The Universe: Learning About The Future From The Distant Past

Our Universe came to life nearly 14 billion years ago in the Big Bang — a tremendously energetic fireball from which the cosmos has been expanding ever since. Today, space is filled with hundreds of billions of galaxies, including our solar system’s own galactic home, the Milky Way. But how exactly did the infant universe develop into its current state, and what does it tell us about our future?

universe

These are the fundamental questions “astrophysical archeologists” like Risa Wechsler want to answer. At the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) of Stanford and the Department of Energy’s SLAC National Accelerator Laboratory, her team combines experimental data with theory in computer simulations that dig deeply into cosmic history and trace back how matter particles clumped together to form larger and larger structures in the expanding universe.

“Most of our calculations are done at KIPAC, and computing is a crucial aspect of the collaboration between SLAC and Stanford,” says Wechsler, who is an associate professor of physics and of particle physics and astrophysics.

Wechsler’s simulated journeys through spacetime use a variety of experimental data, including observations by the Dark Energy Survey (DES), which recently discovered a new set of ultra-faint companion galaxies of our Milky Way that are rich in what is known as dark matter. The gravitational pull from this invisible form of matter affects regular matter, which plays a crucial role in the formation and growth of galaxies.

Dark energy is another key ingredient shaping the universe: It inflates the universe like a balloon at an ever-increasing rate, but researchers don’t know much about what causes the acceleration.

Two future projects will give Wechsler and other researchers new clues about the mysterious energy. The Dark Energy Spectroscopic Instrument (DESI), whose science collaboration she is leading, will begin in 2018 to turn two-dimensional images of surveys like DES into a three-dimensional map of the universe. The Large Synoptic Survey Telescope (LSST), whose ultrasensitive 3,200-megapixel digital eye is being assembled at SLAC, will start a few years later to explore space more deeply than any telescope before.

“Looking at faraway galaxies means looking into the past and allows us to measure how the growth and distribution of galaxies were affected by dark energy at different points in time,” Wechsler says. “Over the past 10 years, we’ve made a lot of progress in refining our cosmological model, which describes many of the properties of today’s universe very well. Yet, if future data caused this model to break down, it would completely change our view of the universe.”

The current model suggests that the universe is fated to expand forever, turning into a darker and darker cosmos faster and faster, with galaxies growing farther and farther apart. But is this acceleration a constant or changing property of spacetime? Or could it possibly be a breakdown of our theory of gravity on the largest scales? More data will help researchers find an answer to these fundamental questions.

An Ocean Lies A Few Kilometers Beneath Saturn’s Moon Enceladus’s Icy Surface

With eruptions of ice and water vapor, and an ocean covered by an ice shell, Saturn’s moon Enceladus is one of the most fascinating in the Solar System, especially as interpretations of data provided by the Cassini spacecraft have been contradictory until now. An international team including researchers from the Laboratoire de Planétologie Géodynamique de Nantes (CNRS/Université de Nantes/Université d’Angers), Charles University in Prague, and the Royal Observatory of Belgium[recently proposed a new model that reconciles different data sets and shows that the ice shell at Enceladus’s south pole may be only a few kilometers thick.

enceladus

This suggests that there is a strong heat source in the interior of Enceladus, an additional factor supporting the possible emergence of life in its ocean.

The study has just been published online on the website of Geophysical Research Letters.

Initial interpretations of data from Cassini flybys of Enceladus estimated that the thickness of its ice shell ranged from 30 to 40 km at the south pole to 60 km at the equator. These models were unable to settle the question of whether or not its ocean extended beneath the entire ice shell. However, the discovery in 2015 of an oscillation in Enceladus’s rotation known as a libration, which is linked to tidal effects, suggests that it has a global ocean and a much thinner ice shell than predicted, with a mean thickness of around 20 km. Nonetheless, this thickness appeared to be inconsistent with other gravity and topography data.

In order to reconcile the different constraints, the researchers propose a new model in which the top two hundred meters of the ice shell acts like an elastic shell. According to this study, Enceladus is made up successively of a rocky core with a radius of 185 km, and an internal ocean approximately 45 km deep, isolated from the surface by an ice shell with a mean thickness of around 20 km, except at the south pole where it is thought to be less than 5 km thick. In this model, the ocean beneath the ice makes up 40% of the total volume of the moon, while its salt content is estimated to be similar to that of Earth’s oceans.

All this implies a new energy budget for Enceladus. Since a thinner ice shell retains less heat, the tidal effects caused by Saturn on the large fractures in the ice at the south pole are no longer enough to explain the strong heat flow affecting this region. The model therefore reinforces the idea that there is strong heat production in Enceladus’s deep interior that may power the hydrothermal vents on the ocean floor. Since complex organic molecules, whose precise composition remains unknown, have been detected in Enceladus’s jets, these conditions appear to be favorable to the emergence of life. The relative thinness of the ice shell at the south pole could also allow a future space exploration mission to gather data, in particular using radar, which would be far more reliable and easy to obtain than with the 40 km thick ice shell initially calculated.

Newborn Giant Planet Grazes Its Star

For the past 20 years, exoplanets known as ‘hot Jupiters’ have puzzled astronomers. These giant planets orbit 100 times closer to their host stars than Jupiter does to the Sun, which increases their surface temperatures. But how and when in their history did they migrate so close to their star? Now, an international team of astronomers has announced the discovery of a very young hot Jupiter orbiting in the immediate vicinity of a star that is barely two million years old — the stellar equivalent of a week-old infant. This first-ever evidence that hot Jupiters can appear at such an early stage represents a major step forward in our understanding of how planetary systems form and evolve.

planet

The work, led by researchers at the Institut de Recherche en Astrophysique et Planétologie (IRAP, CNRS/Université Toulouse III — Paul Sabatier)[1], in collaboration, amongst others[2], with colleagues at the Institut de Planétologie et d’Astrophysique de Grenoble (CNRS/Université Grenoble Alpes)[3], is published on 20 June 2016 in the journal Nature.

It was while monitoring a star barely two million years old called V830 Tau, located in the Taurus stellar nursery some 430 light years away, that an international team of astronomers discovered the youngest known hot Jupiter. The team observed the star for a month and a half and detected a regular fluctuation in the star’s velocity, revealing the presence of a planet almost as massive as Jupiter, orbiting its host star at a distance only one twentieth of that between the Earth and the Sun. The discovery shows for the first time that hot Jupiters can appear at a very early stage in the formation of planetary systems, and therefore have a major impact on their architecture.

In the Solar System, small rocky planets such as the Earth orbit near the Sun, whereas gas giants like Jupiter and Saturn are found much further out. Astronomers were therefore astonished when the first exoplanets detected turned out to be giants orbiting close to their host star. Theoretical work indicates that such planets can only form in the icy outer regions of the protoplanetary disk in which both the central star and its surrounding planets are born. Some, however, migrate inwards and yet avoid falling into their host star, thus becoming hot Jupiters.

Theoretical models predict that migration occurs either early in the lives of giant planets while still embedded within the protoplanetary disk, or else much later, once multiple planets are formed and interact, flinging some of them into the immediate vicinity of their star. Among the known hot Jupiters, some feature tilted or even backward orbits, suggesting that they were hurled towards their star by neighboring bodies. The discovery of a very young hot Jupiter thus confirms that early migration within the disk also applies to giant planets.

Detecting planets in orbit around very young stars proves to be a significant observational challenge, since such stars are monsters in comparison with our own Sun. This is because their intense magnetic activity interferes with the light emitted by the star to a far greater extent than a potential giant planet, even in a close orbit. One of the team’s achievements was to separate the signal caused by the star’s activity from the signal produced by the planet.

For this discovery, the team used the twin spectropolarimeters[4] ESPaDOnS and Narval, designed and built at IRAP. ESPaDOnS is mounted on the Canada-France-Hawaii Telescope (CFHT) on the summit of Maunakea, a dormant volcano on the Island of Hawaii. Narval is mounted on the Bernard Lyot telescope (TBL — OMP) atop the Pic du Midi in the French Pyrenees. The combined use of these two telescopes together with Hawaii’s Gemini telescope was essential for the required continuous monitoring of V830 Tau. SPIRou and SPIP, the next-generation infrared spectropolarimeters built at IRAP for the CFHT and TBL, scheduled for first light in 2017 and 2019 respectively, will offer vastly superior performance and make it possible to study the formation of new worlds with unprecedented sensitivity.

Strong ‘Electric Wind’ Strips Planets of Oceans and Atmospheres

Venus has an ‘electric wind’ strong enough to remove the components of water from its upper atmosphere, which may have played a significant role in stripping the planet of its oceans.

Venus has an ‘electric wind’ strong enough to remove the components of water from its upper atmosphere, which may have played a significant role in stripping the planet of its oceans, according to a new study by NASA and UCL researchers.

“It’s amazing and shocking,” said Glyn Collinson, previously at UCL Mullard Space Science Laboratory and now a scientist at NASA’s Goddard Space Flight Center. “We never dreamt an electric wind could be so powerful that it can suck oxygen right out of an atmosphere into space. This is something that definitely has to be on the checklist when we go looking for habitable planets around other stars.”

The study, published today in the journal Geophysical Research Letters, discovered that Venus’ electric field is so strong that it can accelerate the heavy electrically charged component of water — oxygen — to speeds fast enough to escape the planet’s gravity.

When water molecules rise into the upper atmosphere, sunlight breaks the water into hydrogen ions which are fast and escape easily, and heavier oxygen ions which are carried away by the electric field.

Co-author, Professor Andrew Coates of the UCL MSSL, who leads the electron spectrometer team, said, “We’ve been studying the electrons flowing away from Titan and Mars as well as from Venus, and the ions they drag away to space to be lost forever. We found that over 100 metric tons per year escapes from Venus by this mechanism — significant over billions of years. The new result here is that the electric field powering this escape is surprisingly strong at Venus compared to the other objects. This will help us understand how this universal process works.”

Venus is the planet most like Earth in terms of its size and gravity, and evidence suggests it once had oceans worth of water which boiled away to steam long ago with surfaces temperatures of around 860 degrees Fahrenheit (460 Centigrade). Yet Venus’ thick atmosphere, about 100 times the pressure of Earth’s, has 10,000 to 100,000 times less water than Earth’s atmosphere, suggesting something removed all the steam.

Scientists thought it was the solar wind eroding the remainder of an ocean’s worth of oxygen and water slowly from Venus’ upper atmosphere, but the new findings suggest it was an aggressive electric wind instead.

Just as every planet has a gravity field, it is believed that every planet with an atmosphere is also surrounded by a weak electric field. While the force of gravity is trying to hold the atmosphere on the planet, the electric force can help to push the upper layers of the atmosphere off into space.

The team discovered Venus’ electric field using the NASA-SwRI-UCL electron spectrometer, which is part of a larger instrument called ASPERA-4 aboard the ESA Venus Express. When monitoring electrons flowing out of the upper atmosphere, they noticed the electrons were not escaping at their expected speeds because they were being tugged on by Venus’ potent electric field. By measuring the change in speed, the team found the strength of the field to be much stronger than expected, and at least five times more powerful than at Earth.

“We don’t really know why it is so much stronger at Venus than Earth,” said Collinson, “but, we think it might have something to do with Venus being closer to the sun, and the ultraviolet sunlight being twice as bright. It’s a really challenging thing to measure and to date all we have are upper limits on how strong it might be here.”

Another planet where the electric wind may play an important role is Mars. NASA’s MAVEN mission is currently orbiting Mars to determine what caused the Red Planet to lose much of its atmosphere and water.

Professor Coates added, “With ESA’s Mars Express, we have already caught this process in action at Mars, and MAVEN can now determine its relative importance. With NASA’s Cassini spacecraft we found that Titan loses 7 metric tonnes per day this way.”

Understanding the role played by planet’s electric winds will help astronomers improve estimates of the size and location of habitable zones around other stars. “Even a weak electric wind could still play a role in water and atmospheric loss at any planet,” said Alex Glocer of NASA Goddard, a co-author on the paper. “It could act like a conveyor belt, moving ions higher in the ionosphere where other effects from the solar wind could carry them away.”

NASA’s K2 Finds Newborn Exoplanet Around Young Star

Astronomers have discovered the youngest fully formed exoplanet ever detected. The discovery was made using NASA’s Kepler Space Telescope and its extended K2 mission, as well as the W. M. Keck Observatory on Mauna Kea, Hawaii. Exoplanets are planets that orbit stars beyond our Sun.

nasa

The newfound planet, K2-33b, is a bit larger than Neptune and whips tightly around its star every five days. It is only 5 to 10 million years old, making it one of a very few newborn planets found to date.

“Our Earth is roughly 4.5 billion years old,” said Trevor David of Caltech in Pasadena, lead author of a new study published online June 20, 2016, in the journal Nature. “By comparison, the planet K2-33b is very young. You might think of it as an infant.” David is a graduate student working with astronomer Lynne Hillenbrand, also of Caltech.

Planet formation is a complex and tumultuous process that remains shrouded in mystery. Astronomers have discovered and confirmed roughly 3,000 exoplanets so far; however, nearly all of them are hosted by middle-aged stars, with ages of a billion years or more. For astronomers, attempting to understand the life cycles of planetary systems using existing examples is like trying to learn how people grow from babies to children to teenagers, by only studying adults.

“The newborn planet will help us better understand how planets form, which is important for understanding the processes that led to the formation of Earth,” said co-author Erik Petigura of Caltech.

The first signals of the planet’s existence were measured by K2. The telescope’s camera detected a periodic dimming of the light emitted by the planet’s host star, a sign that an orbiting planet could be regularly passing in front of the star and blocking the light. Data from the Keck Observatory validated that the dimming was indeed caused by a planet, and also helped confirm its youthful age.

Infrared measurements from NASA’s Spitzer Space Telescope showed that the system’s star is surrounded by a thin disk of planetary debris, indicating that its planet-formation phase is wrapping up. Planets form out of thick disks of gas and dust, called protoplanetary disks, that surround young stars.

“Initially, this material may obscure any forming planets, but after a few million years, the dust starts to dissipate,” said co-author Anne Marie Cody, a NASA Postdoctoral Program fellow at NASA’s Ames Research Center in California’s Silicon Valley. “It is during this time window that we can begin to detect the signatures of youthful planets with K2.”

A surprising feature in the discovery of K2-33b is how close the newborn planet lies to its star. The planet is nearly 10 times closer to its star than Mercury is to our sun, making it hot. While numerous older exoplanets have been found orbiting very tightly to their stars, astronomers have long struggled to understand how more massive planets like this one wind up in such small orbits. Some theories propose that it takes hundreds of millions of years to bring a planet from a more distant orbit into a close one — and therefore cannot explain K2-33b, which is quite a bit younger.

The science team says there are two main theories that may explain how K2-33b wound up so close to its star. It could have migrated there in a process called disk migration that takes hundreds of thousands of years. Or, the planet could have formed “in situ” — right where it is. The discovery of K2-33b therefore gives theorists a new data point to ponder.

“After the first discoveries of massive exoplanets on close orbits about 20 years ago, it was immediately suggested that they could absolutely not have formed there, but in the past several years, some momentum has grown for in situ formation theories, so the idea is not as wild as it once seemed,” said David.

“The question we are answering is: Did those planets take a long time to get into those hot orbits, or could they have been there from a very early stage? We are saying, at least in this one case, that they can indeed be there at a very early stage,” he said.

Ames manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA’s Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder.

Small Asteroid Is Earth’s Constant Companion

A small asteroid has been discovered in an orbit around the Sun that keeps it as a constant companion of Earth, and it will remain so for centuries to come.

asteroid

As it orbits the Sun, this new asteroid, designated 2016 HO3, appears to circle around Earth as well. It is too distant to be considered a true satellite of our planet, but it is the best and most stable example to date of a near-Earth companion, or “quasi-satellite.”

“Since 2016 HO3 loops around our planet, but never ventures very far away as we both go around the sun, we refer to it as a quasi-satellite of Earth,” said Paul Chodas, manager of NASA’s Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena, California. “One other asteroid — 2003 YN107 — followed a similar orbital pattern for a while over 10 years ago, but it has since departed our vicinity. This new asteroid is much more locked onto us. Our calculations indicate 2016 HO3 has been a stable quasi-satellite of Earth for almost a century, and it will continue to follow this pattern as Earth’s companion for centuries to come.”

In its yearly trek around the Sun, asteroid 2016 HO3 spends about half of the time closer to the sun than Earth and passes ahead of our planet, and about half of the time farther away, causing it to fall behind. Its orbit is also tilted a little, causing it to bob up and then down once each year through Earth’s orbital plane. In effect, this small asteroid is caught in a game of leap frog with Earth that will last for hundreds of years.

The asteroid’s orbit also undergoes a slow, back-and-forth twist over multiple decades. “The asteroid’s loops around Earth drift a little ahead or behind from year to year, but when they drift too far forward or backward, Earth’s gravity is just strong enough to reverse the drift and hold onto the asteroid so that it never wanders farther away than about 100 times the distance of the moon,” said Chodas. “The same effect also prevents the asteroid from approaching much closer than about 38 times the distance of the moon. In effect, this small asteroid is caught in a little dance with Earth.”

Asteroid 2016 HO3 was first spotted on April 27, 2016, by the Pan-STARRS 1 asteroid survey telescope on Haleakala, Hawaii, operated by the University of Hawaii’s Institute for Astronomy and funded by NASA’s Planetary Defense Coordination Office. The size of this object has not yet been firmly established, but it is likely larger than 120 feet (40 meters) and smaller than 300 feet (100 meters).

 

Most Distant Oxygen Ever Observed

Astronomers from Japan, Sweden, the United Kingdom and ESO have used the Atacama Large Millimeter/submillimeter Array (ALMA to observe one of the most distant galaxies known. SXDF-NB1006-2 lies at a redshift of 7.2, meaning that we see it only 700 million years after the Big Bang.

oxygen

The team was hoping to find out about the heavy chemical elements [1] present in the galaxy, as they can tell us about the level of star formation, and hence provide clues about the period in the history of the Universe known as cosmic reionisation.

“Seeking heavy elements in the early Universe is an essential approach to explore the star formation activity in that period,” said Akio Inoue of Osaka Sangyo University, Japan, the lead author of the research paper, which is being published in the journal Science. “Studying heavy elements also gives us a hint to understand how the galaxies were formed and what caused the cosmic reionisation,” he added.

In the time before objects formed in the Universe, it was filled with electrically neutral gas. But when the first objects began to shine, a few hundred million years after the Big Bang, they emitted powerful radiation that started to break up those neutral atoms — to ionise the gas. During this phase — known as cosmic reionisation — the whole Universe changed dramatically. But there is much debate about exactly what kind of objects caused the reionisation. Studying the conditions in very distant galaxies can help to answer this question.

Before observing the distant galaxy, the researchers performed computer simulations to predict how easily they could expect to see evidence of ionised oxygen with ALMA. They also considered observations of similar galaxies that are much closer to Earth, and concluded that the oxygen emission should be detectable, even at vast distances [2].

They then carried out high-sensitivity observations with ALMA [3] and found light from ionised oxygen in SXDF-NB1006-2, making this the most distant unambiguous detection of oxygen ever obtained. It is firm evidence for the presence of oxygen in the early Universe, only 700 million years after the Big Bang.

Oxygen in SXDF-NB1006-2 was found to be ten times less abundant than it is in the Sun. “The small abundance is expected because the Universe was still young and had a short history of star formation at that time,” commented Naoki Yoshida at the University of Tokyo. “Our simulation actually predicted an abundance ten times smaller than the Sun. But we have another, unexpected, result: a very small amount of dust.”

The team was unable to detect any emission from carbon in the galaxy, suggesting that this young galaxy contains very little un-ionised hydrogen gas, and also found that it contains only a small amount of dust, which is made up of heavy elements. “Something unusual may be happening in this galaxy,” said Inoue. “I suspect that almost all the gas is highly ionised.”

The detection of ionised oxygen indicates that many very brilliant stars, several dozen times more massive than the Sun, have formed in the galaxy and are emitting the intense ultraviolet light needed to ionise the oxygen atoms.

The lack of dust in the galaxy allows the intense ultraviolet light to escape and ionise vast amounts of gas outside the galaxy. “SXDF-NB1006-2 would be a prototype of the light sources responsible for the cosmic reionisation,” said Inoue.

“This is an important step towards understanding what kind of objects caused cosmic reionisation,” explained Yoichi Tamura of the University of Tokyo. “Our next observations with ALMA have already started. Higher resolution observations will allow us to see the distribution and motion of ionised oxygen in the galaxy and provide vital information to help us understand the properties of the galaxy.”