MIT’s Lennon Rodgers, a research scientist who did graduate work in the MIT Space Systems Laboratory (SSL), led a team of students to build a universal docking port (UDP) for the Synchronized Position Hold, Engage, Reorient Experimental Satellites (SPHERES) testbed on the International Space Station (ISS). The flight versions were subsequently developed by graduate students Duncan Miller, David Sternberg, and Chris Jewison, working with Aurora Flight Sciences Corp., and launched to the ISS from Kazakhstan on Wednesday. The SPHERES with UDPs will be used to test autonomous, vision-based algorithms for complex docking maneuvers. Rodgers spoke with MIT News about what he hopes this mission will accomplish.

Q: What was the inspiration for this docking system, and what were some of the issues and challenges involved in coming up with a workable system?

A: We were initially exploring the feasibility of modular spacecraft, which is the idea that a spacecraft could be composed of multiple modules assembled in orbit. One application is the primary mirror of a large, space-based telescope. Instead of being limited by the size of the rocket, the mirror could be composed of multiple module segments and assembled in orbit. Another is testing algorithms for docking to a tumbling spacecraft.

So we set out to build a mechanism for connecting multiple SPHERES together autonomously and rigidly. A key requirement was that identical ports needed to connect to each other, which we referred to as “universal.” I worked with students as part of the [Department of Aeronautics and Astronautics] senior design class to design and build, in the AeroAstro machine shop, the mechanical components, and then continued to develop a camera-based sensor as part of my thesis.

Q: Can you describe how the system will work when it begins its tests on the ISS? What will a typical test run look like, and what kinds of operations will be carried out over time?

A: The UDPs will go through a checkout procedure by the astronauts and subsequently be mounted to the SPHERES already aboard the ISS. Then current SSL graduate students will perform remote tests from their control room in the SSL to validate their models and achieve docking in orbit in a variety of highly dynamic scenarios. Thrusters and sensors will be intentionally faulted to simulate failures. The team will also test novel navigation, autonomy, and reconfigurable control algorithms for the docked system. The UDPs will eventually be used for the Zero Robotics program, where middle and high school student teams compete by programming a SPHERES satellite to achieve virtual goals.

Q: What is the ultimate goal of this research, and what kinds of reconfigurable satellite systems might this research help to bring about?

A: The ultimate goal for the SPHERES docking port system is to provide an open testing platform for autonomous satellite assembly in zero gravity. The flight of the UDPs will be followed by a launch of [systems that] will enable a larger range of docking formations and autonomous satellite reconfiguration. This technology has applications to many next-generation space systems, including satellite servicing and assembly, large telescopes, space debris removal, and asteroid sampling.

UDPs are part of a long string of exciting space-based projects that the MIT Space Systems Lab has done and will be doing over the coming years under the direction of Professor David Miller and SSL director Alvar Saenz-Otero. There are a few planned hardware launches, including the launch of the REXIS instrument for the NASA OSIRIS-REx mission to an asteroid called Bennu, and the launch of MicroMAS 2 and MiRaTa, which are small weather satellites. This is a thrilling time for space research, especially for students and researchers at MIT.

By David L. Chandler | MIT News Office

For the last decade, astronomers have observed curious “hotspots” on Saturn’s poles. In 2008, NASA’s Cassini spacecraft beamed back close-up images of these hotspots, revealing them to be immense cyclones, each as wide as the Earth. Scientists estimate that Saturn’s cyclones may whip up 300 mph winds, and likely have been churning for years.

While cyclones on Earth are fueled by the heat and moisture of the oceans, no such bodies of water exist on Saturn. What, then, could be causing such powerful, long-lasting storms?

In a paper published today in the journal Nature Geoscience, atmospheric scientists at MIT propose a possible mechanism for Saturn’s polar cyclones: Over time, small, short-lived thunderstorms across the planet may build up angular momentum, or spin, within the atmosphere — ultimately stirring up a massive and long-lasting vortex at the poles.

The researchers developed a simple model of Saturn’s atmosphere, and simulated the effect of multiple small thunderstorms forming across the planet over time. Eventually, they observed that each thunderstorm essentially pulls air towards the poles — and together, these many small, isolated thunderstorms can accumulate enough atmospheric energy at the poles to generate a much larger and long-lived cyclone.

The team found that whether a cyclone develops depends on two parameters: the size of the planet relative to the size of an average thunderstorm on it, and how much storm-induced energy is in its atmosphere. Given these two parameters, the researchers predicted that Neptune, which bears similar polar hotspots, should generate transient polar cyclones that come and go, while Jupiter should have none.

Morgan O’Neill, the paper’s lead author and a former PhD student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS), says the team’s model may eventually be used to gauge atmospheric conditions on planets outside the solar system. For instance, if scientists detect a cyclone-like hotspot on a far-off exoplanet, they may be able to estimate storm activity and general atmospheric conditions across the entire planet.

“Before it was observed, we never considered the possibility of a cyclone on a pole,” says O’Neill, who is now a postdoc at the Weizmann Institute of Science in Israel.

“Only recently did Cassini give us this huge wealth of observations that made it possible, and only recently have we had to think about why [polar cyclones] occur.”

O’Neill’s co-authors are Kerry Emanuel, the Cecil and Ida Green Professor of Earth, Atmospheric and Planetary Sciences, and Glenn Flierl, a professor of oceanography in EAPS.

Beta-drifting toward a cyclone

Polar cyclones on Saturn are a puzzling phenomenon, since the planet, known as a gas giant, lacks an essential ingredient for brewing up such storms: water on its surface.

“There’s no surface at all — it just gets denser as you get deeper,” O’Neill says. “If you lack choppy waters or a frictional surface that allows wind to converge, which is how hurricanes form on Earth, how can you possibly get something that looks similar on a gas giant?”

The answer, she found, may be something called “beta drift” — a phenomenon by which a planet’s spin causes small thunderstorms to drift toward the poles. Beta drift drives the motion of hurricanes on Earth, without requiring the presence of water. When a storm forms, it spins in one direction at the surface, and the opposite direction toward the upper atmosphere, creating a “dipole of vorticity.” (In fact, videos of hurricanes taken from space actually depict the storm’s spin as opposite to what’s observed on the ground.)

“The whole atmosphere is kind of being dragged by the planet as the planet rotates, so all this air has some ambient angular momentum,” O’Neill explains. “If you converge a bunch of that air at the base of a thunderstorm, you’re going to get a small cyclone.”

The combination of a planet’s rotation and a circulating storm generates secondary features called beta gyres that wrap around a storm and essentially split its dipole in half, tugging the top half toward the equator, and the bottom half toward the pole.

The team developed a model of Saturn’s atmosphere and ran hundreds of simulations for hundreds of days each, allowing small thunderstorms to pop up across the planet. The researchers observed that multiple thunderstorms experienced beta drift over time, and eventually accumulated enough atmospheric circulation to create a much larger cyclone at the poles.

“Each of these storms is beta-drifting a little bit before they sputter out and die,” O’Neill says. “This mechanism means that little thunderstorms — fast, abundant, but not very strong thunderstorms — over a long period of time can actually accumulate so much angular momentum right on the pole, that you get a permanent, wildly strong cyclone.”

Next stop: Jupiter

The team also explored conditions in which planets would not form polar cyclones, even though they may experience thunderstorms. The researchers found that whether a polar cyclone forms depends on two parameters: the energy within a planet’s atmosphere, or the total intensity of its thunderstorms; and the average size of its thunderstorms, relative to the size of the planet itself. Specifically, the larger an average thunderstorm compared to a planet’s size, the more likely a polar cyclone is to develop.

O’Neill applied this relationship to Saturn, Jupiter, and Neptune. In the case of Saturn, the planet’s atmospheric conditions and storm activity are within the range that would generate a large polar cyclone. In contrast, Jupiter is unlikely to host any polar cyclones, as the ratio of any storm to its overall size would be extremely small. The dimensions of Neptune suggest that polar cyclones may exist there, albeit on a fleeting basis.

“Saturn has an intense cyclone at each pole,” says Andrew Ingersoll, professor of planetary science at Caltech, who was not involved in the study. “The model successfully accounts for that. Jupiter doesn’t seem to have polar cyclones like Saturn’s, but Jupiter isn’t tipped over as much as Saturn, so we don’t get a good view of the poles. Thus the apparent absence of polar cyclones on Jupiter is still a mystery.”

The researchers are eager to see whether their predictions, particularly for Jupiter, bear out. Next summer, NASA’s Juno spacecraft is scheduled to enter into an orbit around Jupiter, kicking off a one-year mission to map and explore Jupiter’s atmosphere.

“If what we know about Jupiter currently is correct, we predict that we won’t see these wildly strong cyclones,” O’Neill says. “We’ll find out next year if our predictions are true.”

This research was funded in part by the National Science Foundation.

By Jennifer Chu | MIT News Office

Viewed from above, our solar system’s planetary orbits around the sun resemble rings around a bulls-eye. Each planet, including Earth, keeps to a roughly circular path, always maintaining the same distance from the sun.

For decades, astronomers have wondered whether the solar system’s circular orbits might be a rarity in our universe. Now a new analysis suggests that such orbital regularity is instead the norm, at least for systems with planets as small as Earth.  

In a paper published in the Astrophysical Journal, researchers from MIT and Aarhus University in Denmark report that 74 exoplanets, located hundreds of light-years away, orbit their respective stars in circular patterns, much like the planets of our solar system.

These 74 exoplanets, which orbit 28 stars, are about the size of Earth, and their circular trajectories stand in stark contrast to those of more massive exoplanets, some of which come extremely close to their stars before hurtling far out in highly eccentric, elongated orbits.

“Twenty years ago, we only knew about our solar system, and everything was circular and so everyone expected circular orbits everywhere,” says Vincent Van Eylen, a visiting graduate student in MIT’s Department of Physics. “Then we started finding giant exoplanets, and we found suddenly a whole range of eccentricities, so there was an open question about whether this would also hold for smaller planets. We find that for small planets, circular is probably the norm.”

Ultimately, Van Eylen says that’s good news in the search for life elsewhere. Among other requirements, for a planet to be habitable, it would have to be about the size of Earth — small and compact enough to be made of rock, not gas. If a small planet also maintained a circular orbit, it would be even more hospitable to life, as it would support a stable climate year-round. (In contrast, a planet with a more eccentric orbit might experience dramatic swings in climate as it orbited close in, then far out from its star.)

“If eccentric orbits are common for habitable planets, that would be quite a worry for life, because they would have such a large range of climate properties,” Van Eylen says. “But what we find is, probably we don’t have to worry too much because circular cases are fairly common.”

Star-crossed numbers

In the past, researchers have calculated the orbital eccentricities of large, “gas giant” exoplanets using radial velocity — a technique that measures a star’s movement. As a planet orbits a star, its gravitational force will tug on the star, causing it to move in a pattern that reflects the planet’s orbit. However, the technique is most successful for larger planets, as they exert enough gravitational pull to influence their stars.

Researchers commonly find smaller planets by using a transit-detecting method, in which they study the light given off by a star, in search of dips in starlight that signify when a planet crosses, or “transits,” in front of that star, momentarily diminishing its light. Ordinarily, this method only illuminates a planet’s existence, not its orbit. But Van Eylen and his colleague Simon Albrecht, of Aarhus University, devised a way to glean orbital information from stellar transit data.

They first reasoned that if they knew the mass of a planet’s star, they could calculate how long a planet would take to orbit that star, if its orbit were circular. The mass of a star determines its gravitational pull, which in turn influences how fast a planet travels around the star.

By calculating a planet’s orbital velocity in a circular orbit, they could then estimate a transit’s duration — how long a planet would take to cross in front of a star. If the calculated transit matched an actual transit, the researchers reasoned that the planet’s orbit must be circular. If the transit were longer or shorter, the orbit must be more elongated, or eccentric.

Not so eccentric

To obtain actual transit data, the team looked through data collected over the past four years by NASA’s Kepler telescope — a space observatory that surveys a slice of the sky in search of habitable planets. The telescope has monitored the brightness of over 145,000 stars, only a fraction of which have been characterized in any detail.

The team chose to concentrate on 28 stars for which mass and radius have previously been measured, using asteroseismology — a technique that measures stellar pulsations, which reflect a star’s mass and radius.

These 28 stars host multiplanet systems — 74 exoplanets in all. The researchers obtained Kepler data for each exoplanet, looking not only for the occurrence of transits, but also their duration. Given the mass and radius of the host stars, the team calculated each planet’s transit duration if its orbit were circular, then compared the estimated transit durations with actual transit durations from Kepler data.

Across the board, Van Eylen and Albrecht found the calculated and actual transit durations matched, suggesting that all 74 exoplanets maintain circular, not eccentric, orbits.

“We found that most of them matched pretty closely, which means they’re pretty close to being circular,” Van Eylen says. “We are very certain that if very high eccentricities were common, we would’ve seen that, which we don’t.”

Van Eylen says the orbital results for these smaller planets may eventually help to explain why larger planets have more extreme orbits.

“We want to understand why some exoplanets have extremely eccentric orbits, while in other cases, such as the solar system, planets orbit mostly circularly,” Van Eylen says. “This is one of the first times we’ve reliably measured the eccentricities of small planets, and it’s exciting to see they are different from the giant planets, but similar to the solar system.”

David Kipping, an astronomer at the Harvard-Smithsonian Center for Astrophysics, notes that Van Eylen’s sample of 74 exoplanets is a relatively small slice, considering the hundreds of thousands of stars in the sky.

“I think that the evidence for smaller planets having more circular orbits is presently tentative,” says Kipping, who was not involved in the research. “It prompts us to investigate this question in more detail and see whether this is indeed a universal trend, or a feature of the small sample considered.”

In regard to our own solar system, Kipping speculates that with a larger sample of planetary systems, “one might investigate eccentricity as a function of multiplicity, and see whether the solar system’s eight planets are typical or not.”

This research was funded in part by the European Research Council.

By Jennifer Chu | MIT News Office

MIT’s Lennon Rodgers, a research scientist who did graduate work in the MIT Space Systems Laboratory (SSL), led a team of students to build a universal docking port (UDP) for the Synchronized Position Hold, Engage, Reorient Experimental Satellites (SPHERES) testbed on the International Space Station (ISS). The flight versions were subsequently developed by graduate students Duncan Miller, David Sternberg, and Chris Jewison, working with Aurora Flight Sciences Corp., and launched to the ISS from Kazakhstan on Wednesday. The SPHERES with UDPs will be used to test autonomous, vision-based algorithms for complex docking maneuvers. Rodgers spoke with MIT News about what he hopes this mission will accomplish.

Q: What was the inspiration for this docking system, and what were some of the issues and challenges involved in coming up with a workable system?

A: We were initially exploring the feasibility of modular spacecraft, which is the idea that a spacecraft could be composed of multiple modules assembled in orbit. One application is the primary mirror of a large, space-based telescope. Instead of being limited by the size of the rocket, the mirror could be composed of multiple module segments and assembled in orbit. Another is testing algorithms for docking to a tumbling spacecraft.

So we set out to build a mechanism for connecting multiple SPHERES together autonomously and rigidly. A key requirement was that identical ports needed to connect to each other, which we referred to as “universal.” I worked with students as part of the [Department of Aeronautics and Astronautics] senior design class to design and build, in the AeroAstro machine shop, the mechanical components, and then continued to develop a camera-based sensor as part of my thesis.

Q: Can you describe how the system will work when it begins its tests on the ISS? What will a typical test run look like, and what kinds of operations will be carried out over time?

A: The UDPs will go through a checkout procedure by the astronauts and subsequently be mounted to the SPHERES already aboard the ISS. Then current SSL graduate students will perform remote tests from their control room in the SSL to validate their models and achieve docking in orbit in a variety of highly dynamic scenarios. Thrusters and sensors will be intentionally faulted to simulate failures. The team will also test novel navigation, autonomy, and reconfigurable control algorithms for the docked system. The UDPs will eventually be used for the Zero Robotics program, where middle and high school student teams compete by programming a SPHERES satellite to achieve virtual goals.

Q: What is the ultimate goal of this research, and what kinds of reconfigurable satellite systems might this research help to bring about?

A: The ultimate goal for the SPHERES docking port system is to provide an open testing platform for autonomous satellite assembly in zero gravity. The flight of the UDPs will be followed by a launch of [systems that] will enable a larger range of docking formations and autonomous satellite reconfiguration. This technology has applications to many next-generation space systems, including satellite servicing and assembly, large telescopes, space debris removal, and asteroid sampling.

UDPs are part of a long string of exciting space-based projects that the MIT Space Systems Lab has done and will be doing over the coming years under the direction of Professor David Miller and SSL director Alvar Saenz-Otero. There are a few planned hardware launches, including the launch of the REXIS instrument for the NASA OSIRIS-REx mission to an asteroid called Bennu, and the launch of MicroMAS 2 and MiRaTa, which are small weather satellites. This is a thrilling time for space research, especially for students and researchers at MIT.

By David L. Chandler | MIT News Office

For the last decade, astronomers have observed curious “hotspots” on Saturn’s poles. In 2008, NASA’s Cassini spacecraft beamed back close-up images of these hotspots, revealing them to be immense cyclones, each as wide as the Earth. Scientists estimate that Saturn’s cyclones may whip up 300 mph winds, and likely have been churning for years.

While cyclones on Earth are fueled by the heat and moisture of the oceans, no such bodies of water exist on Saturn. What, then, could be causing such powerful, long-lasting storms?

In a paper published today in the journal Nature Geoscience, atmospheric scientists at MIT propose a possible mechanism for Saturn’s polar cyclones: Over time, small, short-lived thunderstorms across the planet may build up angular momentum, or spin, within the atmosphere — ultimately stirring up a massive and long-lasting vortex at the poles.

The researchers developed a simple model of Saturn’s atmosphere, and simulated the effect of multiple small thunderstorms forming across the planet over time. Eventually, they observed that each thunderstorm essentially pulls air towards the poles — and together, these many small, isolated thunderstorms can accumulate enough atmospheric energy at the poles to generate a much larger and long-lived cyclone.

The team found that whether a cyclone develops depends on two parameters: the size of the planet relative to the size of an average thunderstorm on it, and how much storm-induced energy is in its atmosphere. Given these two parameters, the researchers predicted that Neptune, which bears similar polar hotspots, should generate transient polar cyclones that come and go, while Jupiter should have none.

Morgan O’Neill, the paper’s lead author and a former PhD student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS), says the team’s model may eventually be used to gauge atmospheric conditions on planets outside the solar system. For instance, if scientists detect a cyclone-like hotspot on a far-off exoplanet, they may be able to estimate storm activity and general atmospheric conditions across the entire planet.

“Before it was observed, we never considered the possibility of a cyclone on a pole,” says O’Neill, who is now a postdoc at the Weizmann Institute of Science in Israel.

“Only recently did Cassini give us this huge wealth of observations that made it possible, and only recently have we had to think about why [polar cyclones] occur.”

O’Neill’s co-authors are Kerry Emanuel, the Cecil and Ida Green Professor of Earth, Atmospheric and Planetary Sciences, and Glenn Flierl, a professor of oceanography in EAPS.

Beta-drifting toward a cyclone

Polar cyclones on Saturn are a puzzling phenomenon, since the planet, known as a gas giant, lacks an essential ingredient for brewing up such storms: water on its surface.

“There’s no surface at all — it just gets denser as you get deeper,” O’Neill says. “If you lack choppy waters or a frictional surface that allows wind to converge, which is how hurricanes form on Earth, how can you possibly get something that looks similar on a gas giant?”

The answer, she found, may be something called “beta drift” — a phenomenon by which a planet’s spin causes small thunderstorms to drift toward the poles. Beta drift drives the motion of hurricanes on Earth, without requiring the presence of water. When a storm forms, it spins in one direction at the surface, and the opposite direction toward the upper atmosphere, creating a “dipole of vorticity.” (In fact, videos of hurricanes taken from space actually depict the storm’s spin as opposite to what’s observed on the ground.)

“The whole atmosphere is kind of being dragged by the planet as the planet rotates, so all this air has some ambient angular momentum,” O’Neill explains. “If you converge a bunch of that air at the base of a thunderstorm, you’re going to get a small cyclone.”

The combination of a planet’s rotation and a circulating storm generates secondary features called beta gyres that wrap around a storm and essentially split its dipole in half, tugging the top half toward the equator, and the bottom half toward the pole.

The team developed a model of Saturn’s atmosphere and ran hundreds of simulations for hundreds of days each, allowing small thunderstorms to pop up across the planet. The researchers observed that multiple thunderstorms experienced beta drift over time, and eventually accumulated enough atmospheric circulation to create a much larger cyclone at the poles.

“Each of these storms is beta-drifting a little bit before they sputter out and die,” O’Neill says. “This mechanism means that little thunderstorms — fast, abundant, but not very strong thunderstorms — over a long period of time can actually accumulate so much angular momentum right on the pole, that you get a permanent, wildly strong cyclone.”

Next stop: Jupiter

The team also explored conditions in which planets would not form polar cyclones, even though they may experience thunderstorms. The researchers found that whether a polar cyclone forms depends on two parameters: the energy within a planet’s atmosphere, or the total intensity of its thunderstorms; and the average size of its thunderstorms, relative to the size of the planet itself. Specifically, the larger an average thunderstorm compared to a planet’s size, the more likely a polar cyclone is to develop.

O’Neill applied this relationship to Saturn, Jupiter, and Neptune. In the case of Saturn, the planet’s atmospheric conditions and storm activity are within the range that would generate a large polar cyclone. In contrast, Jupiter is unlikely to host any polar cyclones, as the ratio of any storm to its overall size would be extremely small. The dimensions of Neptune suggest that polar cyclones may exist there, albeit on a fleeting basis.

“Saturn has an intense cyclone at each pole,” says Andrew Ingersoll, professor of planetary science at Caltech, who was not involved in the study. “The model successfully accounts for that. Jupiter doesn’t seem to have polar cyclones like Saturn’s, but Jupiter isn’t tipped over as much as Saturn, so we don’t get a good view of the poles. Thus the apparent absence of polar cyclones on Jupiter is still a mystery.”

The researchers are eager to see whether their predictions, particularly for Jupiter, bear out. Next summer, NASA’s Juno spacecraft is scheduled to enter into an orbit around Jupiter, kicking off a one-year mission to map and explore Jupiter’s atmosphere.

“If what we know about Jupiter currently is correct, we predict that we won’t see these wildly strong cyclones,” O’Neill says. “We’ll find out next year if our predictions are true.”

This research was funded in part by the National Science Foundation.

By Jennifer Chu | MIT News Office

Looking up through a telescope at the contours of the moon or at Saturn with its faint yet startlingly familiar ring system can be a life changing experience. But in the age of the Internet, sensors, and the ability to connect to observing equipment across the world from a simple desktop, it was perhaps only a matter of time before the attention of MIT’s Wallace Observatory team would turn to making their suite of off-campus telescopes work remotely.

The George R. Wallace Jr. Astrophysical Observatory (WAO), in Westford, Massachusetts, is a teaching and research facility run by the Planetary Astronomy Lab in the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS). Until now, students in the MIT observing courses 12.409 (Hands-on Astronomy: Observing Stars and Planets) and 12.410 (Observational Techniques of Optical Astronomy), have had to travel the 40 miles to and from Wallace to make their observations. But no more. Two years ago Wallace’s roll-off roof-shed that houses four 14-inch Celestron C14 telescopes was retrofitted with a custom system that allows it to be operated and scripted by a standard astronomy equipment language — and can stow the telescopes safely if bad weather arrives.

One of the greatest barriers to student data in the classes had been the two-hour round-trip transit time to WAO. Between getting there and getting back, an observing evening became such an investment of time that instructors needed to be very careful about deciding which nights to go, and which to let pass because they didn’t look like they were going to be quite good enough. With the new system based in the Green Building (Building 54), students can get started almost immediately when they and their telescopes are available — and if it should suddenly cloud up, they can close down and walk back to their dorms with only half an hour lost.

“After working on it for the past two years, we’ve at last ‘perfected’ the ability to observe with the C-14s remotely, so that by the end of the fall semester, 12.410 had students using the telescopes on Monday and Wednesday evenings from campus without the need to drive out to Wallace — without anyone being out there at all, actually,” says Michael Person, a research scientist in the Planetary Astronomy Lab and director of the Wallace Observatory.

The lion’s share of the work was carried out in-house by an assortment of stellar students in the Undergraduate Research Opportunities Programs and others, coordinated by site manager Tim Brothers. Effective and reliable design and installation of the custom shed opening and closing mechanism; acquisition, installation, and testing of remote weather sensors, and nightvision capable video cameras; as well as development of appropriate firewalls to protect the systems in Westford from hackers while allowing control from the designated remote observing lab in Cambridge, all had to come together to make observing direct from Building 54 a reality. 

Brothers, who also fully refurbished the vintage “orange tube” C-14s to their original specifications over this past summer, is pleased with how things are developing. He recently expressed excitement at the fact that continuing developments have allowed the beginning of automated observing — the ability to script observations from start to finish and to “wake up with tons of data waiting for us.” A recent milestone this spring was an entirely scripted observation containing two different data sets — an asteroid light curve and Pluto astrometry — on one telescope, resulting in almost eight hours’ worth of data.

Meanwhile, automation of the domes housing Wallace’s two largest telescopes — 24-inch and 16-inch Cassegrain reflectors — is still on the WAO’s to-do list. Person says, “My long-term goal is to have the entire site ready for fully remote operations, but having students able to use the shed telescopes remotely is a first big milestone.”

“We still can’t control the weather,” he adds ruefully, “but maybe someone else in the department is working on that.”

By Helen Hill | EAPS

Viewed from above, our solar system’s planetary orbits around the sun resemble rings around a bulls-eye. Each planet, including Earth, keeps to a roughly circular path, always maintaining the same distance from the sun.

For decades, astronomers have wondered whether the solar system’s circular orbits might be a rarity in our universe. Now a new analysis suggests that such orbital regularity is instead the norm, at least for systems with planets as small as Earth.  

In a paper published in the Astrophysical Journal, researchers from MIT and Aarhus University in Denmark report that 74 exoplanets, located hundreds of light-years away, orbit their respective stars in circular patterns, much like the planets of our solar system.

These 74 exoplanets, which orbit 28 stars, are about the size of Earth, and their circular trajectories stand in stark contrast to those of more massive exoplanets, some of which come extremely close to their stars before hurtling far out in highly eccentric, elongated orbits.

“Twenty years ago, we only knew about our solar system, and everything was circular and so everyone expected circular orbits everywhere,” says Vincent Van Eylen, a visiting graduate student in MIT’s Department of Physics. “Then we started finding giant exoplanets, and we found suddenly a whole range of eccentricities, so there was an open question about whether this would also hold for smaller planets. We find that for small planets, circular is probably the norm.”

Ultimately, Van Eylen says that’s good news in the search for life elsewhere. Among other requirements, for a planet to be habitable, it would have to be about the size of Earth — small and compact enough to be made of rock, not gas. If a small planet also maintained a circular orbit, it would be even more hospitable to life, as it would support a stable climate year-round. (In contrast, a planet with a more eccentric orbit might experience dramatic swings in climate as it orbited close in, then far out from its star.)

“If eccentric orbits are common for habitable planets, that would be quite a worry for life, because they would have such a large range of climate properties,” Van Eylen says. “But what we find is, probably we don’t have to worry too much because circular cases are fairly common.”

Star-crossed numbers

In the past, researchers have calculated the orbital eccentricities of large, “gas giant” exoplanets using radial velocity — a technique that measures a star’s movement. As a planet orbits a star, its gravitational force will tug on the star, causing it to move in a pattern that reflects the planet’s orbit. However, the technique is most successful for larger planets, as they exert enough gravitational pull to influence their stars.

Researchers commonly find smaller planets by using a transit-detecting method, in which they study the light given off by a star, in search of dips in starlight that signify when a planet crosses, or “transits,” in front of that star, momentarily diminishing its light. Ordinarily, this method only illuminates a planet’s existence, not its orbit. But Van Eylen and his colleague Simon Albrecht, of Aarhus University, devised a way to glean orbital information from stellar transit data.

They first reasoned that if they knew the mass of a planet’s star, they could calculate how long a planet would take to orbit that star, if its orbit were circular. The mass of a star determines its gravitational pull, which in turn influences how fast a planet travels around the star.

By calculating a planet’s orbital velocity in a circular orbit, they could then estimate a transit’s duration — how long a planet would take to cross in front of a star. If the calculated transit matched an actual transit, the researchers reasoned that the planet’s orbit must be circular. If the transit were longer or shorter, the orbit must be more elongated, or eccentric.

Not so eccentric

To obtain actual transit data, the team looked through data collected over the past four years by NASA’s Kepler telescope — a space observatory that surveys a slice of the sky in search of habitable planets. The telescope has monitored the brightness of over 145,000 stars, only a fraction of which have been characterized in any detail.

The team chose to concentrate on 28 stars for which mass and radius have previously been measured, using asteroseismology — a technique that measures stellar pulsations, which reflect a star’s mass and radius.

These 28 stars host multiplanet systems — 74 exoplanets in all. The researchers obtained Kepler data for each exoplanet, looking not only for the occurrence of transits, but also their duration. Given the mass and radius of the host stars, the team calculated each planet’s transit duration if its orbit were circular, then compared the estimated transit durations with actual transit durations from Kepler data.

Across the board, Van Eylen and Albrecht found the calculated and actual transit durations matched, suggesting that all 74 exoplanets maintain circular, not eccentric, orbits.

“We found that most of them matched pretty closely, which means they’re pretty close to being circular,” Van Eylen says. “We are very certain that if very high eccentricities were common, we would’ve seen that, which we don’t.”

Van Eylen says the orbital results for these smaller planets may eventually help to explain why larger planets have more extreme orbits.

“We want to understand why some exoplanets have extremely eccentric orbits, while in other cases, such as the solar system, planets orbit mostly circularly,” Van Eylen says. “This is one of the first times we’ve reliably measured the eccentricities of small planets, and it’s exciting to see they are different from the giant planets, but similar to the solar system.”

David Kipping, an astronomer at the Harvard-Smithsonian Center for Astrophysics, notes that Van Eylen’s sample of 74 exoplanets is a relatively small slice, considering the hundreds of thousands of stars in the sky.

“I think that the evidence for smaller planets having more circular orbits is presently tentative,” says Kipping, who was not involved in the research. “It prompts us to investigate this question in more detail and see whether this is indeed a universal trend, or a feature of the small sample considered.”

In regard to our own solar system, Kipping speculates that with a larger sample of planetary systems, “one might investigate eccentricity as a function of multiplicity, and see whether the solar system’s eight planets are typical or not.”

This research was funded in part by the European Research Council.

By Jennifer Chu | MIT News Office

On the 100th anniversary of Einstein’s theory of relativity, scientists at the Laser Interferometer Gravitational Observatory (LIGO) anticipate new opportunities to tease out one of the remaining mysteries of relativity theory. LIGO was designed to directly observe the gravitational waves predicted by Einstein’s remarkable theory in 1915 — a feat that, despite global participation by scientists in multiple projects, has not yet been accomplished.

This fall, LIGO — which was designed and operated by Caltech and MIT, with funding from the National Science Foundation — will reach a significant milestone as its newest incarnation, the Advanced LIGO detector, comes online. To mark this achievement, a day-long dedication ceremony is being held May 19 at the LIGO Hanford Observatory in Richland, Washington. LIGO research is carried out by the LIGO Scientific Collaboration, a group of some 950 researchers at universities around the United States and the world.

Nergis Mavalvala, the Curtis and Kathleen Marble Professor of Astrophysics at MIT, is a member of the LIGO Scientific Collaboration, a group of some 950 researchers at universities around the world who are working on the LIGO project. She explains the significance of LIGO’s new phase in gravitational wave detection.

Q: Einstein’s theory of general relativity is 100 years old this year. It has been very important in applications such as GPS, and tremendously successful in understanding astrophysical systems like black holes. Is there anything left to test about general relativity?

A: Yes. Gravitational waves, which are ripples in the fabric of space and time produced by violent events in the distant universe — for example, by the collision of two black holes or by the cores of supernova explosions — were predicted by Albert Einstein in 1916 as a consequence of his general theory of relativity. Gravitational waves are emitted by accelerating masses much in the same way  electromagnetic waves are produced by accelerating charges, such as radio waves radiated by electrons accelerating in antennas. As they travel to Earth, these ripples in the space-time fabric carry information about their violent origins and about the nature of gravity that cannot be obtained by traditional astronomical observations using light.

Gravitational waves have not yet been detected directly. Scientists do, however, have great confidence that they exist because their influence on a binary pulsar system (two neutron stars orbiting each other) has been measured accurately and is in excellent agreement with the predictions. Directly detecting gravitational waves will confirm Einstein’s prediction in a new regime of extreme relativistic conditions, and open a promising new window into some of the most violent and cataclysmic events in the cosmos.

Q: How do you directly detect gravitational waves?

A: According to Einstein’s theory, the relative distance between objects will change very slightly when a gravitational wave passes by. Researchers have built long L-shaped interferometers that use a laser split into two beams that travel back and forth down multi-kilometer-long arms. The interference between the beams is used to monitor the distance between precisely configured mirrors. When a gravitational wave passes through the interferometer, the distance between the mirrors changes by a distance of one-thousandth the size of a proton.

LIGO comprises two 4-km-long interferometers, one each at Hanford, Washington, and Livingston, Louisiana. The initial LIGO detectors that operated between 2000 and 2010 were sensitive enough to detect the collision and merging of two neutron stars out to the Virgo galaxy cluster, or 50 million light years away, but no detections of gravitational waves were made. Advanced LIGO, a new detector now being commissioned, is expected to be 10 times more sensitive and probe a thousand-fold greater volume of the universe.

Q: What will Advanced LIGO tell us about the universe?

A: With the 10-fold improvement in sensitivity comes a significant increase in the sensitive frequency range and the ability to tune the instrument for specific astrophysical sources. Advanced LIGO should allow scientists to observe the final death throes of pairs of neutron stars or black holes as they spiral closer to each other, coalesce into one larger black hole, and vibrate ever more faintly — a process much like two soap bubbles becoming one. Advanced LIGO will also allow scientists to zoom in on and study periodic signals from pulsars that spin as fast as a household blender, radiating gravitational waves at frequencies of many hundreds of Hertz (frequencies that correspond to high notes on an organ).

Advanced LIGO will also be used to search for the gravitational cosmic background that originated a mere 10-35 seconds after the Big Bang. Detecting the gravitational cosmic background would enable scientists to study the universe at its very inception: 400,000 years before the earliest glimmers of light — the cosmic microwave background — began to stream toward us.

Every time scientists have turned new instruments with unprecedented capabilities towards the cosmos, they have discovered amazing and unexpected things about our vast and mysterious universe. Advanced LIGO has the potential to be such a pioneering instrument, one that will allow scientists to observe the universe in a completely new way.  

By MIT Kavli Institute for Astrophysics and Space Research

Looking up through a telescope at the contours of the moon or at Saturn with its faint yet startlingly familiar ring system can be a life changing experience. But in the age of the Internet, sensors, and the ability to connect to observing equipment across the world from a simple desktop, it was perhaps only a matter of time before the attention of MIT’s Wallace Observatory team would turn to making their suite of off-campus telescopes work remotely.

The George R. Wallace Jr. Astrophysical Observatory (WAO), in Westford, Massachusetts, is a teaching and research facility run by the Planetary Astronomy Lab in the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS). Until now, students in the MIT observing courses 12.409 (Hands-on Astronomy: Observing Stars and Planets) and 12.410 (Observational Techniques of Optical Astronomy), have had to travel the 40 miles to and from Wallace to make their observations. But no more. Two years ago Wallace’s roll-off roof-shed that houses four 14-inch Celestron C14 telescopes was retrofitted with a custom system that allows it to be operated and scripted by a standard astronomy equipment language — and can stow the telescopes safely if bad weather arrives.

One of the greatest barriers to student data in the classes had been the two-hour round-trip transit time to WAO. Between getting there and getting back, an observing evening became such an investment of time that instructors needed to be very careful about deciding which nights to go, and which to let pass because they didn’t look like they were going to be quite good enough. With the new system based in the Green Building (Building 54), students can get started almost immediately when they and their telescopes are available — and if it should suddenly cloud up, they can close down and walk back to their dorms with only half an hour lost.

“After working on it for the past two years, we’ve at last ‘perfected’ the ability to observe with the C-14s remotely, so that by the end of the fall semester, 12.410 had students using the telescopes on Monday and Wednesday evenings from campus without the need to drive out to Wallace — without anyone being out there at all, actually,” says Michael Person, a research scientist in the Planetary Astronomy Lab and director of the Wallace Observatory.

The lion’s share of the work was carried out in-house by an assortment of stellar students in the Undergraduate Research Opportunities Programs and others, coordinated by site manager Tim Brothers. Effective and reliable design and installation of the custom shed opening and closing mechanism; acquisition, installation, and testing of remote weather sensors, and nightvision capable video cameras; as well as development of appropriate firewalls to protect the systems in Westford from hackers while allowing control from the designated remote observing lab in Cambridge, all had to come together to make observing direct from Building 54 a reality. 

Brothers, who also fully refurbished the vintage “orange tube” C-14s to their original specifications over this past summer, is pleased with how things are developing. He recently expressed excitement at the fact that continuing developments have allowed the beginning of automated observing — the ability to script observations from start to finish and to “wake up with tons of data waiting for us.” A recent milestone this spring was an entirely scripted observation containing two different data sets — an asteroid light curve and Pluto astrometry — on one telescope, resulting in almost eight hours’ worth of data.

Meanwhile, automation of the domes housing Wallace’s two largest telescopes — 24-inch and 16-inch Cassegrain reflectors — is still on the WAO’s to-do list. Person says, “My long-term goal is to have the entire site ready for fully remote operations, but having students able to use the shed telescopes remotely is a first big milestone.”

“We still can’t control the weather,” he adds ruefully, “but maybe someone else in the department is working on that.”

By Helen Hill | EAPS

The U.S. Senate yesterday unanimously confirmed the appointment of MIT Professor Dava Newman as NASA deputy administrator, the agency’s number-two position. The appointment will become official when signed by President Obama.

Newman is a professor of aeronautics and astronautics and of engineering systems. On the MIT faculty since 1993, she directs the Institute’s Technology and Policy Program and MIT Portugal Program, and is co-director of the Department of Aeronautics and Astronautics’ Man Vehicle Laboratory. She is a Harvard-MIT Division of Health Sciences and Technology faculty member, and a Margaret McVicar Faculty Fellow.

Accepting the confirmation, Newman said, “It’s an enormous honor to serve at NASA in times when our country is extending humanity’s reach into space while strengthening American leadership here on Earth. I’m profoundly grateful to President Obama, the United States Senate, and Administrator Bolden — along with everyone at MIT. I can’t wait to come aboard.” 

NASA Administrator Charles Bolden said, “I am delighted with the Senate confirmation of Dr. Dava Newman to be the deputy administrator of NASA. The strong bipartisan support Dr. Newman received in the Senate is a reflection of her well-earned reputation and renown as a global leader in science and technology research and policy.”

According to NASA, the deputy administrator “provides overall leadership, planning, and policy direction.” Her duties will include leading NASA governmental affairs; oversight of the agency’s offices, communications, and educational programs; and serving as the NASA representative to the multinational partnership that manages the International Space Station.

Newman received her BS from the University of Notre Dame. She earned MS degrees in aeronautics and astronautics and technology and policy in 1989 and a PhD in aerospace biomedical engineering in 1992, all from MIT.

Her research has included modeling human performance in low and micro-gravity conditions, examining the dynamics and control of astronaut motion, and the development of assisted walking devices for the physically handicapped. Perhaps her most prominent project has been development of the BioSuit, a skintight spacesuit that would give astronauts unprecedented comfort and freedom in exploration of planetary surfaces and extra-vehicular activity.

The deputy administrator position has been vacant since September 2013 when Lori Garver stepped down to accept a job with the Air Line Pilots Association.

By William Litant | Department of Aeronautics and Astronautics