Looking for exomoons – moons the orbit round one other planet – was one of the crucial thrilling capabilities anticipated of the James Webb House Telescope (JWST) when it launched in late 2021. So, after 4 years of operation, why hasn’t it discovered one but? Seems it’s actually, actually laborious to discover a moon round a planet light-years away. A brand new paper accessible in pre-print on arXiv from David Kipping of Columbia College (and Cool Worlds YouTube Channel fame) exhibits why. They used 60 hours of time on JWST’s NIRSpec instrument and weren’t capable of definitively affirm the existence of a attainable exomoon.
That has not been for lack of attempting. JWST has discovered two potential exomoon candidates, however neither has but been confirmed. WASP-39b is a “sizzling Saturn” that confirmed numerous variability in its sodium and sulfur dioxide ranges, which led the researchers taking a look at it to posit that a particularly volcanic tidally heated exomoon is spewing gasoline onto the planet. Whereas believable, its positively primarily based on oblique proof at finest. One other discovering about W1935, as brown dwarf, is equally primarily based on oblique proof. On this case, it has some unexplained methane emissions that may very well be attributable to an undiscovered exomoon – however but once more it has but to be immediately noticed.
That brings us to Kepler-167e, the main focus of the latest paper by Dr. Kipping and his co-authors. This planet appeared excellent to seek for a moon, because it’s one of many closest Jupiter analogues we’ve but discovered. It’s about .91 occasions the mass of Jupiter, with an orbit of about 1.88 AU, which is in between Mars and Jupiter, round a star that’s round 1,119 mild years away within the constellation Cygnus. Provided that Jupiter itself has upwards of 70 moons, together with Ganymede, the biggest moon in our photo voltaic system, it appears doubtless that an exoplanet so just like it could have some as effectively. The system additionally holds three different “Tremendous-Earth” exoplanets, which needed to be accounted for as confounding components within the mild curves JWST was creating.
Dr, David Kipping, the lead creator on the paper, describes how the search occurred. Credit score – Cool Worlds YouTube Channel
To create these mild curves, the authors acquired 60 hours of observational time on JWST – an absurd quantity when contemplating what number of calls for on its time JWST has. These observational blocks had been damaged into six separate 10 hour segments, with a brief break in between every. One factor the authors famous was that, over the ten hour observational window, the depth of the sunshine curves they had been taking a look at would steadily lower. They chalked it as much as “detector results”, however famous that it occurred on an analogous time-scale to the impact an exomoon would have on the sunshine of its planet, making it tough to differentiate between an exomoon transit and a detector artifact.
Regardless of the struggles with the detector, the authors did their finest to get rid of any bias it may need precipitated, and ran the information JWST collected via a number of “pipelines” as they’re known as in astronomy jargon. One was customized constructed only for this observational run, whereas two extra, often called ExoTiC-JEDI and katahdin, had been beforehand developed. As soon as the information was run via the pipelines, it was in contrast towards one among 4 separate fashions, ranging in complexity between a easy quadratic match to a Gaussian course of with a Matérn-3/2 kernel – anybody eager about studying what meaning can sit up for numerous sign processing math.
Of the twelve completely different attainable mixtures of data-pipeline and mannequin, seven truly confirmed a attainable exomoon within the JWST knowledge. However astronomy is rarely that simple – different explanations should be dominated out to make sure the sign is actual. On this case, the authors famous that there was one other clarification that would have precipitated the information to match so effectively with what’s known as a syzygy-like occasion – the place an exomoon, planet, and star are all aligned. By their reckoning, it regarded just like the moon, planet, and star had been lined up, however in reality it was simply the planet passing over a sunspot.
Fraser interviews Dr. Kipping concerning the seek for exomoons.
Kepler-167 is understood to be comparatively quiet – or “quiescent” in astronomy jargon. However, earlier research of it from Kepler and Spitzer indicated that it was attainable that it creates spots which can be giant sufficient to account for the dip in lightcurve seen within the JWST knowledge. Additionally, when the authors tried to calculate the dimensions of the moon they’d discovered, they calculated that it must be 30% larger than the fashions urged could be attainable so as to account for the dip in mild.
Given these two components, they concluded {that a} sunspot was the almost certainly clarification for his or her findings. Whereas it may be laborious to confess that, after spending a lot effort and time to get all that observational time on probably the most sought-after telescope on this planet, the authors determined they got here up empty-handed. However that’s how the scientific course of goes – typically a destructive result’s what you get.
However that gained’t cease them from attempting once more. They’re suggesting one other observational marketing campaign when Kepler-167e transits once more in October 2027. That’s nonetheless a couple of observational cycles from now for JWST, so it’s unclear whether or not they’ll be granted the extra time. However even when they aren’t, there are many different devoted exomoon observational packages within the present and deliberate cycles over the following few years. If these elusive worlds do exist, it is doubtless solely a matter of time earlier than we discover one – and this new paper supplies a roadmap to the sort of intense knowledge processing, mannequin becoming, and in some circumstances soul looking out, required to be sure that, once we do, we all know its actual.
Be taught Extra:
D. Kipping et al – A JWST Transit of a Jupiter Analog: II. A Search for Exomoons
UT – Tentative Exomoon Sign in HD 206893 B
UT – The Seek for Exomoons is On
UT – These are the Greatest Locations to Seek for Liveable Exomoons
