Comets - Blog Posts

A Geminid meteor streaks across the sky as the Soyuz TMA-19M spacecraft is rolled out by train to the launch pad at the Baikonur Cosmodrome on Sunday, Dec. 13, 2015, in Kazakhstan. Credit: NASA/Joel Kowsky

Make a Wish! How to See the Geminid Meteor Shower

Every December, we have a chance to see one of our favorite meteor showers – the Geminids. To help you prepare, we’ve answered some of your most commonly asked questions. Happy viewing, stargazers!

These radar images of near-Earth object 3200 Phaethon were generated by astronomers at the National Science Foundation's Arecibo Observatory on Dec. 17, 2017. Observations of Phaethon were conducted at Arecibo from Dec. 15 through 19, 2017. At time of closest approach on Dec. 16 at 3 p.m. PST (6 p.m. EST, 2300 UTC), the asteroid was about 6.4 million miles (10.3 million kilometers) away, or about 27 times the distance from Earth to the Moon. Credit: Arecibo Observatory/NASA/NSF

What are the Geminids?

The Geminids are caused by debris from a celestial object known as 3200 Phaethon striking Earth’s atmosphere. Phaethon’s origin is the subject of some debate. Some astronomers consider it to be an extinct comet, based on observations showing some small amount of material leaving its surface. Others argue that it has to be an asteroid because of its orbit and its similarity to the main-belt asteroid Pallas.

All meteors appear to come from the same place in the sky, which is called the radiant. The Geminids appear to radiate from a point in the constellation Gemini, hence the name “Geminids.” The graphic shows the radiants of 388 meteors with speeds of 35 km/s observed by the NASA Fireball Network in December 2020. All the radiants are in Gemini, which means they belong to the Geminid shower. Credit: NASA

Why are they called the Geminids?

All meteors associated with a shower have similar orbits, and they all appear to come from the same place in the sky, which is called the radiant. The Geminids appear to radiate from a point in the constellation Gemini, hence the name “Geminids.”

A Geminid streaks across the sky in this photo from December 2019. Credit: NASA

When is the best time to view them?

The Geminid meteor shower is active for much of December, but the peak will occur during the night of Dec. 13 into the morning of Dec. 14, 2023. Meteor rates in rural areas can be upwards of one per minute this year with minimal moonlight to interfere.

What do I need to see them?

As with all meteor showers, all you need is a clear sky, darkness, a bit of patience, and perhaps warm outerwear and blankets for this one. You don’t need to look in any particular direction, as meteors can generally be seen all over the sky. If you want to take photographs, check out these helpful tips.

An infographic based on 2019’s meteor camera data for the Geminids. Credit: NASA

Do you have any advice to help me see the Geminids better?

Find the darkest place you can and give your eyes about 30 minutes to adapt to the dark. Avoid looking at your cell phone, as it will disrupt your night vision. Lie flat on your back and look straight up, taking in as much sky as possible.

A Geminid streaks across the sky in this photo from December 2011. Credit: NASA

What will the meteors look like?

According to Bill Cooke, lead for the Meteoroid Environment Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama, “Most meteors appear to be colorless or white, however the Geminids appear with a greenish hue. They’re pretty meteors!” Depending on the meteor’s chemical composition, the meteor will emit different colors when burned in the Earth’s atmosphere. Oxygen, magnesium, and nickel usually produce green.

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The 2021 Perseid Meteor Shower Is Here!

Image Credit: NASA/Bill Ingalls 

The Perseids are at their peak this week!

The Perseid meteor shower, one of the biggest meteor showers of the year, will be at its brightest early in the morning on Thursday, August 12, 2021 and Friday, August 13, 2021. Read on for some tips on how to watch the night sky this week – and to find out: what exactly are the Perseids, anyway?

Credit: NASA/Bill Ingalls

Your best chance to spot the Perseids will be between 2 AM and dawn (local time) the morning of August 12 or 13. Find a dark spot, avoid bright lights (yes, that includes your phone) and get acclimated to the night sky.

Your eyes should be at peak viewing capacity after about 30 minutes; with a clear, dark sky, you could see more than 40 Perseids an hour! If you’re not an early bird, you can try and take a look soon after sunset (around 9 PM) on the 12th, though you may not see as many Perseids then.

Credit: NASA/MEO

If it’s too cloudy, or too bright, to go skywatching where you are, just stay indoors and watch the Perseids online!

Our Meteor Watch program will be livestreaming the Perseids from Huntsville, Alabama on Facebook (weather permitting), starting around 11 p.m. EDT on August 11 and continuing through sunrise.

So… why are they called the Perseids?

Because all of a meteor shower’s meteors have similar orbits, they appear to come from the same place in the sky – a point called the radiant. 

The radiant for the Perseids, as you might guess from the name, is in the constellation Perseus, found near Aries and Taurus in the night sky.

But they’re not actually coming from Perseus, right?

Credit: NASA/Joel Kowsky

Right! The Perseids are actually fragments of the comet Swift-Tuttle, which orbits within our solar system.

If you want to learn more about the Perseids, visit our Watch the Skies blog or check out our monthly “What’s Up” video series. Happy viewing!

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Whilst practicing solar distancing, Parker Solar Probe caught this rare glimpse of the twin tails on comet NEOWISE.☄

The twin tails are seen more clearly in this WISPR instrument processed image, which increased contrast and removed excess brightness from scattered sunlight, revealing more de-"tails". C/2020 F3 NEOWISE was discovered by our Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), on March 27. Since it's discovery the comet has been spotted by several NASA spacecraft, including Parker Solar Probe, NASA’s Solar and Terrestrial Relations Observatory, the ESA/NASA Solar and Heliospheric Observatory, and astronauts aboard the International Space Station.

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Get Ready Stargazers: The Geminids Are Here!

The Geminid meteor shower, one of the biggest meteor showers of the year, will peak this weekend, December 13 to 14. We get a lot of questions about the Geminids—so we’ve put together some answers to the ones we’re most commonly asked. Take a look!  

What are the Geminids?

The Geminids are pieces of debris from an asteroid called 3200 Phaethon. Earth runs into Phaethon’s debris stream every year in mid-December, causing meteors to fly from the direction of the constellation Gemini – hence the name “Geminids.”  

Image Credit: Arecibo Observatory/NASA/NSF

When is the best time to view them?

This year, the peak is during the overnight hours of December 13 and into the morning of December 14. Viewing should still be good on the night of December 14 into the early morning hours of the 15th. Weather permitting, the Geminids can be viewed from around midnight to 4 a.m. local time. The best time to see them is around 2 a.m. your local time on December 14, when the Geminid radiant is highest in your night sky. The higher the radiant – the celestial point in the sky from which meteors appear to originate – rises into the sky, the more meteors you are likely to see.

Image Credit & Copyright: Jeff Dai

What is the best way to see them?

Find the darkest place you can and give your eyes about 30 minutes to adapt to the dark. Avoid looking at your cell phone, as it will disrupt your night vision. Lie flat on your back and look straight up, taking in as much sky as possible. You will soon start to see the Geminid meteors!

Image Credit: NASA/Bill Dunford

Can you see the Geminids from anywhere in the world?

The Geminids are best observed in the Northern Hemisphere, but no matter where you are in the world (except Antarctica), some Geminids will be visible.

Image Credit: Jimmy Westlake

How many Geminids can I expect to see?

Under dark, clear skies, the Geminids can produce up to 120 meteors per hour – but this year, a bright, nearly full moon will hinder observations of the shower. Still, observers can hope to see up to 30 meteors per hour. Happy viewing!  

Image Credit & Copyright: Yuri Beletsky

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Galactic Ghouls and Stellar Screams

A quiet, starry night sky might not seem like a very eerie spectacle, but space can be a creepy place! Monsters lurk in the shadowy depths of the universe, sometimes hidden in plain sight. Many of them are invisible to our eyes, so we have to use special telescopes to see them. Read on to discover some of these strange cosmic beasts, but beware — sometimes fact is scarier than fiction.

Monster Black Holes ⚫

You know those nightmares where no matter how fast you try to run you never seem to get anywhere? Black holes are a sinister possible version of that dream — especially because they’re real! If you get too close to a black hole, there is no possibility of escape.

Just last year our Fermi Gamma-ray Space Telescope traced an otherworldly ghost particle back to one of these monster black holes, providing additional insight into the many signals we’re picking up from some of the most feared creatures in the cosmic deep.

But it gets worse. Our Hubble Space Telescope revealed that these things are hidden in the hearts of nearly every galaxy in the universe. That means supermassive black holes lurk in the shadows of the night sky in every direction you look!

A Hazy Specter 👻

This fiendish specter lives in the center of the Milky Way, haunting our galaxy’s supermassive black hole. But it’s not as scary as it looks! Our SOFIA observatory captured streamlines tracing a magnetic field that appears to be luring most of the material quietly into orbit around the black hole. In other galaxies, magnetic fields seem to be feeding material into hungry black holes — beware! Magnetic fields might be the answer to why some black holes are starving while others are feasting.

Bats in the Belfry 🦇

The universe has bats in the attic! Hubble spotted the shadow of a giant cosmic bat in the Serpens Nebula. Newborn stars like the one at the center of the bat, called HBC 672, are surrounded by disks of material, which are hard to study directly. The shadows they cast, like the bat, can clue scientists in on things like the disk’s size and density. Our solar system formed from the same type of disk of material, but we can only see the end result of planet building here — we want to learn more about the process!

Jack-o-lantern Sun 🎃

A jack-o-lantern in space?! Our Solar Dynamics Observatory watches the Sun at all times, keeping a close eye on space weather. In October 2014, the observatory captured a chilling image of the Sun with a Halloweenish face!

Skull Comet 💀

On Halloween a few years ago, an eerie-looking object known as 2015 TB145 sped across the night sky. Scientists observing it with our Infrared Telescope Facility determined that it was most likely a dead comet. It’s important to study objects like comets and asteroids because they’re dangerous if they cross Earth’s path — just ask the dinosaurs!

Halloween Treat 🍬

Trick-or-treat! Add a piece of glowing cosmic candy to your Halloween haul, courtesy of Hubble! This image shows the Saturn Nebula, formed from the outer layers ejected by a dying star, destined to be recycled into later generations of stars and planets. Our Sun will experience a similar fate in around five billion years.

Witch’s Broom Nebula 🧹

Massive stars are in for a more fiery fate, as the Witch's Broom Nebula shows. Hubble’s close-up look reveals wisps of gas — shrapnel leftover from a supernova explosion. Astronomers believe that a couple of supernovae occur each century in galaxies like our own Milky Way.

Zombie Stars 🧟

Supernovae usually herald the death of a star, but on a few occasions astronomers have found “zombie stars” left behind after unusually weak supernovae. Our Nuclear Spectroscopic Telescope Array (NuSTAR) has even spotted a mysterious glow of high-energy X-rays that could be the “howls” of dead stars as they feed on their neighbors.

Intergalactic Ghost Towns 🏚️

The universe is brimming with galaxies, but it’s also speckled with some enormous empty pockets of space, too. These giant ghost towns, called voids, may be some of the largest things in the cosmos, and since the universe is expanding, galaxies are racing even farther away from each other all the time! Be grateful for your place in space — the shadowy patches of the universe are dreadful lonely scenes.

Mysterious Invisible Force 🕵️‍♀️

Some forces are a lot creepier than floorboards creaking or a door slamming shut unexpectedly when you’re home alone. Dark energy is a mysterious antigravity pressure that our Wide Field Infrared Survey Telescope (WFIRST) is going to help us understand. All we know so far is that it’s present everywhere in the cosmos (even in the room with you as you read this) and it controls the fate of the universe, but WFIRST will study hundreds of millions of galaxies to figure out just what dark energy is up to.

Want to learn some fun ways to celebrate Halloween in (NASA) style? Check out this link!

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TESS’s first-year of planet-hunting was out of this world

Have you ever looked up at the night sky and wondered ... what other kinds of planets are out there? Our Transiting Exoplanet Survey Satellite (TESS) just spent its first year bringing us a step closer to exploring the planets around the nearest and brightest stars in the southern sky and is now doing the same in the north.

TESS has been looking for dips in the brightness of stars that could be a sign of something we call “transits.” A transit happens when a planet passes between its star and us. It’s like when a bug flies in front of a light bulb. You may not notice the tiny drop in brightness when the bug blocks some of the light from reaching your eyes, but a sensitive camera could. The cameras on TESS are designed to detect those tiny drops in starlight caused by a transiting planet many light-years away.

In the last year TESS has found 24 planets and more than 900 new candidate planets. And TESS is only halfway through its goal of mapping over three-fourths of our skies, which means there’s plenty more to discover!

TESS has been looking for planets around the closest, brightest stars because they will be the best planets to explore more thoroughly with future missions. We can even see a few of these stars with our own eyes, which means we’ve been looking at these planets for millions of years and didn’t even know it.

We spent thousands of years staring at our closest neighbor, the Moon, and asking questions: What is it like? Could we live there? What is it made of (perhaps cheese?). Of course, now we can travel to the Moon and explore it ourselves (turns out, not made of cheese).

But for the worlds TESS is discovering, the commute to answer those questions would be killer. It took 35 years for Voyager 1 to cross into interstellar space (the region between stars), and it’s zipping along at over 38,000 mph! At that rate it would take more than a half-a-million years to reach the nearest stars and planets that TESS is discovering.

While exploring these distant worlds in person isn’t an option, we have other ways of learning what they are like. TESS can tell us where a planet is, its size and its overall temperature, but observatories on the ground and in space like our upcoming James Webb Space Telescope will be able to learn even more — like whether or not a planet has an atmosphere and what it’s made of.

Here are a few of the worlds that our planet hunter discovered in the last year.

Earth-Sized Planet

The first Earth-sized planet discovered by TESS is about 90% the size of our home planet and orbits a star 53 light-years away. The planet is called HD 21749 c (what a mouthful!) and is actually the second planet TESS has discovered orbiting that star, which you can see in the southern constellation Reticulum.

The planet may be Earth-sized, but it would not be a pleasant place to live. It’s very close to its star and could have a surface temperature of 800 degrees Fahrenheit, which would be like sitting inside a commercial pizza oven.

Water World?

The other planet discovered in that star system, HD 21749 b, is about three times Earth’s size and orbits the star every 36 days. It has the longest orbit of any planet within 100 light-years of our solar system detected with TESS so far.

The planet is denser than Neptune, but isn’t made of rock. Scientists think it might be a water planet or have a totally new type of atmosphere. But because the planet isn’t ideal for follow-up study, for now we can only theorize what the planet is actually like. Could it be made of pudding? Maybe … but probably not.

Magma World

One of the first planets TESS discovered, called LHS 3844 b, is roughly Earth’s size, but is so close to its star that it orbits in just 11 hours. For reference, Mercury, which is more than two and a half times closer to the Sun than we are, completes an orbit in just under three months.

Because the planet is so close to its star, the day side of the planet might get so hot that pools and oceans of magma form on its rocky surface, which would make for a rather unpleasant day at the beach.    

TESS’s Smallest Planet

The smallest planet TESS has discovered, called L 98-59 b, is between the size of Earth and Mars and orbits its star in a little over two days. Its star also hosts two other TESS-discovered worlds.

Because the planet lies so close to its star, it gets 22 times the radiation we get here on Earth. Yikes! It is also not located in its star’s habitable zone, which means there probably isn’t any liquid water on the surface. Those two factors make it an unlikely place to find life, but scientists believe it will be a good candidate for follow-up studies by other telescopes.

Other Data

While TESS’s team is hunting for planets around close, bright stars, it’s also collecting information on all sorts of other things. From transits around dimmer, farther stars to other objects in our solar system and events outside our galaxy, data from TESS can help astronomers learn a lot more about the universe. Comets and black holes and supernovae, oh my!

Interested in joining the hunt? TESS’s data are released online, so citizen scientists around the world can help us discover new worlds and better understand our universe.

Stay tuned for TESS’s next year of science as it monitors the stars that more than 6.5 billion of us in the northern hemisphere see every night.

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What's That Space Rock?

The path through the solar system is a rocky road. Asteroids, comets, Kuiper Belt Objects—all kinds of small bodies of rock, metal and ice are in constant motion as they orbit the Sun. But what’s the difference between them, anyway? And why do these miniature worlds fascinate space explorers so much? The answer is profound: they may hold the keys to better understanding where we all come from. Here’s 10 things to know about the solar system this week:

This picture of Eros, the first of an asteroid taken from an orbiting spacecraft, came from our NEAR mission in February 2000. Image credit: NASA/JPL

1. Asteroids

Asteroids are rocky, airless worlds that orbit our Sun. They are remnants left over from the formation of our solar system, ranging in size from the length of a car to about as wide as a large city. Asteroids are diverse in composition; some are metallic while others are rich in carbon, giving them a coal-black color. They can be “rubble piles,” loosely held together by their own gravity, or they can be solid rocks.

Most of the asteroids in our solar system reside in a region called the main asteroid belt. This vast, doughnut-shaped ring between the orbits of Mars and Jupiter contains hundreds of thousands of asteroids, maybe millions. But despite what you see in the movies, there is still a great deal of space between each asteroid. With all due respect to C3PO, the odds of flying through the asteroid belt without colliding with one are actually pretty good.

Other asteroids (and comets) follow different orbits, including some that enter Earth’s neighborhood. These are called near-Earth objects, or NEOs. We can actually keep track of the ones we have discovered and predict where they are headed. The Minor Planet Center (MPC) and Jet Propulsion Laboratory’s Center for Near Earth Object Studies (CNEOS) do that very thing. Telescopes around the world and in space are used to spot new asteroids and comets, and the MPC and CNEOS, along with international colleagues, calculate where those asteroids and comets are going and determine whether they might pose any impact threat to Earth.

For scientists, asteroids play the role of time capsules from the early solar system, having been preserved in the vacuum of space for billions of years. What’s more, the main asteroid belt may have been a source of water—and organic compounds critical to life—for the inner planets like Earth.

The nucleus of Comet 67P/Churyumov-Gerasimenko, as seen in January 2015 by the European Space Agency’s Rosetta spacecraft. Image credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

2. Comets

Comets also orbit the Sun, but they are more like snowballs than space rocks. Each comet has a center called a nucleus that contains icy chunks of frozen gases, along with bits of rock and dust. When a comet’s orbit brings it close to the Sun, the comet heats up and spews dust and gases, forming a giant, glowing ball called a coma around its nucleus, along with two tails – one made of dust and the other of excited gas (ions). Driven by a constant flow of particles from the Sun called the solar wind, the tails point away from the Sun, sometimes stretching for millions of miles.

While there are likely billions of comets in the solar system, the current confirmed number is 3,535. Like asteroids, comets are leftover material from the formation of our solar system around 4.6 billion years ago, and they preserve secrets from the earliest days of the Sun’s family. Some of Earth’s water and other chemical constituents could have been delivered by comet impacts.

An artist re-creation of a collision in deep space. Image credit: NASA/JPL-Caltech

3. Meteoroids

Meteoroids are fragments and debris in space resulting from collisions among asteroids, comets, moons and planets. They are among the smallest “space rocks.” However, we can actually see them when they streak through our atmosphere in the form of meteors and meteor showers.

This photograph, taken by an astronaut aboard the International Space Station, provides the unusual perspective of looking down on a meteor as it passes through the atmosphere. The image was taken on Aug. 13, 2011, during the Perseid meteor shower that occurs every August. Image credit: NASA

4. Meteors

Meteors are meteoroids that fall through Earth’s atmosphere at extremely high speeds. The pressure and heat they generate as they push through the air causes them to glow and create a streak of light in the sky. Most burn up completely before touching the ground. We often refer to them as “shooting stars.” Meteors may be made mostly of rock, metal or a combination of the two.

Scientists estimate that about 48.5 tons (44,000 kilograms) of meteoritic material falls on Earth each day.

The constellation Orion is framed by two meteors during the Perseid shower on Aug. 12, 2018 in Cedar Breaks National Monument, Utah. Image credit: NASA/Bill Dunford

5. Meteor Showers

Several meteors per hour can usually be seen on any given night. Sometimes the number increases dramatically—these events are termed meteor showers. They occur when Earth passes through trails of particles left by comets. When the particles enter Earth’s atmosphere, they burn up, creating hundreds or even thousands of bright streaks in the sky. We can easily plan when to watch meteor showers because numerous showers happen annually as Earth’s orbit takes it through the same patches of comet debris. This year’s Orionid meteor shower peaks on Oct. 21.

An SUV-sized asteroid, 2008TC#, impacted on Oct. 7, 2008, in the Nubian Desert, Northern Sudan. Dr. Peter Jenniskens, NASA/SETI, joined Muawia Shaddas of the University of Khartoum in leading an expedition on a search for samples. Image credit: NASA/SETI/P. Jenniskens

6. Meteorites

Meteorites are asteroid, comet, moon and planet fragments (meteoroids) that survive the heated journey through Earth’s atmosphere all the way to the ground. Most meteorites found on Earth are pebble to fist size, but some are larger than a building.

Early Earth experienced many large meteorite impacts that caused extensive destruction. Well-documented stories of modern meteorite-caused injury or death are rare. In the first known case of an extraterrestrial object to have injured a human being in the U.S., Ann Hodges of Sylacauga, Alabama, was severely bruised by a 8-pound (3.6-kilogram) stony meteorite that crashed through her roof in November 1954.

The largest object in the asteroid belt is actually a dwarf planet, Ceres. This view comes from our Dawn mission. The color is approximately as it would appear to the eye. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

7. Dwarf Planets

Don’t let the name fool you; despite their small size, dwarf planets are worlds that are just as compelling as their larger siblings. Dwarf planets are defined by astronomers as bodies massive enough to be shaped by gravity into a round or nearly round shape, but they don’t have enough of their own gravitational muscle to clear their path of other objects as they orbit the Sun. In our solar system, dwarf planets are mostly found in the Kuiper Belt beyond Neptune; Pluto is the best-known example. But the largest object in the asteroid belt is the dwarf planet Ceres. Like Pluto, Ceres shows signs of active geology, including ice volcanoes.

8. Kuiper Belt Objects

The Kuiper Belt is a disc-shaped region beyond Neptune that extends from about 30 to 55 astronomical units -- that is, 30 to 55 times the distance from the Earth to the Sun. There may be hundreds of thousands of icy bodies and a trillion or more comets in this distant region of our solar system.

An artist's rendition of the New Horizons spacecraft passing by the Kuiper Belt Object MU69 in January 2019. Image credits: NASA/JHUAPL/SwRI

Besides Pluto, some of the mysterious worlds of the Kuiper Belt include Eris, Sedna, Quaoar, Makemake and Haumea. Like asteroids and comets, Kuiper Belt objects are time capsules, perhaps kept even more pristine in their icy realm.

This chart puts solar system distances in perspective. The scale bar is in astronomical units (AU), with each set distance beyond 1 AU representing 10 times the previous distance. One AU is the distance from the Sun to the Earth, which is about 93 million miles or 150 million kilometers. Neptune, the most distant planet from the Sun, is about 30 AU. Image credit: NASA/JPL-Caltech

9. Oort Cloud Objects

The Oort Cloud is a group of icy bodies beginning roughly 186 billion miles (300 billion kilometers) away from the Sun. While the planets of our solar system orbit in a flat plane, the Oort Cloud is believed to be a giant spherical shell surrounding the Sun, planets and Kuiper Belt Objects. It is like a big, thick bubble around our solar system. The Oort Cloud’s icy bodies can be as large as mountains, and sometimes larger.

This dark, cold expanse is by far the solar system’s largest and most distant region. It extends all the way to about 100,000 AU (100,000 times the distance between Earth and the Sun) – a good portion of the way to the next star system. Comets from the Oort Cloud can have orbital periods of thousands or even millions of years. Consider this: At its current speed of about a million miles a day, our Voyager 1 spacecraft won’t reach the Oort Cloud for more than 300 years. It will then take about 30,000 years for the spacecraft to traverse the Oort Cloud, and exit our solar system entirely.

This animation shows our OSIRIS-REx spacecraft collecting a sample of the asteroid Bennu, which it is expected to do in 2020. Image credit: NASA/Goddard Space Flight Center

10. The Explorers

Fortunately, even though the Oort Cloud is extremely distant, most of the small bodies we’ve been discussing are more within reach. In fact, NASA and other space agencies have a whole flotilla of robotic spacecraft that are exploring these small worlds up close. Our mechanical emissaries act as our eyes and hands in deep space, searching for whatever clues these time capsules hold.

A partial roster of our current or recent missions to small, rocky destinations includes:

OSIRIS-REx – Now approaching the asteroid Bennu, where it will retrieve a sample in 2020 and return it to the Earth for close scrutiny.

New Horizons – Set to fly close to MU69 or “Ultima Thule,” an object a billion miles past Pluto in the Kuiper Belt on Jan. 1, 2019. When it does, MU69 will become the most distant object humans have ever seen up close.

Psyche – Planned for launch in 2022, the spacecraft will explore a metallic asteroid of the same name, which may be the ejected core of a baby planet that was destroyed long ago.

Lucy – Slated to investigate two separate groups of asteroids, called Trojans, that share the orbit of Jupiter – one group orbits ahead of the planet, while the other orbits behind. Lucy is planned to launch in 2021.

Dawn – Finishing up a successful seven-year mission orbiting planet-like worlds Ceres and Vesta in the asteroid belt.

Plus these missions from other space agencies:

The Japan Aerospace Exploration Agency (JAXA)’s Hayabusa2– Just landed a series of small probes on the surface of the asteroid Ryugu.

The European Space Agency (ESA)’s Rosetta – Orbited the comet 67P/Churyumov-Gerasimenko and dispatched a lander to its surface.

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10 Things: Mysterious 'Oumuamua

The interstellar object 'Oumuamua perplexed scientists in October 2017 as it whipped past Earth at an unusually high speed. This mysterious visitor is the first object ever seen in our solar system that is known to have originated elsewhere.  Here are five things we know and five things we don’t know about the first confirmed interstellar object to pass through our solar system.

1. We know it’s not from around here.

 The object known as 1I/2017 U1 (and nicknamed ‘Oumuamua) was traveling too fast (196,000 mph, that’s 54 miles per second or 87.3 kilometers per second) to have originated in our solar system. Comets and asteroids from within our solar system move at a slower speed, typically an average of 12 miles per second (19 kilometers per second) . In non-technical terms, 'Oumuamua is an “interstellar vagabond.”

Artist impression of the interstellar object ‘Oumuamua. Credit: ESA/Hubble, NASA, ESO, M. Kornmesser

2. We’re not sure where it came from.

'Oumuamua entered our solar system from the rough direction of the constellation Lyra, but it’s impossible to tell where it originally came from. Thousands of years ago, when 'Oumuamua started to wander from its parent planetary system, the stars were in a different position so it’s impossible to pinpoint its point of origin. It could have been wandering the galaxy for billions of years.

3. We know it’s out of here.

'Oumuamua is headed back out of our solar system and won’t be coming back. It’s rapidly headed in the direction of the constellation Pegasus and will cross the orbit of Neptune in about four years and cover one light year’s distance in about 11,000 years.

4. We don’t really know what it looks like.

We’ve only seen it as a speck of light through a telescope (it is far away and less than half a mile in length), but its unique rotation leads us to believe that it’s elongated like a cigar, about 10 times longer than it is wide. We can’t see it anymore. Artist’s concepts are the best guesses at what it might look like.

5. We know it got a little speed boost.

A rapid response observing campaign allowed us to watch as 'Oumuamua got an unexpected boost in speed. The acceleration slightly changed its course from earlier predictions.

“This additional subtle force on ′Oumuamua likely is caused by jets of gaseous material expelled from its surface,” said Davide Farnocchia of the Center for Near Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory. “This same kind of outgassing affects the motion of many comets in our solar system.”

6. We know it’s tumbling.

Unusual variations in the comet’s brightness suggest it is rotating on more than one axis.

This illustration shows ‘Oumuamua racing toward the outskirts of our solar system. As the complex rotation of the object makes it difficult to determine the exact shape, there are many models of what it could look like. Credits: NASA/ESA/STScI

7. We don’t know what it’s made of.

Comets in our solar system kick off lots of dust and gas when they get close to the Sun, but 'Oumuamua did not, which led observers to consider defining it as an asteroid.

Karen Meech, an astronomer at the University of Hawaii’s Institute of Astronomy, said small dust grains, present on the surface of most comets, may have eroded away during ′Oumuamua's long journey through interstellar space. "The more we study ′Oumuamua, the more exciting it gets." she said. It could be giving off gases that are harder to see than dust, but it’s impossible to know at this point.

8. We knew to expect it.

Just not when. The discovery of an interstellar object has been anticipated for decades. The space between the stars probably has billions and billions of asteroids and comets roaming around independently. Scientists understood that inevitably, some of these small bodies would enter our own solar system. This interstellar visit by ‘Oumuamua reinforces our models of how planetary systems form.

9. We don’t know what it’s doing now.

After January 2018, 'Oumuamua was no longer visible to telescopes, even in space. But scientists continue to analyze the data gathered during the international observing campaign and crack open more mysteries about this unique interstellar visitor.

10. We know there’s a good chance we’ll see another one...eventually.

Because ′Oumuamua is the first interstellar object ever observed in our solar system, researchers caution that it’s difficult to draw general conclusions about this newly-discovered class of celestial bodies. Observations point to the possibility that other star systems regularly eject small comet-like objects and there should be more of them drifting among the stars. Future ground- and space-based surveys could detect more of these interstellar vagabonds, providing a larger sample for scientists to analyze. Adds, Karen Meech, an astronomer at the University of Hawaii’s Institute of Astronomy: “I can hardly wait for the next interstellar object!"

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