Using observations from NASA’s Hubble Space Telescope and ground-based observatories, an international team of scientists confirmed ′Oumuamua (oh-MOO-ah-MOO-ah), the first known interstellar object to travel through our solar system, got an unexpected shift in trajectory as it passed through the inner solar system last year. Our team is ready to answer your questions today, June 28, 2018, from 4-6 p.m. ET (1-3 p.m. PT, 2000-2200 UTC). Experts will sign their responses.

Update 6:21 p.m. ET: That's all the time we have for today. Back to watching the skies. Thanks for all the questions!

June 27 news:

What we know (and what we don't) about 'Oumuamua:


  • Marco Micheli, astronomer, lead author, ESA Space Situational Awareness Near-Earth Object Coordination Centre
  • Marc Buie, co-author, institute scientist, Southwest Research Institute
  • Davide Farnocchia, co-author, asteroid and comet scientist, NASA Jet Propulsion Laboratory
  • Karen Meech, co-author, astronomer and graduate chair, Institute for Astronomy
  • Kelly Fast, Near-Earth Object Observations Program Manager, NASA Headquarteres
  • Paul Chodas, co-author, manager, Center for Near-Earth Object Studies, NASA JPL

Social media & communications support

  • Ryan A Bell, NASA JPL
  • Brittany Brown, NASA HQ
  • Calla Cofield, NASA JPL
  • Kaitlyn Soares, NASA JPL
  • Stephanie L. Smith, NASA JPL

Comments: 287 • Responses: 72  • Date: 

negatxve28 karma

What are your theories regarding the composition of the object? If there has not been any dust/gas detected, can its material not be deduced by any light that boucnes off of it?

NASAJPL29 karma

We believe that this likely has a composition much like comets in our solar system - largely made of dust and ice, where the most abundant ices are likely water carbon monoxide and carbon dioxide. While we didn't detect dust or gas, this is a very small object - at least 1000 times less massive than a normal comet, so it would not take much gas to push it, and it would be very hard to detect. With the amount of gas we think had to be coming off the surface, we should have seen light reflected from small dust that we usually see on comets if it were there. So, we believe that probably the dust was eroded from the surface during its passage through interstellar space. - Karen

FoxClass20 karma

This object is apparently needle-like in shape which seems to me like an uncommon geometry for an interstellar object to have. Is this actually atypical of objects we've seen in our own solar system? And what kind of event would form an object like that?

NASAJPL26 karma

This is an unusual shape - we only have a handful of objects in our solar system that have axis ratios longer than about 5:1, so we don't quite understand how something this long forms. Some speculate that this might have something to do with its violent ejection from its home solar system. However, when things collide they tend to break up and would not have such a long axis ratio. There have been some interesting speculative ideas discussed in the community about this (planets getting ripped apart by tidal forces as it formed close to a much denser star than our Sun, or planets getting ripped apart in a supernova explosion), and we are all interested to see some papers come out. However, keep in mind, HOW we interpret the shape from the brightness variations depends on how the object is spinning. We now know that it isn't rotating in a simple way, but wobbling like a top. This excited and energetic rotation may be the result of its ejection from the home system. It is possible that the shape interpretation could be more of a flattened oval. There are some folks who can do this modeling, but it is likely to take several months. - Karen

Ryanh198519 karma

Is there any truth to the claim that NASA originally thought this was an interstellar spacecraft?

NASAJPL31 karma

No, NASA never thought it was an interstellar spacecraft. NASA's Near-Earth Object (NEO) Observations Program supports ground-based telescopes that survey the skies searching for asteroids (and comets) that come into Earth's neighborhood, as part of NASA's planetary defense efforts. The University of Hawai'i's Pan-STARRS 1 telescope discovered it during routine NEO survey operations. It had been theorized that such objects pass through our Solar System, so it was not unexpected to finally catch one passing through, but it was very exciting that it finally happened! ---Kelly

TehVulpez18 karma

How long must it have been traveling? How is it still in that strange shape?

NASAJPL28 karma

We don't know which star system this originated in, so we don't know how long ago it formed. It could have been traveling through interstellar space for tens or hundreds of billions of years. It might be older than our own solar system. We presume that it has had this shape since it was formed. -Paul

472649472928 karma

Isn't the universe about 14 billion years old?

NASAJPL27 karma

You're right, of course. I should have just said this object could be older than our solar system. -Paul

FlamingTacoShop16 karma

How many slices of bread could fit inside it? Does it matter if it's wheat or white?

NASAJPL56 karma

OK, this is the part where Reddit has a field day with the journalist-turned-social-media-manager doin' some math. <cracks knuckles> Here we go.

Due to the light curve, we believe that 'Oumuamua is highly elongated in shape, but if it WAS a sphere, the team estimates an average radius of 104m.

If we assume the object has a spherical volume of:

Vo = 4/3πr^3

Vo = (4/3) * (3.14159) * (104m)^3

Vo = (1.33333) * (3.14159) * (1124864 m^3)

Vo = 4711815.32 m^3

Assuming a slice of bread is 4.5 inches on each side by 0.5 inches thick...

Vs = 0.1143m * 0.1143m * 0.0127m

Vs = 0.00016591902 m^3

That would give 'Oumuamua room to hold...

Vo/Vs = 4711815.32m^3 / 0.00016591902 m^3

about 28 billion slices of bread.

White or wheat, doesn't matter. If we were talking density, though... cheap white bread vs. a nice dark pumpernickel? Well, I'll leave that math to another Redditor.



WickedSushi15 karma

Here is a questions for every individual member. What are some of your favorite space movies?

NASAJPL36 karma

The Martian -- Paul, Karen

Space:1999 -- Kelly

Interstellar -- Kaitlyn

Alien -- Ryan

Contact -- Calla, Marco

Star Trek II: The Wrath of Khaaaaaaaaaaaan -- Stephanie

My job is like living in a space movie! -- Davide

antidamage6 karma

Space 1999 gave me horrific nightmares as a kid. There was that one episode with the room-sized blob of alien flesh with an eye and tentacles.

NASAJPL9 karma

Me too!!! I still see the "dragon's" eye every time I'm in a swimming pool at night and the pool light is on, if you know what I mean! I still loved the Moonbase Alpha sets, the Eagles, the space scenes, and the music of the first season.

DeltahJuliet13 karma

Does NASA have any plans to take advantage of this opportunity in the future? Like intercepting and study? Wouldn't moon basses with the capability to quickly launch probes and drones be the next frontier? I think Mars is important, as is everything in space. But the moon is just waiting to be the first international space hub.

NASAJPL19 karma

NASA currently has a fantastic asteroid interception mission underway. OSIRIS-REx will reach the asteroid Bennu later this summer, and after studying Bennu with its instruments, it will collect a sample and return it to Earth for study. You can read more about it here: And we all have been marveling at JAXA's Hayabusa2 mission that has reached the asteroid Ryugu and returned incredible images of the surface just in the past week as part of its sample return mission. -Kelly

BSamuelC11 karma

Is this the first time you have seen anything quite like this? do you think it's common for this to happen?

NASAJPL22 karma

Part of what made this so exciting is that this is the very first observation of an interstellar object - something coming from outside our solar system. They had long been expected to exist. Why now? These move fast relative to the Earth and are quite faint, so you need a large telescope that can see faint things that is scanning a large fraction of the sky quickly. Until recently we didn't have this type of survey. When we thought that this was asteroidal (no outgassing), this discovery suggested that at any one moment there might be one object like this in the inner solar system. Now that this is known to be a comet, the models predict fewer (by maybe a factor of 100), but that still means with dedicated surveys we should start seeing more. This is especially true now that the Pan-STARRS2 telescope starting to survey in Hawaii and in the near future (2022) the LSST 8-m telescope will begin a survey in the southern hemisphere. - Karen

ben31415 karma

Why does the fact that this is a comet rather than an asteroid change the guessed density of interstellar objects based on this observation?

NASAJPL10 karma

Comet densities have been measured by spacecraft (and estimated from the ground) and they are low - around 500 kg/cubic meter (about half the density of water ice). Rocky asteroids, on the other hand, have typical densities around 3500 kg/cubic meter. We can estimate the volume based on the shape, and thus the overall mass will change depending on the density. Our comet models don't work with asteroid densities because there couldn't be enough gas coming off to push a much more massive object. - Karen

metalburning11 karma

What caused the shift in speed?

NASAJPL26 karma

Outgassing from vents on the surface of the object. It's a very small force, but our data was so precise that we could detect it. We think there are lots of frozen gases under the surface of this object, and when it got close to the Sun the surface heated up and those gasses sublimated and erupted through the surface, probably through vents. The Rosetta spacecraft actually imaged this sort of venting on comet 69P/CG. The outgassing occurs mostly on the daytime side of the object, because the daytime side is hotter. That's why outgassing generally pushes objects away from the Sun. That's what we say with `Oumuamua. -Paul

NASAJPL12 karma

Correction: Rosetta was at comet 67P/Churyumov-Gerasimenko, not 69P

Salamander764511 karma

Hypothetically, what is the most exciting conclusion we could draw from studying Oumuamua if we were to rendezvous with it?

NASAJPL13 karma

Ask 1000 scientists and you'll get 1000 answers on this. I would like to measure a sample to see how long it's been drifting in space. This is easy to do if you had a piece and had the right tools from Earth. Is it 1 billion years old? Is it 10 billion? Mostly I want to know if it's older than our solar system or not and then see what else we could learn. --Marc

Glitterytea11 karma

What's the chances of a comet wiping out life on earth in the next 50 years?

NASAJPL15 karma

That is an extremely unlikely event. To give some perspective, asteroids of 1 km or larger reach the Earth on timescales of millions of years. Comet impacts are much less frequent than that, about once every few hundred million years. --Davide

bbreslau9 karma

How did you first observe the object and when did you realise its significance?

NASAJPL11 karma

The object was first observed in October 2017, by the Pan-STARRS telescope in Hawaii.

We started realizing that it was the first interstellar object ever discovered within about a day, when the Pan-STARRS data was combined with observations taken with other telescopes, including ESA's OGS telescope in the Canary Islands.

- Marco

PaperTronics7 karma

What's the internet speed there at NASA? Is it really 92 terabytes or is that just a myth?

NASAJPL9 karma

I can't speak for the whole agency, but for me right now via this conference room WiFi, it's about 50 MB/s (both up and down). That's a luxurious rate compared to what our spacecraft experience via the Deep Space Network when receiving commands or downlinking data. More on that comms system here:

-- Stephanie

markmd46 karma

Could it be that this object is not elongated but just have a side very reflective and another not so?

NASAJPL9 karma

This is a great suggestion, but no. The specific shape of the brightness variations is different if it is due to shape versus due to differing reflectivity (which we call albedo) from one side to another. A lightcurve caused by albedo variations tends to have a more sinusoidal shape (even minima and maxima). A lightcurve caused by shape tends to have rounded tops and pointed bottoms. - Karen

markmd45 karma

Could somebody make spectral analysis to tell it's composition?

NASAJPL14 karma

Several teams tried to do this. It is much harder to do spectroscopy on faint objects because the different wavelengths of light is being spread out out over the detector elements - so you need a much bigger telescope. So the teams that did do spectroscopy found it very challenging and the data was very noisy. Other teams, such as ours, used broad colored filters to get at the composition - and because these collect light over a range of wavelengths the signal is stronger. Both techniques told us that this object is "red". What we mean by this is that it reflects light more efficiently at the red end of the spectrum compared to the blue end. This is very similar to what we see for comets such as 67P/Churyumov-Gerasimenko recently visited by the Rosetta spacecraft. The "red" reflectivity in that case is due to an organic rich surface. However, not all materials that reflect in the red have the same composition. For example, certain minerals that contain iron also reflect light this way - such as the dark side of Saturn's moon, Iapetus. So unfortunately we didn't get much direct information on composition. What is really exciting for me from this new paper is that we do get a hint at composition that is different from comets in our solar system. Our models show that the amount of gas that 'Oumuamua had to give off to give it the acceleration we observed should have produced some light we could detect from a common minor species seen in comets: cyanide (CN). Because we didn't see it here, we believe that `Oumuamua may be depleted in cyanide. This is exciting because it tells us that the solar system it came from my have a different chemistry. This is important when considering how planets get the necessary building blocks for life. - Karen

lanephil5 karma

It sounds like the object's final (far away/intersetllar) departure velocity (relative to the sun) is increased in comparison to it's initial (far away/interstellar) approach velocity. By how much? millimeters per second? meters per second? more?

NASAJPL3 karma

Because of the detected non-gravitational acceleration, 'Oumuamua is not slowing down as it would under the action of gravitational forces alone. Over the time we observed 'Oumuamua (Ocober 2017 to January 2018) this non-gravitational acceleration changed the velocity by about 10 m/s. -- Davide

Jakisuaki4 karma

So, before you had all the details, did any of you hope it was a space ship due to its elongated shape and interstellar origin?

I mean, I sure as hell did.

NASAJPL4 karma

Speaking for myself, I did think of that after reading Arthur C. Clarke's Rendezvous with Rama, it's hard not to. But then we had to ask ourselves what is the most likely explanation for this object, and our analyses of the non-gravitational accelerations were pretty convincing that it's a natural object. -Paul

NASAJPL4 karma

I think many of us right after the first discovery pondered "what if" and were excited .... but as scientists we had to go through the careful route of examining all possible explanations - and everything was consistent with a natural object. - Karen

WallaceAtticus4 karma

What do you think is causing it to go so fast? Is it more than just off-gassing?

NASAJPL12 karma

When traveling in interstellar space, 'Oumuamua had a velocity of about 26 km/s relative to the Solar System. That is a typical relative velocity for interstellar objects. Once 'Oumuamua entered the Solar System, the gravity of the Sun did most of the work by accelerating 'Oumuamua until it came closest to the Sun on September 9, 2017. At that point 'Oumuamua was moving at almost 90 km/s. Now 'Oumuamua is on its way out of the Solar System, slowing down until it will exit the Solar System with a velocity of (again) 26 km/s. Outgassing only had a small effect on the 'Oumuamua trajectory. -- Davide

keigo1990134 karma

When Oumuamua was first noticed, it was moving extremely fast. What plausible explanation could there be for the speed of such an object?

NASAJPL6 karma

It is due to a combination of the initial velocity 'Oumuamua had relative to the Sun before entering the Solar System (about 26 km/s) and the gravitational pull of the Sun (and the planets) that accelerated it to a peak of almost 90 km/s when it came closest to the Sun on September 9, 2017. -- Davide

dude-O-rama4 karma


NASAJPL12 karma

It's a hyperbolic comet, therefore it doesn't have an orbital period, since it's not in a periodic orbit around the Sun.

- Marco

dude-O-rama3 karma


NASAJPL6 karma

It's already too faint to see unfortunately, even with the most powerful telescopes we have, like the Hubble Space Telescope.

- Marco

safarl_osrs3 karma

It also rotates on two axes, and it switches between them every 7.3 hours.

NASAJPL4 karma

Yes, that's true, it's rotating on two axes, and both at the same time with slightly different periods. It's a quite complex spinning motion!

- Marco

Cajoled4 karma

What is the earliest that we could theoretically detect such an object with existing telescopes? Would it be possible to detect one long enough in advance to schedule a mission (even if the mission would be a crash landing)?

NASAJPL5 karma

We last saw Oumuamua in early January with the Hubble Space Telescope. If we knew exactly where to look on its way in we might have seen it in June. It just wasn't visible very long no matter what we used because it's really small. --Marc

Guppypuppy694 karma

Here is a question for all of you, what is your favorite science fiction novel?

NASAJPL7 karma

Dune - Karen

Various novels from Asimov and Clarke - Marco

jedijesus7433 karma

I have been to JPL a few times on tours and the open house day you guys have. If I come on a tour again, how do I get to say hello to the people running this? Awesome job by the way!

NASAJPL7 karma

Cool! We're usually out and about on lab. Tweet @nasajpl when you visit and if we're around, we'll say hi :)

Here's info on our free public tours:

- Kaitlyn

icedankquote3 karma

What temperatures did Oumuamua experience at the closest distance to the sun and might such estimation give you an idea of the composition?

NASAJPL8 karma

'Oumuamua passed inside the orbit of Mercury on September 9, 2017, and the surface temperatures likely got hotter than 600 Kelvin (620 F). Comets in our solar system are actually remarkably good insulators. This is because their density is low (they are very porous - up to 70-80% porosity - meaning the amount of empty relative to full space) - and so it is hard for the heat to get transported. This means that ice can exist beneath the surface. Water ice will convert from a solid to a gas (called sublimation) peaking at about 373 Kelvin (but starting at lower temperatures). We did a model of the transport of heat into the interior in our work to match the amount of outgassing that we needed to push the comet and change the orbit. - Karen

47264947293 karma

Is there any way Oumuama could be intercepted by a probe, or is it too fast?

NASAJPL7 karma

Technologically this is possible -- but would be an enormously expensive high risk mission. This isn't the one to explore. We hope to discover more in the future - and if we could see them on their way in while far from the Sun, and if we had a spacecraft ready to send, then this would be a good mission to think about. - Karen

AngusF23 karma

How fast was it travelling when it passed it's closest point to the sun, and how fast is it going now? What is it's rate of acceleration? Thanks.

NASAJPL4 karma

The velocity of 'Oumuamua when it passed closest to the Sun was almost 90 km/s. Now it's going away from the Sun at about 30 km/s. It is progressively slowing down but will still leave the Solar System with a velocity of about 26 km/s. -- Davide

JamesSway3 karma

Could Oumuamua be part of a larger pack of comets coming from this same direction? A smaller one out front, being NEO discovered it, what are the odds this is a destroyed planet with a large amount of debris that should be following behind?

NASAJPL3 karma

Each solar system may eject a lot of comets when it is first forming, but they spread out in random directions, and there's really no way that the ejected comets can group themselves into "packs". In interstellar space, the density of these objects should be of fairly uniform. -Paul

lemurski3 karma

Follow up question:

If those frozen gases you talked about were to keep realeasing due to heat would it be possible for Oumuamua to change its trajectory so much it would stay in our solar system which could potentially let you study it even more?

NASAJPL4 karma

No, 'Oumuamua will leave are Solar System. The non-gravitational acceleration we detected is small, about a thousand times smaller than that due to the gravity of the Sun, and so the path of 'Oumuamua remains pretty much the same. Moreover, this non-gravitational acceleration is not helping, it is actually slightly pushing 'Oumuamua away. -- Davide

Necc_Gringo3 karma

How do you know its interstellar, and not a product of the Kuiper belt?

NASAJPL9 karma

If it had originated from the Kuiper belt 'Oumuamua could not go as fast it does. Its path is hyperbolic and so 'Oumuamua must have originated somewhere else. -- Davide

huslage3 karma

Why does the orbit look so much like a gravity assist transfer orbit like one of our probes use?

NASAJPL6 karma

Orbits take the basic shape of conic sections because of the Newton's Law of Gravity. They can be circular, elliptical, parabolic, or hyperbolic. Comets, asteroids and planets within our solar system follow elliptical orbits about the Sun. `Oumuamua follows a hyperbolic orbit, which is why we know it came from outside the solar system. Gravity assist trajectories that go really close to planets are basically hyperbolic trajectories relative to the planet, so they have the same basic shape. -Paul

ThanosPapa3 karma

Hello from Greece!!! As far as I understand this object travel too fast in order to be affected by sun's or other planet's gravity in our solar system. At the same time we just recently exit our solar system for the very first time (pls correct me if I am wrong). So my question is...Do you believe that one day we may able to spot this kind of objects early enough in order to somehow land equioment on them and afterwards monitor what is going on outside our solar system? Something like constantly moving sounds cost effective and a potential source of numerous valuable data :-)

NASAJPL3 karma

No, this object was affected a lot. The Sun's gravity accelerated it from its original speed of 26.4 km/s to 87.2 km/s when nearest the Sun, to 31.3 km/s today, and then back to 26.4 km/s after it has left our solar system. Relative to the Sun, the object changed direction by 113 degrees (that's called the turning angle of a hyperbolic trajectory). Interstellar objects move very fast. To send a mission to land on one of these, a spacecraft has to match the object's speed, which is really hard to do. But if we detected one of these objects early enough, and we had a spacecraft more or less ready to launch, it would be technically feasible to land on one of these. There are currently no plans to prepare such a mission, but it would be feasible. -Paul

Astro_Neel3 karma

Any updates on how Oumuamua got its peculiar shape? Is it a result of years of interstellar journey or just some sheer random coincidence?

NASAJPL6 karma

We really don't know and this is still one of the major areas of uncertainty for this object. Speculation ranges from this being planetary material that was forming very close to a star much denser than our own that got ripped apart from the star's tidal forces, and others speculate that it could be shredded planetary material torn apart during the death throes of a star - during a supernova event. I've heard even more exotic explanations. It will be interesting to see if more theories come out. The next analysis, however, should be to do a detailed model of the complex excited rotation (wobbling motion) and get a precise shape model - but this will take several months I think. Right now it had several possible shape interpreations - long and narrow, or more of a flattened oval. - Karen

TStrother3 karma

For years the notion of lithopanspermia has been ridiculed by astrophysicists as beyond unlikely. Do you think ‘Oumuamua’s pass through our solar system will change any minds about this?

NASAJPL5 karma

There are a few aspects to consider: (1) whether material from another star system can make it to our solar system and (2) whether this could be a means of transporting life and (3) did this occur. Scientists have realized for decades that #1 was possible. The existence of `Oumuamua is the first object that we have seen from another star system. For #2 I think we have seen especially from the NASA LDEF experiment (Long duration exposure facility) - that life *can* exist for a long time in space. This experiment, launched in 1984, was supposed to be up in space for a short period to study the effects of the radiation environment on materials and biology. With the space shuttle Challenger disaster in Jan. 1986, there was no way to bring the experiment back until 1990. So scientists thought that the biology experiments would be ruined. To their surprise, it was found that a species of bacteria called an "extremophile" - Deinococcus radiodurans survived! So it is possible to transport material. So that really leaves us with #3 - and there is really no way of knowing. - Karen

markmd43 karma

Was it a person who discovered it or was it an automatic system (program)?

NASAJPL3 karma

The object was first detected by an automatic system, which identified the moving object in images just acquired by the Pan-STARRS telescope, and flagged it as potentially interesting.

It was then reviewed by a person, who confirmed it was real and interesting.

- Marco

Sitonthemelon3 karma

How was the name ‘Oumuamua’ chosen?

NASAJPL18 karma

Initially the object received an internal Pan-STARRS1 survey designation (which was hard to type in the flurry of emails among the team), and then it received the official Minor Planet Center Designation of A/2017 U1 -- not much easier to type. Internally, we briefly tossed around "Rama" after Arthur C. Clark's famous 1973 science fiction story (very easy to type - grin). However, this wasn't right either. Because of the importance of this being the first discovery of an interstellar object and it was made in Hawaii, we decided to contact some local experts on Hawaiian culture - a Hawaiian Navigator, Ka'iu Kimura, and a Hawaian linguist, Larry Kimura. We asked them to propose a name. They suggested 'Oumuamua: "This object is somewhat of a "scout" or "messenger" sent from our distant past/beginnings to "check out" or build connections with us.  ʻou - reach out for; muamua - reduplication of "mua" placing emphasis on the meaning  first, in advance of". - Karen

toyoyome3 karma

I realize that the probability of the object having originated from a star system conducive to supporting life is extremely low, but it looks to me that this would be a very good opportunity to look for evidence of life in distant systems at a close range. Has there been an attempt to find out if the object has any traces of biological / organic matter on it to test this?

NASAJPL8 karma

No. This would be a very exciting experiment, but this object was just too faint to get much at all on the composition. We had only about one week to characterize it before it became really too faint. We are now anxiously waiting for the next one - hoping we have more time to study it! I responded to the question from 'amrok' about spectroscopy (check it out) -- so I think we got a glimpse that the solar system that `Oumuamua came from may have had a different chemistry - and this is important for astrobiology - Karen

toyoyome1 karma

Thanks for the answer! It would be very exciting indeed if we were able to get samples of extrastellar (is that a word?) matter to study! Hope it happens in our time!

NASAJPL2 karma

Me too but I think this is a very long way off! Even doing a flyby would be a challenge. I think we would need to have a spacecraft ready to launch and discover an object on its way in before we would get a flyby. We could learn a huge amount from that as a first cut. Remember we are just starting to do sample return for asteroids in our solar system! - Karen

zeroephos2 karma

Have y’all been able to get a picture of it to know a rough estimate as to what it looks like and also how did you guys find out that it had entered our system?

NASAJPL3 karma

This object is small, and it never got close enough to the Earth for us to resolve it. So, we *do* have some images - you can look at to see our best image from Gemini (true color). Not very impressive I know! How we found it was using the Pan STARRS1 survey in Hawaii - which scans the skies every night looking for Near Earth Objects - Karen

KMustard2 karma

Do you really say "Oumuamua" every time you refer to this object?

NASAJPL3 karma

Yes, I do - but when typing a lot I often will only say it the first time, then abbreviate it to 1I -- even though I type really fast! - Karen

DeltahJuliet2 karma

Was this the fastest moving asteroid ever recorded? Does its speed suggest anything like a collision, explosion or perhaps alien influence?

NASAJPL4 karma

`Oumuamua is probably the fastest. We do know that comets that come in from our Oort cloud can hit the Sun, and at that point they should be moving at 618 km/sec (=384 miles per sec or over 2 million km/hr or 1.4 million mph). We have observed comets called "sungrazers" - which comes very close to the sun - and they too are going very fast. For some beautiful images you can look at the SOHO observatory "Comet gallery" website:

The speed is nothing "unusual" - Karen

exoplanetaryscience2 karma

The JPL shows Oumuamua to have an extremely ridiculously high nongravitational movement. Do you have any possible explanations for how it could be higher than even objects like Halley's comet without any observations showing any activity whatsoever?

NASAJPL4 karma

This object actually is a mass that is 100,000x less than Halley's comet so it does not take as much gas to push it. When sunlight interacts with gas the gas emits light in different narrow wavelength regions. Spectroscopy is a means to detect the light at a bunch of different wavelengths. Images taken through a broad filter collect light over a wide range of wavelengths, and then it would not be possible to distinguish emission from gas over a narrow region. However, for faint objects you need a very large telescope to get a good spectrum because now we are spreading out the light over narrow wavelength regions and so there is not as much signal in each. So, may teams tried to get spectra, but they were noisy. Nothing was detected in terms of gas but for such a small object this was perhaps not too surprising. The most common ices we see in comets are water, carbon dioxide and carbon monoxide. However, those aren't the molecules we usually see first in comets, even when there is quite a bit of gas, because they don't emit light at visible wavelengths where we have the most sensitive detectors. A minor gas that gets dragged out with water is CN (cyanide; typically present at < 1% the abundance of water). It emits light very strongly in the blue and is usually the first gas we see in all comets. Because this object was faint, teams looked for CN in the visible (blue) region. They saw nothing and got upper limits to the amount that could be there and not be seen. The amount of gas we calculate has to be coming off `Oumuamua to give it the acceleration we see is so much that if it had the same chemistry as our solar system's comets would predict that the amount of CN should have been seen. If `Oumuamua's amount of CN relative to water were depleted by at least a factor of 15, then the amount would be lower than the reported limits for detection that were published.

Another less direct way to infer that there is gas is to search for dust. Dust is easier to detect because we are looking for reflected sunlight from the surface of the dust grains at all wavelengths using images - so this is much more sensitive. Typical comets have a wide range of dust sizes from micron sized (about the size of particles in cigarette smoke) up to quite large (10's of cm). Because comets are not particularly large, the gravity is very weak, and the dust is lifted off the surface as the gas flows away. As the dust grains get larger it takes a lot more gas coming off to push them away. In our solar system when the comets are just barely warm enough to have the gas starting to flow, the only dust that can be lifted off is tiny. Dust in the solar system follows a rule for sizes that we see when things collide: a lot of small material is produced, and only very few larger pieces. Only when comets get close enough to the sun that there is a lot of fast moving gas do the really big particles come off. 'Oumuamua was close to the sun and had enough gas coming off to cause the non-gravitational motion, and if the surface had the typical sizes of comet dust there should have been a lot of small dust coming off that we would have seen. We looked closely and didn't see small dust. Because it takes more gas to lift the big dust from the surface if 'Oumuamua were simply lacking in small dust, then we could have the right amount of gas coming off, but not see the smaller number of bigger dust grains. Some scientists have reported that comets in interstellar space could preferentially lose small dust as they interact with the gas and dust in interstellar space

Pozpenguin2 karma

Are there any theorized systems of origin for this object? What kind of distance could it cover over what sort of timescales?

NASAJPL6 karma

We haven't been able to track back 'Oumuamua to its system of origin yet. But using the data we collected for this paper we'll give it try!

While traveling in interstellar space, 'Oumuamua covers one lightyear in about 11 thousand years.

-- Davide

isthewalrus1 karma


NASAJPL4 karma


James Webb will probably not be used to discover new interstellar objects, but it will be very useful to better learn their properties.

Other telescopes dedicated to surveying the sky are better for discovering new ones. For example Pan-STARRS, the project that discovered this one, is soon going to have a second operational telescope, improving their discovery capabilities. And, in the near future, there will be a much larger survey telescope called LSST, which is currently being built in Chile.

- Marco

NotDeadlyRadiation1 karma

What would we need in terms of technology and data itself to have a rough estimate on where did this object originate? Is it possible?

Thank you for doing this AMA!

NASAJPL2 karma

Actually, this was the purpose of our Hubble Space Telescope observing program. Because it can see fainter objects than the ground based telescopes, we planned to observe with Hubble in November, December and early January to extend the position measurements out to 2.5 months. We hoped from this to get an accurate enough trajectory to trace back to its home solar system. However, this new paper and the discovery of the non-gravitational motion makes that task much harder. Now we have another component that adds another source of uncertainty to the orbit. - Karen

Elfing_Rihno1 karma

what is the approx mass of the object ?

NASAJPL2 karma

We estimate approximately a billion kg - or about 1000 times less massive than typical comets, or 100,000 times less massive than Halley's comet. - Karen

lanephil1 karma

Any data (or educated guesses) for the mass of Oumuamua? How about for the total mass offgassed during Solar System transit? If not kilogram numbers, perhaps a ratio?

lanephil1 karma

(I understand from Karen a mass estimate for the object of a billion kilograms. Thanks! How about the models for outgassing; any mass estimates?)

NASAJPL1 karma

For our models we used the 1 billion kg estimate and then assumed typical ice/dust ratios and typical comet composition with respect to ices and then calculated the outgassing trying to match the approximate 10 kg/sec that was needed to give it the observed push. The outgassing will be the strongest when closest to the sun, then drops off roughly as 1/distance-squared. So to get the total mass lost one has to add all this up. We'd have to run models to get you a proper number - but if we assume (incorrectly) that it was 10 kg/sec for the whole time it was inside 1 au from the sun (inside the Earth's orbit) when it was warmest - then this would be less than a few percent of its mass. So - probably a lot less than this. - Karen

ugottafriend1 karma

Would you be able to make an educated guess as to what it's made of, or are the possibilities too variable?

NASAJPL3 karma

I think it is very much like a comet - in other words, ices (water, carbon monoxide and carbon dioxide) and dust. The ices I list are the most abundant ones that freeze out in a cloud in deep space and are likely abundant in a young solar system as it is forming. Comets in our solar system also have a bunch of minor species, organic compounds and other chemicals. We see these in interstellar gas clouds in space - so the starting ingredients should be the same everywhere. The proportions may be quite different in different solar systems depending on on what the physical processes are. The dust composition is likely silicates and organics. - Karen

Dombuldore1 karma

How fast is the object going? Now that the object has changed its trajectory, to which star system is it now headed (if it's heading to one)

NASAJPL1 karma

`Omuamua is travelling about 70,000 mph today, as it moves away from the Sun. The Sun's gravity is still affecting it, slowing it down, and it will end up travelling at about 59,000 mph through interstellar space, relative to our solar system that is. It is headed generally towards the constellation Pegasus, but it will likely be millions of years before it gets near any star system, and since we don't know the trajectories of those star systems very accurately, it's difficult to really predict which of them it will approach first. -Paul

Argel751 karma

Given the odd shape of the object in the uneventful (never) impact with earth would it matter if the object impacts on a dive position vs on its flat side?

NASAJPL1 karma

The impact energy would be the same. -- Davide

clovencarrot1 karma

What's the current theory about how this object's orbit/momentum originated?

NASAJPL2 karma

We think this object originated in another star system, the same way comets and asteroids formed in our own solar system. And then it was thrown out of that star system by a close encounter with a large planet in that system. We think that billions of comets and asteroids were similarly ejected by Jupiter when our own solar system was young. Since it was cast out from its solar system, `Oumuamua has been travelling through interstellar space, and basically just ran across our solar system. -Paul

lemurski1 karma

Do you have any studies you want to conduct or other things you would like to do before Oumuamua leaves us forever?

NASAJPL1 karma

Well, sadly, we can collect no additional data at this point - it is too faint. However, there is still data we can look at. We still want to look at the trajectory and try to trace the path backwards to see where the home system is. - Karen

mychagrin1 karma

Did NASA change the classification from Asteroid to Comet based on the detection of non-gravitational acceleration and the most likely explanation of outgassing? Could this be confirmation bias?

NASAJPL2 karma

After the images that showed there was no activity we were very surprised to see the non-gravitational motion - i.e. this was against our bias! - Karen

BerserkonXBL1 karma

Any idea what caused this object to form it's cigar shape? Perhaps hot and fast ejecta from a large scale impact in a distant star system, hot enough to be decently viscous and stretch the object to it's current shape?

NASAJPL2 karma

We really don't know. There are lots of creative ideas out there - and this is as good a hypothesis as I've seen from many scientists. I think this is one that will take a lot more thought. - Karen

Elfing_Rihno1 karma

is the increase in speed due to gases the same as we had seen on enceledus?

NASAJPL2 karma

It's a little bit of a similar effect, but Enceladus is huge and the outgassing is too small to affect its motion. Also, the jets coming out of Enceladus are not due to solar heating as they are on `Oumuamua. Finally, the jets on Enceladus originate from a subsurface ocean, and we don't have that on `Oumuamua. -Paul

markmd41 karma

Often things don't came alone, can a shower of asteroids came after it marking a new era of bombardment of the solar system and end of life on earth?

NASAJPL1 karma

There is nothing we know that could cause a "shower" of interstellar objects. We do expected to detect more of these, since asteroid surveys are increasingly more capable of finding asteroids and comets, but we think the actual number of interstellar objects passing through our solar system is constant over time. -Paul

Youngheezy1821 karma

in what way does this object benefit us scientifically? do you guys have any guesses as to how it was formed?

NASAJPL2 karma

To me I'm really excited that this recent result gives us a hint that the chemistry of this comet is different from those in another solar system. Understanding the chemical and physical processes occurring when a solar system forms is important for understanding how habitable solar systems form. This has huge implications for astrobiology because life requires specific elements. I can hardly wait to study the next one! - Karen

BerserkonXBL1 karma

Karen, would you recommend UH for someone looking to do a PhD in planetary science? It is one of the many grad schools I was thinking of applying to and I haven't really heard much from people who went there.


NASAJPL2 karma

Absolutely! And, as the new Grad chair I can say that with authority! I think it is a great place to come, and you get unparalleled access to telescope time on Maunakea. We have instrumentation programs as well as observing programs. I am at the Institute for Astronomy (more astronomy focused) and there is a group on campus that focuses more on planetary geosciences. So we have a large variety of options. Check out our webpages: - Karen

esotericist1 karma

Will we be able to see this object clearly anytime assuming we get some of the giant, parallax, or space telescopes up and running as they're scheduled?

NASAJPL3 karma

Right now 'Oumuamua is really too faint to see. The very last observations were made by Hubble Space Telescope (HST) on January 2, 2018. We had an allocation of 5 HST orbits in January but only saw it in two - near a magnitude of 27.5. Magnitudes are a logarithmic brightness system used by astronomers - every 5 magnitudes is a factor of 100 in brightness. The faintest the human eye can see at a dark site is about mag 6. Right now, it is about 600 million miles from Earth and its average brightness is about a factor of 15 too faint for HST to see, and a factor of 5 billion times too faint to see by the naked eye. You can go fainter by combining the light from many telescopes - but at this point its brightness is fainter than 30.5 magnitudes -- so it is not detectable any more. I was on the EPOXI space mission team and when we were trying to find our first comet target (which was lost) we did this experiment -- I combined 8-m and 10-m data from many telescopes and we managed to get down to magnitudes of 28.5. - Karen

Robearsn1 karma

What are the most important learnings thus far from the observation of Oumuamua's passing through our solar system, outside of the knowledge we've gleaned about Oumuamua itself? Thanks, NASA and JPL!

NASAJPL1 karma

To me - the detection of the object is really important. Secondly, I'm really excited from the recent result that we might have gotten a hint that another solar system has a comet with a different chemistry from our solar system comets. - Karen

yes2danny1 karma

Well, I understand what 'Oumuamua' was but is there anything else out there, that we know of is heading towards earth in a similar fashion to that?

hpk72 karma

We can't see 'Oumuamua anymore according to the other comments, so it's unlikely that we'd be able to see anything like it heading towards us.

yes2danny1 karma

I understand we can't see it. I just don't understand how it's unlikely to find others like it.

NASAJPL3 karma

There are telescopes's that survey the skies every night through NASA's Near-Earth Object Observations Program, looking for asteroids (and comets) that pass through Earth's neighborhood, and one of them found 'Oumuamua. It is possible that more of these interstellar objects will eventually be discovered as part of NEO survey operations and other sky survey operations, especially since 'Oumumua showed what to look for and recognize in the data in terms of its motion. And in the future, as new survey telescopes come online, it may be easier to find other interstellar objects if they pass through our solar system. -Kelly

solo967891 karma

I know the answers will vary, but how demanding is it to work at NASA, especially with a case like this? My dream is to work there one day, so what is your experience working there?

NASAJPL3 karma

Great question. It's easy to forget that you're working when you're here. I'm lucky enough to spend my workdays with a group of people that I consider friends. Even though we work super hard we have a good time and look out for one another. This AMA, for instance, has been a great time where we're chatting with the Manager of Center for Near-Earth Object Studies, an astronomer, a scientist, the team that I work on and excited folks like you. I'm getting to learn while working and that's so rad.

I've been here for around seven months now and I feel like I've learned two years worth of college curriculum. We're always hiring somewhere so keep an eye out and follow that dream.

NASA jobs:

NASA/JPL jobs:

- Ryan

horyzon4111 karma

What are our current capabilities against an extinction level emergency such as a comet or asteroid? How soon/far can we predict a trajectory towards earth and do we have the ability to destroy it using earths nuclear missiles?Please Explain ?

NASAJPL1 karma

NASA's Planetary Defense Coordination Office has an FAQ at and just last week NASA participated in the release of the U.S. federal government's multiagency National Near-Earth Object Preparedness Strategy and Action Plan at -Kelly

nebkla1 karma

How often do we think that interstellar objects pass through the solar system, this is the first one we were able to see but could they pass through every 50 years or so?

NASAJPL2 karma

It's hard to draw conclusions based on a single object, it's low number statistics! But the fact that we discovered one after a couple decades of surveying the sky to find asteroids suggests that there should be more interstellar visitors. With new surveys like LSST ( become operational we will have better chances of discovering more. -- Davide

amrok1 karma

What can we get if we point all our telescopes at this object? Will we see anything or something? I know big space telescopes are dedicated and tuned not for objects outside our solar system.

NASAJPL3 karma

Right now 'Oumuamua is really too faint to see. The very last observations were made by Hubble Space Telescope (HST) on January 2, 2018. We had an allocation of 5 HST orbits in January but only saw it in two - near a magnitude of 27.5. Magnitudes are a logarithmic brightness system used by astronomers - every 5 magnitudes is a factor of 100 in brightness. The faintest the human eye can see at a dark site is about mag 6. Right now, it is about 600 million miles from Earth and its average brightness is about a factor of 15 too faint for HST to see, and a factor of 5 billion times too faint to see by the naked eye. You can go fainter by combining the light from many telescopes - but at this point its brightness is fainter than 30.5 magnitudes -- so it is not detectable any more. I was on the EPOXI space mission team and when we were trying to find our first comet target (which was lost) we did this experiment -- I combined 8-m and 10-m data from many telescopes and we managed to get down to magnitudes of 28.5. - Karen

clovencarrot1 karma

Is it possible that this object is in any way related to Planet Nine (Planet X, or whatever else you want to call the idea of a massive dark planet existing in our solar system, undiscovered)?

NASAJPL6 karma

No, we know this object's trajectory really well and we know it came into our solar system with far too much speed to have originated from within our solar system. Planet Nine, f it exists, would be part of our solar system. -Paul