat and the earth is curved, for example, but we can calculate mathematically how this? A plausible answer refers to the parallel lines, for as you draw two parallel on a sheet of paper and will continue, they will be forever parallel, it is the more common definition of parallel lines. However, this exercise must be repeated in relation to the Earth's surface, each heading towards the north, and the shape of the curve of the Earth makes them meet at a time. Earth curbaţiei opposite that of a saddle, the surface of which parallel lines move away from each other. So you can measure "flat" structure using only parallels.



Mapping the Universe, containing the circular map of the universe

However, determining the shape of the universe is a matter of cosmology, and he has a plurality of deformation, there are masses of energy and there is a close correlation between time and space. Have you ever wondered what the difference between a sphere and a cylinder? Use your schools which have drawn two parallel lines and manufactured a cylinder. Meanwhile observed parallel lines: they remain, indeed, parallel to the cylinder is flat.


Mapping the Universe: Space, Time, and Discoveries


This happens because there is a clear distinction between geometry and topography, and as he studied the geometry of the universe is very careful, not topography. But if the universe is indeed flat, this is met in a very distant place, which can not be observed by astronomers, because they never observed galaxies and the CMB identical intersecting

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The above post is reprinted from materials provided by Space . Note: Materials may be edited for content and length.

Wednesday, December 7, 2016

Young galaxies "born" at least 50 stars annually: These "incubators" within young galaxies annually produce more stars than was originally estimated

photo: nasa.gov





Young galaxies in the universe appear to be very fertile and, with an annual average of 50 new stars on the size of the sun.

Updated today 21/05/2020

The recent discovery shows as "incubators" within young galaxies annually produce more stars than was originally estimated. Astronomers have "traveled" back 12.5 billion years to study one of the most remote galaxies known MS1358arc known as infant Galaxies. Light began its journey in the universe just one billion years after the creation of the cosmos, from the Big Bang.
Stars formed at much faster rate in infant galaxies Brahmand News



Bubble Worlds" --Milky Way's Star The Daily Galaxy

The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby galaxies.


Galaxy SMM J2135-0102 wallpaper - Space wallpapers - #7263 SUWalls


Galaxy formation is hypothesized to occur, from structure formation theories, as a result of tiny quantum fluctuations in the aftermath of the Big Bang

The simplest model for this that is in general agreement with observed phenomena is the Λ-Cold Dark Matter cosmology; that is to say that clustering and merging is how galaxies gain in mass, and can also determine their shape and structure.


The dark side of cosmology: Dark matter and dark energy Science


Commonly observed properties of galaxies


Because of the inability to conduct experiments in outer space, the only way to “test” theories and models of galaxy evolution is to compare them with observations. Explanations for how galaxies formed and evolved must be able to predict the observed properties and types of galaxies.

Edwin Hubble created the first galaxy classification scheme known as the Hubble tuning-fork diagram. It partitioned galaxies into ellipticals, normal spirals, barred spirals (such as the Milky Way), and irregulars. These galaxy types exhibit the following properties which can be explained by current galaxy evolution theories:


Hubble tuning fork diagram of galaxy morphology photo: wikipedia.org

Many of the properties of galaxies (including the galaxy color–magnitude diagram) indicate that there are fundamentally two types of galaxies. These groups divide into blue star-forming galaxies that are more like spiral types, and red non-star forming galaxies that are more like elliptical galaxies.

Spiral galaxies are quite thin, dense, and rotate relatively fast, while the stars in elliptical galaxies have randomly-oriented orbits.
The majority of mass in galaxies is made up of dark matter, a substance which is not directly observable, and might not interact through any means except gravity.

The majority of giant galaxies contain a supermassive black hole in their centers, ranging in mass from millions to billions of times the mass of our Sun. The black hole mass is tied to the host galaxy bulge or spheroid mass.

Lenses open precision for 10bn-year-old galaxy - Compute Scotland

Metallicity has a positive correlation with the absolute magnitude (luminosity) of a galaxy.


Hubble thought incorrectly that the tuning fork diagram described an evolutionary sequence for galaxies, from elliptical galaxies through lenticulars to spiral galaxies. However, astronomers now believe that disk galaxies likely formed first, then evolved into elliptical galaxies through galaxy mergers.

So-called "gravitational lenses" were used to enlarge the galaxy using light how "fits" on a nearby star cluster. With this technique, the researchers could observe rapid ascent generated by the formation of new stars. Thus, they could conclude that new stars are created in the galaxy at a speed 100 times higher than the average forecast initially.

With a diameter of 6000 light-years, "collection" of stars will most likely evolve into a new spiral galaxy similar to the Milky Way.


Artist image of a firestorm of star birth deep inside core of young, growing elliptical galaxy. photo: wikipedia.org
Galaxy mergers and the formation of elliptical galaxies 

Elliptical galaxies (such as IC 1101) are among some of the largest known thus far. Their stars are on orbits that are randomly oriented within the galaxy (i.e. they are not rotating like disk galaxies). A distinguishing feature of elliptical galaxies is that the velocity of the stars does not necessarily contribute to flattening of the galaxy, such as in spiral galaxies. Elliptical galaxies have supermassive black holes at their center, and the mass of these black holes correlates with the galaxy’s mass.


NGC 4676 (Mice Galaxies) is an example of a present merger. photo: wikipedia.org

Elliptical galaxies have two main stages of evolution. The first is due to the supermassive black hole increasing in size from accreting cooling gas. The second stage is marked by the black hole stabilizing by suppressing gas cooling, thus leaving the elliptical galaxy in a stable state.The mass of the black hole is also correlated to a property called sigma which is the dispersion of the velocities of stars in the elliptical galaxies. 

This relationship, known as the M-sigma relation, was discovered in 2000. Elliptical galaxies do not have disks around them, although some bulges of disk galaxies look similar to elliptical galaxies. It is more likely to find elliptical galaxies in more crowded regions of the universe (such as galaxy clusters).
Antennae Galaxies are a pair of colliding galaxies - the bright, blue knots are young stars that have recently ignited as a result of the merger. photo: wikipedia.org


Astronomers now see elliptical galaxies as some of the most evolved systems in the universe. It is widely accepted that the main driving force for the evolution of elliptical galaxies is mergers of smaller galaxies. Many galaxies in the universe are gravitationally bound to other galaxies, which means that they will never escape the pull of the other galaxy. 
ESO 325-G004, a typical elliptical galaxy. photo: wikipedia.org

If the galaxies are of similar size, the resultant galaxy will appear similar to neither of the two galaxies merging,but will instead be an elliptical galaxy. There are many types of galaxy mergers, which do not necessarily result in elliptical galaxies, but result in a change in the structure of the mergers. For example, a minor merger event is thought to be occurring between the Milky Way and the Magellanic Clouds.



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Thursday, July 28, 2016

The Milky Way's Halo Spins With The Galaxy



















Astronomers from the University of Michigan have, for the first time, measured the speed at which the Milky Way halo is rotating, a discovery that could provide new clues on how galaxies form and evolve.

Our galaxy is surrounded by a gaseous halo that extends for many hundreds of thousands of light-years from the center. It has a mass comparable to the Milky Way itself and it was believed to be still, compared to our quickly rotating galaxy.

"This flies in the face of expectations," lead author Edmund Hodges-Kluck said in a statement. "People just assumed that the disk of the Milky Way spins while this enormous reservoir of hot gas is stationary – but that is wrong. This hot gas reservoir is rotating as well, just not quite as fast as the disk."

The gas in the halo is incredibly hot, millions of degrees, but very spread out so it's difficult to estimate how quickly it's moving. The researchers had to carefully detect movement as the gas moved in front of very bright extragalactic sources, like active supermassive black holes and quasars.

In a paper published in the Astrophysical Journal, they reported that the gas is moving at about 180 kilometers per second (400,000 mph), which is only slightly slower than the rotational velocity at the rim of the Milky Way (240 km/s, 540,000 mph).

"The rotation of the hot halo is an incredible clue to how the Milky Way formed," continued Hodges-Kluck. "It tells us that this hot atmosphere is the original source of a lot of the matter in the disk."

Galaxies are believed to have formed when intergalactic materials began to fall into the large gravitational wells formed by dark matter. The rotation of the halo tells us how quickly the material must fall towards the center, and also how quickly the Milky Way came together.

"Now that we know about the rotation, theorists will begin to use this to learn how our Milky Way galaxy formed – and its eventual destiny," added Professor Joel Bregman, co-author of the study.










Source: iflscience

Tuesday, July 26, 2016

Dark Energy vs. Dark Matter: What The Universe is Made Of



Dark Energy vs. Dark Matter

While dark energy repels, dark matter attracts. And dark matter’s influence shows up even in individual galaxies, while dark energy acts only on the scale of the entire universe

Our universe may contain 100 billion galaxies, each with billions of stars, great clouds of gas and dust, and perhaps scads of planets and moons and other little bits of cosmic flotsam. The stars produce an abundance of energy, from radio waves to X-rays, which streak across the universe at the speed of light.

Yet everything that we can see is like the tip of the cosmic iceberg — it accounts for only about four percent of the total mass and energy in the universe.



About one-quarter of the universe consists of dark matter, which releases no detectable energy, but which exerts a gravitational pull on all the visible matter in the universe.

Because of the names, it’s easy to confuse dark matter and dark energy. And while they may be related, their effects are quite different. In brief, dark matter attracts, dark energy repels. While dark matter pulls matter inward, dark energy pushes it outward. Also, while dark energy shows itself only on the largest cosmic scale, dark matter exerts its influence on individual galaxies as well as the universe at large.

In fact, astronomers discovered dark matter while studying the outer regions of our galaxy, the Milky Way.


A ring of possible dark matter highlights this Hubble Space Telescope image of a distant galaxy cluster. [NASA/ESA/M.J. Jee/H. Ford (Johns Hopkins)]

The Milky Way is shaped like a disk that is about 100,000 light-years across. The stars in this disk all orbit the center of the galaxy. The laws of gravity say that the stars that are closest to the center of the galaxy — which is also its center of mass — should move faster than those out on the galaxy’s edge.

Yet when astronomers measured stars all across the galaxy, they found that they all orbit the center of the galaxy at about the same speed. This suggests that something outside the galaxy’s disk is tugging at the stars: dark matter.

Calculations show that a vast "halo" of dark matter surrounds the Milky Way. The halo may be 10 times as massive as the bright disk, so it exerts a strong gravitational pull.

The same effect is seen in many other galaxies. And clusters of galaxies show exactly the same thing — their gravity is far stronger than the combined pull of all their visible stars and gas clouds.

Scientists shed light on mystery of dark matter HeritageDaily


Are dark matter and dark energy related? No one knows. The leading theory says that dark matter consists of a type of subatomic particle that has not yet been detected, although upcoming experiments with the world’s most powerful particle accelerator may reveal its presence. Dark energy may have its own particle, although there is little evidence of one.

Instead, dark matter and dark energy appear to be competing forces in our universe. The only things they seem to have in common is that both were forged in the Big Bang, and both remain mysterious.











































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Source: hetdex

Tuesday, July 19, 2016

LARGEST MAP EVER MADE WILL UNLOCK THE HISTORY OF THE UNIVERSE 1.2 MILLION GALAXIES






















Updated 02/05/2020

"This is one slice through the map of the large-scale structure of the Universe from the Sloan Digital Sky Survey and its Baryon Oscillation Spectroscopic Survey. Each dot in this picture indicates the position of a galaxy 6 billion years into the past. The image covers about 1/20th of the sky, a slice of the Universe 6 billion light-years wide, 4.5 billion light-years high, and 500 million light-years thick. Color indicates distance from Earth, ranging from yellow on the near side of the slice to purple on the far side.


Map of the observable universe. (Pablo Carlos Budassi/Wikimedia/CC BY 4.0)



Galaxies are highly clustered, revealing superclusters and voids whose presence is seeded in the first fraction of a second after the Big Bang. This image contains 48,741 galaxies, about 3% of the full survey dataset. Grey patches are small regions without survey data."

What you're looking at is a slice of the entire universe, a web of galaxies billions of light years away. You're also looking into the past, since the further into the distance you look, the longer it took that light to reach your eyes. It all seems a lot smaller until you realize that each of those dots is hundreds of thousands of light years across.

A collaboration of hundreds of scientists released the "largest-ever, three-dimensional map of distant galaxies" with over 1.2 million spots as a part of the Baryon Oscillation Spectroscopic Survey (BOSS) program using a telescope in New Mexico, according to a press release from Brookhaven National Lab. The map isn't for wanderers; scientists are trying to understand some of the universe's unexplained properties, like what dark matter and dark energy are. Understanding those things requires a three-dimensional map bigger and looking further out than any map scientists have made prior.



"The problem was, if you take data on the brightest galaxies in the sky, they happen to be nearby galaxies," BOSS' principal investigator David Schlegel from Lawrence Berkeley National Lab told Popular Science.

"For a cosmologist, that’s just a map of the backyard. I don’t want a map of the backyard. I want a map of the universe."

Up until fifty or so years ago, scientists more or less understood the universe, said Schlegel. But the discovery of dark matter and dark energy showed we don't really understand most of it, since they make up around 95 percent of the stuff in the universe. Yeah, we don't understand 95 percent of the stuff in the universe.

That's not to say we can't measure or detect dark matter and dark energy, though. If you look at the map, you'll see a web of galaxies and places where dots clump. Dark matter still feels gravity's pull, so galaxies align themselves along the webs and clumps of dark matter. We can detect dark energy too. When we look into space, really distant things we'd expect to look white actually look red; they've been redshifted. That's because their light rays have stretched out, because the space itself the light travels through expands, like a stretched-out tattoo on someone who's gaining a lot of weight.

By measuring really far away things, we found out that the universe wasn't just expanding, but the rate it expanded was actually speeding up. That discovery won a team of scientists the 2011 Nobel Prize in Physics.


"I don’t want a map of the backyard. I want a map of the universe."



Map of large universe (Hélène Courtois, Daniel Pomarède, R. Brent Tully, Yehuda Hoffman, and Denis Courtois) smithsonianmag






In one theory of the universe, there's a single number called the "cosmological constant" that says dark energy is a uniform thing permeating the universe and making it expand. Some physicists were hoping that a larger map would show the cosmological constant's value changing in different places, rather than just being a single number everywhere, but the single number stuck throughout the swath of the universe covered by BOSS' results. Schlegel thought theoretical physicists might be a little pigeonholed by the results, since they can do more with varying numbers than a single constant.

Mark Wise, theoretical physicist at California Institute of Technology, hadn't reviewed the BOSS results yet but agreed with Schlegel. "It would be more exciting if it was something else," he told Popular Science.


Map of Universe


The BOSS experiment is about more than just dark energy, though, pointed out Anže Slosar, Brookhaven National Lab and BOSS cosmologist who leads his "futile existence as a scientist and a bureaucrat" (much as a cosmologist would), according to his website. The experiment will also help pinpoint the mass of the neutrino particle. Soon, other experiments like the larger Dark Energy Spectroscopic Instrument (DESI) on a telescope at Kitt Peak in Arizona will pick up where the BOSS experiment leaves off. But Slosar was most excited about how intertwined our physical experiences on Earth are with the rest of the universe.

"The fact that it’s the same fundamental laws that guide GPS satellites all the way down to one second after the big bang is pretty mindblowing," he said.

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Monday, June 20, 2016

NASA's K2 Finds Newborn Exoplanet Around Young Star.



When a planet such as K2-33b passes in front of its host star, it blocks some of the star's light. Observing this periodic dimming, called a transit, from continual monitoring of a star's brightness, allows astronomers to detect planets outside our solar system with a high degree of certainty. This Neptune-sized planet orbits a star that is between 5 and 10 million years old. In addition to the planet, the star hosts a disk of planetary debris, seen as a bright ring encircling the star.
K2-33b, shown in this illustration, is one of the youngest exoplanets detected to date
K2-33b, shown in this illustration, is one of the youngest exoplanets detected to date. It makes a complete orbit around its star in about five days.
Credits: NASA/JPL-Caltech
This image shows the K2-33 system, and its planet K2-33b, compared to our own solar system
This image shows the K2-33 system, and its planet K2-33b, compared to our own solar system. The planet has a five-day orbit, whereas Mercury orbits our sun in 88 days. The planet is also nearly 10 times closer to its star than Mercury is to the sun.
Credits: NASA/JPL-Caltech

Astronomers have discovered the youngest fully formed exoplanet ever detected. The discovery was made using NASA's Kepler Space Telescope and its extended K2 mission, as well as the W. M. Keck Observatory on Mauna Kea, Hawaii. Exoplanets are planets that orbit stars beyond our sun.

The newfound planet, K2-33b, is a bit larger than Neptune and whips tightly around its star every five days. It is only 5 to 10 million years old, making it one of a very few newborn planets found to date.
"Our Earth is roughly 4.5 billion years old," said Trevor David of Caltech in Pasadena, lead author of a new study published online June 20, 2016, in the journal Nature. "By comparison, the planet K2-33b is very young. You might think of it as an infant." David is a graduate student working with astronomer Lynne Hillenbrand, also of Caltech.
Planet formation is a complex and tumultuous process that remains shrouded in mystery. Astronomers have discovered and confirmed roughly 3,000 exoplanets so far; however, nearly all of them are hosted by middle-aged stars, with ages of a billion years or more. For astronomers, attempting to understand the life cycles of planetary systems using existing examples is like trying to learn how people grow from babies to children to teenagers, by only studying adults.
"The newborn planet will help us better understand how planets form, which is important for understanding the processes that led to the formation of Earth," said co-author Erik Petigura of Caltech.

The first signals of the planet's existence were measured by K2. The telescope's camera detected a periodic dimming of the light emitted by the planet's host star, a sign that an orbiting planet could be regularly passing in front of the star and blocking the light. Data from the Keck Observatory validated that the dimming was indeed caused by a planet, and also helped confirm its youthful age.


Infrared measurements from NASA's Spitzer Space Telescope showed that the system's star is surrounded by a thin disk of planetary debris, indicating that its planet-formation phase is wrapping up. Planets form out of thick disks of gas and dust, called protoplanetary disks, that surround young stars.

"Initially, this material may obscure any forming planets, but after a few million years, the dust starts to dissipate," said co-author Anne Marie Cody, a NASA Postdoctoral Program fellow at NASA's Ames Research Center in California's Silicon Valley. "It is during this time window that we can begin to detect the signatures of youthful planets with K2." 

A surprising feature in the discovery of K2-33b is how close the newborn planet lies to its star. The planet is nearly 10 times closer to its star than Mercury is to our sun, making it hot. While numerous older exoplanets have been found orbiting very tightly to their stars, astronomers have long struggled to understand how more massive planets like this one wind up in such small orbits. Some theories propose that it takes hundreds of millions of years to bring a planet from a more distant orbit into a close one -- and therefore cannot explain K2-33b, which is quite a bit younger.

The science team says there are two main theories that may explain how K2-33b wound up so close to its star. It could have migrated there in a process called disk migration that takes hundreds of thousands of years. Or, the planet could have formed "in situ" -- right where it is. The discovery of K2-33b therefore gives theorists a new data point to ponder.

"After the first discoveries of massive exoplanets on close orbits about 20 years ago, it was immediately suggested that they could absolutely not have formed there, but in the past several years, some momentum has grown for in situ formation theories, so the idea is not as wild as it once seemed," said David.

"The question we are answering is: Did those planets take a long time to get into those hot orbits, or could they have been there from a very early stage? We are saying, at least in this one case, that they can indeed be there at a very early stage," he said.

Ames manages the Kepler and K2 missions for NASA's Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder.


Source : NASA