Exomoon or No Exomoon? – Sky & Telescope

July 4, 2019 - Comment

Final October, the primary discovery of a possible exomoon was introduced. However is Kepler-1625b-i an precise moon in one other photo voltaic system? Or simply an artifact of knowledge discount? Artist’s impression of the exomoon candidate Kepler-1625b-i and its host planet and star. NASA / ESA / L. Hustak (STScI) A Difficult Enterprise Artist’s depiction


Final October, the primary discovery of a possible exomoon was introduced. However is Kepler-1625b-i an precise moon in one other photo voltaic system? Or simply an artifact of knowledge discount?

Exomoon (art)

Artist’s impression of the exomoon candidate Kepler-1625b-i and its host planet and star.
NASA / ESA / L. Hustak (STScI)

A Difficult Enterprise

Exomoon (art)

Artist’s depiction of an Earth-like exomoon orbiting a gas-giant planet.
NASA / JPL-Caltech

Moons are a helpful diagnostic — they’ll present all types of details about their host planets, like clues to formation historical past, evolution, and even whether or not the planet may be liveable. What’s extra, exomoons themselves have been indicated as potential targets within the seek for life: whereas a habitable-zone gas-giant planet may not be a really perfect host, for instance, such a planet might have moons which might be.

Given all we stand to study from exomoons, it’d be nice to seek out some! However for all that our photo voltaic system is chock filled with moons (eventually depend, Jupiter alone hosts 79!), we’ve but to seek out any signal of exomoons orbiting planets past the photo voltaic system.

Jupiter family portrait

A montage of Jupiter and its 4 largest moons.
NASA / JPL

This might be as a result of exomoon indicators are tough to identify. Not solely would an exomoon’s sign be tiny in comparison with that of its host planet, however we additionally would want to separate that sign from the host’s — a difficult enterprise. Throw in some instrument systematics to obscure all the information, and exomoon identification turns into much more of a problem.

For these causes, it was a fairly thrilling announcement final fall when Columbia College astronomers Alex Teachey and David Kipping offered Kepler-1625b-i, a sign that they argued represented an exomoon across the fuel big Kepler-1625b. However a wholesome dose of scientific warning has despatched different groups scrambling to discover these knowledge and draw their very own conclusions — and certainly one of these teams is asking the exomoon discovery into query.

Ready for Consensus

Kepler 1625 lightcurve

Finest-fit fashions for the Kepler 1625 mild curve assuming a planet and no moon (prime) or moon (backside). Knowledge as analyzed by Kreidberg et al. are on the left (blue); knowledge as analyzed by Teachey&Kipping are on the appropriate (purple). Kreidberg et al. discover that the most effective match is given by the no-moon mannequin. Click on to enlarge.
Kreidberg et al. 2019

Led by Laura Kreidberg (Harvard-Smithsonian Middle for Astrophysics), a workforce of astronomers has independently analyzed the identical Hubble transit knowledge that Teachey and Kipping used to establish their exomoon candidate. Not like the opposite group, nevertheless, Kreidberg and collaborators discovered that the information are greatest match by a easy planet transit mannequin — the presence of an exomoon isn’t essential or indicated.

In response to Kreidberg and collaborators, the discrepancy between their outcomes and Teachey and Kipping’s is most certainly as a consequence of variations in knowledge discount. Teachey and Kipping have responded to this work with extra evaluation in a current paper submitted to AAS journals, however the debate is way from settled.

So is there an exomoon, or isn’t there? We don’t know but, however that’s okay!

The case of Kepler 1625 is a fantastic illustration of the messy actuality of the scientific course of: typically the information don’t instantly spell out a solution, and it takes extra time, extra evaluation, and sure extra observations earlier than the scientific neighborhood reaches a consensus. This isn’t a nasty factor, although — that is science being achieved proper! Keep watch over the story of Kepler 1625b-i going ahead; we’re certain to proceed to find out about this perhaps/maybe-not exomoon.

Quotation

“No Proof for Lunar Transit in New Evaluation of Hubble House Telescope Observations of the Kepler-1625 System,” Laura Kreidberg et al 2019 ApJL 877 L15. doi:10.3847/2041-8213/ab20c8

This submit initially appeared on AAS Nova, which options analysis highlights from the journals of the American Astronomical Society.



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