Visions of Exoplanets: NASA report

In a new JPL report, Whitney Clavin gives an update on the imaging of exoplanets: impossible magic, or so we would have thought a generation ago. 

This image shows the HR 8799 planets with starlight optically suppressed and data processing conducted to remove residual starlight. The star is at the center of the blackened circle in the image. The four spots indicated with the letters b through e are the planets. This is a composite image using 30 wavelengths of light and was obtained over a period of 1.25 hours on June 14 and 15, 2012. Image courtesy of Project 1640 (NASA)

Gone are the days of being able to count the number of known planets on your fingers. Today, there are more than 800 confirmed exoplanets -- planets that orbit stars beyond our sun -- and more than 2,700 other candidates. What are these exotic planets made of? Unfortunately, you cannot stack them in a jar like marbles and take a closer look. Instead, researchers are coming up with advanced techniques for probing the planets' makeup. 

One breakthrough to come in recent years is direct imaging of exoplanets. Ground-based telescopes have begun taking infrared pictures of the planets posing near their stars in family portraits. But to astronomers, a picture is worth even more than a thousand words if its light can be broken apart into a rainbow of different wavelengths.

Those wishes are coming true as researchers are beginning to install infrared cameras on ground-based telescopes equipped with spectrographs. Spectrographs are instruments that spread an object's light apart, revealing signatures of molecules. Project 1640, partly funded by NASA's Jet Propulsion Laboratory, Pasadena, Calif., recently accomplished this goal using the Palomar Observatory near San Diego.

"In just one hour, we were able to get precise composition information about four planets around one overwhelmingly bright star," said Gautam Vasisht of JPL, co-author of the new study appearing in the Astrophysical Journal. "The star is a hundred thousand times as bright as the planets, so we've developed ways to remove that starlight and isolate the extremely faint light of the planets."

Along with ground-based infrared imaging, other strategies for combing through the atmospheres of giant planets are being actively pursued as well. For example, NASA's Spitzer and Hubble space telescopes monitor planets as they cross in front of their stars, and then disappear behind. NASA's upcoming James Webb Space Telescope will use a comparable strategy to study the atmospheres of planets only slightly larger than Earth.

In the new study, the researchers examined HR 8799, a large star orbited by at least four known giant, red planets. Three of the planets were among the first ever directly imaged around a star, thanks to observations from the Gemini and Keck telescopes on Mauna Kea, Hawaii, in 2008. The fourth planet, the closest to the star and the hardest to see, was revealed in images taken by the Keck telescope in 2010.

That alone was a tremendous feat considering that all planet discoveries up until then had been made through indirect means, for example by looking for the wobble of a star induced by the tug of planets.

Those images weren't enough, however, to reveal any information about the planets' chemical composition. That's where spectrographs are needed -- to expose the "fingerprints" of molecules in a planet's atmosphere. Capturing a distant world's spectrum requires gathering even more planet light, and that means further blocking the glare of the star.

Project 1640 accomplished this with a collection of instruments, which the team installs on the ground-based telescopes each time they go on "observing runs." The instrument suite includes a coronagraph to mask out the starlight; an advanced adaptive optics system, which removes the blur of our moving atmosphere by making millions of tiny adjustments to two deformable telescope mirrors; an imaging spectrograph that records 30 images in a rainbow of infrared colors simultaneously; and a state-of-the-art wave front sensor that further adjusts the mirrors to compensate for scattered starlight.

"It's like taking a single picture of the Empire State Building from an airplane that reveals a bump on the sidewalk next to it that is as high as an ant," said Ben R. Oppenheimer, lead author of the new study and associate curator and chair of the Astrophysics Department at the American Museum of Natural History, N.Y., N.Y.

Their results revealed that all four planets, though nearly the same in temperature, have different compositions. Some, unexpectedly, do not have methane in them, and there may be hints of ammonia or other compounds that would also be surprising. Further theoretical modeling will help to understand the chemistry of these planets.

Meanwhile, the quest to obtain more and better spectra of exoplanets continues. Other researchers have used the Keck telescope and the Large Binocular Telescope near Tucson, Ariz., to study the emission of individual planets in the HR8799 system. In addition to the HR 8799 system, only two others have yielded images of exoplanets. The next step is to find more planets ripe for giving up their chemical secrets. Several ground-based telescopes are being prepared for the hunt, including Keck, Gemini, Palomar and Japan's Subaru Telescope on Mauna Kea, Hawaii.

Ideally, the researchers want to find young planets that still have enough heat left over from their formation, and thus more infrared light for the spectrographs to see. They also want to find planets located far from their stars, and out of the blinding starlight. NASA's infrared Spitzer and Wide-field Infrared Survey Explorer (WISE) missions, and its ultraviolet Galaxy Evolution Explorer, now led by the California Institute of Technology, Pasadena, have helped identify candidate young stars that may host planets meeting these criteria.

"We're looking for super-Jupiter planets located faraway from their star," said Vasisht. "As our technique develops, we hope to be able to acquire molecular compositions of smaller, and slightly older, gas planets."

Still lower-mass planets, down to the size of Saturn, will be targets for imaging studies by the James Webb Space Telescope.

"Rocky Earth-like planets are too small and close to their stars for the current technology, or even for James Webb to detect. The feat of cracking the chemical compositions of true Earth analogs will come from a future space mission such as the proposed Terrestrial Planet Finder," said Charles Beichman, a co-author of the P1640 result and executive director of NASA's Exoplanet Science Institute at Caltech.

Though the larger, gas planets are not hospitable to life, the current studies are teaching astronomers how the smaller, rocky ones form.

"The outer giant planets dictate the fate of rocky ones like Earth. Giant planets can migrate in toward a star, and in the process, tug the smaller, rocky planets around or even kick them out of the system. We're looking at hot Jupiters before they migrate in, and hope to understand more about how and when they might influence the destiny of the rocky, inner planets," said Vasisht.

NASA's Exoplanet Science Institute manages time allocation on the Keck telescope for NASA. JPL manages NASA's Exoplanet Exploration program office. Caltech manages JPL for NASA. 
A visualization from the American Museum of Natural History showing where the HR 8799 system is in relation to our solar system is online at http://www.youtube.com/watch?v=yDNAk0bwLrU . 

More information about exoplanets and NASA's planet-finding program is at http://planetquest.jpl.nasa.gov .

Photonic Space

King Richard III team now digs up 1700 year old Roman cemetery

jet ring just after it had been uncovered

The University of Leicester, England, archaeological unit that discovered English King Richard III buried in a car park (as described in our February blog) has spearheaded another dig and discovered a 1,700-old- Roman cemetery – under another car park in Leicester.

The latest dig follows the historic discovery of King Richard III by colleagues from the same unit. 

The find has revealed remains thought to date back to 300AD – and includes personal items such as hairpins, rings, belt buckles and remains of shoes.

In addition, the team has found a jet ring with a curious symbol etched onto it, apparently showing the letters IX overlain.  Opinion as to its meaning is divided; it may just be an attractive design but it is also reminiscent of an early Christian symbol known as an IX (Iota-Chi) monogram taken from the initials of Jesus Christ in Greek.

The University of Leicester archaeologists have also identified the unusual practice of Christian burials alongside pagan burials.

In total, archaeologists have identified 13 sets of remains at the car park in Oxford Street in Leicester’s historic city centre.

Archaeological Project Officer John Thomas said: “We have discovered new evidence about a known cemetery that existed outside the walled town of Roman Leicester during the 3rd-4th Centuries AD. 

“The excavation, at the junction of Oxford Street and Newarke Street, lay approximately 130m outside the south gate of Roman Leicester, adjacent to one of the main routes into the town from the south (Oxford Street).  Roman law forbade burial within the town limits so cemeteries developed outside the walls, close to well-used roads.

“Previous excavations on Newarke Street had discovered numerous burials to the immediate east and north of the present site, all of which appeared to have been buried according to Christian traditions - buried in a supine position, facing east with little or no grave goods.

“Unusually the 13 burials found during the recent excavations, of mixed age and sex, displayed a variety of burial traditions including east to west & north  to south oriented graves, many with personal items such as finger rings, hairpins, buckles and hob-nailed shoes. 

“One in particular appears to have been buried in a Christian tradition, facing east and wearing a polished jet finger ring on their left hand which has a possible early Christian Iota - Chi monogram etched onto it, taking the initial letters from the Greek for Jesus Christ.  If so this would represent rare evidence for a personal statement of belief from this period. 

“In contrast a nearby and probably near contemporary grave appeared to indicate very different beliefs.  This grave had a north-south orientation, with the body laid on its side in a semi-foetal position, with the head removed and placed near the feet alongside two complete pottery jars that would have held offerings for the journey to the afterlife.  This would seem to be a very pagan burial, so it is possible from the variety of burials found that the cemetery catered for a range of beliefs that would have been important to people living in Leicester at this time.”

The excavations also add information to the increasingly well documented medieval southern suburb of the town, revealing remains of 12th-13th century quarries, cess-pits and rubbish pits that would have been dug in the backyards of properties fronting onto Oxford Street.

Mr Thomas added: “All of these pits contained a wealth of information from pottery, bone and environmental remains to help build a picture of medieval life in this part of the town.  A large 17th century defensive ditch running alongside Newarke Street was also discovered which was part of the town’s defences during the English Civil War.”

The site is currently earmarked for development.

The Search for Richard III was led by the University of Leicester, working with Leicester City Council, and in association with the Richard III Society.

via AlphaGalileo

link: University of Leicester 

Photonic Progress

NASA's Spitzer Telescope and the Hot Jupiter Class of Exoplanets

Space Infrared Telescope Facility

The Spitzer Space Telescope is the fourth and final element in the National Aeronautics and Space Administration's family of orbiting "Great Observatories," which includes the Hubble Space Telescope, the Compton Gamma-Ray Observatory and the Chandra X-Ray Observatory. This new infrared observatory is also an important scientific and technical bridge to NASA's Origins Program - an attempt to address such fundamental questions as "Where did we come from? Are we alone?"

Our galaxy is teeming with a wild variety of planets. In addition to our solar system's eight near-and-dear planets, there are more than 800 so-called exoplanets known to circle stars beyond our sun. One of the first "species" of exoplanets to be discovered is the hot Jupiters, also known as roasters. These are gas giants like Jupiters, but they orbit closely to their stars, blistering under the heat. 

Thanks to NASA's Spitzer Space Telescope, researchers are beginning to dissect this exotic class of planets, revealing raging winds and other aspects of their turbulent nature. A twist to come out of the recent research is the planets' wide range of climates. Some are covered with a haze, while others are clear. Their temperature profiles, chemistries and densities differ as well.

"The hot Jupiters are beasts to handle. They are not fitting neatly into our models and are more diverse than we thought," said Nikole Lewis of the Massachusetts Institute of Technology, Cambridge, lead author of a new Spitzer paper in the Astrophysical Journal examining one such hot Jupiter called HAT-P-2b. "We are just starting to put together the puzzle pieces of what's happening with these planets, and we still don't know what the final picture will be."

The very first exoplanet discovered around a sun-like star was, in fact, a hot Jupiter, called 51 Pegasi b. It was detected in 1995 by Swiss astronomers using the radial velocity technique, which measures the wobble of a star caused by the tug of a planet. Because hot Jupiters are heavy and whip around their stars quickly, they are the easiest to find using this strategy. Dozens of hot Jupiter discoveries soon followed. At first, researchers thought they might represent a more common configuration for other planetary systems in our galaxy beyond our own solar system. But new research, including that from NASA's Kepler space telescope, has shown that they are relatively rare.

In 2005, scientists were thrilled when Spitzer became the first telescope to detect light emitted by an exoplanet. Spitzer monitored the infrared light coming from a star and its planet -- a hot Jupiter -- as the planet disappeared behind the star in an event known as a secondary eclipse. Once again, this technique works best for hot Jupiters, because they are the biggest and hottest planets.

In addition to watching hot Jupiters slip behind their stars, researchers also use Spitzer to monitor the planets as they orbit all the way around a star. This allows them to create global climate maps, revealing how the planets' atmospheres vary from their hot, sun-facing sides to their cooler, night sides, due in part to fierce winds. (Hot Jupiters are frequently tidally locked, with one side always facing the star, just as our moon is locked to Earth.)

Since that first observation, Spitzer has probed the atmospheres of dozens of hot Jupiters, and some even smaller planets, uncovering clues about their composition and climate.

"When Spitzer launched in 2003, we had no idea it would prove to be a giant in the field of exoplanet science," said Michael Werner, the Spitzer project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Now, we're moving farther into the field of comparative planetary science, where we can look at these objects as a class, and not just as individuals."

In the new study, Lewis and colleagues made the longest Spitzer observation yet of a hot Jupiter. The infrared telescope stared at the HAT-P-2 system continuously for six days, watching it cross in front of its star, slip behind, and then reappear on the other side, making a full orbit. What makes the observation even more exciting to scientists is that the planet has a comet-like eccentric orbit, carrying it as close as 2.8 million miles (4.5 million kilometers) to the star and out to as far as 9.3 million miles (15 million kilometers). For reference, Mercury is about 28.5 million miles from our sun.

"It's as if nature has given us a perfect lab experiment with this system," said Heather Knutson, a co-author of the new paper at the California Institute of Technology, Pasadena, Calif. "Because the planet's distance to the sun changes, we can watch how fast it takes to heat up and cool down. It's as though we're turning the heat knob up on our planet and watching what happens." Knutson led the first team to create a global "weather" map of a hot Jupiter, called HD 189733 b, in 2007.

The new HAT-P-2b study is also one of the first to use multiple wavelengths of infrared light, instead of just one, while watching a full orbit of a hot Jupiter. This enables the scientists to peer down into different layers of the planet.

The results reveal that HAT-P-2b takes about a day to heat up as it approaches the hottest part of its orbit, and four to five days to cool down as it swings away. It also exhibits a temperature inversion -- a hotter, upper layer of gas -- when it is closest to its star. What's more, the carbon chemistry of the planet seems to be behaving in unexpected ways, which the astronomers are still trying to understand.

"These planets are much hotter and more dynamic than our own Jupiter, which is sluggish by comparison. Strong winds are churning material up from below, and the chemistry is always changing," said Lewis.

Another challenge in understanding hot Jupiters lies in parsing through the data. Lewis said her team's six-day Spitzer observation left them with 2 million data points to map out while carefully removing instrument noise.

"Theories are being shot down right and left," said Nick Cowan of Northwestern University, Evanston, Ill., a co-author of the HAT-P-2b study. "Right now, it's like the wild, wild west."

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit http://spitzer.caltech.edu and http://www.nasa.gov/spitzer .

NASA

Photonic Space

Deep Space: a great interactive web site from Olaf Frohn

I want to mention if you haven't seen it that Olaf Frohn has made a series of interactive charts detailing just about everything about earth's efforts in space exploration so far. This is an impressive collection well worth sharing or book-marking as a reference. Click here to enter the site. The chart below is a copy of one example from the site, but you need to visit to see the amount of detail.  In particular I like the exploration history chart. Great work!

Photonic Space

Kepler estimates 17 billion earth sized worlds in our galaxy

The results of a new analysis of Kepler data show that one in six stars has an Earth-sized planet in a tight orbit. About a fourth of all stars in the Milky Way have a super-Earth, and the same fraction have a mini-Neptune. Only about 3 percent of stars have a large Neptune, and only 5 percent a gas giant at the orbital distances studied. Credit: F. Fressin (CfA)
Click for full resolution
This artist's illustration represents the variety of planets being detected by NASA's Kepler spacecraft. A new analysis has determined the frequencies of planets of all sizes, from Earths up to gas giants. Key findings include the fact that one in six stars hosts an Earth-sized planet in an orbit of 85 days or less, and that almost all sun-like stars have a planetary system of some sort. (Hat tip to Robert Hurt for inspiring this illustration.) Credit: C. Pulliam & D. Aguilar (CfA)The latest Kepler information indicates there are 17 billion earth like planets in the milky way:  incidentally that is about ten times my own highly speculative estimate in February.

The quest to determine if planets like Earth are rare or common is taking another stride forward on the journey. Using NASA's Kepler spacecraft, managed by NASA Ames Research Center, astronomers are beginning to find Earth-sized planets orbiting distant stars. A new analysis of Kepler data shows that about 17 percent of stars have an Earth-sized planet in an orbit closer than Mercury. Since the Milky Way has about 100 billion stars, there are at least 17 billion Earth-sized worlds out there.

Francois Fressin, of the Harvard-Smithsonian Center for Astrophysics (CfA), presented the analysis today in a press conference at a meeting of the American Astronomical Society in Long Beach, Calif. A paper detailing the research has been accepted for publication in The Astrophysical Journal.

The research team found that 50 percent of all stars have a planet of Earth-size or larger in a close orbit. By adding larger planets detected in wider orbits up to the orbital distance of the Earth, this number increases to 70 percent.

Extrapolating from Kepler's currently ongoing observations and results from other detection techniques, scientists have determined that nearly all sun-like stars have planets.

Planets closer to their stars are easier to find because they transit more frequently. As more data are gathered, planets in larger orbits will be detected. In particular, Kepler's extended mission will enable the detection of Earth-sized planets at greater distances, including Earth-like orbits in the "habitable zone," the region in a planetary system where liquid water might exist on the surface of an orbiting planet.

Kepler is the first NASA mission capable of finding Earth-size planets orbiting in or near the habitable zone of the host star. NASA's Ames Research Center, Moffett Field, Calif., is the home organization of the science principal investigator, and is responsible for the ground system development, mission operations, and science data analysis.

NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development. Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with JPL at the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

The Space Telescope Science Institute in Baltimore archives, hosts and distributes the Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters.

To read more about the discovery, see the Harvard-Smithsonian Center for Astrophysics press release.

Read more about the Kepler Mission.

 

 

Michele Johnson
Ames Research Center, Moffett Field, Calif.
650-604-6982
michele.johnson@nasa.gov