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Seven Planets, Including Three Habitable Ones, Found Around Ultra-Cool Dwarf Star
Forty light-years away, a faint, dim, tiny star known as TRAPPIST-1 caught the fancy of a team of exoplanet hunters led by Michaël Gillon. By observing the starlight over long periods of time, they could tell when an orbiting planet passed in front of it, blocking a small fraction of its light in a periodic fashion. Only a small fraction of stars have their planets aligned in such a way that we can see them, and even fewer have rocky, Earth-like worlds at the right distance to potentially have liquid water — and life as we know it — on them. But this particular star, as scientist Brian Koberlein reports, was discovered to have seven planets orbiting it. Not only that, but three of them might be perfect for life.
The relative orbital sizes of the seven discovered planets. The two innermost ones are likely roasted, and the third is probably too hot for liquid water on its surface as well. But the next three, in the right spot in the habitable zone, might be more Earth-like than any worlds we’ve discovered before. Image credit: ESO/M. Gillon et al.In order to be habitable, at least habitable like Earth is, a world needs to be:
at the right distance from its star,
of the right mass,
with the right atmosphere,
and with the right amount of liquid water on its surface.While Earth is 150 million kilometers (93 million miles) away from the Sun, TRAPPIST-1 is only 8% the mass of the Sun, and gives off only 0.05% of the Sun’s energy. It would take more than 1900 stars like TRAPPIST-1 to equal the Sun.
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. Image credit: ESO/O. Furtak.
Yet at the same time, the seven worlds discovered to orbit TRAPPIST-1 are incredibly close in. They’re more comparable to the moons of Jupiter than they are to the planets in our Solar System as far as distances go. Yet that’s exactly what this system would need if it were to have any hope of liquid water on one of its worlds. As coauthor Amaury Triaud explains:
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 orbits of the Galilean moons around Jupiter, the seven planets discovered around TRAPPIST-1, and the inner Solar System worlds, shown together for comparison of scale. Image credit: ESO/O. Furtak.
The way we reconstruct how large each planet is comes from noticing how much light is blocked when it transits in front of the star. Seven unique, periodic signals were identified, with each one corresponding to a bona fide planet.
The data obtained for the transit depths of each of the seven planets around TRAPPIST-1. Data taken with the Spitzer Space Telescope. Image credit: ESO/M. Gillon et al.
Remarkably, each one of them is approximately the size of a world like ours, with many of them right around the size of Earth or Venus. They’re almost perfect: massive enough to hold onto a reasonably thick atmosphere, yet small enough to still be rocky, without a gaseous envelope.
Unlike the worlds in our Solar System, each one should be tidally locked to the parent star, meaning that the same side always sees “day” while the opposite side resides in eternal night. Yet life on Earth began in the oceans, and of these seven worlds, the fourth, fifth and sixth might all have conditions to support liquid oceans or lakes — if the atmosphere is favorable — bathed in eternal sunlight.
These worlds are also interesting because they’re substantially different from the worlds in our Solar System in some ways: they’re only about two-thirds as dense. While other solar systems we’ve found, mostly around more massive stars than TRAPPIST-1, have most of their worlds substantially smaller or larger than Earth, this system has seven worlds that are all approximately our size. As Michaël Gillon notes:
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!
These worlds are also interesting because they’re substantially different from the worlds in our Solar System in some ways: they’re only about two-thirds as dense. While other solar systems we’ve found, mostly around more massive stars than TRAPPIST-1, have most of their worlds substantially smaller or larger than Earth, this system has seven worlds that are all approximately our size. As Michaël Gillon notes:
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!
While the discovery of these seven planets is remarkable, the most interesting part of this story is yet to be written. As our telescopes become larger and more sophisticated, we’ll finally gain the ability to measure the spectra of these worlds’ atmospheres, search for signs of water and life, and perhaps even discover an answer to whether we’re not alone in the Universe as far as life goes. With three strong candidates, we might finally need to face the possibility that most of the life that arises in the Universe might occur around stars that aren’t like the Sun!
WHY RAMS’ SCHEME CHANGE WON’T AFFECT AARON DONALD
With Wade Phillips in as the Rams’ new defensive coordinator, Sam Monson explores the impact of a defensive scheme change.https://www.profootballfocus.com/pro-why-rams-scheme-change-wont-affect-aaron-donald/
Nothing causes hysteria and concern among a fanbase like a new coaching hire that brings with it the prospect of a change in defensive scheme up front.
This offseason, Wade Phillips was let go as defensive coordinator in Denver following the head-coaching change there, and was quickly snatched up by the Los Angeles Rams, replacing the departing Greg Williams in the same role. That means a switch in scheme for Los Angeles between 4-3 and 3-4 defensive fronts, which immediately raises questions about whether the Rams have the personnel for that change, and what it means for star defensive tackle, Aaron Donald, a player that has ranked first and second in PFF’s Top 101 player list over the past two years, respectively.
The answer to that last question: almost nothing.
In reality, there isn’t much distinction between 3-4 and 4-3 schemes today the way there once was.
When the 3-4 was first in vogue back in the 1990s, it was a two-gap system, where giant behemoths on the D-line played head-up over their blockers, defending the gap to either side of them and occupying space for the linebackers behind them to make plays uncontested. 4-3 defenses were typically one-gap schemes with smaller bodies up front that attacked gaps and won with penetration, while the 3-4 was a system where the linebackers, not the defensive linemen, were the stars, and the big bodies up front controlled multiple gaps without overcommitting to either one.
Today’s 3-4 defenses are very different animals, and predominantly one-gap systems, just like the 4-3. The NFL is generally a one-gap league these days, and there is very little two-gapping deployed as the league has trended towards smaller, quicker players across the board. Gargantuan nose tackles of the past like Ted Washington, Gilbert Brown and Grady Jackson have been eased out in favor of more athletic players that can move down the line, rush the passer, and not just occupy space. Sub 300-pound defensive tackles are not uncommon, and you will even find 3-4 nose tackles that barely tip the scales at over 300 pounds.
The real driving force behind the adjustments in scheme is the passing game. The NFL is a passing league and now lives in nickel defense, not base. Most teams run with three wide receivers on offense instead of a fullback or second tight end, so defenses have countered with an extra defensive back. Last season, base 4-3 and 3-4 defenses combined (with just four defensive backs on the field) accounted for only 27 percent of defensive snaps, while nickel defense (five defensive backs) was at 55 percent, and dime (six defensive backs) another 10.
What used to be your every-down defense is now being used on average only a quarter of the time. Even if two teams have dramatically different base defensive alignments, they are in sub packages far more often, and those sub packages are much more uniform in structure. Base defenses can see significant differences in alignment, but while the 55 percent of snaps the league spends in nickel defense breaks down into a few different personnel groupings, most of them are essentially different ways of achieving the same alignment.
Whether you are a 3-4 or 4-3 base defense, moving to a nickel personnel grouping takes somebody out of the front-seven and adds a player to the secondary. When that happens, most teams deploy the remaining six players up front in more or less the same way because it is the most efficient way of accounting for every gap along the line.
The first guy to get sacrificed is the big nose tackle for 3-4 teams. Linemen that weigh 320-plus pounds may still be great run defenders, but they tend to offer little as pass-rushing threats. 4-3 teams typically lose one of their three linebackers, leaving both schemes with two edge defenders, two interior defenders and two off-the-ball linebackers to go along with their five defensive backs. The only difference is exactly how those edge defenders stand when they line up. Whether you’re a 3-4 or 4-3 base team, the alignment of the front four in nickel and dime defense tends to wind up the same, but is still differentiated by anachronistic position designations that no longer make sense as descriptive tools.
This image shows Denver’s defense under Wade Phillips and the Rams’ defense under Greg Williams from last year, superimposed into one image.
The teams were both facing near enough the same offensive formation, and they deployed their front four in identical gap alignments. The only difference between the two was that the player furthest to the right side playing on the edge was an outside linebacker for the Broncos (DeMarcus Ware) who rushed from a two-point stance, but for the Rams, that player was a defensive end that had his hand in the dirt (Eugene Sims).
Those players are listed at different positions on the roster, but have identical roles from the exact same alignment on the play in this situation. The distinction between linebacker and defensive end is far less meaningful in the world of nickel defense than that between edge defender, interior defender and off-the-ball linebacker, which is why the Pro-Bowl ballot will remain broken until it adopts that shift in player designation.
The difference in the stance of the edge defender between two-point and hand in the dirt may not even be a team-prescribed technique. There are teams in the league (the Patriots, being one) that allow their edge defenders to choose which they feel more comfortable with on any given play, effectively leaving the designation of that defensive front to one player’s whim each snap (if all you care about is how many players have their hand in the ground). As long as he is lined up in the right spot, those teams don’t care if he is in a two- or three-point stance, so the label of linebacker or defensive end is entirely meaningless and arbitrary for that player on that play.
The same thing is true for interior defenders, too. Aaron Donald is known as a 3-technique defensive tackle, or “under-tackle” in a 4-man defensive-line scheme. 3-technique is simply the name of the defensive-line technique that sees a player lined up over the outside shoulder of the guard, ready to attack the gap to his outside. Most pass-rushing defensive tackles primarily play in that specific technique, but so do most pass-rushing 3-4 defensive ends. Calais Campbell, in Arizona’s 3-4 scheme, plays more 3-technique than any other technique—and more than many defensive tackles—but is listed as a defensive end on the roster. Donald’s alignment distribution in 2016 almost exactly matches that of Denver’s defensive ends, Derek Wolfe and Jared Crick.
The defense that Wade Phillips runs does have some eccentricities compared to other systems in the league—they tend to stay in base defense longer than most teams and then leap straight to six defensive backs, bypassing the nickel packages of five DBs altogether. Even in base defense, though, it is very much like a 4-3 scheme from an alignment standpoint.
When looking at the alignment distribution of Wolfe against Donald last year, the only difference between the two is a small spike for Wolfe in the 4-technique spot, the technique that plays head up over the tackle (the original 3-4 two-gap style alignment we mentioned earlier). There will be plays where we see Donald lined up in this spot, but Wolfe played there less than half as often as he played in the 3-technique spot that Donald usually occupied, and even in that alignment, he is going to be tasked with shooting a gap and defeating that tackle with quickness and hand speed rather than trying to eat up space and two-gap either side of him. In Phillips’ scheme, it is more of a disguise measure than it is a statement of two-gapping intent.
We are going to see Aaron Donald and the rest of the Rams’ defense lining up in a new defensive front under Wade Phillips in 2017, but if you can look beyond how many players have their hand in the ground, operating from a three-point stance, you’ll see that the alignment of those players has changed little despite the shift from 4-3 to 3-4. That once was a seismic shift that required a complete retooling of your defensive personnel to make it work, but in today’s NFL, it’s just a different way to shuffle the same cards. Aaron Donald may now be labelled as a 3-4 defensive end, but he will be the same destructive force as an interior defender as he has been over the past couple of seasons.
For me cause of format this one was just easier to read here. Though I was wondering, is that Ceti Alpha 5 and 6 there?
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At about 40 light-years (235 trillion miles) from Earth, the system of planets is relatively close to us, in the constellation Aquarius. Because they are located outside of our solar system, these planets are scientifically known as exoplanets.
This exoplanet system is called TRAPPIST-1, named for The Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile. In May 2016, researchers using TRAPPIST announced they had discovered three planets in the system. Assisted by several ground-based telescopes, including the European Southern Observatory’s Very Large Telescope, Spitzer confirmed the existence of two of these planets and discovered five additional ones, increasing the number of known planets in the system to seven.
The new results were published Wednesday in the journal Nature, and announced at a news briefing at NASA Headquarters in Washington.
Using Spitzer data, the team precisely measured the sizes of the seven planets and developed first estimates of the masses of six of them, allowing their density to be estimated.
Based on their densities, all of the TRAPPIST-1 planets are likely to be rocky. Further observations will not only help determine whether they are rich in water, but also possibly reveal whether any could have liquid water on their surfaces. The mass of the seventh and farthest exoplanet has not yet been estimated – scientists believe it could be an icy, “snowball-like” world, but further observations are needed.
“The seven wonders of TRAPPIST-1 are the first Earth-size planets that have been found orbiting this kind of star,” said Michael Gillon, lead author of the paper and the principal investigator of the TRAPPIST exoplanet survey at the University of Liege, Belgium. “It is also the best target yet for studying the atmospheres of potentially habitable, Earth-size worlds.”
In contrast to our sun, the TRAPPIST-1 star – classified as an ultra-cool dwarf – is so cool that liquid water could survive on planets orbiting very close to it, closer than is possible on planets in our solar system. All seven of the TRAPPIST-1 planetary orbits are closer to their host star than Mercury is to our sun. The planets also are very close to each other. If a person was standing on one of the planet’s surface, they could gaze up and potentially see geological features or clouds of neighboring worlds, which would sometimes appear larger than the moon in Earth’s sky.
The planets may also be tidally locked to their star, which means the same side of the planet is always facing the star, therefore each side is either perpetual day or night. This could mean they have weather patterns totally unlike those on Earth, such as strong winds blowing from the day side to the night side, and extreme temperature changes.
Spitzer, an infrared telescope that trails Earth as it orbits the sun, was well-suited for studying TRAPPIST-1 because the star glows brightest in infrared light, whose wavelengths are longer than the eye can see. In the fall of 2016, Spitzer observed TRAPPIST-1 nearly continuously for 500 hours. Spitzer is uniquely positioned in its orbit to observe enough crossing – transits – of the planets in front of the host star to reveal the complex architecture of the system. Engineers optimized Spitzer’s ability to observe transiting planets during Spitzer’s “warm mission,” which began after the spacecraft’s coolant ran out as planned after the first five years of operations.
“This is the most exciting result I have seen in the 14 years of Spitzer operations,” said Sean Carey, manager of NASA’s Spitzer Science Center at Caltech/IPAC in Pasadena, California. “Spitzer will follow up in the fall to further refine our understanding of these planets so that the James Webb Space Telescope can follow up. More observations of the system are sure to reveal more secrets.”
Following up on the Spitzer discovery, NASA’s Hubble Space Telescope has initiated the screening of four of the planets, including the three inside the habitable zone. These observations aim at assessing the presence of puffy, hydrogen-dominated atmospheres, typical for gaseous worlds like Neptune, around these planets.
This 360-degree panorama depicts the surface of a newly detected planet, TRAPPIST 1-d, part of a seven planet system some 40 light years away. Explore this artist’s rendering of an alien world by moving the view using your mouse or your mobile device.
In May 2016, the Hubble team observed the two innermost planets, and found no evidence for such puffy atmospheres. This strengthened the case that the planets closest to the star are rocky in nature.
“The TRAPPIST-1 system provides one of the best opportunities in the next decade to study the atmospheres around Earth-size planets,” said Nikole Lewis, co-leader of the Hubble study and astronomer at the Space Telescope Science Institute in Baltimore, Maryland. NASA’s planet-hunting Kepler space telescope also is studying the TRAPPIST-1 system, making measurements of the star’s minuscule changes in brightness due to transiting planets. Operating as the K2 mission, the spacecraft’s observations will allow astronomers to refine the properties of the known planets, as well as search for additional planets in the system. The K2 observations conclude in early March and will be made available on the public archive.
Spitzer, Hubble, and Kepler will help astronomers plan for follow-up studies using NASA’s upcoming James Webb Space Telescope, launching in 2018. With much greater sensitivity, Webb will be able to detect the chemical fingerprints of water, methane, oxygen, ozone, and other components of a planet’s atmosphere. Webb also will analyze planets’ temperatures and surface pressures – key factors in assessing their habitability.
NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate. Science operations are conducted at the Spitzer Science Center, at Caltech, in Pasadena, California. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at Caltech/IPAC. Caltech manages JPL for NASA.
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