A Super-Earth With an Air About It: 55 Cancri e, Janssen

This month’s analysis of a piping hot super-Earth’s atmosphere is a big deal.

But it’s not the “first” detection of a terrestrial exoplanet’s atmosphere, not by about eight years.¹

I’ll be talking about how scientists sift through data, 55 Cancri e’s atmosphere, its planetary system, why 55 Cancri e — the exoplanet was officially named Janssen in 2015 — and why calling Janssen a “diamond planet” may be appropriate.

• Scientists and 55 Cancri e: How They Know What They Know
  • Bayesian Basics and Dealing With Incomplete Data
  • Studying Starlight: Transits, Eclipses, and a Whole Lot of Math
• Welcome to the Copernicus Planetary System
  • There’s No Place Like Home: But the Copernicus System Comes Close
  • Copernicus: Giant Planets and a Super-Earth Circling a Slightly Strange Star
• Janssen: ‘Terrestrial’, But Not Like Earth
  • Like a Diamond in the Sky?
  • Carbon Planets: Carbides and Maybe Diamonds

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Scientists and 55 Cancri e: How They Know What They Know

The Copernicus (55 Cancri A) planetary system is just like the Solar System. Except for how it’s different.

“NASA’s Webb Hints at Possible Atmosphere Surrounding Rocky Exoplanet“
NASA Webb Mission Team, Goddard Space Flight Center, NASA (May 8, 2024)

“Researchers using NASA’s James Webb Space Telescope may have detected atmospheric gases surrounding 55 Cancri e, a hot rocky exoplanet 41 light-years from Earth. This is the best evidence to date for the existence of any rocky planet atmosphere outside our solar system.

“Renyu Hu from NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, is lead author on a paper published today in Nature. ‘Webb is pushing the frontiers of exoplanet characterization to rocky planets,’ Hu said. ‘It is truly enabling a new type of science.’…”

I’m not sure exactly what “new type of science” Dr. Hu had in mind. This Dr. Hu is the one with a PhD in planetary science from MIT, by the way; not the nuclear physicist who retired in 1994.

At any rate, this Dr. Hu is the lead author of “A secondary atmosphere on the rocky Exoplanet 55 Cancri e”, published in Nature on May 8, 2024.

And, although Nature is a peer-reviewed scientific journal that’s currently unavailable to me, I do have access to a very recent pre-press draft on Cornell’s open-access arXiv service.¹ I’ve talked about paywalls, member-only online resources, and other frustrations, before.

Getting back to “a new type of science”, the data Dr. Hu’s team was working with is new: partly from 2023 observations by the James Webb Space Telescope.

But as far as I could tell, they’re not using new mathematical tools. On the other hand, I could have missed something. I’m taking it easy this week, and didn’t pore over their pre-print paper all that intently.

Bayesian Basics and Dealing With Incomplete Data

Maybe part of the “new science” is running data through several analyses, with a different team working on each analysis.

“…The NIRCam data were analyzed by 4 independent teams with different pipelines (Methods). We removed 1/f noise (the correlated read noise that impacts data across a wide range of timescales with a 1/f power spectrum³³)…”
(“A secondary atmosphere on the rocky exoplanet 55 Cancri e’“; Renyu Hu, Aaron Bello-Arufe, et al.; (submitted May 8, 2024) via arXiv, Cornell University)

Besides spreading out the workload, independent analysis teams should lower the odds that folks who are crunching the numbers will unintentionally bias their results. That can be a problem for any sort of analysis, not just science stuff, and that’s another topic.

One of the tools Hu and company used is Bayesian math: which I hadn’t noticed in research papers until fairly recently. But then, I’m not a scientist; and it wasn’t until fairly recently that I could get my virtual hands on such things.

Bayesian statistics is what happened when Pierre-Simon Laplace started working on Bayes’ theorem. Bayes was a statistician, philosopher, and Presbyterian minister. A whole bunch of folks have fine-tuned what we call Bayesian statistics, but I’ll skip all that.

Basically, Bayesian statistics lets scientists work out the odds that something is true, based on facts that may or may not matter. It’s useful when we don’t know everything.²

Which, arguably, is pretty much always the case.

Studying Starlight: Transits, Eclipses, and a Whole Lot of Math

Studying 55 Cancri e would be fairly easy, if it was in the Solar System. We’d just point a telescope toward the planet and take a few pictures.

If 55 Cancri e’s edges were fuzzy, that’d mean it’s got an atmosphere.

Scientists could put a spectrometer on the telescope, look at what wavelengths get reflected and/or absorbed, and that’d tell them what’s in the atmosphere or on the surface.

Or they could arrange for a probe to be dropped into 55 Cancri e’s atmosphere, and get data from that.

Just one problem. Light from 55 Cancri e takes 41 years to get here. Astronomers are doing well to work out which parts of the 55 Cancri A system’s light are coming from planets, and which are from the star.

Happily, since 55 Cancri e passes in front of and behind its star during each orbit, careful observations tell scientists quite a bit about the planet.

The trick is measuring light when:

• Both are visible and neither is blocked
• The planet blocks part of the star’s light
• The star blocks light reflected by the planet

Then, using a whole lot of math, scientists work out what’s reflected from the just planet. And what is (or isn’t) shining through the planet’s atmosphere: if it’s got one.

I talked about this last year, along with what we’re learning about weather — winds, specifically — on WASP-18b.³

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Welcome to the Copernicus Planetary System

55 Cancri is a double star, between Rho² and Iota Cancri in our sky.

55 Cancri B is a red dwarf with no name.

But in 2015, the IAU made it official: 55 Cancri A’s name is Copernicus.

Copernicus / 55 Cancri A’s planets are:

• Galileo (b)
• Brahe (c)
• Lipperhey (d)
• Janssen (e)
• Harriot (f)

55 Cancri has a Bonner Durchmusterung designation, BD+28°1660, which strongly suggests that it was known at least as far back as the mid-19th century.

Scientists started spotting planets around 55 Cancri A in the late 20th century.

Galileo, 55 Cancri b, was discovered in 1996; Janssen, 55 Cancri e — the planet I’m talking about this week — was discovered in 2004.

Harriot’s discovery, that’s 55 Cancri f, was announced in 2005 and published in 2007.

At that point, the Copernicus planetary system had five known planets. The last I checked, there’s informed speculation that there may be more.

So how come one of last week’s headlines announced the “discovery” of Janssen??

• “Scientists announce discovery of a planet twice as big as Earth with a thick atmosphere”
  Adithi Ramakrishnan, Associated Press, Science, PBS News Hour (May 8, 2024)

I suspect deadline pressures are a factor, along with the need to grab attention.

That may account for headlines like these:

• “Astronomers finally detect a rocky planet with an atmosphere“
  Will Dunham, Reuters (May 8, 2024)

That’d be impressive, if other scientists hadn’t published this research, back in 2016:

• “Detection of an atmosphere around the super-Earth 55 Cancri e”
  A. Tsiaras et al., The Astrophysical Journal (March 24, 2016)

In my darker moments, I feel that many news editors got their science education by watching “Captain Planet and the Planeteers” and “The Fifth Element”.⁴

More likely, the headlines and articles reflect each publication’s readership: 0r editorial perceptions thereof.

• “James Webb telescope detects 1-of-a-kind atmosphere around ‘Hell Planet’ in distant star system”
  Joanna Thompson, Live Science (May 12, 2024)
• “Diamond-covered ‘super Earth’ Janssen intrigues scientists”
  The Times of India (October 28, 2023)

The “Diamond-covered” description isn’t entirely inaccurate. I’ll get back to that.

There’s No Place Like Home: But the Copernicus System Comes Close

Although the Copernicus planetary system has a Jupiter-sized planet orbiting at about Jupiter’s distance, it’s not quite like our Solar System.

It is, however, the second-closest match we’ve found, as far as I know.

“Second Planetary System Like Ours Discovered“
Shannon Hall, Universe Today (November 27, 2013)

“…KOI-351 is ‘the first system with a significant number of planets (not just two or three, where random fluctuations can play a role) that shows a clear hierarchy like the solar system — with small, probably rocky, planets in the interior and gas giants in the (exterior),’….”
[emphasis mine]

“Our Solar System’s Cousin?“
NASA/JPL-Caltech (November 6, 2007)

“…The 55 Cancri system is currently the closest known analogue to our solar system, yet there are some fundamental differences.

“The similarities begin with the stars themselves, which are about the same mass and age. Both stars also host big families of planets….

“…In addition, both planetary systems have giant planets in their outer regions. The giant located far away from 55 Cancri is four times the mass of our Jupiter, and completes one orbit every 14 years at a distance of five times that between Earth and the sun … Our Jupiter completes one orbit around the sun every 11.9 years, also at about five times the Earth-sun distance….”
[emphasis mine]

Other stars, like HD 70642 and HIP 11915, have roughly Jupiter-mass planets orbiting about as far out as Jupiter. But again: the Copernicus system is still among the very few that resemble our Solar System.

Make that vaguely resemble.

The KOI-351 system — it’s also called Kepler-90, has a mess of other designations, and if I start talking about that, this won’t be ready by Saturday.

Anyway, the KOI-351/Kepler-90 system has eight planets.

The smaller ones orbit close to their star, which is almost but not quite like ours. So far, the KOI-351 system sounds just like the Solar System. Except that all eight planets are closer to their sun than Earth is to ours.

The Copernicus / 55 Cancri planetary system has a roughly Jupiter-mass planet in an orbit roughly as big as Jupiter’s.

But the other known planets aren’t arranged like the Solar System’s:with smaller, rocky, worlds close to the star and giant planets farther out.

Here’s the known Copernicus system planets, starting with the innermost one:⁵

• e (Janssen) — 7.99 times Earth’s mass, 1.875 times Earth’s diameter
• b (Galileo) — 0.8 times Jupiter’s mass, maybe more
• c (Brahe) — 51.2 times Earth’s mass, maybe more
• f (Harriot) — 49.8 times Earth’s mass, maybe more
• d (Lipperhey) — 3.12 times Jupiter’s mass, maybe more

I left out symbols like ±, M_{[astronomical symbol meaning “Earth”]}, and M_J, which say which Solar System planet is being used for comparison, and how accurate our data is. Basically, those numbers are approximations, but pretty close.

Copernicus: Giant Planets and a Super-Earth Circling a Slightly Strange Star

Lipperhey, the outermost known planet in the Copernicus system, is roughly three and an eighth times Jupiter’s mass.

The inner planets — Janssen, Galileo, Brahe, and Harriot — all have orbits smaller than Earth’s.

Janssen, the one I’m talking about today, whips around Copernicus once every 17 hours and 41 minutes. Just under 17 hours and 41 minutes, actually. The point is that it’s really, really, close to its sun.

On top of that, Copernicus is a slightly odd star. Although is it’s a trifle cooler and less massive than our sun, Copernicus apparently puts out a bit more energy than a K0-V main sequence star should.

So it’s classed as K0IV-V: maybe on the main sequence, maybe a subgiant star.

More oddities: Copernicus has more “metals” than our sun. In astronomer-speak, a “metal” is any element heavier than hydrogen or helium. Copernicus has 186% the solar amount of iron; and a carbon/oxygen ratio of 0.78, compared to our star’s 0.55.

All that apparently makes the age of Copernicus hard to work out. But, whether it’s 7,400,000,000 years old or 12,700,000,000 years old, it’s been around considerably longer than the Solar System.

Janssen isn’t quite so ambiguous. It’s a super-Earth that actually is a terrestrial planet: a rocky (?) world, like Earth. It’s twice our home’s diameter, and so hot that it might have had an atmosphere of vaporized rock.⁶

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Janssen: ‘Terrestrial’, But Not Like Earth

Again, Janssen is almost certainly a terrestrial planet: like Mercury, Venus, Earth-Moon, and Mars in the Solar System. I’m inclined to see the Earth-Moon system as a double planet; which is yet another topic.

But Janssen’s ‘rocks’ may not be the silicate sort we’re familiar with.

Now, about Janssen’s atmosphere. Thanks to this month’s “A secondary atmosphere on the rocky exoplanet 55 Cancri e” paper, we can be pretty sure Janssen has an atmosphere; and that Janssen’s air isn’t made of rock vapor.

Odds are that Janssen’s atmosphere has a fair amount of carbon dioxide or carbon monoxide, something that’s mentioned in the study’s opening Summary Paragraph:

“…The measurements rule out the scenario where the planet is a lava world shrouded by a tenuous atmosphere made of vaporized rock^29-32, and indicate a bona fide volatile atmosphere likely rich in CO₂ or CO. This atmosphere can be outgassed from and sustained by a magma ocean….”
(“A secondary atmosphere on the rocky Exoplanet 55 Cancri e“, Renyu Hu et al., preprint (May 2024) via arXiv)

They used data from the James Webb Space Telescope’s MIRI (Mid-Infrared Instrument) and NIRCam (Near-InfraRed Camera) — I talked about JWST and infrared astronomy last December.

I remember reading about carbon dioxide and monoxide in Janssen’s atmosphere in science news articles: but not an odd chemical mentioned in the research paper’s main text:

“…The presence of H₂O, SO₂, or PH₃ could improve the fit to the spectral modulation in 4-5 μm in some cases. In the other set of models, we assumed an atmosphere in volatile equilibrium with the underlying magma ocean⁴⁴,⁴⁵….

“…In summary, the best-fit models center around three possible scenarios: a CO₂-rich atmosphere (C+O~10-3, C/O<1), a CO-dominated atmosphere (C+O~1, C/O>=1), or a PH₃-rich atmosphere with minimal C+O influence (C/O=1, C+O=10^-7, PH₃~10^-4). The first scenario is uniquely favored when fitting the NIRCam data alone (Extended Data Fig. 8), which is consistent with spectral retrievals. By contrast, the MIRI data does not indicate any clear molecular features, suggesting either efficient heat redistribution or overlapping absorption features (e.g., H₂O in 7-9 μm and CO₂ in 9-11 μm) that place the photosphere to the cooler regions of the atmosphere….”
(“A secondary atmosphere on the rocky Exoplanet 55 Cancri e“, Renyu Hu et al., preprint (May 2024) via arXiv) [emphasis mine]

Phosphine, PH₃, is a compound of phosphorus and hydrogen. It’s highly toxic, and used for both pest control and microelectronics manufacturing.

Other than what Hu et al. said about adding a dash of phosphine for a better fit, I don’t see why they picked that particular compound.

Hydrogen is by far the most common element in this universe. Carbon and oxygen are both among the 10 most common elements, at least in this galaxy. Phosphorus isn’t.

My guess is that someone will crunch numbers for the “PH₃-rich atmosphere with minimal C+O influence” atmosphere model.

I suspect it’s just a matter of time before a reporter notices PH₃, phosphine, in one of the study’s models; and remembers the occasional published reports of phosphine in the atmosphere of Venus.⁷

Although phosphine might be a biosignature, the odds of life on Venus are almost nil, and they’re even less for Jannsen.

Diamonds are another matter.

Like a Diamond in the Sky?

“Nearby super-Earth likely a diamond planet“
“New research led by Yale University scientists suggests that a rocky planet twice Earth’s size orbiting a nearby star is a diamond planet.”
YaleNews (October 11, 2012)

“New research led by Yale University scientists suggests that a rocky planet twice Earth’s size orbiting a nearby star is a diamond planet.

“‘This is our first glimpse of a rocky world with a fundamentally different chemistry from Earth,’ said lead researcher Nikku Madhusudhan, a Yale postdoctoral researcher in physics and astronomy. ‘The surface of this planet is likely covered in graphite and diamond rather than water and granite.’…”

I said I’d get back to this:

• “Diamond-covered ‘super Earth’ Janssen intrigues scientists”
  The Times of India (October 28, 2023)

Each time scientists publish something about 55 Cancri e, Janssen, I can count on headlines like these popping up:

• “NASA Discovers Exoplanet Made Of Diamond And 9 Times Bigger Than Earth“
  Curated by Buzz Staff, News18, Delhi, India (May 11, 2024)
• “A scorching hot lava planet made of diamonds has grown second atmosphere after its star destroyed…“
  Livemint, Mint (May 11, 2024)

As I said earlier: reporters and editors deal with deadlines, headlines are supposed to grab attention, and Janssen was discovered in 2004. Under the circumstance, I’m impressed when an article clarifies whether “big” refers to width or mass.

“…The width of the planet is about twice that of Earth and is around 9 times heavier than Earth. According to the information shared by NASA, this exoplanet is known as 55 Cancri e….”
(“NASA Discovers Exoplanet Made Of Diamond And 9 Times Bigger Than Earth“, Curated by Buzz Staff, News18, Delhi, India (May 11, 2024))

However, I’m not clear on where “the information shared by NASA” came from. NASA does have 55 Cancri e-related content, but it also gives Janssen’s mass as “7.99 Earths”.⁸

Maybe the “around 9 times heavier” thing came from truncating “7.99″. I don’t know.

Carbon Planets: Carbides and Maybe Diamonds

I have to admit that ‘diamond planet’ is a catchy phrase.

And Janssen may, in fact, have “a fundamentally different chemistry from Earth”. Which isn’t, actually, a new idea.

The Solar System’s inner planets are mostly silicates, “rocks”, and metals like iron. Much of the stuff we call rocks are silicates: compounds of oxygen and silicone.

At least since 2005, scientists have been saying that an exoplanet’s “rocks” might be made of elements other than oxygen and silicone. Like, for example, carbon and silicone. A “carbon planet” could have an iron-rich core with a mantle of silicon carbide.

And, if there’s enough pressure down where the planet’s mostly carbon, there could be diamonds instead of graphite.

Since Janssen’s sun has significantly more carbon than ours, it may really be a “diamond planet”.⁹ If so, finding proof will take time.

More, mostly about planets and stars:

• “Hearing the Universe, Touching the Stars”
  (February 24, 2024)
• “Colliding Planets Near ASASSN-21qj: Maybe”
  (January 6, 2024)
• “Supernova Remnant Cassiopeia A: Cool Images of Hot Gas”
  (December 16, 2023)
• “WASP-18 b and Other Wonderfully Weird WASP Worlds”
  (June 10, 2023)
• “Super-Duper Super Earths and the Search for Life”
  (May 27, 2023)

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¹ Scientists, research, and a scientific journal:

• Wikipedia
  • Hu Renyu (nuclear physicist, born 1931)
  • Nature (journal)
• “A secondary atmosphere on the rocky Exoplanet 55 Cancri e”
  Renyu Hu, Aaron Bello-Arufe, Michael Zhang, Kimberly Paragas, Mantas Zilinskas, Christiaan van Buchem, Michael Bess, Jayshil Patel, Yuichi Ito, Mario Damiano, Markus Scheucher, Apurva V. Oza, Heather A. Knutson, Yamila Miguel, Diana Dragomir, Alexis Brandeker, Brice-Olivier Demory; preprint draft of paper published in Nature (May 8, 2024) (submitted May 8, 2024) via arXiv, Cornell University
• “First Detection of Super-Earth Atmosphere”
  heic1603 — Science Release, Hubble Space Telescope News, ESA/Hubble (February 16, 2016)
• Renyu Hu (Dr. Renyu Hu: Ph.D. in planetary science MIT (2013); M.S. Astrophysics, Tsinghua University (2009); Diplome d’Ingenieur, Ecole Centrale Paris (2009); B.S. Mathematics and Physics, Tsinghua University (2007))
• Renyu Hu, PhD
  Renyu Hu’s Homepage

² Statistics and minimizing errors:

• Wikipedia
  • Bayes’ theorem
  • Bayesian epistemology
  • Bayesian inference
  • Bayesian probability
  • Bayesian statistics
  • History of statistics
  • Pierre-Simon Laplace
  • Six Sigma
  • Thomas Bayes
• Bias During Analysis in a Six Sigma Project
  Management and Strategy Institute

³ Studying distant worlds:

• Wikipedia
  • 55 Cancri e (Janssen, transiting exoplanet, discovered 2004, via radial velocity detection method)
  • Absorption spectroscopy
  • Astrometry
  • Astronomical spectroscopy
  • Doppler spectroscopy (shows radial velocity)
  • History of spectroscopy
  • Infrared spectroscopy
  • Methods of detecting exoplanets
• Learning from starlight
  • “WASP-18 b and Other Wonderfully Weird WASP Worlds” (June 10, 2023)
    • This WASP World’s Winds: Weirdly Warped?

⁴ Stars, planets, research (plus a cartoon and a movie); this was not hard to find:

• Wikipedia
  • 55 Cancri (AKA Copernicus, Rho¹ Cancri, BD+28°1660 ….)
  • 55 Cancri b (Galileo, discovered 1996)
  • 55 Cancri c (Brahe, discovered 2002)
  • 55 Cancri d (Lipperhey, discovered 2002)
  • 55 Cancri e (Janssen, discovered 2004)
  • 55 Cancri f (Harriot, discovered 2005 (announced), 2007 (published))
  • Cancer (constellation)
  • Captain Planet and the Planeteers
  • Geoffrey Marcy
  • International_Astronomical_Union (IAU)
  • Iota Cancri (about 280 light-years away)
  • NameExoWorlds (AKA IAU NameExoWorlds) (started in 2014 and/or 2015)
  • Planetary system
  • R. Paul Butler
  • Red dwarf
  • Rho² Cancri (490 ± 20 light-years away)
  • The Fifth Element
• “First Detection of Super-Earth Atmosphere”
  heic1603 — Science Release, Hubble Space Telescope News, ESA/Hubble (February 16, 2016)
• Preprint drafts in Cornell University’s arXiv, a selection from the last dozen years
  • “A secondary atmosphere on the rocky Exoplanet 55 Cancri e”
    Renyu Hu, Aaron Bello-Arufe, Michael Zhang, Kimberly Paragas, Mantas Zilinskas, Christiaan van Buchem, Michael Bess, Jayshil Patel, Yuichi Ito, Mario Damiano, Markus Scheucher, Apurva V. Oza, Heather A. Knutson, Yamila Miguel, Diana Dragomir, Alexis Brandeker, Brice-Olivier Demory; Nature (May 8, 2024) (submitted May 8, 2024)
  • “The Transient Outgassed Atmosphere of 55 Cancri e”
    Kevin Heng (submitted August 11, 2023; The Astrophysical Journal Letters (October 10, 2023) (submitted August 11, 2023; last revised September 27, 2023 (this version, v2))
  • “A Case for an Atmosphere on Super-Earth 55 Cancri e”
    Isabel Angelo, Renyu Hu; Solar and Stellar Astrophysics (November 16, 2017) (submitted October 9, 2017)
  • “Detection of an atmosphere around the super-Earth 55 Cancri e”
    A. Tsiaras, M. Rocchetto, I. P. Waldmann, O. Venot, R. Varley, G. Morello, M. Damiano, G. Tinetti, E. J. Barton, S. N. Yurchenko, J. Tennyson; The Astrophysical Journal (March 24, 2016) (submitted November 28, 2015 (v1); last revised February 7, 2016 (this version, v2))
  • “Carbon and Oxygen Abundances in Cool Metal-rich Exoplanet Hosts: A Case Study of the C/O Ratio of 55 Cancri”
    Johanna K. Teske, Katia Cunha, Simon C. Schuler, Caitlin A. Griffith, Verne V. Smith; The Astrophysical Journal (November 12, 2013) (submitted on 24 Sep 2013)
  • “A Possible Carbon-rich Interior in Super-Earth 55 Cancri e”
    Nikku Madhusudhan, Kanani K. M. Lee, Olivier Mousis; The Astrophysical Journal (November 10, 2012) (submitted October 9, 2012)
• BD — Bonner Durchmusterung
  NASA’s HEASARC (High Energy Astrophysics Science Archive Research Center)

⁵ Planets and planetary systems:

• Wikipedia
  • 55 Cancri
  • HD 70642
  • HD 70642 b (a Jupiter analog, discovered 2003)
  • HIP 11915
  • HIP 11915 b (a Jupiter analog, discovered 2015)
  • Kepler-90 (AKA KOI-351, 2MASS J18574403+4918185, KIC 11442793, …)
  • Solar System
    • Comparison with extrasolar systems
• KOI-351 Overview
  NASA Exoplanet Archive, A service of NASA Exoplanet Science Institute

⁶ Planets, stars, and informed speculation:

• Wikipedia
  • 55 Cancri
  • 55 Cancri b (Galileo)
  • 55 Cancri c (Brahe)
  • 55 Cancri d (Lipperhey)
  • 55 Cancri e (Janssen)
  • 55 Cancri f (Harriot)
  • Formation and evolution of the Solar System
  • K-type main-sequence star
  • Main sequence
  • Metallicity
  • Methods of detecting exoplanets
  • Solar analog
  • Solar System
  • Stellar classification
    • Spectral types
  • Subgiant
  • Super-Earth
• Preprint drafts in Cornell University’s arXiv
  • “A Possible Carbon-rich Interior in Super-Earth 55 Cancri e”
    Nikku Madhusudhan, Kanani K. M. Lee, Olivier Mousis; The Astrophysical Journal (November 10, 2012) (submitted October 9, 2012)
  • “55 Cancri: Stellar Astrophysical Parameters, a Planet in the Habitable Zone, and Implications for the Radius of a Transiting Super-Earth”
    Kaspar von Braun, Tabetha S. Boyajian, Theo A. ten Brummelaar, Stephen R. Kane, Gerard T. van Belle, David R. Ciardi, Sean N. Raymond, Mercedes Lopez-Morales, Harold A. McAlister, Gail Schaefer, Stephen T. Ridgway, Laszlo Sturmann, Judit Sturmann, Russel White, Nils H. Turner, Chris Farrington, P.J. Goldfinger; The Astrophysical Journal (September 26, 2011) (submitted June 6, 2011; last revised July 22, 2011 (this version, v2)
  • “Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics”
    Eric E. Mamajek, Lynne A. Hillenbrand; The Astrophysical Journal (November 10, 2008) (submitted July 10, 2008)

⁷ Elements, compounds, and abiotic processes:

• Wikipedia
  • Abiotic component
  • Abundance of the chemical elements
  • Biosignature (“…may require copy editing for grammar, style, cohesion, tone, or spelling….”)
  • Carbon
  • Earth
  • Hydrogen
  • James Webb Space Telescope
  • Life on Venus
  • Magma ocean
  • MIRI (Mid-Infrared Instrument)
  • Moon
  • NIRCam (Near-InfraRed Camera)
  • Oxygen
  • Organophosphine
  • Phosphine
  • Phosphorus
  • Terrestrial planet
• Preprint drafts in Cornell University’s arXiv
  • “A secondary atmosphere on the rocky Exoplanet 55 Cancri e”
    Renyu Hu, Aaron Bello-Arufe, Michael Zhang, Kimberly Paragas, Mantas Zilinskas, Christiaan van Buchem, Michael Bess, Jayshil Patel, Yuichi Ito, Mario Damiano, Markus Scheucher, Apurva V. Oza, Heather A. Knutson, Yamila Miguel, Diana Dragomir, Alexis Brandeker, Brice-Olivier Demory; Nature (May 8, 2024) (submitted May 8, 2024) via arXiv, Cornell University
  • “Measured Spin-Orbit Alignment of Ultra-Short Period Super-Earth 55 Cancri e”
    Lily L. Zhao, Vedad Kunovac, John M. Brewer, Joe Llama, Sarah C. Millholland, Christina Hedges, Andrew E. Szymkowiak, Rachael M. Roettenbacher, Samuel H. C. Cabot, Sam A. Weiss, Debra A. Fischer; Nature Astronomy (February 2023) (submitted December 7, 2022; last revised 9 Dec 2022 (this version, v2)) via arXiv, Cornell University
• Looking below the visible spectrum
  • “Supernova Remnant Cassiopeia A: Cool Images of Hot Gas” (December 16, 2023)
    • Transposing the Invisible: Infrared Astronomy

⁸ An exoplanet, the news, and science:

• Wikipedeia
  • 55 Cancri e (Janssen)
  • Mint (newspaper)
  • News18 India (“…needs additional citations for verification….”)
• 55 Cancri e
  Eyes on Exoplanets, NASA
• “A Possible Carbon-rich Interior in Super-Earth 55 Cancri e”
  Nikku Madhusudhan, Kanani K. M. Lee, Olivier Mousis; preprint draft of paper published in The Astrophysical Journal (November 10, 2012) (submitted October 9, 2012) via arXiv, Cornell University

⁹ Science and informed speculation:

• Wikipedia
  • 55 Cancri
  • 55 Cancri e (Janssen)
  • Abundance of the chemical elements
  • Carbon planet
  • Hypothetical astronomical object
    • Hypothetical planet types
  • Iron planet (a planet with an iron-rich core with little or no mantle, like Mercury)
  • Metal
  • Nikku Madhusudhan
  • Oxygen
  • Phases of ice
  • Rock (geology)
  • Silicate
  • Silicon
  • Silicone carbide
  • Terrestrial planet
  • Titan (moon)
• Preprint drafts in Cornell University’s arXiv
  • “A Possible Carbon-rich Interior in Super-Earth 55 Cancri e”
    Nikku Madhusudhan, Kanani K. M. Lee, Olivier Mousis; preprint draft of paper published in The Astrophysical Journal (November 10, 2012) (submitted October 9, 2012) via arXiv, Cornell University
  • “Extrasolar Carbon Planets”
    Marc J. Kuchner, S. Seager; submitted to The Astrophysical Journal (no publication date found) (submitted on April 8, 2005 (v1), last revised 2 May 2, 2005 (this version, v2)) via arXiv, Cornell University
• “A Flurry of Exoplanet Discoveries”
  Robert Naeye, Sky & Telescope (February 10, 2005)