Evidence of forming planet discovered 335 light years from Earth

This graphic is an artist’s conception of the young massive star HD100546 and its surrounding disk. 

Credit: P. Marenfeld & NOAO/AURA/NSF

An international team of scientists led by a Clemson University astrophysicist has discovered new evidence that planets are forming around a star about 335 light years from Earth.

The team found carbon monoxide emission that strongly suggests a planet is orbiting a relatively young star known as HD100546. The candidate planet is the second that astronomers have discovered orbiting the star.

Theories of how planets form are well-developed. But if the new study's findings are confirmed, the activity around HD100546 would mark one of the first times astronomers have been able to directly observe planet formation happening.

New discoveries from the star could allow astronomers to test their theories and learn more about the formation of solar systems, including our own, said Sean Brittain, an associate professor of astronomy and astrophysics at Clemson.

"This system is very close to Earth relative to other disk systems," he said. "We're able to study it at a level of detail that you can't do with more distant stars. This is the first system where we've been able to do this.

"Once we really understand what's going on, the tools that we are developing can then be applied to a larger number of systems that are more distant and harder to see."

For more than a decade, the team has focused some of Earth's most powerful telescopes on a disk-shaped cloud of gas and dust that surrounds HD100546.

The star is about 2.5 times larger and 30 times brighter than the sun, Brittain said. It's in the constellation Musca, or The Fly, and can only be seen from the Southern Hemisphere.

Brittain made three trips to Chile as far back as 2003 to gather data for the research. He used telescopes at the Gemini Observatory and the European Southern Observatory.

The new planet astronomers believe they have found what would be an uninhabitable gas giant at least three times the size of Jupiter, Brittain said. Its distance from the star would be about the same distance that Saturn is from the sun.

The team used a technique called "spectro-astrometry," which enables small changes in the position of the carbon monoxide emission to be measured.

A source of excess carbon monoxide emission was detected that appears to vary in position and velocity. The varying position and velocity are consistent with orbital motion around the star.

More information: Astrophysical Journal paper - dx.doi.org/10.1088/0004-637X/791/2/136, Preprint on Arxiv: arxiv.org/abs/1409.0804

Astrophysical Journal Letters paper - iopscience.iop.org/2041-8205/766/1/L1/ , Preprint on Arxiv: arxiv.org/abs/1302.7122

Early Earth: A Battered, Hellish World with Water Oases for Life

Asteroids and comets that repeatedly smashed into the early Earth covered the planet's surface with molten rock during its earliest days, but still may have left oases of water that could have supported the evolution of life, scientists say.

The new study reveals that during the planet's infancy, the surface of the Earth was a hellish environment, but perhaps not as hellish as often thought, scientists added.

Earth formed about 4.5 billion years ago. The first 500 million years of its life are known as the Hadean Eon.

Although this time amounts to more than 10 percent of Earth's history, little is known about it, since few rocks are known that are older than 3.8 billion years old.

An artistic conception of the early Earth-moon system showing the Earth's surface after being bombarded with large impacts, causing magma extrusion on the surface, though some liquid water was retained. Image released on July 30, 2014. 

Credit: Simone Marchi

Earth's violent youth
For much of the Hadean, Earth and its sister worlds in the inner solar system were pummeled with an extraordinary number of cosmic impacts.

"It was thought that because of these asteroids and comets flying around colliding with Earth, conditions on early Earth may have been hellish," said lead study author Simone Marchi, a planetary scientist at the Southwest Research Institute in Boulder, Colorado.

Simone Marchi

This imagined hellishness gave the eon its name, Hadean comes from the word Hades, the lord of the underworld in Greek mythology.

However, in the past dozen years or so, a radically different picture of the Hadean began to emerge.

Analysis of minerals trapped within microscopic zircon crystals dating from this eon "suggested there was liquid water on the surface of the Earth back then, clashing with the previous picture that the Hadean was hellish," Marchi said.

This could explain why the evidence of the earliest life on Earth appears during the Hadean, maybe the planet was less inhospitable during that eon than previously thought.

This artist's illustration shows a close-up of the early Earth, revealing magma extrusion on the surface and the scars from severe cosmic bombardment. Image released on July 30, 2014.

Credit: Simone Marchi

Cosmic bombardment history
The exact timing and magnitude of the impacts that smashed Earth during the Hadean are unknown.

To get an idea of the effects of this bombardment, Marchi and his colleagues looked at the moon, whose heavily cratered surface helped model the battering that its close neighbour Earth must have experienced back then.

"We also looked at highly siderophile elements (elements that bind tightly to iron), such as gold, delivered to Earth as a result of these early collisions, and the amounts of these elements tells us the total mass accreted by Earth as the result of these collisions," Marchi said.

Prior research suggests these impacts probably contributed less than 0.5 percent of the Earth's present-day mass.

The researchers discovered that "the surface of the Earth during the Hadean was heavily affected by very large collisions, by impactors larger than 100 kilometers (60 miles) or so, really, really big impactors," Marchi said.

"When Earth has a collision with an object that big, that melts a large volume of the Earth's crust and mantle, covering a large fraction of the surface," Marchi added.

These findings suggest that Earth's surface was buried over and over again by large volumes of molten rock, enough to cover the surface of the Earth several times. This helps explain why so few rocks survive from the Hadean, the researchers said.

However, although these findings might suggest that the Hadean was a hellish eon, the researchers found that "there were time gaps between these large collisions," Marchi said.

"Generally speaking, there may have been something on the order of 20 or 30 impactors larger than 200 km (120 miles) across during the 500 million years of the Hadean, so the time between such impactors was relatively long," Marchi said.

Any water vapourised near these impacts "would rain down again," Marchi said, and "there may have been quiet tranquil times between collisions, there could have been liquid water on the surface."

The researchers suggested that life emerging during the Hadean was probably resistant to the high temperatures of the time.

Marchi and his colleagues detailed their findings in the July 31 issue of the journal Nature.

More Information: Widespread mixing and burial of Earth’s Hadean crust by asteroid impacts. - Authors: S. Marchi, W. F. Bottke, L. T. Elkins-Tanton, M. Bierhaus, K. Wuennemann, A. Morbidelli & D. A. Kring - doi:10.1038/nature13539

ESO ALMA Observatory: Young binary star system form planets with weird and wild orbits

This is ALMA data of HK Tau shown in a composite image with Hubble infrared and optical data. 

Credit: B. Saxton (NRAO/AUI/NSF); K. Stapelfeldt et al. (NASA/ESA Hubble)

Unlike our solitary Sun, most stars form in binary pairs, two stars that orbit a common center of mass.

Though remarkably plentiful, binaries pose a number of questions, including how and where planets form in such complex environments.

While surveying a series of binary stars with the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers uncovered a striking pair of wildly misaligned planet-forming disks in the young binary star system HK Tau.

These results provide the clearest picture ever of proto-planetary disks around a double star and could reveal important details about the birth and eventual orbit of planets in a multiple star system.

"ALMA has given us an unprecedented view of a main star and its binary companion sporting mutually misaligned protoplanetary disks," said Eric Jensen, an astronomer at Swarthmore College in Pennsylvania.

"In fact, we may be seeing the formation of a solar system that may never settle down."

The two stars in this system, which is located approximately 450 light-years from Earth in the constellation Taurus, are less than 5 million years old and separated by about 58 billion kilometers, or 13 times the distance of Neptune from the Sun.

This system's companion star, dubbed HK Tau, appears fainter to astronomers on Earth because its disk of dust and gas blocks out much of the starlight.

The disk itself, however, can be easily observed by the starlight that it scatters at optical and near-infrared wavelengths.

The key velocity data taken with ALMA that helped the astronomers determine that the disks in HK Tau were misaligned. 

The red areas represent material moving away from Earth and the blue indicates material moving toward us. 

Credit: NASA/JPL-Caltech/R. Hurt (IPAC); ALMA (ESO/NAOJ/NRAO)

The disk around the main star, HK Tau A, is tilted in such a way that the light from its host star shines through unobscured, making it difficult for astronomers to see the disk optically.

This is not a problem for ALMA, however, which can readily detect the millimeter-wavelength light emitted by the dust and gas that comprise the disk.

With its unprecedented resolution and sensitivity, ALMA was able to fully resolve the rotation of HK Tau A's disk for the first time.

This clearer picture enabled the astronomers to calculate that the disks were misaligned, meaning they were out of sync with the orbit of their host stars, by as much as 60 degrees or more.

Rachel Akeson

"This clear misalignment has given us a remarkable look at a young binary star system," said Rachel Akeson of the NASA Exoplanet Science Institute (NEXSCI) at the California Institute of Technology in Pasadena, California.

"Though there have been hints before that this type of misaligned system exists, this is the cleanest and most striking example."

Stars and planets form out of vast clouds of dust and gas. As material in these clouds contracts under gravity, it begins to rotate until most of the dust and gas falls into a flattened proto-planetary disk swirling around a growing central protostar.

Despite forming from a flat, regular disk, planets can end up in highly eccentric orbits, and may be misaligned with the star's equator.

One theory for how planets can migrate to these unusual orbits is that a binary companion star can influence them, but only if its orbit is initially misaligned with the planets.

This is an artist's impression of the misaligned protoplanetary disks around the binary stars in HK Tau. 

Credit: R. Hurt (NASA/JPL-Caltech/IPAC)

"Our results demonstrate that the necessary conditions exist to modify planetary orbits and that these conditions are present at the time of planet formation, apparently due to the binary formation process," noted Jensen.

"We can't rule other theories out, but we can certainly rule in that a second star will do the job."

Since ALMA can see the otherwise invisible dust and gas of protoplanetary disks, it allowed for never-before-seen views of this young binary system.

"Because we're seeing this in the early stages of formation with the protoplanetary disks still in place, we can see better how things are oriented," noted Akeson. "You can simply see gas better than you can see planets."

Looking forward, the researchers want to determine if this type of system is typical or not. They note that this is a remarkable individual case, but additional surveys are needed to determine if this sort of arrangement is common throughout our Galaxy.

More information: Nature DOI: 10.1038/nature13521

NASA MRO: Lava, not water, formed canyons on Mars

The Grand Canyon of Mars – Valles Marineris. Credit: NASA,Viking Project,USGS, CC BY

The canyon-like scars which line Mars' crust are seen by many as evidence for liquid water but a study now suggests that a different kind of fluid, one much less hospitable to life, may actually have carved these features.

On Mars, the most striking topography occurs around the equator. The planet's low latitudes are dominated by the Tharsis plateau, which hosts several towering volcanoes.


Not far off sits the solar system's largest, Olympus Mons. Near the Eastern fringe, however, things start to get deep.

There the land dives into a winding maze of valleys and river-like "outflow channels", the former including the 4000km-long Valles Marineris, the "Grand Canyon" of Mars, which exceeds its terrestrial namesake in every dimension.

These great gouges are widely thought to have been formed, at least in part, by flowing water. But according to recently published research, they could have had a very different genesis, linked to the volcanoes to the West.

Explosive erosion
A paper by Giovanni Leone of the Swiss Federal Institute of Technology, published in the Journal of Volcanology and Geothermal Research, suggests that the martian valleys and outflow channels were in fact formed mostly by lava flows, which erupted from the Tharsis plateau in the planet's distant past.

To draw this conclusion, Leone scrutinised thousands of images from NASA's Mars Reconnaissance Orbiter (MRO) spacecraft, which has been orbiting the planet since 2006.

This allowed him to map the floors of the equatorial valleys and outflow channels at an extremely high resolution of up to 25cm per pixel.

These images appear to show extensive lava flows draping the floors of many of the valleys and channels. Around 90% of the floors look to be covered either by lava or by lava-related landslides.

Valles Marineris 

Credit: G. Neukum/ESA/Mars Express/DLR, CC BY

The morphology of the lava flows Leone encountered suggest that the lava actually incised the valleys and channels in the first place.

The MRO images seem to show that channels formed by the freshly erupted lava were later deepened and widened by the passage of liquid rock.

This type of erosion, Leone argues, can explain the existence of the valleys and outflow channels without the need to invoke significant amounts of liquid water.

The valleys and outflow channels are believed to be many billion years old. Leone believes the lava would have been emitted by now-vanished volcanoes somewhere on the Tharsis plateau, forerunners of the region's (relatively juvenile) modern volcanoes.

Leone believes that every stage of this volcanic erosion process is visible in the MRO images. The first stage, he concludes, can be seen in the locations closest to today's Tharsis volcanoes, at the western end of Valles Marineris. Here lava tunnels seem to have collapsed, forming "pit chains" – long curvilinear depressions in the crust.

Further east, where the terrain deepens, the pit chains seem to have been further eroded, by the injection of yet more lava, into more extensive channels – first into "fossae" and later into larger "chasmata".

The MRO images showed relatively little evidence for the past presence of liquid water in the valleys and outflow channels, which can be inferred by the presence of "light toned deposits" in the images. This, Leone believes, adds further weight to the theory that these features are igneous in origin.

Pushy black holes stop elliptical galaxies from forming stars

Multi-wavelength view of the elliptical galaxy NGC 5044. Credit: Digitised Sky Survey /NASA Chandra /Southern Observatory for Astrophysical Research/Very Large Array. 

Contradicting past theories, cold gas has been found in abundance in some elliptical galaxies—showing that there must be some other explanation why these types of galaxies don't form new stars.

Astronomers believe that the jets from supermassive black holes in these galaxies' center must push around the gas and prevent stars from forming.

Researchers spotted the gas for the first time using old data from the recently retired Herschel space observatory, which was able to peer well into the infrared—where it spotted carbon ions and oxygen atoms.

This find stands against the previous belief that these galaxies were "red and dead", referring to their physical appearance and the fact that they form no new stars.

"We looked at eight giant elliptical galaxies that nobody had looked at with Herschel before and we were delighted to find that, contrary to previous belief, six out of eight abound with cold gas", stated Norbert Werner, a researcher at Stanford University in California who led the study.

"These galaxies are red, but with the giant black holes pumping in their hearts, they are definitely not dead," added Werner.

Previously, scientists thought that the galaxies got rid of their cold gas or had used it all up during a burst of earlier star formation.

With cold gas found in the majority of the sample, researchers then used other observatories to try to find warmer gas up to tens of millions of Kelvin (or Fahrenheit or Celsius).

NGC 1399, an elliptical galaxy about 65 million light years from Earth. Credit: NASA, Chandra

X-ray information from NASA's Chandra X-ray Observatory revealed that there is hot gas cooling in six of the eight galaxies, but not in the remaining two of the sample.

"This is consistent with theoretical expectations: once cooled, the hot gas would become the warm and cold gas that are observed at longer wavelengths.

However, in these galaxies the cooling process somehow stopped, and the cold gas failed to condense and form stars," the European Space Agency stated.

"While the six galaxies with plenty of cold gas harbour moderately active black holes at their centres," ESA added, "the other two show a marked difference."

"In the two galaxies without cold gas, the central black holes are accreting matter at frenzied pace, as confirmed by radio observations showing powerful jets of highly energetic particles that stem from their cores."

More information: N. Werner, J. B. R. Oonk, M. Sun, P. E. J. Nulsen, S. W. Allen, R. E. A. Canning, A. Simionescu, A. Hoffer, T. Connor, M. Donahue, A. C. Edge, A. C. Fabian, A. von der Linden, C. S. Reynolds, and M. Ruszkowski. "The origin of cold gas in giant elliptical galaxies and its role in fuelling radio-mode AGN feedback." MNRAS first published online February 24, 2014 DOI: 10.1093/mnras/stu006