An Old Glass Plate Hints at a Potential New Exoplanet Discovery

Polluted white dwarf
An artist's conception of a 'polluted white dwarf' star, plus debris disk. Image credit: NASA.

What’s the value to exoplanet science of sifting through old astronomical observations? Quite a lot, as a recent discovery out of the Carnegie Institution for Science demonstrates. A glass plate spectrum of a nearby solitary white dwarf known as Van Maanen’s Star shows evidence of rocky debris ringing the system, giving rise to a state only recently recognized as a ‘polluted white dwarf.’ Continue reading “An Old Glass Plate Hints at a Potential New Exoplanet Discovery”

Bayesian Analysis Rains On Exoplanet Life Parade

An exoplanet seen from its moon (artist's impression). Via the IAU.
An exoplanet seen from its moon (artist's impression). Via the IAU.

Is there life on other planets, somewhere in this enormous Universe? That’s probably the most compelling question we can ask. A lot of space science and space missions are pointed directly at that question.

The Kepler mission is designed to find exoplanets, which are planets orbiting other stars. More specifically, its aim is to find planets situated in the habitable zone around their star. And it’s done so. The Kepler mission has found 297 confirmed and candidate planets that are likely in the habitable zone of their star, and it’s only looked at a tiny patch of the sky.

But we don’t know if any of them harbour life, or if Mars ever did, or if anywhere ever did. We just don’t know. But since the question of life elsewhere in the Universe is so compelling, it’s driven people with intellectual curiosity to try and compute the likelihood of life on other planets.

One of the main ways people have tried to understand if life is prevalent in the Universe is through the Drake Equation, named after Dr. Frank Drake. He tried to come up with a way to compute the probability of the existence of other civilizations. The Drake Equation is a mainstay of the conversation around the existence of life in the Universe.

The Drake Equation is a way to calculate the probability of extraterrestrial civilizations in the Milky Way that were technologically advanced to communicate. When it was created in 1961, Drake himself explained that it was really just a way of starting a conversation about extraterrestrial civilizations, rather than a definitive calculation. Still, the equation is the starting point for a lot of conversations.

But the problem with the Drake equation, and with all of our attempts to understand the likelihood of life starting on other planets, is that we only have the Earth to go by. It seems like life on Earth started pretty early, and has been around for a long time. With that in mind, people have looked out into the Universe, estimated the number of planets in habitable zones, and concluded that life must be present, and even plentiful, in the Universe.

But we really only know two things: First, life on Earth began a few hundred million years after the planet was formed, when it was sufficiently cool and when there was liquid water. The second thing that we know is that a few billions of years after life started, creatures appeared which were sufficiently intelligent enough to wonder about life.

In 2012, two scientists published a paper which reminded us of this fact. David Spiegel, from Princeton University, and Edwin Turner, from the University of Tokyo, conducted what’s called a Bayesian analysis on how our understanding of the early emergence of life on Earth affects our understanding of the existence of life elsewhere.

A Bayesian analysis is a complicated matter for non-specialists, but in this paper it’s used to separate out the influence of data, and the influence of our prior beliefs, when estimating the probability of life on other worlds. What the two researchers concluded is that our prior beliefs about the existence of life elsewhere have a large effect on any probabilistic conclusions we make about life elsewhere. As the authors say in the paper, “Life arose on Earth sometime in the first few hundred million years after the young planet had cooled to the point that it could support water-based organisms on its surface. The early emergence of life on Earth has been taken as evidence that the probability of abiogenesis is high, if starting from young-Earth-like conditions.”

A key part of all this is that life may have had a head start on Earth. Since then, it’s taken about 3.5 billion years for creatures to evolve to the point where they can think about such things. So this is where we find ourselves; looking out into the Universe and searching and wondering. But it’s possible that life may take a lot longer to get going on other worlds. We just don’t know, but many of the guesses have assumed that abiogenesis on Earth is standard for other planets.

What it all boils down to, is that we only have one data point, which is life on Earth. And from that point, we have extrapolated outward, concluding hopefully that life is plentiful, and we will eventually find it. We’re certainly getting better at finding locations that should be suitable for life to arise.

What’s maddening about it all is that we just don’t know. We keep looking and searching, and developing technology to find habitable planets and identify bio-markers for life, but until we actually find life elsewhere, we still only have one data point: Earth. But Earth might be exceptional.

As Spiegel and Turner say in the conclusion of their paper, ” In short, if we should find evidence of life that arose wholly idependently of us – either via astronomical searches that reveal life on another planet or via geological and biological studies that find evidence of life on Earth with a different origin from us – we would have considerably stronger grounds to conclude that life is probably common in our galaxy.”

With our growing understanding of Mars, and with missions like the James Webb Space Telescope, we may one day soon have one more data point with which we can refine our probabilistic understanding of other life in the Universe.

Or, there could be a sadder outcome. Maybe life on Earth will perish before we ever find another living microbe on any other world.

An Earth-like Planet Only 16 Light Years Away?

An artistic representation of Gliese 832 c against a stellar nebula background. A new paper says Gliese 832 might be home to another planet similar to this, but in the habitable zone. Credit: Planetary Habitability Laboratory at the University of Puerto Rico, Arecibo, NASA/Hubble, Stellarium.
An artistic representation of Gliese 832 c against a stellar nebula background. A new paper says Gliese 832 might be home to another planet similar to this, but in the habitable zone. Credit: Planetary Habitability Laboratory at the University of Puerto Rico, Arecibo, NASA/Hubble, Stellarium.

Earth may have a new neighbour, in the form of an Earth-like planet in a solar system only 16 light years away. The planet orbits a star named Gliese 832, and that solar system already hosts two other known exoplanets: Gliese 832B and Gliese 832C. The findings were reported in a new paper by Suman Satyal at the University of Texas, and colleagues J. Gri?th, and Z. E. Musielak.

Gliese 832B is a gas giant similar to Jupiter, at 0.64 the mass of Jupiter, and it orbits its star at 3.5 AU. G832B probably plays a role similar to Jupiter in our Solar System, by setting gravitational equilibrium. Gliese 832C is a Super-Earth about 5 times as massive as Earth, and it orbits the star at a very close 0.16 AU. G832C is a rocky planet on the inner edge of the habitable zone, but is likely too close to its star for habitability. Gliese 832, the star at the center of it all, is a red dwarf about half the size of our Sun, in both mass and radius.

The newly discovered planet is still hypothetical at this point, and the researchers put its mass at between 1 and 15 Earth masses, and its orbit at between 0.25 to 2.0 AU from Gliese 582, its host star.

The two previously discovered planets in Gliese 832 were discovered using the radial velocity technique. Radial velocity detects planets by looking for wobbles in the host star, as it responds to the gravitational tug exerted on it by planets in orbit. These wobbles are observable through the Doppler effect, as the light of the affected star is red-shifted and blue-shifted as it moves.

The team behind this study re-analyzed the data from the Gliese 832 system, based on the idea that the vast distance between the two already-detected planets would be home to another planet. According to other solar systems studied by Kepler, it would be highly unusual for such a gap to exist.

As they say in their paper, the main thrust of the study is to explore the gravitational effect that the large outer planet has on the smaller inner planet, and also on the hypothetical Super-Earth that may inhabit the system. The team conducted numerical simulations and created models constrained by what’s known about the Gliese 832 system to conclude that an Earth-like planet may orbit Gliese 832.

This can all sound like some hocus-pocus in a way, as my non-science-minded friends like to point out. Just punch in some numbers until it shows an Earth-like planet, then publish and get attention. But it’s not. This kind of modelling and simulation is very rigorous.

Putting in all the data that’s known about the Gliese 832 system, including radial velocity data, orbital inclinations, and gravitational relationships between the planets and the star, and between the planets themselves, yields bands of probability where previously undetected planets might exist. This result tells planet hunters where to start looking for planets.

In the case of this paper, the result indicates that “there is a slim window of about 0.03 AU where an Earth-like planet could be stable as well as remain in the HZ.” The authors are quick to point out that the existence of this planet is not proven, only possible.

The other planets were found using the radial velocity method, which is pretty reliable. But radial velocity only provides clues to the existence of planets, it doesn’t prove that they’re there. Yet. The authors acknowledge that a larger number of radial velocity observations are needed to confirm the existence of this new planet. Barring that, either the transit method employed by the Kepler spacecraft, or direct observation with powerful telescopes, may also provide positive proof.

So far, the Kepler spacecraft has confirmed the existence of 1,041 planets. But Kepler can’t look everywhere for planets. Studies like these are crucial in giving Kepler starting points in its search for exoplanets. If an exoplanet can be confirmed in the Gliese 832 system, then it also confirms the accuracy of the simulation that the team behind this paper performed.

If confirmed, G832 C would join a growing list of exoplanets. It wasn’t long ago that we knew almost nothing about other solar systems. We only had knowledge of our own. And even though it was always unlikely that our Solar System would for some reason be special, we had no certain knowledge of the population of exoplanets in other solar systems.

Studies like this one point to our growing understanding of the dynamics of other solar systems, and the population of exoplanets in the Milky Way, and most likely throughout the cosmos.

NASA Invests In Radical Game-Changing Concepts For Exploration

Artist's concept of some of the Phase I winners of the 2016 NIAC program. Credit: NASA

Every year, the NASA Innovative Advanced Concepts (NIAC) program puts out the call to the general public, hoping to find better or entirely new aerospace architectures, systems, or mission ideas. As part of the Space Technology Mission Directorate, this program has been in operation since 1998, serving as a high-level entry point to entrepreneurs, innovators and researchers who want to contribute to human space exploration.

This year, thirteen concepts were chosen for Phase I of the NIAC program, ranging from reprogrammed microorganisms for Mars, a two-dimensional spacecraft that could de-orbit space debris, an analog rover for extreme environments, a robot that turn asteroids into spacecraft, and a next-generation exoplanet hunter. These proposals were awarded $100,000 each for a nine month period to assess the feasibility of their concept.

Continue reading “NASA Invests In Radical Game-Changing Concepts For Exploration”

The Aquarius Constellation

Aquarius the "Water Bearer" is a large but faint constellation in the Southern sky. Credit: Stellarium

Welcome back to Constellation Friday! Today, we will be dealing with one of the best-known constellations, that “watery” asterism and section of the sky known as Aquarius. Cue the soundtrack from Hair!

In the 2nd century CE, Greek-Egyptian astronomer Claudius Ptolemaeus (aka. Ptolemy) compiled a list of all the-then known constellations. This work (known as the Almagest) would remain the definitive guide to astronomy and astrology for over a thousand years. Among the 48 constellations listed in this book was Aquarius, a constellation of the zodiac that stretches from the celestial equator to the southern hemisphere.

Also known as the “Water Carrier”, Aquarius is bordered by Pegasus, Equuleus and Delphinus at the north, Aquila to the west, Capricornus to the south-west, Piscis Austrinus and Sculptor to the south, Cetus to the east and Pisces to the north-east. Today, it is one of the 88 constellations recognized by the International Astronomical Union (IAU), and is perhaps the most referenced and recognized of all the constellation.

Continue reading “The Aquarius Constellation”

NASA Thinks There’s a Way to Get to Mars in 3 Days

Interstellar travel will require near-light-speed to be feasible. Image: NASA
Interstellar travel will require near-light-speed to be feasible. Image: NASA

We’ve achieved amazing things by using chemical rockets to place satellites in orbit, land people on the Moon, and place rovers on the surface of Mars. We’ve even used ion drives to reach destinations further afield in our Solar System. But reaching other stars, or reducing our travel time to Mars or other planets, will require another method of travel. One that can approach relativistic speeds.

Your aim has to be really really good.
Your aim has to be really really good. Credit: UCSB Experimental Cosmology Group
We can execute missions to Mars, but it takes several months for a vehicle to reach the Red Planet. Even then, those missions have to be launched during the most optimal launch windows, which only occur every 2 years. But the minds at NASA never stop thinking about this problem, and now Dr. Philip Lubin, Physics Professor at the University of California, Santa Barbara, may have come up with something: photonic propulsion, which he thinks could reduce the travel time from Earth to Mars to just 3 days, for a 100 kg craft.

The system is called DEEP IN, or Directed Propulsion for Interstellar Exploration. The general idea is that we have achieved relativistic speeds in the laboratory, but haven’t taken that technology—which is electromagnetic in nature, rather than chemical—and used it outside of the laboratory. In short, we can propel individual particles to near light speed inside particle accelerators, but haven’t expanded that technology to the macro level.

Directed Energy Propulsion differs from rocket technology in a fundamental way: the propulsion system stays at home, and the craft doesn’t carry any fuel or propellant. Instead, the craft would carry a system of reflectors, which would be struck with an aimed stream of photons, propelling the craft forward. And the whole system is modular and scalable.

Photonic propulsion explained.
Photonic propulsion explained.

If that’s not tantalizing enough, the system can also be used to deflect hazardous space debris, and to detect other technological civilizations. As talked about in this paper, detecting these types of systems in use by other civilizations may be our best hope for discovering those civilizations.

There’s a roadmap for using this system, and it starts small. At first, DEEP IN would be used to launch small cube satellites. The feedback from this phase would then inform the next step, which would be to test a unit for defending the ISS from space debris. From then, the systems would meet goals of increasing complexity, from launching satellites to LEO (Low-Earth Orbit) and GEO (Geostationary Orbit), all the way up to asteroid deflection and planetary defense. After that, relativistic drives capable of interstellar travel is the goal.

There are lots of questions still to be answered of course, like what happens when a vehicle at near light-speed hits a tiny meteorite. But those questions will be asked and answered as the system is developed and its capabilities grow.

Obviously, DEEP IN has the potential to bring other stars into reach. This system could deliver probes to some of the more promising exo-planets, and give humanity its first detailed look at other solar systems. If DEEP IN can be successfully scaled up, as Lubin says, then it will be a transformational technology.

Here’s a longer video of Dr. Lubin explaining DEEP IN in greater depth and detail: http://livestream.com/viewnow/niac2015seattle

Here’s the website for the University of California Santa Barbara Experimental Cosmology Group: http://www.deepspace.ucsb.edu/

First Super-Earth Atmosphere Detected

A new paper says that a Super-Earth may have formed in our Solar System and been swallowed by the Sun. Image Credit: ESA/Hubble, M. Kornmesser
A new paper says that a Super-Earth may have formed in our Solar System and been swallowed by the Sun. Image Credit: ESA/Hubble, M. Kornmesser

55 Cancri-e was once touted as one of the most exotic exo-planets ever discovered. Mass and radius modelling led some astronomers to speculate that its interior could be rich in carbon. And that much carbon crushed together under extreme pressure = diamonds. That’s how it got its nickname “Diamond Planet.”

But 55 Cancri-e—now named “Janssen” (Thank you International Astronomical Union!)—is even more exotic with the recent discovery of an atmosphere. A February 7th research paper in the Astrophysical Journal, by a team of European astronomers, reports that Janssen has an atmosphere rich in hydrogen. This makes Janssen the first exo-planet, that we know of, to have an atmosphere.

The team used the Wide Field Camera 3 (WDF3) on the Hubble Space Telescope, and a new scanning technique, to gain an understanding of Janssen’s atmosphere. Along with hydrogen, the team also found helium, and potentially, hydrogen cyanide.

Given Janssen’s surface temperature of 2000 K (1727 C), and its proximity to its host star, the existence of an atmosphere is surprising. The team suspects that the hydrogen-rich atmosphere is left over from the planet’s formation 8 billion years ago, and is a remnant of the nebula that the planet and star formed from.

“Our observations of 55 Cancri e’s atmosphere suggest that the planet has managed to cling on to a significant amount of hydrogen and helium from the nebula from which it formed,” said Angelos Tsiaras, a PhD student at UCL, who helped develop the new scanning technique. “This is a very exciting result because it’s the first time that we have been able to find the spectral fingerprints that show the gases present in the atmosphere of a super-Earth.”

Super-Earths are the most common type of planet in our galaxy, though none exist in our solar system. They are called super-Earths because they have more mass than Earth, but are smaller than the gas giants. A greater understanding of super-Earths should mean a greater understanding of the most common type of planet around.

“This result gives a first insight into the atmosphere of a super-Earth. We now have clues as to what the planet is currently like, how it might have formed and evolved, and this has important implications for 55 Cancri e and other super-Earths,” said Professor Giovanna Tinetti of UCL.

The existence of hydrogen cyanide in Janssen’s atmosphere is also significant. Its presence indicates a carbon-rich atmosphere. This supports the idea that Janssen is a diamond planet, though that conclusion is still far from certain. “If the presence of hydrogen cyanide and other molecules is confirmed in a few years time by the next generation of infrared telescopes, it would support the theory that this planet is indeed carbon rich and a very exotic place,” said Professor Jonathan Tennyson, UCL.

The team has used their new technique on 2 other super-Earths, but no atmosphere was found.

55-Cancri e is about 40 light years from Earth. Its host star is slightly smaller, cooler, and a little dimmer than our Sun, and its year is shorter than an Earth day.

 

 

Time-lapse Video Documents Assembly of Webb Telescope Primary Mirror

This overhead shot of the James Webb Space Telescope shows part of the installation of the 18 primary flight mirrors onto the telescope structure in a clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Credits: NASA’s Goddard Space Flight Center/Chris Gunn See time-lapse video below
This rare overhead shot of the James Webb Space Telescope shows the nine primary flight mirrors installed on the telescope structure in a clean room at NASA's Goddard Space Flight Center in Greenbelt, Maryland.  Credits: NASA's Goddard Space Flight Center/Chris Gunn
This overhead shot of the James Webb Space Telescope shows part of the installation of the 18 primary flight mirrors onto the telescope structure in a clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Credits: NASA’s Goddard Space Flight Center/Chris Gunn
See time-lapse video below

NASA GODDARD SPACE FLIGHT CENTER, MD – A time-lapse video newly released by NASA documents the painstakingly complex assembly of the primary mirror at the heart of the biggest space telescope ever conceived by humankind – NASA’s James Webb Space Telescope (JWST).

Although the video, seen here, is short, it actually compresses over two and a half months of carefully choreographed and very impressive mirror installation process into less than 90 seconds. Continue reading “Time-lapse Video Documents Assembly of Webb Telescope Primary Mirror”

Largest Rocky World Found

An illustration of a large, rocky planet similar to the recently discovered BD+20594b. Image: JPL-Caltech/NASA
An illustration of a large, rocky planet similar to the recently discovered BD+20594b. Image: JPL-Caltech/NASA

We thought we understood how big rocky planets can get. But most of our understanding of planetary formation and solar system development has come from direct observation of our own Solar System. We simply couldn’t see any others, and we had no way of knowing how typical—or how strange—our own Solar System might be.

But thanks to the Kepler Spacecraft, and it’s ability to observe and collect data from other, distant, solar systems, we’ve found a rocky planet that’s bigger than we thought one could be. The planet, called BD+20594b, is half the diameter of Neptune, and composed entirely of rock.

The planet, whose existence was reported on January 28 at arXiv.org by astrophysicist Nestor Espinoza and his colleagues at the Pontifical Catholic University of Chile in Santiago, is over 500 light years away, in the constellation Aries.

BD+20594b is about 16 times as massive as Earth and half the diameter of Neptune. Its density is about 8 grams per cubic centimeter. It was first discovered in 2015 as it passed in between Kepler and its host star. Like a lot of discoveries, a little luck was involved. BD+20594b’s host star is exceptionally bright, which allowed more detailed observations than most exoplanets.

The discovery of BD+20594b is important for a couple of reasons: First, it shows us that there’s more going on in planetary formation than we thought. There’s more variety in planetary composition than we could’ve known from looking at our own Solar System. Second, comparing BD+20594b to other similar planets, like Kepler 10c—a previous candidate for largest rocky planet—gives astrophysicists an excellent laboratory for testing out our planet formation theories.

It also highlights the continuing importance of the Kepler mission, which started off just confirming the existence of exoplanets, and showing us how common they are. But with discoveries like this, Kepler is flexing its muscle, and starting to show us how our understanding of planetary formation is not as complete as we may have thought.

Earth From Afar Would Look Only 82% Right For Life

From Lunar orbit, Earth is obviously habitable. But from a distant point in the galaxy, not so much. Image: NASA/LRO.
From Lunar orbit, Earth is obviously habitable. But from a distant point in the galaxy, not so much. Image: NASA/LRO.

Right now, we’re staring hard at a small section of the sky, to see if we can detect any planets that may be habitable. The Kepler Spacecraft is focused on a tiny patch of sky in our Milky Way galaxy, hoping to detect planets as they transit in front of their stars. But if alien astronomers are doing the same, and detect Earth transiting in front of the Sun, how habitable would Earth appear?

You might think, because, well, here we are, that the Earth would look 100% habitable from a distant location. But that’s not the case. According to a paper from Rory Barnes and his colleagues at the University of Washington-based Virtual Planetary Laboratory, from a distant point in the galaxy, the probability of Earth being habitable might be only 82%.

Illustration of the Kepler spacecraft.(NASA/Kepler mission/Wendy Stenzel)
Illustration of the Kepler spacecraft.(NASA/Kepler mission/Wendy Stenzel)

Barnes and his team came up with the 82% number when they worked to create a “habitability index for transiting planets,” that seeks to rank the habitability of planets based on factors like the distance from its star, the size of the planet, the nature of the star, and the behaviour of other planets in the system.

The search for habitable exo-planets is dominated by the idea of the circumstellar habitable zone—or Goldilocks Zone—a region of space where an orbiting planet is not too close to its star to boil away all the water, and not so far away that the water is all frozen. This isn’t a fixed distance; it depends on the type and size of the star. With an enormous, hot star, the Goldilocks Zone would be much further away than Earth is from the Sun, and vice-versa for a smaller, cooler star. “That was a great first step, but it doesn’t make any distinctions within the habitable zone,” says Barnes.

Comparing a star's habitable zone based on its size. Credit: Fine Art America/Detlev Van Ravenswaay
Comparing a star’s habitable zone based on its size. Credit: Fine Art America/Detlev Van Ravenswaay.

Kepler has already confirmed the existence of over 1,000 exo-planets, with over 4,700 total candidate planets. And Kepler is still in operation. When it comes time to examine these planets more closely, with the James Webb Space Telescope and other instruments, where  do we start? We needed a way to rank planets for further study. Enter Barnes and his team, and their habitability index.

To rank candidates for further study, Barnes focused on not just the distance between the planet and the host star, but on the overall energy equilibrium. That takes into account not just the energy received by the planet, but the planet’s albedo—how much energy it reflects back into space. In terms of  being warm enough for life, a high-albedo planet can tolerate being closer to its star, whereas a low-albedo planet can tolerate a greater distance. This equilibrium is affected in turn by the eccentricity of the planet’s orbit.

The habitability index created by Barnes—and his colleagues Victoria Meadows and Nicole Evans—is a way to enter data, including a planet’s albedo and its distance from its host star, and get a number representing the planet’s probability of being habitable. “Basically, we’ve devised a way to take all the observational data that are available and develop a prioritization scheme,” said Barnes, “so that as we move into a time when there are hundreds of targets available, we might be able to say, ‘OK, that’s the one we want to start with.’”

So where does the Earth fit into all this? If alien astronomers are creating their own probability index, at 82%, Earth is a good candidate. Maybe they’re already studying us more closely.