The latest of some 5,780 exoplanets so far discovered outside our own solar system is described as a "young" planet that may develop into a super-Earth: a world compositionally similar to our own but much larger."Astronomers got lucky," writes Mark Kaufman.
Most exoplanets today are discovered by the "transit method," wherein a telescope watches for slight dips in a star's brightness — caused by a transiting planet. Although the method doesn't work if the star and greater solar system are shrouded in debris, a research team found that the ring of debris in IRAS 04125+2902 b's solar system has become "sharply warped," thus revealing the baby world.
As quoted from a NASA press release, RAS 04125+2902 b "is really just a baby" at 3m years old and the youngest planet discovered using the dominant method of planet detection. Planet Earth is 4.5bn years old.
Here's the paper: A giant planet transiting a 3-Myr protostar with a misaligned disk [Nature]
Astronomers have found more than a dozen planets transiting stars that are 10–40 million years old1, but younger transiting planets have remained elusive. The lack of such discoveries may be because planets have not fully formed at this age or because our view is blocked by the protoplanetary disk. However, we now know that many outer disks are warped or broken2; provided the inner disk is depleted, transiting planets may thus be visible. Here we report observations of the transiting planet IRAS 04125+2902 b orbiting a 3-million-year-old, 0.7-solar-mass, pre-main-sequence star in the Taurus Molecular Cloud. The host star harbours a nearly face-on (30 degrees inclination) transitional disk3 and a wide binary companion. The planet has a period of 8.83 days, a radius of 10.7 Earth radii (0.96 Jupiter radii) and a 95%-confidence upper limit on its mass of 90 Earth masses (0.3 Jupiter masses) from radial-velocity measurements, making it a possible precursor of the super-Earths and sub-Neptunes frequently found around main-sequence stars. The rotational broadening of the star and the orbit of the wide (4 arcseconds, 635 astronomical units) companion are both consistent with edge-on orientations. Thus, all components of the system are consistent with alignment except the outer disk; the origin of this misalignment is unclear.
If you're thinking, "you know, I've always wanted to go on vacation to RAS 04125+2902 b," be warned that it'll likely be inhospitable there for a long time yet—and may end up an ice giant anyway.
Combining TESS's transit measurements with another way of observing planets yields more information about the planet itself. We might call this second approach the "wobble" method. The gravity of a planet tugs its star one way, then another, as the orbiting planet makes its way around the star. And that wobble can be detected by changes in the light from the star, picked up by specialized instruments on Earth. Such "radial velocity" measurements of this planet reveal that its mass, or heft, amounts to no more than about a third of our own Jupiter. But the transit data shows the planet's diameter is about the same. That means the planet has a comparatively low density and, likely, an inflated atmosphere. So this world probably is not a gas giant like Jupiter. Instead, it could well be a planet whose atmosphere will shrink over time. When it finally settles down, it could become a gaseous "mini-Neptune" or even a rocky "super-Earth." These are the two most common planet types in our galaxy – despite the fact that neither type can be found in our solar system.
Previously:
• NASA's 'Eyes on Exoplanets' has hypothetical renderings of those so far discovered
• Watch all the exoplanets orbit their stars simultaneously
• Why the discovery of sulfur dioxide and photochemistry on an exoplanet is a big deal
• Watch: history of exoplanet observations as generative music
• Atmosphere of exoplanet is found to be indicative of an ocean surface… and maybe, possibly life
