Astronomers Track the Birth of a 'Super-Earth'

Astronomers Track the Birth of a 'Super-Earth':

A new model giving rise to young planetary systems offers a fresh solution to a puzzle that has vexed astronomers ever since new detection technologies and planet-hunting missions such as NASA's Kepler space telescope have revealed thousands of planets orbiting other stars: While the majority of these exoplanets fall into a category called super-Earths — bodies with a mass somewhere between Earth and Neptune — most of the features observed in nascent planetary systems were thought to require much more massive planets, rivaling or dwarfing Jupiter, the gas giant in our solar system.

In other words, the observed features of many planetary systems in their early stages of formation did not seem to match the type of exoplanets that make up the bulk of the planetary population in our galaxy. 

"We propose a scenario that was previously deemed impossible: how a super-Earth can carve out multiple gaps in disks," says Ruobing Dong, the Bart J. Bok postdoctoral fellow at the University of Arizona's Steward Observatory and lead author on the study, soon to be published in the Astrophysical Journal. "For the first time, we can reconcile the mysterious disk features we observe and the population of planets most commonly found in our galaxy." 

How exactly planets form is still an open question with a number of outstanding problems, according to Dong. 

"Kepler has found thousands of planets, but those are all very old, orbiting around stars a few billion years old, like our sun," he explains. "You could say we are looking at the senior citizens of our galaxy, but we don't know how they were born."

To find answers, astronomers turn to the places where new planets are currently forming: protoplanetary disks — in a sense, baby sisters of our solar system. 

Such disks form when a vast cloud of interstellar gas and dust condenses under the effect of gravity before collapsing into a swirling disk. At the center of the protoplanetary disk shines a young star, only a few million years old. As microscopic dust particles coalesce to sand grains, and sand grains stick together to form pebbles, and pebbles pile up to become asteroids and ultimately planets, a planetary system much like our solar system is born. 

"These disks are very short-lived," Dong explains. "Over time the material dissipates, but we don't know exactly how that happens. What we do know is that we see disks around stars that are 1 million years old, but we don't see them around stars that are 10 million years old."

In the most likely scenario, much of the disk's material gets accreted onto the star, some is blown away by stellar radiation and the rest goes into forming planets. 

Although protoplanetary disks have been observed in relative proximity to the Earth, it is still extremely difficult to make out any planets that may be forming within. Rather, researchers have relied on features such as gaps and rings to infer the presence of planets. 

"Among the explanations for these rings and gaps, those involving planets certainly are the most exciting and drawing the most attention," says co-author Shengtai Li, a research scientist at Los Alamos National Laboratory in Los Alamos, New Mexico. "As the planet orbits around the star, the argument goes, it may clear a path along its orbit, resulting in the gap we see."

Except that reality is a bit more complicated, as evidenced by two of the most prominent observations of protoplanetary disks, which were made with ALMA, the Atacama Large Millimeter/submillimeter Array in Chile. ALMA is an assembly of radio antennas between 7 and 12 meters in diameter and numbering 66 of them once completed. The images of HL Tau and TW Hydra, obtained in 2014 and 2016, respectively, have revealed the finest details so far in any protoplanetary disk, and they show some features that are difficult, if not impossible, to explain with current models of planetary formation, Dong says. 

"Among the gaps in HL Tau and TW Hya revealed by ALMA, two pairs of them are extremely narrow and very close to each other," he explains. "In conventional theory, it is difficult for a planet to open such gaps in a disk. They can never be this narrow and this close to each other for reasons of the physics involved." 

In the case of HL Tau and TW Hya, one would have to invoke two planets whose orbits hug each other very closely — a scenario that would not be stable over time and therefore is unlikely. 

While previous models could explain large, single gaps believed to be indicative of planets clearing debris and dust in their path, they failed to account for the more intricate features revealed by the ALMA observations. 

The model created by Dong and his co-authors results in what the team calls synthetic observations — simulations that look exactly like what ALMA would see on the sky. Dong's team accomplished this by tweaking the parameters going into the simulation of the evolving protoplanetary disk, such as assuming a low viscosity and adding the dust to the mix. Most previous simulations were based on higher disk viscosity and accounted only for the disk's gaseous component. 

"The viscosity in protoplanetary disks may be driven by turbulence and other physical effects," Li says. "It's a somewhat mysterious quantity — we know it's there, but we don't know its origin or how large its value is, so we think our assumptions are reasonable, considering that they result in the pattern that has actually been observed on the sky." 

Even more important, the synthetic observations emerged from the simulations without the necessity to invoke gas giants the size of Jupiter or larger. 

"One super-Earth turned out to be sufficient to create the multiple rings and multiple, narrow gaps we see in the actual observations," Dong says. 

As future research uncovers more of the inner workings of protoplanetary disks, Dong and his team will refine their simulations with new data. For now, their synthetic observations offer an intriguing scenario that provides a missing link between the features observed in many planetary infants and their grown-up counterparts. 

The study, "Multiple Disk Gaps and Rings Generated by a Single Super-Earth," by Ruobing Dong, Shentai Li, Eugene Chiang and Hui Li, will be published on July 13 in the Astrophysical Journal. 

Credit: arizona.edu

Juno Completes Flyby over Jupiter’s Great Red Spot

Juno Completes Flyby over Jupiter’s Great Red Spot:

NASA's Juno mission completed a close flyby of Jupiter and its Great Red Spot on July 10, during its sixth science orbit. All of Juno's science instruments and the spacecraft's JunoCam were operating during the flyby, collecting data that are now being returned to Earth. Juno's next close flyby of Jupiter will occur on Sept. 1. Raw images from the spacecraft’s latest flyby will be posted in coming days.

"For generations people from all over the world and all walks of life have marveled over the Great Red Spot," said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. "Now we are finally going to see what this storm looks like up close and personal."

The Great Red Spot is a 10,000-mile-wide (16,000-kilometer-wide) storm that has been monitored since 1830 and has possibly existed for more than 350 years. In modern times, the Great Red Spot has appeared to be shrinking. 

Juno reached perijove (the point at which an orbit comes closest to Jupiter's center) on July 10 at 6:55 p.m. PDT (9:55 p.m. EDT). At the time of perijove, Juno was about 2,200 miles (3,500 kilometers) above the planet's cloud tops. Eleven minutes and 33 seconds later, Juno had covered another 24,713 miles (39,771 kilometers), and was passing directly above the coiling crimson cloud tops of the Great Red Spot. The spacecraft passed about 5,600 miles (9,000 kilometers) above the clouds of this iconic feature.

On July 4 at 7:30 p.m. PDT (10:30 p.m. EDT), Juno logged exactly one year in Jupiter orbit, marking 71 million miles (114.5 million kilometers) of travel around the giant planet.

Juno launched on Aug. 5, 2011, from Cape Canaveral, Florida. During its mission of exploration, Juno soars low over the planet's cloud tops -- as close as about 2,100 miles (3,400 kilometers). During these flybys, Juno is probing beneath the obscuring cloud cover of Jupiter and studying its auroras to learn more about the planet's origins, structure, atmosphere and magnetosphere.

Early science results from NASA's Juno mission portray the largest planet in our solar system as a turbulent world, with an intriguingly complex interior structure, energetic polar aurora, and huge polar cyclones.

JPL manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute. The Juno mission is part of the New Frontiers Program managed by NASA's Marshall Space Flight Center in Huntsville, Alabama, for the Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft. JPL is a division of Caltech in Pasadena.

Credit: missionjuno.swri.edu

Hidden Stars May Make Planets Appear Smaller

Hidden Stars May Make Planets Appear Smaller:

In the search for planets similar to our own, an important point of comparison is the planet's density. A low density tells scientists a planet is more likely to be gaseous like Jupiter, and a high density is associated with rocky planets like Earth. But a new study suggests some are less dense than previously thought because of a second, hidden star in their systems.

As telescopes stare at particular patches of sky, they can't always differentiate between one star and two. A system of two closely orbiting stars may appear in images as a single point of light, even from sophisticated observatories such as NASA's Kepler space telescope. This can have significant consequences for determining the sizes of planets that orbit just one of these stars, says a forthcoming study in the Astronomical Journal by Elise Furlan of Caltech/IPAC-NExScI in Pasadena, California, and Steve Howell at NASA's Ames Research Center in California's Silicon Valley.

"Our understanding of how many planets are small like Earth, and how many are big like Jupiter, may change as we gain more information about the stars they orbit," Furlan said. "You really have to know the star well to get a good handle on the properties of its planets."

Some of the most well-studied planets outside our solar system -- or exoplanets -- are known to orbit lone stars. We know Kepler-186f, an Earth-size planet in the habitable zone of its star, orbits a star that has no companion (the habitable zone is the distance at which a rocky planet could support liquid water on its surface). TRAPPIST-1, the ultra-cool dwarf star that is home to seven Earth-size planets, does not have a companion either. That means there is no second star complicating the estimation of the planets' diameters, and therefore their densities.

But other stars have a nearby companion, high-resolution imaging has recently revealed. David Ciardi, chief scientist at the NASA Exoplanet Science Institute (NExScI) at Caltech, led a large-scale effort to follow up on stars that Kepler had studied using a variety of ground-based telescopes. This, combined with other research, has confirmed that many of the stars where Kepler found planets have binary companions. In some cases, the diameters of the planets orbiting these stars were calculated without taking the companion star into consideration. That means estimates for their sizes should be smaller, and their densities higher, than their true values. 

Previous studies determined that roughly half of all the sun-like stars in our sun's neighborhood have a companion within 10,000 astronomical units (an astronomical unit is equal to the average distance between the sun and Earth, 93 million miles or 150 million kilometers). Based on this, about 15 percent of stars in the Kepler field could have a bright, close companion -- meaning planets around these stars may be less dense than previously thought. 

When a telescope spots a planet crossing in front of its star -- an event called a "transit" -- astronomers measure the resulting apparent decrease in the star's brightness. The amount of light blocked during a transit depends on the size of the planet -- the bigger the planet, the more light it blocks, and the greater the dimming that is observed. Scientists use this information to determine the radius -- half the diameter -- of the planet.

If there are two stars in the system, the telescope measures the combined light of both stars. But a planet orbiting one of these stars will cause just one of them to dim. So, if you don't know that there is a second star, you will underestimate the size of the planet.

For example, if a telescope observes that a star dims by 5 percent, scientists would determine the transiting planet's size relative to that one star. But if a second star adds its light, the planet must be larger to cause the same amount of dimming.

If the planet orbits the brighter star in a binary pair, most of the light in the system comes from that star anyway, so the second star won't have a big effect on the planet's calculated size. But if the planet orbits the fainter star, the larger, primary star contributes more light to the system, and the correction to the calculated planet radius can be large -- it could double, triple or increase even more. This will affect how the planet's orbital distance is calculated, which could impact whether the planet is found to be in the habitable zone.

If the stars are roughly equal in brightness, the "new" radius of the planet is about 40 percent larger than if the light were assumed to come from a single star. Because density is calculated using the cube of the radius, this would mean a nearly three-fold decrease in density. The impact of this correction is most significant for smaller planets because it means a planet that had once been considered rocky could, in fact, be gaseous.

In the new study, Furlan and Howell focused on 50 planets in the Kepler observatory's field of view whose masses and radii were previously estimated. These planets all orbit stars that have stellar companions within about 1,700 astronomical units. For 43 of the 50 planets, previous reports of their sizes did not take into account the contribution of light from a second star. That means a revision to their reported sizes is necessary.

In most cases, the change to the planets' reported sizes would be small. Previous research showed that 24 of the 50 planets orbit the bigger, brighter star in a binary pair. Moreover, Furlan and Howell determined that 11 of these planets would be too large to be planets if they orbited the fainter companion star. So, for 35 of the 50 planets, the published sizes will not change substantially.

But for 15 of the planets, they could not determine whether they orbit the fainter or the brighter star in a binary pair. For five of the 15 planets, the stars in question are of roughly equal brightness, so their densities will decrease substantially regardless of which star they orbit.

This effect of companion stars is important for scientists characterizing planets discovered by Kepler, which has found thousands of exoplanets. It will also be significant for NASA's upcoming Transiting Exoplanet Survey Satellite (TESS) mission, which will look for small planets around nearby, bright stars and small, cool stars.

"In further studies, we want to make sure we are observing the type and size of planet we believe we are," Howell said. "Correct planet sizes and densities are critical for future observations of high-value planets by NASA's James Webb Space Telescope. In the big picture, knowing which planets are small and rocky will help us understand how likely we are to find planets the size of our own elsewhere in the galaxy."

Credit: NASA

Distant Galaxies ‘Lift the Veil’ on the End of the Cosmic Dark Ages

Distant Galaxies ‘Lift the Veil’ on the End of the Cosmic Dark Ages:

Astronomers studying the distant Universe have found that small star-forming galaxies were abundant when the Universe was only 800 million years old, a few percent of its present age. The results suggest that the earliest galaxies, which illuminated and ionized the Universe, formed at even earlier times.

Long ago, about 300,000 years after the beginning of the Universe (the Big Bang), the Universe was dark. There were as yet no stars and galaxies, and the Universe was filled with neutral hydrogen gas. At some point the first galaxies appeared, and their energetic radiation ionized their surroundings, the intergalactic gas, illuminating and transforming the Universe.

While this dramatic transformation is known to have occurred sometime in the interval between 300 million years and 1 billion years after the Big Bang, determining when the first galaxies formed is a challenge. The intergalactic gas, which is initially neutral, strongly absorbs and scatters the ultraviolet light emitted by the galaxies, making them difficult to detect.

To home in on when the transformation occurred, astronomers take an indirect approach. Using the demographics of small star-forming galaxies to determine when the intergalactic gas became ionized, they can infer when the ionizing sources, the first galaxies, formed. If star forming galaxies, which glow in the light of the hydrogen Lyman alpha line, are surrounded by neutral hydrogen gas, the Lyman alpha photons are readily scattered, much like headlights in fog, obscuring the galaxies. When the gas is ionized, the fog lifts, and the galaxies are easier to detect.

A new study taking this approach has discovered 23 candidate Lyman alpha emitting galaxies (LAEs) that were present 800 million years after the Big Bang (at a redshift of z~7), the largest sample detected to date at that epoch. The study, “Lyman-Alpha Galaxies in the Epoch of Reionization” (LAGER), was carried out by an international team of astronomers from China, the US, and Chile using the Dark Energy Camera (DECam) on the CTIO 4-m Blanco telescope.

While the study detected many LAEs, it also found that LAEs were 4 times less common at 800 million years than they were a short time later, at 1 billion years (at a redshift of z~5.7). The results imply that the process of ionizing the Universe began early and was still incomplete at 800 million years, with the intergalactic gas about half neutral and half ionized at that epoch. The low incidence rate of LAEs at 800 million years results from the suppression of their Lyman alpha emission by neutral intergalactic gas.

The study shows that “the fog was already lifting when the universe was 5% of its current age”, explained Sangeeta Malhotra (Goddard Space Flight Center and Arizona State University), one of the co-leads of the survey.

Junxian Wang (USTC), the organizer of the study, further explained, “Our finding that the intergalactic gas is 50% ionized at z ~ 7 implies that a large fraction of the first galaxies that ionized and illuminated the universe formed early, less than 800 million years after the Big Bang.”

For Zhenya Zheng (Shanghai Astronomical Observatory, CAS), the lead author of the paper describing these results, “800 million years is the current frontier in reionization studies.” While hundreds of LAEs have been found at later epochs, only about two dozen candidate LAEs were known at 800 million years prior to the current study. The new results dramatically increase the number of LAEs known at this epoch.

“None of this science would have been possible without the widefield capabilities of DECam and its community pipeline for data reduction,” remarked coauthor James Rhoads. “These capabilities enable efficient surveys and thereby the discovery of faint galaxies as well as rare, bright ones.”

To build on these results, the team is “continuing the search for distant star forming galaxies over a larger volume of the Universe”, said Leopoldo Infante (Pontificia Catolica University of Chile and the Carnegie Institution for Science), “to study the clustering of LAEs.” Clustering provides unique insights into how the fog lifts. The team is also investigating the nature of these distant galaxies.

Credit: noao.edu

New Evidence in Support of the Planet Nine Hypothesis

New Evidence in Support of the Planet Nine Hypothesis:

Last year, the existence of an unknown planet in our solar system was announced. However, this hypothesis was subsequently called into question as biases in the observational data were detected. Now Spanish astronomers have used a novel technique to analyse the orbits of the so-called extreme trans-Neptunian objects and, once again, they point out that there is something perturbing them: a planet located at a distance between 300 to 400 times the Earth-Sun separation.

Scientists continue to argue about the existence of a ninth planet within our solar system. At the beginning of 2016, researchers from the California Institute of Technology (Caltech, USA) announced that they had evidence of the existence of this object, located at an average distance of 700 AU or astronomical units (700 times the Earth-Sun separation) and with a mass ten times that of the Earth. Their calculations were motivated by the peculiar distribution of the orbits found for the trans-Neptunian objects (TNO) of the Kuiper belt, which apparently revealed the presence of a Planet Nine or X in the confines of the solar system.

However, scientists from the Canadian-French-Hawaiian project OSSOS detected biases in their own observations of the orbits of the TNOs, which had been systematically directed towards the same regions of the sky, and considered that other groups, including the Caltech group, may be experiencing the same issues. According to these scientists, it is not necessary to propose the existence of a massive perturber (a Planet Nine) to explain these observations, as these are compatible with a random distribution of orbits.

Now, however, two astronomers from the Complutense University of Madrid have applied a new technique, less exposed to observational bias, to study a special type of trans-Neptunian objects: the extreme ones (ETNOs, located at average distances greater than 150 AU and that never cross Neptune's orbit). For the first time, the distances from their nodes to the Sun have been analysed, and the results, published in the journal ‘MNRAS: Letters’, once again indicate that there is a planet beyond Pluto.

The nodes are the two points at which the orbit of an ETNO, or any other celestial body, crosses the plane of the solar system. These are the precise points where the probability of interacting with other objects is the largest, and therefore, at these points, the ETNOs may experience a drastic change in their orbits or even a collision.

“If there is nothing to perturb them, the nodes of these extreme trans-Neptunian objects should be uniformly distributed, as there is nothing for them to avoid, but if there are one or more perturbers, two situations may arise,” explains Carlos de la Fuente Marcos, one of the authors, to SINC. “One possibility is that the ETNOs are stable, and in this case they would tend to have their nodes away from the path of possible perturbers, he adds, but if they are unstable they would behave as the comets that interact with Jupiter do, that is tending to have one of the nodes close to the orbit of the hypothetical perturber”.

Using calculations and data mining, the Spanish astronomers have found that the nodes of the 28 ETNOs analysed (and the 24 extreme Centaurs with average distances from the Sun of more than 150 AU) are clustered in certain ranges of distances from the Sun; furthermore, they have found a correlation, where none should exist, between the positions of the nodes and the inclination, one of the parameters which defines the orientation of the orbits of these icy objects in space.

“Assuming that the ETNOs are dynamically similar to the comets that interact with Jupiter, we interpret these results as signs of the presence of a planet that is actively interacting with them in a range of distances from 300 to 400 AU,” says De la Fuente Marcos, who emphasizes: “We believe that what we are seeing here cannot be attributed to the presence of observational bias”.

Until now, studies that challenged the existence of Planet Nine using the data available for these trans-Neptunian objects argued that there had been systematic errors linked to the orientations of the orbits (defined by three angles), due to the way in which the observations had been made. Nevertheless, the nodal distances mainly depend on the size and shape of the orbit, parameters which are relatively free of observational bias.

“It is the first time that the nodes have been used to try to understand the dynamics of the ETNOs”, the co-author points out, as he admits that discovering more ETNOs (at the moment, only 28 are known) would permit the proposed scenario to be confirmed and subsequently constrain the orbit of the unknown planet via the analysis of the distribution of the nodes.

The authors note that their study supports the existence of a planetary object within the range of parameters considered both in the Planet Nine hypothesis of Mike Brown and Konstantin Batygin from Caltech, and in the original one proposed in 2014 by Scott Sheppard from the Carnegie Institute and Chadwick Trujillo from the University of North Arizona; in addition to following the lines of their own earlier studies (the latest led by the Instituto de Astrofísica de Canarias), which suggested that there is more than one unknown planet in our solar system.

De la Fuente Marcos explains that the hypothetical Planet Nine suggested in this study has nothing to do with another possible planet or planetoid situated much closer to us, and hinted at by other recent findings. Also applying data mining to the orbits of the TNOs of the Kuiper Belt, astronomers Kathryn Volk and Renu Malhotra from the University of Arizona (USA) have found that the plane on which these objects orbit the Sun is slightly warped, a fact that could be explained if there is a perturber of the size of Mars at 60 AU from the Sun.

“Given the current definition of planet, this other mysterious object may not be a true planet, even if it has a size similar to that of the Earth, as it could be surrounded by huge asteroids or dwarf planets,” explains the Spanish astronomer, who goes on to say: “In any case, we are convinced that Volk and Malhotra's work has found solid evidence of the presence of a massive body beyond the so-called Kuiper Cliff, the furthest point of the trans-Neptunian belt, at some 50 AU from the Sun, and we hope to be able to present soon a new work which also supports its existence”.

Credit: agenciasinc.es

W51: Chandra Peers into a Nurturing Cloud

W51: Chandra Peers into a Nurturing Cloud:

In the context of space, the term 'cloud' can mean something rather different from the fluffy white collections of water in the sky or a way to store data or process information. Giant molecular clouds are vast cosmic objects, composed primarily of hydrogen molecules and helium atoms, where new stars and planets are born. These clouds can contain more mass than a million suns, and stretch across hundreds of light years.

The giant molecular cloud known as W51 is one of the closest to Earth at a distance of about 17,000 light years. Because of its relative proximity, W51 provides astronomers with an excellent opportunity to study how stars are forming in our Milky Way galaxy.

A new composite image of W51 shows the high-energy output from this stellar nursery, where X-rays from Chandra are colored blue. In about 20 hours of Chandra exposure time, over 600 young stars were detected as point-like X-ray sources, and diffuse X-ray emission from interstellar gas with a temperature of a million degrees or more was also observed. Infrared light observed with NASA's Spitzer Space Telescope appears orange and yellow-green and shows cool gas and stars surrounded by disks of cool material.

W51 contains multiple clusters of young stars. The Chandra data show that the X-ray sources in the field are found in small clumps, with a clear concentration of more than 100 sources in the central cluster, called G49.5−0.4.

Although the W51 giant molecular cloud fills the entire field-of-view of this image, there are large areas where Chandra does not detect any diffuse, low energy X-rays from hot interstellar gas. Presumably dense regions of cooler material have displaced this hot gas or blocked X-rays from it.

One of the massive stars in W51 is a bright X-ray source that is surrounded by a concentration of much fainter X-ray sources, as shown in a close-up view of the Chandra image. This suggests that massive stars can form nearly in isolation, with just a few lower mass stars rather than the full set of hundreds that are expected in typical star clusters.

Another young, massive cluster located near the center of W51 hosts a star system that produces an extraordinarily large fraction of the highest energy X-rays detected by Chandra from W51. Theories for X-ray emission from massive single stars can't explain this mystery, so it likely requires the close interaction of two very young, massive stars. Such intense, energetic radiation must change the chemistry of the molecules surrounding the star system, presenting a hostile environment for planet formation.

A paper describing these results, led by Leisa Townsley (Penn State), appeared in the July 14th 2014 issue of The Astrophysical Journal Supplement Series and is available online.

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Credit: chandra.harvard.edu

Third Planet Orbiting the Binary Star KIC 5095269 Discovered

Third Planet Orbiting the Binary Star KIC 5095269 Discovered:

A long time ago in a galaxy far, far away, Luke Skywalker lived on a planet circling twin suns. While Star Wars is science-fiction, two stars in orbit of each other is firmly based in reality. An astronomy student working with an Australian Astronomical Observatory (AAO) astronomer has uncovered evidence of a new planet orbiting a binary star (two stars that orbit a common center of mass).

Adding interest to this discovery is the observation that the planet orbits the stars on a tilt – an example of the weird and wonderful diversity of the Universe.

The binary star, KIC 5095269, system was first observed by NASA’s Kepler space telescope.

The newly-discovered planet has a mass 7.7 times more than Jupiter and orbits the binary star every 237.7 days.

“My PhD research involves performing an eclipse timing variation study of binary stars in order to look for any third bodies that may be present, like stars/brown dwarfs or planets,” PhD student Kelvin Getley, who lead authored the journal article announcing the discovery, said.

“I created a program that determined when one star passes in front of another as seen from Earth, and compared them to what we’d expect to see if there was nothing else in the system.

“My PhD supervisors, Professor Brad Carter and Dr Rachel King from the University of Southern Queensland (USQ), and Simon O'Toole from the AAO, guided and advised me, and helped come up with tests that could be done on the system to try to make sure what we were seeing was possible.”

Supervisor and AAO astronomer Dr O’Toole is an expert in exoplanetary systems.

“This is a really neat result,” Dr O’Toole said, “Planets orbiting two stars have been found before, but the cool thing here is that Kelvin has discovered a planet with a tilted orbit, more reminiscent of Pluto than the other planets in our Solar System."

Professor Carter leads USQ’s Astrophysics Research Program Team and commended Mr Getley on his work and discovery.

“Kelvin’s research demonstrates that evidence for new worlds can be gathered through an innovative analysis of the Kepler space telescope's treasure trove of observational data," he said.

Mr Getley is studying a PhD in Astronomy and is an external USQ student living in Charlton, Victoria, with the support of the AAO.

“Being an astronomer is something that I've wanted to be basically my entire life,” he said.

“My granddad was interested in astronomy as a hobby so I grew up reading his books. Doing this research, and making a discovery like this is amazing.”

Credit: aao.gov.au

Smallest-Ever Star Discovered by Astronomers

Smallest-Ever Star Discovered by Astronomers:

The smallest star yet measured has been discovered by a team of astronomers led by the University of Cambridge. With a size just a sliver larger than that of Saturn, the gravitational pull at its stellar surface is about 300 times stronger than what humans feel on Earth.

The star is likely as small as stars can possibly become, as it has just enough mass to enable the fusion of hydrogen nuclei into helium. If it were any smaller, the pressure at the center of the star would no longer be sufficient to enable this process to take place. Hydrogen fusion is also what powers the Sun, and scientists are attempting to replicate it as a powerful energy source here on Earth.

These very small and dim stars are also the best possible candidates for detecting Earth-sized planets which can have liquid water on their surfaces, such as TRAPPIST-1, an ultracool dwarf surrounded by seven temperate Earth-sized worlds.

The newly-measured star, called EBLM J0555-57Ab, is located about six hundred light years away. It is part of a binary system, and was identified as it passed in front of its much larger companion, a method which is usually used to detect planets, not stars. Details will be published in the journal Astronomy & Astrophysics.

“Our discovery reveals how small stars can be,” said Alexander Boetticher, the lead author of the study, and a Master’s student at Cambridge’s Cavendish Laboratory and Institute of Astronomy. “Had this star formed with only a slightly lower mass, the fusion reaction of hydrogen in its core could not be sustained, and the star would instead have transformed into a brown dwarf.”

EBLM J0555-57Ab was identified by WASP, a planet-finding experiment run by the Universities of Keele, Warwick, Leicester and St Andrews. EBLM J0555-57Ab was detected when it passed in front of, or transited, its larger parent star, forming what is called an eclipsing stellar binary system. The parent star became dimmer in a periodic fashion, the signature of an orbiting object. Thanks to this special configuration, researchers can accurately measure the mass and size of any orbiting companions, in this case a small star. The mass of EBLM J0555-57Ab was established via the Doppler, wobble method, using data from the CORALIE spectrograph.

“This star is smaller, and likely colder than many of the gas giant exoplanets that have so far been identified,” said von Boetticher. “While a fascinating feature of stellar physics, it is often harder to measure the size of such dim low-mass stars than for many of the larger planets. Thankfully, we can find these small stars with planet-hunting equipment, when they orbit a larger host star in a binary system. It might sound incredible, but finding a star can at times be harder than finding a planet.”

This newly-measured star has a mass comparable to the current estimate for TRAPPIST-1, but has a radius that is nearly 30% smaller. “The smallest stars provide optimal conditions for the discovery of Earth-like planets, and for the remote exploration of their atmospheres,” said co-author Amaury Triaud, senior researcher at Cambridge’s Institute of Astronomy. “However, before we can study planets, we absolutely need to understand their star; this is fundamental.”

Although they are the most numerous stars in the Universe, stars with sizes and masses less than 20% that of the Sun are poorly understood, since they are difficult to detect due to their small size and low brightness. The EBLM project, which identified the star in this study, aims to plug that lapse in knowledge. “Thanks to the EBLM project, we will achieve a far greater understanding of the planets orbiting the most common stars that exist, planets like those orbiting TRAPPIST-1,” said co-author Professor Didier Queloz of Cambridge’ Cavendish Laboratory.

Credit: cam.ac.uk

Shedding Light on Galaxies' Rotation Secrets

Shedding Light on Galaxies' Rotation Secrets:

The dichotomy concerns the so-called angular momentum (per unit mass), that in physics is a measure of size and rotation velocity. Spiral galaxies are found to be strongly rotating, with an angular momentum higher by a factor of about 5 than ellipticals. What is the origin of such a difference?

An international research team investigated the issue in a study just published in the Astrophysical Journal. The team was led by SISSA Ph.D. student JingJing Shi under the supervision of Prof. Andrea Lapi and Luigi Danese, and in collaboration with Prof. Huiyuan Wang from USTC (Hefei) and Dr. Claudia Mancuso from IRA-INAF (Bologna). The researchers inferred from observations the amount of gas fallen into the central region of a developing galaxy, where most of the star formation takes places.

The outcome is that in elliptical galaxies only about 40% of the available gas fell into that central region. More relevantly, this gas fueling star formation was characterized by a rather low angular momentum since the very beginning. This is in stark contrast with the conditions found in spirals, where most of the gas ending up in stars had an angular momentum appreciably higher. In this vein, the researchers have traced back the dichotomy in the angular momentum of spiral and elliptical galaxies to their different formation history. Elliptical galaxies formed most of their stars in a fast collapse where angular momentum is dissipated. This process is likely stopped early on by powerful gas outflows from supernova explosions, stellar winds and possibly even from the central supermassive black hole. For spirals, on the other hand, the gas infelt slowly conserving its angular momentum and stars formed steadily along a timescale comparable to the age of the Universe.

"Till recent years, in the paradigm of galaxy formation and evolution, elliptical galaxies were thought to have formed by the merging of stellar disks in the distant Universe. Along this line, their angular momentum was thought to be the result of dissipative processes during such merging events" say the researchers. Recently, this paradigm had been challenged by far-infrared/sub-millimeter observations brought about by the advent of space observatories like Herschel and ground based interferometers like the Atacama Large Millimeter Array (ALMA).

These observations have the power of penetrating through interstellar dust and so to unveil the star formation processes in the very distant, dusty galaxies, that constituted the progenitors of local ellipticals. "The net outcome from these observations is that the stars populating present-day ellipticals are mainly formed in a fast dissipative collapse in the central regions of dusty starforming galaxies. After a short timescale of less than 1 billion years the star formation has been quenched by powerful gas outflows". Despite this change of perspective, the origin of the low angular momentum observed in local ellipticals still remained unclear.

"This study reconciles the low angular momentum observed in present-day ellipticals with the new paradigm emerging from Herschel and ALMA observations of their progenitors" conclude the scientists. "We demonstrated that the low angular momentum of ellipticals is mainly originated by nature in the central regions during the early galaxy formation process, and not nurtured substantially by the environment via merging events, as envisaged in previous theories".

Credit: sissa.it

Asteroid 2017 MR8 to Fly by Earth on Saturday

Asteroid 2017 MR8 to Fly by Earth on Saturday:

A newly discovered house-sized asteroid designated 2017 MR8 is about to give Earth a close shave on Saturday, June 15. The space rock will pass by our planet at 2:11 UTC at a safe distance of about 3.29 lunar distances (LD), or 1.26 million kilometers with a relative velocity of 6.9 km/s.

2017 MR8 was detected June 30 by the Mount Lemmon Survey (MLS), which uses a 1.52 m cassegrain reflector telescope at Mount Lemmon Observatory in Arizona. MLS is one of the most prolific surveys when it comes to discovering near-Earth objects (NEOs). So far, it has detected more than 50,000 minor planets.

Astronomers reveal that 2017 MR8 is an Apollo-type asteroid and an estimated diameter between 19 and 59 meters. The object has an absolute magnitude of 25 and orbits the sun every 1.76 years at a distance of approximately 1.46 astronomical units (AU).

One day after the fly-by of 2017 MR8, another close approach of a NEO is expected. The Apollo-type asteroid known as 2007 MB4 has a diameter between 59 and 190 meters and will pass by Earth at a distance of about 14.48 LD (5.56 million kilometers).

On July 13, there were 1,803 Potentially Hazardous Asteroids (PHAs) detected, however none of them is on a collision course with our planet. PHAs are asteroids larger than 100 meters that can come closer to Earth than 19.5 LD.

The Last Survivors on Earth

The Last Survivors on Earth:

The world's most indestructible species, the tardigrade, an eight-legged micro-animal, also known as the water bear, will survive until the Sun dies, according to a new Oxford University collaboration. The new study published in Scientific Reports, has shown that the tiny creatures, will survive the risk of extinction from all astrophysical catastrophes, and be around for at least 10 billion years - far longer than the human race.

Although much attention has been given to the cataclysmic impact that an astrophysical event would have on human life, very little has been published around what it would take to kill the tardigrade, and wipe out life on this planet.

The research implies that life on Earth in general, will extend as long as the Sun keeps shining. It also reveals that once life emerges, it is surprisingly resilient and difficult to destroy, opening the possibility of life on other planets.

Tardigrades are the toughest, most resilient form of life on earth, able to survive for up to 30 years without food or water, and endure temperature extremes of up to 150 degrees Celsius, the deep sea and even the frozen vacuum of space. The water-dwelling micro animal can live for up to 60 years, and grow to a maximum size of 0.5mm, best seen under a microscope. Researchers from the Universities of Oxford and Harvard, have found that these life forms will likely survive all astrophysical calamities, such as an asteroid, since they will never be strong enough to boil off the world's oceans.

Three potential events were considered as part of their research, including; large asteroid impact, and exploding stars in the form of supernovae or gamma ray bursts.

There are only a dozen known asteroids and dwarf planets with enough mass to boil the oceans (2x10^18 kg), these include (Vesta 2x10^20 kg) and Pluto (10^22 kg), however none of these objects will intersect the Earth's orbit and pose a threat to tardigrades.

In order to boil the oceans an exploding star would need to be 0.14 light-years away. The closest star to the Sun is four light years away and the probability of a massive star exploding close enough to Earth to kill all forms of life on it, within the Sun's lifetime, is negligible.

Gamma-ray bursts are brighter and rarer than supernovae. Much like supernovas, gamma-ray bursts are too far away from earth to be considered a viable threat. To be able to boil the world's oceans the burst would need to be no more than 40 light-years away, and the likelihood of a burst occurring so close is again, minor.

Dr Rafael Alves Batista, Co-author and Post-Doctoral Research Associate in the Department of Physics at Oxford University, said: 'Without our technology protecting us, humans are a very sensitive species. Subtle changes in our environment impact us dramatically. There are many more resilient species' on earth. Life on this planet can continue long after humans are gone.

'Tardigrades are as close to indestructible as it gets on Earth, but it is possible that there are other resilient species examples elsewhere in the universe. In this context there is a real case for looking for life on Mars and in other areas of the solar system in general. If Tardigrades are earth's most resilient species, who knows what else is out there.'

Dr David Sloan, Co-author and Post-Doctoral Research Associate in the Department of Physics at Oxford University, said: 'A lot of previous work has focused on 'doomsday' scenarios on Earth - astrophysical events like supernovae that could wipe out the human race. Our study instead considered the hardiest species - the tardigrade. As we are now entering a stage of astronomy where we have seen exoplanets and are hoping to soon perform spectroscopy, looking for signatures of life, we should try to see just how fragile this hardiest life is. To our surprise we found that although nearby supernovae or large asteroid impacts would be catastrophic for people, tardigrades could be unaffected. Therefore it seems that life, once it gets going, is hard to wipe out entirely. Huge numbers of species, or even entire genera may become extinct, but life as a whole will go on.'

In highlighting the resilience of life in general, the research broadens the scope of life beyond Earth, within and outside of this solar system. Professor Abraham Loeb, co-author and chair of the Astronomy department at Harvard University, said: 'It is difficult to eliminate all forms of life from a habitable planet. The history of Mars indicates that it once had an atmosphere that could have supported life, albeit under extreme conditions. Organisms with similar tolerances to radiation and temperature as tardigrades could survive long-term below the surface in these conditions. The subsurface oceans that are believed to exist on Europa and Enceladus, would have conditions similar to the deep oceans of Earth where tardigrades are found, volcanic vents providing heat in an environment devoid of light. The discovery of extremophiles in such locations would be a significant step forward in bracketing the range of conditions for life to exist on planets around other stars.'

Credit: ox.ac.uk

More to Life Than the Habitable Zone

More to Life Than the Habitable Zone:

Two separate teams of scientists have identified major challenges for the development of life in what has recently become one of the most famous exoplanet systems, TRAPPIST-1. The teams, both led by researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., say the behavior of the star in the TRAPPIST-1 system makes it much less likely than generally thought, that planets there could support life.

The TRAPPIST-1 star, a red dwarf, is much fainter and less massive than the Sun. It is rapidly spinning and generates energetic flares of ultraviolet (UV) radiation.

The first team, a pair of CfA theorists, considered many factors that could affect conditions on the surfaces of planets orbiting red dwarfs. For the TRAPPIST-1 system they looked at how temperature could have an impact on ecology and evolution, plus whether ultraviolet radiation from the central star might erode atmospheres around the seven planets surrounding it. These planets are all much closer to the star than the Earth is to the Sun, and three of them are located well within the habitable zone.

"The concept of a habitable zone is based on planets being in orbits where liquid water could exist," said Manasvi Lingam, a Harvard researcher who led the study. "This is only one factor, however, in determining whether a planet is hospitable for life."

Lingam and his co-author, Harvard professor Avi Loeb, found that planets in the TRAPPIST-1 system would be barraged by UV radiation with an intensity far greater than experienced by Earth.

"Because of the onslaught by the star's radiation, our results suggest the atmosphere on planets in the TRAPPIST-1 system would largely be destroyed," said Loeb. "This would hurt the chances of life forming or persisting."

Lingam and Loeb estimate that the chance of complex life existing on any of the three TRAPPIST-1 planets in the habitable zone is less than 1% of that for life existing on Earth.

In a separate study, another research team from the CfA and the University of Massachusetts in Lowell found that the star in TRAPPIST-1 poses another threat to life on planets surrounding it. Like the Sun, the red dwarf in TRAPPIST-1 is sending a stream of particles outwards into space. However, the pressure applied by the wind from TRAPPIST-1's star on its planets is 1,000 to 100,000 times greater than what the solar wind exerts on the Earth.

The authors argue that the star’s magnetic field will connect to the magnetic fields of any planets in orbit around it, allowing particles from the star’s wind to directly flow onto the planet’s atmosphere. If this flow of particles is strong enough, it could strip the planet's atmosphere and perhaps evaporate it entirely.

"The Earth's magnetic field acts like a shield against the potentially damaging effects of the solar wind," said Cecilia Garraffo of the CfA, who led the new study. "If Earth were much closer to the Sun and subjected to the onslaught of particles like the TRAPPIST-1 star delivers, our planetary shield would fail pretty quickly."

While these two studies suggest that the likelihood of life may be lower than previously thought, it does not mean the TRAPPIST-1 system or others with red dwarf stars are devoid of life.

"We're definitely not saying people should give up searching for life around red dwarf stars," said Garraffo's co-author Jeremy Drake, also from CfA. "But our work and the work of our colleagues shows we should also target as many stars as possible that are more like the Sun."

The paper by Lingam and Loeb was published in the International Journal of Astrobiology and is available online. The paper by Garraffo et al, also available online, has been published by The Astrophysical Journal Letters.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Credit: cfa.harvard.edu

New Horizons Unveils New Maps of Pluto, Charon on Flyby Anniversary

New Horizons Unveils New Maps of Pluto, Charon on Flyby Anniversary:

On July 14, 2015, NASA's New Horizons spacecraft made its historic flight through the Pluto system – providing the first close-up images of Pluto and its moons and collecting other data that has transformed our understanding of these mysterious worlds on the solar system's outer frontier. Scientists are still analyzing and uncovering data that New Horizons recorded and sent home after the encounter. On the two-year anniversary of the flyby, the team is unveiling a set of detailed, high-quality global maps of Pluto and its largest moon, Charon.

"The complexity of the Pluto system — from its geology to its satellite system to its atmosphere— has been beyond our wildest imagination," said Alan Stern, New Horizons principal investigator from the Southwest Research Institute in Boulder, Colorado. "Everywhere we turn are new mysteries. These new maps from the landmark exploration of Pluto by NASA's New Horizons mission in 2015 will help unravel these mysteries and are for everyone to enjoy."

The new maps include global mosaics of Pluto and Charon, assembled from nearly all of the highest-resolution images obtained by New Horizons' Long-Range Reconnaissance Imager (LORRI) and the Multispectral Visible Imaging Camera (MVIC). These mosaics are the most detailed and comprehensive global views yet of the Pluto and Charon surfaces using New Horizons data.

The new collection also includes topography maps of the hemispheres of Pluto and Charon visible to New Horizons during the spacecraft's closest approach. The topography is derived from digital stereo-image mapping tools that measure the parallax – or the difference in the apparent relative positions – of features on the surface obtained at different viewing angles during the encounter. Scientists use these parallax displacements of high and low terrain to estimate landform heights.

Both the new Pluto and the new Charon global mosaics have been overlain with transparent, colorized topography data wherever on their surfaces stereo data is available.

The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, manages the New Horizons mission for NASA's Science Mission Directorate. Stern, of the Southwest Research Institute (SwRI), is the principal investigator and leads the mission; SwRI leads the science team, payload operations, and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. APL designed, built and operates the New Horizons spacecraft.

Credit: pluto.jhuapl.edu

AIDA Mission to Validate Crucial Asteroid Deflection Technology

AIDA Mission to Validate Crucial Asteroid Deflection Technology:

While there is currently no imminent asteroid threat and none of known near-Earth objects (NEOs) is on collision course with our planet, humanity should be prepared for the worst. With that thought in mind NASA and ESA are developing the Asteroid Impact and Deflection Assessment (AIDA) mission, which main goal is to demonstrate the kinetic impact technique that could change the motion of a potentially hazardous asteroid.

The AIDA mission will consist of two spacecraft sent to the binary asteroid called Didymos. Built by ESA, the Asteroid Impact Mission (AIM) will be launched in October 2020 and is expected to be injected into the orbit of the larger asteroid. NASA’s contribution to this endeavor, the Double Asteroid Redirection Test (DART), will be launched into space nearly one year later and slated to crash into the smaller asteroid in October 2022. AIM will be just in place to observe the impact and study its aftermath.

“This mission, in partnership with ESA and NASA, will allow us to validate the technology of the kinetic impactor and also to improve our understanding of threatening asteroids,” Patrick Michel, AIM/AIDA investigator at the Côte d'Azur Observatory (OCA), told Astrowatch.net.

Therefore, the mission would be essential for the most one of the most important asteroid deflection technology – the kinetic impactor. In particular, AIDA will demonstrate the feasibility of this technique based on the data gathered by observing DART’s crash into the Didymos’ moon with a velocity of about six km/s. AIM will orbit the asteroid in order to perform detailed before-and-after observations of the structure of the space rock itself, as well as its orbit, to thoroughly characterize the kinetic impact and the consequences.

“To make sure a technique is valid and that we know how to use it, we need a test. Otherwise, we can talk but it will remain on paper and we cannot guarantee anything. And this is why we still push for the AIDA space mission to happen,” Michel said.

He noted that the success of AIDA will have many implications for planetary defense, science and asteroid mining because the knowledge needed for these three aims is essentially the same. According to him, it will prove that asteroids are the only natural risk that we can predict and prevent by making the necessary steps.

“AIDA, if done, will accomplish the step that will allow us to tell the future generations: we did our duty, we have now a validated tool to prevent the risk! And it will also come with science and technology returns, which contributes to inspire young generations,” Michel noted.

The AIM spacecraft is still in its conceptual phase. When it comes to DART, the probe was recently moved by NASA from concept development to preliminary design phase.

A New Search for Extrasolar Planets from the Arecibo Observatory

A New Search for Extrasolar Planets from the Arecibo Observatory:

The National Science Foundation’s Arecibo Observatory and the Planetary Habitability Laboratory of the University of Puerto Rico at Arecibo joined the Red Dots project using the ESO’s exoplanet-hunter in the search for new planets around our nearest stars. This new collaboration will simultaneously observe in both the optical and radio spectrum Barnard’s Star, a popular star in the science fiction literature.

Barnard's star is a low-mass red dwarf almost six light-years away and the second-closest stellar system to our Sun after the Alpha Centauri triple-star system. There are hints of a possible super-Earth mass planet in a cold orbit around this star. 

The Arecibo Observatory has a new campaign to observe nearby red dwarf stars with planets. The purpose of this campaign is to detect radio emissions from these stars, such as from flares, to help characterize their radiation and magnetic environment and any potential perturbations due to other bodies. These perturbations might reveal the presence of new sub-stellar objects including planets.

Barnard’s Star will be the eighth red dwarf star to be recently observed by the Arecibo Observatory. Results from Gliese 436, Ross 128, Wolf 359, HD 95735, BD +202465, V* RY Sex, and K2-18 are currently being analyzed. These observations are led by Prof. Abel Méndez, Director of the Planetary Habitability Laboratory of the University of Puerto Rico at Arecibo in collaboration with Dr. Jorge Zuluaga from the Universidad de Antioquia in Colombia.

The Red Dots team will be joining the observations with the Arecibo Observatory of Barnard’s Star in coordination with other observatories. They are planning simultaneous photometric and spectral observations from SNO, LCO, TJO, and CARMENES from Spain, and earlier with ASH2 from Chile. All these observations will be used to understand the star but more observations using the ESO’s exoplanet-hunter by the Red Dots team will be necessary for the detection and confirmation of any new planet.

The first extrasolar planets were discovered from the Arecibo Observatory in 1992. They were three small planets named Draugr, Poltergeist, and Phobetor around the Lich Pulsar, a fast rotating neutron star that emits a beam of electromagnetic radiation. The first planet around a sun-like star was later discovered in 1995 and today we know of more than 3,500 of them. Recent observations by the Arecibo Observatory have been able to detect brown dwarfs, but no new planet yet.

The first and only time that Barnard’s Star was observed from the Arecibo Observatory was during the SETI Institute’s Phoenix Project (1998-2004). The new observations are in a different frequency (4 to 5 GHz) where radio emission from stellar flares have been observed in other similar or cooler objects. This is the first time Barnard’s Star is seen with such frequencies and sensitivity.

The observations of Barnard’s Star will take place on Sunday, July 16. Another star, Ross 128, will be observed again later that day because it showed potential radio emissions that require follow-up. Results from these observations will be available later that week. The Red Dots team keeps an open journal of their observational campaign.

Credit: phl.upr.edu