Discovered: A Planet With As Many As Four Suns!

Forget the world, the Sun is not enough. Astronomers have found a planet outside our own Solar System, which has as many as four suns! Yes, this planet, thought to be a gas giant, orbits four different suns.

And add a few more suns…

Discovery

The planet was discovered by volunteers who were using the Planethunters.org website, which allows enthusiastic astronomy amateurs access to a lot of data from NASA’s Kepler’s Space telescope. Kepler is built specifically for detecting exoplanets. The planet, named PH1, after the website, is just 5000 light years away, a stone’s throw away on the cosmological distance scales.

The technical ArXiv report is here: http://arxiv.org/abs/1210.3612

The planet is believed to be about the size of Neptune, just a bit larger. The interesting thing about this planet is the number of suns – there are four of them. Now, maintaining a stable orbit around four different suns is a very difficult and delicate problem. While it is moderately difficult to calculate the stable orbit configurations around one star, it is a huge pain to do it around two stars and impossible for four suns! There are virtually no stable points in the gravitational field in the region, where the planet can reside for an indefinite period of time.

Gravitational Confusion

We all know a single star – our Sun is an example. Now, imagine another star around it. This forms a binary system of stars. These are very abundant in the Universe – two stars circling around each other – and these reveal a lot of information about star formation and their subsequent evolution. Now, add two more stars orbiting this central binary system of stars! This is a highly improbable configuration. These outer stars will have a very hard time following a stable orbit around the core binary.

Now, throw in a gas giant planet in the mix! And what you get is utter confusion, if you could somehow see the pattern in the gravitational field. No one knows for how long this planet has existed or for how long it will exist.

One can only imagine the spectacular sunrise and sunset on the planet, but then all four suns won’t be rising or setting at the same time.

Shopping for Diamonds—in Space

Astrophysicists are hypothesizing that a previously discovered planet could have a diamond interior.

This planet, called 55 Cancri e, is an exoplanet (a planet outside the solar system) that orbits a star called 55 Cancri. Its was the one of the first ‘Super-earths’ to be discovered—its mass is greater than that of earth (around 7.8 times), yet much smaller than the masses of Uranus and Neptune. Estimates of its interior composition and atmosphere had already been made from previous studies observing its transits across the star (similar to the much talked-about Venus transit earlier this year). It was estimated that this planet had a core of iron and silicates, and an envelope of supercritical water (i.e., water in a blurred state between liquid and gas).

However, these estimates were based on the assumption that the planet had an oxygen-rich interior, similar to earth. This assumption is now being challenged in a new model proposed by researchers at Yale University. The star around which the planet orbits itself has a carbon-rich interior, and 55 Cancri e is the closest planet to the star. This led to a new model that the planet could have an interior of carbon instead of oxygen, which could also lead to the observed properties of the planet.

An illustration of the planet 55 Cancri e’s interior. A molten iron core at its center, an outer layer of graphite, and an interior of diamond. [Image Credit: space.com and Haven Giguerre]

However, based on the known temperature and pressure of 55 Cancri e, any carbon in its interior would have to exist in the form of diamond. “This is the first glimpse of a rocky world with a fundamentally different chemistry from Earth. The surface of this planet is likely covered in graphite and diamond rather than water and granite,” said Nikku Madhusudhan, who was the first author on this paper.

If this proves to be true, the phrase ‘like a diamond in the sky’, may turn out to be more than a simile. You can read about this research here and here.

“Odd Couple”: Kepler Exoplanets Defy Known Planet Formation Theories

As if astrophysics didn’t have enough problems on its hands, it seems that a new discovery has handed over a new challenge. An exoplanet pair, discovered by the exoplanet hunting Kepler Space Telescope, unimaginatively named Kepler 36-b and Kepler 36-c according to accepted catalog practices, turns out to be spectacular blow for established planet-formation theories.

An artist’s impression of the how the second planet would look standing on Kepler 36-b, when the two planets are close to one another. (Photo Courtesy: David Aguilar, Harvard-Smithsonian Center for Astrophysics)

A problem…

The two planets are very close to one another. They orbit their parent star, but they are separated by only 1.9 million kilometers. This turns out to be 0.01 AU, an AU being an ‘Astronomical Distance’, which is the average distance between the Earth and the Sun. So the two planets are a hundred times closer to each other than the Earth is to the Sun.

Astrophysicists wouldn’t be worried, yet. True this is very odd, but it doesn’t transgress the rule books. Here comes the blow: The two planets are as different as Venus and Neptune!

How is it a problem?

In our own Solar System, Venus is a rocky planet meaning that it has a solid rocky ground to stand on. It’s not a ball of compressed gas. In fact, Venus very much has a surface and it is riddled with numerous volcanic features, like volcanic domes, large fissures on the ground and rolling planes formed by large sheets of solidified lava flows. Kepler 36-b is not quite Venus in the volcanic sense, but is definitely rocky. It’s more like Earth, minus the oceans. Only that it is four times heavier than Earth, suggesting that is very dense.

Neptune is as unlike Venus as a planet can get. It is a gas giant and has no solid ground to stand on. It’s much larger than either Venus or Earth. Kepler 36-c resembles this gas giant.

Making planets

Planet formation theories suggest that when the disc of rocks, gas and dust spinning around a parent star coalesces in clumps to form planets, the gas and dust are naturally flung far away from the center, while the rockier bits of the initial soup of raw materials stay within the vicinity of the parent star. They coalesce to form rocky planets. This explains the occurrence of rocky planets to the interior and the presence of the gas giants farther out for our own Solar System.

Since the forces involved in this process are those of gravitation (due to the star) and the centripetal forces (due to the rotation of the disc of raw materials), scientists would have expected the same rule to work for any planetary system, as these forces are both ubiquitous and inescapable.

But that can’t be the whole story!

That however is not the case apparently. The atmospheres are also very fascinating. Kepler 36-c has an atmosphere which is 10 times as dense as Kepler 36-b, even though they are at almost the same distance from their parent star.

Scientists like puzzles, especially those which can rewrite books. Nothing is ever sacred, not even the physics of the heavenly bodies.

Discovered: The Best Bet Yet For A Super-Earth, And It’s Very Close Too!

This might be even better than Kepler 22b! An alien exoplanet has been discovered, which resembles our own Earth the most. It is the best bet scientists are putting forward for a planet outside our own Solar System that is capable of harbouring liquid water. It lies in just the right zone – called the Goldilocks Zone – at the perfect distance away from its parent star and might even be congenial enough to harbour life of the form we see on Earth. It is also our next door neighbour, being just 22 light years away. The planet is christened GJ 667C.

An artist's impression

Just to give you a sense of how close GJ677C is, consider the fact that there are only 100 stars closer to Earth than this planet. The planet occurs bang in the middle of the Goldilocks zone, as Steven Vogt, astronomer at the University of California, Santa Cruz, emphatically stresses in an interview to space.com:

It’s right smack in the habitable zone – there is no question or discussion about it. It’s not on the edge, it’s right in there!

The planet is about 4.5 times the size of Earth, but is not gaseous. It is rocky, having a composition similar to that of Earth. It orbits its parent star in only 28 days. The parent star is one of a triple-star system, which by itself is a nice fact about this planetary system. The star is a faint M-star, but still visible from Earth. This faintness of the star explains the fact the planet is quite close to the star – as indicated by its small orbital period – while still being in the Goldilocks zone, which is in itself a first instance. It just shows that there are systems which, otherwise deemed boring, might be worth checking.

The sight of the sky from GJ667C should be great! It’s parent star is one of a triple-star system, which means that apart from its own sun, the planet’s sky has two more suns, which are also just far enough to not destabilize the orbit or burn up the planet. Vogt does the explanation again:

The planet is around one star in a triple-star system. The other stars are pretty far away, but they would look pretty nice in the sky.

The study was published in Astrophysical Journal Letters.