Exoplanets, Dust, and Who Sees Data First?

NASA/Ames/JPL-Caltech's diagram, comparing the Solar System and Kepler-22's planetary system. (2011)
Comparison: Kepler-22 planetary system and inner Solar System. (2011)

It’s been a little over 10 years since scientists spotted Kepler-22 b. It was the first time we’d spotted a transiting exoplanet that’s in its sun’s habitable zone.

That may or may not mean that Kepler-22 b is habitable. The odds are good that the exoplanet is a water world: covered with an ocean far deeper than Earth’s.

Since then we’ve discovered quite a few water worlds. And, possibly because there’s a 1995 action film called “Waterworld”, they’re often called ocean worlds.1

This week I’ll talk about two (probably) ocean worlds, Kepler-138 c and d; discovered in 2014, they’re far to hot for life as we know it. But scientists recently published a new analysis of those two worlds. And that gave me something to talk about.

So did a proposed change in when taxpayer-funded research projects release data. It’s good news or bad news, depending on who’s talking. That’s this week’s first item.

I’ll also look at a very young planetary system’s dust disk, the odds for life on ocean planets, and assorted other topics:

Sharing Information, and a Newfangled Idea

NASA, ESA, CSA, STScI's image: the Southern Ring Nebula, one of the first James Webb Space Telescope images released to the public. (2022)
The Southern Ring Nebula, image from the James Webb Space Telescope. (2022)

What’s the fairest way to share cosmic views from Hubble and James Webb telescopes?
Nell Greenfieldboyce, NPR (February 7, 2023)

“The managers of the James Webb Space Telescope are considering a big change in how its observations get shared, one that could have a major impact on the science that gets done — and on who gets to do it.

“As it stands now, if an astronomer makes a proposal for where to point this $10 billion space telescope, and the proposal gets accepted, that scientist usually has a year of exclusive access to the resulting observations.

“Now, though, with the federal government pushing for more taxpayer-funded research to be made public instantly, telescope managers are pondering whether all of the data collected by JWST should be available to everyone right away….”

“…with the federal government pushing…” apparently refers to a White House press release and a memo:

On the whole, I like the idea of having access to information I’ve paid for: as soon as it’s in viewable or readable form, not a year of mofd later.

The pandemonium that passes for politics being what it is, an explanation may be in order.

Access to Information

Map of Internet censorship and surveillance by country (2018)I think having access to information is generally a good idea. After a quick glance at that memo, I think this change in the rules might make sense.

But that doesn’t mean that I think the memo is unquestionably right and just, simply because it came from someone in the current administration. And that anyone who doesn’t agree is a doo-doo-head.

On the other hand, I’m not absolutely sure it’s a good idea.

Which doesn’t mean I think the memo is an assault on all that is right and just — because, again, the memo was written by someone working for the current administration. And that anyone who exhibits insufficient revulsion is a traitor to the fatherland.

I’d be delighted of more folks would take a deep breath, consider the possibility that knee-jerk responses aren’t always reasonable: and think! And that’s another topic.

At any rate, some folks like the proposed new rules; and some don’t.

“…Proponents of open access say that sharing all of these space telescopes’ findings immediately could accelerate new discoveries and maximize the return from these powerful scientific assets.

“Critics, however, worry that this could exacerbate existing inequities in who gets to do astronomical research, and perhaps even result in shoddier science as scientists race to be first to find hidden gems in the data….”
(Nell Greenfieldboyce“, NPR (February 7, 2023)

‘We’ve Never Done It This Way Before’

Getty Images: Nature magazine, via BBC News. 'Scientific journals can play a role in helping improve the reliability of reporting' (February 22, 2017)The “shoddier science” argument may have merit. But I’m not entirely convinced.

Scientists are human, and occasionally publish bogus results: intentionally or not.

Letting folks who aren’t insiders see fresh data would, I suspect, be at least as likely to disprove dubious analyses as it would be to inspire another Archaeoraptor SNAFU.2

And I also suspect that some protests come, consciously or not, from a perceived affront to cherished traditions.

“…Astronomers have turned their telescopes to the skies for hundreds of years. Traditionally, they decided how and when to share their records of what they’d seen.

“The data really were more or less owned by the person who came up with the idea to take the observations in the first place,” says Eric Smith, associate director for research at the astrophysics division of NASA’s science mission directorate in Washington, DC.

“An astronomer who used a ground telescope physically possessed their records.

“‘Originally it was just hand drawings, and then it became glass plates, and then it was film in some cases, and eventually it was magnetic tapes,’ explains Smith. ‘Whoever went to the observatory took those data home with them — and they just put them in their office or they put them in some university vault.’…”
(Nell Greenfieldboyce, NPR (February 7, 2023))

My guess is that either now or later, observations from multinational projects like the Hubble and James Webb space telescopes will be distributed sooner than they are now.

That’s mainly because it strikes me that trends have been going that way for decades.

And maybe because I hope that I’ll get a look at data earlier than I could have before.

AU Microscopii’s Dusty Disk: A Close Look, in Infrared

Hubble Space Telescope NIRCam images: AU Microscopii's dust disk at 3.56 and 4.44 microns with polarizing filters F606W (V) (POL0V, POL60V, and POL120V). (August 1, 2004) Credit: NASA, ESA, J. R. Graham and P. Kalas (University of California, Berkeley), and B. Matthews (Hertzberg Institute of Astrophysics)
JWST NIRCam images at 3.56 (blue) and 4.44 (red) microns. (August 1, 2004)

New Webb Image Reveals Dusty Disk Like Never Seen Before
Laura Betz, Claire Blome, Christine Pulliam, Madison Arnold; NASA’s Goddard Space Flight Center, Greenbelt, Maryland; Space Telescope Science Institute, Baltimore, Maryland; NASA (January 11, 2023)

“NASA’s James Webb Space Telescope has imaged the inner workings of a dusty disk surrounding a nearby red dwarf star. These observations represent the first time the previously known disk has been imaged at these infrared wavelengths of light. They also provide clues to the composition of the disk.

“The star system in question, AU Microscopii or AU Mic, is located 32 light-years away in the southern constellation Microscopium. It’s approximately 23 million years old, meaning that planet formation has ended since that process typically takes less than 10 million years. The star has two known planets, discovered by other telescopes. The dusty debris disk that remains is the result of collisions between leftover planetesimals – a more massive equivalent of the dust in our solar system that creates a phenomenon known as zodiacal light….”

AU Microscopii’s designation has little or nothing to do with it being small. It’s in the southern constellation Microscopium.

That patch of sky had been the rear hooves of Sagittarius until the early 1750s, when Nicolas-Louis de Lacaille mapped more than a dozen new constellations, including:

  • Antlia pneumatica (la Machine Pneumatique/the Pneumatic Machine)
  • Apparatus Sculptoris (the sculptor’s studio)
  • Circinus, Norma (compass)
  • Fornax chemical (chemical furnace)
  • Horologium (clock (lit. “an instrument for telling the hour”))
  • Microscopium (microscope)
  • Norma (carpenter’s square, set square or level)
  • Octanis/Octans (octant)
  • Pictor (painter)
  • Pyxis nautica (mariner’s compass)
  • Reticulus rhomboidalis (Reticulum) (the reticle in Lacaille’s telescope eyepiece)
  • Mons Menae (Mensa: originally Table Mountain, later Table)
  • Telescopium (telescope)
    (Source: Nicolas-Louis de Lacaille, Biographies, MacTutor History of Mathematics Archive, University of St. Andrews, Scotland; Wikipedia)

Many of them were named after scientific instruments, which were all the rage in the Age of Enlightenment, and I’m drifting off-topic.

AU Microscopii’s planetary system — it’s got two known planets, roughly 10 and 20 times Earth’s mass — is very new.3

All that dust probably is, as the NASA article said, from leftover planetesimals. But we may learn differently. That’s happened before, and I figure it’ll happen gain.

Take what we’re learning about the inner Solar System’s zodiacal light, for example.

A Zodiacal Digression

Illustration from J. Otto's 'Ottův Slovník Naučný', 'Otto's Educational Dictionary'. (1908)Zodiacal light is a cone of light barely visible before dawn and after sunset, near the sun.

It’s a very faint band of light running along the ecliptic.

A brighter bit, opposite the sun, is gegenschein or counterglow.

Which definition of zodiacal light is in play depends on who’s talking. In my experience, at any rate.

Scientists figure zodiacal light comes from a pancake-shaped dusty area surrounding the Solar System’s inner planets. Or maybe a really flat doughnut.

Either way, it’s called the zodiacal cloud or interplanetary dust cloud.

Where the dust comes from is debatable and debated. Particularly now that we’ve got data from a spacecraft that was looking for something else: Juno.

NASA/JPL-Caltech/SwRI/MSSS' image from the Juno spacecraft: 'Juno took this picture as it flew over the north pole, from a distance of 195,000km' (September 2, 2016) via Jonathan Amos, BBC News, used w/o permissionBefore the Juno spacecraft headed for Jupiter, scientists generally figured that the dust was from asteroids and comets.

Juno’s mission didn’t include observing space-dust. But getting useful data from its magnetometer depended on the spacecraft knowing which way it was pointed.

That’s why Juno had four star trackers, cameras that took pictures every quarter-second, and a simple AI that compared the views with known stars and other objects.

Technical University of Denmark professor John Leif Jørgensen had programmed one of Juno’s four star trackers to send back a picture whenever an uncataloged object showed up more than once.

Jørgensen had hoped Juno would spot a previously-uncharted asteroid.

Serendipitous Juno Detections Shatter Ideas About Origin of Zodiacal Light” Lonnie Shekhtman et al., JPL/NASA (March 9, 2021)

“…He didn’t expect to see much: Nearly all objects in the sky are accounted for in the star catalog. So when the camera started beaming down thousands of images of unidentifiable objects – streaks appearing then mysteriously disappearing – Jørgensen and his colleagues were baffled. ‘We were looking at the images and saying, ‘What could this be?”‘ he said.

“…It wasn’t until the researchers calculated the apparent size and velocity of the objects in the images that they finally realized something: Dust grains had smashed into Juno at about 10,000 miles (or 16,000 kilometers) per hour, chipping off submillimeter pieces of spacecraft. ‘Even though we’re talking about objects with only a tiny bit of mass, they pack a mean punch,’ said Jack Connerney, Juno’s magnetometer investigation lead and the mission’s deputy principal investigator, who’s based at NASA’s Goddard Space Flight Center in Greenbelt, Maryland….”

Long story short, Juno made it through the unexpected ‘dust storm’. Mainly because most of the impacts were on the comparatively rugged back side of the spacecraft’s solar panels.

The best fit for explaining all that dust was that it was coming from Mars. Some scientists figure the recent analysis is accurate. Others don’t.4 Which is about par for the course, when we find new data that doesn’t fit existing explanations.

A Dust Disk by Starlight: Polarized Light, Oscillations and Weird Ripples

NASA, ESA, J. R. Graham and P. Kalas (University of California, Berkeley), and B. Matthews (Hertzberg Institute of Astrophysics)'s image of AU Microscopii's dust/debris disk; from Hubble Space Telescope (August 1, 2004) through filters Filters F606W (V), (POL0V, POL60V, and POL120V). Scale in AU, size of Neptune's orbit, location of star and occulting disk added.
Hubble image of AU Microscopii debris/dust disk (August 1, 2004)

At this point, I’d like to start sharing what the new images of AU Microscopii’s dust disk tell us about how stars and planets form, what causes the weird ripples — I’ll get back to that — and how it ties into our search for life on other worlds.

But I can’t. The most recent analysis I found said, basically, that we’ve been learning a great deal about how data like this should be analyzed.

They also said they’d found evidence of silicates like MgFeSiO4, carbon and tholins: organic compounds that happen when ultraviolet light or cosmic rays hit simpler compounds like carbon dioxide (CO2), methane, (CH4) or ethane (C2H6). Nitrogen (N2) or water (H2O) are part of the process, too, often enough.5

And that’s enough chemical geek-speak for now.

Here’s an excerpt from what scientists found in a new “snapshot” of AU Microscopii’s debris/dust disk.

Hubble’s Snapshot of Debris Disk Around Young Star
J. R. Graham and P. Kalas (University of California, Berkeley), and B. Matthews (Hertzberg Institute of Astrophysics); ESA/NASA; Images, Resource Gallery, HubbleSite (January 7, 2007)

“…The image shows the flattened disk, appearing like Saturn’s rings, but seen almost exactly edge-on. Normally, starlight would be so bright that the debris disk could not be seen. But astronomers used the coronagraph on Hubble’s Advanced Camera for Surveys, which blocked out most of the starlight. The black circle in the center of the image is the coronagraph’s occulting disk. The disk in this image extends to about 8 billion miles from the star, or three times farther than Neptune is from the Sun. In other observations, the disk has been traced to at least 11 billion miles.

“The only light seen is starlight reflected off dust in the debris disk. Astronomers used polarizing filters on the Advanced Camera to analyze the dust in the disk. The polarizing filters allowed astronomers to study how dust is reflecting the starlight. A polarizing filter lets through light vibrating in one orientation while blocking light oscillating in other directions. The white lines in the bottom image illustrate the direction a light wave is oscillating. The length of the line represents the degree to which all the light waves are oscillating in the same direction….”

I think a key word here is “oscillating.” AU Microscopii is close enough for us to get a good look at the star’s planetary system, dust included. And even get the occasional video.

These “mysterious ripples” are weird. Which, for scientists, is a very good thing.

Mysterious Ripples Found Racing Through Planet-forming Disk
Ray Villard, Space Telescope Science Institute, Baltimore, Maryland; Lynn Jenner, Editor; Hubble, NASA (October 7, 2015; last updated August 6, 2017)

“…The fast-moving, wave-like structures are unlike anything ever observed, or even predicted in a circumstellar disk, said researchers of a new analysis. This new, unexplained phenomenon may provide valuable clues about how planets form inside these star-surrounding disks….”

I’d be astounded if we don’t learn something from those ripples. Although I suspect “waves” or maybe “spurts” is a better term.

And I’m pretty sure that we’ll learn more from comparing the AU Microscopii system’s cloud to similar features in other systems.

Hot Jupiters, Planetary Migration: And Much More Left to Learn

NASA, ESA, ESO, A. Boccaletti (Paris Observatory)'s images: AU Microscopii's 40 billion-mile diameter edge-on disk, showing ripples moving across the disk at about 22,000 miles per hour: something that's not been seen before. (2010-2014)
AU Microscopii’s dust disk, with ripples traveling 22,000 miles per hour. (2010-2014)
This phenomenon had not been observed before, and had not been predicted.

B. Saxton (NRAO/AUI/NSF)/ALMA (ESO/NAOJ/NRAO)'s images of dust disks around nine young stars, from SPHERE instrument on ESO's Very Large Telescope. (April 2018)The nebular hypothesis is still the best, or least-unlikely, explanation for how our Solar System and other planetary systems take shape. But it’s still called a hypothesis.

How long it’ll take scientists to either confirm the nebular hypothesis, or show that it doesn’t work: that, I don’t know.

I’m pretty sure, though, that the process will take less time now. Before, we had only one planetary system to study. Now we have thousands.

Of those, dozens (at least) have dust disks. I’m not sure if that includes protoplanetary disks and proplyds: ionized protoplanetary disks.

The point is that we’ve gone from studying one example of a ‘finished’ planetary system, to studying thousands. Some of them are really weird, which gives scientists opportunities for learning something new.

Hot Jupiters, for example, encouraged — demanded? — new explanations for how planets end up where we find them.

Turns out that planets can and do move into new orbits, particularly when planetary systems are new. It’s called “planetary migration.”

The process is also complicated, and very likely explains how Earth’s Moon formed. I like to call it “playing bumper cars with planets”.

Finally, we’ve found dozens of planetary systems, at least, that are in very early stages of development: like AU Microscopii’s.6

As I’ve said before, and will again, there’s a great deal left to learn.

Zodiacs, Dust and Loose Ends

Now, mainly because I think it’s cool, here’s link to a NASA Goddard video with music by Vangellis. It talks about interplanetary dust, Mars and Jupiter.

Our Solar System’s zodiacal cloud isn’t unique. Astronomers have been spotting interplanetary dust clouds (“exozodiacal dust”) in other planetary systems.

Let’s see. What else?

The “zodiac” is a band of constellations running along the ecliptic. The ecliptic is Earth’s orbital plane, or the line where that plane meets the celestial sphere.

Steve Zodiac is the name of a character in the 1960s science fiction puppet show “Fireball XL5”, and guitarist and songwriter Stephen John Hepworth’s stage name. All of which are yet more topics.7

Kepler-138 c, d: “Water, Water Everywhere?”

Benoit Gougeon's (University of Montreal) 'illustration showing a cross-section of the Earth (left) and the exoplanet Kepler-138 d (right). Like the Earth, this exoplanet has an interior composed of metals and rocks (brown portion), but Kepler-138 d also has a thick layer of high-pressure water in various forms....' (2022)
Benoit Gougeon’s illustration: Earth (left) and Kepler-138 d (right). (2022)

Two Exoplanets May Be Mostly Water, NASA’s Hubble and Spitzer Find
Claire Andreoli, NASA’s Goddard Space Flight Center, Greenbelt, Maryland; Ray Villard, Space Telescope Science Institute, Baltimore, Maryland; Marie-Eve Naud, Trottier Institute for Research on Exoplanets, University of Montreal, Montreal, Canada; Caroline Piaulet, Trottier Institute for Research on Exoplanets, University of Montreal, Montreal, Canada; Björn Benneke, Trottier Institute for Research on Exoplanets, University of Montreal, Montreal, Canada; Editor Andrea Gianopoulos; Hubble; NASA (last updated December 15, 2022)

“A team led by researchers at the University of Montreal has found evidence that two exoplanets orbiting a red dwarf star are ‘water worlds,’ where water makes up a large fraction of the entire planet. These worlds, located in a planetary system 218 light-years away in the constellation Lyra, are unlike any planet found in our solar system.

“The team, led by Caroline Piaulet of the Trottier Institute for Research on Exoplanets at the University of Montreal, published a detailed study of this planetary system, known as Kepler-138, in the journal Nature Astronomy today….”

The article’s two exoplanets are Kepler-138 c and d. They’re both about 1.5 times Earth’s diameter, but only 2.3 (Kepler-138 c) and 2.1 (Kepler-139 d) times Earth’s mass: give or take a bit.

That means they’re a whole lot less dense than Earth. The scientists are pretty sure of their data, which includes observations with the Keck Observatory’s High Resolution Echelle Spectrometer. And if I go down that rabbit hole, I’ll never get this thing finished in time.

The Kepler-138 planetary system has at least one more planet, Kepler-138 b, and maybe a fourth: Kepler-138 e.

Kepler-138 b is a little over half Earth’s diameter and almost certainly a rocky world, like the Solar System’s inner planets.

Kepler-138 e may or may not be there. Its existence hasn’t been confirmed, but if it is, it’ll be near the inner edge of the system’s habitable zone.

The other three planets — b, c, and d — are between the habitable zone and their sun: too hot for life. As we know it, at any rate, and that’s yet again another topic.

More like Enceladus than Earth, But Not Quite Like Either

NASA's illustration, showing the likely inner structure of Enceladus. (2017) via BBC News, used w/o permission.There aren’t any planets like Kepler-138 c and d in the Solar System. But some of the outer Solar System’s moons are similar.

Saturn’s Enceladus, for example, has an ocean that’s around 26 to 31 kilometers deep: 16 to 19 miles.

By comparison, Earth’s ocean has an average depth of 3.7 kilometers. Or 3,682 meters, if you’re into three-decimal-place accuracy. That’s on average.

Some parts of Earth’s ocean are more than 10,000 meters, 32808.4 feet deep. And its depth at the shore goes down to zero. Or would that be up to zero? Never mind.

Earth’s ocean is covered by ice around the north pole; and would be at the south pole, if Antarctica wasn’t there. Enceladus, on the other hand, is covered by a thickish ice crust: but not thick enough to keep geysers from happening at the south pole.

Kepler-138 c and d are too hot for an ice crust like Enceladus’, or ice caps like Earth’s.

They might, however, have very hot oceans under an atmosphere that’s mostly steam.8

This NASA video gives a pretty good — and, at 89 seconds, short — overview of why scientists think Kepler-138 c and d are “water worlds”, or ocean planets:

Too Much of a Good Thing: or Maybe Not

Natalie Batalha's and Wendy Stenzel's chart of exoplanet populations found with Kepler data. (2017) (NASA and Ames Research Center)Life needs water, but water worlds or ocean planets may have too much of a good thing.

Then again, maybe not.

Life needs water, but it doesn’t just need water: besides an energy source, living critters need chemicals dissolved in water. In a sense, living critters are chemicals dissolved in water.

Rainwater falling on Earth’s land surfaces picks up elements and compounds, eventually delivering them to the ocean. With no land surfaces, an ocean planet might have too little stuff — particularly phosphorus — dissolved in its water to support life. Or get life started.

Besides having no rocky surface above water level, the liquid water of ocean planets might have no contact with the rocky surface below them. Water that’s at the ocean’s floor would be under extreme pressure.

At extreme pressures, water can turn to ice at very high temperatures. Weird ice, but quite solid enough to keep the rock below from dissolving.

And it gets worse, maybe. Some scientists crunched numbers, and found that an ocean planet’s rocky crust and mantle might be under so much pressure that the planet’s interior couldn’t get fluid enough to start geological process that recycle chemicals here on Earth

On the other hand, scientists from the University of Chicago and Penn State crunched other numbers: and got a fair number of virtual ocean planets that were life-friendly.

It’s far too early to tell whether ocean planets can be habitable. As far as I can tell, that is.

The consensus seems to be that we need more data. Which, happily, keeps coming in.9

Wolf 1069-b, Very Briefly

Roger Sinnott, Rick Fienberg's IAU /Sky and Telescope magazine sky map: Cygnus. (June 5, 2011)I’m forgetting something.

Let me think — Right! A planet.

Last week I mentioned Wolf 1069 b, an exoplanet orbiting Wolf 1069: which is also called GJ 1253 or Glies 1253.

Anyway, Wolf 1069 b is in its star’s habitable zone. Its minimum mass is about the same as Earth’s. It doesn’t cross its sun’s face from where we are, and it orbits a red dwarf star.

Wolf 1069 is in the north end of Cygnus, in the same general direction as Eta Cephei, but closer: a little over 31 light-years, compared to Eta Cephei’s 46 and a half.

That makes Wolf 1069 b the sixth-closest roughly-Earth-Mass exoplanet that’s inside a conservatively-defined habitable zone.10

Coming Attractions

Alejandro Suárez Mascareño's and Inés Bonet's (IAC) impression of GJ 1002's two Earth-mass planets.I had more left to say about GJ 1002 b and c last week.

They’re maybe-habitable worlds orbiting a red dwarf that’s about 16 light-years away.

One of the points I was going to talk about was tidal locking: the situation that has Earth’s Moon always facing Earth, and Mercury rotating three times for every two revolutions/orbits around the Sun.

Meanwhile, I’ve found a recent article about Wolf 1069 b.11

After a little rummaging through my digital archives, I also found a paper from 2013 that discussed conditions on a hypothetical planet with an extensive ocean in a red dwarf’s habitable zone.

The 2013 paper shows how ocean currents and wind could cool a tidally-locked planet’s day side and warm the part where it’s always night. And the researchers’ analysis gave the hypothetical planet a vaguely lobster-shaped area of open water on the day side.

I’ll either talk about that next week, or give you a break and look at something besides exoplanets and our ongoing search for extraterrestrial life.

If you’ve got a preference one way or the other, feel free to say so in a comment.

No guarantees made or implied, though, 😉 since looking at something else depends on finding something else. That said, this bit of weirdness, a nearly-complete fossilized skeleton found in Germany, has possibilities:

More about exoplanets, life and how we’ve been naming stars:

1 Strange new worlds, science and an action film:

2 Sometimes repeatable results aren’t, and data isn’t real:

3 A star, an astronomer, and planets under construction:

4 Zodiacal miscellanea:

5 Life’s building blocks and a dust cloud:

6 Learning how planetary systems form:

7 more miscellanea:

8 Oceans and astronomy:

9 Oceans in the sky:

10 Wolf 1069, mostly:

11 Tides and tidally-locked worlds:

About Brian H. Gill

I was born in 1951. I'm a husband, father and grandfather. One of the kids graduated from college in December, 2008, and is helping her husband run businesses and raise my granddaughter; another is a cartoonist and artist; #3 daughter is a writer; my son is developing a digital game with #3 and #1 daughters. I'm also a writer and artist.
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