This is another of my articles to help the many people who come to my science blog saying how scared they are of a planet, which they think is hidden behind the sun and is about to fly past or hit Earth in the near future. What I'm going to describe here is beginner level astronomy, but of course many never study astronomy. Most know that the Earth orbits the sun, nowadays, but few stop to think through what this means for the night sky and where planets can appear in it.

So let's draw out some of those implications, and then, if you are one of those who worry about this, I hope you'll see for yourself why astronomers say the idea is just plain nutty. Maybe after reading this, you will be kicking yourself that you got so scared of such a nutty idea. I hope so, anyway.

It is just so sad that people do get scared of these ideas. Even suicidal sometimes. Back in 2012 a school girl in the UK committed suicide and after she died, her parents found out that she'd been obsessively reading all these online conspiracy theory hidden planet web sites. It was all about something that she could have seen to be nutty if she had known just a bit of basic astronomy, which I'm about to explain. I hope this will be like a vaccine to inoculate some of you at least against these ideas.

TL:DR - if there was a planet matching "Nibiru" at the other side of the sun right now, - well wherever it is in the night sky, it has to be in one of the constellations. Last winter, Earth was the other side of the sun - and the constellations currently hidden behind the sun were visible all night, as anyone will know who looks at the night sky regularly.

If you say it was already between us and the sun last winter - then what about previous years on its decade long journey in towards the sun? Ask the Nibiru people what constellation it was in. Whatever they say, it's impossible for it to stay hidden as the constellation is visible all night at some point in the year.

Then, any planet approaching from the South Pole would be somewhere in the region of the sky close to the Southern Cross. This means it would be visible all night, every clear night, from almost the entire southern hemisphere including Australia, Southern Africa, New Zealand, Madagascar, South America etc. If approaching from the North pole likewise it is visible all night, every clear night from anywhere in the Northern hemisphere where you can see Polaris.

There are many other reasons why it is impossible, but this is the easiest way to see it. I guarantee that anyone who tells you Nibiru exists will not have an answer to these questions. They just change the subject.

It is true that stars and planets can hide behind the sun for a while. Take Sirius for example.

Sirius is the bright star just to left and below the middle of this photo of the night sky looking towards Orion (by kronerda).

You can see Sirius from the Northern hemisphere as a bright star in winter and early spring. It’s hidden behind the sun in summer and autumn. See Sirius is Dog Star and brightest star |

Here is how it works (Sirius is in Canis Major):

Why do different stars appear with seasons? (Beginner)

However, they can only be hidden for half the year. If a star is hidden from us in spring, you just need to wait until autumn, and there it will be, plain to view. Sirius is hidden in summer, but easy to see in winter.

That’s true of the planets too, for the ones that orbit further away than Earth. Venus and Mercury are different, they are so close to the sun that they just go back and forth to either side of it as seen from Earth - sometimes in the late evening sky and sometimes in the early morning sky.

But the outer planets Mars, Jupiter, and Saturn are visible in the night sky for half the year. At some point, every year, when we are roughly between the planet and the sun, each planet will rise when the sun sets, set when the sun rises, and is in the sky all night. It's the same also for the fainter planets further away, of Uranus, Neptune, and Pluto which you look at with telescopes.

Also, if anything comes into the inner solar system from beyond Pluto - which is possible with a long period comet - it has to take ten years to get here. Any faster, and it would be going so fast it would escape from the solar system, and can’t be in orbit around the sun.

So, when they say Nibiru is hidden behind the sun, it has to have been hidden for ten years at least on its long journey in - if it existed. And that is impossible of course.

Try asking this question if anyone tells you that Nibiru hides behind the sun. If it is hidden behind the sun in summer, where was it in winter, when Earth was the other side of the sun from where it is now? I guarantee that they won’t be able to answer this. If they are a "Nibiru true believer", they will just change subject.

They may say “Ah but it is dark, because it’s a brown dwarf”. Well, a brown dwarf is a “failed star”, a planet that is larger than Jupiter, nearly large enough to shine by its own light but not quite big enough. It is warm enough to shine by infrared light but doesn’t produce any visible light of its own.

Well, the Moon also doesn’t shine by its own light. Yet it is easy to see. The Moon is dark also, as dark as worn asphalt surfacing a road, as you can tell if you look at the moon rocks. It only looks so bright because the sunlight shining on it is so very bright and because the night sky is dark.

When we see the bright moon in the sky - this is what we are looking at, dark rocks as dark as worn asphalt. It looks so bright because the sunlight hitting it is bright, and because we see it against a dark night sky. This is a rare lunar meteorite, a meteorite found on Earth that comes from the Moon. Lunaite (lunar breccia)

Brown dwarfs vary a lot in how dark they are, but the very darkest brown dwarf at the distance of Jupiter would still be as bright as Betelgeuse.

Betelgeuse is the bright slightly reddish star towards the middle of this picture, by Till Credner, marking out the left shoulder of the constellation Orion. The darkest brown dwarf at the distance of Jupiter would be as bright as Betelgeuse

The other thing they are likely to do to change subject is to say that Nibiru is approaching us from the South pole and is only visible from Antarctica. Here is a rather hilarious (for astronomers) obviously fake video that is supposed to show Nibiru hovering above the South pole.

Please don’t be taken in by such videos. This is easy to fake. You can do it on an ordinary PC and you don’t need any special equipment. Probably can do it even with free tools nowadays. It is just a video of some base in an icy place, then fades to a wobbly photo of a planet like object, with sound effects added. Then the “planet” disappears off the screen to the top and the icy location reappears. It doesn’t even have both on screen at once, so this is an extremely basic elementary level faking.

The so called “Planet” here, I’m pretty sure is Saturn’s moon Mimas, from the distinctive shape of that enormous crater.

This is a better view of it:


Now if you pay any attention to the stars and know how to find the pole star, you may know that in the northern hemisphere whenever you get a clear night, you always see the pole star. What’s more it is always at the exactly same place in the sky. It doesn’t move at all, or only by minute amounts, all night and all year. Every day of the year, if it’s a clear night, look due North and up a fair bit, and there it is.

If you are close to the equator, then it’s very low just above the horizon, but again, always in the same place, same direction, same height, night after night. Here it is from Thailand.

This is a photo of the big dipper and Polaris from Thailand by Thammarith Likittheerameth - Polaris is that slightly fainter star at middle left. It is visible all night, every night, everywhere in the Northern hemisphere, except right at the equator. In Thailand it's close to the horizon, not high in the sky as it is here in the UK, but still is visible all night.

Well, it’s the same in the Southern hemisphere. Just as the pole star is visible from almost the entire northern hemisphere, the southern cross is visible from all of the southern hemisphere, except again, close to the equator.

Southern Cross

Anything visible in the night sky above the South Pole would also be visible in Australia, New Zealand, Southern Africa, South America, etc. That is, unless it is actually hovering above the South pole almost in the Earth's atmosphere.

So if they say to you that it is hidden from view because it’s approaching from the South, ask them, why then don’t we get all our Internet friends from the southern hemisphere shouting out to us that they can see a bright planet near the southern cross in their sky? (Or if you live there yourself, ask why you can't see it.) Again I guarantee that they can't answer this.

This all shows that this is an idea that spreads only because many people have no idea about physics. The people who say these things, as Neil De Grasse Tyson says, must have flunked physics at school.

That’s why astronomers just don’t give any time at all to these Nibiru people. They don’t really understand what it means for the Earth to orbit the sun, and they don’t understand how the stars work, and don’t know that the Southern cross is visible all night all year round throughout the southern hemisphere, or if they do know that, they haven't thought through the implications.

So - can you not see, these are not clear sighted people with a special understanding of the future, able to predict what is going to happen to us. They are just muddled, confused, deluded, people, and sometimes deliberately hoaxing us.

Sometimes you can be sure that it is just a hoax. This is a clip from a frame from a video recently posted to youtube that got many people scared.

Here is a photograph of the full Moon for a comparison

And here is the full video:

However much one might want to think that nobody could do such a thing, it is just not credible, that anyone would take a fuzzy video of the full Moon through a red filter, or post production edit it to look red, and not realize that they are videoing the Moon.

Please don’t be scared by this nutty idea or by the many people who jump on the bandwagon and share videos like this.

In this video I talk about why a planet in a 3,600 year orbit can't hide behind the Sun, as seen from Earth in our 1 year orbit.

I wrote this page after I realized from private messages that for some people with a not very strong background in physics and astronomy, that explanation wasn't clear enough. I think the reason is that as a geometrical explanation it's a little abstract, and it needed to be grounded more in everyday experience of how stars and planets work when you follow them in the night sky, as seen from Earth. So that is what this article does. 

Here I am again talking about some of the things I just said above, in an audio recording: Why Nibiru can’t hide behind the Sun.


So anyway with this background, it’s not Earth that’s in trouble here, it’s Nibiru; as it couldn’t be there.

Think about it. They say that this planet does repeated flybys of Earth every 3600 years. Well every time it did that, its orbit would change, through the gravitational effects of Earth on it. And if it flies past Earth, then of course on many orbits it would also fly by Jupiter, Saturn, Uranus and Neptune which are much larger. It can't miss them all indefinitely because they have different orbital periods.

There may well have been planets in orbits like that in the early solar system. But they did’t last long because within a few orbits they either hit Jupiter, hit the Sun, were ejected from the solar system, or were torn into pieces by tidal effects of a close flyby of Jupiter or melted in the heat of the Sun. It is not possible that there are any planets in orbits like this in our current solar system.

Our solar system can have extra planets, but to be still there after these billions of years, they have to be in stable orbits. The Planet X candidates that astronomers put forward have all been in orbits way beyond Neptune. The astronomers' hypothetical planets can never come anywhere near to Earth.


Now some people find this hard to understand because they hear that astronomers find new planets all the time. Well it depends how far away the planet is.

Tennis Ball with racket

If you have a tennis ball in your hand you can see it easily. If you look at a tennis game from a distance it might be quite hard to see the ball sometimes. And if you look at it from, say, ten miles away you can’t see it at all.

It’s like that. The Pan STARRS telescope, which searches for asteroids every night can see objects of up to 300 meters in diameter right out to the outer edge of the asteroid belt, in ideal viewing conditions when they are high in the night sky. Our telescopes have already found all the asteroids of 10 kilometers in diameter or larger in Earth crossing orbits inside of Jupiter, and 90% of the ones of 1 kilometer in diameter (expected to find 99% of those some time in the 2020s). So we could still be missing objects of 1 km in diameter out to Jupiter, but not something of 10 km in diameter.

When you get to the distance of Neptune and beyond then we are still discovering objects of the order of 100 km in diameter. And when you get to many times the distance to Neptune or Pluto, then we might be able to find planets as big as Earth or even Jupiter, they think, if far enough away. And around distant stars, light years away, we think that just about every star has planets, and they are very hard to spot from Earth, because they are so far away.

In the other direction, towards the sun, then we could miss asteroids inside of Mercury. Immediately inside Mercury, the orbit would be unstable, and an asteroid could only be there for a short time. And very close to the sun, the rocks would boil and then evaporate in the heat of the sun. But in between, there is a zone where there could be asteroids hidden from view. 

Vulcan - Le Verrier's hypothesized planet between Mercury and the sun and smaller than Mercury - would have been a hot object something like this artist’s impression of exoplanet Kepler 10b (Image credit: NASA) We now know Vulcan (the hypothetical planet in our solar system that is) doesn't exist, but there could be tiny asteroid sized objects nestling close to the sun, close enough not to be disturbed by Mercury, and yet, just far enough away so that the rocks don't boil and evaporate in the heat of the sun.

There have been searches to try to find them using space telescopes, and nothing has been found yet. If they exist, they could be up to a few tens of kilometers in diameter. We know that there aren't any vulcanoids larger than about 60 km assuming they are similar in darkness to Mercury.

Other searches with NASA's two STEREO spacecraft (which looked at the Sun at a different angle from Earth) suggests there are probably no vulcanoids larger than 5.7 km in diameter, and no more than 76 of them larger than 1 km in diameter.

If these objects do exist, they are of no risk at all to Earth because they are so close to the Sun, tightly bound in an orbit that goes around the Sun many times a year.

Then in addition to all that, we also have strong limits on any kind of matter, including invisible "dark matter" in our solar system. We have a spacecraft orbiting Saturn - Cassini - and also many orbiting Mars, and have long timelines for them with very precise distance measurements. As a result, we also know the positions of those planets very exactly. So we can use them as sensitive measurements of the effect of gravity of everything in the inner solar system inside of Saturn.

As a result researchers have come up with Constraints on Dark Matter in the Solar SystemBy "dark matter" they include all forms of matter we haven't detected yet, including tiny asteroids or gas or dust, and also even forms of matter that we hypothesized but haven't discovered yet such as the hypothetical WIMPs (Weakly Interacting Massive Particles).

It turns out that we are missing less than a seventh of the mass of Ceres. 

Ceres, Earth and Moon comparison. From the motions of our spacecraft around Saturn and Mars we know that we have accounted for nearly all the mass inside of Saturn's orbit. We are missing at most a seventh of the mass of tiny Ceres in there. 

This shows we can't even have a hidden large asteroid there, anywhere inside of Saturn, say as large as Pallas (about a fifth of the mass of Ceres), no matter how dark it was, no matter where it is, as it would have detectable effects on our spacecraft.


For an everyday example, suppose that a friend tells you that you have a cow in your house. Every time they pass your house they hear it mooing and they’ve even seen it. Well would you believe them?

That’s the sort of thing you’d know about. There’s no way you could miss a cow in your house. If they keep saying this, like the Nibiru people who keep saying there’s a hidden planet in the inner solar system, well you just would give up eventually, just politely leave them to their beliefs.

That is, unless you actually do have a cow in your house :).

Then you would believe them. But it’s not the sort of thing that could happen, and you don’t know about it. But if they say that they have lost their keys in your house, then yes, you’d hunt around, do your best to find them. So it’s like that.


Now there are things that can threaten us. Not planet sized. Not even 100 km in size. Nothing large enough to make humans extinct even with the most basic stone-age technology. But there are things that could be seriously bad news for us even so.

Well - first - don’t worry about them, as they are very very rare. You can be 99.999999% certain you won’t be hit by a giant asteroid this century. You are far more likely to be killed by a tornado or a lightning strike, and far far more likely to be killed in a car crash. These everyday things are the main things you need to take care about.

However the asteroids are important because they are the one natural disaster we can actually predict to the minute. Astronomers when talking about real asteroids that fly past the Earth don’t say “oh it could fly past in spring” then when spring comes and it doesn't come, say “oh it will fly past in autumn” or “ it will fly past just before Christmas” or whatever.

They will say - it will fly past on such and such a date, at this exact time to the minute. If you know enough about the orbit to know it is going to fly past Earth, you definitely know exactly when it will do it too. Because the Earth moves by 108,000 km/h so if you got the time of the flyby wrong by even a few hours, then it would be further away than the Moon. If you got it so wrong you said spring instead of autumn, it would be twice the distance to the sun away from us.

So - you have a prediction exact to the minute. If we can predict it a decade in advance as well, just a gentle nudge will move it. It’s enough to change its velocity by a little more than the speed of a fast moving snail to get it to miss the Earth a decade later by an Earth radius. And if it does a flyby of Earth first, then it will have a tiny “keyhole” of a few hundred meters it has to go through to hit Earth next time around. Now you just need to change its velocity by a few cms a day!

So the main priority here is to track these things and predict them. If we can predict them long in advance we can prevent the impact. And - we are much more at risk from volcanoes, earthquakes, tsunamis etc. Nobody in recent history has been killed by an asteroid, though some have in ancient history. Even then we haven’t had anything like an asteroid equivalent of Pompeii.

So, it's not something to be alarmed about. But given how predictable asteroids are, and that we could evacuate the impact zone, avoid injuries such as for the Chelyabinsk meteorite with a warning to people to stay away from windows, or given enough warning, deflect them to miss Earth completely, I think we should do a lot more than we are doing, to deal with this easily detected and preventable hazard. We are searching for them. But the astronomers could do so much more with a bit more funding.

The UK government has just voted to approve renewal of the Trident nuclear weapon system at a cost that is not capped, and is likely to be at least £180 billion ($236 billion) over its lifetime with the latest independent estimates, and some say it will cost the UK £205 billion ($268 billion). The government themselves in the parliament debate refused repeated requests by MPs opposed to Trident to give an estimated lifetime cost themselves.

HMS Victorious at Clyde naval base. Photograph: Reuters. Replacing Trident will cost at least £205bn, campaigners say

When we spend so much on defending against each other - whatever you think about whether we should have done it or not (disclosure, I think we should be working towards world wide nuclear disarmament myself, and that the UK could take a lead there) - whatever you think of that, could we not spend a tiny fraction of the amount we spend on nuclear weapons, on defending Earth against asteroids?

For half a billion dollars, less than 0.2% of the cost of Trident renewal, the UK government, unilaterally, could launch a spacecraft to Venus orbit which would find the majority of hazardous objects right down to 20 meters in diameter in a decade. Astronomers know exactly what to do to find these objects, they just need the funding to go ahead.

The Sentinel space telescope. Estimated cost half a billion dollars (380 million pounds)

It would sit inside of Earth, close to Venus's orbit. It looks away from the sun and can see faint NEOs that are in between the Earth and the Sun which is the hardest place to spot them from our current Earth based surveys. It would help fix that blind spot. It looks in infra red because the asteroids are far more obvious in the infrared, even ones that are very dark in visible light. The idea is that it would find nearly all potential impactors down to 40 meters in diameter. And recently announced, that it should be able to spot them down to 20 meters diameter.

They hoped to launch it in 2017 to 2018 on a Falcon 9. And to find 90% of NEOs down to 140 meters within ten years and a significant proportion of all NEOs down to 20 meters. - but sadly though they got millions of dollars of private donations, they never got enough funding to meet that schedule. It is still on the go, but they won’t be able to fly it any time soon, unless someone steps in with more funding to fill the gap.

Even a billionaire, a philanthropist individual, could do this. There are over 500 billionaires in the US, over 200 in China, over 100 in Germany, and India, and over 50 in the UK, Brazil, Hong Kong, or Russia. See list of countries by numbers of US billionaires.

It would effectively retire most of the remaining risk from asteroid impacts. This is a real thing, and we could do something about it too. Nibiru, as Neil deGrasse Tyson said, is imaginary fiction.

For more on this see my Giant Asteroid Headed Your Way? - How We Can Detect And Deflect Them


If you search the web you get thousands of pages from the conspiracy theory websites, the sensationalist websites float to the top of the google and youtube results. And I agree, these sites do get people very scared.

"Before it's News" is one of the worst of those - a sensationalist site where anyone can post anything, often completely made up and the most sensationalist hoaxes are listed as the top stories for the day. The other week one of their top stories was that the Moon is an illusion and transparent (they didn't cover eclipses of the sun of course). They often have articles claiming that the Earth is flat and that the governments of the world are covering up the flatness of the Earth (for reasons rather obscure). And back at the time of the 2012 scare, 20% of all Chinese thought the world was about to end, with figures like 10% in some other countries. Luckily,lots of people worrying that it will happen doesn't make the world end.

While astronomers for the most part don't post about it at all, becuse it is too nutty an idea for them to think it worth mentioning. As an example Mike Brown just has the one post about it, I do not ♥ pseudo-science. Brian Cox even less, j he doesn't think it is worth spending more than one tweet's worth of words on it. But there are a fair few who debunk it in more detail if you know where to look.

Here are a few


And "Imaginary Bullshit Planet" Nibiru (free to read online) is also available as a kindle booklet

Get this as a kindle ebook (127 pages)

(BTW I plan to do a new book when I have time, incorporate some of the things from my other articles like this one)

Get notifications of new blog posts

If you want to get alerts every time I do one of these posts, join my Robert Walker - Science20 Blog Alerts facebook page.

To get a red facebook alert every time I post a new science20 article, or post an idea for a new article, then select "all on" in the page's Liked drop menu above.

Or subscribe to the associated twitter feed.

For email alerts about once every month or so, subscribe to Robert Walker's Science 20 blog Monthly Alerts on Google Groups.

This article was originally posted as my answer to Would we be in a stable orbit if Nibiru were just behind the Sun? on quora.