Discovery image of HD 106906 b in the thermal infrared (4µm wavelength) from MagAO/Clio2, processed to remove the bright light from its host star, HD 106906 A. The planet is more than 20 times farther away from HD 106906 A than Neptune is from our Sun.
We report the discovery of a planetary-mass companion, HD 106906 b, with the new Magellan Adaptive Optics (MagAO) + Clio2 system. The companion is detected with Clio2 in three bands: J, KS, and L′, and lies at a projected separation of 7.1” (650 AU). It is confirmed to be comoving with its 13±2 Myr-old F5 host using Hubble Space Telescope/Advanced Camera for Surveys astrometry over a time baseline of 8.3 yr. DUSTY and COND evolutionary models predict the companion’s luminosity corresponds to a mass of 11±2MJup, making it one of the most widely separated planetary-mass companions known. We classify its Magellan/Folded-Port InfraRed Echellette J/H/K spectrum as L2.5±1; the triangular H-band morphology suggests an intermediate surface gravity. HD 106906 A, a pre-main-sequence Lower Centaurus Crux member, was initially targeted because it hosts a massive debris disk detected via infrared excess emission in unresolved Spitzer imaging and spectroscopy. The disk emission is best fit by a single component at 95 K, corresponding to an inner edge of 15-20 AU and an outer edge of up to 120 AU. If the companion is on an eccentric (e>0.65) orbit, it could be interacting with the outer edge of the disk. Close-in, planet-like formation followed by scattering to the current location would likely disrupt the disk and is disfavored. Furthermore, we find no additional companions, though we could detect similar-mass objects at projected separations >35 AU. In situ formation in a binary-star-like process is more probable, although the companion-to-primary mass ratio, at <1%, is unusually small.
For more on HD 106906 b see:
Bailey, V., et al. "HD 106906 b: A planetary-mass companion outside a massive debris disk".
ApJL, 780, L4, 2013ADSpreprint [pdf]arxiv preprint
Today the MagAO team is extremely happy to announce our first three refereed publications. Read on to find out about the exciting science we did in the Orion nebula.
The following press release can be downloaded as a pdf.
For a little more insight into the project see this Arizona Daily Star article. For Carnegie’s take go here. For the Italian version, check out INAF’s news. Nice work Simone.
Scientists Make Highest Resolution Photos Ever of the Night Sky
Astronomers at the University of Arizona, Arcetri Observatory in Italy, and at the Carnegie Observatory have developed a new type of camera that allows higher resolution (sharper) images to be taken than ever before. The team has been developing this technology for over 20 years at observatories in Arizona (most recently at the Large Binocular Telescope; LBT), and has now deployed the latest version of these cameras in the high desert of Chile at the Magellan 6.5m (21ft) telescope. “It was very exciting to see this new camera make the night sky look sharper than has ever before been possible” said University of Arizona professor Laird Close, the project’s principal scientist, “We can, for the first time, make deep images that resolve objects just 0.02 arcseconds across. That is a very small angle on the sky. It is like the width of a dime (1.7 cm) seen over 100 miles (160 km) away. It could also be compared to resolving a baseball diamond on the Moon”.
Removing the “twinkle” From the Stars in Visible Light
The reason for the factor of 2 improvement over past efforts is that, for the first time, a large 6.5m telescope is being used for digital photography at its theoretical resolution limit in wavelengths of visible light. “As you move from infrared to visible light, your image sharpness improves”, said Dr. Jared Males, a NASA Sagan Fellow at the University of Arizona , “Up until now, large telescopes could make the theoretically sharpest photos only in infrared (long wavelength) light, but our new camera can work in the visible and make photos twice as sharp”. These images are also at least twice as sharp as what the Hubble Space Telescope (HST) can make because the 6.5m Magellan telescope is much larger than the 2.4m HST. HST has always produced the best available visible light images, since until now even large ground-based telescope with complex adaptive optics imaging cameras could only make blurry images in light that the eye can see (visible light). To obtain the excellent correction of atmospheric turbulence required for “visible light AO”, the team developed a very powerful adaptive optics system that floats a thin (1/16 inch (1.6 mm) thick) curved glass mirror (2.7 feet (85 cm) across) on a magnetic field 30 feet (9.2m) above the large 21 foot (6.5m) primary mirror of the telescope (see figure 1). This so-called “Adaptive Secondary Mirror” (ASM) can change its shape at 585 points on its surface 1000 times a second. In this manner the “blurring” effects of the atmosphere can be removed, and thanks to the high density of actuators on the mirror, astronomers can see the visible sky more clearly than ever before, almost like having a 6.5m telescope in space.
Figure 1: 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.
New Science Results From MagAO: Insights into How Stars and Planets Form
The new adaptive optics system, called MagAO, has already made some important scientific discoveries. As the system was being tested (so called “First Light”) the team tried to resolve the famous star that gives the Great Orion Nebulae (M42) most of its UV light. This young (~1 million year old) star is called Theta 1 Ori C and it was previously known to be two stars (a binary star pair; called C1 and C2). However, the separation is so small that this famous pair has never been resolved into 2 stars in a direct telescope photo. Once MagAO and its visible science camera (VisAO; see figure 2) were pointed towards Theta Ori 1 C, the results were exciting and immediate (see figure 3). “I have been imaging Theta 1 Ori C for over 20 years and never could I directly see that it was in fact 2 stars”, said Dr. Close, “But as soon as we turned on the MagAO system it was beautifully split into 2 stars just 0.032 arcseconds apart”. MagAO was then used to map out all the positions of the brightest nearby Orion Trapezium cluster stars and was able to detect very small motions compared to older LBT data, a result of the stars slowly revolving around each other. Indeed, a small group of stars called Theta 1 Ori B1-B4 was proved to be likely a bound “mini-cluster” of stars that will likely eject the lowest mass star in the near future (see figure 4). This result has just been published in the Astrophysical Journal (preprint).
Figure 2: The VisAO camera and MagAO wavefront sensors at the focus of the 6.5m Magellan telescope (all optics inside dark ring) that were used to make the visible wavelength images. Dr. Jared Males (VisAO instrument scientist/NASA Sagan Fellow) and Professor Laird Close (MagAO project scientist) are shown for scale from left to right. Photo credit Dr. Katie Morzinski, NASA Sagan Fellow at the University of Arizona.Figure 3: The power of visible light adaptive optics. Here we show (on the left) a “normal” photo of the theta 1 Ori C binary star in red light (in the r’ filter, 630 nm). It just looks an unresolved star. Then the middle image shows how if we remove (in real time) the blurring of the atmosphere with MagAO’s adaptive optics’ the resulting photo becomes ~17 times sharper (corrected resolutions range from 0.019-0.029 arcseconds on theta 1 Ori C). Both photos are 60 seconds long, and no post-detection image enhancement has been applied. These are the highest resolution photos taken by a telescope. Photo credit Laird Close, University of Arizona.
A mystery about how planets form is: how are the disks of dust and gas affected by the strong ionizing light/wind coming from a massive star like Theta 1 Ori C (some 44 times the mass of the Sun)? The team used MagAO and VisAO to look for red light (at 656 nm, or hydrogen alpha) from ionized hydrogen gas to trace out how the strong UV flux and stellar wind from Theta 1 Ori C affects the disks around its neighboring stars. MagAO’s photo shows that the envelope of gas and dust around a pair of stars (called LV1) just 6.5 arcseconds away from Theta 1 Ori C are heavily distorted into “teardrop” shapes as the strong UV light and wind create shock fronts and drag gas downwind of the pair (see bottom insert in figure 4). “We were surprised to find that the mass of the pair of young stars was very low, making this a very rare example of a low mass pair of young disks (called proplyds).” Said Arizona graduate student Ya-Lin Wu (who led the Astrophysical Journal paper on this result (preprint).
Figure 4: The Orion Trapezium is a cluster of young stars still in the process of forming. The top inset image shows MagAO’s photo of the “mini-cluster” of young stars in the Theta 1 Ori B group (B1-B4; Top Inset image). There is now clear evidence of relative motion of these stars around B1. The lowest mass member (B4) will likely be ejected in the future. The middle inset photo shows the highest resolution astronomical photo of the Theta 1 Ori C1 C2 pair, and the bottom insert shows the LV 1 binary young star pair shaped by the wind from Theta 1 Ori C (in the visible light of hydrogen gas (at 656 nm). Photo Credit: Laird Close and Ya-Lin Wu, University of Arizona. The Background image is a previous HST Orion Trapezium Cluster visible image (NASA, C.R. O’Dell and S.K. Wong, Rice University).
The distribution of gas and dust in young planetary systems is another unsolved problem in planet formation. The team used VisAO’s simultaneous/spectral differential Imager (SDI) to image in and out of the bright 656 nm hydrogen alpha emission line. This allowed the team to trace the absorption (hence mass) of one of the rare “silhouette” disks in Orion. The disk lies in front of the bright Orion nebula, so we see the dark shadow cast as the dust in the disk absorbs background light from the nebula (see figure 5). The more material lies in the foreground disk, the greater the degree of absorption of background light from the nebula. The SDI camera allowed the light from the star to be removed at a very high level—leaving, for the first time, a clear look at the inner regions of the silhouette. “We were surprised to find that the amount of attenuated light from the nebula increased gradually, rather than sharply, toward the star”, noted Arizona graduate student (and lead author of the Astrophysical Journal letter – preprint) Kate Follette. “It seems as though the outer parts of this large disk have less dust than we would have expected”. As can been seen from Figure 5, there is clear evidence that MagAO with its SDI camera can make visible images of even very faint stars such as Orion 218-354.
Figure 5: A MagAO image of Orion 218-354 silhouette after removal of light from the central star. The left-hand image shows the silhouette (shadow) of the disk against the bright background hydrogen alpha emission of the Orion nebula. The right-hand image is the same, but with contours denoting levels of increasing attenuation of the background nebular light toward the central star. The percentages denote the amount of nebular light passing through the disk. The degree of attenuation probes the amount of dust in the disk at each location. Photo credit Kate Follette, University of Arizona.
These results are just highlights of the first three science papers from the MagAO system. More exciting results will soon follow. Development of the MagAO system could not have been possible without the strong support of the National Science Foundation MRI, TSIP and ATI grant programs. The ASM itself was produced by Microgate and ADS of Italy, with the University of Arizona, Steward Observatory Mirror Lab. The MagAO pyramid wavefront sensor was developed at the Arcetri Observatory, Italy. The success of the system could not have been possible without the great support of the Magellan Telescope staff that helped us use their powerful telescope. The Magellan telescopes are run by a partnership of the Carnegie institute, University of Arizona, Harvard University, MIT, 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 (Caltech) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. The work of Kate Follette was funded in part by the NSF Graduate Research Fellowship program.
For more information about the Magellan Adaptive Optics System (MagAO) see /
We utilized the new high-order (250-378 mode) Magellan Adaptive Optics system
(MagAO) to obtain very high spatial resolution observations in “visible light”
with MagAO’s VisAO CCD camera. In the good-median seeing conditions of Magellan
(0.5-0.7″) we find MagAO delivers individual short exposure images as good as
19 mas optical resolution. Due to telescope vibrations, long exposure (60s) r’
(0.63 micron) images are slightly coarser at FWHM=23-29 mas (Strehl ~28%) with
bright (R<9 mag) guide stars. These are the highest resolution filled-aperture
images published to date. Images of the young (~1 Myr) Orion Trapezium Theta 1
Ori A, B, and C cluster members were obtained with VisAO. In particular, the 32
mas binary Theta 1 Ori C1/C2 was easily resolved in non-interferometric images
for the first time. Relative positions of the bright trapezium binary stars
were measured with ~0.6-5 mas accuracy. We now are sensitive to relative proper
motions of just ~0.2 mas/yr (~0.4 km/s at 414 pc) - this is a ~2-10x
improvement in orbital velocity accuracy compared to previous efforts. For the
first time, we see clear motion of the barycenter of Theta 1 Ori B2/B3 about
Theta 1 Ori B1. All five members of the Theta 1 Ori B system appear likely a
gravitationally bound "mini-cluster", but we find that not all the orbits can
be both circular and co-planar. The lowest mass member of the Theta 1 Ori B
system (B4; mass ~0.2 Msun) has a very clearly detected motion (at 4.1+/-1.3
km/s; correlation=99.9%) w.r.t B1 and will likely be ejected in the future.
This "ejection" process of the lowest mass member of a "mini-cluster" could
play a major role in the formation of low mass stars and brown dwarfs
[caption id="attachment_4889" align="aligncenter" width="1585"] The power of visible light adaptive optics. Here we show (on the left) a “normal” photo of the theta 1 Ori C binary star in red light (in the r’ filter, 630 nm). It just looks an unresolved star. Then the middle image shows how if we remove (in real time) the blurring of the atmosphere with MagAO’s adaptive optics’ the resulting photo becomes ~17 times sharper (corrected resolutions range from 0.019-0.029 arcseconds on theta 1 Ori C). Both photos are 60 seconds long, and no post-detection image enhancement has been applied. These are the highest resolution photos taken by a telescope. Photo credit Laird Close, University of Arizona. [/caption]
For more on high resolution filled-aperture imaging of Trapezium see:
Close, L. M., et al. “Diffraction-limited Visible Light Images of Orion Trapezium Cluster With the Magellan Adaptive Secondary AO System (MagAO)”. ApJ, 774, 94, 2013preprint [pdf]arxiv preprint
Disks of gas and dust around newly born stars, dubbed protoplanetary disks (proplyds), are believed to evolve into planetary systems. Understanding how these disks are affected by strong light/wind from nearby massive stars is crucial to theories of planet formation and evolution. We used MagAO to image the binary proplyd (called LV 1) in the Orion Nebula (M42) at the 653nm hydrogen emission line (H alpha) during the first commissioning run. The spatial resolution is comparable to that of the Hubble Space Telescope (HST), demonstrating the power of AO in visible wavelengths. Our H alpha image clearly shows that the gas of the binary is heavily distorted into “teardrop” shape due to strong UV light and wind from a nearby star, Theta 1 Ori C (See image below). The lack of orbital motion over ~18 years between the stars further suggests that they are of low masses, plausibly a double brown dwarf (the so-called “failed star” since it is not massive enough to initiate hydrogen fusion). This makes LV 1 a rare example of a low mass pair of young disks. Finally, we show that the macroscopic features of these disks may help infer the embedded magnetic field intensity and profile.
The binary proplyd “LV-1” in the Orion Trapezium cluster, imaged with MagAO’s VisAO camera.
For more on LV 1 see:
Wu, Y. L., et al. “High Resolution H alpha Images of the Binary Low-mass Proplyd LV 1 with the Magellan AO System”. ApJ, 775, 45, 2013preprint [pdf]arxiv preprint
Abstract: We utilize the new Magellan adaptive optics system (MagAO) to image the binary proplyd LV 1 in the Orion Trapezium at H alpha. This is among the first AO results in visible wavelengths. The H alpha image clearly shows the ionization fronts, the interproplyd shell, and the cometary tails. Our astrometric measurements find no significant relative motion between components over ~18 yr, implying that LV 1 is a low-mass system. We also analyze Large Binocular Telescope AO observations, and find a point source which may be the embedded protostar’s photosphere in the continuum. Converting the H magnitudes to mass, we show that the LV 1 binary may consist of one very-low-mass star with a likely brown dwarf secondary, or even plausibly a double brown dwarf. Finally, the magnetopause of the minor proplyd is estimated to have a radius of 110 AU, consistent with the location of the bow shock seen in H alpha.
The flat pancake-like disks of gas and dust that surround young stars (so-called “circumstellar disks”) are of interest to astronomers because we believe that planets are made from their material. In the 1990s, the Hubble Space Telescope completed groundbreaking observations of the Great Orion Nebula at a red wavelength of light termed “Hydrogen-alpha” (the brightest light emitted by glowing hydrogen gas), revealing a number of circumstellar disks seen in silhouette against the bright background nebula. At the time, these observations provided the most conclusive direct evidence of the existence of circumstellar disks around young stars, and providing some of the first measurements of their size and geometry.
These “silhouette disks” occur because the stars that host them lie between Earth and the glowing hydrogen gas of the nebula. The light from the nebula passes through the disk on its way to Earth and some of it is absorbed by the material in the disk so that less total light reaches us from the regions of the nebula that lie behind it. In other words, the disk casts a shadow that we see as a dark patch amid the glowing gas of the nebula.
The amount of light blocked varies depending on how much material lies in the disk. More specifically, the densest regions of the disk will absorb most or even all of the background light, while thinner regions will absorb less. Imagine a butterfly flying in front of a spotlight. While its body will block enough light to make it opaque, it’s wings will be partially translucent – blocking some, but not all, of the background light. The thicker the wings, the more light they will block. Analogously, the amount of nebular light passing through each point in a silhouette disk is a direct measurement of the thickness (amount of material) in the disk at that point.
Until now, these disks have not been observed in silhouette from the ground. Although the theoretical resolution limit of a large ground-based telescope is higher than that of the small Hubble Space Telescope, the earth’s atmosphere makes it difficult to make images at the theoretical resolution limit of the telescope. This conundrum was the impetus for the development of adaptive optics (AO) technology, which corrects for the blurring effect of the atmosphere.
However, most modern AO systems operate at infrared wavelengths because the Earth’s atmosphere is a little better behaved (more “coherent”) there. It is only with the advent of next generation AO systems like Magellan AO that we are able to correct atmospheric turbulence at the level needed to achieve AO correction in visible light. Since nebulae like Orion emit most of their light in the visible, it wasn’t possible to image these disks in silhouette from the ground until now.
The MagAO system gives us several advantages over HST, the primary being that we are able to take images where the starlight is concentrated in just a small number of pixels (the star is “unsaturated”, so to speak). This allows us to probe the silhouette disks much farther inward than was possible with HST.
We observed the silhouette disk called Orion 218-354 during our December 2012 commissioning run. We were able to probe the amount of light blocked by the large disk all the way from its outer regions at a radius of ~500AU inward to just ~20AU (about the orbit of Uranus in our solar system). Surprisingly, we found that the amount of background light from the nebula that made it through the disk decreased slowly towards the star, and never reached an opaque point. This was unexpected because previous observations of the disk suggested that there was probably more material in the disk, and that it should reach an opaque point very quickly.
There are several possible explanations for why there is so little material in this disk, but one of the more interesting and plausible explanations is that the small dust grains that block Hydrogen-alpha emission from the nebula most effectively have been depleted. Although we believe disks are born with mostly small grains, as they age these grains may collide and coagulate, forming larger and larger grains and eventually pebbles, boulders and planets. The small amount of material that we found in this disk may indicate that this process (called “grain growth”) is well underway in the Orion 218-354 disk. A MagAO image of Orion 218-354 silhouette after removal of light from the central star. The left-hand image shows the silhouette (shadow) of the disk against the bright background hydrogen alpha emission of the Orion nebula. The right-hand image is the same, but with contours denoting levels of increasing attenuation of the background nebular light toward the central star. The percentages denote the amount of nebular light passing through the disk. The degree of attenuation probes the amount of dust in the disk at each location. Photo credit Kate Follette, University of Arizona.
For more on Orion 218-354 see:
Follette, K. B., et al. “The First Circumstellar Disk Imaged in Silhouette at Visible Wavelengths with Adaptive Optics : MagAO Imaging of Orion 218-534”. ApJ, 775, L13, 2013preprint [pdf]arxiv preprint
Abstract: We present high resolution adaptive optics (AO) corrected images of the silhouette disk Orion 218-354 taken with Magellan AO (MagAO) and its visible light camera, VisAO, in simultaneous differential imaging (SDI) mode at H-alpha. This is the first image of a circumstellar disk seen in silhouette with adaptive optics and is among the first visible light adaptive optics results in the literature. We derive the disk extent, geometry, intensity and extinction profiles and find, in contrast with previous work, that the disk is likely optically-thin at H-alpha. Our data provide an estimate of the column density in primitive, ISM-like grains as a function of radius in the disk. We estimate that only ~10% of the total sub-mm derived disk mass lies in primitive, unprocessed grains. We use our data, Monte Carlo radiative transfer modeling and previous results from the literature to make the first self-consistent multiwavelength model of Orion 218-354. We find that we are able to reproduce the 1-1000micron SED with a ~2-540AU disk of the size, geometry, small vs. large grain proportion and radial mass profile indicated by our data. This inner radius is a factor of ~15 larger than the sublimation radius of the disk, suggesting that it is likely cleared in the very interior.
