Author: jappe

Space.com Editors have selected 12 Great Telescopes in 4 Categories. Are you a traveler? Student of the sky? On a budget? Live in a small home? Do you like digital tech? Or prefer an analog approach?

*Editor’s Note: Start saving on your entire gift list. Get up to 15% cash back and exclusive deals on gadgets, gear, electronics, computers and more through Purch, Space.com’s parent company. And check out our picks for the Best Space Gifts and Best Kids’ Space Gifts and Toys for more ideas.*

A photon leaps off the sun and, about 500 seconds later, bounces off our Earth. Light has been dancing and rebounding from faraway and nearby celestial objects for more than 13 billion years. It’s time you caught some of it for your very own.

That’s what telescopes do; they gather light. But to collect that radiance, you’ll need to pick the telescope that fits your needs and budget. Our editors have selected a few of the best options in five categories. Click on each to read a deep review of the telescopes in these groups: 

Once you’ve picked a great telescope, you might also like to check into what else you might need, using our Astronomy Guide: Tools, Tips and Equipment page.

Now, let’s see which telescopes are the best fit for your needs: 

1. See our Best Telescopes for Kids (Preschool and Up) pages for full reviews by age group 

Toy store telescopes are mostly junk. We’ve selected several better-quality ones, which will be easy to use and fun for all family members. Here are some highlights: 

Editors’ Choice for Viewing

Celestron FirstScope

• Dobsonian / AltAz / Tripod
• Totally intuitive and simple 

Average price: $49.95 + $19.95 Optional Accessory Kit

The Celestron FirstScope is a Space.com top pick for Best Telescopes for Kids.

Credit: Celestron

Remarkably fine optical quality at a very low price makes this surprising telescope a great choice for kids with an interest in the night sky. With patience and a dark location, planets, nebulae and even a few galaxies are in range of this telescope.

The Celestron FirstScope’s tabletop spin-and-tilt design makes the device easy for kids to use. The optical tube is decorated with the names of noteworthy astronomers throughout history, inspiring kids even when it’s sitting on their desk or on a shelf indoors. It comes with two eyepieces (20 millimeters and 4 mm) for wide and close-up views. FirstScope’s 3-inch (76 mm) aperture is small, but its fast focal ratio (3.95) lets kids see objects in the deep sky on dark (moonless) nights. An optional accessory kit adds a finder scope, anti-glare moon filter, two more eyepieces and a DVD-ROM of very useful astronomy software for the PC and Mac.   

Editors’ Choice for Learning

Levenhuk LabZZ MTB3 Combo

• Telescope / Binoculars / Microscope + Slide Prep Kit
   
• Lets kids engage the universe at all scales 

Average Price: $59.95

Buy Levenhuk LabZZ MTB3 Microscope & Telescope & Binoculars Kit on Amazon.com

You get kid-size versions of instruments to extend vision to the very big, the very faraway and the very small. A 2-inch aperture refractor telescope works at night for moon, planets and stars, and during the day for animals and sports. [Never point a telescope at the sun!] Note that 6x binoculars are made for little hands and faces. A three-objective microscope (150x, 450x and 900x) brings the subvisible to giant size.

Other Options:

            GeoSafari Talking Telescope

            Galileoscope Refractor Telescope Kit

[Read our Full Reviews and comparison of Best Telescopes for Kids]

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See our Best Telescopes for Hobbyists pages for full reviews 

After carefully looking at a variety of telescopes, we selected the ones that have enough horsepower to drive many years of satisfying observation, but that don’t break the bank.

Editors’ Choice

Celestron SkyProdigy 130

• Reflector / AltAz / Tripod / Go-To
   
• Easiest setup; totally self-aligning on the sky

Average price: $589.99

<img class=”pure-img lazy” big-src=”http://www.space.com/images/i/000/053/039/original/celestron-skyprodigy-130-telescope.jpg?1454522389?interpolation=lanczos-none&downsize=*:1400″ data-src=”http://www.space.com/images/i/000/053/039/i02/celestron-skyprodigy-130-telescope.jpg?1454522389?interpolation=lanczos-none&downsize=640:*” alt=”This telescope aligns itself to the stars in just 3 minutes and brings a lot of power and clarity to the table, letting beginners and experts alike lose themselves in the cosmos. Celestron SkyProdigy 130“/>

This telescope aligns itself to the stars in just 3 minutes and brings a lot of power and clarity to the table, letting beginners and experts alike lose themselves in the cosmos. Celestron SkyProdigy 130

Credit: Celestron

The Celestron SkyProdigy 130 is the first consumer telescope to offer fully automatic alignment. Once you set it up under the night sky, it takes about 3 minutes for the scope to find itself. Then you can use the wired remote keypad to drive this high-quality Newtonian reflector. The SkyProdigy comes with two 1.25-inch Kellner eyepieces (25 mm and 9 mm). The nicely machined focuser can also accept 2-inch eyepieces.

Alternate Editors’ Choice:

Orion SkyQuest XT8i IntelliScope

• Reflector / AltAz / Dobsonian
   
• Most “Big Bang” for your buck; largest aperture

Average price: $659.99

Buy Orion 10018 SkyQuest XT8i IntelliScope Dobsonian Telescope on Amazon.com

Much “Big Bang” for your buck, has this large aperture Dobsonian telescope.

Credit: Orion Telescopes and Binoculars

Orion’s SkyQuest is an 8-inch (203 mm) Dobsonian telescope. It’s a big light bucket with an excellent-quality primary mirror that’s great for hauling in the old, tired photons of distant galaxies and nebulae. As long as you don’t intend to take long-exposure astrophotos, the SkyQuest is a fabulous tool. Also, be aware that it’s a bit of a kit: You must screw together the altitude-azimuth mount, fit up the tilting optical tube and do a few more bits of assembly. But it’s fun to do, and the result is a wonderful scope that you can use for decades.

Also Consider:

            Levenhuk SkyMatic 135 GTA computerized Newtonian reflector

Levenhuk SkyMatic 135 GTA computerized Newtonian reflector

Credit: Dave Brody/Space.com

[Read our Full Reviews and comparison of Best Telescopes for Hobbyists and Learners]

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3. See our Best Small, Portable Telescopes for Travelers and City Dwellers pages for full reviews

Editors’ Choice:

Celestron Regal M2 100ED – “Spotting Scope”

• Refractor (tripod sold separately)
   
• Clearest and sharpest grab-and-go compact telescope

Average price: $849.95

Buy Celestron 52306 Regal M2 100ED Spotting Scope on Amazon.com

The Celestron Regal M2 100ED is a Space.com top pick for spotting scopes.

Credit: Dave Brody/Space.com

Loved for their rugged portability, spotting scopes are favored by daytime sports and outdoors enthusiasts. Now, Celestron brings you a spotting scope that is excellent for grab-and-go astronomy as well. The Regal M2 100ED can pull a lifetime of visual memories into its 19.25-inch (48.9 centimeters), 8.6-lb. (2.1 kilograms) frame. The M2’s body is cast of lightweight magnesium alloy. You’ll need to buy a tripod separately, and possibly a 1.25-inch astronomy eyepiece or two for skywatching.

Editors’ Budget Choice:

Levenhuk Blaze 90 Spotting Scope

• Refractor / Small Tripod
   
• Most cost-effective grab-and-go compact telescope

Average price: $214.95

Loved for their rugged portability, spotting scopes are favored by daytime sports and outdoors enthusiasts.

Credit: Dave Brody/Space.com

Levenhuk’s Blaze 90 Spotting Scope lets you pack 3.5 inches (9 cm) of starlight-snagging aperture into your go-anywhere bag. For about one-fifth the cost of Celestron’s M2 100ED, you can get about three-quarters the thrill if you buy the Levenhuk. Try pairing it with Orion’s heavy-duty model tripod and head for no-wiggle skywatching. The Blaze 90 comes in a highly functional field pouch that’s built of tough ballistic nylon.

Other Options:

            Celestron TravelScope 60 – National Park Edition

[Read our Full Reviews and comparison of Best Small, Portable Telescopes for Travelers and City Dwellers.]

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4. See our Best Telescope for Beginners (Easy to Use) pages for full reviews 

Editors’ Choice for Computer-Driven Scopes:

Celestron AstroFi 102 Mak-Cas Wi-Fi

• Maksutov-Cassegrain / AltAz Tripod / Go-To
• Most innovative, future proof and “digital”

Average price: $419.95

The Celestron AstroFi 102 computer-driven telescope.

Credit: Dave Brody/Space.com

Also comes as a refractor at the same price:

Celestron AstroFi 90 Refractor Wi-Fi

• Refractor / AltAz Tripod / Go-To

Average price: $419.95

Celestron AstroFi 90 Refractor Wi-Fi

Credit: Dave Brody/Space.com

The Celestron AstroFi telescopes take their observing orders from your Apple or Android smartphone or tablet via the free SkyPortal app [App Store or Google Play]. You won’t need access to a network; your new AstroFi scope is itself a network. It will even work where your cellular networks don’t. The 3.5-inch (90 mm) refractor is our choice for planet watching. The 4-inch (102 mm) Maksutov-Cassegrain hybrid wonderfully resolves tiny point-source stars. And there’s a slightly more expensive AstroFi 5-inch (130 mm) Newtonian reflector, as well. Just be a little careful not to bend the lightweight aluminum tripod.

Editors’ Choice for Manually Operated:

Orion StarBlast 6 or StarBlast 6i “IntelliScope”

• Reflector/ AltAz Rocket Box
• Simplest to use; gobbles big gulps of photons 

Average price: $339.99 (or $499.99 for IntelliScope model)

This simple-to-use tabletop Dobsonian comes out of the box ready to observe. The “IntelliScope” computer guides you to manually move the ‘scope to objects on the sky.

Credit: Orion Telescopes and Binoculars

If you want to escape your phone and concentrate on the sky, Orion’s StarBlast 6 Dobsonian reflector might be your ticket out. The 6-inch (15 cm) mirror is broad enough to gobble light waves from millions of years ago, or from just a few seconds past. Unlike many Dobsonians, the StarBlast pops out of its shipping box ready to work, which makes it a nice gift buy.

[Read our Full Reviews and comparison of Best Telescopes for Beginners (Easy to Use).]

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5. See our Best Inexpensive Telescopes (A Great Gift Idea) pages for full reviews 

5a. Editors’ Choice:

Astronomers Without Borders OneSky 130

• Reflector / AltAz “Rock and Roll” Turntable
•   Best gift under $200 and helps developing nations

Average price: $199.99

This clever pop-up Newtonian reflector gives you a remarkably large aperture and super-easy operation at very low cost. Nearly half your purchase price goes to support science education in developing nations.

Credit: Space.com – Jeremy Lips and Dave Brody

Give this OneSky telescope as a gift (even to yourself!) and you automatically make a donation to the nonprofit Astronomers Without Borders (AWB). Young science students a world away will benefit from enhanced education programs as you enjoy your astronomy hobby. We are all under one sky.

And you’ll be getting an extraordinarily good telescope: 5.1 inches (130 mm) of aperture, good-quality glass, two Plossl eyepieces and an innovative compact-expanding design. It’s a truss tube Newtonian reflector on a simple-to-work altitude-azimuth mount, with a built-in handle. We truly love this telescope.

5b. Also Consider:

Levenhuk Strike 80

• Refractor / AltAz Tripod
• A classic “spyglass” plus a colorful learner’s kit

Average price: $139.95

Buy Levenhuk Strike 80 NG Telescope achromatic refractor 80 mm on Amazon.com

Levenhuk Strike 80 NG Telescope

Credit: Dave Brody/Space.com

A durable optical tube, strong mount and stainless-steel tripod with accessory tray, along with two eyepieces and a Barlow lens, add up to excellent value. Levenhuk offers this 3-inch (80 mm) aperture refractor — not very different from old Galileo’s — on an altitude-azimuth yoke. It’s a simple and solid instrument.

Other Options:

            Celestron Cometron 114AZ Reflector / AltAz

            Levenhuk Skyline 130 x 900 EQ Reflector / Equatorial

            Celestron ExploraScope 60AZ NPF Edition Long Tube Refractor / AltAz

[Read our Full Reviews and comparison of these budget-minded Best Inexpensive Telescopes.]

The long view of astronomy

Here’s the deep truth of telescopes: It does not matter what price you pay to get into amateur astronomy. Telescopes gather light. And, yes, more light — or purer light — is better.

But once you tune in to the reality that the universe is coming directly to you — to meet you wherever you are, as long as you look up — you will never be the same. Once you start observing with a telescope, you will likely never stop. 

May the photons be with you.

130mm Aperture Newtonian Reflector Telescope with SkyAlign Go-To Computer Credit: Space.com

Reflector Telescopes: Newton Astride a Tripod

Bright guy, Sir Isaac Newton: He managed to distill the mechanics of our local universe down to three simple laws of motion. He developed much of mathematical calculus. And he harnessed the magnification properties of concave mirrors to drive a new type of telescope.

His new “reflecting” telescope solved a problem: It didn’t cause light to break apart into colors (as Galileo’s refractor did). It made for telescopes that could gulp more light for their length. In 1668, Newton opened up the universe for closer inspection.

Buy a Reflector: Celestron NextStar 130 SLT

Modernizing Newton: Celestron’s NexStar 130SLT

Over the past three and a half centuries, Newton’s Reflectors have evolved into comfortable, powerful, elegant instruments that are simple to use. Among the best we’ve found for under $500 is Celestron’s NexStar 130SLT.

That “130” refers to the aperture (“opening”) expressed in millimeters. This model is a recent upgrade from a smaller 114mm Celestron. It’s now more than 5 inches. Aperture is nearly everything in telescopes; more photons reach your eye, camera or spectroscope. And the more starlight you grab, the more illuminated your understanding of the cosmos.

Optics:

You’ll have many chances to be thus enlightened by the 130SLT. We found it’s aluminized glass mirror to be surprisingly well ground and polished for a scope in this price-range. A thin, but strong “spider” holds a well-milled secondary mirror securely in position to reflect photons through your eyepiece. Newton would be pleased.

Celestron supplies two nice eyepieces with the NexStar 130. The “wider” of the two, the 25mm, is about right to stare at galaxies or – with an added lunar filter – at the moon. The “tighter,” a 9mm, will show you larger details on planets. But you will probably want a higher power eyepiece (or a magnification doubling Barlow) to see phenomena like the moons of Jupiter casting shadows on the Big World’s face.

This NexStar is compatible with 2″ eyepieces. That opens up some great possibilities for wide field “space-walking” – a real feeling of being out there among them.  It also lends an element of future proofing; your next telescope (after this NexStar) is likely to crave 2” glass. And eyepieces can last for generations; you’ll pass them to your grandchildren.

Like cars and musical instruments, telescopes do need occasional tune-ups. Reflectors in particular must be “collimated” from time to time. Our NexStar showed up from the factory not needing adjustment. Its optical axis was nicely aligned to make sharp images. Stars (except for our Sun) are effectively point sources on the sky. If you notice stars starting to “bloom” in your eyepiece, it’s probably time to collimate.

Finding & Tracking Targets: Celestron’s “Go-To” Computer

Celestron’s SkyAlign system is a masterpiece. It lets you use objects in the night sky to set up the scope’s tracking without know which they actually are. Yes, I’m championing ignorance in saying this but that’s a huge improvement. In most other systems, you must know what star you’re looking at.

With SkyAlign, you don’t. In fact, you can even use a planet (it’s hard for beginners to tell the difference). You just need to level the tripod; then tell the system your rough location, plus the date and time. Then just introduce the telescope to any three bright lights (well, not an airplane or satellite) and the computer will be happy as a clam.

You will be too, as you slew around to your choice of 4000 objects; planets, galaxies, nebulae, stars and clusters. There aren’t as many in the database as some other beginner scope system. But as a practical matter, if you find time to observe even half of those 4k, you long since ceased being a beginner!

Easy to use

Our reviewers were happy the Celestron NexStar’s battery pack in located within the mount. That means no cable to wrap and tangle as the telescope moves. But, to be fair, an external “power tank” will hold much more charge for much longer observing and can power other devices (say, your laptop … or heated gloves!).

Set-up is dead simple. I’m a monkey-see/monkey-do type: I loved that there’s a cute, helpful online video. The tripod and mount are lightweight. Good for portability; maybe bad for durability. But only time will tell.

We did notice the images wiggle a bit for a second or so after the optical tube was nudged, a consequence of that relatively light duty mount and tripod. But telescope makers must trade-off something, somewhere, to stay in business.

And, when observing faint objects, there’s one actual benefit to a bit of “shimmer” or “dance”: Your eye and brain will work harder to build up a mental picture. You’ll actually see more small details if you “ping” the telescope by tapping your eyepiece, or the optical tube, gently. Try it!

This telescope isn’t for targets on Earth. It’s Newtonian design demands that you stand or sit at the side of the optical tube.  And the image is inverted. So it’s not a point and shoot spyglass. [For that, you would want a Refractor or Hybrid.] But take the NexStar 130 out on star-date night and your view will be truly stellar.

With a 130mm (5inches) of beefy main mirror, we didn’t expect this unit to be a featherweight. But its 18lbs is quite doable, even if you have a long-ish carry to your dark sky site. And the whole rig is small enough for most cars if you’re outbound to escape local light pollution.

Help & Support

If, like me, you’re fundamentally lazy, it’s nice to have a computerized “go-to” scope out there under the stars. But it’s even nicer to know what you could see hours or days before your observing session. Celestron wants to help you here too: They’ve provided a disk of “The Sky” astronomy software, one of the best software planetariums out there for laptop, notebook or desktop computers.

And speaking of computers, Celestron also gives you a 2^nd disk with utilities to control your 130. [Sorry no tablet support … yet.] To pull this trick off, you will need the correct cable.  It’s available (but not included) from Celestron. Order it online.

Celestron’s telephone support can be a bit frustrating. But our review crew loved their website. It’s packed with knowledge bases, set-up videos, downloads and complete issue resolution procedures. Any beginner with a web connection and time to spend at Celestron.com won’t be a beginner for long.

Enjoy!

Out under the night sky, with million year-old photons coming to rest on the back of your eyeball, you will sense his presence; Old Sir Isaac Newton, standing there at your shoulder.

Buy a Reflector: Celestron NextStar 130 SLT

More beginner telescope types:

Hybrid:  Compact Power & Cool Design

Refractor:  Galileo’s Elegant Simplicity

Dobsonian:  A Universe For Every Person

Beginner Telescope Buying Guide (Main Page)

For more choices, please check this interactive chart comparing our top ten telescope picks for beginners.

Or look at some accessories – and lots of other space gear–in our SPACE.com Store.

Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

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Editor’s note:  The next lunar eclipse will be a total lunar eclipse on Sept. 27, 2015. It will occur while the moon is at perigee, making it a rare Supermoon Blood Moon lunar eclipse. Such an event won’t happen again until 2033.

A total lunar eclipse occurs when the moon passes completely beneath Earth’s shadow. 

Photos: The Long Total Lunar Eclipse of June 2011

Video: Inside the June 15 Total Lunar Eclipse

Photos: Amazing Views of November 2011 Solar Eclipse

More Infographics

Dust Cloud Around the Moon Explained (Infographic)

Inside Star Trek’s Galileo Shuttlecraft (Infographic)

Inside a Neutron Star (Infographic)

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Comet Swift-Tuttle, whose debris creates the Perseids, is the largest object known to make repeated passes near Earth. Its nucleus is about 6 miles (9.7 kilometers) across, roughly equal to the object that wiped out the dinosaurs.

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Back in the early 1990s, astronomer Brian Marsden calculated that Swift-Tuttle might actually hit Earth on a future pass. More observations quickly eliminated all possibility of a collision. Marsden found, however, that the comet and Earth might experience a cosmic near miss (about a million miles) in 3044.

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Perseid meteoroids (which is what they’re called while in space) are fast. They enter Earth’s atmosphere (and are then called meteors) at roughly 133,200 mph (60 kilometers per second) relative to the planet. Most are the size of sand grains; a few are as big as peas or marbles. Almost none hit the ground, but if one does, it’s called a meteorite.

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When a Perseid particle enters the atmosphere, it compresses the air in front of it, which heats up. The meteor, in turn, can be heated to more than 3,000 degrees Fahrenheit (1,650 Celsius). The intense heat vaporizes most meteors, creating what we call shooting stars. Most become visible at around 60 miles up (97 kilometers). Some large meteors splatter, causing a brighter flash called a fireball, and sometimes an explosion that can often be heard from the ground.

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Comet Swift-Tuttle has many comet kin. Most originate in the distant Oort cloud, which extends nearly halfway to the next star. The vast majority never visit the inner solar system. But a few, like Swift-Tuttle, have been gravitationally booted onto new trajectories, possibly by the gravity of a passing star long ago.

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Perseid meteoroids (and if you’ve been following along, you know these are things in space before they hit Earth’s atmosphere) are anywhere from 60 to 100 miles apart, even at the densest part of the river of debris left behind by comet Swift-Tuttle. That river, in fact, is more like many streams, each deposited during a different pass of the comet on its 130-year orbit around the Sun. The material drifts through space and, in fact, orbits the Sun on roughly the same path as the comet while also spreading out over time.

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As Earth rotates, the side facing the direction of its orbit around the Sun tends to scoop up more space debris. This part of the sky is directly overhead at dawn. For this reason, the Perseids and other meteor showers (and also random shooting stars in general) are usually best viewed in the predawn hours.

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Comet Swift-Tuttle was last seen in 1992, an unspectacular pass through the inner solar system that required binoculars to enjoy. Prior to that, it had last been seen in the year it was “discovered” by American astronomers Lewis Swift and Horace Tuttle, 1862. Abraham Lincoln was president.

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Swift-Tuttle’s orbit has been traced back nearly 2,000 years and is now thought to be the same comet that was observed in 188 AD and possibly even as early as 69 BC.

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More Countdowns

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Our solar system is a vast place, with lots of mostly empty space between planets. But out there are comets, asteroids and more rocky, frozen objects (including dwarf planets) yet to be discovered in the Kuiper Belt and Oort Cloud. Credit: NASA

The solar system is made up of the sun and everything that orbits around it, including planets, moons, asteroids, comets and meteoroids. It extends from the sun, called Sol by the ancient Romans, and goes past the four inner planets, through the Asteroid Belt to the four gas giants and on to the disk-shaped Kuiper Belt and far beyond to the giant, spherical Oort Cloud and the teardrop-shaped heliopause. Scientists estimate that the edge of the solar system is about 9 billion miles (15 billion kilometers) from the sun.

Discovery

For millennia, astronomers have followed points of light that seemed to move among the stars. The ancient Greeks named these planets, meaning “wanderers.” Mercury, Venus, Mars, Jupiter and Saturn were known in antiquity, and the invention of the telescope added the Asteroid Belt, Uranus, Neptune, Pluto and many of these worlds’ moons. The dawn of the space age saw dozens of probes launched to explore our system, an adventure that continues today. The discovery of Eris kicked off a rash of new discoveries of dwarf planets. [Infographic: Structure of the Solar System]

Astronomers are now hunting for another planet in our solar system, a true ninth planet, after evidence of its existence was unveiled on Jan. 20, 2016. The so-called “Planet Nine,” as scientists are calling it, is about 10 times the mass of Earth and 5,000 times the mass of Pluto. 

[The Evidence for ‘Planet Nine’ in Our Solar System (Gallery)]

Formation

Many scientists think our solar system formed from a giant, rotating cloud of gas and dust known as the solar nebula. As the nebula collapsed because of its gravity, it spun faster and flattened into a disk. Most of the material was pulled toward the center to form the sun. Other particles within the disk collided and stuck together to form asteroid-sized objects named as planetesimals, some of which combined to become the asteroids, comets, moons and planets.

The solar wind from the sun was so powerful that it swept away most of the lighter elements, such as hydrogen and helium, from the innermost planets, leaving behind mostly small, rocky worlds. The solar wind was much weaker in the outer regions, however, resulting in gas giants made up mostly of hydrogen and helium.

The sun

The sun is by far the largest object in our solar system, containing 99.8 percent of the solar system’s mass. It sheds most of the heat and light that makes life possible on Earth and possibly elsewhere. Planets orbit the sun in oval-shaped paths called ellipses, with the sun slightly off-center of each ellipse.

Uncle Milton Solar System In My Room. Buy Here
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Inner solar system

The four inner four planets — Mercury, Venus, Earth and Mars — are made up mostly of iron and rock. They are known as terrestrial or earthlike planets because of their similar size and composition. Earth has one natural satellite — the moon— and Mars has two moons — Deimos and Phobos.

Between Mars and Jupiter lies the Asteroid Belt. Asteroids are minor planets, and scientists estimate there are more than 750,000 of them with diameters larger than three-fifths of a mile (1 km) and millions of smaller asteroids. The dwarf planet Ceres, about 590 miles (950 km) in diameter, resides here. A number of asteroids have orbits that take them closer into the solar system that sometimes lead them to collide with Earth or the other inner planets.

Outer solar system

The outer planets — Jupiter, Saturn, Uranus and Neptune — are giant worlds with thick outer layers of gas. Nearly all their mass is made up of hydrogen and helium, giving them compositions like that of the sun. Beneath these outer layers, they have no solid surfaces — the pressure from their thick atmospheres liquefy their insides, although they might have rocky cores. Rings of dust, rock, and ice encircle all these giants, with Saturn’s being the most famous.

Comets are often known as dirty snowballs, and consist mainly of ice and rock. When a comet’s orbit takes it close to the sun, some of the ice in its central nucleus turns into gas that shoots out of the comet’s sunlit side, which the solar wind carries outward to form into a long tail. Short-period comets that complete their orbits in less than 200 years are thought to originate from the disk-shaped Kuiper Belt, while long-period comets that take more than 200 years to return are thought to come from the spherical Oort Cloud.

Give Me Some Space 24″x36″ Posters. Buy Here
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Trans-Neptunian region

Astronomers had long suspected that a band of icy material known as the Kuiper Belt existed past the orbit of Neptune extending from about 30 to 55 times the distance of Earth to the sun, and from the last decade of the 20th century up to now, they have found more than a thousand of such objects. Scientists estimate the Kuiper Belt is likely home to hundreds of thousands of icy bodies larger than 60 miles (100 km) wide, as well as an estimated trillion or more comets.

Pluto, now considered a dwarf planet, dwells in the Kuiper Belt. It is not alone — recent additions include Makemake, Haumea and Eris. Another Kuiper Belt object dubbed Quaoar is probably massive enough to be considered a dwarf planet, but it has not been classified as such yet. Sedna, which is about three-fourths the size of Pluto, is the first dwarf planet discovered in the Oort Cloud. NASA’s New Horizons mission performed history’s first flyby of the Pluto system on July 14, 2015, and continues to explore the Kuiper Belt. [Related: New Horizons’ Pluto Flyby: Latest News, Images and Video]

[‘Planet Nine’: Facts About the Mysterious Solar System World (Infographic)]

The Oort Cloud lies well past the Kuiper Belt, and theoretically extends from 5,000 to 100,000 times the distance of Earth to the sun, and is home to up to 2 trillion icy bodies, according to NASA. Past the Oort Cloud is the very edge of the solar system, the heliosphere, a vast, teardrop-shaped region of space containing electrically charged particles given off by the sun. Many astronomers think that the limit of the heliosphere, known as the heliopause, is about 9 billion miles (15 billion km) from the sun.

Additional reporting by Nola Taylor Redd, Space.com Contributor

Additional resource

Learn more about the solar system: