Here is a video of the NASA panel discussion of the findings by an international team of the TRAPPIST-1 star system with 7 earth sized exoplanets (see earlier posting here).
The briefing participants included:
Thomas Zurbuchen, associate administrator of the Science Mission Directorate at NASA Headquarters in Washington
Michael Gillon, astronomer at the University of Liege in Belgium
Sean Carey, manager of NASA’s Spitzer Science Center at Caltech/IPAC, Pasadena, California
Nikole Lewis, astronomer at the Space Telescope Science Institute in Baltimore
Sara Seager, professor of planetary science and physics at Massachusetts Institute of Technology, Cambridge
This artist’s impression shows the view from the surface of one of the planets in the TRAPPIST-1 system. At least seven planets orbit this ultra cool dwarf star 40 light-years from Earth and they are all roughly the same size as the Earth. They are at the right distances from their star for liquid water to exist on the surfaces of several of them. This artist’s impression is based on the known physical parameters for the planets and stars seen, and uses a vast database of objects in the Universe. [Full size image]Astronomers have found a system of seven Earth-sized planets just 40 light-years away. Using ground and space telescopes, including ESO’s Very Large Telescope, the planets were all detected as they passed in front of their parent star, the ultracool dwarf star known as TRAPPIST-1. According to the paper appearing today in the journal Nature, three of the planets lie in the habitable zone and could harbour oceans of water on their surfaces, increasing the possibility that the star system could play host to life. This system has both the largest number of Earth-sized planets yet found and the largest number of worlds that could support liquid water on their surfaces.
Astronomers using the TRAPPIST–South telescope at ESO’s La Silla Observatory, the Very Large Telescope (VLT) at Paranal and the NASA Spitzer Space Telescope, as well as other telescopes around the world [1], have now confirmed the existence of at least seven small planets orbiting the cool red dwarf star TRAPPIST-1[2]. All the planets, labelled TRAPPIST-1b, c, d, e, f, g and h in order of increasing distance from their parent star, have sizes similar to Earth [3].
This diagram compares the sizes of the newly-discovered planets around the faint red star TRAPPIST-1 with the Galilean moons of Jupiter and the inner Solar System. All the planets found around TRAPPIST-1 are of similar size to the Earth. [Full size image.]Dips in the star’s light output caused by each of the seven planets passing in front of it — events known as transits — allowed the astronomers to infer information about their sizes, compositions and orbits [4]. They found that at least the inner six planets are comparable in both size and temperature to the Earth.
This diagram shows the changing brightness of the ultra cool dwarf star TRAPPIST-1 over a period of 20 days in September and October 2016 as measured by NASA’s Spitzer Space Telescope and many other telescopes on the ground. On many occasions the brightness of the star drops for a short period and then returns to normal. These events, called transits, are due to one or more of the star’s seven planets passing in front of the star and blocking some of its light. The lower part of the diagram shows which of the system’s planets are responsible for the transits. [Full size image]
Lead author Michaël Gillon of the STAR Institute at the University of Liège in Belgium is delighted by the findings:
“This is an amazing planetary system — not only because we have found so many planets, but because they are all surprisingly similar in size to the Earth!”
With just 8% the mass of the Sun, TRAPPIST-1 is very small in stellar terms — only marginally bigger than the planet Jupiter — and though nearby in the constellation Aquarius (The Water Carrier), it appears very dim. Astronomers expected that such dwarf stars might host many Earth-sized planets in tight orbits, making them promising targets in the hunt for extraterrestrial life, but TRAPPIST-1 is the first such system to be found.
Co-author Amaury Triaud expands:
“The energy output from dwarf stars like TRAPPIST-1 is much weaker than that of our Sun. Planets would need to be in far closer orbits than we see in the Solar System if there is to be surface water. Fortunately, it seems that this kind of compact configuration is just what we see around TRAPPIST-1!”
The team determined that all the planets in the system are similar in size to Earth and Venus in the Solar System, or slightly smaller. The density measurements suggest that at least the innermost six are probably rocky in composition.
This infographic displays some artist’s illustrations of how the seven planets orbiting TRAPPIST-1 might appear — including the possible presence of water oceans — alongside some images of the rocky planets in our Solar System. Information about the size and orbital periods of all the planets is also provided for comparison; the TRAPPIST-1 planets are all approximately Earth-sized. [Full sized image]The planetary orbits are not much larger than that of Jupiter’s Galilean moon system, and much smaller than the orbit of Mercury in the Solar System. However, TRAPPIST-1’s small size and low temperature mean that the energy input to its planets is similar to that received by the inner planets in our Solar System; TRAPPIST-1c, d and f receive similar amounts of energy to Venus, Earth and Mars, respectively.
This diagram compares the orbits of the newly-discovered planets around the faint red star TRAPPIST-1 with the Galilean moons of Jupiter and the inner Solar System. All the planets found around TRAPPIST-1 orbit much closer to their star than Mercury is to the Sun, but as their star is far fainter, they are exposed to similar levels of irradiation as Venus, Earth and Mars in the Solar System. [Full size image ]All seven planets discovered in the system could potentially have liquid water on their surfaces, though their orbital distances make some of them more likely candidates than others. Climate models suggest the innermost planets, TRAPPIST-1b, c and d, are probably too hot to support liquid water, except maybe on a small fraction of their surfaces. The orbital distance of the system’s outermost planet, TRAPPIST-1h, is unconfirmed, though it is likely to be too distant and cold to harbour liquid water — assuming no alternative heating processes are occurring [5]. TRAPPIST-1e, f, and g, however, represent the holy grail for planet-hunting astronomers, as they orbit in the star’s habitable zone and could host oceans of surface water [6].
This diagram compares the orbits of the newly-discovered planets around the faint red star TRAPPIST-1 with the Galilean moons of Jupiter and the inner Solar System. All the planets found around TRAPPIST-1 orbit much closer to their star than Mercury is to the Sun, but as their star is far fainter, they are exposed to similar levels of irradiation as Venus, Earth and Mars in the Solar System. [Full size image]These new discoveries make the TRAPPIST-1 system a very important target for future study. The NASA/ESA Hubble Space Telescope is already being used to search for atmospheres around the planets and team member Emmanuël Jehin is excited about the future possibilities:
This video takes the viewer on a quick trip from Earth, past the Moon and far beyond. We finally arrive at the faint red ultracool dwarf star TRAPPIST-1, which has a remarkable seven planets orbiting it, all having sizes similar to the Earth.
The stars in the animation are accurately positioned as in reality. The tiny ultracool dwarf TRAPPIST-1 is so dim that it would remain invisible to the naked eye until the imaginary traveller gets very close, when its seven orbiting planets can also be seen.
The artist’s impression in this video is based on the known physical parameters for the planets and stars seen, and uses a vast database of objects in the Universe. Credit: ESO/L. Calçada/spaceengine.org
[2] TRAPPIST–South (the TRAnsiting Planets and PlanetesImals Small Telescope–South) is a Belgian 0.6-metre robotic telescope operated from the University of Liège and based at ESO’s La Silla Observatory in Chile. It spends much of its time monitoring the light from around 60 of the nearest ultracool dwarf stars and brown dwarfs (“stars” which are not quite massive enough to initiate sustained nuclear fusion in their cores), looking for evidence of planetary transits. TRAPPIST–South, along with its twin TRAPPIST–North, are the forerunners to the SPECULOOS system, which is currently being installed at ESO’s Paranal Observatory.
[3] In early 2016, a team of astronomers, also led by Michaël Gillon announced the discovery of three planets orbiting TRAPPIST-1. They intensified their follow-up observations of the system mainly because of a remarkable triple transit that they observed with the HAWK-I instrument on the VLT. This transit showed clearly that at least one other unknown planet was orbiting the star. And that historic light curve shows for the first time three temperate Earth-sized planets, two of them in the habitable zone, passing in front of their star at the same time!
[4] This is one of the main methods that astronomers use to identify the presence of a planet around a star. They look at the light coming from the star to see if some of the light is blocked as the planet passes in front of its host star on the line of sight to Earth — it transits the star, as astronomers say. As the planet orbits around its star, we expect to see regular small dips in the light coming from the star as the planet moves in front of it.
[5] Such processes could include tidal heating, whereby the gravitational pull of TRAPPIST-1 causes the planet to repeatedly deform, leading to inner frictional forces and the generation of heat. This process drives the active volcanism on Jupiter’s moon Io. If TRAPPIST-1h has also retained a primordial hydrogen-rich atmosphere, the rate of heat loss could be very low.
[6] This discovery also represents the largest known chain of exoplanets orbiting in near-resonance with each other. The astronomers carefully measured how long it takes for each planet in the system to complete one orbit around TRAPPIST-1 — known as the revolution period — and then calculated the ratio of each planet’s period and that of its next more distant neighbour. The innermost six TRAPPIST-1 planets have period ratios with their neighbours that are very close to simple ratios, such as 5:3 or 3:2. This means that the planets most likely formed together further from their star, and have since moved inwards into their current configuration. If so, they could be low-density and volatile-rich worlds, suggesting an icy surface and/or an atmosphere.
This artist’s concept illustrates a close-up view of a cool brown dwarf. Objects like this, drifting just beyond our solar system, have been imaged by NASA’s Wide-field Infrared Survey Explorer and could be discovered by Backyard Worlds: Planet 9. Credit: NASA/JPL-Caltech › Full image and caption
NASA is inviting the public to help search for possible undiscovered worlds in the outer reaches of our solar system and in neighboring interstellar space. A new website, called Backyard Worlds: Planet 9, lets everyone participate in the search by viewing brief movies made from images captured by NASA’s Wide-field Infrared Survey Explorer (WISE) mission. The movies highlight objects that have gradually moved across the sky.
“There are just over four light-years between Neptune and Proxima Centauri, the nearest star, and much of this vast territory is unexplored,” said lead researcher Marc Kuchner, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Because there’s so little sunlight, even large objects in that region barely shine in visible light. But by looking in the infrared, WISE may have imaged objects we otherwise would have missed.”
WISE scanned the entire sky between 2010 and 2011, producing the most comprehensive survey at mid-infrared wavelengths currently available. With the completion of its primary mission, WISE was shut down in 2011. It was then reactivated in 2013 and given a new mission assisting NASA’s efforts to identify potentially hazardous near-Earth objects (NEOs), which are asteroids and comets on orbits that bring them into the vicinity of Earth’s orbit. The mission was renamed the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE).
The new website uses the data to search for unknown objects in and beyond our own solar system. In 2016, astronomers at Caltech, in Pasadena, California, showed that several distant solar system objects possessed orbital features indicating they were affected by the gravity of an as-yet-undetected planet, which the researchers nicknamed “Planet Nine.” If Planet Nine — also known as Planet X — exists and is as bright as some predictions, it could show up in WISE data.
The search also may discover more-distant objects like brown dwarfs, sometimes called failed stars, in nearby interstellar space.
“Brown dwarfs form like stars but evolve like planets, and the coldest ones are much like Jupiter,” said team member Jackie Faherty, an astronomer at the American Museum of Natural History in New York. “By using Backyard Worlds: Planet 9, the public can help us discover more of these strange rogue worlds.”
Unlike more distant objects, those in or closer to the solar system appear to move across the sky at different rates. The best way to discover them is through a systematic search of moving objects in WISE images. While parts of this search can be done by computers, machines are often overwhelmed by image artifacts, especially in crowded parts of the sky. These include brightness spikes associated with star images and blurry blobs caused by light scattered inside WISE’s instruments.
Backyard Worlds: Planet 9 relies on human eyes because we easily recognize the important moving objects while ignoring the artifacts. It’s a 21st-century version of the technique astronomer Clyde Tombaugh used to find Pluto in 1930, a discovery made 87 years ago this week.
On the website, people around the world can work their way through millions of “flipbooks,” which are brief animations showing how small patches of the sky changed over several years. Moving objects flagged by participants will be prioritized by the science team for follow-up observations by professional astronomers. Participants will share credit for their discoveries in any scientific publications that result from the project.
“Backyard Worlds: Planet 9 has the potential to unlock once-in-a-century discoveries, and it’s exciting to think they could be spotted first by a citizen scientist,” said team member Aaron Meisner, a postdoctoral researcher at the University of California, Berkeley, who specializes in analyzing WISE images.
Backyard Worlds: Planet 9 is a collaboration among NASA, UC Berkeley, the American Museum of Natural History in New York, Arizona State University in Tempe, the Space Telescope Science Institute in Baltimore, and Zooniverse, a collaboration of scientists, software developers and educators who collectively develop and manage citizen science projects on the internet.
A previously cataloged brown dwarf named WISE 0855?0714 shows up as a moving orange dot in this loop of WISE images spanning five years. By viewing movies like this, anyone can help discover more of these objects. Credits: NASA/WISE › Larger view
NASA’s Jet Propulsion Laboratory in Pasadena manages and operates WISE for NASA’s Science Mission Directorate. The WISE mission was selected competitively under NASA’s Explorers Program managed by the agency’s Goddard Space Flight Center. The science instrument was built by the Space Dynamics Laboratory in Logan, Utah. The spacecraft was built by Ball Aerospace & Technologies Corp. in Boulder, Colorado. Science operations and data processing take place at IPAC at Caltech, which manages JPL for NASA.
Stars are the atoms of the universe. The process by which stars form is at the nexus of astrophysics since they are believed to be responsible for the re-ionization of the universe, they created the heavy elements, they play a central role in the formation and evolution of galaxies, and their formation naturally leads to the formation of planets. Whereas early work on star formation was based on the assumption that it is a quiescent process, it is now believed that turbulence plays a dominant role. In this overview, I shall discuss the evolution of our understanding of how stars form and current ideas about the stellar initial mass function, the rate of star formation, the formation of massive stars, the role of magnetic fields, and the formation of the first stars.
Here is a preview of night sky highlights for the coming month:
Use Venus and Mars to find the Zodiacal Light, plus two comets and the brightest asteroid. Find more astronomy information and events in your area by visiting https://nightsky.jpl.nasa.gov/ .
