Month: February 2019

Crater Counts On Pluto, Charon Show Small Kuiper Belt Objects Surprisingly Rare

Using New Horizons data from the Pluto-Charon flyby in 2015, a Southwest Research Institute-led team of scientists have indirectly discovered a distinct and surprising lack of very small objects in the Kuiper Belt. The evidence for the paucity of small Kuiper Belt objects (KBOs) comes from New Horizons imaging that revealed a dearth of small craters on Pluto’s largest satellite, Charon, indicating that impactors from 300 feet to 1 mile (91 meters to 1.6 km) in diameter must also be rare.

The Kuiper Belt is a donut-shaped region of icy bodies beyond the orbit of Neptune. Because small Kuiper Belt objects were some of the “feedstock” from which planets formed, this research provides new insights into how the solar system originated. This research was published in the March 1 issue of the journal Science.

“These smaller Kuiper Belt objects are much too small to really see with any telescopes at such a great distance,” said SwRI’s Dr. Kelsi Singer, the paper’s lead author and a co-investigator of NASA’s New Horizons mission. “New Horizons flying directly through the Kuiper Belt and collecting data there was key to learning about both large and small bodies of the Belt.”

“This breakthrough discovery by New Horizons has deep implications,” added the mission’s principal investigator, Dr. Alan Stern, also of SwRI. “Just as New Horizons revealed Pluto, its moons, and more recently, the KBO nicknamed Ultima Thule in exquisite detail, Dr. Singer’s team revealed key details about the population of KBOs at scales we cannot come close to directly seeing from Earth.”

Craters on solar system objects record the impacts of smaller bodies, providing hints about the history of the object and its place in the solar system. Because Pluto is so far from Earth, little was known about the dwarf planet’s surface until the epic 2015 flyby. Observations of the surfaces of Pluto and Charon revealed a variety of features, including mountains that reach as high as 13,000 feet (4 km) and vast glaciers of nitrogen ice. Geologic processes on Pluto have erased or altered some of the evidence of its impact history, but Charon’s relative geologic stasis has provided a more stable record of impacts.

“A major part of the mission of New Horizons is to better understand the Kuiper Belt,” said Singer, whose research background studying the geology of the icy moons of Saturn and Jupiter positions her to understand the surface processes seen on KBOs. “With the successful flyby of Ultima Thule early this year, we now have three distinct planetary surfaces to study. This paper uses the data from the Pluto-Charon flyby, which indicate fewer small impact craters than expected. And preliminary results from Ultima Thule support this finding.”

Typical planetary models show that 4.6 billion years ago, the solar system formed from the gravitational collapse of a giant molecular cloud. The Sun, the planets and other objects formed as materials within the collapsing cloud clumped together in a process known as accretion. Different models result in different populations and locations of objects in the solar system.

“This surprising lack of small KBOs changes our view of the Kuiper Belt and shows that either its formation or evolution, or both, were somewhat different than those of the asteroid belt between Mars and Jupiter,” said Singer. “Perhaps the asteroid belt has more small bodies than the Kuiper Belt because its population experiences more collisions that break up larger objects into smaller ones.”

Using Stardust Grains, Scientists Build New Model For Nova Eruptions

What do tiny specks of silicon carbide stardust, found in meteorites and older than the solar system, have in common with pairs of aging stars prone to eruptions?

A collaboration between two Arizona State University scientists — cosmochemist Maitrayee Bose and astrophysicist Sumner Starrfield, both of ASU’s School of Earth and Space Exploration — has uncovered the connection and pinpointed the kind of stellar outburst that produced the stardust grains.

Their study has just been published in The Astrophysical Journal.

The microscopic grains of silicon carbide — a thousand times smaller than the average width of a human hair — were part of the construction materials that built the Sun and planetary system. Born in nova outbursts, which are repeated cataclysmic eruptions by certain types of white dwarf stars, the silicon carbide grains are found today embedded in primitive meteorites.

“Silicon carbide is one of the most resistant bits found in meteorites,” Bose said. “Unlike other elements, these stardust grains have survived unchanged from before the solar system was born.”

Violent birth

A star becomes a nova — a “new star” — when it suddenly brightens by many magnitudes. Novae occur in pairs of stars where one star is a hot, compact remnant called a white dwarf. The other is a cool giant star so large its extended outer atmosphere feeds gas onto the white dwarf. When enough gas collects on the white dwarf, a thermonuclear eruption ensues, and the star becomes a nova.

Although powerful, the eruption doesn’t destroy the white dwarf or its companion, so novae can erupt over and over, repeatedly throwing into space gas and dust grains made in the explosion. From there the dust grains merge with clouds of interstellar gas to become the ingredients of new star systems.

The Sun and solar system were born about 4.6 billion years ago from just such an interstellar cloud, seeded with dust grains from earlier stellar eruptions by many different kinds of stars. Almost all the original grains were consumed in making the Sun and planets, yet a tiny fraction remained. Today these bits of stardust, or presolar grains, can be identified in primitive solar system materials such as chondritic meteorites.

“The key that unlocked this for us was the isotopic composition of the stardust grains,” Bose said. Isotopes are varieties of chemical elements that have extra neutrons in their nuclei. “Isotopic analysis lets us trace the raw materials that came together to form the solar system.”

She added, “Each silicon carbide grain carries a signature of the isotopic composition of its parent star. This provides a probe of that star’s nucleosynthesis — how it made elements.”

Bose collected published data on thousands of grains, and found that nearly all the grains grouped naturally into three main categories, each attributable to one kind of star or another.

But there were about 30 grains that couldn’t be traced back to a particular stellar origin. In the original analyses, these grains were flagged as possibly originating in nova explosions.

But did they?

Making stardust

As a theoretical astrophysicist, Starrfield uses computer calculations and simulations to study various kinds of stellar explosions. These include novae, recurrent novae, X-ray bursts, and supernovae.

Working with other astrophysicists, he was developing a computer model to explain the ejected materials seen in the spectrum of a nova discovered in 2015. Then he attended a colloquium talk given by Bose before she had joined the faculty.

“I would not have pursued this if I hadn’t heard Maitrayee’s talk and then had our follow-up discussion,” he said. That drew him deeper into the details of nova eruptions in general and what presolar grains could say about these explosions that threw them into space.

A problem soon arose. “After talking with her,” Starrfield said, “I discovered our initial way of solving the problem was not agreeing with either the astronomical observations or her results.

“So I had to figure out a way to get around this.”

He turned to multidimensional studies of classical nova explosions, and put together a wholly new way of doing the model calculations.

There are two major composition classes of nova, Starrfield said. “One is the oxygen-neon class which I’ve been working on for 20 years. The other is the carbon-oxygen class which I had not devoted as much attention to.” The class designations for novae come from the elements seen in their spectra.

“The carbon-oxygen kind produce a lot of dust as part of the explosion itself,” Starrfield said. “The idea is that the nova explosion reaches down into the white dwarf’s carbon-oxygen core, bringing up all these enhanced and enriched elements into a region with high temperatures.”

That, he said, can drive a much bigger explosion, adding, “It’s really messy. It shoots out dust in tendrils, sheets, jets, blobs, and clumps.”

Starrfield’s calculations made predictions of 35 isotopes, including those of carbon, nitrogen, silicon, sulfur, and aluminum, that would be created by the carbon-oxygen nova outbursts.

It turned out that getting the right proportion of white dwarf core material and accreted material from the companion star was absolutely necessary for the simulations to work. Bose and Starrfield then compared the predictions with the published compositions of the silicon carbide grains.

This led them to a somewhat surprising conclusion. Said Bose, “We found that only five of the roughly 30 grains could have come from novae.”

While this may seem a disappointing result, the scientists were actually pleased. Bose said, “Now we have to explain the compositions of the grains that didn’t come from nova outbursts. This means there’s a completely new stellar source or sources to be discovered.”

And looking at the larger picture, she added, “We have also found that astronomical observations, computer simulations, and high-precision laboratory measurements of stardust grains are all needed if we want to understand how stars evolve. And this is exactly the kind of interdisciplinary science that the school excels at.”

My Schools Apex Fun Run is Back

Hi Everybody, It’s Alexa Battros and my little sister Sophia. Most of you know my dad Mitch Battros from his Science Of Cycles research. I’m his oldest daughter and I will be 11 yrs old next month. My sister turned 6 last month.

I’m participating in my school Hidden Forest Fun Run and I would love your support. My run event was canceled due to rain and is rescheduled for tomorrow Feb. 25th – so I’m hoping you can help right away.

I have a request… would you please pledge me a dollar amount per Lap? I will complete between 26 and 36 Laps, with 36 being the most. You can pledge $1, $3, $5 per Lap, or any other flat donation amount.

To make a pledge, just click here: Hidden Forest Fun Run . Donations will be used for my school’s Laptop Carts & Technology Improvements.

Thank you again for helping my cause!

Sincerely,
Alexa and Sophia Battros

7.5 Magnitude Earthquake Strikes Ecuador-Peru Boarder

A powerful earthquake struck eastern Ecuador early Friday, sending tremors for miles through a sparsely populated area and into neighboring Peru and Colombia. The quake hit at an intermediate depth of about 82 miles, the U.S. Geological Survey said.

The earthquake struck at 5:17 a.m. local time. Its epicenter was 71 miles east-southeast of Palora, far inland and distant from Ecuador’s main highways that run along its mountain ranges.

“The Peru-Chile Trench is an area that hosts large earthquakes quite regularly,” the USGS said. It added that 15 other intermediate-depth earthquakes have occurred within 310 miles of the epicenter in the past 100 years.

Earth’s Atmosphere Stretches Out To The Moon – And Beyond

The gaseous layer that wraps around Earth reaches up to 630,000 kilometers away, or 50 times the diameter of our planet, according to a new study based on observations by the ESA/NASA Solar and Heliospheric Observatory, SOHO, and published in AGU’s Journal of Geophysical Research: Space Physics.

“The moon flies through Earth’s atmosphere,” says Igor Baliukin of Russia’s Space Research Institute, lead author of the paper presenting the results. “We were not aware of it until we dusted off observations made over two decades ago by the SOHO spacecraft.”

Where our atmosphere merges into outer space, there is a cloud of hydrogen atoms called the geocorona. One of the spacecraft instruments, SWAN, used its sensitive sensors to trace the hydrogen signature and precisely detect how far the very outskirts of the geocorona are. These observations could be done only at certain times of the year, when the Earth and its geocorona came into view for SWAN.

For planets with hydrogen in their exospheres, water vapor is often seen closer to their surface. That is the case for Earth, Mars and Venus.

“This is especially interesting when looking for planets with potential reservoirs of water beyond our solar system,” explains Jean-Loup Bertaux, co-author and former principal investigator of SWAN.

The first telescope on the moon, placed by Apollo 16 astronauts in 1972, captured an evocative image of the geocorona surrounding Earth and glowing brightly in ultraviolet light.

“At that time, the astronauts on the lunar surface did not know that they were actually embedded in the outskirts of the geocorona,” says Jean-Loup.

Cloud of hydrogen
The sun interacts with hydrogen atoms through a particular wavelength of ultraviolet light called Lyman-alpha, which the atoms can both absorb and emit. Since this type of light is absorbed by Earth’s atmosphere, it can only be observed from space.

Thanks to its hydrogen absorption cell, the SWAN instrument could selectively measure the Lyman-alpha light from the geocorona and discard hydrogen atoms further out in interplanetary space.

The new study revealed that sunlight compresses hydrogen atoms in the geocorona on Earth’s dayside, and also produces a region of enhanced density on the night side. The denser dayside region of hydrogen is still rather sparse, with just 70 atoms per cubic centimeter at 60,000 kilometers above Earth’s surface, and about 0.2 atoms at the moon’s distance.

“On Earth we would call it vacuum, so this extra source of hydrogen is not significant enough to facilitate space exploration,” says Igor. The good news is that these particles do not pose any threat for space travelers on future crewed missions orbiting the moon.

“There is also ultraviolet radiation associated to the geocorona, as the hydrogen atoms scatter sunlight in all directions, but the impact on astronauts in lunar orbit would be negligible compared to the main source of radiation – the sun,” says Jean-Loup Bertaux.

On the down side, the Earth’s geocorona could interfere with future astronomical observations performed in the vicinity of the moon.

“Space telescopes observing the sky in ultraviolet wavelengths to study the chemical composition of stars and galaxies would need to take this into account,” adds Jean-Loup.
The power of archives

Launched in December 1995, the SOHO space observatory has been studying the sun, from its deep core to the outer corona and the solar wind, for over two decades. The satellite orbits around the first Lagrange point (L1), some 1.5 million kilometers from Earth towards the sun.

This location is a good vantage point to observe the geocorona from outside. SOHO’s SWAN instrument imaged Earth and its extended atmosphere on three occasions between 1996 and 1998.

Jean-Loup and Igor’s research team in Russia decided to retrieve this data set from the archives for further analysis. These unique views of the whole geocorona as seen from SOHO are now shedding new light on Earth’s atmosphere.

“Data archived many years ago can often be exploited for new science,” says Bernhard Fleck, ESA SOHO project scientist. “This discovery highlights the value of data collected over 20 years ago and the exceptional performance of SOHO.”

Cosmic Dust Forms On Supernovae Blasts

Scientists claim to have solved a longstanding mystery as to how cosmic dust, the building blocks of stars and planets, forms across the Universe.

Cosmic dust contains tiny fragments or organic material and is spread out across the Universe. The dust is primarily formed in stars and is then blown off in a slow wind or a massive star explosion.

Up until now, astronomers have had little understanding as to why so much cosmic dust exists in the interstellar medium, with theoretical estimates suggesting it should be obliterated by supernova explosions.

A supernova is an event that occurs upon the violent death of a star and is one of the most powerful events in the Universe, producing a shockwave which destroys almost anything in its path.

Yet new research published in the Monthly Notices of the Royal Astronomical Society has observed the survival of cosmic dust around the closest supernova explosion detected to us, Supernova 1987A.

Observations using NASA’s research aircraft, the Stratospheric Observatory for Infrared Astronomy (SOFIA), have detected cosmic dust in a distinctive set of rings that form part of Supernova 1987A.

The results seem to suggest that there is rapid growth of cosmic dust within the rings, leading the team to believe that dust may actually be re-forming after it is destroyed in the wake of a supernova blast wave.

This immediacy – that the post-shock environment might be ready to form or re-form dust – had never been considered before, and may be pivotal in fully understanding how cosmic dust is both created and destroyed.

“We already knew about the slow-moving dust in the heart of 1987A,” said Dr. Mikako Matsuura, lead author on the paper from the School of Physics and Astronomy.

“It formed from the heavy elements created in the core of the dead star. But the SOFIA observations tell us something completely new.”

Cosmic dust particles can be heated from tens to hundreds of degrees causing them to glow at both infrared and millimeter wavelengths. Observations of millimeter-wave dust emission can generally be carried out from the ground using telescopes; however, observations in the infrared are almost impossible to interference from the water and carbon dioxide in the Earth’s atmosphere.

By flying above most of the obscuring molecules, SOFIA provides access to portions of the infrared spectrum not available from the ground.

Solar Mystery Starts To Unravel As NASA Detects ‘Tadpole’ Jets Coming From Sun’s Surface

One of the biggest mysteries of the Sun is why its upper atmosphere—also known as the corona—is over 200 times hotter than its surface. For some unknown reason, this region that extends millions of miles into space is superheated—while the surface temperature hovers around 5,500 degree Celsius, the corona can reach two million degrees Celsius.

In a study published in Nature Astronomy, scientists with NASA are now edging closer to understanding this weird phenomenon.

While analyzing data taken by one of the space agency’s solar observation satellites, researchers discovered jets emerging from sunspots and shooting up to 3,000 miles into the inner corona. The jets had bulky heads and slim tails, so they looked like tadpoles swimming through the layers of the Sun.

Sunspots are regions that temporarily appear on the surface of the Sun. They are much cooler than the surrounding areas and are highly magnetized.

Previously, there were two main hypotheses about what was heating the Sun’s corona. The first relates to nanoflares, where explosions caused by the reconnection of magnetic lines release energy into the atmosphere, heating it in the process. The second involves electromagnetic waves, with charged particles being pushed into the Sun’s atmosphere. The tadpole discovery adds a third possibility to the mix.

Scientists found the tadpoles were made up entirely of plasma—the fourth state of matter, consisting of electrically conducting material made up of charged particles. The tadpoles (also known as ‘pseudo shocks’) may help heat up the Sun’s corona at specific times in its 11 year cycle—specifically during the solar maximum, when there is increased activity on the Sun’s surface.

The pseudo-shocks are thought to occur when magnetic field lines become tangled and produce explosions. This often happens around sunspots, but may well take place in other magnetized regions of space.

Computer simulations showed that the tadpoles could carry enough energy to heat the inner corona.

“We were looking for waves and plasma ejecta, but instead, we noticed these dynamical pseudo-shocks, like disconnected plasma jets, that are not like real shocks but highly energetic to fulfill Sun’s radiative losses,” lead author Abhishek Srivastava, from Indian Institute of Technology, said in a statement.

The Sun is currently coming to the end of its latest cycle—known as sunspot cycle 24—and will enter the next one at some point this year. As the new cycle begins, sunspot activity will begin to increase before reaching a peak, known as the solar maximum—currently expected to be around 2024.

Previously, scientists suggested that sunspot cycle 25 could be weaker than the current cycle, potentially meaning a period of global cooling could ensue. However, this has largely been ruled out, with a team of scientists in India recently predicting that the next solar cycle could be even stronger than the current one.

In their paper published in Nature Astronomy, the authors said: “We conclude that near-Earth and inter-planetary space environmental conditions and solar radiative forcing of climate over sunspot cycle 25 (i.e., the next decade) will likely be similar or marginally more extreme relative to what has been observed during the past decade over the current solar cycle.”