Direct Imaging in the Habitable Zone and the Problem of Orbital Motion

Males, Jared R.; Skemer, Andrew J.; Close, Laird M.

doi:10.1088/0004-637x/771/1/10

Cited by 32 publications

(15 citation statements)

References 42 publications

(33 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An additional night of data was taken on 2019 June 27. Enough time separates the collection of these data from the initial observations such that orbital motion complicates combining these with the rest of the data 33 , 34 . However, this extra night provides a useful astrometric check for brighter planet candidates.…”

Section: Resultsmentioning

confidence: 99%

Imaging low-mass planets within the habitable zone of α Centauri

et al. 2021

View full text Add to dashboard Cite

Giant exoplanets on wide orbits have been directly imaged around young stars. If the thermal background in the mid-infrared can be mitigated, then exoplanets with lower masses can also be imaged. Here we present a ground-based mid-infrared observing approach that enables imaging low-mass temperate exoplanets around nearby stars, and in particular within the closest stellar system, α Centauri. Based on 75–80% of the best quality images from 100 h of cumulative observations, we demonstrate sensitivity to warm sub-Neptune-sized planets throughout much of the habitable zone of α Centauri A. This is an order of magnitude more sensitive than state-of-the-art exoplanet imaging mass detection limits. We also discuss a possible exoplanet or exozodiacal disk detection around α Centauri A. However, an instrumental artifact of unknown origin cannot be ruled out. These results demonstrate the feasibility of imaging rocky habitable-zone exoplanets with current and upcoming telescopes.

show abstract

Section: Resultsmentioning

confidence: 99%

Imaging low-mass planets within the habitable zone of α Centauri

et al. 2021

View full text Add to dashboard Cite

show abstract

“…This effectively reduces the number of independant orbits that should be taken into account in Equation 3. We did not try to thouroughly test this hypothesis, but interestingly enough, this idea, based only on the empirical results of our K-Stacker runs and on our experience using it, agrees with the conclusion reached by Males et al (2013), using a more sophisticated theoretical reasoning.…”

Section: The Problem Of False Positivessupporting

confidence: 55%

“…At first glance, in the case of K-Stacker, the situation seems much more problematic since each of the 10 8 orbits tried by the algorithm can potentially lead to a false detection. This particular problem was already pointed out by Males et al (2013). A first estimate of the false positive probability can be done assuming that the S/N value of each orbit tried by K-Stacker is independant of all the other values.…”

Section: The Problem Of False Positivesmentioning

confidence: 99%

“…This is especially true when using large telescope, probing the innermost part of close-by stellar system. In such a case, even data acquired during succeeding nights can be affected by the orbital motion of the planet (see Males et al, 2013 for a detailed disccussion of this particular problem) Males et al (2015) also worked on the problem of recombining images acquired on longer timescale, in which the planet was moving on a significant part of its orbit. However, they use the assumption that the planet, albeit very faint, could be seen in each individual frame.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

K-Stacker: Keplerian image recombination for the direct detection of exoplanets

Nowak

Coroller

Arnold

et al. 2018

A&A

View full text Add to dashboard Cite

Context. Angular Differential Imaging (ADI) takes advantage of the field rotation naturally induced by altitude-azimuth mounts to reduce static speckle noise. Used with facilities like SPHERE at the VLT, this technique allows to achieve contrast ratios of 10 −6 . But the ADI method intrinsically limits the useful exposure time on a given target (to about 1-2 h per night). Detecting fainter exoplanets requires to be able to combine multiple observations acquired on different nights, potentially spread on several weeks or months. But the unknown orbital motion of the planet makes it particularly diffcult to properly combine all observations. In the near future, with the upcoming generation of Extremely Large Telescopes (ELTs) with increased resolution, the orbital motion may even become a problem on a single night. Aims. We present a proof of concept for a new algorithm which can be used to detect exoplanets in high contrast images. The algorithm properly combines mutliple observations acquired during different nights, taking into account the orbital motion of the planet. Methods. We simulate SPHERE/IRDIS time series of observations in which we blindly inject planets on random orbits, at random level of S/N, below the detection limit (down to S/N 1.5). We then use an optimization algorithm to "guess" the orbital parameters, and take into account the orbital motion to properly recombine the different images, and eventually detect the planets. Results. We show that an optimization algorithm can indeed be used to find undetected planets in temporal sequences of images, even if they are spread over orbital time scales. As expected, the typical gain in S/N ratio is √ n, n being the number of observations combined. We find that the K-Stacker algorithm is able de-orbit and combine the images to reach a level of performance similar to what could be expected if the planet was not moving. We find recovery rates of 50% at S/N=5. We also find that the algorithm is able to determine the position of the planet in individual frames at one pixel precision, even despite the fact that the planet itself is below the detection limit in each frame. Conclusions. Our simulations show that K-Stacker can be used to detect planets at very low S/N level, down to 2 in individual frames, for series of 10 images. This could be used to increase the contrast limit of current exoplanet imaging instruments and to discover fainter bodies. We also suggest that the ability of K-Stacker to determine the position of the planet in every image of the time serie could be used as part of a new observing strategy in which long exposures would be broken into shorter ones spread over months. This could make possible to determine the orbital parameters of a planet without requiring multiple high S/N >5 detections.

show abstract

“…These ELTs will be used to search for planets at very small separations (below 10 au) with first-light instruments (Chauvin 2018a). In this case, the Keplerian motion could become non-negligeable in a matter of only a few days (Males et al 2013).…”

Section: Introductionmentioning

confidence: 99%

K-Stacker: an algorithm to hack the orbital parameters of planets hidden in high-contrast imaging

Coroller

Nowak

Delorme

et al. 2020

A&A

View full text Add to dashboard Cite

Context. Recent high-contrast imaging surveys, using the Spectro-Polarimetic High contrast imager for Exoplanets REsearch (SPHERE) or the Gemini Planet Imager in search of planets in young, nearby systems, have shown evidence of a small number of giant planets at relatively large separation beyond 10–30 au, where those surveys are the most sensitive. Access to smaller physical separations between 5 and 30 au is the next step for future planet imagers on 10 m telescopes and the next generation of extremely large telescopes in order to bridge the gap with indirect techniques such as radial velocity, transit, and soon astrometry with Gaia. In addition to new technologies and instruments, the development of innovative observing strategies combined with optimized data processing tools is participating in the improvement of detection capabilities at very close angular separation. In that context, we recently proposed a new algorithm, Keplerian-Stacker, which combines multiple observations acquired at different epochs and takes into account the orbital motion of a potential planet present in the images to boost the ultimate detection limit. We showed that this algorithm is able to find planets in time series of simulated images of the SPHERE InfraRed Dual-band Imager and Spectrograph (IRDIS) even when a planet remains undetected at one epoch. Aims. Our goal is to test and validate the K-Stacker algorithm performances on real SPHERE datasets to demonstrate the resilience of this algorithm to instrumental speckles and the gain offered in terms of true detection. This will motivate future dedicated multi-epoch observation campaigns of well-chosen, young, nearby systems and very nearby stars carefully selected to search for planets in emitted and reflected light, respectively, to open a new path concerning the observing strategy used with current and future planet imagers. Methods. To test K-Stacker, we injected fake planets and scanned the low signal-to-noise ratio (S/N) regime in a series of raw observations obtained by the SPHERE/IRDIS instrument in the course of the SPHERE High-contrast ImagiNg survey for Exoplanets. We also considered the cases of two specific targets intensively monitored during this campaign: β Pictoris and HD 95086. For each target and epoch, the data were reduced using standard angular differential imaging processing techniques and then recombined with K-Stacker to recover the fake planetary signals. In addition, the known exoplanets β Pictoris b and HD 95086 b previously identified at lower S/N in single epochs have also been recovered by K-Stacker. Results. We show that K-Stacker achieves a high success rate of ≈100% when the S/N of the planet in the stacked image reaches ≈9. The improvement of the S/N is given as the square root of the total exposure time contained in the data being combined. At S∕N < 6−7, the number of false positives is high near the coronagraphic mask, but a chromatic study or astrophysical criteria can help to disentangle between a bright speckle and a true detection. During the blind test and the redetection of HD 95086 b, and β Pic b, we highlightthe ability of K-Stacker to find orbital solutions consistent with those derived by the current Markov chain Monte Carlo orbital fitting techniques. This confirms that in addition to the detection gain, K-Stacker offers the opportunity to characterize the most probable orbital solutions of the exoplanets recovered at low S/N.

show abstract

Direct Imaging in the Habitable Zone and the Problem of Orbital Motion

Cited by 32 publications

References 42 publications

Imaging low-mass planets within the habitable zone of α Centauri

Imaging low-mass planets within the habitable zone of α Centauri

K-Stacker: Keplerian image recombination for the direct detection of exoplanets

K-Stacker: an algorithm to hack the orbital parameters of planets hidden in high-contrast imaging

Contact Info

Product

Resources

About