Earth-sized in mass, maybe, but earth-like?<p>They argue there may be a ∼ 1.5–3 M⊕ object out there, but don’t say anything about its size or surface temperature.<p>At ∼ 200–500 au, chances are it would be mostly ice. (<a href="https://en.wikipedia.org/wiki/Kuiper_belt" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Kuiper_belt</a>: <i>“most Kuiper belt objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia, and water”</i>)<p><a href="https://en.m.wikipedia.org/wiki/Kuiper_belt#Composition" rel="nofollow noreferrer">https://en.m.wikipedia.org/wiki/Kuiper_belt#Composition</a>: <i>“The temperature of the belt is only about 50 K”</i><p><i>“The densities range from less than 0.4 to 2.6 g/cm³”</i><p>⇒ a bit heavier and likely way less dense than earth (at 5.5 g/cm³, the densest object in the solar system. See <a href="https://www.forbes.com/sites/startswithabang/2020/03/31/this-is-why-earth-surprisingly-is-the-densest-object-in-our-solar-system/?sh=1712f0617be6" rel="nofollow noreferrer">https://www.forbes.com/sites/startswithabang/2020/03/31/this...</a>), so likely at least double its diameter, and very cold, so not earth-like.<p>That title is click-bait.