The Experts below are selected from a list of 15192 Experts worldwide ranked by ideXlab platform
Michael E. Brown - One of the best experts on this subject based on the ideXlab platform.
-
A Deep Search for Additional Satellites around the Dwarf Planet Haumea
The Astronomical Journal, 2016Co-Authors: Luke Burkhart, Darin Ragozzine, Michael E. BrownAbstract:Haumea is a Dwarf Planet with two known satellites, an unusually high spin rate, and a large collisional family, making it one of the most interesting objects in the outer solar system. A fully self-consistent formation scenario responsible for the satellite and family formation is still elusive, but some processes predict the initial formation of many small moons, similar to the small moons recently discovered around Pluto. Deep searches for regular satellites around Kuiper belt objects are difficult due to observational limitations, but Haumea is one of the few for which sufficient data exist. We analyze Hubble Space Telescope (HST) observations, focusing on a 10-consecutive-orbit sequence obtained in 2010 July, to search for new very small satellites. To maximize the search depth, we implement and validate a nonlinear shift-and-stack method. No additional satellites of Haumea are found, but by implanting and recovering artificial sources, we characterize our sensitivity. At distances between ~10,000 and ~350,000 km from Haumea, satellites with radii as small as ~10 km are ruled out, assuming an albedo (p ≃ 0.7) similar to Haumea. We also rule out satellites larger than ≳40 km in most of the Hill sphere using other HST data. This search method rules out objects similar in size to the small moons of Pluto. By developing clear criteria for determining the number of nonlinear rates to use, we find that far fewer shift rates are required (~35) than might be expected. The nonlinear shift-and-stack method to discover satellites (and other moving transients) is tractable, particularly in the regime where nonlinear motion begins to manifest itself.
-
a deep search for additional satellites around the Dwarf Planet haumea
arXiv: Earth and Planetary Astrophysics, 2016Co-Authors: Luke Burkhart, Darin Ragozzine, Michael E. BrownAbstract:Haumea is a Dwarf Planet with two known satellites, an unusually high spin rate, and a large collisional family, making it one of the most interesting objects in the outer solar system. A fully self-consistent formation scenario responsible for the satellite and family formation is still elusive, but some processes predict the initial formation of many small moons, similar to the small moons recently discovered around Pluto. Deep searches for regular satellites around KBOs are difficult due to observational limitations, but Haumea is one of the few for which sufficient data exist. We analyze Hubble Space Telescope (HST) observations, focusing on a ten-consecutive-orbit sequence obtained in July 2010, to search for new very small satellites. To maximize the search depth, we implement and validate a non-linear shift-and-stack method. No additional satellites of Haumea are found, but by implanting and recovering artificial sources, we characterize our sensitivity. At distances between $\sim$10,000 km and $\sim$350,000 km from Haumea, satellites with radii as small as $\sim$10 km are ruled out, assuming an albedo ($p \simeq 0.7$) similar to Haumea. We also rule out satellites larger than $\gtrsim$40 km in most of the Hill sphere using other HST data. This search method rules out objects similar in size to the small moons of Pluto. By developing clear criteria for determining the number of non-linear rates to use, we find that far fewer shift rates are required ($\sim$35) than might be expected. The non-linear shift-and-stack method to discover satellites (and other moving transients) is tractable, particularly in the regime where non-linear motion begins to manifest itself.
-
The Size and Shape of the Oblong Dwarf Planet Haumea
Earth Moon and Planets, 2014Co-Authors: Alexandra C. Lockwood, Michael E. Brown, John StansberryAbstract:We use thermal radiometry and visible photometry to constrain the size, shape, and albedo of the large Kuiper belt object Haumea. The correlation between the visible and thermal photometry demonstrates that Haumea’s high amplitude and quickly varying optical light curve is indeed due to Haumea’s extreme shape, rather than large scale albedo variations. However, the well-sampled high precision visible data we present does require longitudinal surface heterogeneity to account for the shape of lightcurve. The thermal emission from Haumea is consistent with the expected Jacobi ellipsoid shape of a rapidly rotating body in hydrostatic equilibrium. The best Jacobi ellipsoid fit to the visible photometry implies a triaxial ellipsoid with axes of length 1,920 × 1,540 × 990 km and density $$2.6$$ 2.6 g cm $$^{-3}$$ - 3 , as found by Lellouch et al. (A&A, 518:L147, 2010 . doi: 10.1051/0004-6361/201014648 ). While the thermal and visible data cannot uniquely constrain the full non-spherical shape of Haumea, the match between the predicted and measured thermal flux for a dense Jacobi ellipsoid suggests that Haumea is indeed one of the densest objects in the Kuiper belt.
-
On the Size, Shape, and Density of Dwarf Planet Makemake
The Astrophysical Journal, 2013Co-Authors: Michael E. BrownAbstract:A recent stellar occultation by the Dwarf Planet Makemake provided an excellent opportunity to measure the size and shape of one of the largest objects in the Kuiper belt. The analysis of these results provided what were reported to be precise measurements of the lengths of the projected axes, the albedo, and even the density of Makemake, but these results were, in part, derived from qualitative arguments. We reanalyzed the occultation timing data using a quantitative statistical description, and, in general, found the previously reported results on the shape of Makemake to be unjustified. In our solution, in which we use our inference from photometric data that Makemake is being viewed nearly pole-on, we find a 1σ upper limit to the projected elongation of Makemake of 1.02, with measured equatorial diameter of 1434 ± 14 km and a projected polar diameter of 1422 ± 14 km, yielding an albedo of 0.81^(+0.01)_(−0.02). If we remove the external constraint on the pole position of Makemake, we find instead a 1σ upper limit to the elongation of 1.06, with a measured equatorial diameter of 1434^(+48)_(−18) km and a projected polar diameter of 1420^(+18)_(−24) km, yielding an albedo of 0.81^(+0.03)_(−0.05). Critically, we find that the reported measurement of the density of Makemake was based on the misapplication of the volatile retention models. A corrected analysis shows that the occultation measurements provide no meaningful constraint on the density of Makemake.
-
Orbits and Masses of the Satellites of the Dwarf Planet Haumea (2003 EL61)
The Astronomical Journal, 2009Co-Authors: Darin Ragozzine, Michael E. BrownAbstract:Using precise relative astrometry from the Hubble Space Telescope and the W. M. Keck Telescope, we have determined the orbits and masses of the two dynamically interacting satellites of the Dwarf Planet (136108) Haumea, formerly 2003 EL61. The orbital parameters of Hi'iaka, the outer, brighter satellite, match well the previously derived orbit. On timescales longer than a few weeks, no Keplerian orbit is sufficient to describe the motion of the inner, fainter satellite Namaka. Using a fully interacting three-point-mass model, we have recovered the orbital parameters of both orbits and the mass of Haumea and Hi'iaka; Namaka's mass is marginally detected. The data are not sufficient to uniquely determine the gravitational quadrupole of the nonspherical primary (described by J_2). The nearly coplanar nature of the satellites, as well as an inferred density similar to water ice, strengthen the hypothesis that Haumea experienced a giant collision billions of years ago. The excited eccentricities and mutual inclination point to an intriguing tidal history of significant semimajor axis evolution through satellite mean-motion resonances. The orbital solution indicates that Namaka and Haumea are currently undergoing mutual events and that the mutual event season will last for next several years.
Andreas Nathues - One of the best experts on this subject based on the ideXlab platform.
-
Mineralogical analysis of the Ac-H-6 Haulani quadrangle of the Dwarf Planet Ceres
Icarus, 2019Co-Authors: Federico Tosi, Francesca Zambon, Filippo Giacomo Carrozzo, Mauro Ciarniello, Martin Hoffmann, Andrea Longobardo, M C De Sanctis, Alessandro Frigeri, J. Ph. Combe, Andreas NathuesAbstract:Abstract Ac-H-6 ‘Haulani’ is one of five quadrangles that cover the equatorial region of the Dwarf Planet Ceres. This quadrangle is notable for the broad, spectrally distinct ejecta that originate from the crater Haulani, which gives the name to the quadrangle. These ejecta exhibit one of the most negative (‘bluest’) visible to near infrared spectral slope observed across the entire body and have distinct color properties as seen in multispectral composite images. Besides Haulani, here we investigate a broader area that includes other surface features of interest, with an emphasis on mineralogy as inferred from data obtained by Dawn's Visible InfraRed mapping spectrometer (VIR), combined with multispectral image products from the Dawn Framing Camera (FC) so as to enable a clear correlation with specific geologic features. Our analysis shows that crater Haulani stands out compared to other surface features of the quadrangle. Albedo maps obtained in the near infrared range at 1.2 µm and 1.9 µm reveal that the floor and ejecta of Haulani are indeed a patchwork of bright and dark material units. Visible to near-infrared spectral slopes display negative values in crater Haulani's floor and ejecta, highlighting bluish, younger terrains. Diagnostic spectral features centered at ∼2.7 µm and ∼3.1 µm respectively indicate a substantial decrease in the abundances of magnesium-bearing phyllosilicates and ammoniated phyllosilicates in crater Haulani's floor and bright ejecta. Similar, but less prominent, spectral behavior is observed in other geologic features of this quadrangle, while the general trend in quadrangle Ac-H-6 for these two mineral species is to increase from the northwest to the southeast. However, it is worth noting that the correlation between the ∼2.7 µm and ∼3.1 µm spectral parameters is generally strong in the Haulani crater's area, but much weaker elsewhere, which indicates a variable degree of mixing between these two major mineral phases in moving away from the crater. Finally, the region of crater Haulani displays a distinct thermal signature and a local enhancement in calcium and possibly sodium carbonate minerals, which is hardly found in the rest of the quadrangle and is likely the result of intense hydrothermal processes following the impact event. These evidences all together confirm the young age of crater Haulani, as they have not been erased or made elusive by space weathering processes.
-
Spectral properties and geology of bright and dark materials on Dwarf Planet Ceres
Meteoritics & Planetary Science, 2018Co-Authors: Guneshwar Thangjam, Andreas Nathues, M Hoffmann, Thomas Platz, Edward A Cloutis, Kurt Mengel, Matthew Richar Izawa, Daniel M. ApplinAbstract:Variations and spatial distributions of bright and dark material on Dwarf Planet Ceres play a key role for the understanding of the processes that have led to its present surface composition. We define limits for bright and dark material in order to distinguish them consistently, based on the reflectance with respect to the average surface using Dawn Framing Camera data. A systematic classification of four types of bright material is presented based on their spectral properties, composition, spatial distribution, and association with specific geomorphological features. We found obvious correlations of reflectance with spectral shape (slopes) and age; however, this is not unique throughout the bright spots. Although impact features show generally more extreme reflectance variations, several areas can only be understood in terms of inhomogeneous distribution of composition as inferred from Dawn Visible and Infrared Spectrometer data. Additional materials with anomalous composition and spectral properties are rare. The identification of the origin of the dark, and particularly the darkest, material remains to be explored. The spectral properties and the morphology of the dark sites suggest an endogenic origin, but it is not clear whether they are more or less primitive surficial exposures or excavated sub-surface but localized material. The reflectance, spectral properties, inferred composition, and geologic context collectively suggest that the bright and dark materials tend to gradually change towards the average surface over time. This could be because of multiple processes, i.e., impact gardening/space weathering, and lateral mixing, including thermal and aqueous alteration, accompanied with changes in composition and physical properties such as grain size, surface temperature, porosity (compaction).
-
The Geology of the Occator Quadrangle of Dwarf Planet Ceres: Floor-Fractured Craters and Other Geomorphic Evidence of Cryomagmatism.
Icarus, 2018Co-Authors: Debra L. Buczkowski, Ralf Jaumann, David A. Williams, Jennifer E.c. Scully, Paul M. Schenk, Scott C. Mest, David A. Crown, T. Roatsch, F. Preusker, Andreas NathuesAbstract:Abstract The Dawn Science Team is conducting a geological mapping campaign at Ceres during the nominal mission, including iterative mapping using data obtained during each orbital phase. We are using geological mapping as a method to identify the geologic processes that have modified the surface of Dwarf Planet Ceres. We here present the geology of the Ac-9 Occator quadrangle, located between 22˚S-22˚N and 216-288˚E. The Ac-9 map area is within the topographically high region named Hanami Planum. Features of note within the profile include impact craters Occator, Azacca, Lociyo, Nepen and Kirnis. Four of these craters have fractured, shallow floors, morphometrically comparable to floor-fractured craters (FFCs) on the Moon. Similar to models for the formation of the lunar FFCs, we suggest that these Ceres FFCs are a result of cryomagmatic uplift under the crater floors. A set of regional linear structures called the Samhain Catenae do not have any obvious relationship to impact craters. Many of the catenae are comprised of smaller structures that have linked together, suggestive of en echelon fractures. It has been suggested that these fractures formed due to the uplift of Hanami Planum due to cryromagmatic plumes.
-
The geology of the Kerwan quadrangle of Dwarf Planet Ceres: Investigating Ceres’ oldest, largest impact basin
Icarus, 2018Co-Authors: David A. Williams, Andreas Nathues, Thomas Platz, T Kneissl, Adrian Neesemann, Jennifer E.c. Scully, Andrea Longobardo, Scott C. Mest, Ernesto Palomba, Anton ErmakovAbstract:Abstract We conducted a geologic mapping investigation of Dawn spacecraft data to determine the geologic history of the Kerwan impact basin region of Dwarf Planet Ceres, which is mostly located in the Ac-7 Kerwan Quadrangle. Geological mapping was applied to Dawn Framing Camera images from the Low Altitude Mapping Orbit (LAMO, 35 m/pixel) and supplemented by digital terrain models and color images from the High Altitude Mapping Orbit (HAMO, 135 m/pixel), as well as preliminary Visible and Infrared Spectrometer (VIR) and gravity data. The 284-km diameter Kerwan impact basin is the oldest unequivocal impact crater on Ceres, and has a highly discontinuous, polygonal, degraded rim and contains a ‘smooth’ unit that both fills the basin floor and surrounds the degraded rim to the west, south, and east. Although there are some subtle topographic features in the Kerwan basin that could be interpreted as flow boundaries, there is no indisputable evidence of cryovolcanic features in or around the basin (however if such features existed they could be buried). Nevertheless, all data point to impact-induced melting of a cerean crust enriched in a volatile, likely water ice, to produce the Kerwan smooth material. Subsequent geologic activity in this region includes emplacement of impact craters such as Dantu, which produced a variety of colorful deposits, and rayed craters such as Rao and Cacaguat. Based on the crater size-frequency distribution absolute model ages of the Kerwan smooth material in and around the basin, marking a minimum age for the Kerwan basin, our mapping defines this as the oldest boundary within the cerean geologic timescale, separating the Pre-Kerwanan and Kerwanan Periods at > 1.3 Ga (Lunar-derived chronology model) or > 230–850 Ma (Asteroid-derived chronology model, depending on strength of target material).
-
Geomorphological evidence for ground ice on Dwarf Planet Ceres
Nature Geoscience, 2017Co-Authors: Britney E. Schmidt, Andreas Nathues, Thomas Platz, Jennifer E.c. Scully, Hanna G. Sizemore, Kynan H. G. Hughson, H. T. Chilton, Michael T. Bland, Shane Byrne, Simone MarchiAbstract:Despite evidence for an ice-rich outer shell, little water ice has been observed on the surface of Ceres. Lobate morphologies observed on Ceres that are increasingly prevalent towards the Dwarf Planet’s poles are consistent with ice-rich flows.
Darin Ragozzine - One of the best experts on this subject based on the ideXlab platform.
-
Modeling the Formation of the Family of the Dwarf Planet Haumea
The Astronomical Journal, 2019Co-Authors: Benjamin Proudfoot, Darin RagozzineAbstract:The Dwarf Planet (136108) Haumea has an intriguing combination of unique physical properties: near-breakup spin, two regular satellites, and an unexpectedly compact family. While these properties indicate formation by collision, there is no self-consistent and reasonably probable formation hypothesis that can connect the unusually rapid spin and the low relative velocities of Haumea family members ("Haumeans"). We explore and test the proposed formation hypotheses (catastrophic collision, graze-and-merge, and satellite collision). We flexibly parameterize the properties of the collision (e.g., the collision location) and use simple models for the three-dimensional velocity ejection field expected from each model to generate simulated families. These are compared to observed Kuiper Belt Objects using Bayesian parameter inference, including a mixture model that allows for interlopers from the background population. After testing our methodology, we find the best match to the observed Haumeans is an isotropic ejection field with a typical velocity of 150 m s$^{-1}$. The graze-and-merge and satellite collision hypotheses are disfavored. Including these constraints, we discuss the formation hypotheses in detail, including variations, some of which are tested. Some new hypotheses are proposed (a cratering collision and a collision where Haumea's upper layers are "missing") and scrutinized. We do not identify a satisfactory formation hypothesis, but we do propose several avenues of additional investigation. In addition, we identify many new candidate Haumeans and dynamically confirm 7 of them as consistent with the observed family. We confirm that Haumeans have a shallow size distribution and discuss implications for the identification of new Haumeans.
-
A Deep Search for Additional Satellites around the Dwarf Planet Haumea
The Astronomical Journal, 2016Co-Authors: Luke Burkhart, Darin Ragozzine, Michael E. BrownAbstract:Haumea is a Dwarf Planet with two known satellites, an unusually high spin rate, and a large collisional family, making it one of the most interesting objects in the outer solar system. A fully self-consistent formation scenario responsible for the satellite and family formation is still elusive, but some processes predict the initial formation of many small moons, similar to the small moons recently discovered around Pluto. Deep searches for regular satellites around Kuiper belt objects are difficult due to observational limitations, but Haumea is one of the few for which sufficient data exist. We analyze Hubble Space Telescope (HST) observations, focusing on a 10-consecutive-orbit sequence obtained in 2010 July, to search for new very small satellites. To maximize the search depth, we implement and validate a nonlinear shift-and-stack method. No additional satellites of Haumea are found, but by implanting and recovering artificial sources, we characterize our sensitivity. At distances between ~10,000 and ~350,000 km from Haumea, satellites with radii as small as ~10 km are ruled out, assuming an albedo (p ≃ 0.7) similar to Haumea. We also rule out satellites larger than ≳40 km in most of the Hill sphere using other HST data. This search method rules out objects similar in size to the small moons of Pluto. By developing clear criteria for determining the number of nonlinear rates to use, we find that far fewer shift rates are required (~35) than might be expected. The nonlinear shift-and-stack method to discover satellites (and other moving transients) is tractable, particularly in the regime where nonlinear motion begins to manifest itself.
-
a deep search for additional satellites around the Dwarf Planet haumea
arXiv: Earth and Planetary Astrophysics, 2016Co-Authors: Luke Burkhart, Darin Ragozzine, Michael E. BrownAbstract:Haumea is a Dwarf Planet with two known satellites, an unusually high spin rate, and a large collisional family, making it one of the most interesting objects in the outer solar system. A fully self-consistent formation scenario responsible for the satellite and family formation is still elusive, but some processes predict the initial formation of many small moons, similar to the small moons recently discovered around Pluto. Deep searches for regular satellites around KBOs are difficult due to observational limitations, but Haumea is one of the few for which sufficient data exist. We analyze Hubble Space Telescope (HST) observations, focusing on a ten-consecutive-orbit sequence obtained in July 2010, to search for new very small satellites. To maximize the search depth, we implement and validate a non-linear shift-and-stack method. No additional satellites of Haumea are found, but by implanting and recovering artificial sources, we characterize our sensitivity. At distances between $\sim$10,000 km and $\sim$350,000 km from Haumea, satellites with radii as small as $\sim$10 km are ruled out, assuming an albedo ($p \simeq 0.7$) similar to Haumea. We also rule out satellites larger than $\gtrsim$40 km in most of the Hill sphere using other HST data. This search method rules out objects similar in size to the small moons of Pluto. By developing clear criteria for determining the number of non-linear rates to use, we find that far fewer shift rates are required ($\sim$35) than might be expected. The non-linear shift-and-stack method to discover satellites (and other moving transients) is tractable, particularly in the regime where non-linear motion begins to manifest itself.
-
Orbits and Masses of the Satellites of the Dwarf Planet Haumea (2003 EL61)
The Astronomical Journal, 2009Co-Authors: Darin Ragozzine, Michael E. BrownAbstract:Using precise relative astrometry from the Hubble Space Telescope and the W. M. Keck Telescope, we have determined the orbits and masses of the two dynamically interacting satellites of the Dwarf Planet (136108) Haumea, formerly 2003 EL61. The orbital parameters of Hi'iaka, the outer, brighter satellite, match well the previously derived orbit. On timescales longer than a few weeks, no Keplerian orbit is sufficient to describe the motion of the inner, fainter satellite Namaka. Using a fully interacting three-point-mass model, we have recovered the orbital parameters of both orbits and the mass of Haumea and Hi'iaka; Namaka's mass is marginally detected. The data are not sufficient to uniquely determine the gravitational quadrupole of the nonspherical primary (described by J_2). The nearly coplanar nature of the satellites, as well as an inferred density similar to water ice, strengthen the hypothesis that Haumea experienced a giant collision billions of years ago. The excited eccentricities and mutual inclination point to an intriguing tidal history of significant semimajor axis evolution through satellite mean-motion resonances. The orbital solution indicates that Namaka and Haumea are currently undergoing mutual events and that the mutual event season will last for next several years.
-
orbits and masses of the satellites of the Dwarf Planet haumea 2003 el61
arXiv: Earth and Planetary Astrophysics, 2009Co-Authors: Darin Ragozzine, Michael E. BrownAbstract:Using precise relative astrometry from the Hubble Space Telescope and the W. M. Keck Telescope, we have determined the orbits and masses of the two dynamically interacting satellites of the Dwarf Planet (136108) Haumea, formerly 2003 EL61. The orbital parameters of Hi'iaka, the outer, brighter satellite, match well the previously derived orbit. On timescales longer than a few weeks, no Keplerian orbit is sufficient to describe the motion of the inner, fainter satellite Namaka. Using a fully-interacting three point-mass model, we have recovered the orbital parameters of both orbits and the mass of Haumea and Hi'iaka; Namaka's mass is marginally detected. The data are not sufficient to uniquely determine the gravitational quadrupole of the non-spherical primary (described by $J_2$). The nearly co-planar nature of the satellites, as well as an inferred density similar to water ice, strengthen the hypothesis that Haumea experienced a giant collision billions of years ago. The excited eccentricities and mutual inclination point to an intriguing tidal history of significant semi-major axis evolution through satellite mean-motion resonances. The orbital solution indicates that Namaka and Haumea are currently undergoing mutual events and that the mutual event season will last for the next several years.
Bruno Sicardy - One of the best experts on this subject based on the ideXlab platform.
-
Results of two multichord stellar occultations by Dwarf Planet (1) Ceres
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: A. R. Gomes-júnior, Bruno Sicardy, Breno L. Giacchini, F. Braga-ribas, Marcelo Assafin, R. Vieira-martins, Julio Camargo, Brad Timerson, T. George, J. BroughtonAbstract:We report the results of two multi-chord stellar occultations by the Dwarf Planet (1) Ceres that were observed from Brazil on 2010 August 17, and from the USA on 2013 October 25. Four positive detections were obtained for the 2010 occultation, and nine for the 2013 occultation. Elliptical models were adjusted to the observed chords to obtain Ceres’ size and shape. Two limb fitting solutions were studied for each event. The first one is a nominal solution with an indeterminate polar aspect angle. The second one was constrained by the pole coordinates as given by Drummond et al. Assuming a Maclaurin spheroid, we determine an equatorial diameter of 972 6 km and an apparent oblateness of 0:08 0:03 as our best solution. These results are compared to all available size and shape determinations for Ceres made so far, and shall be confirmed by the NASA’s Dawn space mission.
-
albedo and atmospheric constraints of Dwarf Planet makemake from a stellar occultation
Nature, 2012Co-Authors: J L Ortiz, Bruno Sicardy, F Bragaribas, A Alvarezcandal, E Lellouch, R Duffard, N Pinillaalonso, V D Ivanov, S P Littlefair, J I B CamargoAbstract:The icy Dwarf Planet Makemake has projected axes of 1,430 ± 9 and 1,502 ± 45 km and a V-band geometric albedo larger than Pluto’s but smaller than Eris’s, with no global Pluto-like atmosphere. Makemake is thought to be the third-largest Dwarf Planet in our Solar System, a little smaller than Pluto and Eris, but until now knowledge of its size and albedo were only approximate. This paper reports the results of observations of the occultation of a faint star known as NOMAD 1181-0235723 by Makemake on 23 April 2011. The data confirm that Makemake is smaller than Pluto and Eris, with axes of 1,430±9 km and 1,502±45 km. Makemake's mean geometric albedo — the ratio of light reflected to light received — is intermediate between that of Pluto and that of Eris. All three are icy, making them among the most reflective objects in the Solar System. And the occultation light curves rule out the presence of a global Pluto-like atmosphere on Makemake, although the presence of dark terrain might imply the presence of a localized atmosphere. Pluto and Eris are icy Dwarf Planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies1,2. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos3. Makemake is another icy Dwarf Planet with a spectrum similar to Eris and Pluto4, and is currently at a distance to the Sun intermediate between the two. Although Makemake’s size (1,420 ± 60 km) and albedo are roughly known5,6, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere4,7,8. Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430 ± 9 km (1σ) and 1,502 ± 45 km, implying a V-band geometric albedo pV = 0.77 ± 0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4–12 nanobar (1σ) for the surface pressure, although a localized atmosphere is possible. A density of 1.7 ± 0.3 g cm−3 is inferred from the data.
-
Albedo and atmospheric constraints of Dwarf Planet Makemake from a stellar occultation
Nature, 2012Co-Authors: J L Ortiz, Bruno Sicardy, E Lellouch, R Duffard, V D Ivanov, S P Littlefair, F. Braga-ribas, A. Alvarez-candal, N. Pinilla-alonso, J I B CamargoAbstract:Pluto and Eris are icy Dwarf Planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos. Makemake is another icy Dwarf Planet with a spectrum similar to Eris and Pluto, and is currently at a distance to the Sun intermediate between the two. Although Makemake's size (1,420 +/- 60 km) and albedo are roughly known, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere. Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430 +/- 9 km (1σ) and 1,502 +/- 45 km, implying a V-band geometric albedo pV = 0.77 +/- 0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4-12 nanobar (1σ) for the surface pressure, although a localized atmosphere is possible. A density of 1.7 +/- 0.3 g cm-3 is inferred from the data.
-
a pluto like radius and a high albedo for the Dwarf Planet eris from an occultation
Nature, 2011Co-Authors: J L Ortiz, Bruno Sicardy, F Bragaribas, E Lellouch, M Assafin, Emmanuel Jehin, A Maury, Gil R Hutton, Francois ColasAbstract:The Dwarf Planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 UT. The event is consistent with a spherical shape for Eris, with radius 1,163+/-6kilometres, density 2.52+/-0.05 grams per cm3 and a high visible geometric albedo, . No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ~1nanobar, about 10,000 times more tenuous than Pluto's present atmosphere. As Pluto's radius is estimated to be between 1,150 and 1,200 kilometres, Eris appears as a Pluto twin, with a bright surface possibly caused by a collapsed atmosphere, owing to its cold environment. We anticipate that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun.
J L Ortiz - One of the best experts on this subject based on the ideXlab platform.
-
Long-term photometric monitoring of the Dwarf Planet (136472) Makemake
Astronomy & Astrophysics, 2019Co-Authors: T. A. Hromakina, J L Ortiz, Irina Belskaya, René Duffard, Nicolás Morales, Yu. N. Krugly, Vasilij G. Shevchenko, Pablo Santos-sanz, Audrey Thirouin, R. Ya. InasaridzeAbstract:We studied the rotational properties of the Dwarf Planet Makemake. The photometric observations were carried out at different telescopes between 2006 and 2017. Most of the measurements were acquired in BVRI broad-band filters of a standard Johnson-Cousins photometric system. We found that Makemake rotates more slowly than was previously reported. A possible lightcurve asymmetry suggests a double-peaked period of P = 22.8266$\pm$0.0001~h. A small peak-to-peak lightcurve amplitude in R-filter A = 0.032$\pm$0.005 mag implies an almost spherical shape or near pole-on orientation. We also measured BVRI colours and the R-filter phase-angle slope and revised the absolute magnitudes. The absolute magnitude of Makemake has remained unchanged since its discovery in 2005. No direct evidence of a newly discovered satellite was found in our photometric data; however, we discuss the possible existence of another larger satellite.
-
albedo and atmospheric constraints of Dwarf Planet makemake from a stellar occultation
Nature, 2012Co-Authors: J L Ortiz, Bruno Sicardy, F Bragaribas, A Alvarezcandal, E Lellouch, R Duffard, N Pinillaalonso, V D Ivanov, S P Littlefair, J I B CamargoAbstract:The icy Dwarf Planet Makemake has projected axes of 1,430 ± 9 and 1,502 ± 45 km and a V-band geometric albedo larger than Pluto’s but smaller than Eris’s, with no global Pluto-like atmosphere. Makemake is thought to be the third-largest Dwarf Planet in our Solar System, a little smaller than Pluto and Eris, but until now knowledge of its size and albedo were only approximate. This paper reports the results of observations of the occultation of a faint star known as NOMAD 1181-0235723 by Makemake on 23 April 2011. The data confirm that Makemake is smaller than Pluto and Eris, with axes of 1,430±9 km and 1,502±45 km. Makemake's mean geometric albedo — the ratio of light reflected to light received — is intermediate between that of Pluto and that of Eris. All three are icy, making them among the most reflective objects in the Solar System. And the occultation light curves rule out the presence of a global Pluto-like atmosphere on Makemake, although the presence of dark terrain might imply the presence of a localized atmosphere. Pluto and Eris are icy Dwarf Planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies1,2. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos3. Makemake is another icy Dwarf Planet with a spectrum similar to Eris and Pluto4, and is currently at a distance to the Sun intermediate between the two. Although Makemake’s size (1,420 ± 60 km) and albedo are roughly known5,6, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere4,7,8. Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430 ± 9 km (1σ) and 1,502 ± 45 km, implying a V-band geometric albedo pV = 0.77 ± 0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4–12 nanobar (1σ) for the surface pressure, although a localized atmosphere is possible. A density of 1.7 ± 0.3 g cm−3 is inferred from the data.
-
Albedo and atmospheric constraints of Dwarf Planet Makemake from a stellar occultation
Nature, 2012Co-Authors: J L Ortiz, Bruno Sicardy, E Lellouch, R Duffard, V D Ivanov, S P Littlefair, F. Braga-ribas, A. Alvarez-candal, N. Pinilla-alonso, J I B CamargoAbstract:Pluto and Eris are icy Dwarf Planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos. Makemake is another icy Dwarf Planet with a spectrum similar to Eris and Pluto, and is currently at a distance to the Sun intermediate between the two. Although Makemake's size (1,420 +/- 60 km) and albedo are roughly known, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere. Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430 +/- 9 km (1σ) and 1,502 +/- 45 km, implying a V-band geometric albedo pV = 0.77 +/- 0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4-12 nanobar (1σ) for the surface pressure, although a localized atmosphere is possible. A density of 1.7 +/- 0.3 g cm-3 is inferred from the data.
-
a pluto like radius and a high albedo for the Dwarf Planet eris from an occultation
Nature, 2011Co-Authors: J L Ortiz, Bruno Sicardy, F Bragaribas, E Lellouch, M Assafin, Emmanuel Jehin, A Maury, Gil R Hutton, Francois ColasAbstract:The Dwarf Planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 UT. The event is consistent with a spherical shape for Eris, with radius 1,163+/-6kilometres, density 2.52+/-0.05 grams per cm3 and a high visible geometric albedo, . No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ~1nanobar, about 10,000 times more tenuous than Pluto's present atmosphere. As Pluto's radius is estimated to be between 1,150 and 1,200 kilometres, Eris appears as a Pluto twin, with a bright surface possibly caused by a collapsed atmosphere, owing to its cold environment. We anticipate that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun.
-
A study of photometric variations on the Dwarf Planet (136199) Eris
Astronomy & Astrophysics, 2007Co-Authors: René Duffard, J L Ortiz, P. Santos Sanz, Alcione Mora, P. J. Gutiérrez, Nicolás Morales, D. GuiradoAbstract:Context. Eris is the largest Dwarf Planet currently known in the solar system. Knowledge about its physical parameters is necessary to interpret the characteristics of these kinds of bodies. Aims. The goal of this work is to study Eris' short-term and long-term variability in order to determine the amplitude of the lightcurve, which can be linked to the degree of elongation of the body or to the degree of albedo heterogeneity on the surface of the Dwarf Planet. In addition, the rotation period can be determined. Methods. CCD photometric observations of the trans Neptunian object Eris in R band on 16 nights spanning two years were carried out using the 1.5 m telescope at Sierra Nevada Observatory (OSN), the 2.5 m Isaac Newton Telescope (INT) telescope at the Roque de los Muchachos Observatory, and the 2.2 m Telescope at Calar Alto Observatory. Results. The time-series analysis leads to indications of a short-term variability whose nature is not clear. It could be real or a result of data-reduction artifacts, such as contamination by close, faint-background stars. The most significant periodicities are 14 h or its double, but other possibilities cannot be ruled out, like a 32 h weaker peak in the periodogram. As for the amplitude of the lightcurve, we get a peak-to-peak variability of 0.01 ± 0.01 mag. The study of the long-term variability indicates that a long rotation period cannot be rejected, but the amplitude would be smaller than 0.06 mag. These results are compatible with a nearly spherical body that has a homogeneous surface.
