<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><font size="4" class="">Hi All,</font><div class=""><font size="4" class=""> I hope you have had a wonderful week and will look forward to the weekend….for those in the US, there will be lots of Halloween parties…everyone dressing up and so many of the costumes are awesome… many of the houses are decorated and lots of pumpkins floating around….it really is a fun time, then on Monday I know many of the teachers and the kids will dress up too….Monday night will be the Trick or Treaters who will be out looking for Treats….also tomorrow will be the return of the crew from the ISS…you can watch the events on NASA TV <strong style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class=""><a href="http://www.nasa.gov/nasatv" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 116, 189); text-decoration: none;" class="">http://www.nasa.gov/nasatv</a>. </strong><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class="">Wishing you all a wonderful weekend…we have to remember to do our best, enjoy everything we do, live in </span>the present, let those we care about most know, smile, and have fun…Gabe</font></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br style="font-family: Arial, Helvetica, sans-serif; font-size: 18px;" class=""><b style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Arial, Helvetica, sans-serif; font-size: 18px;" class="">NASA Television to Air Return of Three Space Station Crew Members</b><br style="font-family: Arial, Helvetica, sans-serif; font-size: 18px;" class=""><table align="center" width="687" cellpadding="1" style="margin: 0px 0px 10px; padding: 0px; border: 1px solid rgb(190, 191, 185); vertical-align: baseline; border-collapse: collapse; border-spacing: 0px; width: 708px; font-size: 0.923em; font-family: Arial, Helvetica, sans-serif;" class=""><tbody style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class=""><tr style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class=""><td style="margin: 0px; padding: 10px; border: 1px solid rgb(230, 230, 230); vertical-align: middle; font-size: 14px;" class=""><div class="dnd-drop-wrapper" style="margin: 0px 0px 9px; padding: 0px; border: 0px; vertical-align: baseline;"><a href="http://www.nasa.gov/sites/default/files/thumbnails/image/m16-126.jpg" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 116, 189); text-decoration: none;" class=""><img typeof="foaf:Image" src="http://www.nasa.gov/sites/default/files/styles/full_width/public/thumbnails/image/m16-126.jpg" width="687px" height="auto" alt="Expedition 49 crew members Kate Rubins of NASA, Anatoly Ivanishin of Roscosmos and Takuya Onishi of the Japan Aerospace Agency." title="" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class=""></a></div><div class="dnd-legend-wrapper" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><div class="caption" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; font-size: 10px;">Expedition 49 crew members Kate <span class="scayt-misspell-word" data-scayt-lang="en_US" data-scayt-word="Rubins" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Rubins</span> of NASA, <span class="scayt-misspell-word" data-scayt-lang="en_US" data-scayt-word="Anatoly" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Anatoly</span> <span class="scayt-misspell-word" data-scayt-lang="en_US" data-scayt-word="Ivanishin" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Ivanishin</span> of the Russian space agency <span class="scayt-misspell-word" data-scayt-lang="en_US" data-scayt-word="Roscosmos" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Roscosmos</span> and <span class="scayt-misspell-word" data-scayt-lang="en_US" data-scayt-word="Takuya" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Takuya</span> <span class="scayt-misspell-word" data-scayt-lang="en_US" data-scayt-word="Onishi" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Onishi</span> of the Japan Aerospace Exploration Agency are concluding a 115-day mission of science and research aboard the International Space Station and are set to return to Earth Oct. 29, 2016.</div><b style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class=""><i style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class=""><div class="credits" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; font-size: 10px;">Credits: NASA</div></i></b><div class="link" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"></div></div></td></tr></tbody></table><p style="margin: 1em 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Arial, Helvetica, sans-serif; font-size: 18px;" class="">Three crew members on the International Space Station are scheduled to depart the orbital outpost Saturday, Oct. 29, with coverage of activities beginning the day before on NASA Television and the agency’s website. Expedition 49 Commander Anatoly Ivanishin of the Russian space agency Roscosmos, and Flight Engineers Kate Rubins of NASA and Takuya Onishi of the Japan Aerospace Exploration Agency, will undock their Soyuz spacecraft from the space station at 8:37 p.m. EDT Saturday and land in Kazakhstan at 11:59 p.m. (9:59 a.m. Oct. 30, Kazakhstan time). Their return will wrap up 115 days in space for the crew since their launch in July. Together, the Expedition 49 crew members pursued hundreds of experiments in biology, biotechnology, physical science and Earth science aboard the orbiting laboratory. NASA Television will air coverage of the departure and landing activities at the following dates and times:</p><div style="margin: 1em 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Arial, Helvetica, sans-serif; font-size: 18px;" class="">Friday, Oct. 28:</div><ul style="margin: 0.25em 0px 0.25em 1.5em; padding: 0px; border: 0px; vertical-align: baseline; list-style-image: none; list-style-position: initial; font-family: Arial, Helvetica, sans-serif; font-size: 18px;" class=""><li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class="">3:30 p.m. – Change of command ceremony in which Ivanishin hands over station command to NASA’s Shane Kimbrough</li></ul><div style="margin: 1em 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Arial, Helvetica, sans-serif; font-size: 18px;" class="">Saturday, Oct. 29:</div><ul style="margin: 0.25em 0px 0.25em 1.5em; padding: 0px; border: 0px; vertical-align: baseline; list-style-image: none; list-style-position: initial; font-family: Arial, Helvetica, sans-serif; font-size: 18px;" class=""><li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class="">4:45 p.m. – Farewell and hatch closure coverage (hatch closure scheduled at 5:15 p.m.)</li><li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class="">8:15 p.m. – Undocking coverage (undocking scheduled at 8:37 p.m.)</li><li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class="">10:45 p.m. – Deorbit burn and landing coverage (deorbit burn scheduled at 11:06 p.m., with landing at 11:59 p.m.)</li></ul><div style="margin: 1em 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Arial, Helvetica, sans-serif; font-size: 18px;" class="">Sunday, Oct. 30:</div><ul style="margin: 0.25em 0px 0.25em 1.5em; padding: 0px; border: 0px; vertical-align: baseline; list-style-image: none; list-style-position: initial; font-family: Arial, Helvetica, sans-serif; font-size: 18px;" class=""><li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class="">2 a.m. – Video File of hatch closure, undocking and landing activities</li><li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class="">1 p.m. – Video File of landing and post-landing activities and post-landing interview with Rubins and Onishi in Kazakhstan</li></ul><div style="margin: 1em 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Arial, Helvetica, sans-serif; font-size: 18px;" class="">At the time of undocking, Expedition 50 will begin aboard the station under the command of NASA astronaut Shane Kimbrough. Along with his crewmates Sergey Ryzhikov and Andrey Borisenko of Roscosmos, the three-person crew will operate the station for three weeks until the arrival of three new crew members. Peggy Whitson of NASA, Thomas Pesquet of ESA (European Space Agency) and Oleg Novitsky of Roscosmos are scheduled to launch in November from Baikonur, Kazakhstan. Check out the full NASA TV schedule and video streaming information at: <strong style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class=""><a href="http://www.nasa.gov/nasatv" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 116, 189); text-decoration: none;" class="">http://www.nasa.gov/nasatv</a> </strong>Keep up with the International Space Station, and its research and crews, at: <strong style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;" class=""><a href="http://www.nasa.gov/station" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 116, 189); text-decoration: none;" class="">http://www.nasa.gov/station</a></strong></div><div style="margin: 1em 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Arial, Helvetica, sans-serif; font-size: 18px;" class=""><br class=""></div><div style="margin: 1em 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Arial, Helvetica, sans-serif;" class=""><div class="title-bar" style="font-size: 14px; box-sizing: border-box; margin: 2em 0px; color: rgb(51, 51, 51); font-family: 'Titillium Web', 'Helvetica Neue', Helvetica, Arial, sans-serif;"><div class="title-wrap" style="box-sizing: border-box; width: 738.75px; padding: 0px;"><h1 class="title" style="box-sizing: border-box; margin: 0px; font-family: inherit; line-height: 1.1; color: inherit; font-size: 2.2em;">A Dead Star's Ghostly Glow</h1></div></div><section id="ember915" class="opened collapsible ember-view" style="box-sizing: border-box; max-height: none; overflow-y: hidden; color: rgb(51, 51, 51); font-family: 'Titillium Web', 'Helvetica Neue', Helvetica, Arial, sans-serif;"><div class="text" style="box-sizing: border-box; color: rgb(0, 0, 0); font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;"><p style="font-size: 1em; box-sizing: border-box; margin: 0px 0px 15px; -webkit-font-smoothing: inherit; line-height: 1.4em;" class="">The eerie glow of a dead star, which exploded long ago as a supernova, reveals itself in this NASA Hubble Space Telescope image of the Crab Nebula. But don't be fooled. The ghoulish-looking object still has a pulse. Buried at its center is the star's tell-tale heart, which beats with rhythmic precision.</p><div class="type-image dnd-atom-wrapper context-full_width" style="box-sizing: border-box; clear: both; display: table; margin: 0px auto 2em;"><div class="dnd-drop-wrapper" style="box-sizing: border-box;"><a href="https://www.nasa.gov/sites/default/files/thumbnails/image/hubblehs201637alargeweb-1.jpg" style="box-sizing: border-box; color: rgb(66, 139, 202); text-decoration: none; background-position: 0px 0px; background-repeat: initial initial;" class=""><font size="4" class=""><img typeof="foaf:Image" width="640" height="416" alt="wispy green swirling through space" title="" style="box-sizing: border-box; border: 0px; vertical-align: middle; max-width: 100%; margin-bottom: 10px;" apple-inline="yes" id="90ABBBF7-3427-4BF7-A3FD-8853CF85D3F8" apple-width="yes" apple-height="yes" src="cid:BC514B4A-968D-417A-AEC2-0BD06891BB87" class=""></font></a></div><div class="dnd-legend-wrapper" style="box-sizing: border-box;"><div class="caption" style="box-sizing: border-box;"><font size="4" class="">Astronomers discovered a real "tell-tale heart" in space, 6,500 light-years from Earth. The "heart" is the crushed core of a long-dead star, called a neutron star, which exploded as a supernova and is now still beating with rhythmic precision. Evidence of its heartbeat are rapid-fire, lighthouse-like pulses of energy from the fast-spinning neutron star. The stellar relic is embedded in the center of the Crab Nebula, the expanding, tattered remains of the doomed star.</font></div><div class="credits" style="box-sizing: border-box; font-style: italic; font-weight: 700;"><font size="4" class="">Credits: NASA and ESA, Acknowledgment: M. Weisskopf/Marshall Space Flight Center</font></div><div class="link" style="box-sizing: border-box; background-image: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-size: inherit; padding: 0px;"><font size="4" class=""><a href="" style="box-sizing: border-box; color: rgb(66, 139, 202); background-position: 0px 0px;" class=""></a></font></div></div></div><p style="box-sizing: border-box; margin: 0px 0px 15px; -webkit-font-smoothing: inherit; line-height: 1.4em;" class=""><font size="4" class="">The "heart" is the crushed core of the exploded star. Called a neutron star, it has about the same mass as the sun but is squeezed into an ultra-dense sphere that is only a few miles across and 100 billion times stronger than steel. The tiny powerhouse is the bright star-like object near the center of the image.</font></p><div class="type-image dnd-atom-wrapper context-side_image" style="box-sizing: border-box; margin: 0.5em 0px 3em 2em; max-width: 320px; float: right; clear: right; width: 320px;"><div class="dnd-drop-wrapper" style="box-sizing: border-box;"><a href="https://www.nasa.gov/sites/default/files/thumbnails/image/hs201637aanimatedgif.gif" style="box-sizing: border-box; color: rgb(66, 139, 202); text-decoration: none; background-position: 0px 0px; background-repeat: initial initial;" class=""><font size="4" class=""><img typeof="foaf:Image" width="320" height="213" alt="moving black and white image of supernova like ripples in pond" title="" style="box-sizing: border-box; border: 0px; vertical-align: middle; max-width: 100%; margin-bottom: 10px;" apple-inline="yes" id="FEC6F123-9B4A-49F1-A8AF-7F625FDED64C" apple-width="yes" apple-height="yes" src="cid:E4AB5C9B-7D15-48C7-A141-56FEDC39C64D" class=""></font></a></div><div class="dnd-legend-wrapper" style="box-sizing: border-box;"><div class="caption" style="box-sizing: border-box;"><br class=""></div><div class="credits" style="box-sizing: border-box; font-style: italic; font-weight: 700;"><font size="4" class="">Credits: NASA and ESA, Acknowledgment: J. Hester (Arizona State University)</font></div><div class="link" style="box-sizing: border-box; background-image: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-size: inherit; padding: 0px;"><font size="4" class=""><a href="" style="box-sizing: border-box; color: rgb(66, 139, 202); background-position: 0px 0px;" class=""></a></font></div></div></div><p style="box-sizing: border-box; margin: 0px 0px 15px; -webkit-font-smoothing: inherit; line-height: 1.4em;" class=""><font size="4" class="">This surviving remnant is a tremendous dynamo, spinning 30 times a second. The wildly whirling object produces a deadly magnetic field that generates an electrifying 1 trillion volts. This energetic activity unleashes wisp-like waves that form an expanding ring, most easily seen to the upper right of the pulsar.</font></p><div class="type-image dnd-atom-wrapper context-side_image" style="box-sizing: border-box; margin: 0.5em 0px 3em 2em; max-width: 320px; float: right; clear: right; width: 320px;"><div class="dnd-drop-wrapper" style="box-sizing: border-box;"><a href="https://www.nasa.gov/sites/default/files/thumbnails/image/spothubble-boilerplate.png" style="box-sizing: border-box; color: rgb(66, 139, 202); text-decoration: none; background-position: 0px 0px; background-repeat: initial initial;" class=""><font size="4" class=""><img typeof="foaf:Image" width="320" height="102" alt="#SpotHubble graphic" title="" style="box-sizing: border-box; border: 0px; vertical-align: middle; max-width: 100%; margin-bottom: 10px;" apple-inline="yes" id="ADC45541-04E9-4DFA-9DAB-3FB9948100CF" apple-width="yes" apple-height="yes" src="cid:C878FFDA-19C8-4C36-8BD4-3AD651EB2472" class=""></font></a></div><div class="dnd-legend-wrapper" style="box-sizing: border-box;"><div class="link" style="box-sizing: border-box; background-image: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-size: inherit; padding: 0px;"></div></div></div><p style="box-sizing: border-box; margin: 0px 0px 15px; -webkit-font-smoothing: inherit; line-height: 1.4em;" class=""><font size="4" class="">The nebula's hot gas glows in radiation across the electromagnetic spectrum, from radio to X-rays. The Hubble exposures were taken in visible light as black-and-white exposures. The Advanced Camera for Surveys made the observations between January and September 2012. The green hue that gives the nebula a Halloween theme, represents the color range of filter used in the observation..</font></p><p style="box-sizing: border-box; margin: 0px 0px 15px; -webkit-font-smoothing: inherit; line-height: 1.4em;" class=""><font size="4" class="">The Crab Nebula is one of the most historic and intensively studied supernova remnants. Observations of the nebula date back to 1054 A.D., when Chinese astronomers first recorded seeing a "guest star" during the daytime for 23 days. The star appeared six times brighter than Venus. Japanese, Arabic, and Native American stargazers also recorded seeing the mystery star. In 1758, while searching for a comet, French astronomer Charles Messier discovered a hazy nebula near the location of the long-vanished supernova. He later added the nebula to his celestial catalog as "Messier 1," marking it as a "fake comet." Nearly a century later British astronomer William Parsons sketched the nebula. Its resemblance to a crustacean led to M1's other name, the Crab Nebula. In 1928 astronomer Edwin Hubble first proposed associating the Crab Nebula to the Chinese "guest star" of 1054.</font></p><p style="box-sizing: border-box; margin: 0px 0px 15px; -webkit-font-smoothing: inherit; line-height: 1.4em;" class=""><font size="4" class="">The nebula, bright enough to be visible in amateur telescopes, is located 6,500 light-years away in the constellation Taurus.</font></p><div style="font-size: 14px;" class=""><br class=""></div><div style="font-size: 14px;" class=""><br class=""></div><div style="font-size: 14px;" class=""><br class=""></div><div style="font-size: 14px;" class=""><br class=""></div><div style="font-size: 14px;" class=""><br class=""></div><div style="font-size: 14px;" class=""><br class=""></div><div style="font-size: 14px;" class=""><br class=""></div><div style="font-size: 14px;" class=""><br class=""></div><div style="font-size: 14px;" class=""><br class=""></div><div class=""><div class="title-bar" style="font-size: 14px; box-sizing: border-box; margin: 2em 0px;"><div class="title-wrap" style="box-sizing: border-box; width: 738.75px; padding: 0px;"><h1 class="title" style="box-sizing: border-box; margin: 0px; font-family: inherit; line-height: 1.1; color: inherit; font-size: 2.2em;">Study: Planet Orbiting Nearest Star Could be Habitable </h1></div></div><section id="ember911" class="opened collapsible ember-view" style="box-sizing: border-box; max-height: none; overflow-y: hidden;"><div class="text" style="box-sizing: border-box;"><div class="type-image dnd-atom-wrapper context-full_width" style="box-sizing: border-box; clear: both; display: table; margin: 0px auto 2em;"><div class="dnd-drop-wrapper" style="box-sizing: border-box;"><a href="https://www.nasa.gov/sites/default/files/thumbnails/image/proximasurfacelarge900h_0.jpg" style="box-sizing: border-box; color: rgb(66, 139, 202); text-decoration: none; background-position: 0px 0px; background-repeat: initial initial;" class=""><img typeof="foaf:Image" width="985" height="554" alt="Artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri" title="" style="box-sizing: border-box; border: 0px; vertical-align: middle; max-width: 100%; margin-bottom: 10px;" apple-inline="yes" id="67BC0D26-8334-489D-A6C7-4BC105E093FC" apple-width="yes" apple-height="yes" src="cid:D28BE7ED-29E3-4787-8F70-6AF5DAB8C861" class=""></a></div><div class="dnd-legend-wrapper" style="box-sizing: border-box;"><div class="caption" style="box-sizing: border-box;">This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the solar system. The double star Alpha Centauri AB also appears in the image. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface.</div><div class="credits" style="box-sizing: border-box; font-style: italic; font-weight: 700;">Credits: ESO/M. Kornmesser</div><div class="link" style="font-size: 11px; box-sizing: border-box; background-image: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-size: inherit; padding: 0px;"></div></div></div><p style="box-sizing: border-box; margin: 0px 0px 15px; -webkit-font-smoothing: inherit; line-height: 1.4em;" class=""><font size="4" class="">A rocky extrasolar planet with a mass similar to Earth’s was recently detected around Proxima Centauri, the nearest star to our sun. This planet, called Proxima b, is in an orbit that would allow it to have liquid water on its surface, thus raising the question of its habitability. In a study to be published in The Astrophysical Journal Letters, an international team led by researchers at the Marseille Astrophysics Laboratory (CNRS/Aix-Marseille Université) has determined the planet’s dimensions and properties of its surface, which actually favor its habitability.The team says Proxima b could be an "ocean planet," with an ocean covering its entire surface, the water perhaps similar to that of subsurface oceans detected inside icy moons around Jupiter and Saturn. The researchers also show that Proxima b’s composition might resemble Mercury’s, with a metal core making up two-thirds of the mass of the planet. These results provide the basis for future studies to determine the habitability of Proxima b.Proxima Centauri, the star nearest the sun, has a planetary system consisting of at least one planet. The new study analyzes and supplements earlier observations. These new measurements show that this planet, named Proxima Centauri b or simply Proxima b, has a mass close to that of Earth (1.3 times Earth’s mass) and orbits its star at a distance of 0.05 astronomical units (one tenth of the sun-Mercury distance). Contrary to what one might think, such a small distance does not imply a high temperature on the surface of Proxima b because the host star, Proxima Centauri, is a red dwarf with a mass and radius that are only one-tenth that of the Sun, and a brightness a thousand times smaller than the sun’s. Hence Proxima b is in the habitable zone of its star and may harbor liquid water at its surface. However, very little is known about Proxima b, particularly its radius. It is therefore impossible to know what the planet looks like, or what it is made of. The radius measurement of an exoplanet is normally done during transit, when it eclipses its star. But Proxima b is not known to transit. There is another way to estimate the radius of a planet. If we know its mass, we can simulate the behavior of the constituent materials. This is the method used by a French-American team of researchers from the Marseille Astrophysics Laboratory (CNRS/Aix-Marseille University) and the Department of Astronomy at Cornell University. With the help of a model of internal structure, they explored the different compositions that could be associated with Proxima b and deduced the corresponding values for the radius of the planet. They restricted their study to the case of potentially habitable planets, simulating dense and solid planets, formed with the metallic core and rocky mantle found in terrestrial planets in our solar system. They also allowed the incorporation of a large mass of water in their composition. These assumptions allow a wide variety of compositions for Proxima b. The radius of the planet may vary between 0.94 and 1.40 times the radius of the Earth (3,959 miles, or 6,371 kilometers). The study shows that Proxima b has a minimum radius of 3,722 miles (5,990 kilometers), and the only way to get this value is to have a very dense planet, consisting of a metal core with a mass equal to 65 percent of the planet, the rest being rocky mantle (formed of silicate). The boundary between these two materials is then located about 932 miles (1,500 kilometers) depth. With such a composition, Proxima b is very close to the planet Mercury, which also has a very solid metal core. This first case does not exclude the presence of water on the surface of the planet, as on Earth where the water body does not exceed 0.05 percent of the mass of the planet. In contrast, Proxima b can also have a radius of 5,543 miles (8,920 kilometers), provided that it is composed of 50 percent rock surrounded by 50 percent water. In this case, Proxima b would be covered by a single liquid ocean 124 miles (200 kilometers) deep. Below, the pressure would be so strong that liquid water would turn to high-pressure ice before reaching the boundary with the mantle to 1,926 miles (3,100 kilometers) depth. In these extreme cases, a thin gas atmosphere could cover the planet, as on Earth, making Proxima b potentially habitable. Such findings provide important additional information to different composition scenarios that have been proposed for Proxima b. Some involve a completely dry planet, while others permit the presence of a significant amount of water in its composition. The work of the research team included providing an estimate of the radius of the planet for each of these scenarios. Similarly, this would restrict the amount of water available on Proxima b, where water is prone to evaporation by ultraviolet and X-rays from the host star, which are much more violent than those from the sun. Future observations of Proxima Centauri will refine this study. In particular, the measurement of stellar abundances of heavy elements (magnesium, iron, silicon) will decrease the number of possible compositions for Proxima b, allowing determination more accurate radius Proxima b. 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