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News Article | January 20, 2016
Site: www.nature.com

A century after observatory founder Percival Lowell speculated that a ‘Planet X’ lurks at the fringes of the Solar System, astronomers say that they have the best evidence yet for such a world. They call it Planet Nine. Orbital calculations suggest that Planet Nine, if it exists, is about ten times the mass of Earth and swings an elliptical path around the Sun once every 10,000–20,000 years. It would never get closer than about 200 times the Earth–Sun distance, or 200 astronomical units (au). That range would put it far beyond Pluto, in the realm of icy bodies known as the Kuiper belt. No one has seen Planet Nine, but researchers have inferred its existence from the way several other Kuiper belt objects (KBOs) move. And given the history of speculation about distant planets (see ‘Solving for X’), Planet Nine may end up in the dustbin of good ideas gone wrong. “If I read this paper out of the blue, my first reaction would be that it was crazy,” says Mike Brown, an astronomer at the California Institute of Technology in Pasadena who was part of the research team. “But if you look at the evidence and statistics, it’s very hard to come away with any other conclusion.” Brown and his colleague Konstantin Batygin propose Planet Nine in a paper published on 20 January in the Astronomical Journal (K. Batygin and M. E. Brown Astronom. J. 151, 22; 2016). Alessandro Morbidelli, an orbital-dynamics specialist at the University of the Côte d’Azur in Nice, France, who has reviewed the paper in detail, says he is “quite convinced” that the planet exists. Others are not so sure. “I have seen many, many such claims in my career,” says Hal Levison, a planetary scientist at the Southwest Research Institute in Boulder, Colorado. “And all of them have been wrong.” Claims of Planet Nine’s existence recall a period in the nineteenth century when astronomers predicted and then discovered Neptune by studying tiny perturbations in the orbit of Uranus. The gravity of some unseen body must be tugging on Uranus, they said — and they were right. “In some sense we’re hoping to relive history a little bit,” says Batygin. The story of Planet Nine began in 2014, when a pair of astronomers reported finding a KBO called 2012 VP . Its stretched-out orbit never came closer than 80 au to the Sun (C. A. Trujillo and S. S. Sheppard Nature 507, 471–474; 2014). (Pluto, at its most distant, is 48 au from the Sun.) VP joined the dwarf planet Sedna as only the second known object with a very distant orbit. In their report, Chadwick Trujillo at the Gemini Observatory in Hilo, Hawaii, and Scott Sheppard of the Carnegie Institution for Science in Washington DC said that the orbits of these objects suggested that yet another object, a planet bigger than Earth, could exist at around 250 au (see ‘Far afield’). Batygin and Brown picked up the challenge. “Our main goal at that point was to show that this idea is crazy,” says Brown. But Trujillo and Sheppard had noted that Sedna, VP , and several other KBOs all shared a peculiar property: their closest approach to the Sun lay in the plane of the Solar System, and they all moved from south to north when crossing that plane. Batygin and Brown analysed the orbits further and discovered that their long axes were physically aligned, too, as if something had nudged them to occupy the same region of space around the Sun. The team concluded that a massive object must be shepherding the objects. “We have a gravitational signature of a giant planet in the outer Solar System,” Batygin says. Planet Nine — informally known as Phattie — is probably smaller than Neptune and icy with a gassy outer layer. The gravitational effect of Uranus and Neptune would have flung it outward in the first 3 million years of the Solar System’s existence, Batygin says. Actually spotting Planet Nine through a telescope could be difficult because it would spend most of its time very far from the Sun, making it faint and hard to see, notes Meg Schwamb, an astronomer at the Academia Sinica in Taipei. Brown and Batygin have been looking for it using the Subaru telescope in Hawaii, so far without success. The Large Synoptic Survey Telescope in Chile will have a good chance of catching it when it starts operating early next decade, Brown says. But he and Batygin say that there are other ways to test the existence of Planet Nine. Its gravitational influence would also produce a population of KBOs with orbits at steeply inclined angles. A few of these have already been spotted, but discovering more would strengthen the statistics of the discovery and help to clarify whether Planet Nine really exists or not, says David Nesvorny, a planetary scientist at the Southwest Research Institute. So it’s back to the telescopes. “It really points to the fact that more extreme KBOs need to be found,” says Trujillo. “The location is not known well enough to just point a telescope at it and say, ‘there it is’.”


News Article | February 27, 2017
Site: phys.org

Published today in Nature Astronomy and funded by the Science and Technology Facilities Council and the European Research Council, the study finds the remains of shattered asteroids orbiting a double sun consisting of a white dwarf and a brown dwarf roughly 1000 light-years away in a system called SDSS 1557. The discovery is remarkable because the debris appears to be rocky and suggests that terrestrial planets like Tatooine - Luke Skywalker's home world in Star Wars - might exist in the system. To date, all exoplanets discovered in orbit around double stars are gas giants, similar to Jupiter, and are thought to form in the icy regions of their systems. In contrast to the carbon-rich icy material found in other double star systems, the planetary material identified in the SDSS 1557 system has a high metal content, including silicon and magnesium. These elements were identified as the debris flowed from its orbit onto the surface of the star, polluting it temporarily with at least 1017 g (or 1.1 trillion US tons) of matter, equating it to an asteroid at least 4 km in size. Lead author, Dr Jay Farihi (UCL Physics & Astronomy), said: "Building rocky planets around two suns is a challenge because the gravity of both stars can push and pull tremendously, preventing bits of rock and dust from sticking together and growing into full-fledged planets. With the discovery of asteroid debris in the SDSS 1557 system, we see clear signatures of rocky planet assembly via large asteroids that formed, helping us understand how rocky exoplanets are made in double star systems." In the Solar System, the asteroid belt contains the leftover building blocks for the terrestrial planets Mercury, Venus, Earth, and Mars, so planetary scientists study the asteroids to gain a better understanding of how rocky, and potentially habitable planets are formed. The same approach was used by the team to study the SDSS 1557 system as any planets within it cannot yet be detected directly but the debris is spread in a large belt around the double stars, which is a much larger target for analysis. The discovery came as a complete surprise, as the team assumed the dusty white dwarf was a single star but co-author Dr Steven Parsons (University of Valparaíso and University of Sheffield), an expert in double star (or binary) systems noticed the tell-tale signs. "We know of thousands of binaries similar to SDSS 1557 but this is the first time we've seen asteroid debris and pollution. The brown dwarf was effectively hidden by the dust until we looked with the right instrument", added Parsons, "but when we observed SDSS 1557 in detail we recognised the brown dwarf's subtle gravitational pull on the white dwarf." The team studied the binary system and the chemical composition of the debris by measuring the absorption of different wavelengths of light or 'spectra', using the Gemini Observatory South telescope and the European Southern Observatory Very Large Telescope, both located in Chile. Co-author Professor Boris Gänsicke (University of Warwick) analysed these data and found they all told a consistent and compelling story. "Any metals we see in the white dwarf will disappear within a few weeks, and sink down into the interior, unless the debris is continuously flowing onto the star. We'll be looking at SDSS 1557 next with Hubble, to conclusively show the dust is made of rock rather than ice." Explore further: Dwarf star 200 light-years away contains life's building blocks


News Article | February 27, 2017
Site: www.eurekalert.org

Evidence of planetary debris surrounding a double sun, 'Tatooine-like' system has been found for the first time by a UCL-led team of researchers. Published today in Nature Astronomy and funded by the Science and Technology Facilities Council and the European Research Council, the study finds the remains of shattered asteroids orbiting a double sun consisting of a white dwarf and a brown dwarf roughly 1000 light-years away in a system called SDSS 1557. The discovery is remarkable because the debris appears to be rocky and suggests that terrestrial planets like Tatooine - Luke Skywalker's home world in Star Wars - might exist in the system. To date, all exoplanets discovered in orbit around double stars are gas giants, similar to Jupiter, and are thought to form in the icy regions of their systems. In contrast to the carbon-rich icy material found in other double star systems, the planetary material identified in the SDSS 1557 system has a high metal content, including silicon and magnesium. These elements were identified as the debris flowed from its orbit onto the surface of the star, polluting it temporarily with at least 1017 g (or 1.1 trillion US tons) of matter, equating it to an asteroid at least 4 km in size. Lead author, Dr Jay Farihi (UCL Physics & Astronomy), said: "Building rocky planets around two suns is a challenge because the gravity of both stars can push and pull tremendously, preventing bits of rock and dust from sticking together and growing into full-fledged planets. With the discovery of asteroid debris in the SDSS 1557 system, we see clear signatures of rocky planet assembly via large asteroids that formed, helping us understand how rocky exoplanets are made in double star systems." In the Solar System, the asteroid belt contains the leftover building blocks for the terrestrial planets Mercury, Venus, Earth, and Mars, so planetary scientists study the asteroids to gain a better understanding of how rocky, and potentially habitable planets are formed. The same approach was used by the team to study the SDSS 1557 system as any planets within it cannot yet be detected directly but the debris is spread in a large belt around the double stars, which is a much larger target for analysis. The discovery came as a complete surprise, as the team assumed the dusty white dwarf was a single star but co-author Dr Steven Parsons (University of Valparaíso and University of Sheffield), an expert in double star (or binary) systems noticed the tell-tale signs. "We know of thousands of binaries similar to SDSS 1557 but this is the first time we've seen asteroid debris and pollution. The brown dwarf was effectively hidden by the dust until we looked with the right instrument", added Parsons, "but when we observed SDSS 1557 in detail we recognised the brown dwarf's subtle gravitational pull on the white dwarf." The team studied the binary system and the chemical composition of the debris by measuring the absorption of different wavelengths of light or 'spectra', using the Gemini Observatory South telescope and the European Southern Observatory Very Large Telescope, both located in Chile. Co-author Professor Boris Gänsicke (University of Warwick) analysed these data and found they all told a consistent and compelling story. "Any metals we see in the white dwarf will disappear within a few weeks, and sink down into the interior, unless the debris is continuously flowing onto the star. We'll be looking at SDSS 1557 next with Hubble, to conclusively show the dust is made of rock rather than ice."


Top Scientific Minds You Probably Never Heard Of On Thursday, Aug. 25, scientists announced the discovery of a galaxy with the same mass as the Milky Way but contains 99.99 percent dark matter, which is an elusive and undetected substance. Known as Dragonfly 44, the newly identified galaxy was first detected through the Dragonfly Telephoto Array in Toronto. Afterward, scientists used the world's most powerful telescopes, the Gemini North telescope at the Gemini Observatory and the Keck II telescope at the W.M. Keck Observatory, to monitor it further. Although the galaxy is not the first to be identified with presence of dark matter, its discovery is special because it is the only average-sized galaxy nearly dominated by dark matter. Pieter van Dokkum, an astronomer from Yale University, says soon after the galaxy's discovery, they realized there was more to it than meets the eye. Dragonfly 44 is located about 300 million light-years away from our planet and is considered a dim galaxy with very few stars. According to van Dokkum, the dim galaxy has so few stars that it would be rapidly ripped apart unless it was being held together by something. Scientists believe the galaxy is likely made up of dark matter because the velocities of stars within it are much higher than what they had expected, indicating that it has a mass greater than what can be detected through telescopes. Furthermore, although Dragonfly 44 has the same mass as our own galaxy, it's actually the "Dark Twin" and is different from our galaxy by a factor of 100. How The Discovery Changes Everything The dim galaxy is such a novelty in the line of research that astrophysicists currently study. According to van Dokkum, the discovery of Dragonfly 44 challenges existing notions on the formation of galaxies. He says that prior to the research, they thought the ratio of dark matter was something they already understood. For instance, dark matter is thought to outnumber regular matter — ordinary matter composed by atoms — by 5 to 1 in the universe. Additionally, scientists thought the formation of stars was related to how much dark matter is present. However, Dragonfly 44 turns this last idea around. “It means we don’t understand, kind of fundamentally, how galaxy formation works," says van Dokkum. Meanwhile, the race to detect other galaxies similar to Dragonfly 44 is on. Because dark matter is believed to emit a faint ultraviolet signal, experts hope a neighboring galaxy with dark matter can provide the first evidence of the elusive substance's existence. Details of the report were published in the Astrophysical Journal Letters. © 2016 Tech Times, All rights reserved. Do not reproduce without permission.


Researchers now have evidence that rocky planets may be present in a Tatooine-like system with a double sun located about 1,000 light-years away. In a study funded by the European Research Council and the Science and Technology Facilities Council, researchers led by a team from the University College London reported the discovery of shattered asteroid remains moving around a double sun system known as SDSS 1557. As the debris appears to be made of rock, it suggests that planets of the same nature might be in existence in the system. So far, all exoplanets that have been discovered orbiting double sun systems were gas giants much like Jupiter, and were believed to have formed in their systems's icy regions. Unlike icy material rich in carbon found within other double sun systems, those identified in SDSS 1557 were highly metallic and included magnesium and silicon. The researchers were able to identify the elements when debris flowed onto one of the suns' surfaces, temporarily polluting it with matter the size of a minimum of 1.1 trillion U.S. tons. That's an area about as big as an asteroid that is at least 2.5 miles in size! According to Jay Farihi, the study's lead author, it's challenging for rocky planets to form in double sun systems because gravitational forces from the two (one white dwarf and one brown dwarf in the case of SDSS 1557) would result in constant and tremendously strong pushing and pulling that will prevent dust and rocks from sticking together. "With the discovery of asteroid debris in the SDSS 1557 system, we see clear signatures of rocky planet assembly via large asteroids that formed," he said. The solar system's asteroid belt features leftover building blocks from terrestrial planets such as Mars, Earth, Venus, and Mercury. To understand then how rocky, possibly habitable planets came to be, researchers turn to asteroids. This is the same approach used by Farihi and colleagues as no planet has been detected directly yet in SDSS 1557, no thanks to the widespread debris in the system. Discovering evidence of rocky planets in the system actually came as a surprise to the researchers because they initially thought SDSS 1557 was a single-sun system. Steven Parsons, a study co-author, was the one who noticed that they were actually looking at a double sun system. He explained that thousands of binary systems similar to SDSS 1557 are already known. However, this was the first time that pollution and debris from asteroids were observed in a system. All that pollution and debris hid the brown dwarf from sight until the right instrument was used to view SDSS 1557. To study the double sun system and its debris's chemical composition, the researchers used the European Southern Observatory Very Large Telescope and the Gemini Observatory South Telescope to measure differences in light wavelength absorption. When gathered data was analyzed, it yielded results that were compelling and consistent. To acquire conclusive proof that the dust swirling in SDSS 1557 is indeed rocky in nature and not icy, the researchers will be observing the system next using the Hubble telescope. © 2017 Tech Times, All rights reserved. Do not reproduce without permission.


Sheppard S.S.,Carnegie Institution of Washington | Trujillo C.A.,Gemini Observatory
Astrophysical Journal Letters | Year: 2010

We present an ultra-deep survey for Neptune Trojans using the Subaru 8.2 m and Magellan 6.5 m telescopes. The survey reached a 50% detection efficiency in the R band at mR = 25.7 mag and covered 49 deg2 of sky. mR = 25.7 mag corresponds to Neptune Trojans that are about 16 km in radius (assuming an albedo of 0.05). A paucity of smaller Neptune Trojans (radii < 45 km) compared with larger ones was found. The brightest Neptune Trojans appear to follow a steep power-law slope (q = 5 ± 1) similar to the brightest objects in the other known stable reservoirs such as the Kuiper Belt, Jupiter Trojans, and main belt asteroids.We find a roll-over for the Neptune Trojans that occurs around a radius of r = 45 ± 10 km (mR = 23.5 ± 0.3), which is also very similar to the other stable reservoirs. All the observed stable regions in the solar system show evidence for Missing Intermediate-Sized Planetesimals (MISPs). This indicates a primordial and not collisional origin, which suggests that planetesimal formation proceeded directly from small to large objects. The scarcity of intermediate- and smaller-sized Neptune Trojans may limit them as being a strong source for the short period comets. ©2010. The American Astronomical Society. All rights reserved.


Geballe T.R.,Gemini Observatory | Oka T.,University of Chicago
Astrophysical Journal Letters | Year: 2010

Until now, the known sources in the Galactic center with sufficiently smooth spectra and of sufficient brightness to be suitable for high-resolution infrared absorption spectroscopy of interstellar gas occupied a narrow range of longitudes, from the central cluster of hot stars to approximately 30 pc east of the center. In order to more fully characterize the gas within the r∼180 pc central molecular zone, it is necessary to find additional such sources that cover a much wider longitudinal range of sightlines. We are in the process of identifying luminous dust-embedded objects suitable for spectroscopy within 1.2 in longitude and 0.1 in latitude of Sgr A* using the Spitzer GLIMPSE and the Two Micron All Sky Survey catalogs. Here we present spectra of H+ 3 and CO toward two such objects, one located 140 pc west of Sgr A*, and the other located on a line of sight to the Sgr B molecular cloud complex 85 pc to the east of Sgr A*. The sightline to the west passes through two dense clouds of unusually high negative velocities and also appears to sample a portion of the expanding molecular ring. The spectra toward Sgr B reveal at least 10 absorption components covering over 200kms-1 and by far the largest equivalent width ever observed in an interstellar H + 3 line; they appear to provide the first near-infrared view into that hotbed of star formation. © 2010. The American Astronomical Society. All rights reserved..


Jorgensen I.,Gemini Observatory | Chiboucas K.,Gemini Observatory
Astronomical Journal | Year: 2013

We present an analysis of stellar populations and evolutionary history of galaxies in three similarly rich galaxy clusters MS0451.6-0305 (z = 0.54), RXJ0152.7-1357 (z = 0.83), and RXJ1226.9+3332 (z = 0.89). Our analysis is based on high signal-to-noise ground-based optical spectroscopy and Hubble Space Telescope imaging for a total of 17-34 members in each cluster. Using the dynamical masses together with the effective radii and the velocity dispersions, we find no indication of evolution of sizes or velocity dispersions with redshift at a given galaxy mass. We establish the Fundamental Plane (FP) and scaling relations between absorption line indices and velocity dispersions. We confirm that the FP is steeper at z ≈ 0.86 compared to the low-redshift FP, indicating that under the assumption of passive evolution the formation redshift, zform, depends on the galaxy velocity dispersion (or alternatively mass). At a velocity dispersion of σ = 125 km s-1 (Mass = 1010.55 M⊙) we find zform = 1.24 ± 0.05, while at σ = 225 km s-1 (Mass = 10 11.36 M⊙) the formation redshift is zform = 1.95+0.3 -0.2, for a Salpeter initial mass function. The three clusters follow similar scaling relations between absorption line indices and velocity dispersions as those found for low-redshift galaxies. The zero point offsets for the Balmer lines depend on cluster redshifts. However, the offsets indicate a slower evolution, and therefore higher formation redshift, than the zero point differences found from the FP, if interpreting the data using a passive evolution model. Specifically, the strength of the higher order Balmer lines Hδ and Hγ implies z form > 2.8. The scaling relations for the metal indices in general show small and in some cases insignificant zero point offsets, favoring high formation redshifts for a passive evolution model. Based on the absorption line indices and recent stellar population models from Thomas et al., we find that MS0451.6-0305 has a mean metallicity [M/H] approximately 0.2 dex below that of the other clusters and our low-redshift sample. We confirm our previous result that RXJ0152.7-1357 has a mean abundance ratio [α/Fe] approximately 0.3 dex higher than that of the other clusters. The differences in [M/H] and [α/Fe] between the high-redshift clusters and the low-redshift sample are inconsistent with a passive evolution scenario for early-type cluster galaxies over the redshift interval studied. Low-level star formation may be able to bring the metallicity of MS0451.6-0305 in agreement with the low-redshift sample, while we speculate whether galaxy mergers can lead to sufficiently large changes in the abundance ratios for the RXJ0152.7-1357 galaxies to allow them to reach the low-redshift sample values in the time available. © 2013. The American Astronomical Society. All rights reserved.


Schirmer M.,Gemini Observatory | Schirmer M.,Isaac Newton Group of Telescopes | Schirmer M.,University of Bonn
Astrophysical Journal, Supplement Series | Year: 2013

The last 15 years have seen a surge of new multi-chip optical and near-IR imagers. While some of them are accompanied by specific reduction pipelines, user-friendly and generic reduction tools are uncommon. In this paper I introduce THELI, an easy-to-use graphical interface driving an end-to-end pipeline for the reduction of any optical, near-IR, and mid-IR imaging data. The advantages of THELI when compared to other approaches are highlighted. Combining a multitude of processing algorithms and third party software, THELI provides researchers with a single, homogeneous tool. A short learning curve ensures quick success for new and more experienced observers alike. All tasks are largely automated, while at the same time a high level of flexibility and alternative reduction schemes ensure that widely different scientific requirements can be met. Over 90 optical and infrared instruments at observatories world-wide are pre-configured, while more can be added by the user. The Appendices contain three walk-through examples using public data (optical, near-IR, and mid-IR). Additional extensive documentation for training and troubleshooting is available online. © 2013. The American Astronomical Society. All rights reserved.


News Article | February 28, 2017
Site: www.gizmag.com

An international team of scientists may have discovered debris from a metal-rich, rocky asteroid falling into a white dwarf that comprises one half of a distant binary star system. The presence of the asteroid suggests that rocky, and potentially habitable worlds could potentially form in a two-star system, not entirely unlike the fictional planet Tatooine on which Luke Skywalker was raised in the Star Wars universe. Prior to the recent observations, it had been thought that the focus of the study, the solar system SDSS 1557, was centered around a single white dwarf star. However, upon closer observation the team was able to discern the presence of a second brown dwarf star, whose gravity was pulling on its larger neighbor. Ordinarily, in a single-star system, the planetary and sub-planetary bodies would form incredibly slowly from the material left over from the creation of the central star. The gravity of the new-born star would sculpt this material into what is known as a protoplanetary disk. Over time, particles of dust and other materials would collide to form larger and larger chunks of matter, and from these minuscule beginnings a planet could be born. However, it was thought that in a dual-star system, things may not be so simple. Prior to the new study, only gas giants, such as Jupiter or Saturn, had been discovered in double-star systems, leading astronomers to assume that the chaotic push and pull of the gravity of the duelling stars was stopping the rock and dust from coalescing and growing into rocky planets. Owing to the fact that the SDSS 1557 System lies some 1,000 light-years distant from Earth, and that the asteroid from which the debris originated was thought to be only 4 km (2.5 miles) in width, it would be impossible to have directly imaged its remains. However, by using the ESO's Very Large Telescope in concert with the Gemini Observatory South telescope, both of which are located in Chile, the team was able to observe the light signature of the material as it was drawn from its orbit and onto the surface of the white dwarf star. By measuring the light absorption of specific light wavelengths as this event unfolded, the team was able to deduce the chemical composition of the ex-asteroid. It was found that the rocky debris had a high metal content, and boasted an abundance of both silicon and magnesium, unlike the icy carbon-rich material detected in other binary systems. Asteroids in orbit around our sun are considered to be near-perfect time capsules that allow scientists to observe the building blocks of our solar system, and the same holds true for their counterparts in orbit around distant stars. The researchers believe that by analyzing the light signature of the debris, they can gain a greater understanding of how rocky planets could come to form under the gravitational influence of dual stars. The team believes that roughly 1.1 trillion tonnes of material collided with the surface of the star over the course of the event, and it is likely that, unless further debris is drawn to its surface, the newly-deposited metals will sink down into the star and disappear in a few weeks. The next step for the team will be to use the powerful Hubble Space Telescope to confirm that the asteroid was indeed composed of a rocky material as the new research suggests, rather than ice, which is more commonly found in binary star systems. Should the follow-up observations corroborate the team's findings, it will serve as a strong indicator that the formation of rocky planets is possible in a binary system, despite the tumultuous gravitational influence of the double stars.

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