the galaxy and the universe · · 2018-03-31the galaxy and the universe 7 articles ... 306 words...

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The Galaxy and the Universe7 Articles

Check articles you have read:

How Did the Universe Begin?138 words

The Milky Way Galaxy306 words

The Big Bang89 words

In Pictures: Beyond Planet Earth1387 words

In Pictures: Journey to the Stars1524 words

One-On-One With the Sun1652 words

Meet the Ologist: Neil deGrasse Tyson2070 words

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How Did the Universe Begin?T his text is pro vided co urtesy o f OLo g y, the American Museum o f Natural Histo ry’s website fo r kids.

In the 1920s in California, astronomer Edwin Hubble observed distant galaxies using an extremely

powerful telescope. He made two mind-boggling discoveries.

First, Hubble figured out that the Milky Way isn’t the only galaxy. He realized that faint, cloud-like

objects in the night sky are actually other galaxies far, far away. The Milky Way is just one of billions

of galaxies.

Second, Hubble discovered that the galaxies are constantly moving away from each other. In other

words, the universe is expanding. The biggest thing that we know about is getting bigger all the

time.

A few years later, Belgian astronomer Georges Lemaître used Hubble‘s amazing discoveries to

suggest an answer to a big astronomy question: “How did the universe begin? ”

Illustrations courtesy of AmandaDuffy

This breakthrough idea later became known as…

Illustrations courtesy of Amanda Duffy

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of 31 © 2018 ReadWorks®, Inc. All rights reserved.© 2015 American Museum of Natural History. All rights reserved. Used by Permission

Photo Credit: NASA

Milky Way as seen from Earth

Photo Credit: NASA/JPL

Milky Way as seen from below

Photo Credit: NASA/JPL

Milky Way as seen from the side

The Milky Way GalaxyT his text is pro vided co urtesy o f OLo g y, the American Museum o f Natural Histo ry’s website fo r kids.

The Milky Way is a huge collection of stars, dust, and gas. It’s called a

spiral galaxy because if you could view it from the top, it would look like a

spinning pinwheel. The Sun is located on one of the spiral arms, about

25,000 light-years away from the center of the galaxy. Even if you could

travel at the speed of light (186,000 miles per second), it would take you

about 25,000 years to reach the middle of the Milky Way.

The Milky Way gets its name from a Greek

myth about the goddess Hera who sprayed

milk across the sky. In other parts of the world, our galaxy goes by other

names. In China it’s called the “Silver River,” and in the Kalahari Desert

in Southern Africa, it’s called the “Backbone of Night.”

If you could see our galaxy from the side, it would look like a huge, thin

disk with a slight bump in the center. This flat shape is caused by the

galaxy spinning around. Everything in our spinning galaxy would fly off

into space if it weren’t for the force of gravity.

Without a telescope, we can see about 6,000 stars from Earth. That may

seem like a lot of stars, but it’s actually only a small part of the whole. If

you think of the entire galaxy as a giant pizza, all the stars you can see

from Earth fall within about one pepperoni on that pizza. In fact, for

every star you can see, there are more than 20 million you cannot see.

Most of the stars are too faint, too far away, or blocked by clouds of

cosmic dust.

SHOW_AUTO_COPYRIGHT© 2016 American Museum of Natural History. All rights reserved. Used by Permissionamnh The Milky Way Galaxy


The Big BangT his text is pro vided co urtesy o f OLo g y, the American Museum o f Natural Histo ry’s website fo r kids.

1. About 13 billion years ago, the universe began as a tiny, dense fireball that exploded.

2. In the early years, everything was made of gas. This gas, mostly hydrogen and helium,

expanded and cooled.

3. Over billions of years, gravity caused gas and dust to form galaxies, stars, planets, and more.

4. The matter that spread out from the Big Bang developed into everything in the universe—even

YOU!

5. Most astronomers use this theory to explain how the universe began, but what caused this

explosion in the first place is a mystery.

SHOW_AUTO_COPYRIGHT© 2015 American Museum of Natural History. All rights reserved. Used by Permissionamnh The Big Bang


In Pictures: Beyond Planet EarthT his text is pro vided co urtesy o f OLo g y, the American Museum o f Natural Histo ry’s website fo r kids.

What would it be like to travel across the solar system and explore space?

Hi, I'm Mike Shara, an astrophysicist at the American Museum of Natural History.

Let's take a look at some of the places that humans might go someday, and the questions that

scientists are asking.

Courtesy of JPL, California Instituteof Technology and NASA

A solar system is made up of a starand everything that travels around it.Solar means "of the sun." In ourSolar System, the Sun is orbited bythe terrestrial planets Mercury,Venus, Earth, and Mars, the gasplanets Jupiter, Saturn, Uranus,Neptune, and Pluto, and the ring ofcomets known as the Kuiper Belt. Itsouter edge is the spherical cloud ofcomets called the Oort Cloud.

Our closest neighbor is the Moon. Did you know that only 12 people have ever set foot on its near-

black, powdery surface?

No one has been to the Moon since 1972. But today, many scientists want to send people and robots

back there. What do you think it would be like to live and work on the Moon?

SHOW_AUTO_COPYRIGHT© 2016 American Museum of Natural History. All rights reserved. Used by PermissionamnhIn Pictures: Beyond Planet Earth


© NASA

Moon

Image credits: courtesy of USGS;Mordecai-Mark MacLow: AMNH.

Meteorites and asteroids havebombarded the Moon for billions ofyears, leaving deep craters on itssurface. Without the forces ofweather to remove them, the cratersact as a record of all of theseimpacts. Many of its craters andmountains can be seen with thenaked eye! In fact, some peoplethink that these features resemble aman's face. What do you see whenyou look at the Moon?

© NASA

Moon Walk

© John R. Whitesel

Expandable Spacecraft

When and if humans return to the Moon, they might want to set up a base camp. Astronauts could

eat, sleep, bathe, and work in an expandable spacecraft like this one.

The Moon would be a great place to do astronomy. There is no atmosphere to block the view!

Scientists can set up a liquid mirror telescope that could detect light from the earliest days of the

universe.

In Pictures: Beyond Planet Earth


Courtesy of AMNH

On a clear night, Mike Shara seesmore than just the beautiful twinklingof stars when he gazes at the sky.Mike is an astrophysicist and studiesstars' life cycles at the AmericanMuseum of Natural History. He oftenuses the Hubble Space Telescopeand other large telescopes on Earthto make his observations.

Photo Credit: Courtesy of P.Hickson/ University of BritishColumbia; lunar elevator

Most reflecting telescopes use glassmirrors to focus light from farawayobjects, such as stars and galaxies.In a liquid mirror telescope, thismirror is a pool of shiny liquid insteadof glass. Someday scientists hope tobuild a huge liquid mirror telescope atthe Moon's South Pole. Since there'sno atmosphere to blur the view,astronomers can see clearer andfarther away than from Earth.

© AMNH

Lunar Elevator

Image Credits: courtesy of NASA;Rosamond Kinzler: AMNH

The Earth is our home. So far, it’s theonly place that we know of that haslife. Everywhere you look on Earththere is life. This is possible becauseEarth has lots of water. It’s also justthe right distance from the Sun.Some people call Earth the“Goldilocks planet.” It’s not too hot(like Venus), and not too cold (likeMars), it’s just right!

Scientists are also working on an idea of a lunar elevator. Secured to a cable from a space station to

the Moon, it would help transport goods and people between Earth and the Moon.

Orbiting beyond the Moon is an asteroid named Itokawa. This space rock is huge. It's longer than 50

school buses! Itokawa is one of more than 7,000 near-Earth asteroids in our solar system.



© NASA

Mars

Courtesy of JPL/MSSS, and NASA

Mars is often called the "red planet."It's red because its surface iscovered with rusted particles of iron.Like the Earth, Mars has polar icecaps, mountains, craters, plains,canyons, and summer and winterseasons. Scientists think that liquidwater once flowed on the surface ofMars when it was warmer. But todaythere are no signs of life or water onMars' rocky surface.

© JAXA

Itokawa

Can humans visit these space rocks? It's definitely a possibility. Learning more about asteroids

could help scientists learn to deflect ones that get too close to Earth.

© NASA

Asteroid Visit

Next stop: Mars. Today, this red planet is cold and dry. But millions of tons of liquid water once

flowed on its surface. Could life have thrived there? Scientists want to find out.



© NASA

Curiosity

Courtesy of NASA

The National Aeronautics and SpaceAdministration (NASA) runs thespace program, but that's just part ofwhat they do. Thousands ofscientists conduct research in fieldslike aeronautics, space exploration,Earth science, and biology. NASA'sresearch centers around the countryare constantly expanding what weknow about our planet and theUniverse around us.

Image Credit: © NASA

If there’s life on any other planet inour solar system, it’s probably onMars. Scientists have sent orbiters,landers, and rovers to the RedPlanet in search of clues of life. TheCuriosity rover is the latest and mostadvanced step in this quest. Thisone-ton science lab will land on Marsinside Gale Crater, which may be adried up lake. Using scientificinstruments, the car-sized rover willexamine the crater for signs of pastor present life.

NASA is sending the Curiosity rover to Mars. This robot is like a roving science lab. It can pick up

samples and test them onboard. And it can fire a laser at rocks to see what they're made of!

Someday, humans might go to Mars too. The Nautilus-Xspacecraft could carry a crew of nine on a

two-year voyage, which is long enough to reach Mars.

© John R. Whitesel

Nautilus-X exterior and interior

Astronauts would sleep in spinning compartments. As it spins, passengers are pushed against the

outer walls. The artificial gravity would help prevent bone loss and other health problems.



© John R. Whitesel


Jim Paillot

Gravity is the force of attractionbetween all objects in the Universe.Objects with more mass havegreater gravitational pull than objectswith less mass. Gravity keeps Earthand the planets orbiting around theSun instead of floating off into space.What would the Universe be likewithout gravity?

Exercise machines would help astronauts keep their muscles and bones strong. Solid waste from

toilets could be used as compost for plants. The plants in turn would provide food and oxygen.

© John R. Whitesel


Mars' surface is cold and barren. But the ingredients for a warm, wet, fertile environment are all

there. They're just frozen underground. Could we turn Mars into a livable planet? Some scientists

think so!

Image Credit: © Steven Hobbs

Terraforming Mars



© NASA

Jupiter and moons

Courtesy of NASA

It's fitting that the largest planet in oursolar system is named after Jupiter,the supreme king of all Roman gods.Jupiter is so big that 1,300 Earthscould fit inside this planetarymonster. Jupiter and its kingdom of17 moons are often pounded bymeteorites.

© NASA

More than 60 moons orbit Jupiter.One of these moons is Europa. It isespecially intriguing to scientists.Miles below its cracked icy surfacelies a deep saltwater ocean. Futuremissions to Europa will investigatethese oceans for signs of life. If lifeexists, what kinds of organismscould survive in such a cold, darkplace? To answer this question,scientists look to some of the mostextreme environments on Earth.

Transforming Mars into an Earthlike planet would take hundreds or even thousands of years. And it

would be very expensive. But we could learn a lot about how climates and ecosystems work.

© Steven Hobbs

Terraforming Mars

Further out our solar system is the giant planet Jupiter. Did you know that it has at least 50 moons?

One of its moon is the ice-covered Europa.

Scientists think that there may be a deep saltwater ocean beneath Europa's icy surface. On Earth,

life exists wherever there is water. Is the same true on this moon? Future missions may find out!



Image credits: © AMNH/D.Finnin;Mordecai-Mark Mac Low: courtestyof AMNH / D. Finnin.

In college, Mordecai-Mark Mac Lowdecided to take science classes thatlooked like fun. So he choseastrophysics, which uses physics tounder- stand how the universeworks. Today, he's anastrophysicist, studying how stars,planets, and galaxies form. Sincethese process take millions of years,he models them using computersimula- tions. Then he compares themodels to observa-tions of objects atdifferent stages of formation.

Image credits: courtesy of AMNH /D. Finnin.

As a kid growing up in New YorkCity, Rebecca Oppenheimer alwayswanted to study stars and planets.She never dreamed she wouldsomeday discover an entirely newkind of object. In 1995, she observeda small, dim object that was neither aplanet nor a star. It is called a browndwarf. This observation shows usthat there are still things left to bediscovered in the universe. Rebeccaalso studies faraway planets, anddying stars called white dwarfs.

© AMNH

Image credits: © AMNH; Mordecai-Mark Mac Low: courtesty of AMNH /D. Finnin.

A star is a huge glowing ball of hotgas. Deep inside its core, hydrogenatoms smash together, forminghelium and releasing huge amountsof energy that heats the gas. This iscalled nuclear fusion, and it's why astar shines. As the hot gas pushesoutward, it opposes the inward pull of

© AMNH

In Pictures: Journey to the StarsBy American Museum o f Natural Histo ry

T his text is pro vided co urtesy o f OLo g y, the American Museum o f Natural Histo ry’s website fo r kids.

Hi, we're Mordecai-Mark Mac Low and Rebecca Oppenheimer. We are astrophysicists at the

American Museum of Natural History. Did you know that stars are really important to us? In fact,

they make all l ife possible. Let's find out why!

Twinkle, twinkle, little star... On a clear night, we can see thousands of stars with our naked eye.

SHOW_AUTO_COPYRIGHT© 2016 American Museum of Natural History. All rights reserved. Used by PermissionamnhIn Pictures: Journey to the Stars


gravity. This balance of forces iswhat makes a star, a star. It holdsthe star together and keeps it at asteady temperature for most of itslife.

Image credits: The Milky Way inInfrared, courtesy of The COBEProject, DIRBE, and NASA; MikeShara: courtesy of AMNH.

The Milky Way is the galaxy in whichour Solar System lives. There aremore than 200 billion stars in ourspiral galaxy, and our Sun is just oneof them. Even if you traveled at thespeed of light, it would take youabout 100,000 years to get acrossthe Milky Way.

Image credits: The image of theuniverse © American Museum ofNatural History and the NationalCenter for SupercomputingApplications, 1999; Charles Liu:courtesy of AMNH.

You have to be a really big thinker toimagine the size of the Universe. It'sso big that light from the most distantgalaxies takes over 10 billion yearsjust to reach us on Earth! That'stwice as long as Earth's beenaround. Everything we've everobserved in space is part of ourUniverse. We don't know what'sbeyond it or if there are otherUniverses out there.

© AMNH

Image credits: Jim Paillot.

Gravity is the force of attractionbetween all objects in the Universe.Objects with more mass havegreater gravitational pull than objectswith less mass. Gravity keeps Earthand the planets orbiting around theSun instead of floating off into space.

© AMNH

In the Milky Way Galaxy alone, there are hundreds of billions of stars. And there are many more in

the universe. But did you know that a long, long time ago, there were no stars at all?

Over 13 billion years ago, there was only an invisible substance called dark matter, along with

hydrogen and helium gas. Dark matter's gravity gathered this gas to form the first stars.

In Pictures: Journey to the Stars


What would the Universe be likewithout gravity?

Image credits: courtesy of NASA;Rosamond Kinzler: AMNH.

The Earth is our home. So far, it's theonly place that we know of that haslife. Everywhere you look on Earththere is life. This is possible becauseEarth has lots of water. It's also justthe right distance from the Sun.Some people call Earth the"Goldilocks planet." It's not too hot(like Venus), and not too cold (likeMars), it's just right!

Image credits: courtesy of NASA;Neil Tyson: AMNH.

Ninety-three million miles from Earth,a giant ball of hot gas brightens thesky. Nuclear reactions in the Sun'score create energy, which graduallyflows to the Sun's surface. Thisenergy reaches Earth in the form ofsunlight. The Sun's heat and lightwarm Earth's surface, drive weatherand currents, and make life possibleon our planet. We experience theSun's energy every time we feel itswarmth on our skin or see with theaid of sunlight.

© AMNH

But the first stars didn't last long. They were massive. They burned hot, l ived fast, and died young.

They blew up in gigantic explosions called supernovas.

Stars are factories for new elements. As stars live and die, they form almost all of the elements

that we know of, l ike oxygen and carbon.

Image credits: Eric Hamilton.

We see light every day -- whether from light bulbs,flames, flashlights, or the Sun (our most importantsource of light). We see objects because theyreflect, or bounce, light into our eyes. Light is aform of energy called electromagnetic radiation. It'smade of tiny particles called photons that travel instraight lines. In a vacuum, nothing can travelfaster.



© AMNH

© AMNH

Image credits: Eric Hamilton.

Energy is the ability to do work.Scientists define "work" as when aforce moves something. When youlift a brick, you are doing workbecause you are exerting a force to

© AMNH

Earth orbits a star we call the Sun. It is a middle-aged yellow star that is more massive than the

average star.

The Sun is a star that powers our planet. It brightens our days and provides us with heat and other

forms of energy.

© AMNH

The Sun, like all stars, is a huge glowing ball of hot gas. It gives off energy as light that we can see

—sunshine. It also gives off invisible light, such as ultraviolet and radio.



lift the heavy object. Energy comesin many forms, such as heat, sound,light, electric, and chemical. Energyeasily changes from one form toanother.

Image credits: courtesy of AMNH. Image credits: "Observers","Institute", Sven Kohle and Till

At the end of its life, the Sun will become a red giant. It will blow its outer layers out into the

universe, seeding new stars and planets. But don't worry. This won't happen for 5 billion years.

© AMNH

Scientists observe stars using telescopes on Earth and in space. They see stars being born,

maturing, and at the ends of their lives.

© AMNH

This is the Orion Nebula. Huge stellar nurseries like this are found all over the Milky Way and other

spiral galaxies.



Before telescopes were invented,people gazed at the night sky withamazement and dreamed of a closerlook. The invention of the telescopein 1608 gave humans their chance toexplore the vastness of theUniverse. In fact, most of what weknow about the Universe comesfrom studying the sky withtelescopes. Telescopes use lensesand mirrors to gather light andproduce images. Galileo was the firstto use telescopes for astronomy.

Credner.

The Orion constellation is known forhaving some of the brightest stars inthe night sky. On a clear night, try tofind the three stars that form the"belt" of the hunter. Above and belowthe belt you'll see Betelgeuse andRigel. Betelgeuse looks reddish andRigel is blue. The cloudy area justbelow the belt is the Orion Nebula --the closest major star-forming regionto Earth.

Image credits: The SouthernPinwheel Galaxy from VLT, FORSTeam 8.2-meter VLT ESO HubbleDeep Field ,R. Williams and the HDFTeam (STScI) and NASA M31: TheAndromeda Galaxy, © and Courtesyof Jason Ware; Charles Liu:courtesy of AMNH.

A galaxy is a giant, spinning objectmade of gas, dust, and stars heldtogether by gravity. Galaxies comein different shapes and sizes andcan contain billions of stars. Mostoccur in groups that are also heldtogether by gravity. We now knowthat the Universe has billions ofgalaxies, and the Milky Way is onlyone of them.

© AMNH

© AMNH

The Pleiades is an older star cluster than the

one in Orion. Young stars are leaving this

cluster, too.

See those teardrop shapes? They are gas and dust clouds that cradle infant stars. Most stars form in

tightly packed groups called star clusters.



© AMNH

Scientists also observe stars at the ends of

their lives. The remains of one of these stars

formed the Helix Nebula.

© AMNH

All that remains of the star is a very dense

object called a white dwarf. It will take

billions of years to cool and slowly fade

away.

© AMNH

Brown dwarfs are neither stars nor planets.

And they are as numerous as stars! The

discovery of these new objects tells us that

our cosmic family is more diverse than we

imagined.



One-On-One With the SunBy American Museum o f Natural Histo ry


Illustration Credit: Jim Steck

Hey, Stella Stardust here. Welcome to another cosmic conversation. Let’s give a warm welcome to

the Sun!

Image Credit: Courtesy of NASA;Neil Tyson: AMNH

Ninety-three million miles from Earth,a giant ball of hot gas brightens thesky. Nuclear reactions in the Sun'score create energy, which graduallyflows to the Sun's surface. Thisenergy reaches Earth in the form ofsunlight. The Sun's heat and lightwarm Earth's surface, drive weatherand currents, and make life possibleon our planet. We experience theSun's energy every time we feel itswarmth on our skin or see with theaid of sunlight.

STELLA: You know, everyone here on Earth loves your work. If it weren’t for you, we wouldn’t be

here.

SUN: Thanks, Stella. I’ve been cranking out energy for billions of years—and not one day off.

STELLA: Impressive. Your agent told me that you’re the biggest star in the universe. Is that true?

SHOW_AUTO_COPYRIGHT© 2016 American Museum of Natural History. All rights reserved. Used by PermissionamnhOne-On-One With the Sun


SUN: Actually, no. My agent tends to exaggerate. I’m just a medium-sized star. To my fans on Earth,

I look much bigger than the other stars in the sky. That’s because I’m much closer to you than the

other stars. I’m 93 million miles away from you. The bigger stars are millions of times farther away

from your planet.

Image credits: The image of theuniverse © American Museum ofNatural History and the NationalCenter for SupercomputingApplications, 1999; Charles Liu:courtesy of AMNH.

You have to be a really big thinker toimagine the size of the Universe. It'sso big that light from the most distantgalaxies takes over 10 billion yearsjust to reach us on Earth! That'stwice as long as Earth's beenaround. Everything we've everobserved in space is part of ourUniverse. We don't know what'sbeyond it or if there are otherUniverses out there.

STELLA: I can’t believe it. You, the Sun, are just an average, ordinary, run-of-the-mill star!

SUN: Hey, take it easy. I may be an average star, but I’m still a LOT bigger than your puny planet.

Guess how many Earth-sized planets could fit inside me?

STELLA: I don’t know. Maybe ten?

SUN: Not even close! More than a million! I'm big and I've got lots of mass. That's why I've got a lot

of gravity. You guys don’t call this the Solar system for nothing. "Solar" means "sun." This is my

show. All the planets, comets, and asteroids orbit around ME.

Image Credits: Jim Paillot

One-On-One With the Sun


Image Credits: Jim Paillot

Gravity is the force of attractionbetween all objects in the Universe.Objects with more mass havegreater gravitational pull than objectswith less mass. Gravity keeps Earthand the planets orbiting around theSun instead of floating off into space.What would the Universe be likewithout gravity?

STELLA: I know you star types tend to be touchy about age, but how old are you?

SUN: Well, I began shining about 4.6 billion years ago. It was so long ago I don’t remember the

exact day.

STELLA: Was it a Sunday? Just kidding. Actually, I’m curious to know how stars begin. What’s your

story?

SUN: We stars begin as huge spinning clouds of gas and dust. Gravity pulls the gas and dust together

in round clumps, which get hot. At that point, we're called protostars. Eventually we get hot enough

to start fusing hydrogen atoms together, which releases energy. Then we really shine. Stars are

born in batches, which are like star nurseries. Then, over millions of years, these stars drift apart

and spread out around the galaxy.

Image credits: courtesy of JPL,California Institute of Technology andNASA; Frank Summers: AMNH.

If you ever go to Mercury, bring yoursunscreen because it is the planetclosest to the Sun. You'll also need apair of thermal underwear becauseat night Mercury cools down fast.Temperatures can drop to as low as-292 degrees F! Now that's cold! Youwill also need a pair of hiking bootsso you can travel and climb in andout of the craters that coverMercury's scarred landscape.

Image credits: courtesy of NASA;Mordecai-Mark MacLow: AMNH.

Venus and Earth are sometimescalled sister planets because of theirsimilar size, but don't let thiscomparison fool you! Venus, thesecond planet from the Sun, has athick and heavy atmosphere thattraps the Sun's heat to producesizzling temperatures. This planetarygreenhouse has been visited by overtwenty spacecrafts. Each missionreturned with important data aboutthis mysterious planet.

Image credits: courtesy of NASA;Rosamond Kinzler: AMNH.

The Earth is our home. So far, it's theonly place that we know of that haslife. Everywhere you look on Earththere is life. This is possible becauseEarth has lots of water. It's also justthe right distance from the Sun.Some people call Earth the"Goldilocks planet." It's not too hot(like Venus), and not too cold (likeMars), it's just right!

STELLA: Let’s turn to a delicate subject. How do stars die?

SUN: After stars like me shine for billions of years, we eventually run out of fuel. When that



happens, we swell up as much as 100 times bigger and are called red giants. Astronomers predict

that I’ll eventually become a red giant. At that time, my heat will vaporize the inner planets -

Mercury, Venus, and Earth

STELLA: That sounds really scary.

SUN: Don’t worry. That won’t happen for about 5 billion years! After I become a red giant, I’ll lose

my outer gas layers and reveal my inner core, known as a white dwarf. When I’m a white dwarf, I’ll

be only as big as Earth, but still very hot, and very dense. Finally, I’ll cool down and disappear from

view.

STELLA: I hear that some stars die differently. What’s a supernova?

SUN: When a star more massive than I gets old and runs out of nuclear fuel, it blows up in a great

flash of light called a

Image credits: In the Heart of theCrab, courtesy of William P. Blair(JHU) et al. Hubble Heritage Team(STScI/AURA), and NASA.

About 1,000 years ago, a massivestar exploded at the end of its lifecycle. What remains is the CrabNebula, a glowing cloud of gas anddust. At the center of the CrabNebula is a pulsar, the small,spinning core of the massive deadstar. The pulsar emits all kinds oflight, making the Crab Nebula easyto detect with a telescope.

supernova. This explosion splatters the star’s guts in all directions.




STELLA: I’d like to show the people at home a picture of a

star that exploded as a supernova. Its remains are called the Crab Nebula.

SUN: What a mess that star made. Want to know something amazing? Humans saw this star explode

in the year 1054. But the explosion actually happened about 6,000 years before that.

STELLA: Huh?

SUN: I’ll explain. Stars give off light, right? Light travels incredibly fast - at a speed of 186,000

miles per second. Light can travel from Earth to the Moon in about one second. My sunlight reaches

you Earthlings in about eight minutes. Most stars are much farther away. That’s why astronomers

don’t use miles when they talk about the distances between stars. That’s like describing the

distance between New York and Los Angeles in inches! Astronomers talk about light-years. A

light-year is the distance light travels in one year. Since the star in that picture was about 6,000

light-years away from Earth when it exploded, it took about 6,000 years for us to get the

“newsflash.”

STELLA: In Hollywood, I meet a lot of people filled with hot air. What gases are inside you?

SUN: Ah, you want to know what gives me that special glow! Well, l ike most other stars, I’m made up

of mostly two gases, hydrogen and helium. These light gases stay close to me because of my

massive gravity. Inside, I’m so hot that I use a fancy process called thermonuclear fusion. By

turning hydrogen into helium, I create lots of energy. It makes me shine.



Image credits: Eric Hamilton; Mordecai-Mark MacLow: AMNH.

Would you measure the distance between New York and New Delhi in inches? For thesame reason, astronomers don't use miles to measure vast distances in space.Instead, they use light-years: the distance that light travels in a year. That makesProxima Centauri, the closest known star to the Sun, 4.28 light-years away; that's a loteasier than saying 24,000,000,000,000,000 miles.

STELLA: This may be a little rude, but what are those dark splotches on you? Are those, like, star

“zits”?

SUN: (sigh) No, those dark splotches are called sunspots. All normal stars have them. They look

dark because they’re cooler than the gases around them. By the way, when I say “cooler,” keep in

mind that my outside is about 10,000o F. That’s many times hotter than the hottest kitchen oven. My

inner core is even hotter, something like 30,000,000o F.

STELLA: Is there anything else you’d like to say?


SUN: You think your sunglasses are “star-shaped,” right?

STELLA: Sure.



SUN: Well, if they were really “star-shaped,” they’d be round. You Earthlings have the strange idea

that stars have points. We don’t. Gravity keeps us shaped like spheres.

STELLA: Thanks to the Sun for a great interview. Good night.

Image credits: courtesy of AURA/NOAO/NSF; Mordecai-Mark MacLow: AMNH.

The Sun is speckled with markings called sunspots thatlook darker than the rest of its surface. These spots showup where strong magnetic fields inside the Sun keepcurrents of hot gas from reaching the surface. Sunspotsfollow an 11-year cycle. The first spots appear near thepoles; as years pass, more spots develop and movetowards the equator.



Courtesy of Jayanne English (STScl)et. Al., CGPS, PAL/U. Calgary,APOD

Milky way as seen from Earth.

Image courtesy of AMNHDepartment of Library Services

The Museum’s first HaydenPlanetarium

Image Courtesy of John W. Young,Apollo 16 Crew and NASA

Astronaut on the Moon

Meet the Ologist: Neil deGrasse TysonBy American Museum o f Natural Histo ry


Does it bug you that you can't get closer to the things you study?

Neil Said: No, It’s the very nature of the subject. I mean, if you were

frustrated by the distance, you wouldn’t be studying astrophysics, you’d

be studying some tabletop science. Part of the fascination is that you

can’t touch it. It’s quite humbling. You can’t interfere with it, you can’t

pollute it, you can’t change it. It’s like fishing – you’re just sitting there,

hoping the fish will bite your bait.

As a kid, what did you do when you wanted to

learn more about space?

Neil Said: When I was eleven, I took my first course at the Hayden

Planetarium on astronomy and astrophysics. Most of the material was

over my head, but that didn't matter. What I did learn was that the science

I was interested in requires real math, real physics. So at eleven I began

to shape my life so that I could get that math and physics background. It

changed my study of the universe from an exercise in simply looking up

to an exercise in learning about the forces and laws of nature.

Did you ever go to space camp?

Neil Said: No, I went to astronomy camp in Arizona, when I was fourteen

- my first real trip away from New York City's light and air pollution.

That's where I noticed that in fact the real sky was a pretty good

approximation of the one I saw in the Hayden Planetarium. Space camp

today is actually for training to be an astronaut. I never wanted to be an

astronaut.

What's the difference between an astrophysicist and an astronomer?

SHOW_AUTO_COPYRIGHT© 2016 American Museum of Natural History. All rights reserved. Used by PermissionamnhMeet the Ologist: Neil deGrasse Tyson


Image Courtesy of Concept Images,1998 Noriko all rights reserved

Light divided by a prism

Images Courtesy ofAURA/NOAO/NSF “CopyrightAssociation of Universities forResearch in Astronomy Inc. (AURA);all rights reserved.”

Spectra of light

Image Courtesy of NASA

City in infrared

Neil Said: In fact there's no difference. It's just that astrophysics reasserts the role of physics in

understanding how the universe works. In the late 1800s we learned that

light from the universe could be analyzed with a prism, which allowed us

to figure out all sorts of things about planets, stars, and galaxies,

especially their chemical composition and whether they are in motion

through space. From then on, scientists began to think about the

universe as it related to the laws of physics.

What's the hardest thing to explain about the

universe?

Neil Said: The hardest thing, I think by far, is how we analyze spectra -

light broken up into its component colors. It's so abstract, so removed

from the actual object we're studying. See, chemists can study actual

chemicals in the lab. Biologists can study actual plants. But

astrophysicists can't go out there and grab a piece of a galaxy and put it

in a laboratory. We have to study a picture of the thing, and then analyze

the light that comes from it. Ninety-nine percent of everything we know

about the machinery of our universe comes to us through the analysis of

light.

What would the world look like if we could see invisible light such as radio

waves?

Neil Said: Completely different. If you could tune your eyeballs to see

radio waves, the antennas on top of tall buildings would be aglow from

TV and radio broadcasts. If you could tune your eyes to microwaves, then

the police officer standing on the edge of the highway with a radar gun

would be the brightest thing on the horizon. If you had infrared eyes

you'd see people glowing from their body temperature. Visible light is

such a tiny slice of the whole spectrum that we are essentially blind. New telescopes can see these

other kinds of light and tell us amazing things about the universe.

If you could send a spacecraft somewhere, where would you send it?

Meet the Ologist: Neil deGrasse Tyson


Image Courtesy of R. Williams andthe HDF Team (STScl) and NASA,Hubble Deep Field

Surface of Europa

Courtesy of NASA

Hubble Space Telescope view ofdeep space

Courtesy of AMNH Department ofLibrary Services

Projector from the Museum's oldHayden Planetarium

Image courtesy of AMNH

Neil Said: Jupiter's moon, Europa. It's got a kilometer of ice on its surface, nothing unusual, but what

is unusual is that that ice appears to be floating on an ocean of liquid

water. It looks a lot like what we see in the Arctic Ocean. And the oceans

are where life began on Earth. Perhaps a form of life developed in the

oceans of Europa. I want to cut a hole and go ice fishing and see what's

down there. It'll happen in the next twenty or thirty years.

How come you never wanted to be an

astronaut?

Neil Said: Because astronauts just went into orbit 200 miles above Earth's

surface, no farther than Boston is from New York City. At best they went

to the Moon. I was fascinated by the space program and I still am. But my

scope, my sense of what I wanted to do in life, extended to the outer

reaches of the universe.

What do you remember about your first visit

to the Hayden Planetarium?

Neil Said: I was nine years old when I first visited the Hayden Planetarium

and I felt as though I could see forever. In the Planetarium's starry dome

I saw thousands of stars, essentially an uncountable number. And I was

pretty convinced that it was a hoax - that it couldn't be the case! I know

how many stars there were, because I'd seen them from the Bronx, New

York, where I'd grown up. Which was the real sky, the thousand-star-

studded sky of the dome, or the sky I recognized? That conflict got me

started.

How did your stargazing career begin?

Neil Said: I was about eleven when a friend of mine lent me a pair of

binoculars. I'd used them at sporting events, but my friend encouraged

me to look up. That's when I saw the Moon for the first time. It wasn't just

bigger, it was better. It was a world unto itself. This object that floats

above us, that we all take for granted, became a place that I could



Department of Library Services

The moon

Photo Courtesy of Neil deGrasseTyson

Neil with his first telescope

Image Courtesy of JPL, CaliforniaInstitute of Technology and NASA

Saturn

Photo Courtesy of Neil deGrasseTyson

Neil as a young astronomer

imagine being, because I saw the mountains and valleys and craters. I

thought to myself, if binoculars could do this what could mountaintop

telescopes do? And you know, 15 years later I was using mountaintop

telescopes, which was an immeasurably bigger and better experience.

When did you get your first telescope?

Neil Said: I was in seventh grade. It was a birthday gift from my parents. It

wasn't one of these wishful gifts that parents buy after thinking, "Oh

wouldn't it be great if Junior gets a chemistry set to get him interested in

chemistry." No, I'd already demonstrated a strong interest in the

universe. It was a simple telescope, I think it cost $50, but that's all you

need to show real details on the Moon's surface or the rings of Saturn.

Why is Saturn your favorite planet?

Neil Said: Oh, it's the most beautiful thing out there. No matter who you

are, no matter your state of mind, if you look at Saturn your mouth drops

open. If l ife ever gets you low, just pull out a telescope and look at

Saturn. You say, "My gosh there's a world out there, with a ring around it

- how cool can you get!"

How did you meet other amateur

astronomers?

Neil Said: Through the Amateur Astronomers Association of New York.

Anyone can join, at any age, as long as you're interested in the universe.

A telescope can come later. I happened to join when I was thirteen and

attended all their observing sessions, which are called "star parties."

The dues at the time included a subscription to Sky & Telescope

magazine, which is a hobbyist's dream. There, in this magazine,

appeared article after article about my favorite subject. Most cities in the country have

organizations of amateur astronomers. To be an amateur astronomer is actually a badge of pride.

How are new technologies changing what we know about the universe?



Image courtesy of Dave Finley, AUI,NRAO, NSF

radio telescopes

courtesy of STScI, The HubbleHeritage Team and NASA

faraway stars

Courtesy of NASA

The Planets

Courtesy of NASA

Hubble Space Telescope view ofdeep space

Neil Said: Advances in our knowledge of the universe have always

marched in step with advances in technology. For example, fifty years

ago, there was only one view of the universe, and it was through the

visible part of the spectrum of light. But now, every window of light in the

universe is now open to us. We now have telescopes on Earth and in orbit

that are sensitive to gamma rays, X-rays, ultraviolet, infrared,

microwaves, and to radio waves. It's all just light - it just happens to be

invisible to the naked eye.

What does light tell us about the universe?

Neil Said: Different objects and phenomena in space give off different

kinds of light. And that light tells us all kinds of things: what an object is

made of, how old it is, whether it's moving towards or away from us,

whether it's spinning. Studying the light from these distant objects is the

most fundamental way we know anything about the universe.

How has the space program changed

astrophysics?

Neil Said: The space program enabled us to visit the solar system as

though it were our backyard. It transformed the solar system into a

laboratory, mainly because now we can make little robots that get up

there faster and easier and don't have to be brought back. But that's just

nearby.

What question do you get asked most often?

Neil Said: The number one question is, "Is there life elsewhere in the

universe? " Given the sheer scale of the universe, and given how quickly

life formed on Earth, and given that life is made out of the most common

ingredients in the universe, there's no question that life exists

elsewhere. It took only 200 million years - just 4% of Earth's total

history - to jumpstart life. History has shown us that the more we think

we're special, the more we find out we're not. So get used to it!



Courtesy of Jayanne English(STScI) et. Al., CGPS, RAL/U.Calgary, APOD

Milky Way seen from the side

Courtesy of University of Arizona,JPL/SSI and NASA, Galileo

Surface of asteroid Eros

You study the structure of our galaxy, the Milky Way. What makes this hard to do?

Neil Said: The Milky Way is our home, and it's very difficult to know the

structure of something if you're embedded within it. It's as difficult as an

unborn child trying to figure out what its mother looks like. Imagine one

of the blueberries in a blueberry pancake. If the pancake is our entire

Milky Way Galaxy and the Sun was in the center of the blueberry, the

farthest we can see is the edge of the berry. So we use radio waves and

other techniques that can penetrate through the pancake (through the

galaxy) to try to see what's out there.

What are some tricky questions astrophysicists wrestle with?

Neil Said: Oh, big, grand questions like, will we expand forever, what's

the shape of the universe? That sort of thing. But there are some

questions that hit home. For example, when is the next asteroid going to

hit Earth? But people shouldn't worry about the next collision, 'cause

when it happens you'll be dead. If it doesn't happen, you'll be fine. I'm

not worried, it's just part of the cycle of life. An asteroid took out the

dinosaurs 65 million years ago and enabled the mammals of the day to

rise up from the underbrush and lead to species that today include humans. We're here because of

an asteroid.



the galaxy and the universe · · 2018-03-31the galaxy and the universe 7 articles ... 306 words...

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