265 Years of Planet Discoveries in a 60 Second Gif
Humanity has known of the existence of other planets orbiting our Sun for centuries, but the existence of planets outside our solar system had long been nothing more than a theory. In 1994, Dr. Alexander Wolszczan announced what he called the first "unambiguous proof" of the existence of planets outside of our solar system. Since then, planet hunting technologies like NASA's Kepler space telescope have brought about a massive expansion in our charting of planets outside our solar system. At the time of writing, the total number of confirmed exoplanet detections currently stands at an impressive 1,813 with almost double that awaiting confirmation.
With such huge numbers already in the books, it's easy to forget that before Wolsczan's discovery, we hadn't even been able to comprehensively chart all of the major planetary bodies in our own solar system, let alone confirm the existence of any planets outside it. To help put things in perspective, a new gif from PHD Phsyicist Hugh Osborn shows just how incredible the achievements of the last few years really are.
(Credit: Hugh Osborn)
The planets in dark blue are those found within our own solar systems. The other colors you see refer to the technique used to discover the exoplanets in question. Osborn provided a very simple description on a recent post on Reddit, which you can see below:
Radial Velocity (Light Blue)
Planets orbit thanks to gravitational attraction from their star's mass. But the mass of the planet also has an effect on the star - pulling it around in a tiny circle once every orbit. Astronomers can split the light from a star up into it's colours, which have an atomic barcode of absorption lines in. These lines shift position as the star moves - the light is effectively compressed to bluer colours when moving towards and pulled to longer colours when moving away. So, by measuring this to-and-fro (radial) velocity, and finding periodic signals, astronomers can detect the tug of distant exoplanets.
Direct Imaging (Maroon)
This is easier to get your head around - point a big telescope at a star and directly image a planet around it. This only works for the biggest young planets as these are warmest, so glow brightest in the infra-red (like a red-hot piece of Iron). To find the planet in the glare of it's star, the starlight needs to be suppressed. This is done by either blocking it out with a starshade, or digitally combining the images in such a way to remove the central star, revealing new exoplanets.
Einstein's general theory of relativity shows that mass bends space time. This means that light can be bent by massive objects, and even act like a lens. Occasionally a star with a planetary system passes in front of a distant star. The light from the distant star is bent and lensed by both the star and the planet, giving two sharp increases in brightness over a few days - one for the star and one for the planet. The amount of lensing gives the mass of the planets, and the time between the events gives us the distance from their star.
When a planet crosses in front of it's star, it blocks out a small portion of sunlight depending on it's size. We only see the star as a single point, but we can infer the presence of a planet from the dip in light. When this repeats, we get a period. This is how we have found more than 1000 of the current crop of ~1800 exoplanets!
The only problem with making a graphic like this is that the exoplanet discoveries are coming in so thick and fast, any catalogue of them can very easily find itself out of date before you know it!
For more information on the graphic visit Hugh Osborn's website.