TRAPPIST-1 Planets Probably Rich in Water

Artist’s impressions of the TRAPPIST-1 planetary system 

Artist’s impressions of the TRAPPIST-1 planetary system 

Artist’s impressions of the TRAPPIST-1 planetary system 

 
The ultracool dwarf star TRAPPIST-1 in the constellation of Aquarius 

 
The sizes, masses and temperatures of the seven TRAPPIST-1 planets and others

 
Properties of the seven TRAPPIST-1 planets compared to other known planets 

Properties of the seven TRAPPIST-1 planets 

Comparison of the properties of the seven TRAPPIST-1 planets 

Comparison of the TRAPPIST-1 system and the Solar System


Videos
 
ESOcast 150 Light: Planets around TRAPPIST-1 Probably Rich in Water

ESOcast 150 Light: Planets around TRAPPIST-1 Probably Rich in Water

Planet Parade: the seven planets of TRAPPIST-1

Planet Parade: the seven planets of TRAPPIST-1


First glimpse of what Earth-sized exoplanets are made of

A new study has found that the seven planets orbiting the nearby ultra-cool dwarf star TRAPPIST-1 are all made mostly of rock, and some could potentially hold more water than Earth. The planets’ densities, now known much more precisely than before, suggest that some of them could have up to 5 percent of their mass in the form of water — about 250 times more than Earth’s oceans. The hotter planets closest to their parent star are likely to have dense steamy atmospheres and the more distant ones probably have icy surfaces. In terms of size, density and the amount of radiation it receives from its star, the fourth planet out is the most similar to Earth. It seems to be the rockiest planet of the seven, and has the potential to host liquid water.
Planets around the faint red star TRAPPIST-1, just 40 light-years from Earth, were first detected by the TRAPPIST-South telescope at ESO’s La Silla Observatory in 2016. In the following year further observations from ground-based telescopes, including ESO’s Very Large Telescope and NASA’s Spitzer Space Telescope, revealed that there were no fewer than seven planets in the system, each roughly the same size as the Earth. They are named TRAPPIST-1b,c,d,e,f,g and h, with increasing distance from the central star [1].
Further observations have now been made, both from telescopes on the ground, including the nearly-complete SPECULOOS facility at ESO’s Paranal Observatory, and from NASA’s Spitzer Space Telescope and the Kepler Space Telescope.  A team of scientists led by Simon Grimm at the University of Bern in Switzerland have now applied very complex computer modelling methods to all the available data and have determined the planets’ densities with much better precision than was possible before [2].
Simon Grimm explains how the masses are found: “The TRAPPIST-1 planets are so close together that they interfere with each other gravitationally, so the times when they pass in front of the star shift slightly. These shifts depend on the planets’ masses, their distances and other orbital parameters. With a computer model, we simulate the planets’ orbits until the calculated transits agree with the observed values, and hence derive the planetary masses.”
Team member Eric Agol comments on the significance: “A goal of exoplanet studies for some time has been to probe the composition of planets that are Earth-like in size and temperature. The discovery of TRAPPIST-1 and the capabilities of ESO’s facilities in Chile and the NASA Spitzer Space Telescope in orbit have made this possible — giving us our first glimpse of what Earth-sized exoplanets are made of!”
The measurements of the densities, when combined with models of the planets’ compositions, strongly suggest that the seven TRAPPIST-1 planets are not barren rocky worlds. They seem to contain significant amounts of volatile material, probably water [3], amounting to up to 5% the planet’s mass in some cases — a huge amount; by comparison the Earth has only about 0.02% water by mass!
“Densities, while important clues to the planets’ compositions, do not say anything about habitability. However, our study is an important step forward as we continue to explore whether these planets could support life,” said Brice-Olivier Demory, co-author at the University of Bern.

TRAPPIST-1b and c, the innermost planets, are likely to have rocky cores and be surrounded by atmospheres much thicker than Earth’s. TRAPPIST-1d, meanwhile, is the lightest of the planets at about 30 percent the mass of Earth. Scientists are uncertain whether it has a large atmosphere, an ocean or an ice layer.
Scientists were surprised that TRAPPIST-1e is the only planet in the system slightly denser than Earth, suggesting that it may have a denser iron core and that it does not necessarily have a thick atmosphere, ocean or ice layer. It is mysterious that TRAPPIST-1e appears to be so much rockier in its composition than the rest of the planets. In terms of size, density and the amount of radiation it receives from its star, this is the planet that is most similar to Earth.

TRAPPIST-1f, g and h are far enough from the host star that water could be frozen into ice across their surfaces. If they have thin atmospheres, they would be unlikely to contain the heavy molecules that we find on Earth, such as carbon dioxide.

“It is interesting that the densest planets are not the ones that are the closest to the star, and that the colder planets cannot harbour thick atmospheres,” notes Caroline Dorn, study co-author based at the University of Zurich, Switzerland.
The TRAPPIST-1 system will continue to be a focus for intense scrutiny in the future with many facilities on the ground and in space, including ESO’s Extremely Large Telescope and the NASA/ESA/CSA James Webb Space Telescope.
Astronomers are also working hard to search for further planets around faint red stars like TRAPPIST-1. As team member Michaël Gillon explains [4]: “This result highlights the huge interest of exploring nearby ultracool dwarf stars — like TRAPPIST-1 — for transiting terrestrial planets. This is exactly the goal of SPECULOOS, our new exoplanet search that is about to start operations at ESO’s Paranal Observatory in Chile.”


 
Notes

 [1] The planets were discovered using the ground-based TRAPPIST-South at ESO’s La Silla Observatory in Chile; TRAPPIST-North in Morocco; the orbiting NASA Spitzer Space Telescope; ESO’s HAWK-I instrument on the Very Large Telescope at the Paranal Observatory in Chile; the 3.8-metre UKIRT in Hawaii; the 2-metre Liverpool and 4-metre William Herschel telescopes on La Palma in the Canary Islands; and the 1-metre SAAO telescope in South Africa.

[2] Measuring the densities of exoplanets is not easy. You need to find out both the size of the planet and its mass. The TRAPPIST-1 planets were found using the transit method — by searching for small dips in the brightness of the star as a planet passes across its disc and blocks some light. This gives a good estimate of the planet’s size. However, measuring a planet’s mass is harder — if no other effects are present planets with different masses have the same orbits and there is no direct way to tell them apart. But there is a way in a multi-planet system — more massive planets disturb the orbits of the other planets more than lighter ones. This in turn affects the timing of transits. The team led by Simon Grimm have used these complicated and very subtle effects to estimate the most likely masses for all seven planets, based on a large body of timing data and very sophisticated data analysis and modelling.

[3] The models used also consider alternative volatiles, such as carbon dioxide. However, they favour water, as vapour, liquid or ice, as the most likely largest component of the planets’ surface material as water is the most abundant source of volatiles for solar abundance protoplanetary discs.

[4] The SPECULOOS survey telescopes facility is nearly complete at ESO’s Paranal Observatory.


 
More Information


This research was presented in a paper entitled “The nature of the TRAPPIST-1 exoplanets”, by S. Grimm et al., to appear in the journal Astronomy & Astrophysics.

The team is composed of Simon L. Grimm (University of Bern, Center for Space and Habitability, Bern, Switzerland) , Brice-Olivier Demory (University of Bern, Center for Space and Habitability, Bern, Switzerland), Michaël Gillon (Space Sciences, Technologies and Astrophysics Research Institute, Université de Liège, Liège, Belgium), Caroline Dorn (University of Bern, Center for Space and Habitability, Bern, Switzerland; University of Zurich, Institute of Computational Sciences, Zurich, Switzerland), Eric Agol (University of Washington, Seattle, Washington, USA; NASA Astrobiology Institute’s Virtual Planetary Laboratory, Seattle, Washington, USA; Institut d’Astrophysique de Paris, Paris, France), Artem Burdanov (Space Sciences, Technologies and Astrophysics Research Institute, Université de Liège, Liège, Belgium), Laetitia Delrez (Cavendish Laboratory, Cambridge, UK; Space Sciences, Technologies and Astrophysics Research Institute, Université de Liège, Liège, Belgium), Marko Sestovic (University of Bern, Center for Space and Habitability, Bern, Switzerland), Amaury H.M.J. Triaud (Institute of Astronomy, Cambridge, UK; University of Birmingham, Birmingham, UK), Martin Turbet (Laboratoire de Météorologie Dynamique, IPSL, Sorbonne Universités, UPMC Univ Paris 06, CNRS, Paris, France), Émeline Bolmont (Université Paris Diderot, AIM, Sorbonne Paris Cité, CEA, CNRS, Gif-sur-Yvette, France), Anthony Caldas (Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, Pessac, France), Julien de Wit (Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA), Emmanuël Jehin (Space Sciences, Technologies and Astrophysics Research Institute, Université de Liège, Liège, Belgium), Jérémy Leconte (Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, Pessac, France), Sean N. Raymond (Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, Pessac, France), Valérie Van Grootel (Space Sciences, Technologies and Astrophysics Research Institute, Université de Liège, Liège, Belgium), Adam J. Burgasser (Center for Astrophysics and Space Science, University of California San Diego, La Jolla, California, USA), Sean Carey (IPAC, Calif. Inst. of Technology, Pasadena, California, USA), Daniel Fabrycky (Department of Astronomy and Astrophysics, Univ. of Chicago, Chicago, Illinois, USA), Kevin Heng (University of Bern, Center for Space and Habitability, Bern, Switzerland), David M. Hernandez (Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA), James G. Ingalls (IPAC, Calif. Inst. of Technology, Pasadena, California, USA), Susan Lederer (NASA Johnson Space Center, Houston, Texas, USA), Franck Selsis (Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, Pessac, France) and Didier Queloz (Cavendish Laboratory, Cambridge, UK).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and by Australia as a strategic partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.


 
Links


Contacts

Simon Grimm
SAINT-EX Research Group, University of Bern, Center for Space and Habitability
Bern, Switzerland
Tel: +41 31 631 3995
Email:
simon.grimm@csh.unibe.ch

Brice-Olivier Demory
SAINT-EX Research Group, University of Bern, Center for Space and Habitability
Bern, Switzerland
Tel: +41 31 631 5157
Email:
brice.demory@csh.unibe.ch

Richard Hook
ESO Public Information Officer
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email:
rhook@eso.org

Source: ESO/News

Russians Move from Longest Spacewalk to Shortest Cargo Delivery

ISS – Expedition 54 Mission patch.

February 5, 2018

Fresh off a record-breaking spacewalk last week, the International Space Station program is preparing for its first docking of a cargo craft in just two orbits. Back inside the orbital lab, the Expedition 54 crew researched how microgravity affects muscles to help humans on Earth.

Cosmonauts Alexander Misurkin and Anton Shkaplerov wrapped up the longest spacewalk in Russian space program history at eight hours and 13 minutes on Friday. The two station residents worked over the weekend stowing spacewalk tools, cleaning the Pirs airlock and checking their Orlan spacesuits.

Image above: A Russian spacewalker is seen in an Orlan spacesuit with blue stripes (center image) working outside the Zvezda service module during the longest spacewalk in Russian space program history on Feb. 2, 2018. Image Credit: NASA TV.

The Russian Federal Space Agency is now preparing for the launch Sunday of its unpiloted Progress 69 resupply ship at 3:58 a.m. EST. After its launch from the Baikonur Cosmodrome in Kazakhstan, the cargo craft will take two orbits around the Earth before automatically docking to the aft end of the Zvezda service module.

Astronauts Scott Tingle and Norishige Kanai observed mice on the space station being treated with a drug that may slow or reverse muscle atrophy. The rodents are housed in a special microgravity habitat for up to two months with results of the study helping scientists design therapies for humans with muscle-related ailments.

Related links:
Mice on the space station: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7423

Expedition 54: https://www.nasa.gov/mission_pages/station/expeditions/expedition54/index.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Image (mentioned), Text, Credits: NASA/Mark Garcia.

Best regards, Orbiter.ch

New Clues to TRAPPIST-1 Planet Compositions, Atmospheres

NASA – Hubble Space Telescope patch / NASA – Spitzer Space Telescope patch.

Feb. 5, 2018

Image above: This artist’s concept shows what the TRAPPIST-1 planetary system may look like, based on available data about the planets’ diameters, masses and distances from the host star, as of February 2018. Image Credits: NASA/JPL-Caltech.

In the year since NASA announced the seven Earth-sized planets of the TRAPPIST-1 system, scientists have been working hard to better understand these enticing worlds just 40 light-years away. Thanks to data from a combination of space- and ground-based telescopes, we know more about TRAPPIST-1 than any other planetary system besides our solar system.

A new study in the journal Astronomy and Astrophysics, using data from NASA’s Spitzer and Kepler space telescopes, offers the best-yet picture of what these planets are made of. They used the telescope observations to calculate the densities more precisely than ever, then used those numbers in complex simulations. Researchers determined that all of the planets are mostly made of rock. Additionally, some have up to 5 percent of their mass in water, which is 250 times more than the oceans on Earth.

Hubble Observes Atmospheres of TRAPPIST-1 Exoplanets in the Habitable Zone

Video above: Astronomers using the Hubble Space Telescope have conducted the first spectroscopic survey of Earth-sized planets in the TRAPPIST-1 system’s habitable zone. Video Credits: NASA’s Goddard Space Flight Center.

The form that water takes on TRAPPIST-1 planets would depend on how much heat they receive from their ultra-cool dwarf star, which is only about 9 percent as massive as our Sun. Planets closest to the star are more likely to host water in the form of atmospheric vapor, while those farther away may have water frozen on their surfaces as ice. TRAPPIST-1e is the rockiest planet of them all, but is still believed to have the potential to host some liquid water.

The question of the planets’ atmospheres is also important for understanding whether liquid water could be present on these surfaces — an essential ingredient for habitability. NASA’s Hubble Space Telescope has now surveyed six of the seven TRAPPIST-1 planets, and new results on four of them are published in Nature Astronomy. In the new study, Hubble reveals that at least three of the TRAPPIST-1 planets — d, e, and f — do not seem to contain puffy, hydrogen-rich atmospheres like the gas giants of our own solar system. Hydrogen is a greenhouse gas, and would make these close-in planets hot and inhospitable to life.

In 2016, Hubble observations also did not find evidence for hydrogen atmospheres in c and d. These results and the new ones, instead, favor more compact atmospheres like those of Earth, Venus and Mars. Additional observations are needed to determine the hydrogen content of planet g’s atmosphere.

Both studies help pave the way for NASA’s James Webb Space Telescope, scheduled to launch in 2019. Webb will probe deeper into the planetary atmospheres, searching for heavier gases such as carbon dioxide, methane, water and oxygen. The presence of such elements could offer hints of whether life could be present, or if the planets are habitable.

TRAPPIST-1 is named for the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile, which discovered two of the seven TRAPPIST planets we know of today — announced in February 2016. NASA’s Spitzer Space Telescope, in collaboration with ground-based telescopes, confirmed these planets and uncovered the other five in the system.

For more information about TRAPPIST-1, visit: https://exoplanets.nasa.gov/trappist1

Hubble Space Telescope: https://www.nasa.gov/mission_pages/hubble/main/index.html

Kepler and K2: https://www.nasa.gov/mission_pages/kepler/main/index.html

Spitzer Space Telescope: http://www.nasa.gov/mission_pages/spitzer/main/index.html

Image (mentioned), Video (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Elizabeth Landau.

Best regards, Orbiter.ch