[syndicated profile] badastronomy_feed

Posted by Phil Plait

[Artwork depicting a gas giant exoplanet with a gas giant exomoon. Credit: Shutterstock / Jurik Peter]

In a paper just published on the astronomy preprint server called arXiv, a group of astronomers has made an astonishing claim: They have found evidence of the possible existence of an exomoon, a moon orbiting a planet orbiting another star. If true, this will be the first moon orbiting an exoplanet ever discovered!

However, I want to be really, really clear here: The evidence is very interesting, and I might even use the word compelling. But it’s not conclusive, and certainly not confirmed. Importantly, the paper has not yet been peer-reviewed, either (it was released early because news of upcoming observations leaked, and the authors wanted to get ahead of any news stories that might be sensationalized; normally, I wouldn’t write about a non-peer-reviewed paper, but I agree with them, and hopefully this will curtail inaccurate coverage). Assuming it passes peer review, what they have here is evidence, which means it needs to be examined carefully, and follow-up observations must be made to further investigate it. If it pans out, it’s a major discovery, and a very exciting one. But please keep in mind the preliminary nature of this while reading.

The exomoon, if it exists, is orbiting an exoplanet named Kepler-1625b, which itself is orbiting a star called Kepler-1625 (and so, if the moon is confirmed it will be called Kepler-1625b-I). The star is similar to the Sun, with about the same mass, though 1.8 times the Sun’s size. This indicates it’s old, and may be starting to swell into a red giant. It also means the star has a low density, which turns out to be important (more on that below). The star is about 4,000 light years from Earth, which makes it apparently pretty dim.

If a planet's orbit is seen face-on from Earth (top) we don’t see a transit, but if it’s edge-on (bottom) we do. Credit: Greg Loughlin (adapted by Phil Plait)


The planet is a gas giant, about the size of Jupiter but with ten times its mass, and takes just under 290 days to orbit the star once. It was found in 2016 using the Kepler spacecraft, designed to look for exoplanets. For several years, Kepler stared at one spot in the sky, looking at the light from 150,000 stars. If a planet orbits its star edge-on as seen from Earth, then every time the planet passes in front of the star, we see a transit, a mini-eclipse. The light from the star dims a bit, and does so once every orbit, revealing the presence of the planet and the length of its year. Not only that, but the amount the light dims also tells us the size of the planet (a bigger planet blocks more light).

If a planet has a moon or moons, they, too, will likely pass in front of the star, dimming it. This is an extremely tricky observation to make, because moons are smaller than planets, and the amount of dimming is very tiny indeed. Attempts to look for exomoons have been tried since exoplanets were first found in the 1990s.



In this case, the astronomers looked at over 6000 individual transits from 284 different exoplanets, and tried to fit them using a physical model of what it would look like if a planet plus a moon transited their host star. But it’s not that simple! You have to try a lot of different combinations of moon sizes, planet sizes, moon orbit sizes, and so on. A whole lot: In the end, each transit was fit with millions of combinations of different physical models!

In almost all the cases, they didn’t find anything; statistically speaking, the transits looked just like lone planets crossing the faces of their host stars. But in one case, they found a transit that looked very much like it was a planet plus a moon. And that was Kepler-1625b.

The problem is, the data are a bit noisy, so it’s not possible to be 100% sure that’s what’s being seen in the observations. Also, because of its relatively long orbit, only three transits were seen for Kepler-1625b. But the data really are interesting.

The three observed transits of the exoplanet Kepler-1625b show odd asymmetries, possibly indicating the presence of an exomoon.

The three observed transits of the exoplanet Kepler-1625b show odd asymmetries, possibly indicating the presence of an exomoon. The dark line is the best fit model of a planet+moon (various other models are plotted with thin purple lines). Credit: Teachey, Kipping, and Schmidt


Normally, a transit is smooth and symmetric except for statistical noise. The start of the dip and the end should look very nearly like mirror images of each other. But that’s not what they saw.

In the first transit, the best model fit shows a small dip preceding the main one, and then a sudden jump in brightness in the middle of the transit. The middle one shows a sudden dip in the middle and a wiggle at the end, and the third shows dips preceding and following the main dip. If the main dip is the exoplanet, those other dips could be caused by a moon!

These transit graphs are why I say the evidence is compelling. The astronomers looked at other possible reasons for them, including instrumental problems, starspots (like sunspots but on the star Kepler-1625), and more. Nothing they found was more likely than the existence of an exomoon. Interestingly, they considered the planet might have a ring system like Saturn’s, but that should produce symmetric dips on either side of the transit, which isn’t seen in all three transits. There are physical ways a ring could do that, but they’re very unlikely. A moon is a better guess.

Assuming that’s what’s causing these extra dips, Kepler-1625b-I is pretty big: Roughly the size of Neptune! It would be orbiting the planet at very roughly 2.5 million kilometers out. That’s a long way, but consider that Jupiter has a moon, Callisto, that orbits it at a distance of almost 2 million km. Since Kepler-1625b has more mass, it could hold on to a big moon at a larger orbital distance.

Jupiter and Neptune

Neptune (left; 49,000 km in diameter) and Jupiter (right; 140,000 km) shown to scale. The exoplanet Kepler-1625 b and the possible exomoon are about the same size, though much farther apart than depicted here. Credit: NASA / JPL & E. Kraaikamp/ D. Peach/ F. Colas / M. Delcroix / R. Hueso/ C. Sprianu / G. Therin / Pic du Midi Observatory (OMP-IRAP) / Paris Observatory (IMCEE / LESIA) / CNRS (PNP) / Europlanet 2020 RI / S2P


The size of the moon (again, if it exists!) is interesting, too. No moon anywhere that big exists in our solar system and, in fact, physical models of how moons form show you can’t form one that size. But that’s not necessarily a problem! Those same models predict the Earth shouldn’t have a moon as big as our Moon, either. But the model assumes the moon forms with the planet, at the same time, and ours is more likely the result of a huge collision that occurred after the Earth formed. Also, it’s possible that a massive planet could capture a big moon — we know Neptune’s moon Triton is a captured object, as are several moons of Saturn and Jupiter.

Another bit I found very interesting: If a moon orbits a planet too far out, the gravity of the star can destabilize the orbit. The moon has to be close enough to the planet for the planet’s gravity to dominate, and this distance can be calculated mathematically. It’s called the Hill sphere, and it depends on the planet’s and star’s density, and the planet’s distance from the star.

At first, it was thought that the star Kepler-1625 was much like the Sun. That was a problem, because a star as dense as the Sun would quickly destabilize an exomoon around Kepler-1625b. But updates to the data show the star is actually bigger than first supposed, possibly on its way to becoming a red giant, as I mentioned earlier. That means its density is lower, and in fact the moon should be stable over billions of years.

So, after all this, how can we find out if it really exists or not? The best way is to do follow-up observations with a big telescope to carefully measure the star’s light before, during, and after a transit of the exoplanet. And that’s just what the team is doing: They have Hubble observations planned for October, during a predicted transit. Given what they know, they’ve been able to predict what the transit graph shape should look like if the moon exists.

If the data are consistent with that, well then, that’ll be interesting, won’t it?

There have been a handful of other exomoon claims made in the past, but like this one, they remain unconfirmed. Given our own solar system, where most of the planets have moons, and even many asteroids and Kuiper Belt Objects do as well, it seems overwhelmingly likely that exoplanets will too. And that’s fine, but we won’t know for sure until we find one. Interestingly, there’s a search on right now for potential moons orbiting the exoplanet Beta Pic b, and if any exist they may very well be found.

This is so cool! We’re right on the edge of a new kind of astronomical endeavor. Once we find one of these exomoons we’ll find more, and they’ll be incredibly useful in helping us understand the planets they orbit.

Of course, that’s still in the future. But maybe not so far in the future.

My thanks to David Kipping, one of the paper authors, for a helpful conversation on this.


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The most bourgeois hotel room in Kiev

Jul. 28th, 2017 02:47 pm
sabotabby: (lolmarx)
[personal profile] sabotabby
We're heading out for lunch as soon as the dude can get the AC working, but in the meantime behold the "VIP suite," in which we will spend our last evening in Kiev. We are pretty sure Soviet dignitaries stayed here and they haven't touched the room since:



Jul. 28th, 2017 12:31 pm
liv: cartoon of me with long plait, teapot and purple outfit (mini-me)
[personal profile] liv
I don't normally care whether people read my links or not, but I would very much like it if as wide an audience as possible saw [personal profile] sovay's post I was anticipating the total destruction of Polish Jewry, about visiting an exhibition of photos from the Lodz ghetto. The subject matter is the Holocaust / Shoah.

I don't know my family history as well as Sovay does. All my great-grandparents were in England by 1900, so none of my close relatives were directly involved. I'm in a similar position that I'm pretty sure there are third etc cousins of mine who should exist but don't. The people who should have been their ancestors might be in the photos; there probably were people related to me among those murdered in Poland, no idea if they were in Lodz specifically.

Whichever Nazi it was that claimed 'a million deaths is a statistic', the scale matters in a different way. That is, one person murdered because of who they are is already too many, but once you get into the millions, everybody is affected. Every Jewish person with any European connections at all might, it's probably best to assume they do, have missing relatives. Every part of history since 1930 is marked by that mass murder.

Anyway. I have more to say but I'm not sure I want to say it on a public post, and you're better reading the linked post anyway.

The Blood is the Life for 28-07-2017

Jul. 28th, 2017 11:00 am
miss_s_b: (Default)
[personal profile] miss_s_b
fairestcat: naked woman reading. vintage (Reading)
[personal profile] fairestcat
Posting another book post, because I'm about to leave for a week of camping at a pagan festival. Since I'm not actually pagan, just pagan-adjacent, and so have no interest in most of the panels and rituals, I mostly end up relaxing and reading a lot. It should be lovely.

The last week has been a mix of queer romances and SF/F short stories.

Seasons of Glass and Iron - Amal El-Mohtar - ★ ★ ★ ★ ★

A gorgeous contemporary fairytale about women saving each other. read more )

Things With Beards - Sam J. Miller - ★ ★ ★ ★

An intriguing and unsettling sequel to the movie The Thing, this is ultimately a story about identity, what we hide of ourselves, what we reveal, and what that choice costs us. read more )

The Orangery - Bonnie Jo Stufflebeam - ★ ★ ★ ★

A striking story about predatory men and the choices women make to escape them, told through the framework of Greek myth.

A Fist of Permutations in Lighting and Wildflowers - Alyssa Wong - ★ ★ ★ ★

Gorgeous, beautifully written story about sisterhood and loss and individual choice, told through a metaphor of superpowers. read more )

Touring With the Alien - Carolyn Ives Gilman - ★ ★

I wanted to like this story -- it's certainly well-written -- but found myself fundamentally disagreeing with it instead. read more )

Spice and Smoke (Bollywood Confidential #1) - Suleikha Snyder - ★

Wow did I hate this book. Enough that I rage-quit it about 2/3 of the way through.

From the summary I went into this book expecting poly relationship negotiations and a generally happy poly ending for everyone.

What I got was jealousy, bitterness and dishonesty, with a side of "you're only sleeping around because you're unhappy," and "when you're really in love with someone you'll want to be monogamous." read more )

Madeleine - Amal El-Mohtar - ★ ★ ★ ★ ★

A gorgeous story about mourning and loss and memory and coming out of the dark.

Madeleine's slow, unexpected journey back from grief is just perfect.

Waiting For The Flood - Alexis Hall - ★ ★ ★ ★

A lovely story about mourning for what might have been and finding the courage to once again dream of the future. read more )

And Their Lips Rang With The Sun - Amal El-Mohtar - ★ ★ ★ ★

A beautiful, unusual folk tale.

El-Mohtar creates a vivid mythology, filled with striking visual imagery.

The Art of Space Travel - Nina Allan - ★ ★ ★

A quiet story about memory and history and legacy set against an SF-nal background.

I liked the narrator and the stream of consciousness style, but it ultimately felt kind of unresolved.

Our Talons Can Crush Galaxies - Brooke Bolander - ★ ★ ★ ★ ★

Short, intense, and unapologetically angry. read more )

Catalysts: The Scientific Method (Scientific Methods Universe #1) - Kris Ripper - ★ ★ ★ ★ ★

Fuck. This is so fucking hot. And kinky. But also intense and emotionally revelatory and unconventionally romantic and one of the most honest depictions of poly I've ever read. read more )

Unexpected Gifts (Scientific Method Universe #2) - Kris Ripper - ★ ★ ★ ★

This series continues to be SO good. read more )

Take Three Breaths (Scientific Method Universe #3) - Kris Ripper - ★ ★ ★ ★ ★

This one's a rough read, but entirely worth it. read more )
fairestcat: Dreadful the cat (Default)
[personal profile] fairestcat
This month you get a double-length playlist, because there were just too many tracks to choose from.

I might have a lot of feelings about the patriarchy and the ways I'd like to fuck it up. One or two at least.

Making it double length also meant I could justify having more than one track by a couple artist.

I've put content warnings on some of these songs. Unsurprisingly, considering the subject matter, there's some discussion of rape and some use of homophobic and misogynistic slurs.

40 songs. 2 hours, 23 minutes of music

fuck the patriarchy (I will not be afraid of women)
Zip file on dropbox (211MB) or Individual tracks on dropbox

As Cool As I Am - Dar Williams
Every Mother's Son - The Pretenders
Quiet - MILCK
Who's That Girl - Robyn
Pretty Hurts - Beyonce
Me And A Gun - Tori Amos (cw: rape)
The Oxford Girl - Oysterband (cw: implied violence against women)
Boys Who Rape (Should All Be Destroyed) - The Raveonettes (cw: rape)
A Girl Needs A Knife - Flash Girls
The Maid On The Shore - Stan Rogers
Real Men - Joe Jackson (cw: homophobic language)
Lucystoners - Amy Ray (cw: homophobic language)
Big Boy On A Saturday Night - Kirsty Maccoll
Daddy Lessons - Beyonce & The Dixie Chicks
Red Dirt Girl - Emmylou Harris
Fast Car - Tracy Chapman
Black Water - Alina Simone
The Old Maid In The Garrett - Steeleye Span
Chill Factor - The Pretenders
Burn - Phillipa Soo
Dixon's Girl - Dessa
Getting Ready To Get Down - Josh Ritter
Manic Pixie Dream Girl - Scary Bear Soundtrack and Avid Napper
Revolver - The Donnas
Break The Sky - The Hush Sound
Cry Like A Man - Christy Moore
When I Was A Boy - Dar Williams
No Mermaid - Sinead Lohan
Drinking With The Jocks - Against Me! (cw: homophobic and misogynistic language)
Androgynous - Joan Jett
Patriarch On A Vespa - Metric
The Ballad of Mary Magdalene - Richard Shindell
Sex Is Not The Enemy - Garbage
Goodbye Earl - Dixie Chicks
Milford Haven - Oysterband
Seneca Falls - The Distillers
I'm In The Band - Bratmobile
Bros - Wolf Alice
Feminism Is For Everybody (With A Beating Heart And A Functioning Brain) - Anti-Flag

As usual, I'd love a comment if you download.

Also, if you like anything I post I encourage you to buy more from the artists.

politics, argh

Jul. 27th, 2017 10:52 pm
cofax7: climbing on an abbey wall  (Default)
[personal profile] cofax7
OH THANK FUCK. (Re: McCain for once did the right thing and voted down the "skinny repeal" bill which would have resulted in 16 million people losing health insurance within a year.)

In other news, I may be giddy with relief, but this made me laugh like a drain.

cheer me up?

Jul. 27th, 2017 10:40 pm
yhlee: Sandman raven with eyeball (Sandman raven (credit: rilina))
[personal profile] yhlee
I had the predictable depressive crash after disrupted sleep (Joe had to go out to work last night from 11:30 p.m. to 4 a.m.--I fell asleep before he got home, but only managed to go to bed around 2 a.m., which is not optimal either).

Send cute kitten pics/silly gamer stories?

Alternately, leave me a silliness prompt and I might write you a tiny!silly!crackficlet?
umadoshi: (fangirl (bisty_icons))
[personal profile] umadoshi
[dreamwidth.org profile] wildpear was over last night, and among other things, we started talking about how it'd been ages since we watched anything together. We keep meaning to do that regularly during our hangouts, but ultimately The X-Files wasn't working for her--it's so very much of its time, although she's glad to have much more context for it now, because of course it's also powerfully influential--and we haven't really started in on anything else, other than the time I showed her an ep. of Princess Jellyfish.

We talked a bit about things we've been watching and meaning to watch individually: me wanting to watch Black Sails, her starting in on season 2 of Switched at Birth (which meant I got to tell her that Allison Scagliotti guest-starred in a couple of episodes at some point--[dreamwidth.org profile] wildpear, if you see this, she's in season 2!) and having watched the first few episodes of Wynonna Earp). Wynonna Earp led to talking about shows that come with the "the first chunk of episodes are weak/terrible/not representative" warning, which is so common (see also: Black Sails), and between those things Stitchers came up, and then I was saying I still haven't seen the final season of The Vampire Diaries, other than the season premiere, even though--despite having wandered off from the show in early season 5 or so--I've been meaning to watch that season because Scags is in it.

I remember showing [dreamwidth.org profile] wildpear a random episode from...uh, I don't remember; maybe late season 2?...back when I was watching TVD, and I don't think she remembers anything about that, but she somehow wound up watching the very first episode at one point and (fairly) thought it was absolutely terrible...and her mentioning that led to me telling her that even though I abandoned the show, it was way better than that once you get through the first chunk of episodes, although I honestly can't imagine ever rewatching past the first couple of seasons (once it gets into the whole Originals thing, roughly).

Upshot: I read her the Wikipedia summaries for episodes 1x01-1x05, and showed her 1x06, in which Elena and Stefan have the whole "oh God, you're a vampire!!!" day of explanations and he tells her some things about Katherine. I don't know if we'll watch further; I'm game, so it depends on her. (From the summary I expected more Katherine backstory than we actually got in that episode, which is why we watched that one, but IIRC that's around when the show actually starts finding its feet.) But wow, so many of the core cast aren't in that episode at all! Jenna's not around (possibly for reasons explained in a skipped episode), and Caroline and Bonnie and Tyler aren't onscreen at all. (Caroline's mom is, though!)

...and okay, I kinda want [dreamwidth.org profile] wildpear to see some of the show so she can see Candice Accola work, because a) I wholeheartedly adore Caroline even though she doesn't remotely match the character type(s) I usually fall for, and b) Accola ("King" now, I guess?) is my fancast for Kelly Connolly in Newsflesh.

(While writing this post I got sidetracked by rewatching vidder dayln03's Caroline vid for the first time in ages, and I'm full of feelings now. I can't find the vid online to link to now, though. :/ The vidder's YouTube profile is easy to find, but that vid isn't there.)

Shortly before [dreamwidth.org profile] wildpear headed home, I wound up telling her some very random things about Game of Thrones, which she is never, ever going to watch. It came up because some of the things people were saying about the current season, at least after the season premiere and maybe second episode, have been making me vaguely want to check in with the show after bailing an episode into...season 5, I think. (Huh. Same as with TVD.) I don't miss Game of Thrones, really, but wow, some of the acting is amazing. (See: Lena Headey for Stacy Mason! I mean, speaking of Newsflesh fancasting.)

(I really ought to consolidate my "fancasting" and "dreamcast" tags here. >.<)
klgaffney: a black cat sitting at a window looking out at the street. (from this side of the glass)
[personal profile] klgaffney
I was getting frustrated with my draft, so I impulsively grabbed Shawn Coyne's The Story Grid off the shelf (it was among the books that lived in All The Boxes--I don't remember buying it so it must've been a while back). And I can already hear the groan (a lot of people really hate this thing), but hey, it's working for me right now.

I decided to use it like a workbook and treat it somewhat like the WorldbuildingJune thing. I got through 36 chapters in two days (this is not as crazy as it sounds, it's got 69 chapters, they're not all demanding that you do a thing, and some bits are nicely bite-sized). Then I abandoned it for a few days because the 'unreasonably exhausted' status intensified to 'completely fuckin' miserable' and hasn't budged (no, not due to the writing stuff). I have tried to distract myself a bit; after I did my revamping and resending out of resumes, I painted some trim in the bathroom that needed a second coat. Then I figured I'd try to poke at this again and I'm still okay with my progress thus far.

some stuff abut the story grid. )

The current thing that has got me hung up a bit is lurking at the beginning of this chapter (entitled 'Math,' so it will be fun). It is only two short lines:

...before we dive into it, remember that you are not the problem. The problem is the problem.

I don't have a problem dealing with that when it comes to the story. But all I can think right now is that I wish I could get that thinking to consistently apply to the rest of my life. It might really help.

*especially since I yoinked my prospective story-beats list off of a comment in Quora. It was a movie-based list, which meant it has exactly the elements I wanted. But I'm thinking it could be applied to only one of the two major POV/plotlines, as one can easily be nudged into one subgenre and one could actually be a different but complementary/overlapping subgenre--and THAT is exactly the kind of thing that working through this book sparked for me. I see no reason to reinvent the wheel. But I do like to make things interesting. If it doesn't work, it doesn't work, but I think it's worth trying and the results could be neat.
archangelbeth: Bleach's Captain Byakuya, three-quarters view. Captioned: sigh (Sigh)
[personal profile] archangelbeth
But no, 3 phone calls. So I gave up.

Stayed in for breakfast. Yay, leftovers. Went out for dinner, which included an ibuprofen and ice tea, so I could get caffeine and hydration and painkiller and stop the withdrawal-headache. (I was doing fine till about 5pm, oddly. *sigh*) Talked mostly about electric bikes and whatnot, instead of politics. (I maintain that electric bikes are likely to be great, but anyone who thinks "take a bike/leave a bike" stuff is gonna kill busses does not have primary-child-custody of 4-5 year olds, family shopping duties, or awareness of a host of other things that are hard enough with busses.)

Kid is doing better, stomach-wise, YAY! I am pretty sure I have a mild case of it, but as I spent months queasy 24/7 when pregnant, it does not surpass that.

Wrote some flashfic yesterday. AU fanfic based off my kid's unfinished work. So many spoilers, so little sense. At least it was writing, of the "characters insist on having a conversation while I'm in the shower" form.

Very upsetting news from a friend. Please send good thoughts... O:(

Havva Quote
<<OOC>> Amelie notes that she has the Pacifist Hindrance, at the 'won't fight except in self-defense' level, so she's going to do the scariest thing she can: start talking.
--from the star trek game

INwatch+Bookwatch )

Dragons under fold )

(no subject)

Jul. 28th, 2017 01:12 am
dancefloorlandmine: Me pointing at camera (Kitchener)
[personal profile] dancefloorlandmine
This is quite an interesting and convoluted tale ...

The Hijacking of the Brillante Virtuoso

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