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Original: BEN Skuse
Translator: Mou Xinxiang
Proofreader: Zhou Yufeng Zhou Xueyun
Arrangement: Li Ziqi
Backstage: Kutlia Fuka Li Ziqi Dong Tengchen Hu Yongwei
Original link: https://skyandtelescope.org/astronomy-news/needle-in-the-haystack-new-exomoon-candidate-found/
The discovery of a second suspected exoplanet suggests that exomoons may be as common as exoplanets
Although a large number of exoplanets have been discovered since the 1990s, astronomers have not been able to determine the existence of any exoplanets. In fact, so far, only about a dozen possible candidates have been found in total.
In 2018, David Kipping of Columbia University and Alex Teachey of The Academia Sinica in Taiwan first proposed that the exoplanet Kepler-1625b, 7,800 light-years away from Earth, might have a Neptune-sized moon: Kepler-1625 b-i. Now, astronomers and other staff announced the discovery of another exoplanet on January 14 in Nature Astronomy. Of course, as always, they hoped that the parties would not make premature conclusions and would need to be supported by sufficient observational evidence.
The exoplanet Kepler-1625b and its moon Kepler-1625 b-i are simultaneously transiting
Image source: Dan Durda
The exoplanet candidate, named Kepler-1708 b-i, orbits a planet about the size of Jupiter 5,700 light-years away, which orbits a Sun-like star in a Mars-like orbit with an orbital radius of 1.6 AU. Its moons are about 12 planetary radii, similar to Europa and Jupiter. But unlike Europa, Kepler-1708 b-i is huge, 2.5 times larger than Earth, unlike any satellite in the solar system.
Compared to Jupiter, Europa is really too small
Image source: Network
"I'm not sure what it actually constructs," Kipping said. "It could just be a cloud of gas, an ocean, or a rocky planet wrapped in hydrogen — we don't know yet."
Kipping and his colleagues' discovery began a few years ago with a Kepler space telescope's observation of 284 relatively close planets. At that time, it had only discovered one object suspected of being an exoplanet (Kepler-1625b-i), which led him to wonder: Are larger moons more likely to appear around planets farther away from the host star?
Kepler Space Telescope
To test this idea, astronomers began investigating cryogenic gas giants in Kepler's archives. After weeding out the inappropriate and poor-mass data, all that remains are the 70 planets that Kepler observed at least twice. They then looked in more detail at the luminosity decline curves that planets produce as they pass across the star's surface, retaining only those parts that better fit the curves of planets with satellites.
Only three planets passed the test, but more careful scrutiny further screened out the few remaining candidate planets. "One of them we're pretty sure was two points of star that caused the change in the shape of the light, which looks like it was caused by a single satellite," Kipping explains. "Another rejection is because we think it was actually a misjudgment by the instrument."
In the end, only the Kepler-1708 b-i was left unseen.
As a final check, the team made a virtual signal that matched only the host planet and randomly incorporated it into the Kepler data of the host star to test how often they found the errors of the non-existent exoplanets. The result was that the data incorrectly reflected the presence of exosates in two of the 200.
That said, "there's a 1% chance that this finding is just a random error in the data that fooled us," Kipping explains. "That's a big number, but it's not small." To confirm Kepler-1708 b-i's status as an exoplanet, Kipping acknowledges the need for additional observational evidence.
"This analysis is great, but even so, it's still just a suspected exoplanet," said Mary Anne Limbach of Texas A&M University, who was not involved in the study.
Laura Kreidberg of the Max Planck Astronomical Institute in Germany, who conducted a follow-up study and questioned the previous Kepler-1625 b-i, showed that Kepler-1708 b-i is one of the most promising candidates found so far, but still needs more data to support it: "We need another transit observation, which will show two drops in brightness: one when the planet blocks the star's light, and the other when the moon blocks the light." ”
However, such observations may not be possible in the short term. The Kepler telescope was retired in 2018, and the instrument most capable of making this measurement at the moment — the recently launched James Webb Space Telescope — has been heavily overbooked for observations. In addition, Kepler-1708 b-i's 737-day orbital period means it won't be over the stars again in 2022.
Looking to the future, the prospects are brighter. Kipping is using more advanced techniques to sift through data from the Kepler telescope to discover more exomoons. He also plans to use data from the Hubble Space Telescope or the James Webb Space Telescope to look for small exolinks the size of Europa or Ganymede.
Limbach said: "In the next decade, several telescopes sensitive enough to detect exosolats will be online. "The list includes the Nancy Grace Roman Space Telescope and a new class of ground-based observatories – the European Extremely Large Telescope, the Giant Magellan Telescope and the 30-meter telescope." I think this could accelerate the development of this area in a number of ways and could lead us to really identify the first exosolate in the next decade. ”
Editor-in-Charge: Zhou Xueyun
Pastoral New Media Editorial Department
"Astronomical Wet Engraving" produced by Shepherd
Moonrise on the Fuchun River.
The moon is reddish when it is just rising and about to set because the Rayleigh scattering caused by particles in the atmosphere scatters a large amount of shorter wavelengths of blue-green light. The lower the moon, the longer the path through which the moonlight passes, and the stronger the scattering. This is the same principle as the red color of the setting sun. PS: When the moon first emerged from the mountain, there were still friends who thought that the mountain was on fire
Source: Sea otters are not otters