Search NASA⌕ Search

SEARCH · Search NASA

Results for “NEPTUNE”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

TOI–757 b: an eccentric transiting mini–Neptune on a 17.5–d orbit

ABSTRACT We report the spectroscopic confirmation and fundamental properties of TOI$-$757 b, a mini$-$Neptune on a 17.5$-$d orbit transiting a bright star ($V\, =\, 9.7$ mag) discovered by the TESS mission. We acquired high$-$precision radial velocity measurements with the HARPS, ESPRESSO, and PFS spectrographs to confirm the planet detection and determine its mass. We also acquired space$-$borne transit photometry with the CHEOPS space telescope to place stronger constraints on the planet radius, supported with ground$-$based LCOGT photometry. WASP and KELT photometry were used to help constrain the stellar rotation period. We also determined the fundamental parameters of the host star. We find that TOI$-$757 b has a radius of $R_{\mathrm{p}} = 2.5 \pm 0.1 R_{\oplus }$ and a mass of $M_{\mathrm{p}} = 10.5^{+2.2}_{-2.1} M_{\oplus }$, implying a bulk density of $\rho _{\text{p}} = 3.6 \pm 0.8$ g cm$^{-3}$. Our internal composition modelling was unable to constrain the composition of TOI$-$757 b, highlighting the importance of atmospheric observations for the system. We also find the planet to be highly eccentric with e = 0.39$^{+0.08}_{-0.07}$, making it one of the very few highly eccentric planets among precisely characterized mini$-$Neptunes. Based on comparisons to other similar eccentric systems, we find a likely scenario for TOI$-$757 b’s formation to be high eccentricity migration due to a distant outer companion. We additionally propose the possibility of a more intrinsic explanation for the high eccentricity due to star$-$star interactions during the earlier epoch of the Galactic disc formation, given the low metallicity and older age of TOI$-$757.

Alqasim, A. (ORCID:0000000151025505)↗
DOE OSTI2022

CRADA Number NFE-19-07867 with Neptune Fluid Flow Systems (CRADA Final Report)

Neptune Fluid Flow Systems is a rising engineering firm with a technology focus in improving cryogenic sample preparation for cryogenic-transmission electron microscopy (cryo-TEM) studies. To advance the R&D of its innovative cryogenic preparation method, Neptune has teamed up with the Center for Nanophase Materials Science (CNMS) at Oak Ridge National Laboratory (ORNL) to achieve the following aims: (1) validate the technical feasibility of CryoSheet sample prep method, (2) design, fabricate and test the cryo-stage support, and (3) experiment and achieve success with the novel sample preparation method on different soft matters.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Information Content of JWST NIRSpec Transmission Spectra of Warm Neptunes

Warm Neptunes offer a rich opportunity for understanding exo-atmospheric chemistry. With the upcoming James Webb Space Telescope (JWST), there is a need to elucidate the balance between investments in telescope time versus scientific yield. We use the supervised machine-learning method of the random forest to perform an information content (IC) analysis on a 11-parameter model of transmission spectra from the various NIRSpec modes. The three bluest medium-resolution NIRSpec modes (0.7–1.27 μm, 0.97–1.84 μm, 1.66–3.07 μm) are insensitive to the presence of CO. The reddest medium-resolution mode (2.87–5.10 μm) is sensitive to all of the molecules assumed in our model: CO, CO{sub 2}, CH{sub 4}, C{sub 2}H{sub 2}, H{sub 2}O, HCN, and NH{sub 3}. It competes effectively with the three bluest modes on the information encoded on cloud abundance and particle size. It is also competitive with the low-resolution prism mode (0.6–5.3 μm) on the inference of every parameter except for the temperature and ammonia abundance. We recommend astronomers to use the reddest medium-resolution NIRSpec mode for studying the atmospheric chemistry of 800–1200 K warm Neptunes; its corresponding high-resolution counterpart offers diminishing returns. We compare our findings to previous JWST IC analyses that favor the blue orders and suggest that the reliance on chemical equilibrium could lead to biased outcomes if this assumption does not apply. A simple, pressure-independent diagnostic for identifying chemical disequilibrium is proposed based on measuring the abundances of H{sub 2}O, CO, and CO{sub 2}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

HATS-37Ab and HATS-38b: Two Transiting Hot Neptunes in the Desert

We report the discovery of two transiting Neptunes by the HATSouth survey. The planet HATS-37Ab has a mass of 0.099±0.042 M{sub J} (31.5 ± 13.4 M {sub ⊕}) and a radius of 0.606±0.016 R{sub J}, and is on a P=4.3315 day orbit around a V=12.266±0.030 mag, 0.843{sub −0.012}{sup +0.017} M{sub ⊙} star with a radius of 0.877{sub −0.012}{sup +0.019} R{sub ⊙}. We also present evidence that the star HATS-37A has an unresolved stellar companion HATS-37B, with a photometrically estimated mass of 0.654±0.033 M{sub ⊙}. The planet HATS-38b has a mass of 0.074±0.011 M{sub J} (23.5 ± 3.5 M {sub ⊕}) and a radius of 0.614±0.017 R{sub J}, and is on a P=4.3750 day orbit around a V=12.411±0.030 mag, 0.890{sub −0.012}{sup +0.016} M{sub ⊙} star with a radius of 1.105±0.016 R{sub ⊙}. Both systems appear to be old, with isochrone-based ages of 11.46{sub −1.45}{sup +0.79} Gyr, and 11.89±0.60 Gyr, respectively. Both HATS-37Ab and HATS-38b lie in the Neptune desert and are thus examples of a population with a low occurrence rate. They are also among the lowest-mass planets found from ground-based wide-field surveys to date.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

The Habitable Zone Planet Finder Reveals a High Mass and Low Obliquity for the Young Neptune K2-25b

Using radial velocity data from the Habitable Zone Planet Finder, we have measured the mass of the Neptune-sized planet K2-25b, as well as the obliquity of its M4.5 dwarf host star in the 600–800 Myr Hyades cluster. This is one of the youngest planetary systems for which both of these quantities have been measured and one of the very few M dwarfs with a measured obliquity. Based on a joint analysis of the radial velocity data, time-series photometry from the K2 mission, and new transit light curves obtained with diffuser-assisted photometry, the planet’s radius and mass are 3.44 ± 0.12 R {sub ⊕} and 24.5{sub −5.2}{sup +5.7}M{sub ⊕}. These properties are compatible with a rocky core enshrouded by a thin hydrogen–helium atmosphere (5% by mass). We measure an orbital eccentricity of e = 0.43 ± 0.05. The sky-projected stellar obliquity is λ = 3° ± 16°, compatible with spin–orbit alignment, in contrast to other “hot Neptunes” that have been studied around older stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Nondetection of Helium in the Upper Atmospheres of Three Sub-Neptune Exoplanets

We present a search for helium in the upper atmospheres of three sub-Neptune-sized planets to investigate the origins of these ubiquitous objects. The detection of helium for a low-density planet would be strong evidence for the presence of a primary atmosphere accreted from the protoplanetary nebula because large amounts of helium are not expected in the secondary atmospheres of rocky planets. We used Keck+NIRSPEC to obtain high-resolution transit spectroscopy of the planets GJ 1214b, GJ 9827d, and HD 97658b around the 10833 Å He triplet feature. We did not detect helium absorption for any of the planets despite achieving a high level of sensitivity. We used the nondetections to set limits on the planets’ thermosphere temperatures and atmospheric loss rates by comparing grids of 1D models to the data. We also performed coupled interior structure and atmospheric loss calculations, which suggest that the bulk atmospheres (winds) of the planets would be at most modestly enhanced (depleted) in helium relative to their primordial composition. Our lack of detections of the helium triplet for GJ 1214b and GJ 9827d is highly inconsistent with the predictions of models for the present-day mass loss on these planets. Higher signal-to-noise data would be needed to detect the helium feature predicted for HD 97658b. We identify uncertainties in the extreme-ultraviolet fluxes of the host stars and the lack of detailed mass-loss models specifically for cool and metal-enhanced atmospheres as the main limitations to the interpretation of our results. Ultimately, our results suggest that the upper atmospheres of sub-Neptune planets are fundamentally different from those of gas giant planets.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1972

First generation atmospheric probes (10-BARS) for Uranus and Neptune

The feasibility of atmospheric entry probe missions to Uranus and Neptune is studied, and preliminary estimates of missions parameters are presented. Most of the study results are applicable, with only minor modifications, to Uranus-Neptune entry probes included on any type of outer planet mission. Trajectory dynamics is discussed first because it imposes some important constraints upon the total time available for data transmission, which in turn determines the descent rate. This last quantity provides important information for the design of the scientific payload.

Sullivan, R. J.↗
NASA NTRS1974

Evidence for an internal heat source in Neptune

Analysis of Morrison and Cruikshank's (1974) infrared flux measurements of Uranus and Neptune shows that Uranus is probably in equilibrium with the incident solar flux, while Neptune probably radiates 2.4 times as much energy as it receives from the sun, implying an internal heat source of 1.4 times the solar input. On the basis of very broadband data (1.5 to 300 micron) Jupiter has been shown to radiate more energy than it receives from the sun. Of the Jovian planets, only Uranus, the least massive, appears to lack an internal heat source.

Murphy, R. E.↗
NASA NTRS1974

Neptune - Observations of the H2 quadrupole lines in the /4-0/ band

The first measurement of Neptune's quadrupole H2 lines is reported. The equivalent widths of the S(0) and S(1) lines of the (4-0) band are given along with the corresponding widths measured from comparison spectra of Uranus taken on the same nights. These are interpreted in terms of both an inhomogeneous atmosphere overlying a reflecting layer and a homogeneous, semi-infinite, scattering atmosphere. Only the scattering model proves to be consistent with Neptune's spectrum in this wavelength region. The H2 abundance along the scattering mean free path is found to be less than the value for Rayleigh scattering in pure H2. This result is interpreted in terms of the presence of H2, CH4, and at least one other gas, instead of the more conventional interpretation in terms of the presence of an aerosol mixed with H2. Weak features in the continuum were observed. Their widths and the strength of the H2 features indicate that H2 is more abundant than the sum of the remaining gases in these atmospheres.

Trafton, L.↗
NASA NTRS1977

Evidence for weather on Neptune. I

Between April 1975 and March 1976 the reflectance of Neptune between 1 and 4 microns increased substantially. A spectrum taken at these wavelengths near the period of peak observed brightness showed a low-intensity continuum with weak superposed absorptions caused by CH4 and H2. Photographic spectra of the planet measured during the same period showed no differences from older published data. The gas abundances derived from the infrared spectrum, 5 plus or minus 2 km-amagat of H2 at a base density of 0.26 plus or minus 0.08 am and no more than about 1 m-am of CH4, appear to refer to an effective reflecting level high in the atmosphere of Neptune.

Joyce, R. R.↗
NASA NTRS1977

Evidence for weather on Neptune. II

Data obtained by Joyce et al., (1977) are interpreted as evidence for the formation of an optically-thin cloud high in the atmosphere of Neptune. About 10 months after the cloud's initial appearance and subsequent partial dissipation, the optical thickness of the cloud, averaged over the planet, had a value for tau in the vicinity of 1. The minimum effective radius indicated for the cloud particles is about 1 micron. The model which leads to this interpretation of the data is explained, and the calculations are presented. Implications of the model and also apparent similarities between Neptune's atmosphere and that of other planets are discussed.

Pilcher, C. B.↗
NASA NTRS1977

The ionospheres of Saturn, Uranus, and Neptune

Models of the ionospheres of Saturn, Uranus, and Neptune are presented. It is postulated that galactic cosmic-ray ionization is an important component of these ionospheres. For example, in the case of Neptune, the level of ionization caused by cosmic rays is comparable with that due to solar extreme-ultraviolet (EUV) radiation. The existence of cosmic-ray, as well as solar EUV-produced ionization, could be a valuable diagnostic tool for investigating the atmospheric thermal structure of those planets.

Capone, L. A.↗
NASA NTRS1977

The effective temperature of Neptune

The brightness temperature of Neptune has been measured in two broad passbands with flux-weighted mean wavelengths of 45 and 93 microns, permitting a direct determination of its effective temperature. The derived value of 55.5 plus or minus 2.3 K implies that Neptune radiates twice as much power as it receives from the sun.

Loewenstein, R. F.↗
NASA NTRS1978

On the rotation period of Neptune

Two plausible values for the rotation period of Neptune have been deduced from photometric light curves at 1.25 and 2.2 microns. They are 0.7572 + or - 0.002 and 0.8160 + or - 0.002 day; additional photometric data will be required to ascertain which period is correct. Evidence is presented for changes in the atmosphere of Neptune with a time scale of several days.

Cruikshank, D. P.↗
NASA NTRS1979

The infrared spectra of Uranus, Neptune, and Titan from 0.8 to 2.5 microns

The paper combines the results of two projects that significantly augment previous studies: exploratory IR spectroscopic observations of Uranus, Neptune, and Titan using a 4-m telescope; and new long-path laboratory comparison spectra of methane at abundances appropriate for these planetary spectra. The observations of these previously unexplored spectral regimes provide new insights into the composition and structures of these atmospheres. The spectra of Uranus, Neptune, and Titan are discussed and analyzed from several complementary points of view. A number of specific topics are discussed in detail: methane abundance determinations, limitations in using the 3nu3 CH4 band at high abundances, upper limits to a number of molecules, implications from the pressure-induced spectrum of H2, and consequences of Rayleigh scattering in Uranus's upper atmosphere.

Fink, U.↗
NASA NTRS1980

Ultraviolet albedos of Uranus and Neptune

Observations on Uranus, Neptune, and four G-type stars which were obtained with the five channel ultraviolet spectrometer aboard the Astronomical Netherlands Satellite are reported. The paper uses these data to derive geometric albedos between 1800 and 3300 A for Uranus and between 2200 and 3300 A for Neptune. It is shown that the albedos are in good agreement with ground measurements near 3300 A and with OAO 2 measurements near 2500 A. In addition, it is noted that the albedos are smaller than theoretical predictions for deep pure H2 Rayleigh-Raman scattering atmospheres, which confirms earlier predictions that additional sources of ultraviolet absorption are required in the upper atmosphere of these planets. Consideration is given to the possibility that the Uranian atmosphere contains an extra absorber, noting that the identification of this absorber is difficult from broad-band spectrophotometric measurements.

Savage, B. D.↗
NASA NTRS1980

Five-micrometer measurements of Uranus and Neptune

Five-micron brightness temperatures and brightness temperature upper limits for Uranus and Neptune have been obtained which are substantially lower than those of Jupiter and Saturn and which correspond to a geometric albedo of approximately 0.01, in agreement with results reported by Gillett and Rieke (1977). Phosphine and CH3D, which are observed at 5 microns on Jupiter and Saturn, are discussed as possible sources of opacity at 5 microns in the atmospheres of Uranus and Neptune.

Macy, W. W., Jr.↗
NASA NTRS1980

Measurements of the H2 4-0 quadrupole bands of Uranus and Neptune

It is found that the equivalent widths of the lines of the 4-0 H2 quadrupole band on Uranus and Neptune are substantially smaller than the values found by some previous observers. An analysis of the results based on a range of atmospheric models yields H2 abundances of 240 + or - 60 km-amagats for Uranus and greater than approximately 200 km amagats for Neptune.

Smith, W. H.↗