Search for Life Beyond the Solar System

This week MagAO attended the conference, Search for Life Beyond the Solar System, locally in Tucson, Arizona. We’d like to thank the organizing committee, lead by Arizona Prof. Daniel Apai, for an interactive and interesting conference.

On Monday, Laird had lunch with most of his previous graduate students, almost all of whom attended the conference:


Most of Laird’s current and former students. Clockwise from 12:00: Laird Close, Beth Biller, Ya-Lin Wu, Andy Skemer, Eric Nielsen and friend, Jared Males, Kate Follette, Derek Kopon, and Nick Siegler.

The direct imaging talks were yesterday. This included Laird (H-alpha as a Probe of Very Low-mass Planets: The GAPplanetS Survey With the MagAO System) and Jared (Direct Imaging of Extrasolar Giant Planets in the Habitable Zone), as well as MagAO friends and colleagues Beth Biller(The Gemini/NICI Planet-Finding Campaign: The Frequency of Planets around Young Moving Group Stars), Jenny Patience, Andy Skemer (LEECH: LBTI Exozodi Exoplanet Common Hunt), Phil Hinz (The Challenge of the Exozodiacal Light(Tomorrow’s Resolution, Today) ), Denis Defrere (The Hunt for Observable Signatures of Terrestrial Planetary Systems), Olivier Guyon (Coronagraphy — From State of the Art to the Near Future), and more.

You can see the archived talks here, and you can read Tweets from the conference here.

VisAO takes the first optical image of an exoplanet from the ground

Today the MagAO team, along with our collaborators from the NICI team, published a paper on the extrasolar planet beta Pictoris b. We used our CCD camera VisAO to take a picture of the planet, the first time such a camera has been used to image an extrasolar planet from the ground.

You can read more about this achievement at UA News, the NASA Exoplanet Science Institute, and PlanetQuest.

Here is our announcement:

A Small Step Toward Discovering Habitable Earths

University of Arizona researchers snapped images of a planet outside our solar system with an Earth-based telescope using essentially the same type of imaging sensor found in digital cameras instead of an infrared detector. Although the technology still has a very long way to go, the accomplishment takes astronomers a small step closer to what will be needed to image earth-like planets around other stars

An artist’s impression of a young, giant exoplanet orbiting its host star. (Image: NASA/JPL-Caltech)

“This is an important next step in the search for exoplanets because imaging in visible light instead of infrared is what we likely have to do if we want to detect planets that might be suitable for harboring life,” said Jared Males, a NASA Sagan Fellow in the UA’s Department of Astronomy and Steward Observatory and lead author on a report to be published in The Astrophysical Journal.

Even though the image was taken at a wavelength that is just shy of being visible to the human eye, the use of a digital camera-type imaging sensor – called a charge-coupled device or CCD – opens up the possibility of imaging planets in visible light, which has not been possible previously with Earth-based telescopes.

“This is exciting to astronomers because it means we now are a small step closer to being able to image planets outside our solar system in visible light,” said Laird Close, a professor in the Department of Astronomy, who co-authored the paper.

He explained that all the other Earth-based images taken of exoplanets close to their stars are infrared images, which detect the planets’ heat. This limits the technology to Gas Giants – massive, hot planets young enough to still shed heat. In contrast, older, possibly habitable planets that have cooled since their formation don’t show up in infrared images as readily, and to image them, astronomers will have to rely on cameras capable of detecting visible light.

“Our ultimate goal is to be able to image what we call pale blue dots,” Close said. “After all, the Earth is blue. And that’s where you want to look for other planets: in reflected blue light.”

The photographed planet, called Beta Pictoris b, orbits its star at only nine times the Earth-Sun distance, making its orbit smaller than Saturn’s. In the team’s CCD images, Beta Pictoris b appears about 100,000 times fainter than its host star, making it the faintest object imaged so far at such high contrast and at such relative proximity to its star. The new images of this planet helped confirm that its atmosphere is at a temperature of roughly 2600 degrees Fahrenheit (1700 Kelvin). The team estimates that Beta Pictoris b weighs in at about 12 times the mass of Jupiter.

An image of the exoplanet Beta Pictoris b made with the Magellan Adaptive Optics (MagAO) VisAO camera. This image was made using a CCD camera, which is essentially the same technology as a cell phone camera. The planet is nearly 100,000 times fainter than its star, and orbits its star at roughly the same distance as Saturn from our Sun.

“Because the Beta Pictoris system is 63.4 light years from Earth, the scenario is equivalent to imaging a dime next right next to a lighthouse beam from more than four miles away,” Males said. “Our image has the highest contrast ever achieved on an exoplanet that is so close to its star.”

The contrast in brightness between the bright star and the faint planet is similar to the height of a 4-inch molehill next to Mount Everest, Close explained.

In addition to the host star’s overwhelming brightness, the astronomers had to overcome the turbulence in Earth’s atmosphere, which causes stars to twinkle and telescope images to blur. The success reported here is mostly due to an adaptive optics system developed by Close and his team that eliminates much of the atmosphere’s effect. The Magellan Adaptive Optics technology is very good at removing this turbulence, or blurring, by means of a deformable mirror changing shape 1,000 times each second in real time.

The Magellan Telescope with MagAO’s Adaptive Secondary Mirror (ASM) mounted at the top looking down (some 9 meters) onto the 6.5m (21 foot) diameter Primary Mirror (not visible, inside blue mirror cell). Moonlight image, credit: Yuri Beletsky, Las Campanas Observatory.

Adaptive optics have been used for more than 20 years at observatories in Arizona, most recently at the Large Binocular Telescope, and the latest version has now been deployed in the high desert of Chile at the Magellan 6.5-meter telescope.

The team also imaged the planet with both of MagAO’s cameras, giving the scientists two completely independent simultaneous images of the same object in infrared as well as bluer light to compare and contrast.

“An important part of the signal processing is proving that the tiny dot of light is really the planet and not a speckle of noise,” said Katie Morzinski, who is also a Sagan Fellow and member of the MagAO team. “I obtained the second image in the infrared spectrum – at which the hot planet shines brightly – to serve as an unequivocal control that we are indeed looking at the planet. Taking the two images simultaneously helps to prove the planet image on the CCD is real and not just noise.”

Males added: “In our case, we were able to record the planet’s own glow because it is still young and hot enough so that its signal stood out against the noise introduced by atmospheric blurring.”

“But when you go yet another 100,000 times fainter to spot much cooler and truly earthlike planets,” Males said, “we reach a situation in which the residual blurring from the atmosphere is too large and we may have to resort to a specialized space telescope instead.”

Development of the MagAO system was made possible through the strong support of the National Science Foundation MRI, TSIP and ATI grant programs. The Magellan telescopes are operated by a partnership of the Carnegie institute, the University of Arizona, Harvard University, Massachusetts Institute of Technology and the University of Michigan. The work of NASA Sagan Fellows Jared Males and Katie Morzinski was performed in part under contract with the California Institute of Technology funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute.

Magellan Adaptive Optics first-light observations of the exoplanet β Pic b. I. Direct imaging in the far-red optical with MagAO+VisAO and in the near-IR with NICI

There are a number of factors that have pushed extrasolar planet imagers to work in the infrared. The first is that young planets are very hot, so they are brighter in the infrared. In fact, they become very faint at shorter “optical” wavelengths. The second factor is that adaptive optics (AO), the technology we use to image exoplanets, has normally worked better in the infrared. You could say that the stars twinkle less there. But to know as much as we can about exoplanets and their atmospheres, we want to image them at as many wavelengths as we can. So we used MagAO’s VisAO camera to image the extrasolar planet beta Pictoris b with our CCD. This is the first time that has been done from the ground, and shows that we are pushing the capabilities of AO to ever shorter (and more difficult) wavelengths.

An image of the exoplanet Beta Pictoris b made with the Magellan Adaptive Optics (MagAO) VisAO camera. This image was made using a CCD camera, which is essentially the same technology as a cell phone camera. The planet is nearly 100,000 times fainter than its star, and orbits its star at roughly the same distance as Saturn from our Sun.

Abstract: We present the first ground-based CCD (λ<1μm) image of an extrasolar planet. Using MagAO's VisAO camera we detected the extrasolar giant planet (EGP) β Pictoris b in Y-short (YS, 0.985 μm), at a separation of 0.470±0.010′′ and a contrast of (1.63±0.49)×10−5. This detection has a signal-to-noise ratio of 4.1, with an empirically estimated upper-limit on false alarm probability of 1.0%. We also present new photometry from the NICI instrument on the Gemini-South telescope, in CH4S,1% (1.58 μm), KS (2.18μm), and Kcont (2.27 μm). A thorough analysis of our photometry combined with previous measurements yields an estimated near-IR spectral type of L2.5±1.5, consistent with previous estimates. We estimate log(Lbol/LSun) = −3.86±0.04, which is consistent with prior estimates for β Pic b and with field early-L brown dwarfs. This yields a hot-start mass estimate of 11.9±0.7 MJup for an age of 21±4 Myr, with an upper limit below the deuterium burning mass. Our Lbol based hot-start estimate for temperature is Teff=1643±32 K (not including model dependent uncertainty). Due to the large corresponding model-derived radius of R=1.43±0.02 RJup, this Teff is ∼250 K cooler than would be expected for a field L2.5 brown dwarf. Other young, low-gravity (large radius), ultracool dwarfs and directly-imaged EGPs also have lower effective temperatures than are implied by their spectral types. However, such objects tend to be anomalously red in the near-IR compared to field brown dwarfs. In contrast, β Pic b has near-IR colors more typical of an early-L dwarf despite its lower inferred temperature. For more on our result see: Males, J. R., et al. "Magellan Adaptive Optics first-light observations of the exoplanet β Pic b. I. Direct imaging in the far-red optical with MagAO+VisAO and in the near-IR with NICI" ApJ, 786, 32, 2014      ADS    arxiv preprint