What is a heavenly body that is sometimes visible without a telescope and has a large elliptical orbit around the sun?

A heavenly body that is sometimes visible without a telescope and has a large elliptical orbit around the sun is indeed a comet. Comets are composed of ice, dust, and rocky materials, and they typically originate from regions such as the Kuiper Belt or the Oort Cloud. When they approach the sun, they heat up and release gases and dust, forming a glowing coma and often a visible tail, which can make them bright enough to be seen from Earth with the naked eye.

The key aspect of their orbit is that comets follow highly elliptical paths around the sun, which differentiates them from other types of celestial bodies. While asteroids and planets also orbit the sun, their orbits are generally more circular. Meteorites, on the other hand, are remnants of meteoroids that survive their passage through the Earth's atmosphere; they do not have orbits around the sun themselves and are usually not visible without a telescope before entering the atmosphere. Thus, the characteristics of visibility and orbit described in the question align perfectly with what we know about comets.