Category Archives: FAQs

Frequently Asked Questions.

For anyone wondering, in the most basic terms, what it means to find new planets and how we are able to do it, here’s a short blog I put together based on what people seem to want to know…

So what do you do?

I use telescopes to hunt for planets around other stars.

How does that work? Do you just find new dots of light in the sky?

Kepler-62f_with_62e_as_Morning_StarStars are really bright. The Sun, for instance, shines tens of billions of times brighter than any of the planets. Not only that, but the stars we see in the night sky are also incredibly far away. Imagine holding the Earth and the Sun within your palm. (By the way, the Earth in this scenario is the size of a human red blood cell). On that scale, Mars is just beyond your wrist and Saturn is by your elbow. The nearest star, however, is still more than 7km away! And what we want to do is spot a fleck of dust around that. It is as impossible as it sounds – even with the best telescope on Earth, we can’t spot planets directly in this way.

So how do you know if a planet is there?

While we may not be able to spot the planet’s light directly, there are hints in the starlight itself.

Orbit3

Everything that has mass has a gravitational pull; and while most people know that the mass of the Sun keeps the Earth in orbit around it, few people know that the Sun is also in motion around the Earth. That orbit is a tiny circle: only 450km in radius compared to the 150million km orbit the Earth follows once a year. Larger planets like Jupiter cause correspondingly larger effects. So, by detecting the motion of a star, we can figure out how big a planet is, and how far away from the star it must be.

This was how the first planets were found 20 years ago; by splitting starlight into its colours and using tiny shifts in the ‘barcode’ of elements to determine the motion of the star. It’s also how the new Gaia satellite will hopefully find tens of thousands of new planets, by precisely measuring their locations and spotting these tiny wobbles.

eso_planet

Another method is to hunt for the rare occasions when planets pass in front of their stars, like the moon during an eclipse. However, even the largest planets only block less than 1% of the starlight during these transits. So to find planets this way we not only need telescopes that can look at thousands of stars at a time, they also need to be really accurate at measuring the star’s brightness. This is something we have been able to do from the ground, with surveys like WASP and HAT, and from space with telescopes like Kepler.

So which method do you use?

I hunt for planets using the transit method. At the moment I am trying to find long-distance Jupiter-sized planets using the WASP survey. This uses 16 relatively small cameras in South Africa and Chile to follow the brightness of millions of stars. So far we’ve found over 100 planets this way, with dozens more in the pipeline.

How many have you personally found?

Finding planets really is a team game. I have helped out at every stage from identifying the first signs of planet transits, to following up transits with better telescopes to check they’re real. So, depending on how you count, somewhere between zero and half a dozen.

Do you get to name them?

Nope :(. Any planets we find get named after the telescopes, eg WASP-134b. Not exactly the most captivating names, I know!

Have we found any planets like Earth?

EarthMoonSmaller planets, especially ones far away from their star, are a lot more difficult to detect. To detect such planets using the radial motion of a star requires measuring the star’s velocity to better than 10cm/s. That’s slower than your average tortoise! Remarkably, there are some instruments being built that could do it.

As for the transit method, Earths crossing their star dim the light about 0.008%. That’s about the same as watching for a piece of dust crossing in front of a lightbulb. But, remarkably, we can do it! The Kepler space telescope was able to monitor the brightness of more than 100,000 stars down to a few parts per million. And it found dozens of Earth-sized worlds that look very similar to our own.

Will there be Aliens on them?

Maybe. Thanks to missions like Kepler, we now know that there are hundreds of billions of planets like the Earth in our galaxy. And we know that life sprung into existence on at least one of them. So there’s no reason to think it wouldn’t have done so elsewhere else too.

Whether intelligent life is common is another question – we’ve been looking for decades and found absolutely no evidence. My own feeling is that, while simple microbes might be common in the universe, technologically advanced life probably isn’t. It took 4 billion years and a handful of chance events for intelligence to evolve at all. And the way our species is going, surviving even for a few thousand years more (~0.0001% the lifetime of the planet) seems unlikely.

Please feel free to ask any more questions in the comments! I will add some if and when I think of them.

What’s In A Name?

Hundreds of astronomers across the globe are currently searching nearby stars for a fleeting glimpse of astronomical gold dust: exoplanets. I am also part of the search, scanning through terabytes of data taken by the WASP and NGTS telescopes looking for the distinctive signal of a distant world crossing its star. Thanks to the mountains of data from NASA’s Kepler probe, it is now even possible for amateurs to go online and help out. And thousands of people have taken part, spurred on by the chance to become the first person in history to lay eyes on a new part of the universe.

It is a thrilling quest, but the question on everyone’s lips is this: do you get to name it? Surprisingly enough, the answer is a ‘No’. Or maybe a ‘Not yet’…

Cookie

Here on Earth it has long been custom that, for whatever it may be, the discoverer becomes the namer. Columbus, Cook and Magellan all took pleasure in naming new lands, doctors such as Alzheimer or Asperger gave their names to their respective disorders, even some recently named animal species include Attenborosaurus conybeari and Heteropoda davidbowie in honour of the researcher’s heros. Chemists discovering new elements are given a relative freedom over naming their discoveries. Even in astronomy, comets are named after their discoverer with names such as Lovejoy or McNaught often gracing comet codes. Exoplanets, on the other hand, are a very different kettle of fish.

The problem with naming planets comes from the stars they circle. As nice as it would be to name every object something eye-catching like ‘Permadeath’ or ‘Baallderaan’, to avoid confusion the name of the star must be listed first. This is much like the way biological names come with both genus (Homo) and species (sapiens). So how do we end up with names like HD80606b whereas biologists get Bushiella beatlesi? The first part comes down to how we name stars.

Too Many stars to Count

Unlike islands or animals, there exist a near infinite plethora of stars. Our galaxy alone has more than 100 billion. Attempt to name each in the Linnaean style and you would quickly run out of words (and sanity). Early sky-watchers soon realised this and, after giving a few hundred stars colloquial names such as Vega or Pollux, settled for simply numbering the stars by brightness in a certain area. This ‘Bayer’ designation, cooked up in 1603, ranked the stars from alpha down to omega and beyond. For example the brightest in the Centaurus constellation is Alpha Centauri, our Sun’s nearest neighbour. With limited telescopic power and Greek and Latin characters, Bayer gave up after about 1500 stars.

More recent surveys have used telescopes to attempt to sweep the rest of the sky into some sort of order. This has resolutely failed, with the majority of stars having numerous names under many different catalogues (HD, HR, Gliese, or HIP to name but a few). Each of these official catalogues simply orders the stars by number, giving rise to the cumbersome alphanumeric system we see today. {NB: Despite what some might insist, naming a star has never been done via gift subscription companies}. So, thanks to the sheer number of star systems, the sky is a mess and there would seem little hope of sorting it out. 

GJ581 Planets

But forgetting the star for a second, once a planet is found we do get to add a ‘species name’ to the stars, right? Dont get your hopes up: this is normally the lower-case letter b. The lower case shows it to be a planet (as opposed to ‘B’ which would designate another star) and the ‘b’ designates it as the second object in the system after the star itself. In multi-planet systems things get even more confusing, with the order of names increasing not outwards from the star but simply in order of which was discovered first. For example GJ581e circles within the orbit of ‘b’ and GJ 581g is sandwiched between ‘c’ and ‘d’. However, this fundamentally makes sense: planets in the same solar system are given names reflecting their sibling nature.

It may be a dysfunctional system that results in far-from eye-catching names, but it is one at least partly grounded in reason. The alternative, of letting discoverers name the planet whatever they want (my personal choice would be Hughtopia), would ultimately end in confusion and a lot more angry shouting matches at conferences.

Even worse, a whole host of recent crowd-sourced websites have sprung up attempting to get the general public to name the 100-strong list of current exoplanets (for money, of course).  The International Astronomical Union (IAU), who ultimately decide on the names of everything in space, have even given support to public-generated naming systems. The feeling among astronomers, though, is that such a move might not be such a good idea.

But is there a middle way? Could the ordered nomenclature remain intact while giving at least some naming rights to the discoverers? The Planetary Habitability Laboratory recently proposed a system that would retain the star name but allow free reign over the planetary name, for example allowing Alpha Centauri B b to become Alcen-B Rakhat. It is an intriguing idea, and one that could help improve the public perception of astronomy. I, for one, am still hopeful that ‘Betelgeuse Hughtopia’ can become a reality.

[Relevant XKCD:]

relevantxkcd