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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

STIS Coronagraphic Imaging of Fomalhaut: Main Belt Structure and the Orbit of Fomalhaut b

We present new optical coronagraphic data of Fomalhaut obtained with HST/STIS in 2010 and 2012. Fomalhaut b is recovered at both epochs to high significance. The observations include the discoveries of tenuous nebulosity beyond the main dust belt detected to at least 209AU projected radius, and a approx. 50AU wide azimuthal gap in the belt northward of Fomalhaut b. The two epochs of Space Telescope Imaging Spectrograph (STIS) photometry exclude optical variability greater than 35%. A Markov chain Monte Carlo analysis demonstrates that the orbit of Fomalhaut b is highly eccentric, with e = 0.8 +/- 0.1, a = 177 +/- 68AU, and q = 32 +/- 24AU. Fomalhaut b is apsidally aligned with the belt and 90% of allowed orbits have mutual inclination <=36 deg. Fomalhaut b's orbit is belt crossing in the sky plane projection, but only 12% of possible orbits have ascending or descending nodes within a 25AU wide belt annulus. The high eccentricity invokes a dynamical history where Fomalhaut b may have experienced a significant dynamical interaction with a hypothetical planet Fomalhaut c, and the current orbital configuration may be relatively short-lived. The Tisserand parameter with respect to a hypothetical Fomalhaut planet at 30AU or 120AU lies in the range 2-3, similar to highly eccentric dwarf planets in our solar system. We argue that Fomalhaut b's minimum mass is that of a dwarf planet in order for a circumplanetary satellite system to remain bound to a sufficient radius from the planet to be consistent with the dust scattered light hypothesis. In the coplanar case, Fomalhaut b will collide with the main belt around 2032, and the subsequent emergent phenomena may help determine its physical nature.

Tisserand parameter↗
NASA NTRS2018

ADS-B Mixed sUAS and NAS System Capacity Analysis and DAA Performance

Automatic Dependent Surveillance-Broadcast (ADS-B) technology was introduced more than twenty years ago to improve surveillance within the US National Airspace Space (NAS) as well as in many other countries. Via the NextGen initiative, implementation of ADS-B technology across the US is planned in stages between 2012 and 2025. ADS-B's automatic one second epoch packet transmission exploits on-board GPS-derived navigational information to provide position information, as well as other information including vehicle identification, ground speed, vertical rate and track angle. The purpose of this technology is to improve surveillance data accuracy and provide access to better situational awareness to enable operational benefits such as shorter routes, reduced flight time and fuel burn, and reduced traffic delays, and to allow air traffic controllers to manage aircraft with greater safety margins. Other than the limited amount of information bits per packet that can be sent, ADS-B's other hard-limit limitation is capacity. Small unmanned aircraft systems (sUAS) can utilize limited ADS-B transmission power, in general, thus allowing this technology to be considered for use within a combined NAS and sUAS environment, but the potential number and density of sUAS predicted for future deployment calls into question the ability of ADS-B systems to meet the resulting capacity requirement. Hence, studies to understand potential limitations of ADS-B to fulfill capacity requirements in various sUAS scenarios are of great interest. In this paper we, validate/improve on, previous work performed by the MITRE Corporation concerning sUAS power and capacity in a sUAS and General Aviation (GA) mixed environment. In addition, we implement its inherent media access control layer capacity limitations which was not shown in the MITRE paper. Finally, a simple detect and avoid (DAA) algorithm is implemented to display that ADS-B technology is a viable technology for a mixed NAS/sUAS environment even in proposed larger mixed density environments.

Matheou, Konstantin J.↗
NASA NTRS2018

ADS-B Mixed sUAS and NAS System Capacity Analysis and DAA Performance

Automatic Dependent Surveillance-Broadcast (ADS-B) technology was introduced more than twenty years ago to improve surveillance within the US National Airspace Space (NAS) as well as in many other countries. Via the NextGen initiative, implementation of ADS-B technology across the US is planned in stages between 2012 and 2025. ADS-B's automatic one second epoch packet transmission exploits on-board GPS-derived navigational information to provide position information, as well as other information including vehicle identification, ground speed, vertical rate and track angle. The purpose of this technology is to improve surveillance data accuracy and provide access to better situational awareness to enable operational benefits such as shorter routes, reduced flight time and fuel burn, and reduced traffic delays, and to allow air traffic controllers to manage aircraft with greater safety margins. Other than the limited amount of information bits per packet that can be sent, ADS-B's other hard-limit limitation is capacity. Small unmanned aircraft systems (sUAS) can utilize limited ADS-B transmission power, in general, thus allowing this technology to be considered for use within a combined NAS and sUAS environment, but the potential number and density of sUAS predicted for future deployment calls into question the ability of ADS-B systems to meet the resulting capacity requirement. Hence, studies to understand potential limitations of ADS-B to fulfill capacity requirements in various sUAS scenarios are of great interest. In this paper we, validate/improve on, previous work performed by the MITRE Corporation concerning sUAS power and capacity in a sUAS and General Aviation (GA) mixed environment. In addition, we implement its inherent media access control layer capacity limitations which was not shown in the MITRE paper. Finally, a simple detect and avoid (DAA) algorithm is implemented to display that ADS-B technology is a viable technology for a mixed NAS/sUAS environment even in proposed larger mixed density environments.

Matheou, Konstantin↗
NASA NTRS2018

A Component-Level Model of Automatic Dependent Surveillance - Broadcast (ADS-B)

Automatic Dependent Surveillance – Broadcast (ADS-B) is being employed in numerous peer-to-peer initiatives attempting to expand the capacity of the National Airspace System (NAS) or enable mixed operations of manned and unmanned vehicles. Safety assessments of these initiatives rely, in part, on modeling the accuracy of ADS-B in reporting the position and direction of an ownship and surrounding traffic. Frequently, these initiatives utilize a position uncertainty model that applies a reported ADS-B estimation position uncertainty (EPU) value to a Rayleigh distribution and uses a Gauss-Markov random walk to add error to the ADS-B output of a vehicle. This model of ADS-B state error is easy to implement and apply to numerous problems. However, it has a couple of draw-backs. First, the ADS-B state errors are equally probable in all directions. This is a good assumption in situations where aircraft maneuvering is not constrained. However, in situations where the aircraft maneuvering is constrained such as landing, the error distribution is likely to exhibit directionality and the non-directional model may skew results especially when assessing very low probabilities (e.g., 10(exp -9)) of catastrophic encounters. Second, the model does not account for processing latency in the receiving aircraft. NASA Langley Research Center (LaRC) recently examined the feasibility of decreasing the spacing of aircraft on parallel approaches to runways separated by as little as 700 feet. For Monte-Carlo analysis using a high-fidelity simulation of a large transport, LaRC started with a Gauss-Markov model of ADS-B error but then developed a component level model of ADS-B error to increase the fidelity of results.

Madden, Michael M.↗
NASA NTRS2017

B-plane Evolution Under Highly Non-Keplerian Dynamics

Juno is the second of a series of New Frontiers missions and was launched in 2011. The spacecraft was set en route to Jupiter, and its Jupiter Orbit Insertion occurred on 2016-07-04 after a five-year cruise in deep space. The mission phase just prior to this large maneuver is called approach. As navigation team, we were responsible for precise orbit determination of the Juno spacecraft to ensure a successful orbit insertion. To evaluate the navigation performance we employed the B-plane mapping, where the incoming hyperbolic velocity defines the plane perpendicular to it, and the time to go to hit the plane will directly map into the uncertainties of the target point. The B-plane is a convenient tool when assessing the navigation performance as it is not affected by non-linearities due to the gravitational pull of the targeted body. However, as the Jupiter Orbit Insertion approached we started to realize that the B-plane mapping uncertainties were significantly larger than expected. We found that the B-plane mapping time had tremendous influence on the covariance inflation in the B-plane. Because of the close approach distance during the Jupiter Orbit Insertion and the strong interaction with J2 spherical harmonic coefficient, the Juno dynamics were too far from a Keplerian one assumed for the B-plane mapping. We first discuss the analytical approach of the B-plane mapping uncertainty and perform a numerical analysis to isolate the components of the Juno dynamics that cause the B-plane covariance inflation.

Bordi, John↗
NASA NTRS1985

Configuration of the high-latitude thermosphere neutral circulation for IMF B(y) negative and positive

Asymmetries in the Northern Hemisphere neutral circulation that are dependent on the sign of the east-west 'B(y)' component of the IMF are presently illustrated by measurements of the neutral wind in the polar F-region which were conducted by the DE-2 spacecraft. The data thus obtained are categorized according to the sign of the hourly averaged IMF B(y) component measured by ISEE-3 for the hour preceding the DE-2 measurements. It is noted that there is (1) an asymmetry in the polar cap neutral flow velocity, with the region of most rapid antisunward flow shifting from the dawn side to the dusk side of the polar cap as B(y) changes from positive to negative; (2) a shift occurs in the magnetic local time of the region of entry of neutral gas into the polar cap, from a location on the dawn side of the moon-midnight meridian for B(y) positive to one more biased, for B(y) negative; and (3) there is an enhancement of velocities associated with the dawn anticlockwise neutral vortex for B(y) negative relative to those observed for B(y) positive.

Mccormac, F. G.↗
NASA NTRS2003

The promotive effect of latrunculin B on maize root gravitropism is concentration dependent

The cytoskeleton has been proposed to be a key player in the gravitropic response of higher plants. A major approach to determine the role of the cytoskeleton in gravitropism has been to use inhibitors to disrupt the cytoskeleton and then to observe the effect that such disruption has on organ bending. Several investigators have reported that actin or microtubule inhibitors do not prevent root gravitropism, leading to the conclusion that the cytoskeleton is not involved in this process. However, there are recent reports showing that disruption of the actin cytoskeleton with the actin inhibitor, latrunculin B, promotes the gravitropic response of both roots and shoots. In roots, curvature is sustained during prolonged periods of clinorotation despite short periods of gravistimulation. These results indicate that an early gravity-induced signal continues to persist despite withdrawal of the constant gravity stimulus. To investigate further the mechanisms underlying the promotive effect of actin disruption on root gravitropism, we treated maize roots with varying concentrations of latrunculin B in order to determine the lowest concentration of latrunculin B that has an effect on root bending. After a 10-minute gravistimulus, treated roots were axially rotated on a one rpm clinostat and curvature was measured after 15 hours. Our results show that 100 nM latrunculin B induced the strongest promotive effect on the curvature of maize roots grown on a clinostat. Moreover, continuously gravistimulated roots treated with 100 nM latrunculin B exhibited stronger curvature responses while decapped roots treated with this concentration of latrunculin B did not bend during continuous gravistimulation. The stronger promotive effect of low concentrations of latrunculin B on the curvature of both clinorotated and continuously gravistimulated roots suggests that disruption of the finer, more dynamic component of the actin cytoskeleton could be the cause of the enhanced tropic responses of roots to gravity. c2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

Non-NASA Center↗
NASA NTRS2016

The Habitability of Proxima Centauri b: I. Irradiation, Rotation and Volatile Inventory From Formation to the Present

Proxima b is a planet with a minimum mass of 1.3 M(sub ⨁) orbiting within the habitable zone (HZ) of Proxima Centauri, a very low-mass, active star and the Sun’s closest neighbor. Here we investigate a number of factors related to the potential habitability of Proxima b and its ability to maintain liquid water on its surface. We set the stage by estimating the current high-energy irradiance of the planet and show that the planet currently receives 30 times more extreme-UV radiation than Earth and 250 times more X-rays. We compute the time evolution of the star’s spectrum, which is essential for modeling the flux received over Proxima b’s lifetime. We also show that Proxima b’s obliquity is likely null, and its spin is either synchronous or in a 3:2 spin-orbit resonance, depending on the planet’s eccentricity and level of triaxiality. Next, we consider the evolution of Proxima b’s water inventory. We use our spectral energy distribution to compute the hydrogen loss from the planet with an improved energy-limited escape formalism. Despite the high level of stellar activity, we find that Proxima b is likely to have lost less than an Earth ocean’s worth of hydrogen (EO(sub H)) before it reached the HZ 100–200 Myr after its formation. The largest uncertainty in our work is the initial water budget, which is not constrained by planet formation models. We conclude that Proxima b is a viable candidate habitable planet.

Proxima Cen↗
NASA NTRS1975

Preliminary study of oxide-dispersion-strengthened B-1900 prepared by mechanical alloys

An experimental oxide dispersion strengthened (ODS) alloy based on the B-1900 composition was produced by the mechanical alloying process. Without optimization of the processing for the alloy or the alloy for the processing, recrystallization of the extruded product to large elongated grains was achieved. Materials having grain length-width ratios of 3 and 5.5 were tested in tension and stress-rupture. The ODS B-1900 exhibited tensile strength similar to that of cast B-1900. Its stress-rupture life was lower than that of cast B-1900 at 760 C. At 1095 C the ODS B-1900 with the higher grain length-width ratio (5.5) had stress-rupture life superior to that of cast B-1900. It was concluded that, with optimization, oxide dispersion strengthening of B-1900 and other complex cast nickel-base alloys has potential for improving high temperature properties over those of the cast alloy counterparts.

Glasgow, T. K.↗
NASA NTRS1981

Protective mechanisms and acclimation to solar ultraviolet-B radiation in Oenothera stricta

Plant adaptations ameliorating or repairing the damaging effects of ultraviolet-B (UV-B) radiation on plant tissue were investigated. The degree of phenotype plasticity in UV protective mechanisms and acclimation in relation to the natural solar UV-B radiation flux and in an enhanced UV-B irradiance environment was also examined. Mechanisms by which plants avoid radiation, adaptations altering the path of radiation incident on the leaf, and repair processes were considered. Attenuation of UV-B by tissues, UV-B irradiation into the leaf, and the effects of UV-B on photosynthesis were investigated.

Robberecht, R.↗
NASA NTRS1985

External calibration of SIR-B imagery with area-extended and point targets

Data-takes on two ascending orbits of the Shuttle Imaging Radar-B (SIR-B) over an agricultural test site in west-central Illinois were used to establish end-to-end transfer functions for conversion of the digital numbers on the 8-bit image to values of the radar backscattering coefficient sigma sup 0 (sq m/sq. m) in dB. The transfer function for each data-take was defined by the SIR-B response to an array of six calibrated point targets of known radar cross-section (transponders) and to a large number of area-extended targets also with known radar cross-section as measured by externally calibrated, truck-mounted scatterometers. The radar cross-section of each transponder at the SIR-B center frequency was measured on an antenna range as a function of local angle of incidence. Two truck-mounted scatterometers observed 20 to 80 agricultural fields daily at 1.6 GHz with HH polarization and at azimuth viewing angles and incidence angles equivalent to those of the SIR-B. The form of the transfer function is completely defined by the SIR-B receiver and the incoherent averaging procedure incorporated into production of the standard SIR-B image product.

Dobson, M. C.↗
NASA NTRS1993

31 Cygni: The B star and the wind

I have followed photospheric and wind absorptions in International Ultraviolet Explorer (IUE) spectra over much of the orbit of this K4 Ib+B3-4 binary system, using interstellar lines to transform all the velocities to a scale with the interstellar medium at -10.1 km/s. Results are as follows: Interstellar Fe II lines give NL (Fe(+)) = 1-2 x 10(exp 14)/sq cm with a Doppler width of 7 km/s; depletions of heavy elements along the line of sight to this star are similar to those for other stars with low interstellar densities. Photospheric lines yield a new velocity amplitude for the B star, K(sub B) = 23.2 +/- 1.0 km/s, which gives the mass ratio M(sub K)/M(sub B) = 1.66 and masses M(sub B) = 7.1 solar mass and M(sub K) = 11.7 solar mass. Existing photometry gives R(sub K) = 197 solar radius, R(sub B) = 5.2 solar radius, and i = 87.19 deg. Breadths of photospheric lines imply the rotational velocity of the B star is V sin i = 70-80 km/s. Most of the wind features are formed in a shell much larger than the binary system for which the terminal velocity seems to be 73 +/- 2 km/s, but it may be as high as approximately 90 km/s. The Doppler width (approximately 13 km/s) of Fe II shell lines likely results from acceleration of the wind, although it could reflect orbital motion of the K supergiant. Shell lines of Mg II and Si II are roughly consistent with Fe II, although their strengths are phase dependent, while S II requires a somewhat thicker shell in S(+) than in Fe(+) with a greater spread in expansion velocity. Shell lines of O I and N I are abnormally weak, if detected at all, and this implies that hydrogen is ionized throughout much of the wind. Lines of highly ionized species (C IV, Si Iv, and N V) appear sporadically in the spectrum and have inverse P Cyg profiles implying collapse (probably of an accretion disk) onto the B star. They do not seem to be isolated at particular phases as might be expected for formation in a conical shock front around an accretion column. I argue that the wind is roughly isotopic and is accelerated slowly, in agreement with existing ideas about winds.

Eaton, Joel A.↗
NASA NTRS1981

Theoretical Treatment of the X(sup 1)Sigma(sup +), A(sup 1)Sigma(sup +), and B(sup 1)Pi states of LiH

Ab initio self-consistent-field plus configuration-interaction calculations are reported for the X(sup 1)Sigma(sup +), A(sup 1)Sigma(sup +), and B(sup 1)Pi states of LiH using a 22(sugma)12(pi)7(delta) function Slater basis set. The resulting dissociation energies, with the experimental values in parentheses, are D(sub e)(X(sup 1)Sigma(sup +)) = 19 972 (20288)/ cm, and D(sub e)(A(sup 1)Sigma(sup +)) = 9042 (8682)/ cm, and D(sup e)(B(sup 1)Pi) = 284 (288) /cm. This is the first ab initio treatment to quantitatively account for the binding in the B(sup 1)Pi state. Calculated dipole moments and electronic transition moments for the X(sup 1)Sigma(sup+)-A(sup 1)Sigma(sup +), X(sup 1)Sigma(sup +)-B((sup 1)Pi, and A(sup 1)Sigma(sup +)- B(sup 1)PI band systems are in excellent agreement with existing theoretical and experimental data. Radiative transition probabilities and lifetimes, including both the bound-bound and bound-free contributions, are computed for all vibrational levels of the A(sup 1)Sigma(sup+) and B(sup 1)Pi states. Comparison with previous results using experimentally based potentials provides insight into the sensitivity of the radiative lifetimes to the detailed nature of the uppermost region of the potentials. Our calculated lifetimes for the lower vibrational levels of the A(sup 1)Sigma(sup +) state are within the experimental uncertainty. Our calculated lifetimes for the three vibrational levels of the B(sup 1)Pi state are in excellent agreement with those of Zemke and Stwalley (values in parentheses), increasing with (upsilon)' from 11.3 (11.3) nsec at (upsilon)' = 0, to 17.0 (17.0) nsec at (upsilon)' = 1, and then to 23.5 (24.0) nsec at (upsilon)' = 2.

Partridge, Harry↗
NASA NTRS2010

The Roles of Tidal Evolution and Evaporative Mass Loss in the Origin of CoRoT-7 b

CoRoT-7 b is the first confirmed rocky exoplanet, but, with an orbital semimajor axis of 0.0172 au, its origins may be unlike any rocky planet in our Solar System. In this study, we consider the roles of tidal evolution and evaporative mass loss in CoRoT-7 b's history, which together have modified the planet's mass and orbit. If CoRoT-7 b has always been a rocky body, evaporation may have driven off almost half its original mass, but the mass loss may depend sensitively on the extent of tidal decay of its orbit. As tides caused CoRoT-7 b's orbit to decay, they brought the planet closer to its host star, thereby enhancing the mass loss rate. Such a large mass loss also suggests the possibility that CoRoT-7 b began as a gas giant planet and had its original atmosphere completely evaporated. In this case, we find that CoRoT-7 b's original mass probably did not exceed 200 Earth masses (about two-third of a Jupiter mass). Tides raised on the host star by the planet may have significantly reduced the orbital semimajor axis, perhaps causing the planet to migrate through mean-motion resonances with the other planet in the system, CoRoT-7 c. The coupling between tidal evolution and mass loss may be important not only for CoRoT-7 b but also for other close-in exoplanets, and future studies of mass loss and orbital evolution may provide insight into the origin and fate of close-in planets, both rocky and gaseous.

Jackson, Brian↗
NASA NTRS2019

Explicit IMF B(sub y)-Effect Maximizes at Subauroral Latitudes (Dedicated to the Memory of Eigil Friis-Christensen)

The most important parameter in the coupling between solar wind and geomagnetic activity is the B(sub z)‐component of the interplanetary magnetic field (IMF). However, recent studies have shown that IMF B(sub y) is an additional, independent driver of geomagnetic activity. We use here local geomagnetic indices from a large network of magnetic stations to study how IMF B(sub y) affects geomagnetic activity at different latitudes for all solar wind and, separately, during coronal mass ejections. We show that geomagnetic activity, for all solar wind, is 20% stronger for B(sub y) > 0 than for B(sub y) < 0 at subauroral latitudes of about 60° corrected geomagnetic latitude. During coronal mass ejections, the B(sub y)‐effect is larger, about 40%, at slightly lower latitudes of about 57° (corrected geomagnetic) latitude. These results highlight the importance of the IMF B(sub y)‐component for space weather at different latitudes and must be taken into account in space weather modeling

Holappa, L.↗
NASA NTRS2020

Atmospheric Characterization and Further Orbital Modeling of κ Andromeda b

We present κ Andromeda b's photometry and astrometry taken with Subaru/SCExAO+HiCIAO and Keck/NIRC2, combined with recently published SCExAO/CHARIS low-resolution spectroscopy and published thermal infrared photometry to further constrain the companion's atmospheric properties and orbit. The Y/Y−K colors of κ And b are redder than field dwarfs, consistent with its youth and lower gravity. Empirical comparisons of its Y-band photometry and CHARIS spectrum to a large spectral library of isolated field dwarfs reaffirm the conclusion from Currie et al. that it likely has a low gravity but admit a wider range of most plausible spectral types (L0–L2). Our gravitational classification also suggests that the best-fit objects for κ And b may have lower gravity than those previously reported. Atmospheric models lacking dust/clouds fail to reproduce its entire 1–4.7 μm spectral energy distribution (SED), and cloudy atmosphere models with temperatures of ~1700–2000 K better match κ And b data. Most well-fitting model comparisons favor 1700–1900 K, a surface gravity of log(g) ~ 4–4.5, and a radius of 1.3–1.6 R (sub Jup); the best-fit model (Drift-Phoenix) yields the coolest and lowest-gravity values: T (sub eff) = 1700 K and log g = 4.0. An update to κ And b's orbit with ExoSOFT using new astrometry spanning 7 yr reaffirms its high eccentricity (0.77 ± 0.08). We consider a scenario where unseen companions are responsible for scattering κ And b to a wide separation and high eccentricity. If three planets, including κ And b, were born with coplanar orbits, and one of them was ejected by gravitational scattering, a potential inner companion with mass ≲10 M (sub Jup) could be located at ≲25 au.

Exoplanet astronomy↗
NASA NTRS2024

SOLES XII. The Aligned Orbit of TOI-2533 b, a Transiting Brown Dwarf Orbiting an F8-type Star

Brown dwarfs occupy a middle ground in mass space between gaseous giant planets and ultracool dwarf stars, and the characterisation of their orbital orientations may shed light on how these neighbouring objects form. We present an analysis of the Rossiter–McLaughlin effect across the transit of TOI-2533 b, a brown dwarf on a moderately eccentric (e b = 0.2476 ± 0.0090) and wide-separation (a b /R ⋆ = 13.34 ± 0.30) orbit around an F8-type star, using data from the NEID/WIYN spectrograph in combination with archival photometry and radial velocity observations. Spin-orbit analyses of brown dwarfs are relatively rare, and TOI-2533 stands out as the fifth brown dwarf system with a measured spin–orbit constraint. We derive a sky-projected stellar obliquity of λ = −7° ± 14° for TOI-2533 b, finding that the brown dwarf is consistent with spin–orbit alignment. Our joint model also indicates that TOI-2533 b falls near the lower bound of the hydrogen-burning minimum mass range (M b = 74.9 ± 5.3 M Jup ). Ultimately, we find that TOI-2533 b is consistent with formation from disc fragmentation in a primordially spin–orbit aligned orientation, although we cannot rule out the possibility that the system has been tidally realigned during its lifetime.

Thiago Ferreira dos Santos↗
NASA NTRS1979

Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars

This paper discusses effective temperatures, angular diameters, distances, and linear diameters that have been determined for 160 O and B stars on the basis of published UV spectrophotometry, visible and near-IR intermediate-band photometry, and model-atmosphere fluxes. The results are compared with previous measurements and calculations for main-sequence and giant O and B stars. It is found that: (1) the flux effective temperatures of O and B supergiants are systematically lower than those of main-sequence and giant stars of the same subtype; (2) the effective temperatures and radii of Beta Cep stars are the same as those of nonvariable stars of the same spectral type; (3) Be stars that do not have two Balmer jumps have effective temperatures very similar to those of normal B stars of the same subtype; (4) O and B stars increase in size from the main sequence to supergiants; and (5) late B supergiants are approximately twice as large as O9 supergiants.

Underhill, A. B.↗