Category: Solar System

ALMA photographs debris ring around young star Formalhaut

Disk’s chemical composition is strangely similar to that of comets in our solar system.

Using the Atacama Large Millimeter/submillimeter Array (ALMA), a team of scientists has captured the first ever complete image of a ring of icy dust surrounding the young star Formalhaut.

The complete millimeter-wavelength of the ring reveals it to be a well-defined structure of dust and gas with a composition surprisingly similar to that of comets in our solar system.

Located approximately 25 light years away, Formalhaut has a planet initially discovered in 2008. It is one of only about 20 nearby star systems whose orbiting planets have been directly imaged.

The debris ring is approximately two billion kilometers wide at a distance of about 20 billion kilometers from the star.

At about 440 million years old, the system is just one-tenth as old as our solar system and may be experiencing its own version of the Late Heavy Bombardment that ours underwent about four billion years ago, a period characterized by asteroids and comets left over from the system’s formation repeatedly slamming into its planets.

Impacts of exocomets crashing into one another in the outer regions of the Formalhaut system likely created the debris ring, scientists believe.

A previous attempt to image the debris ring with ALMA in 2012, when the telescope was still in the process of being built, revealed just half of the disk but already hinted at chemical similarities with our solar system’s comets.

Now, “ALMA has given us this staggeringly clear image of a fully formed debris disk. We can finally see the well-defined shape of the disk, which may tell us a great deal about the underlying planetary system responsible for its highly distinctive appearance,” noted Meredith MacGregor of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA, and lead author of two papers on the subject scheduled for publication in the Astrophysical Journal.

With the help of computer modeling, the researchers were able to pinpoint the exact location and shape of the disk. Based on its narrow shape, they believe it to be the product of the gravitational influence of planets orbiting the star.

Interestingly, the debris disk contains approximately the same high levels of both carbon monoxide and carbon dioxide found in our own solar system’s comets.

Impacts among numerous exocomets could be releasing these gases.

“This chemical kinship may indicate a similarity in comet formation conditions between the outer reaches of this planetary system and our own,” noted Luca Matra of the University of Cambridge in the UK and lead author of one of the two papers on the discovery.

 

 

Organics on Ceres are likely native

Distribution of organic materials is inconsistent with delivery by comets or asteroids.

Organic materials found on dwarf planet Ceres by NASA’s Dawn spacecraft are likely native to the small world, according to research by scientists at the Southwest Research Institute (SwRI) in San Antonio, Texas.

The researchers specifically focused on a localized region of organic-rich material near Ernutet Crater, a 32-mile- (52-km-) wide opening on Ceres’ northern hemisphere.

Two origins are theorized for these organic materials or carbon-based compounds. They could have been brought to Ceres by impacting asteroids or comets after the dwarf planet formed 4.5 billion years ago, or they could have been synthesized through an internal process on the dwarf planet.

Located at the boundary of the solar system’s rocky planets and gas giants, Ceres is composed of clays and both sodium- and ammonium-carbonates, all of which indicate the small planet underwent complex chemical evolution.

“Earlier research that focused on the geology of the organic-rich region on Ceres were inconclusive about their origin,” explained Simone Marchi, an SwRI principal investigator who presented the findings Wednesday at a press conference held at the American Astronomical Society’s 49th Division for Planetary Sciences Meeting in Provo, Utah.

“Recently, we more fully investigated the viability of organics arriving via an asteroid or comet impact.”

Through computer simulations, scientists considered a range of variables, including the sizes and velocities of impacting objects.

The simulations indicated comet-like objects that hit Ceres at very high velocities would have had their organic materials destroyed by a mechanism known as shock compression, in which total pressure is lost.

Impacting asteroids, which would have lower velocities, would hold onto between 20 and 30 percent of their organic materials, depending on the angle at which they hit.

However, the localized distribution of organic materials on Ceres is not consistent with what would be seen if those organics had been delivered by small asteroids from the belt between Mars and Jupiter.

While researchers admit they still do not have all the pieces of the puzzle when it comes to Ceres’ organics, “These findings indicate that the organics are likely to be native to Ceres,” Marchi said.

Ceres is geologically differentiated, with a rocky core and icy mantle, and may harbor a subsurface ocean that could possibly be home to microbial life.

Asteroid that will fly close to Earth on Thursday poses no danger

Astronomers will have opportunity to observe a complete rotation of the object in just one night.

An asteroid discovered five years ago will come within 31,000 miles (50,000 km) of Earth on Thursday, October 12, but poses no impact danger to our planet.

Just a week after its discovery by Hawaii’s Pan-STARRS, asteroid 2012 TC4 passed within 58,900 miles (94,800 km) of Earth, and observation over time indicates it has made many such approaches in the past.

Approximately the size of the meteor that hit Chelyabinsk, Russia, in 2013, with a diameter ranging from 26 to 85 feet (8 to 26 meters), 2012 TC4 has an elongated shape, rotates at a high speed, and orbits the Sun every 1.67 years. Its distance from the Sun is around 1.4 AU or astronomical units, with one AU equal to the average Earth-Sun distance or 93 million miles.

“There is no hazard in its upcoming pass or anytime in the near future,” said Alan Harris, formerly a researcher at NASA’s Jet Propulsion Laboratory (JPL).

Early calculations conducted this summer by JPL led scientists to believe 2012 TC4 could come as close as 4,200 miles (6,800 km). Because these calculations were based on just seven days of tracking the asteroid, later studies by the European Space Agency’s (ESA) Oliver Hainaut, Detlef Koschny, and Marco Micheli using the European Southern Observatory (ESO) concluded its approach would not be that close.

According to JPL, “The new calculations indicate that TC4 will fly safely past our planet on Oct. 12, at a distance of about 43,500 km (27,000 miles) above the surface, or about one-eighth of the distance to the Moon.”

Astronomers around the world will be able to observe the asteroid, which will have a brightness of approximately magnitude 14, when it makes its close approach at 5:41 UTC (1:41 AM EDT) on Thursday.

Because 2012 TC4 has such a fast rotation rate, observers should be able to watch a full rotation in just one night, Harris said.

The International Asteroid Warning Network, a UN-sanctioned organization that focuses on collecting data on asteroids that pose potential threats to Earth, will also be following it.

While there is no chance of 2012 TC4 hitting the Earth, even if it did impact, it is too small to cause major damage and would likely land harmlessly over one of Earth’s oceans, Harris noted.

Milky Way disk spans 200,000 light years

Metal-rich stars have been discovered far beyond what was thought to be the galactic disk’s boundary.

The Milky Way’s disk, the flat, central region of the galaxy that contains mostly young stars, gas, and dust within the structure of its spiral arms, measures 200,000 light years across, making it significantly larger than initially thought, according to a new study.

Previous studies calculated the galaxy’s diameter at 100,000 to 160,000 light years.

In the most recent study, scientists analyzed data collected by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) on the spectra of stars in the galactic disk.

A star’s spectrum breaks down its light into different colors whose patterns reveal the specific elements present within that star.

For this study, researchers analyzed the metallicities or amounts of heavy elements, within disk stars and were surprised to find stars with high metallicities beyond the region they believed to be the boundary of the galaxy’s disk.

“We have shown that there is an appreciable fraction of stars with higher metallicity, characteristic of disk stars, further out than the previously assumed limit on the radius of the galaxy disk,” said Carlos Allende of the Astrophysics Institute of the Canary Islands (IAC).

Although spiral disks are usually thin, that is not the case for the Milky Way. “The disk of our galaxy is huge, around 200,000 light years in diameter,” stated Martin Lopez-Corredoira, also of the Astrophysics Institute.

The newly-discovered metal-rich disk stars are located about three times further and possibly as far as four times further from the galactic center than our Sun.

One light year is equal to approximately six trillion miles (10 trillion km). A spacecraft traveling at the speed of light would take 200,000 years to cross from one end of the galaxy to the other.

A paper detailing the study’s findings has been published in the journal Astronomy and Astrophysics.

Astronomers continue search for elusive Planet Nine

All circumstantial evidence points towards a new planet, but detecting it remains near impossible.

Many astronomers remain convinced that they will one day locate the mysterious Planet Nine, the hypothetical body thought to be hiding far beyond Neptune. “Every time we take a picture,” says astronomer Surhud More, “there is a possibility that Planet Nine exists in the shot.” Yet, despite all the circumstantial evidence for its existence, no telescope has been able to spot it.

The first evidence for Planet Nine transpired in 2014, when astronomers discovered a handful of mini ice-worlds beyond the Kuiper belt following similar paths, writes Charlie Wood for Quanta Magazine. According to Scott Sheppard, an astronomer at the Carnegie Institution for Science, “if things are in the same orbit, then something’s pushing them.” Astronomical calculations predict that the light coming back from Planet Nine would appear more than 1 million times weaker, creating a “brick wall” to any sightings of it, according to astronomer Kevin Luhman. Teams led by Michael Brown at the California Institute of Technology, and Sheppard are searching for the planet with the Subaru telescope in Hawaii. Subaru’s wide field of view can sour a potential search area the size of 4,000 full moons. Still, factors like light pollution in the Milky Way, or the glare of a bright star can keep the planet hidden.

Some scientists are suggesting backup plans like searching for the heat glow emitted by the planet, which could be detected by current telescopes in Antarctica and Chile. Others wonder if signs of Planet Nine might lie buried in today’s data sets by just slightly affecting the paths of known planets. As astrophysicist Matthew Holman puts it, “if you put a planet in” the outer solar system, “the fit would be better.”

Lunar meteorite suggests there could be water on the moon

A meteorite from the moon suggests that there is water on Earth’s natural satellite.

A lunar meteorite uncovered in Africa 13 years ago may hold a mineral that only forms in the presence of water, according to a new study published in the journal Science Advances.

The space rock — known as meteorite NWA2727 — is important because it is seemingly hard evidence that there is in fact water on or below the surface of the moon.

To make this discovery, scientists from Tohoku University analyzed the meteorite and found that it contained the substance moganite. As the mineral only forms in the presence of water, and as the meteorite landed in a desert, there must be some frozen liquid on the moon.

Moganite is commonly found within the cracks of rocks and appears through brecciation, where older rocks form a large mass. However, that process can only happen in the presence of water.

“For the first time, we can prove that there is water ice in the lunar material,” lead author Masahiro Kayama, a researcher at Tohoku University told Space.com. “In a moganite, there is less water, because moganite forms from the evaporation of water. That’s the case on the surface of the moon. But in the subsurface, much water remains as ice, because it’s protected from the sunlight.”

Though the team is not sure, they believe the water on the moon likely got there from asteroids and comets some three billion years ago. From there, they postulate the liquid became trapped in the surface and cooled. Then, another rock hit the moon and sent the water-filled rocks down to Earth.

The presence of moganite from a meteor that landed in a desert does suggest water on the moon, but it is not definitive evidence. Further missions need to collect samples from the lunar surface. It may also help to look back at older missions as well.

“It also highlights the need to study Apollo samples with modern analytical techniques,” said Noah Petro, a lunar geologist with NASA who was not involved in the research, according to Gizmodo.

In addition, scientists are not sure where water would sit on the moon or how much exists. Even if they do find water, nobody is sure how they would manage to extract or use it.

New Horizons team to observe stellar occultation from Senegal and Colombia

Data from distant observation will help guide plans for New Year’s flyby.

NASA’s New Horizons team is preparing to view the spacecraft’s second target, Kuiper Belt Object (KBO) Ultima Thule, pass in front of a star less than five months ahead of its scheduled New Year’s flyby.

When Ultima Thule, also known as 2014 MU69, passes in front of or occults a star on August 4, mission scientists will observe the event from two 18.5-mile (30-km) locations in Senegal and Colombia identified by data from the Hubble Space Telescope (HST) as the places on Earth where the KBO will cast its shadow.

Last summer, the mission team observed three occultations, when Ultima Thule passed in front of three separate stars in June and July. Observing from Patagonia and Argentina, the team successfully viewed the event from five separate sites in spite of extreme winter weather.  Data obtained from the event helped mission scientists learn more about the KBO and set the flyby distance at 2,175 miles (3,500 km).

As then, scientists will set up telescopes on various locations along the shadow’s path to observe the occultation, which this year will be viewed from Senegal and Colombia.

“Gathering occultation data is an extremely difficult task. We are literally at the limit of what we can detect with Hubble, and the amount of computer processing needed to resolve the data is staggering,” said Marc Buie of the Southwest Research Institute (SwRI), who is leading the observation team, as he did last year.

“Our team of almost 50 researchers using telescopes in Senegal and Colombia are certainly hoping lightning will strike twice, and we’ll see more blips in the stars. This occultation will give us hints about what to expect at Ultima Thule and help us refine our flyby plans,” he explained.

The observation team is grateful to the governments of Senegal and Colombia, US embassies in both countries, and the French, Senegalese, Colombian, and Mexican astronomy communities for their support in the project, which requires detailed and painstaking preparations.

Ultima Thule is located more than four billion miles from Earth. Like other Kuiper Belt Objects, it is made of pristine materials unchanged from the time the solar system formed.

Based on last year’s occultations, mission scientists determined the KBO is either a binary system of two objects that orbit close to one another or actually touch one another or a two-lobed object. Its size is estimated at 20 miles (30 km) long if it is a single object or nine to twelve miles (15-20 km) long each if it is two objects.

“If the team is successful, the results will help guide our planning for the flyby,” said New Horizons principal investigator Alan Stern, also of SwRI.

 

 

New Horizons takes first picture of distant second target

Spacecraft’s photographs will help mission team refine the path to Ultima Thule.

More than four months before its scheduled flyby of Kuiper Belt Object (KBO) Ultima Thule, NASA’s New Horizons spacecraft captured its first image of its small second target.

The spacecraft’s Long Range Reconnaissance Imager (LORRI) photographed the dim KBO on August 16 from a distance of more than 100 million miles, surprising mission scientists, who did not expect any images of the object until September.

LORRI took a total of 48 images of the faint KBO against a dense background of stars, which it transmitted back to Earth via NASA’s Deep Space Network (DSN).

All previous images of Ultima Thule were either captured by the Hubble Space Telescope (HST) or obtained via ground-based telescopes when the KBO passed in front of a background star, casting a shadow.

Observations made between now and the January 1, 2019, flyby are of critical importance to the mission team, who will use them to refine the probe’s path to its closest approach, which will occur at 12:33 AM EST on New Year’s Day.

This initial detection confirms Ultima Thule is at the exact location where mission scientists expected it to be and indicates their calculations of its orbit are correct.

“Our team worked hard to determine if Ultima was detected by LORRI at such a great distance, and the result is a clear yes,” New Horizons principal investigator Alan Stern of the Southwest Research Institute (SwRI) in Boulder, Colorado, emphasized.  “We now have Ultima in our sights from much farther out than once thought possible. We are on Ultima’s doorstep, and an amazing exploration awaits.”

Hal Weaver of the Johns Hopkins University Applied Physics Laboratory (JHUAPL), New Horizons project scientist and LORRI principal investigator, described the challenge mission scientists faced in directing the spacecraft to photograph Ultima Thule from such a great distance.

“The image field is extremely rich with background stars, which makes it difficult to detect faint objects. It really is like finding a needle in a haystack. In these first images, Ultima appears only as a bump on the side of a background star that’s roughly 17 times brighter, but Ultima will be getting brighter–and easier to see–as the spacecraft gets closer.”

Located around one billion miles beyond Pluto, Ultima Thule will be the most distant object ever visited by a spacecraft and the first small KBO studied up close. New Horizons will break its own record in the flyby, set when it explored Pluto in July 2015.

Other records set by the spacecraft include taking the most distant photo of the Sun, imaging a galactic open cluster, and capturing distant images of two remote KBOs.

NASA releases image, video, of Saturn’s auroras

Data from Hubble and Cassini reveal remarkable similarities with Earth’s auroras.

Last year, while the Cassini spacecraft was still orbiting Saturn, NASA’s Hubble Space Telescope (HST) captured a stunning view of the planet’s northern aurora, which, after being combined with Cassini data, was just released as an image and video.

When Saturn experienced its summer solstice on May 24, 2017, meaning its north pole was tilted toward the Sun, both Hubble and Cassini observed and measured the northern aurora.

Although the aurora appears blue, it actually glows in ultraviolet wavelengths, which can only be seen from space. When hydrogen gas at the north pole interacts with energetic electrons generated by the planet’s powerful magnetic field, intense auroras are created. Because Saturn rotates rapidly on its axis, with a Saturn “day” taking just 11 hours, the auroras’ appearances constantly change.

The actual image and video released by NASA are composites that include images of the aurora taken in early 2018 and transformation of the May 2017 photos from ultraviolet wavelengths to visible light.

One of Cassini’s last images before it plunged into Saturn’s atmosphere last September revealed a never-previously-seen auroral storm produced by interactions between plasma in the planet’s magnetosphere and its upper atmosphere.

The spacecraft also tracked an arc-shaped structure within the aurora as it grew and eventually disappeared.

In a paper published in the journal Geophysical Research Letters, Cassini scientists noted the aurora bears a striking resemblance to auroras seen on Earth and attributed its creation to the solar wind, a stream of charged particles emanating from the Sun.

From the combined observations of both Hubble and Cassini, scientists learned that Saturn’s aurora strongly peaked just prior to the planet’s midnight, then did so again around dawn. Both midnight and dawn auroral spikes also occur on Earth.

Japanese scientists determine age of asteroid Itokawa

Analysis indicates it came from large ancient parent body later destroyed in an impact.

Japanese scientists who analyzed samples taken from asteroid Itokawa and returned to Earth in 2010 by the Hayabusa probe determined the asteroid came from a parent body that formed 4.6 billion years ago, at the dawn of the solar system.

That body was destroyed in an impact with another asteroid approximately 1.5 billion years ago. Remnants from that impact stuck together over time, producing Itokawa.

Between 100,000 and 400,000 years ago, Itokawa was ejected from the asteroid belt between Mars and Jupiter and propelled into its current near-Earth orbit, where asteroids usually do not survive very long.

Scientists estimate Itokawa will either break apart or hit the Earth within the next million years.

Hayabusa was launched by the Japan Aerospace and Exploration Agency (JAXA) in 2003 with the goal of studying the near-Earth asteroid and returning a sample of it to Earth for analysis.

While Itokawa itself poses no current threat to Earth, near-Earth asteroids could potentially pose hazards to our planet. Understanding their formation and evolution processes is important for scientists in terms of both predicting and addressing potential impacts.

The Japanese scientists, including some from Osaka University, looked at tiny, phosphate-rich minerals found in the particles taken from Itokawa’s surface. They then measured the level of uranium inside the particles and determine how much of it had broken down into lead, a process that always occurs at the same pace. This allowed them to put together the asteroid’s history.

From this analysis, the scientists learned that the asteroid’s phosphate minerals crystallized during a time when the parent body experienced shock from an impacting object.

Another discovery the researchers made is that Itokawa’s mineralogy and geochemistry match those of low-iron, low-metal chondrite meteorites that often land on Earth. Chondrites are rocky, non-metallic meteorites that were never modified by melting of their parent bodies.

A paper detailing the scientists’ findings has been published in the journal Scientific Reports.