Searching for debris surrounding other worlds might lead to their discovery


Artist's illustration of a small Saturn-like planet discovered in the system LkCa 15. The planet resides within dense rings of dust and gas that surround a bright yellow star. (Image credit: M.Weiss/Center for Astrophysics/Harvard & Smithsonian)
Artist's illustration of a small Saturn-like planet discovered in the system LkCa 15. The planet resides within dense rings of dust and gas that surround a bright yellow star. (Image credit: M.Weiss/Center for Astrophysics/Harvard & Smithsonian)

We don't typically get fortunate when looking for freshly formed planets that are tens, hundreds, or thousands of light years distant. Planets develop in protoplanetary disks, which are dense clouds of dust and gas that whirl around a star. As a result, seeing young planets directly through all the junk is extremely challenging. Scientists must instead depend on circumstantial evidence to infer the existence of a protoplanet. However, Feng Long, a postdoctoral scholar at the Center for Astrophysics at Harvard and the Smithsonian Institution has identified a fresh indication that may suggest the existence of a protoplanet: material near the Lagrange points.


Long described the protoplanetary disk LkCa 15, situated 518 light years distant, as a dusty ring with two distinct and brilliant clusters of material circling inside it, while combing through data from Chile's ALMA Observatory.


One of the groupings formed an arc, while the other clumped together.


She stated that this arc and cluster are separated by around 120 degrees. That degree of separation does not just happen; it is mathematically significant.

That angle implies that the two material clusters are placed at two Lagrange points. When two celestial bodies, such as a star and a planet, are gravitationally linked, there are five places in space where their gravity and orbital motion practically cancel each other out. The material stays stationary at these Lagrange points, which are labeled L1 through L5, virtually locked in space. Long believes the material clusters are at L4 and L5, with a planet at 60 degrees between them, based on the 120-degree angle detected between them.


According to Long, we can observe that this substance is stable and has a preference for where it wants to be positioned based on physics and the items involved.


Long believes that more observations of LkCa 15 from ALMA might give additional evidence to back her idea, but current astronomical technology prevents her from doing so. Long expects that others will apply her approach of scanning for debris at Lagrange points to locate other probable protoplanets in the meantime.


She expressed her hope that this strategy will be widely utilized in the future.


Long's findings were published this week in The Astrophysical Journal Letters.

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