In the glare of the Sun Sheppard, Scott S.
Science (American Association for the Advancement of Science),
07/2022, Letnik:
377, Številka:
6604
Journal Article
Recenzirano
Searches during twilight toward the Sun have found several asteroids near Venus’ orbit
Asteroid surveys generally operate at night, mostly finding objects beyond Earth’s orbit. This creates a blind ...spot because many near-Earth objects (NEOs) could be lurking in the sunlight interior to Earth’s orbit. New telescopic surveys are braving the Sun’s glare and searching for asteroids toward the Sun during twilight. These surveys have found many previously undiscovered asteroids interior to Earth, including the first asteroid with an orbit interior to Venus, ’Ayló’chaxnim (2020 AV2), and an asteroid with the shortest-known orbital period around the Sun, 2021 PH27 (
1
,
2
).
The observable Solar System can be divided into three distinct regions: the rocky terrestrial planets including the asteroids at 0.39 to 4.2 astronomical units (AU) from the Sun (where 1 AU is the ...mean distance between Earth and the Sun), the gas giant planets at 5 to 30 AU from the Sun, and the icy Kuiper belt objects at 30 to 50 AU from the Sun. The 1,000-kilometre-diameter dwarf planet Sedna was discovered ten years ago and was unique in that its closest approach to the Sun (perihelion) is 76 AU, far greater than that of any other Solar System body. Formation models indicate that Sedna could be a link between the Kuiper belt objects and the hypothesized outer Oort cloud at around 10,000 AU from the Sun. Here we report the presence of a second Sedna-like object, 2012 VP113, whose perihelion is 80 AU. The detection of 2012 VP113 confirms that Sedna is not an isolated object; instead, both bodies may be members of the inner Oort cloud, whose objects could outnumber all other dynamically stable populations in the Solar System.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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 ∼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 (∼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.
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, , 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° from Planet X's longitude of perihelion, keeping 2015 TG387 antialigned with Planet X over the age of the solar system.
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 JL80, 2014 ...JO80, and 2014 JQ80) 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 ∼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 ∼50% of the small Plutinos are potential contact binaries.
The optical colors of 58 objects in mean motion resonance with Neptune were obtained. The various Neptune resonant populations were found to have significantly different surface color distributions. ...The different color distributions of objects in mean motion resonance with Neptune are likely a result from the disruption of the primordial Kuiper Belt from the scattering and migration of the giant planets. The few low-inclination objects known in the outer 2:1 and 5:2 resonances are mostly only moderately red. This suggests if the 2:1 and 5:2 have a cold low-inclination component, the objects likely had a significantly different origin than the ultra-red-dominated cold components of the cold classical belt and 5:3 and 7:4 resonances.
Extreme outer solar system objects have possible origins beyond the Kuiper Belt edge, high inclinations, very large semimajor axes, or large perihelion distances. Thirty-three such objects were ...observed in this work to determine their optical colors. All three objects that have been dynamically linked to the inner Oort Cloud by various authors ((90377) Sedna, 2006 SQ372, and (87269) 2000 OO67) were found to have ultra-red surface material (spectral gradient, S ~ 25). Ultra-red material is generally associated with rich organics and the low inclination 'cold' classical Kuiper Belt objects (KBOs). The observations detailed here show that very red material may be a more general feature for objects kept far from the Sun. The recently discovered retrograde outer solar system objects (2008 KV42 and 2008 YB3) and the high inclination object (127546) 2002 XU93 show only moderately red surfaces (S ~ 9) very similar to known comets, suspected dead comets, Jupiter and Neptune Trojans, irregular satellites, D-type asteroids, and damocloids. The extended or detached disk objects, which have large perihelion distances and are thus considered to be detached from the influence of the giant planets but yet have large eccentricities, are found to have mostly moderately red colors (10 S 18). The colors of the detached disk objects, including the dynamically unusual 2004 XR190 and (148209) 2000 CR105, are similar to the scattered disk and Plutino populations. Thus the detached disk, scattered disk, Plutino, and high inclination 'hot' classical objects likely have a similar mix of objects from the same source regions. Outer classical KBOs, including (48639) 1995 TL8, were found to have very red surfaces (18 S 30). The low inclination 'cold' classical KBOs, outer classical KBOs and possibly the inner Oort Cloud appear to be dominated by ultra-red objects (S 25) and thus do not likely have a similar mix of objects as the other outer solar system reservoirs such as the scattered disk, detached disk, and Trojan populations. A possible trend was found for the detached disk and outer classical Kuiper Belt in that objects with smaller eccentricities have redder surfaces irrespective of inclinations or perihelion distances. There is also a clear trend that objects more distant appear redder.
ABSTRACT Recently, Sheppard et al. presented the discovery of seven new trans-Neptunian objects with moderate eccentricities, perihelia beyond 40 au, and semimajor axes beyond 50 au. Like the few ...previously known objects on similar orbits, these objects' semimajor axes are just beyond the Kuiper Belt edge and clustered around Neptunian mean motion resonances (MMRs). These objects likely obtained their observed orbits while trapped within MMRs, when the Kozai-Lidov mechanism raised their perihelia and weakened Neptune's dynamical influence. Using numerical simulations that model the production of this population, we find that high-perihelion objects near Neptunian MMRs can constrain the nature and timescale of Neptune's past orbital migration. In particular, the population near the 3:1 MMR (near 62 au) is especially useful due to its large population and short dynamical evolution timescale. If Neptune finishes migrating within ∼100 Myr or less, we predict that over 90% of high-perihelion objects near the 3:1 MMR will have semimajor axes within 1 au of each other, very near the modern resonance's center. On the other hand, if Neptune's migration takes ∼300 Myr, we expect ∼50% of this population to reside in dynamically fossilized orbits over ∼1 au closer to the Sun than the modern resonance. We highlight 2015 KH162 as a likely member of this fossilized 3:1 population. Under any plausible migration scenario, nearly all high-perihelion objects in resonances beyond the 4:1 MMR (near 76 au) reach their orbits well after Neptune stops migrating and compose a recently generated, dynamically active population.
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.
ABSTRACT We report a new active asteroid in the main belt of asteroids between Mars and Jupiter. Object (62412) 2000 SY178 exhibited a tail in images collected during our survey for objects beyond ...the Kuiper Belt using the Dark Energy Camera on the CTIO 4 m telescope. We obtained broadband colors of 62412 at the Magellan Telescope, which, along with 62412ʼs low albedo, suggests it is a C-type asteroid. 62412ʼs orbital dynamics and color strongly correlate with the Hygiea family in the outer main belt, making it the first active asteroid known in this heavily populated family. We also find 62412 to have a very short rotation period of 3.33 0.01 hours from a double-peaked light curve with a maximum peak-to-peak amplitude of 0.45 0.01 mag. We identify 62412 as the fastest known rotator of the Hygiea family and the nearby Themis family of similar composition, which contains several known main belt comets. The activity on 62412 was seen over one year after perihelion passage in its 5.6 year orbit. 62412 has the highest perihelion and one of the most circular orbits known for any active asteroid. The observed activity is probably linked to 62412ʼs rapid rotation, which is near the critical period for break-up. The fast spin rate may also change the shape and shift material around 62412ʼs surface, possibly exposing buried ice. Assuming 62412 is a strengthless rubble pile, we find the density of 62412 to be around 1500 kg m−3.
PDF
