Category Archives: Science

The Lost Planets of Sol

Astronomers, in their search for new planets, are constantly positing the existence of worlds that haven’t turned up. Here’s some of the most famous worlds that astronomers have been looking for evidence of.

1. Planet X

Man from planet xPlanet X, despite the numeral, is a hypothetical ninth planet. Oddly, it was first postulated in 1834, before the discovery of an eighth planet. An astronomer called Hansen believed that there would need to two extra planets to explain irregularities in the movements of Uranus. Scientists predicted the position of Neptune without it, but irregularities in the orbit of Neptune caused new problems and the search for Planet X really began.

Percival Lowell, most famous for his claims about Martian canals, became particularly emotionally caught up in the search. In fact, the stress of searching may have killed him. Lowell would have been pleased that after his death his observatory discovered Pluto. It wasn’t big enough to change Neptune’s orbit, but it was a major breakthrough.

The search for Planet X lasted for over a century, but in 1993 it was suggested that based on data about Neptune from the Voyager 2 flyby, there would be no need for a Planet X. With that, one of the longest hunts for a planet came to a disappointing end.

2. Phaeton

Phaeton in Greek myth was a guy who unwise tried to drive the chariot of the Sun, but crashed it into the Earth and had to be struck down by Jupiter. Appropriate choice, I think.
Phaeton in Greek myth was a guy who unwisly tried to drive the chariot of the Sun, but crashed it into the Earth and had to be struck down by Jupiter. Appropriate choice, I think.

In the 18th century, astronomers noticed that the planets were regularly spaced, provided you place a fifth planet between Mars and Jupiter. This was called the Titius-Bode Law. Excitingly, when they discovered Uranus, it fit the pattern, this led some astronomers to get interested in the missing fifth planet.

In 1801 the first asteroid, Ceres, was discovered, and it looked like the fifth planet had been found just where it was expected to be. However, it was too small, and there were many other asteroids like it in the same area. The idea was put forward that the asteroids were created by the destruction of Phaeton, the fifth planet.

Today, a lot of astronomers would argue the reverse. Not that the asteroids were a planet that became rubble, but that it’s rubble that didn’t become a planet. However, some astronomers are still looking for evidence of a fifth planet.

One theory about a fifth planet ignores its role in forming the asteroid belt entirely and instead tries to explain a period of intense asteroid impacts on Earth.  3.9 billion years ago, they argue, Planet V was half the size of Mars located between Mars and the asteroid belt. It developed an unstable orbit which sent it through the belt and back towards the inner planets, carrying asteroids in its wake. Eventually, its orbit took it into the Sun.

3. Vulcan

Not this kind of Vulcan

The planet Vulcan was first hypothesized by Le Verrier in 1860, he noted irregularities in the orbit of Mercury and believed that a small planet closer to the sun than Mercury may be the cause. In the 1860s and 1870s black dots near the sun were assumed to be Vulcan on a few occasions.

In the 20th century applying astronomers applied the theory of relativity to the orbit of Mercury and found that it worked without there having to be another planet. This left a problem: what were the objects people had seen while looking for Vulcan? Some astronomers believe there may be a small group of asteroids between Mercury and the Sun. Once again, the search for a non-existent planet could turn up some nice new asteroids as a consolation prize.

4. Theia

Theia_giant_imapct_hypothesisThe Moon is very much like the Earth in terms of its composition, leading some people to believe that the Moon must have been created when a chunk of the Earth was thrown into space by a giant impact. Theia is a hypothetical planet that developed in a stable area between the Earth and the Sun, but it grew too large and fell towards Earth four billion years ago.

Estimates on the size of Theia range from Earth sized to the size of Mars, and some reject the idea entirely, saying that Earth and the Moon aren’t similar enough to justify it.

5. Nemesis/Tyche

A cloud of comets, called the Oort Cloud, surround our solar system
A cloud of comets, called the Oort Cloud, surround our solar system

Nemesis was a red Dwarf Star on a highly eccentric orbit which passes through the Oort Cloud every 28 million years, sending comets into the inner solar system. Each time this happens, it causes a mass-extinction event. The idea that we’re in a binary solar system with a second, secret star of death is a really nice romantic notion. Unfortunately, the telescope we have scouring the skies for Nemesis has turned up nothing. And it is now widely accepted that there’s no red dwarf to be found.

Tyche was a kind of budget-Nemesis. It would only need to be a few times bigger than Jupiter, and was an attempt to explain the orbits of comets, and, later, of Sedna. It was first suggested in 1999, but there was a spate of stories about how “scientists could soon discover a new planet” in 2011. But it didn’t seem to be based on anything more than the fact that we had the technology to look for it. So far, there’s no evidence that such a planet is out there.

6. Fifth Gas Giant

Some current theories of planetary formation indicate that gas giants like Neptune and Uranus are too far out to have evolved in their current orbits. If this is true, they must have been created closer to the sun, and migrated outwards. Unsurprisingly, it’s difficult to move a herd of gas giants out of a young solar system full of debris without destroying any smaller rocky worlds in the region.

Some astronomers believe that the best way to get the outer planets from where they think they were created to their current orbits would be to have a fifth gas giant that had a “violent encounter” with Jupiter, that pushed the gas giants out and ejected the fifth world from the system.

In 2013, we started to find rogue planets, which have probably been ejected from their own solar systems into deep space. So it’s a possibility. Maybe in the next few decades we can start to locate planets that have been kicked out of our own system.

So what…

We tend to think of planets as an unchanging, monolithic kind of thing. But it seems that conditions everywhere have been shaped by planets swapping places in the past, and they may move again in the future.

Is this a random process, ruled by chance alone? The fact that planets are regularly spaced could indicate a pattern behind it, but the Titius-Bode Rule failed to predict the location of Neptune, so maybe it was just a coincidence. However, some astronomers are starting to see similar patterns in other systems. So, maybe there’s some kind of reason and pattern to these movements. I don’t know, ask a scientist. Or if you want a definitive answer, your best bet is to just ask God. If you can find him.

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How planets can escape ultimate fiery oblivion with the power of explosions

The media is only interested in an exo-planet these days if it’s passingly similar to Earth, but some of the most fascinating worlds are interesting because they’re not Earth analogues.

Take the BD+48 740 system, the star  is a red giant that has already expanded sufficiently to have eaten most of the inner planets that may at one time have circled it. But it has one known world; the romantically named BD+48 740b which is a gas giant 1.6 times the size of Jupiter. There’s two strange things about this system:

1. A unusually high concentration of lithium in the star’s atmosphere.

2. The planet has an unusually high level of eccentricity to it’s orbit. In it’s super-heated Summer it gets closer to its sun than Venus is to ours, and in its winter it is much further out than Mars is in our system.

Our assumption is that at one stage, this system had an inner planet, but as BD+48 740 expanded it got pushed into the star, the crash caused an explosion that pushed BD+48 740b out of the way of the sun and into it’s current eccentric orbit. This kind of explosion would also have also generated the Lithium in the star’s atmosphere.

This is exciting, because it means that there is another way for a planet to end it’s life. We always thought that there were basically two things that can happen as a star like ours expands: either it expands quickly and pulls many of it’s worlds into it. Or it expands slowly and the extra energy it emits slowly pushes the planets away from it until they eventually freeze. BD+48 740b seems to have found a kind of a happy medium between the two.

Which leads me to wonder, could we do this? In five billion years time maybe we’ll decide we want to save the Earth from fiery oblivion. As the process of getting sucked into the sun takes thousands of years, we won’t necessarily have time to reverse that trend in the lifespan of a single civilisation. But it might be possible to push Venus in ahead of us to save our own world from destruction. 

It would, at least, make an interesting premise for a science fiction story.