Kuiper Belt Object MakeMake has a Moon

Peering to the outskirts of our solar system, NASA's Hubble Space Telescope has spotted a small, dark moon orbiting Makemake, the second brightest icy dwarf planet -- after Pluto -- in the Kuiper Belt.

The moon -- provisionally designated S/2015 (136472) 1 and nicknamed MK 2 -- is more than 1,300 times fainter than Makemake. MK 2 was seen approximately 13,000 miles from the dwarf planet, and its diameter is estimated to be 100 miles across. Makemake is 870 miles wide. The dwarf planet, discovered in 2005, is named for a creation deity of the Rapa Nui people of Easter Island.

The Kuiper Belt is a vast reservoir of leftover frozen material from the construction of our solar system 4.5 billion years ago and home to several dwarf planets. Some of these worlds have known satellites, but this is the first discovery of a companion object to Makemake. Makemake is one of five dwarf planets recognized by the International Astronomical Union.

The observations were made in April 2015 with Hubble's Wide Field Camera 3. Hubble's unique ability to see faint objects near bright ones, together with its sharp resolution, allowed astronomers to pluck out the moon from Makemake's glare. The discovery was announced today in a Minor Planet Electronic Circular.

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Spectral Variation on Kuiper Belt Objects

The Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System: Spectral Variation on Kuiper Belt Objects

Authors:

Fraser et al

Abstract:

Here we present additional photometry of targets observed as part of the Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System. 12 targets were re-observed with the Wide Field Camera 3 in optical and NIR wavebands designed to compliment those used during the first visit. Additionally, all observations originally presented by Fraser and Brown (2012) were reanalyzed through the same updated photometry pipeline. A reanalysis of the optical and NIR colour distribution reveals a bifurcated optical colour distribution and only two identifiable spectral classes, each of which occupies a broad range of colours and have correlated optical and NIR colours, in agreement with our previous findings. We report the detection of significant spectral variations on 5 targets which cannot be attributed to photometry errors, cosmic rays, point spread function or sensitivity variations, or other image artifacts capable of explaining the magnitude of the variation. The spectrally variable objects are found to have a broad range of dynamical classes, absolute magnitudes, exhibit a broad range of apparent magnitude variations, and are found in both compositional classes. The spectrally variable objects with sufficiently accurate colours for spectral classification maintain their membership, belonging to the same class at both epochs. 2005 TV189 exhibits a sufficiently broad difference in colour at the two epochs that span the full range of colours of the neutral class. This strongly argues that the neutral class is one single class with a broad range of colours, rather than the combination of multiple overlapping classes.

Hubble Observations of Titan's Atmosphere

HST observations of the limb polarization of Titan

Authors:

Bazzon et al

Abstract:

Titan is an excellent test case for detailed studies of the scattering polarization from thick hazy atmospheres. We present the first limb polarization measurements of Titan, which are compared as a test to our limb polarization models. Previously unpublished imaging polarimetry from the HST archive is presented which resolves the disk of Titan. We determine flux-weighted averages of the limb polarization and radial limb polarization profiles, and investigate the degradation and cancelation effects in the polarization signal due to the limited spatial resolution of our observations. Taking this into account we derive corrected values for the limb polarization in Titan. The results are compared with limb polarization models, using atmosphere and haze scattering parameters from the literature.

In the wavelength bands between 250 nm and 2000 nm a strong limb polarization of about 2-7 % is detected with a position angle perpendicular to the limb. The fractional polarization is highest around 1 micron. As a first approximation, the polarization seems to be equally strong along the entire limb. The detected polarization is compatible with expectations from previous polarimetric observations taken with Voyager 2, Pioneer 11, and the Huygens probe.

Our results indicate that ground-based monitoring measurements of the limb-polarization of Titan could be useful for investigating local haze properties and the impact of short-term and seasonal variations of the hazy atmosphere of Titan. Planets with hazy atmospheres similar to Titan are particularly good candidates for detection with the polarimetric mode of the upcoming planet finder instrument at the VLT. Therefore, a good knowledge of the polarization properties of Titan is also important for the search and investigation of extra-solar planets.

Potential Kuiper Belt Targets for New Horizons: 2011 JY31, 2011 HZ102, and 2013 LU35

New Horizons: Long-Range Kuiper Belt Targets Observed by the Hubble Space Telescope

Authors:

Benecchi et al

Abstract:

We report on Hubble Space Telescope (HST) observations of three Kuiper Belt Objects (KBOs), discovered in our dedicated ground-based search campaign, that are candidates for long-range observations from the New Horizons spacecraft: 2011 JY31, 2011 HZ102, and 2013 LU35. Astrometry with HST enables both current and future critical accuracy improvements for orbit precision, required for possible New Horizons observations, beyond what can be obtained from the ground. Photometric colors of all three objects are red, typical of the Cold Classical dynamical population within which they reside; they are also the faintest KBOs to have had their colors measured. None are observed to be binary with HST above separations of ~0.02 arcsec (~700 km at 44 AU) and {\Delta}m less than or equal to 0.5.

New Horizons Space Probe has a Crisis

Nearly 4.3 billion kilometres from Earth, and most of the way to Pluto, NASA’s New Horizons spacecraft is in danger of missing out on half of its mission. Project managers face a looming deadline to identify an icy object in the outer Solar System for the probe to fly by after it passes Pluto.

A visit to a Kuiper belt object, or KBO, was always meant to be a key part of New Horizons’ US$700-million journey, which began in 2006. But there is only a slim chance that astronomers will find a suitable KBO with their current strategy of using ground-based telescopes — and securing time on the orbiting Hubble Space Telescope is far from guaranteed.

New Horizons will fly past Pluto in July 2015. Soon afterwards, it must fire its engines and set itself on course to fly past a selected KBO. Project scientists must identify a KBO in the next several months if they are to determine the necessary trajectory well enough for New Horizons to aim accurately and meet its target.

“They’re running out of time,” says Mark Sykes, director of the Planetary Science Institute in Tucson, Arizona, who is not involved in the mission. “We’re not just talking about science being lost — we’re talking about getting return on our investment.”

New Horizons scientists have asked for 160 orbits’ worth of observing time on the hugely oversubscribed Hubble. It is a rare request for a NASA mission already in operation. The committee that allocates Hubble time will make a decision by 13 June.

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Centaur Chiron, Haumea & Another Kuiper Belt Object Observed in the Ultraviolet by Hubble Space Telescope

FIRST ULTRAVIOLET REFLECTANCE MEASUREMENTS OF SEVERAL KUIPER BELT OBJECTS, KUIPER BELT OBJECT SATELLITES, AND NEW ULTRAVIOLET MEASUREMENTS OF A CENTAUR

Authors:

Stern et al

Abstract:

We observed the 2600-3200 Å (hereafter, mid-UV) reflectance of two Kuiper Belt Objects (KBOs), two KBO satellites, and a Centaur, using the Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS). Other than measurements of the Pluto system, these constitute the first UV measurements obtained of KBOs, and KBO satellites, and new HST UV measurements of the Centaur 2060 Chiron. We find significant differences among these objects, constrain the sizes and densities of Haumea's satellites, and report the detection of a possible spectral absorption band in Haumea's spectrum near 3050 Å. Comparisons of these objects to previously published UV reflectance measurements of Pluto and Charon are also made here.

First Observance of an Asteroid Disintegrating

Disintegrating Asteroid P/2013 R3

Authors:

Jewitt et al

Abstract:

Splitting of the nuclei of comets into multiple components has been frequently observed but, to date, no main-belt asteroid has been observed to break-up. Using the Hubble Space Telescope, we find that main-belt asteroid P/2013 R3 consists of 10 or more distinct components, the largest up to 200 m in radius (assumed geometric albedo of 0.05) each of which produces a coma and comet-like dust tail. A diffuse debris cloud with total mass roughly 2x10^8 kg further envelopes the entire system. The velocity dispersion among the components is about V = 0.2 to 0.5 m/s, is comparable to the gravitational escape speeds of the largest members, while their extrapolated plane-of-sky motions suggest break-up between February and September 2013. The broadband optical colors are those of a C-type asteroid. We find no spectral evidence for gaseous emission, placing model-dependent upper limits to the water production rate near 1 kg/s. Breakup may be due to a rotationally induced structural failure of the precursor body.

Comet 133P/Elst-Pizarro Studied

Hubble Space Telescope Investigation of Main-Belt Comet 133P/Elst-Pizarro

Authors:

Jewitt et al

Abstract:

We report new observations of the prototype main-belt comet (active asteroid) 133P/Elst-Pizarro taken at high angular resolution using the Hubble Space Telescope. The object has three main components; a) a point-like nucleus, b) a long, narrow antisolar dust tail and c) a short, sunward anti-tail. There is no resolved coma. The nucleus has a mean absolute magnitude H_V = 15.70+/-0.10 and a lightcurve range 0.42 mag., the latter corresponding to projected dimensions 3.6 x 5.4 km (axis ratio 1.5:1), at the previously measured geometric albedo of 0.05+/-0.02. We explored a range of continuous and impulsive emission models to simultaneously fit the measured surface brightness profile, width and position angle of the antisolar tail. Preferred fits invoke protracted emission, over a period of 150 days or less, of dust grains following a differential power-law size distribution with index 3.25 less than q less than 3.5 and having a wide range of sizes. Ultra-low surface brightness dust projected in the sunward direction is a remnant from emission activity occurring in previous orbits, and consists of the largest (less than cm-sized) particles. Ejection velocities of one micron-sized particles are comparable to the ~1.8 m/s gravitational escape speed of the nucleus, while larger particles are released at speeds less than the gravitational escape velocity. The observations are consistent with, but do not prove, a hybrid hypothesis in which mass loss is driven by gas drag from the sublimation of near-surface water ice, but escape is aided by centripetal acceleration from the rotation of the elongated nucleus. No plausible alternative hypothesis has been identified.

Europa has Eruptive Water Jets Like Enceladus

NASA’s Hubble Space Telescope has observed water vapor above the frigid south polar region of Jupiter's moon Europa, providing the first strong evidence of water plumes erupting off the moon's surface.

Previous scientific findings from other sources already point to the existence of an ocean located under Europa's icy crust. Researchers are not yet fully certain whether the detected water vapor is generated by erupting water plumes on the surface, but they are confident this is the most likely explanation.

Should further observations support the finding, this would make Europa the second moon in the solar system known to have water vapor plumes. The findings are being published in the Dec. 12 online issue of Science Express, and reported at the meeting of the American Geophysical Union in San Francisco.

“By far the simplest explanation for this water vapor is that it erupted from plumes on the surface of Europa,” said lead author Lorenz Roth of Southwest Research Institute in San Antonio. "If those plumes are connected with the subsurface water ocean we are confident exists under Europa's crust, then this means that future investigations can directly investigate the chemical makeup of Europa's potentially habitable environment without drilling through layers of ice. And that is tremendously exciting."

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Water Signature Seen For Three Exoplanets

EXOPLANET TRANSIT SPECTROSCOPY USING WFC3: WASP-12 b, WASP-17 b, AND WASP-19 b

Authors:

Mandell et al

Abstract:

We report an analysis of transit spectroscopy of the extrasolar planets WASP-12 b, WASP-17 b, and WASP-19 b using the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). We analyze the data for a single transit for each planet using a strategy similar, in certain aspects, to the techniques used by Berta et al., but we extend their methodology to allow us to correct for channel- or wavelength-dependent instrumental effects by utilizing the band-integrated time series and measurements of the drift of the spectrum on the detector over time. We achieve almost photon-limited results for individual spectral bins, but the uncertainties in the transit depth for the band-integrated data are exacerbated by the uneven sampling of the light curve imposed by the orbital phasing of HST's observations. Our final transit spectra for all three objects are consistent with the presence of a broad absorption feature at 1.4 μm most likely due to water. However, the amplitude of the absorption is less than that expected based on previous observations with Spitzer, possibly due to hazes absorbing in the NIR or non-solar compositions. The degeneracy of models with different compositions and temperature structures combined with the low amplitude of any features in the data preclude our ability to place unambiguous constraints on the atmospheric composition without additional observations with WFC3 to improve the signal-to-noise ratio and/or a comprehensive multi-wavelength analysis.

Hubble Finds Evidence of Asteroids Crashing into White Dwarves in Ancient Stellar Clusters

The stars, known as white dwarfs — small, dim remnants of stars once like the Sun — reside 150 light-years away in the Hyades star cluster, in the constellation of Taurus (The Bull). The cluster is relatively young, at only 625 million years old.

Astronomers believe that all stars formed in clusters. However, searches for planets in these clusters have not been fruitful — of the roughly 800 exoplanets known, only four are known to orbit stars in clusters. This scarcity may be due to the nature of the cluster stars, which are young and active, producing stellar flares and other outbursts that make it difficult to study them in detail.

A new study led by Jay Farihi of the University of Cambridge, UK, instead observed "retired" cluster stars to hunt for signs of planet formation [1].

Hubble's spectroscopic observations identified silicon in the atmospheres of two white dwarfs, a major ingredient of the rocky material that forms Earth and other terrestrial planets in the Solar System. This silicon may have come from asteroids that were shredded by the white dwarfs' gravity when they veered too close to the stars. The rocky debris likely formed a ring around the dead stars, which then funnelled the material inwards.

The debris detected whirling around the white dwarfs suggests that terrestrial planets formed when these stars were born. After the stars collapsed to form white dwarfs, surviving gas giant planets may have gravitationally nudged members of any leftover asteroid belts into star-grazing orbits [2].

"We have identified chemical evidence for the building blocks of rocky planets," says Farihi. "When these stars were born, they built planets, and there's a good chance that they currently retain some of them. The signs of rocky debris we are seeing are evidence of this — it is at least as rocky as the most primitive terrestrial bodies in our Solar System."

Besides finding silicon in the Hyades stars' atmospheres, Hubble also detected low levels of carbon. This is another sign of the rocky nature of the debris, as astronomers know that carbon levels should be very low in rocky, Earth-like material. Finding its faint chemical signature required Hubble's powerful Cosmic Origins Spectrograph (COS), as carbon's fingerprints can be detected only in ultraviolet light, which cannot be observed from ground-based telescopes.

"The one thing the white dwarf pollution technique gives us that we won't get with any other planet detection technique is the chemistry of solid planets," Farihi says. "Based on the silicon-to-carbon ratio in our study, for example, we can actually say that this material is basically Earth-like."

This new study suggests that asteroids less than 160 kilometres across [3] were gravitationally torn apart by the white dwarfs' strong tidal forces, before eventually falling onto the dead stars [4].

The team plans to analyse more white dwarfs using the same technique to identify not only the rocks' composition, but also their parent bodies. "The beauty of this technique is that whatever the Universe is doing, we'll be able to measure it," Farihi said. "We have been using the Solar System as a kind of map, but we don't know what the rest of the Universe does. Hopefully with Hubble and its powerful ultraviolet-light spectrograph COS, and with the upcoming ground-based 30- and 40-metre telescopes, we'll be able to tell more of the story."

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Notes

1] The two "polluted" Hyades white dwarfs are part of a search of planetary debris around more than 100 white dwarfs, led by Boris Gänsicke of the University of Warwick, United Kingdom. Using computer models of white dwarf atmospheres, Detlev Koester from the University of Kiel in Germany is determining the abundances of various elements that can be traced to planets in the COS data.

[2] Seeing evidence of asteroids points to the possibility of Earth-sized planets in the same system. Asteroids are the building blocks of major planets. Planet-forming processes are inefficient, and spawn many times more small bodies than large bodies — but once rocky embryos the size of asteroids are built, planets are sure to follow.

[3] The team estimated the size of the infalling asteroids by measuring the amount of dust being gobbled up by the stars — about 10 million grams per second, equal to the flow rate of a small river. They then compared that data with measurements of material falling onto other white dwarfs.

[4] The Hyades study offers insight into what will happen in the Solar System when the Sun burns out, five billion years from now.

Fomalhaut b, Rogue Planet in 2000 Year Orbit, Brings Doom in 2032

Newly released Hubble Space Telescope images of a vast debris disk encircling the nearby star Fomalhaut, and of a mysterious planet circling it, may provide forensic evidence of a titanic planetary disruption in the system.

Astronomers are surprised to find that the debris belt is wider than previously known, spanning a gulf of space from 14 billion miles to nearly 20 billion miles from the star. Even more surprisingly, the latest Hubble images have allowed a team of astronomers to calculate that the planet follows an unusual elliptical orbit that carries it on a potentially destructive path through the vast dust ring.

The planet, called Fomalhaut b, swings as close to its star as 4.6 billion miles, and the outermost point of its orbit is 27 billion miles away from the star. The orbit was re-calculated from the newest Hubble observation made in 2012. "We are shocked — Fomalhaut b probably passed three times closer to the star than we previously thought, and now it is zipping outward," said Paul Kalas of the University of California at Berkeley and the SETI Institute in Mountain View, Calif.

The Fomalhaut team led by Kalas considers this circumstantial evidence that there may be other planet-like bodies in the system that gravitationally disturbed Fomalhaut b to place it in such a highly eccentric orbit.

His team is presenting their finding on January 8 at the 221st meeting of the American Astronomical Society in Long Beach, Calif.

Among several scenarios to explain Fomalhaut b's 2,000-year-long orbit is the hypothesis that an as yet undiscovered planet gravitationally ejected Fomalhaut b from a position closer to the star, and sent it flying into an orbit that extends beyond the dust belt. "Hot Jupiters get tossed through scattering events, where one planet goes in and one gets thrown out. This could be the planet that gets thrown out," according to co-investigator Mark Clampin of NASA's Goddard Space Flight Center in Greenbelt, Md.

Hubble also found that the dust and ice belt encircling Fomalhaut (the star) has an apparent gap slicing across the belt. This might have been carved out by another undetected planet, researchers said. "Hubble's exquisite view of the dust belt shows irregularities that strongly motivate a search for other planets in the system," Kalas said.

"If its orbit lies in the same plane with the dust belt, then Fomalhaut b will intersect the belt around 2032 on the outbound leg of its orbit. During the crossing, icy and rocky debris in the belt could crash into the planet's atmosphere and create the type of cosmic fireworks seen when comet Shoemaker-Levy 9 crashed into Jupiter," Kalas said. "But if Fomalhaut b is not co-planar with the belt, we may not see anything at all except for a gradual dimming of Fomalhaut b as it travels farther and farther from the star," he explained.

Kalas hypothesized that Fomalhaut b's extreme orbit is a major clue in explaining why the planet is unusually bright in visible light but very dim in infrared light. The planet could be between the mass of Pluto and Jupiter, but the optical brightness possibly originates from a ring or shroud of dust around the planet, reflecting starlight. The dust is rapidly produced by satellites orbiting the planet, which suffer extreme erosion by impacts and gravitational stirring when Fomalhaut b enters into the planetary system after a millennium of deep freeze beyond the main belt. "An analogy can be found by looking at Saturn, which has a tenuous but very large dust ring produced when meteoroids hit the outer moon called Phoebe," Kalas said.

The team has also considered a different scenario where a hypothetical second dwarf planet suffered a catastrophic collision with Fomalhaut b. Kalas explained, "The collision scenario would provide a solution as to why Fomalhaut (the star) has a narrow outer belt linked to an extreme planet. But in this case the belt is young, less than 10,000 years old, and it is difficult to produce energetic collisions far from the star in such young systems."

Stunning Hubble Pic