The TRAPPIST-1 star system is home to the largest batch of roughly Earth-size planets ever found outside our solar system. some 40 light-years away, these seven rocky siblings offer a glimpse at the tremendous variety of planetary systems that likely fill the universe.

A accepted by the Planetary Science Journal shows that the planets share similar densities. That could mean they all contain roughly the same ratio of materials thought to be common to rocky planets, such as iron, oxygen, magnesium and silicon. If so, then while the might be similar to each other, they appear to differ notably from Earth: They鈥檙e about 8% less dense than they would be if they had the same chemical composition as our planet.

These findings give astronomers new data that they鈥檙e using to try to pin down the precise composition of these planets, and compare them not just to Earth, but to all the rocky planets in our solar system, according to lead author , a 天美影视传媒 professor of astronomy.

鈥淭his is one of the most precise characterizations of a set of rocky exoplanets, which gave us high-confidence measurements of their diameters, densities and masses,鈥� said Agol. 鈥淭his is the information we needed to make hypotheses about their composition and understand how these planets differ from the rocky planets in our solar system.鈥�

Since the initial detection in 2016 of the TRAPPIST-1 worlds, scientists have studied this planetary family with multiple space- and ground-based telescopes, including NASA’s now-retired and . Spitzer alone provided over 1,000 hours of targeted observations of the system before . Since they鈥檙e too small and faint to view directly, all seven exoplanets were found via the so-called transit method: looking for dips in the star’s brightness created when the planets cross in front of it.

had shown that the planets are roughly the size and mass of Earth and thus must also be 鈥� as opposed to gas-dominated worlds like Jupiter and Saturn. This new study offers the most precise density measurements to date for any group of exoplanets.

“The night sky is full of planets, and it’s only been within the last 30 years that we’ve been able to start unraveling their mysteries,” said co-author of the University of Zurich. “The TRAPPIST-1 system is fascinating because around this one star we can learn about the diversity of rocky planets within a single system. And we can actually learn more about a planet by studying its neighbors as well, so this system is perfect for that.”

The team 鈥� which includes scientists based in the United States, Switzerland, France, the United Kingdom and Morocco 鈥� used observations of the starlight dips and precise measurements of the timing of the planets’ orbits to make detailed measurements of each planet鈥檚 mass and diameter, and from there to determine its density. Agol and UW co-authors Zachary Langford and , a professor of astronomy, analyzed data and performed computer simulations that constrained the orbits of the TRAPPIST-1 planets and calculated their densities.

With more precise measurements of an object鈥檚 density, we can know more about its composition. A baseball and a paperweight may be the same size, but the baseball is much lighter. Width and weight together reveal each object’s density, and from there it is possible to infer that the baseball is made of lighter materials, like string and leather, while the paperweight has a heavier composition, like glass or metal.

In our own solar system, the densities of the eight planets vary widely. The gas giants 鈥� Jupiter, Saturn, Uranus and Neptune 鈥� are larger, but much less dense than the four rocky planets. Earth, Venus and Mars have similar densities, but Mercury contains a much higher percentage of iron, so although it is the solar system’s smallest planet in diameter, Mercury has the second highest density of all eight planets.

The seven TRAPPIST-1 planets, on the other hand, all share a similar density, which makes the system quite different from our own. The difference in density between the TRAPPIST-1 planets and Earth, Venus and Mars, may seem small 鈥� about 8% 鈥� but it is significant on a planetary scale. For example, one way to explain the lower density is that the TRAPPIST-1 planets have a similar composition to Earth, but with a lower percentage of iron 鈥� about 21% compared to Earth’s 32%, according to the study.

Alternatively, the iron in the TRAPPIST-1 planets might be infused with high levels of oxygen, forming iron oxide, or rust. The additional oxygen would decrease the planets’ densities. The surface of Mars gets its red tint from iron oxide, but like its three terrestrial siblings, it has a core composed of non-oxidized iron. By contrast, if the lower density of the TRAPPIST-1 planets were caused entirely by oxidized iron, then the planets would have to be rusty throughout and could not have iron cores.

Agol said the answer might be a combination of the two scenarios 鈥� less iron overall and some oxidized iron.

The team also looked into whether the surface of each planet could be covered with water, which is even lighter than rust and which would change the planet’s overall density. If that were the case, water would have to account for about 5% of the total mass of the outer four planets. By comparison, water makes up less than 0.1% of Earth’s total mass. The three inner TRAPPIST-1 planets, positioned too close to their star for water to remain a liquid under most circumstances, would require hot, dense atmospheres like on Venus, where water could remain bound to the planet as steam. But this explanation seems less likely because it would be a coincidence for all seven planets to have just enough water present to have such similar densities, according to Agol.

When it launches, NASA鈥檚 James Webb Space Telescope should have the capabilities to probe this system further, including gathering more detailed information about the atmospheres of the seven TRAPPIST-1 worlds.

鈥淭here are many more questions to answer about TRAPPIST-1 and its worlds,鈥� said Agol. 鈥淎nd in a way, answering them helps us understand our own solar system, too.鈥�

Agol and Meadows are members of the NASA NExSS Virtual Planetary Laboratory team and the UW Astrobiology Program. Agol鈥檚 involvement in the study was funded by the National Science Foundation, NASA, the Guggenheim Foundation and the Virtual Planetary Laboratory.

For more information, contact Agol at agol@uw.edu.

Adapted from a by NASA鈥檚 Jet Propulsion Laboratory.

A team of astronomers including of the 天美影视传媒 has found that the seven Earth-sized planets orbiting the star TRAPPIST-1 are all made mostly of rock, and some could even have more water 鈥� which can give life a chance 鈥� than Earth itself.

The research was led by Simon Grimm of the University of Bern in Switzerland, and Feb. 5 in the journal Astronomy and Astrophysics. Agol is among about two dozen co-authors. The scientists created computer models to simulate the planets based on available information.

TRAPPIST-1 is an ultra-cool dwarf star about 40 light-years 鈥� or about 235 trillion miles 鈥� from Earth in the Aquarius constellation. Astronomers its seven potentially habitable planets in early 2017 using the NASA Spitzer Space Telescope and the European Southern Observatory’s in Chile. It is the first known system with so many Earth-sized planets orbiting a single star.

TRAPPIST-1’s seven planets 鈥� labeled TRAPPIST-1b though h, moving outward from the star 鈥� orbit more closely to it than Mercury does the sun, which would be too close for potential habitability in our own system. But because the star is faint, its habitable zone 鈥� the swath of space around it just right to allow an orbiting rocky planet to sustain water on its surface 鈥� lies closer in, so orbiting planets could still, in theory, hold liquid water. Some may be tidally locked, with the same side forever facing the star.

In fact, the worlds orbit TRAPPIST-1 so closely, a person standing on the surface of one would have a spectacular view of the neighboring planets 鈥� some appearing in the sky larger than the moon looks from 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 鈥� about 250 times more than Earth’s oceans. The hotter, closer-in worlds likely have dense, steamy atmospheres, and the more distant ones icy surfaces.

In terms of size, density and the amount of radiation it receives from its star, the fourth planet out, TRAPPIST-1e, is the most similar to Earth, though slightly denser. It seems to be the rockiest planet of the seven, and has the potential to host liquid water. TRAPPIST-1f, g and h are far enough from the star, water could be frozen across their surfaces.

The researchers were able to calculate densities of the planets because they are aligned such that as they pass in front of their star, Earth- and space-based telescopes can detect a dimming of its light, called a transit. The amount by which the starlight dims is related to the radius of the planet.

The team used what are called “transit timing variations,” or TTV 鈥� a method Agol assisted in developing over recent years 鈥� to learn the density of the planets. Minus other gravitational forces, a transiting planet will always cross in front of its host star in the same amount of time 鈥� just as the Earth orbits the sun like clockwork every 365 days.

But because the TRAPPIST-1 planets are packed so close together, they affect one another gravitationally, slightly changing the timing of each other’s “years.” Those variations in orbital timing are used to estimate the planets’ masses.

Agol performed the TTV calculations in parallel with lead author Grimm. “We obtained the same masses for the planets,” he said, “which was great to have concordance, and increased our faith that neither was making any mistakes.”

Then mass and radius are in turn used to calculate density.

Agol, a UW professor of astronomy 鈥� supported in this work by a Guggenheim fellowship 鈥� is affiliated with the NASA Astrobiology Institute’s , based at the UW. Other co-authors are from Universit茅 de Li猫ge, Li猫ge, Belgium; Cambridge University; the University of Birmingham in the UK, the Massachusetts Institute of Technology, the University of Bordeaux; University of California, San Diego; the University of Chicago, the California Institute of Technology and several other institutions.

The next step, researchers say, in exploring the TRAPPIST-1 system, researchers say, will be to use NASA’s coming James Webb Telescope to study the atmospheres of these worlds.

“A goal of exoplanet studies for some time has been to probe the composition of planets that are Earth-like in size and temperature,” said Agol. “The discovery of TRAPPIST-1 and the capabilities of ESO鈥檚 facilities in Chile and the NASA Spitzer Space Telescope in orbit have made this possible 鈥� giving us our first glimpse of what Earth-sized exoplanets are made of.”

Sean Carey, manager of the Spitzer Science Center at Cal Tech, said, “We now know more about TRAPPIST-1 than any other planetary system apart from our own.”

Adapted in part from releases by the and .

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For more information, contact Agol at 206-543-7106 or agol@astro.washington.edu.

A 天美影视传媒-led international team of astronomers has used data gathered by the Kepler Space Telescope to observe and confirm details of the outermost of seven exoplanets orbiting the star .

They confirmed that the planet, TRAPPIST-1h, orbits its star every 18.77 days, is linked in its orbital path to its siblings and is frigidly cold. Far from its host star, the planet is likely uninhabitable 鈥� but it may not always have been so.

UW doctoral student is lead author on a published May 22 in the journal Nature Astronomy.

“TRAPPIST-1h was exactly where our team predicted it to be,” Luger said. The researchers discovered a mathematical pattern in the orbital periods of the inner six planets, which was strongly suggestive of an 18.77 day period for planet h.

“It had me worried for a while that we were seeing what we wanted to see. Things are almost never exactly as you expect in this field 鈥� there are usually surprises around every corner, but theory and observation matched perfectly in this case.”

TRAPPIST-1 is a middle-aged, ultra cool dwarf star, much less luminous than the sun and only a bit larger than the planet Jupiter. The star, which is nearly 40 light-years or about 235 trillion miles away in the constellation of Aquarius, is named after the ground-based Transiting Planets and Planetesimals Small Telescope (TRAPPIST), the facility that first found evidence of planets around it in 2015.

The TRAPPIST survey is led by of the University of Li猫ge, Belgium, who is also a coauthor on this research. In 2016, Gillon鈥檚 team announced the detection of three planets orbiting TRAPPIST-1 and this number was upped to seven in a subsequent 2017 paper. Three of
TRAPPIST-1’s planets appear to be within the star’s habitable zone, that swath of space around a star where a rocky planet could have liquid water on its surface, thus giving life a chance.

Such exoplanets are detected when they transit, or pass in front of, their host star, blocking a measurable portion of the light. Gillon’s team was able to observe only a single transit for TRAPPIST-1h, the farthest-out of the star’s seven progeny, prior to the data analyzed by Luger鈥檚 team.

Luger led a multi-institution international research team that studied the TRAPPIST-1 system more closely using 79 days of observation data from K2, the second mission of the Kepler Space Telescope. The team was able to observe and study four transits of TRAPPIST-1h across its star.

The team used the K2 data to further characterize the orbits of the other six planets, help rule out the presence of additional transiting planets, and determine the rotation period and activity level of the star. They also discovered that TRAPPIST-1’s seven planets appear linked in a complex dance known as an where their respective orbital periods are mathematically related and slightly influence each other.

“Resonances can be tricky to understand, especially between three bodies. But there are simpler cases that are easier to explain,” Luger said. For instance, closer to home, Jupiter’s moons Io, Europa and Ganymede are set in a 1:2:4 resonance, meaning that Europa’s orbital period is exactly twice that of Io, and Ganymede’s is exactly twice that of Europa.

These relationships, Luger said, suggested that by studying the orbital velocities of its neighbor planets they could predict the exact orbital velocity, and hence also orbital period, of TRAPPIST-1h even before the K2 observations. Their theory proved correct when they located the planet in the K2 data.

TRAPPIST-1’s seven-planet chain of resonances established a record among known planetary systems, the previous holders being the systems Kepler-80 and Kepler-223, each with four resonant planets. The resonances are “self-correcting,” Luger said, such that if one planet were to somehow be nudged off course, it would lock right back into resonance. “Once you’re caught into this kind of stable resonance, it’s hard to escape,” he said.

All of this, Luger said, indicates that these orbital connections were forged early in the life of the TRAPPIST-1 system, when the planets and their orbits were not fully formed.

“The resonant structure is no coincidence, and points to an interesting dynamical history in which the planets likely migrated inward in lock-step,” Luger said. “This makes the system a great testbed for planet formation and migration theories.”

It also means that while TRAPPIST-1h is now extremely cold 鈥� with an average temperature of 173 Kelvin (minus 148 F) 鈥� it likely spent several hundred million years in a much warmer state, when its host star was younger and brighter.

“We could therefore be looking at a planet that was once habitable and has since frozen over, which is amazing to contemplate and great for follow-up studies,” Luger said.

Luger said he has been working with data from the K2 mission for a while now, researching ways to reduce “instrumental noise” in its data resulting from broken reaction wheels 鈥� small flywheels that help position the spacecraft 鈥� that can overwhelm planetary signals.

鈥淥bserving TRAPPIST-1 with K2 was an ambitious task,鈥� said Marko Sestovic, a doctoral student at the University of Bern and second author of the study. In addition to the extraneous signals introduced by the spacecraft鈥檚 wobble, the faintness of the star in the optical (the range of wavelengths where K2 observes) placed TRAPPIST-1h 鈥渘ear the limit of what we could detect with K2,鈥� he said. To make matters worse, Sestovic said, one transit of the planet coincided with a transit of TRAPPIST-1b, and one coincided with a stellar flare, adding to the difficulty of the observation. 鈥淔inding the planet was really encouraging,鈥� Luger said, 鈥渟ince it showed we can still do high-quality science with Kepler despite significant instrumental challenges.鈥�

Luger’s UW co-authors are astronomy doctoral students and , post-doctoral researcher and professor (Guggenheim Fellow). Agol separately helped confirm the approximate mass of TRAPPIST-1 planets with a technique he and colleagues devised called “” that describes planets’ gravitational tugs on one another.

Luger said the TRAPPIST-1 system’s relative nearness “makes it a prime target for follow-up and characterization with current and upcoming telescopes, which may be able to give us information about these planets’ atmospheric composition.”

Contributing to this discovery are researchers at the University of Bern in Switzerland; Paris Diderot and Paris Sorbonne Universities and the CEA Saclay in France; the University of Li猫ge in Belgium; the University of Chicago; the University of California, San Diego; California Institute of Technology; the University of Bordeaux in France; the University of Cambridge in England; NASA’s Ames Research Center, Goddard Space Flight Center, and Johnson Space Center; Massachusetts Institute of Technology; the University of Central Lancashire in England; King Abdulaziz University in Saudi Arabia; Cadi Ayyad University in Morocco; and the University of Geneva in Switzerland.

The research was funded by the via the UW-based as well as a National Science Foundation Graduate Student Research Fellowship, the Swiss National Science Foundation, the Simons Foundation, the European Research Council and the UK Science and Technology Facilities Council, among other agencies.

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For more information, visit or contact Luger at 206-543-6276 or rodluger@uw.edu

• Watch a video about the TRAPPIST-1 systems’s orbital resonances:

The animation shows a simulation of the聽planets of TRAPPIST-1 orbiting for 90 Earth-days. After 15 Earth days,聽the animation聽focuses only on the outer three planets: TRAPPIST-1f,聽TRAPPIST-1g,聽TRAPPIST-1h. The motion freezes each time two adjacent planets pass each other; an arrow appears pointing to the location of the third planet.聽This complex but predictable pattern, called an orbital resonance, occurs when planets exert a regular, periodic gravitational tug on each other as they orbit their star.聽The three-body resonance聽of the outer three planets聽causes the planets to repeat the same relative positions, and expecting such a resonance was used to predict the orbital period of TRAPPIST-1h. 聽

By Daniel Fabrycky / University of Chicago; with reference to聽Luger聽et al. 2017, Nature Astronomy

天美影视传媒 astronomy professor is part of the large team of researchers that has just announced confirmation of several Earth-sized, potentially habitable planets orbiting a star about 40 light-years (235 trillion miles) away.

Astronomers with NASA today, Feb. 22, of the first known planetary system with seven Earth-sized planets orbiting a single star, called TRAPPIST-1, in the Aquarius constellation.

Three of the planets lie well within the star’s habitable zone, the swath of space around a star just right to allow a rocky planet to have liquid water 鈥� necessary for life 鈥� on its surface. But all seven could support surface water, given the right atmospheric conditions, according to the research team.

Agol helped confirm the approximate mass of the planets using a technique he and colleagues proposed in 2005 called “transit timing variation” analysis, or TTV. He collaborated on the TTV analysis with astronomers Brice Olivier-Demory at the University of Bern, Switzerland; and Katherine Deck of the California Institute of Technology.

This method, Agol said, “uses the fact that as the planets orbit the star and pass one another, they behave like distracted drivers turning their heads to look at one another each time they pass, swerving slightly in their orbits.” The larger the mass of the planets, he said, the stronger their gravitational tugs are on one another relative to the star, and the more significantly their orbits swerve.

“This variation can be seen each time the planet transits, or passes the star. Sometimes the planet will arrive early, sometimes late, depending on how strongly it interacted with the other planets during its prior orbit of the star.” The colleagues each analyzed transit times for the planets orbiting TRAPPIST-1 separately, Agol said, and then combined their results.

Modeling these variations with Newton’s Law of Gravity, Agol said, the team was able to infer the planet-to-star mass ratio, so that measuring the mass of the star gave them the masses of the planets.

Agol added: “This is the first time that planet masses have been inferred for such small, temperate, Earth-sized planets, which is what makes this result particularly exciting for astronomers and planetary scientists.”

Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate in Washington, D.C., said, “This discovery could be a significant piece in the puzzle of finding habitable environments, places that are conducive to life. Answering the question 鈥榓re we alone鈥� is a top science priority and finding so many planets like these for the first time in the habitable zone is a remarkable step forward toward that goal.”

The research team confirmed the planets using the NASA Spitzer Space Telescope, the TRAPPIST-South telescope at the European Southern Observatory’s La Silla Observatory and other telescopes around the world. The planets are labeled TRAPPIST- 1b, c, d, e, f, g and h, in order of increasing distance from the cool parent star, a red dwarf. The discovery sets a new record for the greatest number of planets in the habitable zone of a single star beyond the solar system.

The TRAPPIST-1 star is classified as an “ultra-cool dwarf” 鈥� cool enough to allow liquid water even on the surface of rocky planets orbiting close in. All seven of the confirmed planets are closer to their host star than Mercury is to the sun. The star is also small, about 8 percent the mass of the sun. The cool nature of the host star inspired NASA, in its news release, to cast a Disney spin on the research, calling it “Ultracool Dwarf and the Seven Planets.”

NASA reports that the planets are so close to each other, people who stood on the surface of one might be able to look up and see geological features or clouds of neighboring worlds, some appearing even larger than the moon in Earth’s sky.

Agol said in the coming year he and colleagues will collect more data with the Spitzer Space Telescope and other ground-based telescopes, “which will greatly improve our precision in measuring the planet masses.”

Then, he said, they might be able to distinguish whether the planets are rocky with iron 鈥� like Earth 鈥� or maybe rocky without iron or surrounded by a thick atmosphere or ocean.

“It’s exciting to have the first mass estimates,” Agol said, “it will be even more exciting in the future when we can measure precise masses 鈥� and thus learn something about the compositions of these planets.”

Lead author of the paper is Micha毛l Gillon of the University of Li猫ge in Belgium. Gillon also lead a team of astronomers that in 2016 announced the discovery of three planets orbiting TRAPPIST-1. That find inspired the intense follow-up study that resulted in confirmation of all seven planets, due in part to Agol’s work.

The large research team includes astronomers from the NASA, the UW-based Virtual Planetary Laboratory and researchers in the United Kingdom, Switzerland, Belgium, France, Morocco, South Africa, Saudi Arabia and the European Organization for Astronomical Research in the聽 Southern Hemisphere.

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This was adapted from a . For more information on the UW’s involvement in this major discovery, contact Agol at 206-543-7106 or agol@uw.edu.

What looked at first like a sort of upside-down planet has instead revealed a new method for studying binary star systems, discovered by a 天美影视传媒 student astronomer.

Working with UW astronomer , doctoral student has confirmed the first “self-lensing” binary star system 鈥� one in which the mass of the closer star can be measured by how powerfully it magnifies light from its more distant companion star. Though our sun stands alone, about 40 percent of similar stars are in binary (two-star) or multi-star systems, orbiting their companions in a gravitational dance.

Kruse’s discovery confirms an astronomer’s prediction in 1973, based on stellar evolution models of the time, that such a system should be possible. A by Kruse and Agol was published in the April 18 edition of Science.

Like so many interesting discoveries, this one happened largely by accident.

Astronomers detect planets too far away for direct observation by the dimming in light when a world passes in front of, or transits, its host star. Kruse was looking for transits others might have missed in data from the planet-hunting when he saw something in the binary star system KOI-3278 that didn’t make sense.

“I found what essentially looked like an upside-down planet,” Kruse said. “What you normally expect is this dip in brightness, but what you see in this system is basically the exact opposite 鈥� it looks like an anti-transit.”

The two stars of KOI-3278, about 2,600 light-years (a light-year is 5.88 trillion miles) away in the Lyra constellation, take turns being nearer to Earth as they orbit each other every 88.18 days. They are about 43 million miles apart, roughly the distance the planet Mercury is from the sun. The white dwarf, a cooling star thought to be in the final stage of life, is about Earth’s size but 200,000 times more massive.

That increase in light, rather than the dip Kruse thought he’d see, was the white dwarf bending and magnifying light from its more distant neighbor through gravitational lensing, like a magnifying glass.

“The basic idea is fairly simple,” Agol said. “Gravity warps space and time and as light travels toward us it actually gets bent, changes direction. So, any gravitational object 鈥� anything with mass 鈥� acts as a magnifying glass,” though a weak one. “You really need large distances for it to be effective.”

“The cool thing, in this case, is that the lensing effect is so strong, we are able to use that to measure the mass of the closer, white dwarf star. And instead of getting a dip now you get a brightening through the gravitational magnification.”

This finding improves on in 2013 by the California Institute of Technology, which detected a similar self-lensing effect minus the brightening of the light because the two stars being studied were much closer together.

“The effect in this system is much stronger,” said Agol. “The larger the distance, the more the effect.”

Gravitational lensing is a common tool in astronomy. It has been used to detect planets around distant stars within the Milky Way galaxy, and was among the first methods used to confirm Albert Einstein’s general theory of relativity. Lensing within the Milky Way galaxy, such as this, is called microlensing.

But until now, the process had only been used in the fleeting instances of a nearby and distant star, not otherwise associated in any way, aligning just right, before going their separate ways again.

“The chance is really improbable,” said Agol. “As those two stars go through the galaxy they’ll never come back again, so you see that microlensing effect once and it never repeats. In this case, though, because the stars are orbiting each other, it repeats every 88 days.”

White dwarfs are important to astronomy, and are used as indicators of age in the galaxy, the astronomers said. Basically embers of burned-out stars, white dwarfs cool off at a specific rate over time. With this lensing, astronomers can learn with much greater precision what its mass and temperature are, and follow-up observations may yield its size.

By expanding their understanding of white dwarfs, astronomers take a step closer to learning about the age of the galaxy.

“This is a very significant achievement for a graduate student,” Agol said.

The two have sought time to use the Hubble Space Telescope to study KOI-3278 in more detail, and to see if there are other such star systems waiting to be discovered in the Kepler data.

“If everyone’s missed this one, then there could be many more that everyone’s missed as well,” said Kruse.

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The research was funded by grants from the National Science Foundation (#AST 0645416) and NASA (#12-OSS12-0011). For more information, contact Agol at 206-543-7106 or agol@astro.washington.edu; or Kruse at 845-499-1384 or eakruse@uw.edu.

天美影视传媒 astronomer played a key role in the windfall of 715 new exoplanets . Agol was on a team that found seven of those worlds, all in orbit around the same star, Kepler-90. It’s the first planetary system with seven planets seen to transit, or cross in front of their host star.

Agol, colleague Josh Carter of the Harvard-Smithsonian Center for Astrophysics and co-authors discovered the multiple planets (though published findings before ) and helped confirm the high likelihood that the grouping is in fact a planetary system. News reports note that an amateur astronomer assisted in identifying the seventh planet.

The worlds were all detected via the Kepler Space Telescope. Many of the newly verified systems have multiple planets. The 715 worlds orbit 305 different stars, and the great majority are planets smaller than Neptune.

In the seven-planet system Kepler-90 there are two worlds about the size of Earth, three super-Earths 鈥� planets larger in mass than Earth but less than 10 times so 鈥� and two much larger planets. The smaller planets orbit closer to the star and the bigger ones further out, as in our system.

The system is about 2,500 light-years away, in the area of the Draco constellation. A light-year, the distance light travels in a year, is about 6 trillion miles. It’s a tightly packed grouping, too; the outermost planet orbits the host star at about the same distance Earth is from the sun.

Four of the 715 newly discovered worlds are less than 2.5 times the size of Earth and their orbits are within their host star’s habitable zone, the swath of space just right for an orbiting planet’s surface water to be in liquid form, thus potentially giving life a chance.

The NASA discovery substantially brings to 1,700 the total number of confirmed exoplanets, or worlds beyond our own solar system. Visit for more information about the Kepler mission.