Possible Alien World Discovered Thanks to Orbiting Debris
The universe is teeming with exoplanets, based on our current (very limited) ability to detect them. Instruments like the brand new James Webb Space Telescope might help us spot more, but maybe we’ve been looking in the wrong place. A study in The Astrophysical Journal Letters details a new method for spotting the youngest planets. According to the study, looking for areas of gravitational equilibrium could point the way to the exoplanets themselves.
The new analysis, led by Feng Long of the Harvard Smithsonian Center for Astrophysics, focused on a young star called LkCa 15 sitting 518 light-years away in the Taurus constellation. LkCa 15 is notable because it has a protoplanetary disk that shows evidence of early planetary formation. There’s still some disagreement as to how that happens, but Long’s research shows that LkCa 15 might have a Neptune-sized exoplanet already locked in.
While the James Webb Space Telescope is adept at peering through the dust and gas around young stars, it wasn’t needed for this analysis. Long turned to data from Chile’s ALMA Observatory collected back in 2019. This radio observatory shows several bright spots in the protoplanetary disk that could be exoplanets. Long identified two faint features that were not previously identified in observations of LkCa 15.
At 42 AU from the star (1 AU is the distance between Earth and the sun), Long spotted two bright blobs of material orbiting within a dusty ring. These blobs were separated along the arc by exactly 120 degrees, and that’s not random. That degree of separation doesn’t just happen — it’s important mathematically,” says Long. These features could be the Lagrange points of the exoplanet, regions of gravitational equilibrium between the planet and its host star.
We have Lagrange points near Earth, and one of them plays host to the Webb Telescope. That point (L2) is relatively close to us, just outside the moon’s orbit, but L4 and L5 are more distant and separated by, you guessed it, 120 degrees. Long suggests we’re seeing the L4 and L5 Lagrange points of a young gas giant in LkCa 15. If confirmed, the planet would probably be just a million or two years old.
It’s difficult to directly image exoplanets, even for the revolutionary Webb Telescope — it’s only done that once so far. However, detecting the Lagrange debris isn’t easy either. It requires “very deep data” due to the faint signal. Long, now a Hubble Fellow at the University of Arizona, believes future observations of LkCa 15 will be able to strengthen the case for this exoplanet, and that could encourage other astronomers to go hunting for Lagrange blobs.
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