2 years ago the Kepler probe was dealt a critical blow. Out of 4 reaction wheels, the devices which keep the telescope pointed in the right direction, only 2 remained functioning. This meant that the telescope was no longer able to maintain the level of precision required to continue its planet hunting mission. However there was a bold plan to continue Kepler’s mission, albeit in rather different capacity. Kepler could use the solar pressure exerted by our sun as a third reaction wheel, allowing it to continue imaging the sky and looking for planets. It wouldn’t be able to look at the same piece of sky for the entire time however and would be limited to viewing periods of approximately 80 days each.
Whilst this was a significant downgrade in Kepler’s abilities it was a far better option than just retiring the spacecraft completely. In its previous incarnation Kepler was able to track hundreds of thousands of stars continuously, allowing us to detect numerous planets orbiting their parent stars. In its current incarnation Kepler will only be able to detect planets with shorter orbits which are unlikely to be the Earth-like ones we’re all hoping for. Still even in that reduced capacity Kepler has been able to identify no less than 100 new exoplanets with over 200 additional candidates awaiting confirmation by other methods. For a telescope that may have been written off that’s an amazing accomplishment, but it doesn’t just stop there.
As the above diagram shows Kepler has to reorient itself every so often so that light from the sun doesn’t enter the telescope (this would damage its sensors). Not all of these orientations are good for looking for exoplanets however and so Kepler has been put to other uses. Several of the viewing periods have been dedicated to looking at planets within our own solar system, giving us insights into their behaviour like we didn’t have before. It recently spent 70 days observing the weather on Neptune and the motion of its moons, the longest observation of the planet to date. Additionally another observation period is being dedicated to doing a similar investigation on Uranus.
Like I’ve said before second chances with space missions are rare and it’s incredibly heartening to see Kepler producing these kinds of results 2 years after its reaction wheels failed. Whilst these might not be the exact results we’re after they’re still invaluable pieces of data that will help broaden our understanding of both our universe and galactic backyard. I’m sure that we’ll continue to see great things from Kepler and, hopefully, many more exoplanets.
As far as we know right now we’re alone in the universe. However the staggering size of the universe suggests that life should be prevalent elsewhere and we (or they) have the unenviable task of tracking it (or us) down. We’re also not quite sure to look for as whilst we have solid ideas about our kind of life there’s no guarantees that they hold universally true across the galaxy. So when it comes to observing phenomena the last reason researchers should resort to is “aliens did it” as we simply have no way of verifying that was the case. It does make for some interesting speculation however like with the current wave of media hysteria surrounding KIC 8462852, or Tabby’s star as it’s more informally called.
KIC 8462852 was one of 145,000 stars that was being constantly monitored by the Kepler spacecraft, a space telescope that was designed to directly detect exoplanets. Kepler’s planet detection method relies on a planet transiting (I.E. passing in front of) its parent star during its observation period. When the planet does this it ever so slightly drops the brightness of the star and this can give us insights into the planet’s size, orbit and composition. This method has proven to be wildly successful with the number of identified exoplanets increasing significantly thanks to Kepler’s data. KIC 8462852 has proved particularly interesting however as its variation in brightness is way beyond anything we’ve witnessed elsewhere.
Indeed instead of the tiny dips we’re accustomed to seeing, an Earth-like planet around a main sequence star like ours produces a chance of about 84 parts per million, KIC 8462852 has dipped a whopping 15% and 22% on separate occasions. Typically this isn’t particularly interesting, there are many stars with varying output for numerous reasons, however KIC 8462852 is a F-type main sequence star which is very similar to ours (which is a G-type if you’re wondering). These don’t vary wildly in output and the scientists have ruled out issues with equipment and other potential phenomena so what we’re left with is a star with varying output with no great explanation. Whatever is blocking that light has to be huge, at least half the width of the star itself.
There are a few potential candidates to explain this, most notably a cloud of comets on an elliptical orbit that happens to transit our observation path. How that exactly came to be is anyone’s guess, and indeed it would be a rare phenomenon, but it’s looking to be the best explanation we currently have. A massive debris field has currently been ruled out due to a lack of infrared radiation, something which would be present due to the star heating the debris field. This has led to some speculation as to what could cause something like this to happen and some have looked towards intelligent life as the cause.
How could an alien race make a star’s output dip that significantly you ask? Well the theory goes that any sufficiently advanced civilization will eventually require the entire energy output of their star in order to fuel their activities. The only way to do that is to encase the star in a sphere (called a Dyson Sphere) in order to capture all of the energy that it releases. Such a megastructure couldn’t be built instantly however and so to an outside observer the star’s output would likely look weird as the structure was built around it. Thus KIC 8462852, with its wild fluctuations of output, could be in the process of being encased in one such structure for use by another civilization.
Of course such a hypothesis makes numerous leaps that are not supported by any evidence we currently have at our disposal. The research is thankfully focused on finding a more plausible explanation, something which we are capable of finding by engaging in further observations of this particular star. Should all these attempts fail to explain the phenomena, something which I highly doubt will happen, only then should we start toying with the idea that this is the work of some hyper-advanced alien civilization. Whilst the sci-fi nerd me wants to leap at the possibility of a Dyson sphere being built in our backyard I honestly can’t entertain an idea when I know there are so many other plausible options out there.
It is fun to dream, though.
The Kepler Mission is by far one of the most exciting things NASA has done in recent memory. It’s goal was simple, observe a patch of stars continuously for a long period of time in order to detect the planets that orbit them. It’s lone instrument for doing so is a highly sensitive photometer designed to detect the ever so subtle changes in brightness of a parent star when one of its planets transits in front of it. Whilst the chances are low of everything lining up just right so that we can witness such an event the fact that Kepler could monitor some 145,000 stars at once meant that we were almost guaranteed to see a great deal of success.
Indeed we got just that.
The first six weeks of Kepler’s operation proved to be highly successful with 5 planets discovered, albeit ones that would likely be inhospitable due to their close proximity to their parent stars. The years since then have proved to be equally fruitful with Kepler identifying thousands of potential exoplanet candidates with hundreds of them since being confirmed via other methods. These discoveries have reshaped our idea of what our universe looks like with a planetary system like our own now thought to be a relatively common occurrence. Whilst we’re still a long way from finding our home away from home there’s a ton of tantalizing evidence suggesting that such places are numerous with untold numbers of them right in our own galaxy.
However earlier this year Kepler was struck with an insurmountable problem. You see in order to monitor that field of stars precisely Kepler relied on a set of reaction wheels to ensure it was pointed in the right direction at all times. There are a total of 4 of them on board and Kepler only needed 3 of them in order to keep the precision up at the required level. Unfortunately it had previously had one fail forcing the backup wheel to kick into motion. Whilst that had been running fine for a while on May 15th this year another reaction wheel failed and Kepler was unable to maintain its fix on the star field. At the time this was thought to be the end of the mission and, due to the specialized nature of the hardware, likely the end of Kepler’s useful life.
However, thanks to some incredibly clever mechanics, Kepler may rise again.
Whilst there are only 2 functioning reaction wheels NASA scientists have determined that there’s another source of force for them to use. If they orient Kepler in a certain way so that its solar panels are all evenly lit by the sun (the panels wrap around the outer shell of the craft) there’s a constant and reliable force applied to them. In conjunction with the 2 remaining reaction wheels this is enough to aim it, albeit at a different patch of the sky than originally intended. Additionally it won’t be able to keep itself on point consistently like it did previously, needing to reorient itself every 3 months or so which means it will end up studying a different part of the sky.
Whilst this is a massive deviation from its original intended purpose it could potentially breathe a whole new life into the craft, prolonging its life significantly. Considering the numerous discoveries it has already helped us achieve continuing its mission in any way possible is a huge boon to the science community and a testament to NASA’s engineering prowess. We’re still at the initial stages of verifying whether or not this will work as intended but I’m very confident it will, meaning we’ll be enjoying Kepler aided discoveries for a long time to come.
Humanity, for the longest time, has been aware of planets outside the one that we reside on. Ask anyone today about the planets in our solar system and they’re sure to be able to name at least one other planet but ask them about any outside our solar system and you’re sure to draw a blank look. That’s not their fault however as the discovery of planets outside our solar system (which is by definition, not a planet but an exoplanet) is only recent, dating just over 20 years when the first was discovered in 1988. Since then we’ve discovered well over 500 more planets that exist outside our immediate vicinity and whilst their discovery is great none of them have yet been much like the one we currently call home.
In fact the vast majority of the exoplanets that have been discovered have been massive gas giants orbiting their parent stars at the same distance as Mercury orbits from our sun. This threw scientists initially as back then our current theories on solar system formation didn’t support the notion of large planets forming that close to their parent star. However as time we found more and more examples of such planets, these hot gas giants orbiting at velocities the likes we’d never seen before. The reason behind this is simple, the methods we use to find exoplanets are quite adept at finding these planets and not so much those which we’d consider potential homes.
The method by which the vast majority of exoplanets have been discovered is called the Radial Velocity method. As a planet orbits around its parent star the parent star also moves in tandem, tracing out an elliptical path that’s pinned around the common centre of mass between the two heavenly bodies. As the star does this we can observe changes in the star’s radial velocity, the speed at which the star is moving towards or away from this. Using this data we can then infer the minimum mass, distance and speed required to induce such changes in the planet’s radial velocity which will be the exoplanet itself. This method is prone to finding large planets orbiting close to their parent stars because they will cause larger perturbations in the star’s radial orbit more frequently, allowing us to detect them far more easily.
More recently one of the most productive methods of detecting an exoplanet is the Transit method. This method works by continuously measuring a star’s brightness over a long period of time. When an exoplanet crosses in front of its parent relative to us the star’s apparent brightness drops for the time it is in transit. This of course means that this method is limited to detecting planets and stars whose orbits line up in such a way to cause a transit like this. For earth like exoplanets there’s only a 0.47% chance that such planets will line up just right so we can observe them but thankfully this method can be done on tens of thousands of stars at once, ensuring that we discover at least a few in our search. Exoplanets discovered this way usually require verification by another method before they’re confirmed since there are many things that can cause a dip in a star’s apparent brightness.
There are of course numerous other methods to discover planets outside our solar system but for the most part the vast majority of them have been discovered by one of the two methods mentioned above. For both of them they are heavily skewed towards discovering big planets with short transit times as these produce the most observable effects on their parent stars. Still this does not preclude them from finding exoplanets like earth as shown with the recent discovery of Kepler10-b, a small rocky world in torturous conditions:
The planet, called Kepler-10b, is also the first rocky alien planet to be confirmed by NASA’s Kepler mission using data collected between May 2009 and early January 2010. But, while Kepler-10b is a rocky world, it is not located in the so-called habitable zone – a region in a planetary system where liquid water can potentially exist on the planet’s surface.
“Kepler-10b is the smallest exoplanet discovered to date, and the first unquestionably rocky planet orbiting a star outside our solar system,” said Natalie Batalha, Kepler’s deputy science team leader at NASA’s Ames Research Center in Moffett Field, Calif., at a press conference here at the 217th American Astronomy Society meeting.
Kepler-10b is the smallest transitioning planet to be confirmed to date and shows that it’s possible to discover worlds like our own using current technology. As time goes on and the amount of data increases I’m certain that we’ll eventually find more planets like these, hopefully a bit further out so they’ll be in the habitable zone. The Kepler mission is just a few months shy of its 2 year anniversary with at least another 1.5 years to go and if all goes well it should be returning swaths of data for us for the entire time to come.
I’m always fascinated by the latest discoveries in space even when they’re something like a molten mercury 564 light years away. Our technology is becoming more advanced with every passing day and I know that future missions will end up discovering millions of planets at a time with thousands of potentially life supporting worlds. It’s amazing to think that just 3 decades ago we couldn’t be sure that planets existed outside our solar system and today we know for sure there are more than 500 of them out there.
Ain’t science grand?