The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere and collect spectra of %10 6 galaxies, 100,000 quasars, 30,000 stars, and 30,000 serendipity targets. In 2001 June, the SDSS released to the general astronomical community its early data release, roughly 462 deg 2 of imaging data including almost 14 million detected objects and 54,008 follow-up spectra. The imaging data were collected in drift-scan mode in five bandpasses (u, g, r, i, and z); our 95% completeness limits for stars are 22.0, 22.2, 22.2, 21.3, and 20.5, respectively. The photometric calibration is reproducible to 5%, 3%, 3%, 3%, and 5%, respectively. The spectra are flux-and wavelength-calibrated, with 4096 pixels from 3800 to 9200 Å at R % 1800. We present the means by which these data are distributed to the astronomical community, descriptions of the hardware used to obtain the data, the software used for processing the data, the measured quantities for each observed object, and an overview of the properties of this data set.

We discuss measurements of the properties of ∼10,000 asteroids detected in 500 deg 2 of sky in the Sloan Digital Sky Survey (SDSS) commissioning data. The moving objects are detected in the magnitude range 14 < r * < 21.5, with a baseline of ∼5 minutes, resulting in typical velocity errors of ∼3%. Extensive tests show that the sample is at least 98% complete, with the contamination rate of less than 3%.We find that the size distribution of asteroids resembles a broken power-law, independent of the heliocentric distance: D −2.3 for 0.4 km ∼ < D ∼ < 5 km, and D −4 for 5 km ∼ < D ∼ < 40 km. As a consequence of this break, the number of 1 Based on observations obtained with the Sloan Digital Sky Survey.-3asteroids with r * < 21.5 is ten times smaller than predicted by extrapolating the power-law relation observed for brighter asteroids (r * ∼ < 18). The observed counts imply that there are about 530,000 objects with D > 1 km in the asteroid belt, or about four times less than previous estimates. We predict that by its completion SDSS will obtain about 100,000 near simultaneous five-band measurements for a subset drawn from 280,000 asteroids brighter than r * < 21.5 at opposition. Only about a third of these asteroids have been previously observed, and usually in just one band.The distribution of main belt asteroids in the 4-dimensional SDSS color space is bimodal, and the two groups can be associated with S (rocky) and C (carbonaceous) asteroids. A strong bimodality is also seen in the heliocentric distribution of asteroids and suggests the existence of two distinct belts: the inner rocky belt, about 1 AU wide (FWHM) and centered at R ∼2.8 AU, and the outer carbonaceous belt, about 0.5 AU wide and centered at R ∼3.2 AU. The median color of each class becomes bluer by about 0.03 mag AU −1 as the heliocentric distance increases. The observed number ratio of S and C asteroids in a sample with r * < 21.5 is 1.5:1, while in a sample limited by absolute magnitude it changes from 4:1 at 2 AU, to 1:3 at 3.5 AU. In a size-limited sample with D > 1 km, the number ratio of S and C asteroids in the entire main belt is 1:2.3.The colors of Hungarias, Mars crossers, and near-Earth objects, selected by their velocity vectors, are more similar to the C-type than to S-type asteroids, suggesting that they originate in the outer belt. In about 100 deg 2 of sky along the Celestial Equator observed twice two days apart, we find one plausible Kuiper Belt Object (KBO) candidate, in agreement with the expected KBO surface density. The colors of the KBO candidate are significantly redder than the asteroid colors, in agreement with colors of known KBOs. We explore the possibility that SDSS data can be used to search for very red, previously uncatalogued asteroids observed by 2MASS, by extracting objects without SDSS counterparts. We do not find evidence for a significant population of such objects; their contribution is no more than 10% of the asteroid population.

We discuss optical colors of 10,592 asteroids with known orbits selected from a sample of 58,000 moving objects observed by the Sloan Digital Sky Survey (SDSS). This is more than ten times larger sample that includes both orbital parameters and multi-band photometric measurements than previously available. We confirm that asteroid dynamical families, defined as clusters in orbital parameter space, also strongly segregate in color space. In particular, we demonstrate that the three major asteroid families (Eos, Koronis, and Themis), together with the Vesta family, represent four main asteroid color types. Their distinctive optical colors indicate that the variations in chemical composition within a family are much smaller than the compositional differences between families, and strongly support earlier suggestions that asteroids belonging to a particular family have a common origin. We estimate that over 90% of asteroids belong to families.Comment: 18 pages, color figures, accepted by A

We investigate the distribution of mass M and orbital period P of extrasolar planets, taking account of selection effects caused by the limited velocity precision and duration of existing surveys. We fit the data on 72 planets to a power-law distribution of the form dn = C M −α P −β (dM/M)(dP/P), and find α = 0.11 ± 0.10, β = −0.27 ± 0.06 for M 10 M J , where M J is the mass of Jupiter. The correlation coefficient between these two exponents is −0.31, indicating that uncertainties in the two distributions are coupled. We estimate that 4 per cent of solar-type stars have companions in the range 1 M J < M < 10 M J , 2 d < P < 10 yr.

Habitability is usually defined as the requirement for a terrestrial planet's atmosphere to sustain liquid water. This definition can be complemented by the dynamical requirement that other planets in the system do not gravitationally perturb terrestrial planets outside of their habitable zone, the orbital region allowing the existence of liquid water. We quantify the dynamical habitability of 85 known extrasolar planetary systems via simulations of their orbital dynamics in the presence of potentially habitable terrestrial planets. When requiring that habitable planets remain strictly within their habitable zone at all times, the perturbing influence of giant planets extends beyond the traditional Hill sphere for close encounters: terrestrial planet excursions outside of the habitable zone are also caused by secular eccentricity variations and, in some cases, strong mean-motion resonances. Our results indicate that more than half the known extrasolar planetary systems (mostly those with distant, eccentric giant planets) are unlikely to harbor habitable terrestrial planets. About one-fourth of the systems (mostly those with close-in giant planets), including one-third of the potential targets for the Terrestrial Planet Finder, appear as dynamically habitable as our own solar system. The influence of yet undetected giant planets in these systems could compromise their dynamical habitability. Some habitable terrestrial planets in our simulations have substantial eccentricities (e > 0:1), which may lead to large seasonal climate variations and thus affect their habitability.

One of the parameters fitted by Doppler radial velocity measurements of extrasolar planetary systems is ω, the argument of pericenter of a given planet's orbit referenced to the plane of the sky. Curiously, the ω's of the outer two planets orbiting Upsilon Andromedae are presently nearly identical:This observation is least surprising if planets C and D occupy orbits that are seen close to edge-on (sin i C , sin i D 0.5) and whose mutual inclination Θ does not exceed 20 • . In this case, planets C and D inhabit a secular resonance in which ∆ω librates about 0 • with an amplitude of ∼30 • and a period of ∼4 × 10 3 yr. The resonant configuration spends about one-third of its time with |∆ω| ≤ 10 • . If Θ 40 • , either ∆ω circulates or the system is unstable. This instability is driven by the Kozai mechanism which couples the eccentricity of planet C to Θ to drive the former quantity to values approaching unity. Our expectation that Θ 20 • suggests that planets C and D formed in a flattened, circumstellar disk, and may be tested by upcoming astrometric measurements with the FAME satellite.

Ensembles of in‐plane and inclined orbits in the vicinity of the Lagrange points of the terrestrial planets are integrated for up to 100 Myr. The integrations incorporate the gravitational effects of the Sun and the eight planets (Pluto is neglected). Mercury is the least promising planet, as it is unable to retain tadpole orbits over 100‐Myr time‐scales. Mercurian Trojans probably do not exist, although there is evidence for long‐lived, corotating horseshoe orbits with small inclinations. Both Venus and the Earth are much more promising, as they possess rich families of stable tadpole and horseshoe orbits. Our survey of Trojans in the orbital plane of Venus is undertaken for 25 Myr. Some 40 per cent of the survivors are on tadpole orbits. For the Earth, the integrations are pursued for 50 Myr. The stable zones in the orbital plane are larger for the Earth than for Venus, but fewer of the survivors (∼20 per cent) are tadpoles. Both Venus and the Earth also have regions in which inclined test particles can endure near the Lagrange points. For Venus, only test particles close to the orbital plane are stable. For the Earth, there are two bands of stability, one at low inclinations and one at moderate inclinations The inclined test particles that evade close encounters are primarily moving on tadpole orbits. Two Martian Trojans (5261 Eureka and 1998 VF31) have been discovered over the last decade and both have orbits moderately inclined to the ecliptic (203 and 313 respectively). Our survey of in‐plane test particles near the Martian Lagrange points shows no survivors after 60 Myr. Low‐inclination test particles do not persist, as their inclinations are quickly increased until the effects of a secular resonance with Jupiter cause destabilization. Numerical integrations of inclined test particles for time‐spans of 25 Myr show stable zones for inclinations between 14° and 40°. However, there is a strong linear resonance with Jupiter that destabilizes a narrow band of inclinations at ∼29°. Both 5261 Eureka and 1998 VF31 lie deep within the stable zones, which suggests that they may be of primordial origin.

We positionally correlate known asteroids with a sample of $18,000 asteroids detected by the Sloan Digital Sky Survey (SDSS). We find 2641 unique matches, which represent the largest sample of asteroids with both accurate multicolor photometry and known orbital parameters. The matched objects are predominantly bright and demonstrate that the SDSS photometric pipeline recovers $90% of the known asteroids in the observed region. For the recovered asteroids, we find a large offset ($0.4 mag) between Johnson V magnitudes derived from SDSS photometry and the predicted magnitudes. This offset varies with the asteroid color, from 0.34 mag for blue asteroids to 0.44 mag for red asteroids, and is probably caused by the use of unfiltered CCD observations in the majority of recent asteroid surveys. This systematic photometric error leads to an overestimate of the number of asteroids brighter than a given absolute magnitude limit by a factor of $1.7. The distribution of the matched asteroids in orbital parameter space indicates strong color segregation. We confirm that some families are dominated by a single asteroid type (e.g., the Koronis family by red asteroids and the Themis family by blue asteroids), while others appear to be a mixture of blue and red objects (e.g., the Nysa-Polana family). Asteroids with the bluest i*Àz* colors, which can be associated with the Vesta family, show particularly striking localization in orbital parameter space.