Eris, located far away, really far away. That’s why it was very difficult for us to notice it. But its discovery changed completely our perception of our solar systems. On July 2005, during the observations of the Hubble Space telescope, a planet located 15 billion kilometers away from the earth was determined. The same year we discovered that it had a satellite. And we gave the names Eris and Dysnomia coming from the Greek Mythology to these 2 celestial bodies. NASA and some media members were defining Eris as the 10th planet of the solar system when it was discovered.
In 2006, the International Astronomy Association had excluded Pluto from the planet’s list. At that time Eris was discovered and they both were evaluated same way. In fact the discovered of Eris was very unfortunate for Pluto. Because the discovery of Eris dethroned Pluto. Pluto was discovered in 1930 but it took very long to discover Eris.
This celestial body has an unusual orbit. It takes the dwarf planet Eris almost 577 years to orbit the sun. Sometimes it goes very distant from us, and sometimes it can become closer than Pluto. Yet, this change in distance is not the only reason of the delay of its discovery. The orbit of Eris has a 44 degree inclination compared to the plane of planets.
For a long time, astronomers didn’t feel the need to study these parts of the solar system. It’s an object that stands very far and that doesn’t give off light. As you know, you have to make ultraviolet observations to be able to see these. And this technology is begun developing after 80’s to be exact. And as we also mentioned the inclination of its orbit, the fact that it doesn’t turn on the same plane as the others, is one of the reasons why we’ve missed it.
After the discovery of Eris, the studies gain momentum. First, it’s mass and volume had to be calculated. In 2010, with a special experiment the dimensions of this celestial body were determined. The main purpose of the experiment was to observe the projection of Eris. If an object entered between earth and a planet located far far away a projection that perfectly matches to this object had to be formed on the earth.
It’s not possible for a single planet to form a shadow as you are seeing in this animation on a universe where billions of planets were located, yet this situation presents another possibility for astronomers. If there is a star at the background and if Eris crosses in front of this star located at the background by forming an eclipse, we can determine the diameter of Eris by looking the time of this crossing. That means we can guess, we can calculate its dimensions.
In fact, what we do in here is a very simple but clever geometrical calculation. The researches of the observatories of San Pedro and La Silla located in Chile and of El Leoncito located Argentina observed for how long that the chosen star was disappeared from the sight regarding their observation points of view while Eris’s crossing in front of it and accordingly determined 4 different points. If the 4 points of a circle is determined that means you can easily draw the circle.
This experiment proved that Eris was just as big as Pluto with its approximately 2,300km. diameter. The fact that we’ve just discovered Eris that stands right under our very nose with respect to the greatness of the universe prove that we are only at the beginning of the road.