The TRAPPIST-1 system is the most tempting in our local galactic neighborhood. It is only 40 light years away, with seven rocky exoplanets, three of which are in the habitable zone of its star. But it takes more than that to create a truly habitable world, so astronomers have been looking for features that can tell us more about the history of the system.
Now, impressive new research has shown that just like the planets in the solar system orbit in a more or less flat plane around the Sun's equator, much like a vinyl record, the exoplanets TRAPPIST-1 also orbit in a flat plane around is the middle
This discovery will allow astronomers to study the dynamic history of the system, which can help us refine the models of the system and exclude habitability on one of its exoplanets. But finding the planets around the star's equator means that they are essentially orbiting at the same inclination that they formed, which makes the study of the study. 39; easier state of the system.
To date, astronomers have discovered more than 4,000 exoplanets in the Milky Way galaxy, and one of the very important things they can show us is the normality (or not) of the solar system.
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Astronomers have taken measurements of the orbital alignment of some exoplanets, and many gas giants in close orbit what is called stellar obliquity, when the exoplanets of a star orbit at an oblique angle to the axis of rotation of the star.
Multiple planet systems tend to be less oblique – but nobody had measured it before with rocky worlds, like the Earth. Indeed, stellar asymmetry is measured based on something called the Rossiter-McLaughlin effect, which is difficult to observe with small, weak stars like TRAPPIST-1.
This is how it works. When we observe a star in orbit, the light from the side which turns towards us will be compressed at higher frequencies towards the blue end of the spectrum. We call it a blueshift. Light from the side that is moving away from us, however, propagates to lower frequencies or turns red.
When a planet moves around this star, you can tell which direction it is moving depending on the type of wavelength that is blocked first. And the exoplanet projects a traveling Doppler shadow that creates distortion that can be used to directly model the stellar tilt.
TRAPPIST-1 is a red dwarf, which means that it is very small and weak, which makes the Rossiter-McLaughlin effect previously impossible to observe. But the Subaru telescope located in Hawaii was recently equipped with the infrared Doppler (IRD), a new infrared spectrograph with a resolution high enough to distinguish it.
Then, by chance, on the night of August 31, 2018, three of the TRAPPIST-1 exoplanets transited the star in a single night, allowing the team to collect a large amount of data in a single race. Observation. And they were lucky. Only one of the transits produced a reliable Doppler shadow, but suggested that the stellar asymmetry was close to zero.
This is not yet conclusive: there was a fairly large margin of error, which means that the orbital misalignment could not be completely excluded. But this suggests some interesting possibilities for the TRAPPIST-1 system.
During star formation, a star is surrounded by a large, flat disk of dust and gas that coils around it. When the star is finished, the rest of the dust and gas is what forms everything else. This is why the planets of the solar system are so well ordered, instead of swinging in all directions: nothing seemed to disturb their alignment, so they just stayed.
If the TRAPPIST-1 exoplanets are on an ordered equatorial plane, then they probably stayed where they also formed. However, the planets are grouped fairly close to their star; This means that this compact arrangement was probably the result of a gradual inward migration, rather than any other disruptive factor.
It could also mean that the absence of large gravitational disturbances is more likely to cause planets to be in peaceful, habitable areas, although, of course, reaching this conclusion would require much more consideration.
But for now, the team work is an impressive step forward.
"Despite the data limitations, our observation of Doppler transits in the TRAPPIST-1 system is the first of these observations, to our knowledge, for a star of such low mass." they wrote on their paper
"No other results have been reported for stars below 3500 K. By making additional observations with IRD and other new high-resolution infrared spectrographs, a new window will open. will open up in planetary systems orbital architectures around low mass stars. " "
The research was published in Letters from the astrophysical journal.