Replica Solar System discovered 5,000 light years away

BBC News

Back in ancient times most people thought that our planet was at the center of the Universe. Then we thought it was the Sun, and not too long after we realized that we’re actually just a tiny part of one of billions of galaxies in a Universe filled with trillions of other stars. Just over a decade ago one of the last things that we thought might be unique about our Solar System was disproved – the first ever planet outside our Solar System (an ‘exoplanet’ for short) was discovered around another Sun.

Wikipedia Now our uniqueness has been eroded away a little bit more – a British team of astronomers has discovered what looks a bit like a replica of our own Solar System, orbiting around a star 5000 light-years away.

OK, it’s not an exact replica, but the resemblance is quite striking. Two giant gassy planets (like Jupiter and Saturn in our own Solar System) have the same mass ratio to their sun as Jupiter and Saturn have to our own Sun. And the size of their orbit is proportionally the same as the orbits of Jupiter and Saturn. (The star in the newly discovered system is only about half the size of our Sun, hence the reason why all the figures are given as ratios). The orbital period of the giants is about the same too.

So what about a copy of Earth and the other inner, rocky planets? Well, the scientists didn’t actually discover a new Earth, but they say that the existence of an Earth-like planet is quite likely because there is plenty of empty space in between the gas giants and the star.

Wikipedia Unfortunately there’s not much chance of us discovering any more planets in this system – at least not yet, anyway. Current techniques simply aren’t powerful enough to see such small objects so far away.

But wait a minute… if the system’s so far away, how could we detect that the giant gas planets were there? They’re pretty tiny too, surely, compared to the size of their sun?

They used a clever trick called ‘gravitational lensing’, which involves the effect first predicted by Einstein that if you put a heavy object (like a star) in front of another object (like another star further away), the star in front will bend the light from the star behind because gravity bends light. This enables us to see faraway objects much bigger than we would usually be able to see them. (Click here to read more about gravitational lensing, and how it enabled the Hubble Space Telescope to see a galaxy 13 billion light years away.)

Since we don’t know for definite that there’s a replica Earth in this system, should we really be getting so excited? I think the answer should definitely be yes – in the decade since we first discovered extrasolar planets, 300 planets outside our Solar System have been discovered. The more variation among these planets, the more chance of eventually finding ET. And that would be seriously cool.

Click here for NASA’s excellent exoplanet website: PlanetQuest.


The youngest planet ever discovered – only a few hundred years old A few hundred years is a huge length of time for humans, but in cosmic terms it’s absolutely tiny. A hundred years in the world of Space could easily be compared to a millisecond for humans. But now scientists have discovered a planet that may have formed in as little as a few hundred years – which beats the former fastest forming planet by about 10 million years.

OK, it hasn’t finished growing yet, but the fact that it can be classified as a planet when it’s only been around for so little time is amazing astronomers all over the world. And the planet’s not the only interesting thing – its sun has only been around for a few hundred thousand years. (By the way, the planet and its sun are around 520 light years from Earth.)

So if this planet’s so young, how did astronomers find it? They used the Very Large Array (VLA) in Arizona to search for wavelengths of radiation that corresponded with pebble-sized lumps of rock (different sizes of rock emit different amounts of heat). They looked for pebbles because they are a vital hint that a planet is being formed.

National GeographicIt may be an intriguing discovery, but does is actually mean anything in terms of knowing more about our Universe? It certainly does – and it is stirring up quite a lot of controversy in the process. When stars form, they develop an area of rocks and gases around them, and these rocks and gases can eventually start to group together too form planets.

People used to think that planets formed when these rocks randomly collided, creating bodies with bigger and bigger gravitational attraction, which led to a sort of runaway growth. But this would take a very long time to produce a planet. An alternative theory, backed by this latest discovery, is that planets actually form when an area of greater density within the area of rocks orbiting the star starts to contract, a process that could be complete within several thousand years.

OK, the difference between the two methods of planet formation don’t sound huge, but they have massive implications for scientists trying to understand the origins of our Earth. Let’s just hope that the meeting of the British Royal Astronomical Society (where this discovery was announced) won’t turn into a war between feuding scientists.

Saturn’s moon may have rings – the first ever discovered

An artist's impression of Rhea's rings | Image: NASA

Everyone knows that Saturn has rings, but what about its moons? Surely they don’t have rings as well? Well actually, Rhea, a moon of Saturn that is usually overlooked, may be the first moon ever discovered to have rings, thanks to new research from the NASA/ESA Cassini-Huygens mission.

Rhea’s rings aren’t particularly impressive compared to Saturn’s – after all, it’s hard to imagine anything having a more impressive ring system that the huge gas giant Saturn. In fact, they haven’t even been photographed yet, but there is strong evidence to show that they exist.

Saturn | Image: Wikipedia How did the scientists work out that Rhea had rings without even seeing them? It’s all down to electrons, tiny charged particles that surround Saturn in its magnetic field. Because Rhea lies within the magnetic field of Saturn, it was expected to be seen ‘clearing up’ some of the electrons, because Rhea would absorb electrons from the magnetic field.

Saturn's rimgs, as imaged by Cassini | Image: NASA / ESA Rhea certainly did clear up the electrons – but it did it far better than expected, absorbing electrons about 7 times further away than it should have done. Why? The only feasible answer seems to be that Rhea has a ring system, and that the ring particles are absorbing the extra electrons.

Rhea is just one of a group of Saturn’s 52+ moons that are intriguing scientists: Rhea’s cousin Titan has methane lakes and rain; Iapetus is half-black and half-white; Enceladus has an atmosphere. The Cassini-Huygens mission is making it obvious that Saturn’s moons are just as interesting as the ringed planet itself.

Venus: The planet where it rains acid

Venus in visible light | Image: Wikipedia

Everyone seems to complain whenever it rains here on Earth, but on Venus you might actually have good reason to moan. Instead of water Venus’s clouds are made of corrosive sulfuric acid, and if you got covered in that, chances are you wouldn’t be around very long to tell the tale.

In reality it never rains sulfuric acid (at least not down to ground level) on Venus, because it evaporates before it has time to hit the ground – in fact, surface temperatures on Venus are hot enough to melt lead.

New research from ESA’s Venus Express probe is starting to reveal some of the secrets of Venus’s atmosphere, and some of them are very surprising indeed.

Unlike on Earth, where clouds tend to move only a few hundred miles at most, sulfuric acid clouds on Venus have ben seen moving from the poles to the equator, then back to the poles again, in just a few days.

Venus Express, which is due to end its mission in May 2009 | Image: ESABut wait a minute… where does all this sulfuric acid come from? After all, Venus is sometimes known as ‘Earth’s evil twin’ because of its runaway global warming, caused by excess carbon dioxide levels.

In fact, 97% of Venus’s atmosphere is made of CO2, although there are small amounts of gases such as sulfur dioxide and water vapor.

Recently discovered by the Venus Express probe is that the sulfuric acid is created when the sulfur dioxide and water vapor rise to the top of the atmosphere and are exposed to ultraviolet rays from the Sun, causing them to react and form sulfuric acid.

Why do they rise up? That’s one of the many things that remains to be found out, hopefully during this last year of the phenomenal Venus Express mission.

Click here for an interactive guide to Venus

Mars in 3D for the first time

The new 3D view from Mars Express | Image: National Geographic / ESA We’ve seen Mars from an aerial view, we’ve seen it from the ground, but what about in 3D? Well now we can do that too, thanks to Europe’s Mars Express probe.

The 3D shot (right) of Olympus Mons, the biggest volcano or mountain anywhere in the Solar System, shows the topography of Mars in unprecedented detail. There are amazing possibilities for this kind of information when it is combined with aerial views, such as the one to the below.

But why do we want to know loads about the altitudes of different bits of Mars? Well, it could actually play a pivotal role in the search for life, because by analyzing the altitudes of hills and surface features, scientists are able to tell where water has once flowed. It is thought that life could only ever have existed where water was present.

An aerial view of Olympus Mons | Image: WikipediaAnother big question: how on Earth do you get 3D shots like this? The obvious first thought would be radar or lasers, which NASA has previously used on its Mars Global Surveyor mission. However, these only provide the height at the exact point under the probe.

To get detailed measurements over a wide area, Mars Express used a technique that involved taking three photos: one slightly before it was overhead Olympus Mons, one above it, and one slightly after it had flown over it. By combining these three different angles, scientists were able to construct a 3D image.

We’ve only just started our exploration of Mars; there are loads more probes set to explore the Red Planet before 2030, NASA’s target date for the First Man on Mars. It’s a pretty exciting time to be in for space exploration! The Mars Express probe | Image: ESA

Mercury: The planet with a spider

Messenger has discovered that Mercury has faint blue and red/pink tinges to its surface, as shown in this image | Image: National Geographic / NASA

The only reason we have mountains is because the Earth is shrinking, causing its surface to buckle up into peaks. At least that’s what people believed 200 years ago. Nowadays we know that it’s all down to tectonic activity on Earth, but somewhere else in our Solar System, shrinking may actually be the reason for mountains. The planet: Mercury.

New images released by NASA following the flyby of Mercury by their Messenger probe in January have revealed strange new things about a planet that up until now was considered, well, boring.

So what caused Mercury to shrink, and then create these huge mountain chains? It’s all down to the fact that Mercury’s interior cooled after its formation; when things cool, they contract. Because Mercury has not had any tectonic activity (volcanoes, earthquakes) for billions of years, the effects of that contraction can still be seen today.

The 'spider' volcano formation | Image: National Geographic / NASA Also revealed in the new photos was a strange feature, dubbed ‘The Spider’ (see image on right). It is thought to be the remnants of an ancient volcano, though there is also a meteorite crater near the peak.

Another revelation was that Mercury’s not so bland and colorless after all – faint blue and red/pink tinges have been detected by Messenger’s cameras (see image at top).

Messenger makes another flyby in October this year, then again in 2009, before finally coming into orbit around the Solar System’s smallest planet in March 2011. I think we can expect plenty more fascinating news from Messenger over the next few years.

See my previous posts about the Messenger missions to Mercury here and here.

What’s so great about Mercury? Quite a bit, actually.

What’s so great about Mercury? Isn’t it a bit boring, with no rings (like Saturn has), no giant storms the size of Earth (as on Jupiter), and in fact nothing but loads and loads of craters?

Even if doesn’t seem particularly special, Mercury still looks beautiful, and it can tell us a great deal about the history of our own planet.

NASA’s Messenger probe, the first one to visit in over 30 years, has taken some stunning shots, a few of which are posted below. Click to enlarge.

For more information, NPR’s Science Friday had a fascinating interview with a scientist working on the project, which can be downloaded here (about 20 minutes long)


Messenger actually got just 125 km from Mercury’s surface, enabling it to get detailed pictures of the craters that cover this rocky planet. One crater, the Caloris basin, is among the biggest in the Solar System.







 Why so many craters?

The other planets have been bombarded almost as much as Mercury during their 4.5 billion year history, but because Mercury has no wind, water or volcanic activity to erode the craters away, it’s far more cratered than the other planets. Looking at Mercury’s craters can tell us what our Earth used to be like.

Some scientists suggest Mercury may have been bombarded more than other planets, because there would have been more asteroids the closer you got to the Sun.



Why no color?

All the other planets either have colored elements in their rocks – like Mars, which contains large amounts of iron – or they have an atmosphere – think of Jupiter and Saturn. This leaves Mercury looking much like our Moon.