vania-janet/multiturn-rag-retrieval-data huggingface dataset:
Galaxies - NASA Science
Most large galaxies have supermassive black holes at their centers, some with billions of times the Sun’s mass.Galaxies come in a variety of shapes, mostly spirals and ellipticals, as well as those with less orderly appearances, usually dubbed irregular.Most galaxies are between 10 billion and 13.6 billion years old. Some are almost as old as the universe itself, which formed around 13.8 billion years ago. Astronomers think the youngest known galaxy formed approximately 500 million years ago.Galaxies can organize into groups of about 100 or fewer members held together by their mutual gravity. Larger structures, called clusters, may contain thousands of galaxies. Groups and clusters can be arranged in superclusters, which are not gravitationally bound. Superclusters, empty voids, “walls” of galaxies, and other large-scale structures make up the cosmic web of matter in the universe.Our Milky WayOur home galaxy is called the Milky Way. It’s a spiral galaxy with a disk of stars spanning more than 100,000 light-years. Earth is located along one of the galaxy’s spiral arms, about halfway from the center. Our solar system takes about 240 million years to orbit the Milky Way just once.This illustration shows the Milky Way, our home galaxy.NASA/JPL-CaltechFrom our perspective on Earth, the Milky Way looks like a faint, milky band of light arcing across the entire sky, which is how it got its name. This feature marks the central disk of our home galaxy seen edge on.The Milky Way sits in a neighborhood with over 50 other galaxies called the Local Group.
What is the Universe? - NASA Science
Or collect 333,000 Earth masses of hydrogen and helium together, and you have a Sun-like star.For the sake of practicality, humans categorize clumps of matter based on their attributes. Galaxies, star clusters, planets, dwarf planets, rogue planets, moons, rings, ringlets, comets, meteorites, raccoons — they’re all collections of matter exhibiting characteristics different from one another but obeying the same natural laws.Scientists have begun tallying those clumps of matter and the resulting numbers are pretty wild. Our home galaxy, the Milky Way, contains at least 100 billion stars, and the observable universe contains at least 100 billion galaxies. If galaxies were all the same size, that would give us 10 thousand billion billion (or 10 sextillion) stars in the observable universe.But the universe also seems to contain a bunch of matter and energy that we can’t see or directly observe. All the stars, planets, comets, sea otters, black holes and dung beetles together represent less than 5 percent of the stuff in the universe. About 27 percent of the remainder is dark matter, and 68 percent is dark energy, neither of which are even remotely understood. The universe as we understand it wouldn’t work if dark matter and dark energy didn’t exist, and they’re labeled “dark” because scientists can’t seem to directly observe them. At least not yet.Two views from Hubble of the massive galaxy cluster Cl 0024+17 (ZwCl 0024+1652) are shown. To the left is the view in visible-light with odd-looking blue arcs appearing among the yellowish galaxies. These are the magnified and distorted images of galaxies located far behind the cluster. Their light is bent and amplified by the immense gravity of the cluster in a process called gravitational lensing. To the right, a blue shading has been added to indicate the location of invisible material called dark matter that is mathematically required to account for the nature and placement of the gravitationally lensed galaxies that are seen. NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University)How has our view of the universe changed over time?Human understanding of what the universe is, how it works and how vast it is has changed over the ages.
How Old Are Galaxies? | NASA Space Place – NASA Science for Kids
How Old Are Galaxies? | NASA Space Place – NASA Science for Kids

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How Old Are Galaxies?

This is an illustration of our galaxy, the Milky Way. The Milky Way is an ancient galaxy that was born only a few hundred million years after the Big Bang. Credit: NASA/JPL

Most galaxies are between 10 billion and 13.6 billion years old. Our universe is about 13.8 billion years old, so most galaxies formed when the universe was quite young!
Astronomers believe that our own Milky Way galaxy is approximately 13.6 billion years old. The newest galaxy we know of formed only about 500 million years ago.

Credit: NASA/JPL-Caltech

How can astronomers study things that are so far away?
Astronomers use light to study things that are far away. In fact, light even gives us a way to look back in time!
Light always travels at a certain speed: nearly 186,000 miles (300,000 kilometers) per second. That means that light can travel about 6 trillion miles (about 10 trillion kilometers) in one Earth year. We call this distance a light-year.
This means that the farther away something is, the longer it takes for light from that object to reach us.
What is the most distant galaxy we know of?
In 2016, astronomers used NASA's Hubble Space Telescope to measure a galaxy called GN-z11 that is 13.4 billion light-years away. Because it is that far away, Hubble sees the light from the young galaxy as it was when the Universe was just 400 million years old.

This animation shows the location of the farthest galaxy ever seen, called GN-z11. Credit: NASA, ESA, and P. Oesch (Yale University), G. Brammer (STScI), P.van Dokkum (Yale University) and G. Illingworth (University of California, Santa Cruz)

What can we learn by studying distant galaxies?
Astronomers have observed lots of galaxies at different distances.
Galaxies - NASA Science
Our solar system takes about 240 million years to orbit the Milky Way just once.This illustration shows the Milky Way, our home galaxy.NASA/JPL-CaltechFrom our perspective on Earth, the Milky Way looks like a faint, milky band of light arcing across the entire sky, which is how it got its name. This feature marks the central disk of our home galaxy seen edge on.The Milky Way sits in a neighborhood with over 50 other galaxies called the Local Group. Its members range in size from dwarf galaxies (smaller galaxies with up to a few billion stars) to Andromeda, our nearest large galactic neighbor.The Local Group sits just off the edge of the Virgo cluster and is part of the Laniakea supercluster.Galaxies StoriesExplore All Galaxy StoriesArticle2 min readHubble Captures a Bright Spiral in the Queen’s HairArticle5 min readGalaxies Actively Forming in Early Universe Caught Feeding on Cold Gas6 min readNew Images From Euclid Mission Reveal Wide View of the Dark UniverseArticle2 days ago5 min readSpotted: ‘Death Star’ Black Holes in ActionImage Article2 min readHubble Views Cosmic Dust LanesArticle1 week agoKeep ExploringDiscover More Topics From NASAUniverseBlack HolesStarsExoplanetsReturn to topThe National Aeronautics and Space AdministrationNASA explores the unknown in air and space, innovates for the benefit of humanity, and inspires the world through discovery.About NASA's MissionJoin UsHomeNews & EventsMultimediaNASA+MissionsHumans in SpaceEarth & ClimateThe Solar SystemThe UniverseScienceAeronauticsTechnologyLearning ResourcesAbout NASANASA en EspañolFollow NASAMore NASA Social AccountsNASA NewslettersSitemapFor MediaPrivacy PolicyFOIANo FEAR ActOffice of the IGBudget & Annual ReportsAgency Financial ReportsContact NASAAccessibilityPage Last Updated:2 weeks agoPage Editor:SMD Content EditorsResponsible NASA Official for Science:Dana Bolles
How Old Are Galaxies? | NASA Space Place – NASA Science for Kids
Because it is that far away, Hubble sees the light from the young galaxy as it was when the Universe was just 400 million years old.

This animation shows the location of the farthest galaxy ever seen, called GN-z11. Credit: NASA, ESA, and P. Oesch (Yale University), G. Brammer (STScI), P.van Dokkum (Yale University) and G. Illingworth (University of California, Santa Cruz)

What can we learn by studying distant galaxies?
Astronomers have observed lots of galaxies at different distances. By comparing them, we can begin to understand how galaxies and their stars are born, how they change and how they die over time.

 	article last updated January 24, 2019
 

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What Is a Light-Year? | NASA Space Place – NASA Science for Kids
All of the other stars we can see with our eyes are farther, some even thousands of light-years away.

Stars are found in large groups called galaxies. A galaxy can have millions or billions of stars. The nearest large galaxy to us, Andromeda, is 2.5 million light-years away. So, we see Andromeda as it was 2.5 million years in the past. The universe is filled with billions of galaxies, all farther away than this. Some of these galaxies are much farther away.

An image of the Andromeda galaxy, as seen by NASA's GALEX observatory. Credit: NASA/JPL-Caltech

In 2016, NASA's Hubble Space Telescope looked at the farthest galaxy ever seen, called GN-z11. It is 13.4 billion light-years away, so today we can see it as it was 13.4 billion years ago. That is only 400 million years after the big bang. It is one of the first galaxies ever formed in the universe.
Learning about the very first galaxies that formed after the big bang, like this one, helps us understand what the early universe was like.

This picture shows hundreds of very old and distant galaxies. The oldest one found so far in GN-z11 (shown in the close up image). The image is a bit blurry because this galaxy is so far away. Credit: NASA, ESA, P. Oesch (Yale University), G. Brammer (STScI), P. van Dokkum (Yale University), and G. Illingworth (University of California, Santa Cruz)

 	article last updated August 27, 2020
 

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Galaxies - NASA Science
Galaxies - NASA Science

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Types - NASA Science
Other classifications organize galaxies by the activity in their central regions – powered by a supersized black hole – and the angle at which we view them.Spiral GalaxiesThis stunning view of spiral galaxy M101, also known as the Pinwheel galaxy, was captured by the Hubble Space Telescope.NASA, ESA, K. Kuntz (JHU), F. Bresolin (University of Hawaii), J. Trauger (Jet Propulsion Lab), J. Mould (NOAO), Y.-H. Chu (University of Illinois, Urbana) and STScI; CFHT Image: Canada-France-Hawaii Telescope/J.-C. Cuillandre/Coelum; NOAO Image: G. Jacoby, B. Bohannan, M. Hanna/NOAO/AURA/NSFOur Milky Way is one example of a broad class of galaxies defined by the presence of spiral arms. These galaxies resemble giant rotating pinwheels with a pancake-like disk of stars and a central bulge or tight concentration of stars.The spiral arms can be wound tightly or loosely, and some cannot be seen from Earth because we view the galaxy from the side, edge on.Spiral galaxies are surrounded by halos, mixtures of old stars, star clusters, and dark matter – invisible material that does not emit or reflect light but still has a gravitational pull on other matter. The youngest stars form in gas-rich arms, while older stars can be found throughout the disk and within the bulge and halo.Both the Milky Way and the Andromeda galaxies belong to a subtype known as barred spirals, which make up two-thirds of the group. Barred spirals sport ribbons of stars, gas, and dust that cut across their centers. Scientists think the presence of a bar indicates that a galaxy has reached full maturity.Elliptical GalaxiesNGC 2865, shown here in an image captured by the Hubble Space Telescope, is an elliptical galaxy located 100 million light-years away.ESA/Hubble & NASAElliptical galaxies have shapes that range from completely round to oval. They are less common than spiral galaxies.Unlike spirals, elliptical galaxies usually contain little gas and dust and show very little organization or structure. The stars orbit around the core in random directions and are generally older than those in spiral galaxies since little of the gas needed to form new stars remains.
Types - NASA Science
They range from dwarf irregular galaxies with 100 million times the Sun’s mass to large ones weighing 10 billion solar masses.Astronomers think these galaxies’ odd shapes are sometimes the result of interactions with others. For example, one spiral galaxy passing another with a stronger gravitational pull could lose some of its material, become distorted, and morph into a new shape. Some, like gas-rich dwarf galaxies, may be new, formed by material pulled from such encounters. Or perhaps when galaxies collide, they create a larger, oddly shaped mashup. Some scientists theorize that some large irregular galaxies could represent an intermediate step between spiral and elliptical galaxies.Irregular galaxies born from galaxy interactions or collisions typically host a mix of older and younger stars, depending on the characteristics and composition of the original galaxies. Irregular galaxies may also hold significant amounts of gas and dust – essential ingredients for making new stars.Active GalaxiesAround 10% of known galaxies are active, which means their centers appear more than 100 times brighter than the combined light of their stars. They can be spiral, elliptical, or irregular. The Milky Way is not currently an active galaxy, although it likely experienced a burst of activity in the past few million years.Astronomers think this excess energy comes from areas near the galaxies’ central supermassive black holes, which range from hundreds of thousands to billions of times the mass of our Sun.Gas and dust collect around the black hole to form an accretion disk. The black hole’s gravity compresses and heats the disk, which causes the material to glow across multiple wavelengths, from infrared to X-rays.Infrared observations show that the black hole and its accretion disk are embedded within a clumpy ring of cooler dust, called a torus, that may be a few light-years across. Close to the black hole, a small fraction of the infalling gas can be driven outward, perpendicular to the disk, as jets of particles that move near the speed of light.During the early 20th century, astronomers began classifying active galaxies based on the distinctive characteristics and behaviors they observed. Scientists now think viewing the centers of these galaxies at different angles – for example, seeing directly into the torus versus seeing it from the side – produce many of the signature traits.Active galaxies can also be categorized by their brightness in radio wavelengths.
What is the Universe? - NASA Science
The same can be said about any time in the past — last year, a million years ago, a billion years ago. But the past doesn’t go on forever.By measuring the speed of galaxies and their distances from us, scientists have found that if we could go back far enough, before galaxies formed or stars began fusing hydrogen into helium, things were so close together and hot that atoms couldn’t form and photons had nowhere to go. A bit farther back in time, everything was in the same spot. Or really the entire universe (not just the matter in it) was one spot.Don't spend too much time considering a mission to visit the spot where the universe was born, though, as a person cannot visit the place where the Big Bang happened. It's not that the universe was a dark, empty space and an explosion happened in it from which all matter sprang forth. The universe didn’t exist. Space didn’t exist. Time is part of the universe and so it didn’t exist. Time, too, began with the big bang. Space itself expanded from a single point to the enormous cosmos as the universe expanded over time.What is the universe made of?The universe contains all the energy and matter there is. Much of the observable matter in the universe takes the form of individual atoms of hydrogen, which is the simplest atomic element, made of only a proton and an electron (if the atom also contains a neutron, it is instead called deuterium). Two or more atoms sharing electrons is a molecule. Many trillions of atoms together is a dust particle. Smoosh a few tons of carbon, silica, oxygen, ice, and some metals together, and you have an asteroid. Or collect 333,000 Earth masses of hydrogen and helium together, and you have a Sun-like star.For the sake of practicality, humans categorize clumps of matter based on their attributes. Galaxies, star clusters, planets, dwarf planets, rogue planets, moons, rings, ringlets, comets, meteorites, raccoons — they’re all collections of matter exhibiting characteristics different from one another but obeying the same natural laws.Scientists have begun tallying those clumps of matter and the resulting numbers are pretty wild.
What Is the Big Bang? | NASA Space Place – NASA Science for Kids
What Is the Big Bang? | NASA Space Place – NASA Science for Kids

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What Is the Big Bang?

The Short Answer:

	The big bang is how astronomers explain the way the universe began. It is the idea that the universe began as just a single point, then expanded and stretched to grow as large as it is right now—and it is still stretching!
	

What's This Big Bang All About?
In 1927, an astronomer named Georges Lemaître had a big idea. He said that a very long time ago, the universe started as just a single point. He said the universe stretched and expanded to get as big as it is now, and that it could keep on stretching.

What an Idea!
The universe is a very big place, and it’s been around for a very long time. Thinking about how it all started is hard to imagine.

Some More Information
Just two years later, an astronomer named Edwin Hubble noticed that other galaxies were moving away from us. And that’s not all. The farthest galaxies were moving faster than the ones close to us.

This meant that the universe was still expanding, just like Lemaître thought. If things were moving apart, it meant that long ago, everything had been close together. 

Everything we can see in our universe today—stars, planets, comets, asteroids—they weren't there at the beginning. Where did they come from?

A Tiny, Hot Beginning
When the universe began, it was just hot, tiny particles mixed with light and energy. It was nothing like what we see now. As everything expanded and took up more space, it cooled down.
The tiny particles grouped together. They formed atoms. Then those atoms grouped together. Over lots of time, atoms came together to form stars and galaxies.
The first stars created bigger atoms and groups of atoms. That led to more stars being born. At the same time, galaxies were crashing and grouping together.
What is the Universe? - NASA Science
To the right, a blue shading has been added to indicate the location of invisible material called dark matter that is mathematically required to account for the nature and placement of the gravitationally lensed galaxies that are seen. NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University)How has our view of the universe changed over time?Human understanding of what the universe is, how it works and how vast it is has changed over the ages. For countless lifetimes, humans had little or no means of understanding the universe. Our distant ancestors instead relied upon myth to explain the origins of everything. Because our ancestors themselves invented them, the myths reflect human concerns, hopes, aspirations or fears rather than the nature of reality.Several centuries ago, however, humans began to apply mathematics, writing and new investigative principles to the search for knowledge. Those principles were refined over time, as were scientific tools, eventually revealing hints about the nature of the universe. Only a few hundred years ago, when people began systematically investigating the nature of things, the word “scientist” didn’t even exist (researchers were instead called “natural philosophers” for a time). Since then, our knowledge of the universe has repeatedly leapt forward. It was only about a century ago that astronomers first observed galaxies beyond our own, and only a half-century has passed since humans first began sending spacecraft to other worlds.In the span of a single human lifetime, space probes have voyaged to the outer solar system and sent back the first up-close images of the four giant outermost planets and their countless moons; rovers wheeled along the surface on Mars for the first time; humans constructed a permanently crewed, Earth-orbiting space station; and the first large space telescopes delivered jaw-dropping views of more distant parts of the cosmos than ever before. In the early 21st century alone, astronomers discovered thousands of planets around other stars, detected gravitational waves for the first time and produced the first image of a black hole.Using the Event Horizon Telescope, scientists obtained an image of the black hole at the center of galaxy M87.Event Horizon Telescope collaboration et al.With ever-advancing technology and knowledge, and no shortage of imagination, humans continue to lay bare the secrets of the cosmos. New insights and inspired notions aid in this pursuit, and also spring from it.