Despite an explosion of exoplanet discoveries since the 1990s, astronomers have not confirmed the discovery of a single exomoon. In fact, only around a dozen exomoon candidates have been put forward up to now.
In 2018, David Kipping (Columbia University) and Alex Teachey (now at Academia Sinica, Taiwan) were the first, tentatively reporting a possible Neptune-radius moon about 7,800 light-years from Earth: Kepler-1625 b-i. Now, the astronomers and other colleagues have announced the discovery of another exomoon, published January 14th in Nature Astronomy. However, just as before, they urge both caution and the need for further observations.
The putative exomoon, designated Kepler-1708 b-i, was found 5,700 light-years away, orbiting a Jupiter-size planet around a star similar to the Sun. The planet is on a Mars-like orbit, at about 1.6 astronomical units (a.u.). Its moon orbits about 12 planetary radii away, similar to Europa's distance from Jupiter. Unlike Europa, though, Kepler-1708 b-i is huge, about 2.5 times Earth's size. This means the moon would be unlike any satellite in our solar system.
Journal Reference:
David Kipping, Steve Bryson, Chris Burke, et al. An exomoon survey of 70 cool giant exoplanets and the new candidate Kepler-1708 b-i [open], Nature Astronomy (DOI: 10.1038/s41550-021-01539-1)
Yet another observation to add onto JWST's schedule.
Also at Scientific American.
Previously: First Exo-Moon Discovered?
First Known Exomoon May Have Been Detected: Kepler 1625b i
New Evidence Supports Existence of Neptune-Sized Exomoon Orbiting Kepler-1625b
Exomoon Confirmation Remains Elusive
Related Stories
New Scientist, on authority of NASA's Jet Propulsion Laboratory, reports that the first moon outside of our solar system may have been discovered.
It is not yet clear what double object MOA-2011-BLG-262 is: it may be a rogue planet with a massive moon about 1800 light years from Earth, or a faint star (brown or red dwarf) with a Neptune-sized planet much further away.
The discovery was made by telescopes in New Zealand and Tasmania during a micro-lensing event in 2011. Since the micro-lensing event is over and we don't know the distance of the double object, we can not distinguish between both possibilities.
(The discovery was published late 2013, but it is making mainstream news now.)
The first satellite orbiting an exoplanet may have been discovered:
A team of astronomers has potentially discovered the first known moon beyond the Solar System. If confirmed, the "exomoon" is likely to be about the size and mass of Neptune, and circles a planet the size of Jupiter but with 10 times the mass.
The signal was detected by Nasa's Kepler Space Telescope; astronomers now plan to carry out follow-up observations with Hubble in October. A paper about the candidate moon is published on the Arxiv pre-print site.
[...] The Kepler telescope hunts for planets by looking for tiny dips in the brightness of a star when a planet crosses in front - known as a transit. To search for exomoons, researchers are looking for a dimming of starlight before and after the planet causes its dip in light. The promising signal was observed during three transits - fewer than the astronomers would like to have in order to confidently announce a discovery.
The host star, Kepler-1625, is about 4,000 light years away. The potential exomoon, Kepler 1625b i, has been nicknamed "Nept-moon".
Also at ScienceNews.
The Hunt for Exomoons with Kepler (please update your site).
Hubble finds compelling evidence for a moon outside the Solar System
Using the NASA/ESA Hubble Space Telescope and older data from the Kepler Space Telescope two astronomers have found the first compelling evidence for a moon outside our own Solar System. The data indicate an exomoon the size of Neptune, in a stellar system 8000 light-years from Earth. The new results are presented in the journal Science Advances.
[...] In 2017 NASA's Kepler Space Telescope detected hints of an exomoon orbiting the planet Kepler-1625b. Now, two scientists from Columbia University in New York (USA) have used the incomparable capabilities of the NASA/ESA Hubble Space Telescope to study the star Kepler-1625, 8000 light-years away, and its planet in more detail. The new observations made with Hubble show compelling evidence for a large exomoon orbiting the only known planet of Kepler-1625. If confirmed, this would be the first discovery of a moon outside our Solar System.
The candidate moon, with the designation Kepler-1625b-i, is unusual because of its large size; it is comparable in diameter to the planet Neptune. Such gargantuan moons are unknown in our own Solar System.
Other sources put Kepler-1625 at around 4,000 light years away.
Discoveries like this are why we could use as many identical better-than-Hubble space telescopes as we can build and launch.
Also at Sky & Telescope, Cosmos Magazine, The Verge, Axios, NPR, CNN.
Evidence for a large exomoon orbiting Kepler-1625b (open, DOI: 10.1126/sciadv.aav1784) (DX)
Previously: First Exo-Moon Discovered?
First Known Exomoon May Have Been Detected: Kepler 1625b i
The first suspected exomoon may remain hidden for another decade
A good exomoon is hard to find. Proving that the first purported moon around an exoplanet actually exists could take up to a decade, its discoverers say.
"We're running into some difficult problems in terms of confirming the presence of this thing," said astronomer Alex Teachey of Columbia University at a meeting of the American Astronomical Society on January 10.
[...] That uncertainty is partly because the purported moon seems to be about the size of Neptune, much larger than moon formation theories predict. And the researchers can't rule out that the evidence of the moon isn't actually evidence of a second planet. "We're trying to be very careful about not calling this a discovery, that we've got this beyond a shadow of a doubt," Teachey said.
[...] Ground-based telescopes are trying to confirm if the object is a moon or a second planet based on the object's gravitational tugs on the known planet. That's a much slower process than looking for dips in light from exoplanets and exomoons passing in front of their stars, which is what the Hubble and Kepler data reveal, and could take five to 10 years, Teachey says.
Headline News: Object Not Found.
Previously: First Exo-Moon Discovered?
First Known Exomoon May Have Been Detected: Kepler 1625b i
New Evidence Supports Existence of Neptune-Sized Exomoon Orbiting Kepler-1625b
(Score: 2) by Runaway1956 on Tuesday January 18 2022, @02:12PM (7 children)
I don't understand all the excitement over every little discovery. Especially discoveries that may or may not be interpreted correctly. We have not yet sent a probe to one single exo-body to check it out. No man has ever sat in a cockpit 100 miles above an exo-thing to confirm what all the instruments seemed to be saying. What exactly are the astronomers seeing? "Oh, look Bill, this star kinda flickers periodically." "Cool, Jane, you found a planet!" Months later, "Hey, Jane! The flicker you found on this sun has a flicker of it's own!" "Awesome Bill! You found a moon!"
In reality, the alien's Dyson Belt has a couple of flaws in it, causing light and energy to escape at exactly those periods we interpret as planets and moons. When they complete their sphere, the flickers will disappear, and we'll sit around for decades, trying to figure out how a star can disappear, along with it's planets and moons.
(Score: 0) by Anonymous Coward on Tuesday January 18 2022, @03:12PM (4 children)
What a long-ass way to post, "That's no moon..."
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[ insert propaganda here ]
(Score: 2) by Runaway1956 on Tuesday January 18 2022, @03:59PM (3 children)
You could save yourself a lot of grief by skipping over my posts.
(Score: 0) by Anonymous Coward on Tuesday January 18 2022, @04:42PM
Words of Wisdom from Runaway.
(Score: -1, Offtopic) by Anonymous Coward on Tuesday January 18 2022, @05:08PM (1 child)
“The price of liberty, and even of common humanity, is eternal vigilance.” -Aldous Huxley
(Score: -1, Offtopic) by Anonymous Coward on Tuesday January 18 2022, @05:14PM
Spoken like a true conservative!
(Score: 4, Informative) by LabRat on Tuesday January 18 2022, @04:01PM
Oh, to be this much of a curmudgeon. The Scientific American coverage does a good job explaining why this discovery is important.
The Sky and Telescope article provides the more observation-scrutinous quote:
That said, this is a small Neptune-like orbiting a Jupiter-like, so life isn't the reason we care. It's more about gauging observation power with current equipment.
(Score: 1) by khallow on Wednesday January 19 2022, @03:23AM
Indeed. Can't they just get all these discoveries done at once, so we can get excited about other stuff instead?
(Score: 3, Informative) by inertnet on Tuesday January 18 2022, @04:14PM
Professor David Kipping explains the process [youtube.com] of the find in detail. Searching for exo moons is his specialty.