An astroid that resembles the Astonishing Legends logo quite a bit is going to be in view in 2018! Although it is relatively small by solar system standards, it's astonishing resemblance to a humanoid skull makes it a big deal. I'm taking it as a sign that this will be our spookiest year ever...but who knows.
Not only does it look like a skull (from some angles at, least) it is also an incredibly dark shade of black. It was last strolling past earth on Halloween 2015 (seriously). It is so dark that its "albedo" (the amount of light it reflects) is equivalent to "a lump of coal." You'd think the symbolism would end there....skull-shaped and dark as night seems like enough. BUT it is also likely a "dead" comet. Comets usually have a tail, however this one does not which means it has likely lost all its ice/gases (which produce the tail) and leave just the rocky core. After so many trips around the sun, it has lost "all its volatile compounds."
Why wasn't it discovered before 2015, though? Well - like I said earlier...it's pretty small. This matched with the fact that it spends a lot of its days beyond mars makes it pretty difficult to discover.
Last time it visited it was thisclose to earth - just outside the moon's orbit (roughly 302,000 miles). However, it is estimated it won't be that close for another 500 years. It also doesn't swing by every year...or even on the same day. "Its orbital period is 1,112 days, or just over three years." The 2018 flyby will take place in early November and it will be quite far - roughly 105x the distance between Earth and the moon.
Sciencealert quotes astrophysicist Pablo Santos-Sanz from the Institute of Astrophysics of Andalusia: "The object measures between 625 metres and 700 metres, its shape is a slightly flattened ellipsoid, and its rotation axis was roughly perpendicular to the Earth at the time of its closest proximity."
Rotation of Asteroid 2015 TB145 on October 30, 3015
This animated GIF of 2015 TB145 was generated using radar data collected by the National Science Foundation's 1,000-foot (305-meter) Arecibo Observatory in Puerto Rico. The six radar images used in the animation were taken on Oct. 30, 2015, and the image resolution is 25 feet (7.5 meters) per pixel.