Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Diamond 'super-earth' may not be quite as precious, UA graduate student finds

09.10.2013
An alien world reported to be the first known planet to consist largely of diamond appears less likely to be of such precious nature, according to a new analysis led by UA graduate student Johanna Teske

A planet 40 light years from our solar system, believed to be the first-ever discovered planet to consist largely of diamond, may in fact be of less exquisite nature, according to new research led by University of Arizona astronomy graduate student Johanna Teske.


In the sky with diamonds? A so-called super-earth, planet 55 Cancri e was believed to be the first known planet to consist largely of diamond, due in part to the high carbon-to-oxygen ratio of its host star.

Credit: Haven Giguere/Yale University/NASA

Revisiting public data from previous telescope observations, Teske's team analyzed the available data in more detail and concluded that carbon – the chemical element diamonds are made of – appears to be less abundant in relation to oxygen in the planet's host star – and by extension, perhaps the planet – than was suggested by a study of the host star published in 2010.

"The 2010 paper found that '55 Cancri,' a star that hosts five planets, has a carbon-to-oxygen ratio greater than one," Teske said. "This observation helped motivate a paper last year about the innermost planet of the system, the 'super-Earth' 55 Cancri e. Using observations of the planet's mass and radius to create models of its interior that assumed the same carbon-to-oxygen ratio of the star, the 2012 paper suggested the planet contains more carbon than oxygen."

"However, our analysis makes this seem less likely because the host star doesn't appear as carbon-rich as previously thought," Teske said.

Observations obtained in 2010, together with simulations astronomers use to model a planet's interior based on data like radius, mass and orbital velocity, had yielded a carbon to oxygen ratio greater than one, in other words, an alien world based on carbon instead of oxygen as most planets are in our solar system, including Earth.

"The sun only has about half as much carbon as oxygen, so a star or a planet with a higher ratio between the two elements, particularly a planet with more carbon than oxygen, is interesting and different from what we have in our solar system," explained Teske, who is graduating this spring with a doctorate from the UA's Department of Astronomy and Steward Observatory.

Based on the previous results, it was suggested that the "diamond planet" is a rocky world with a surface of graphite surrounding a thick layer of diamond instead of water and granite like Earth.

The new research by Teske and collaborators, to be published in the Astrophysical Journal and available online, calls this conclusion in question, making it less likely a hypothetical space probe sent to sample the planet's innards would dig up anything sparkling.

Teske's group found that the planet's host star contains almost 25 percent more oxygen than carbon, about mid way between the Sun and what the previous study suggested.

"In theory, 55 Cancri e could still have a high carbon to oxygen ratio and be a diamond planet, but the host star does not have such a high ratio," Teske said. "So in terms of the two building blocks of information used for the initial 'diamond-planet' proposal – the measurements of the exoplanet and the measurements of the star – the measurements of the star no longer verify that."

A so-called super-Earth boasting about twice the Earth's diameter and eight times Earth's mass, the "diamond planet," whose official designation is 55 Cancri e, is the smallest member of a five-planet system located in the constellation Cancer. 55 Cancri e races around its host star at such close distance that one year lasts only 18 hours and its surface temperature is more than 3,000 degrees Fahrenheit.

"With rocky worlds like 55 Cancri e, researchers use measurements of a planet's radius, mass and density and basic physical equations governing the internal structure of solid planets to calculate possible compositions of the planet's interior," Teske said.

"This planet is probably rocky or has a large rocky component," she said. "We don't really know if it has an atmosphere."

Since astronomers can't probe the makeups of stars and planets directly, they rely on indirect observational methods such as absorption spectra; each chemical element absorbs light at different wavelengths, in a characteristic pattern that can be used as a fingerprint of that element. By analyzing the absorption spectra of starlight passing through a star's atmosphere, it is possible to deduce what elements are present in the star's atmosphere.

"Instead of using the same absorption lines in the spectrum of the host star as the previous study of 55 Cancri, we looked at more lines of carbon and more lines of oxygen," Teske said. "We find that because this particular host star is cooler than our sun and more metal-rich, the single oxygen line analyzed in the previous study to determine the star's oxygen abundance is more prone to error."

Teske instead relied on several different indicators of the oxygen abundance that were not considered previously. "Averaging all of these measurements together gives us a more complete picture of the oxygen abundance in the star."

Teske pointed out that the 'diamond planet' results hinge on the presumption that a star's composition bears some relation to the composition of its planets, a notion grounded in the idea that planets form from the same material as their host stars. However, as astronomers discover more and more extrasolar systems, a one-size-fits-all formula becomes less likely.

"We still don't know whether our solar system is common or uncommon in the universe," Teske said, "because many of the systems that we are finding have giant gas planets closer to the star, unlike our system where rocky planets dominate the inner orbits and gas giants occur further out."

Given there are so many processes – most of which are not fully understood – happening in a planet-forming disk that could influence the composition of planets, Teske said: "At this point, I would honestly be surprised if there was a one-to-one correlation."

"The compositions of planets and stars don't always match," she said, explaining that in a swirling disk of dust and gas giving birth to a star and planets, "you can have pockets where there is a lot of water, meaning an enhancement of oxygen. Or places where water has frozen out, leaving behind carbon species as the dominant gas molecules. So the planets that are accreting gas at those locations in the disk could be more carbon-rich instead of oxygen-rich."

Therefore, room for uncertainty remains, according to the researchers.

"Depending on where 55 Cancri e formed in the protoplanetary disk, its carbon-to-oxygen ratio could differ from that of the host star," Teske said. "It could be higher or lower. But based on what we know at this point, 55 Cancri e is more of a 'diamond in the rough.'"

The study was co-authored by Katia Cunha of Steward Observatory and Observatorio Nacional in Rio de Janeiro, Brazil; Simon Schuler of the University of Tampa, Fla.; Caitlin Griffith of the UA Lunar and Planetary Laboratory; and Verne Smith of the National Optical Astronomy Observatory in Tucson. Teske and Griffith were supported by NASA's Planetary Atmospheres Program.

The research paper is published at http://arxiv.org/abs/1309.6032

The previous studies mentioned in this article are available here:
2010 study by Delgado Mena et al.:
http://m.iopscience.iop.org/0004-637X/725/2/2349?rel=sem&relno=3
2012 study by Madhusudhan, Lee and Mousis:
http://inspirehep.net/record/1190108?ln=en

Daniel Stolte | University of Arizona
Further information:
http://www.arizona.edu

More articles from Physics and Astronomy:

nachricht Ultra-compact phase modulators based on graphene plasmons
27.06.2017 | ICFO-The Institute of Photonic Sciences

nachricht Smooth propagation of spin waves using gold
26.06.2017 | Toyohashi University of Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Touch Displays WAY-AX and WAY-DX by WayCon

27.06.2017 | Power and Electrical Engineering

Drones that drive

27.06.2017 | Information Technology

Ultra-compact phase modulators based on graphene plasmons

27.06.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>