We show that 'Oumuamua's excited spin could be in a high-energy long axis mode (LAM) state, which implies that its shape could be far from the highly elongated shape found in previous studies. CLEAN and ANOVA algorithms are used to analyze 'Oumuamua's lightcurve using 818 observations over 29.3. days. Two fundamental periodicities are found at frequencies (2.77 +/- 0.11) and (6.42 +/- 0.18). cycles/day, corresponding to (8.67 +/- 0.34) hr and (3.74 +/- 0.11) hr, respectively. The phased data show that the lightcurve does not repeat in a simple manner, but approximately shows a double minimum at 2.77. cycles/day and a single minimum at 6.42. cycles/day. 'Oumuamua could be spinning in either the LAM or short axis mode (SAM). For both, the long axis precesses around the total angular momentum vector with an average period of (8.67 +/- 0.34) hr. For the three LAMs we have found, the possible rotation periods around the long axis are 6.58, 13.15, or 54.48 hr, with 54.48 hr being the most likely. 'Oumuamua may also be nutating with respective periods of half of these values. We have also found two possible SAM states where 'Oumuamua oscillates around the long axis with possible periods at 13.15 and 54.48 hr. In this case any nutation occurs with the same periods. Determination of the spin state, the amplitude of the nutation, the direction of the total angular momentum vector (TAMV), and the average total spin period may be possible with a direct model fit to the lightcurve. We find that 'Oumuamua is "cigar-shaped," if close to its lowest rotational energy, and an extremely oblate spheroid if close to its highest energy state.

We identify new Y- and T-type brown dwarfs from the WISE All Sky data release using images obtained in filters that divide the traditional near-infrared H and J bands into two halves-specifically CH(4)s and CH(4)l in the H and J2, and J3 in the J. This proves to be very effective at identifying cool brown dwarfs via the detection of their methane absorption, as well as providing preliminary classification using methane colors and WISE -to-near-infrared colors. New and updated calibrations between T/Y spectral types and CH(4)s-CH(4)l J3-W2, and CH(4)s-W2 colors are derived, producing classification estimates good to a few spectral sub-types. We present photometry for a large sample of T and Y dwarfs in these filters, together with spectroscopy for 23 new ultra-cool dwarfs-2 Y dwarfs and 21 T dwarfs. We identify a further 8 new cool brown dwarfs, which we have high confidence are T dwarfs based on their methane photometry. We find that, for objects observed on a 4 m class telescope at J-band magnitudes of similar to 20 or brighter, CH(4)s-CH(4)l is the more powerful color for detecting objects and then estimating spectral types. Due to the lower sky background in the J-band, the J3 and J2 bands are more useful for identifying fainter cool dwarfs at J greater than or similar to 22. The J3-J2 color is poor at estimating spectral types. But fortunately, once J3-J2 confirms that an object is a cool dwarf, the J3-W2 color is very effective at estimating approximate spectral types.

We observed 12 Plutinos over two separated years with the 4.3 m Lowell's Discovery Channel Telescope. Here, we present the first light-curve data for those objects. Three of them (2014 JL(80), 2014 JO(80), and 2014 JQ(80)) display a large light-curve amplitude explainable by a single elongated object, but they are most likely caused by a contact binary system due to their light-curve morphology. These potential contact binaries have rotational periods from 6.3 to 34.9 hr and peak-to-peak light-curve variability between 0.6 and 0.8 mag. We present partial light curves, allowing us to constrain the light-curve amplitude and the rotational period of another nine Plutinos. By merging our data with the literature, we estimate that up to similar to 40% of the Plutinos could be contact binaries. Interestingly, we found that all of the suspected contact binaries in the 3:2 resonance are small with absolute magnitude H > 6 mag. Based on our sample and the literature, up to similar to 50% of the small Plutinos are potential contact binaries.

Active asteroids behave dynamically like asteroids but display comet-like comae. These objects are poorly understood, with only about 30 identified to date. We have conducted one of the deepest systematic searches for asteroid activity by making use of deep images from the Dark Energy Camera (DECam) ideally suited to the task. We looked for activity indicators among 11,703 unique asteroids extracted from 35,640 images. We detected three previously identified active asteroids ((62412), (1) Ceres and (779) Nina), though only (62412) showed signs of activity. Our activity occurrence rate of 1 in 11,703 is consistent with the prevailing 1 in 10,000 activity occurrence rate estimate. Our proof of concept demonstrates (1) our novel informatics approach can locate active asteroids and (2) DECam data are well-suited to the search for active asteroids.

We report observations of the reactivations of the main-belt comets (MBCs) 238P/Read and 288P/(300163) 2006 VW139 that also track the evolution of each object's activity over several months in 2016 and 2017. We additionally identify and analyze archival SDSS data showing 288P to have been active in 2000, meaning that both 238P and 288P have now each been confirmed to be active near perihelion on three separate occasions. From data obtained of 288P from 2012-2015 when it appeared inactive, we find best-fit R-band H, G phase function parameters of H-R = 16.80 +/- 0.12 mag and G(R) = 0.18 +/- 0.11, corresponding to effective component radii of r(c) = 0.80 +/- 0.04 km, assuming a binary system with equally sized components. Fitting linear functions to ejected dust masses inferred for 238P and 288P soon after their observed reactivations in 2016, we find an initial average net dust production rate of M-d = 0.7. 0.3 kg. s(-1) and a best-fit start date of 2016 March 11 (when the object was at a true anomaly of nu = -63 degrees) for 238P, and an initial average net dust production rate of M-d = 5.6. 0.7 kg s(-1) and a best-fit start date of 2016 August 5 (when the object was at nu = -27 degrees) for 288P. Applying similar analyses to archival data, we find similar start points for previous active episodes for both objects, suggesting that minimal mantle growth or ice recession occurred between the active episodes in question. Some changes in dust production rates between active episodes are detected, however. More detailed dust modeling is suggested to further clarify the process of activity evolution in MBCs.

We present observations of main-belt comet (MBC) 358P/PANSTARRS (P/2012 T1) obtained using the Gemini South telescope from 2017 July to December, as the object approached perihelion for the first time since its discovery. We find best-fit IAU phase function parameters of H-R = 19.5 +/- 0.2 mag and G(R) = -0.22 +/- 0.13 for the nucleus, corresponding to an effective radius of r(N) 0.32 +/- 0.03 km (assuming an albedo of p(R) 0.05). The object appears significantly brighter (by >= 1 mag) than expected starting in 2017 November, while a faint dust tail oriented approximately in the antisolar direction is also observed on 2017 December 18. We conclude that 358P has become active again for the first time since its previously observed active period in 2012-2013. These observations make 358P the seventh MBC candidate confirmed to exhibit recurrent activity near perihelion with intervening inactivity away from perihelion, strongly indicating that its activity is sublimation-driven. Fitting a linear function to the ejected dust masses inferred for 358P in 2017 when it is apparently active, we find an average net dust production rate of M = 2.0 +/- 0.6 kg s(-1) (assuming a mean effective particle radius of a(d) = 1 mm) and an estimated activity start date of 2017 November 8 +/- 4 when the object was at a true anomaly of v= 316 degrees +/- 1 degrees and a heliocentric distance of R=2.54 au. Insufficient data is currently available to ascertain whether activity strength has changed between the object's 2012-2013 and 2017 active periods. Further observations are therefore highly encouraged during the object's upcoming observing window (2018 August through 2019 May).

2013 FY27 is the ninth intrinsically brightest Trans-Neptunian Object (TNO). We used ALMA at thermal wavelengths and Magellan in the optical to determine 2013 FY27's size and albedo for the first time and compare it to other dwarf planets. We found 2013 FY27 has a geometric albedo of p(v) = 0.17(-0.030)(+0.0451) and effective diameter of D = 765(+)(85)(+80)km. This puts 2013 FY27 in the transition region between the largest TNOs that have higher albedos and densities than smaller TNOs. No short-term light curve was found, with variations <0.06 +/- 0.02 mag over hours and days. The Sloan colors of 2013 FY27 are g-r = 0.76 +/- 0.02 and r-i = 0.31 +/- 0.03 mag, giving a moderately red color. This is different than the neutral or ultra-red colors found for the 10 largest TNOs, making 2013 FY27 one of the largest moderately red TNOs, which are only seen, and in abundance, at diameters less than 800 km. This suggests something different might be associated with TNOs larger than 800 km. Moderately red colors might indicate old or ice-poor surfaces with TNOs larger than 800 km having fresher or more volatile-rich surfaces. TNOs larger than 800 km could be more differentiated, giving them different surface compositions. A satellite at 0 '' 17 and 3.0 +/- 0.2 mag fainter than 2013 FY27 was found through Hubble Space Telescope observations. Almost all the largest TNOs have satellites, which now includes 2013 FY27. Assuming a similar albedo, the satellite is similar to 186 km in diameter, making the primary D = 742(-)(83)(+78)km.

Inner Oort cloud objects (IOCs) are trans-Plutonian for their entire orbits. They are beyond the strong gravitational influences of the known planets, yet close enough to the Sun that outside forces are minimal. Here we report the discovery of the third known IOC after Sedna and 2012 VP113, called 2015 TG387. This object has a perihelion of 65 +/- 1 au and semimajor axis of 1170 +/- 70 au. The longitude of perihelion angle, (w) over bar, for 2015 TG387 is between that of Sedna and 2012 VP113 and thus similar to the main group of clustered extreme trans-Neptunian objects (ETNOs), which may be shepherded into similar orbital angles by an unknown massive distant planet called Planet X, or Planet Nine. The orbit of 2015 TG387 is stable over the age of the solar system from the known planets and Galactic tide. When including outside stellar encounters over 4 Gyr, 2015 TG387's orbit is usually stable, but its dynamical evolution depends on the stellar encounter scenarios used. Surprisingly, when including a massive Planet X beyond a few hundred au on an eccentric orbit that is antialigned in longitude of perihelion with most of the known ETNOs, we find that 2015 TG387 is typically stable for Planet X orbits that render the other ETNOs stable as well. Notably, 2015 TG387's argument of perihelion is constrained, and its longitude of perihelion librates about 180 degrees from Planet X's longitude of perihelion, keeping 2015 TG387 antialigned with Planet X over the age of the solar system.

We present a survey of the rotational and physical properties of the dynamically low inclination Cold Classical (CC) trans-Neptunian objects (TNOs). The CCs are primordial planetesimals and contain information about our solar system and planet formation over the first 100 million years after the Sun's formation. We obtained partial/ complete light curves for 42 CCs. We use statistical tests to derive general properties about the shape and rotational frequency distributions of the CCs and infer that they have slower rotations and are more elongated/deformed than the other TNOs. On the basis of the full light curves, the mean rotational period of the CCs is 9.48 +/- 1.53 hr compared to 8.45 +/- 0.58 hr for the rest of the TNOs. About 65% of the TNOs have a light-curve amplitude below 0.2 mag compared to the 36% of CCs with small amplitude. We present the full light curve of one likely contact binary, 2004 VC131, with a potential density of 1 g cm(-3) for a mass ratio of 0.4. We have hints that 2004 MU8 and 2004 VU75 are perhaps potential contact binaries, on the basis of their sparse light curves, but more data are needed to confirm this finding. Assuming equal-sized binaries, we find that similar to 10%-25% of the CCs could be contact binaries, suggesting a deficit of contact binaries in this population compared to previous estimates and to the (similar to 40%-50%) possible contact binaries in the Plutino population. These estimates are lower limits and may increase if nonequal-sized contact binaries are considered. Finally, we put in context the results of the New Horizons flyby of 2014 MU69.

The g'r'i' colors of seven likely and potential contact binaries in the Kuiper Belt were acquired with the Magellan-Baade telescope and combined with colors from the literature to understand contact binary surfaces. The likely and potential contact binaries discovered in the dynamically cold classical population display very red/ultra-red colors. Such colors are common in this sub-population and imply that the cold classical contact binaries were formed in situ. The likely contact binaries found in several mean motion resonances with Neptune have colors from moderately to ultra-red, suggesting different formation regions. Among the nine contact binaries discovered in resonances, five have very red/ultra-red colors and four have moderately red surfaces. Based on the very red/ultra-red colors and low to moderate inclinations of the contact binaries in resonances, these contact binaries are possibly escaped dynamically cold classicals that are now trapped in resonances. Moderately red surfaces are common in diverse sub-populations of the Kuiper Belt, thus pinpointing their origin is difficult though they are most likely captured objects that formed in the giant planet area. Finally, for the contact binary population we report an anti-correlation between inclination and g'-r', as noticed in the rest of this belt. We also find hints of trends between eccentricity, perihelion distance, rotational period, and g'-r', but as we are still dealing with a limited sample, additional data are required to confirm them.