‘Ultracool’ dwarf star hosts three potentially habitable Earth-sized planets just 40 light-years away

By Adam Burgasser, University of California, San Diego.

The search for Earth-like planets – and life – beyond the solar system has long been the stuff of science fiction and fantasy. But today’s ground and space telescopes, high-precision instruments and advanced analysis techniques have made this search an active area of real scientific research. Hundreds of terrestrial worlds have been found over the past several years, including a handful at the right distance from their host star to have conditions amenable to liquid water on their rocky surfaces. Astronomers focus on planets in these “habitable zones” in the search for life beyond Earth.

Now for the first time, our international team has found Earth-sized planets around a type of star so extreme it’s referred to as an “ultracool dwarf.” This is the first time planets have been found around the lowest-mass stars, and indicates that they may be the ideal hunting grounds for habitable worlds beyond the solar system.

Size comparison of the Sun, an ultracool dwarf star and the planet Jupiter. Chaos syndrome, CC BY-SA

Shifting the focus in the search

Astronomers have recently started focusing their search for Earth-like planets away from bright, Sun-like stars to dimmer, cooler, low-mass stars called M dwarfs. These stars, while far more numerous in the Milky Way, are too faint to be seen with the naked eye.

Yet their relatively small diameters – less than one-half the width of the Sun – make it easier to detect Earth-sized planets orbiting them using a common technique called the transit method. A transit occurs when a planet passes between us and its host star, resulting in a very slight apparent dimming of the star as the planet blocks a portion of its light.

The alignment of the planet and star must be just right for a transit to be seen, so the probability of this happening is small, and usually only happens if the planet orbits very close to its star. Fortunately, the habitable zone around a cool M dwarf is also closer in than it is around a hotter Sun-like star, so transiting Earth-like planets in these systems have a greater chance of having the conditions necessary for liquid water on their surfaces.

Unfortunately, the feeble amount of light emitted by M dwarfs restricts the search for planetary transits to those stars closest to the Sun, and requires larger telescopes.

TRAPPIST-1 and its planets

It is a technical and scientific feat, then, that our international team of astronomers has found the first Earth-like planets around one of the coolest and smallest M dwarfs near the Sun. These “ultracool dwarf” stars are a mere tenth of the diameter of the Sun and 2,000 times fainter.

TRAPPIST telescope, ESO La Silla Observatory in Chile. Credit: TRAPPIST

The planets were found by the transit method, using a facility called TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope), a 60-cm telescope at La Silla Observatory in Chile, optimized to search for small variations in the dim light emitted by ultracool dwarfs. The trick is to monitor them in near-infrared light, a form of radiation with wavelengths longer than the visible light our eyes can perceive (infrared radiation is often used for television remote controls). Over the past year, my colleagues on the TRAPPIST team have monitored several dozen ultracool dwarfs to search for the faint transit signals characteristic of an Earth-sized planet, a mere one percent dip in the already faint light they emit.

Imagined view from the surface of one of the newly discovered planets, with ultracool dwarf star TRAPPIST-1 in the background.
ESO/M. Kornmesser,  CC BY

In September 2015, they found their first signal from a star they’ve dubbed TRAPPIST-1, located just 40 light-years away from us. Over the next several months they found more. In total, the astronomers have inferred the presence of three Earth-sized planets, all on very close orbits around the star, with orbital periods (“years”) ranging from 1.5 days to 73 days.

To have such short orbital periods, the planets must be extremely close to their star, between 1/100th and 1/10th the distance between the Sun and the Earth. This is closer than Mercury is to the Sun, and such a small orbit would scorch a planet in our solar system. However, around TRAPPIST-1 these orbits are in and around the habitable zone.

The inner two planets receive two and four times more light energy from their star than the Earth receives from the Sun, and while highly reflective surfaces might make these worlds cool enough for liquid water, they are probably more like Venuses – hot planets in which the water has evaporated into the atmosphere – than Earths. But the third planet, TRAPPIST-1d, receives between 20 percent and 100 percent of the starlight that Earth does from our Sun (insolation), so it orbits at the right distance to have liquid water on its surface, and is potentially an Earth-like world.

An imagined view from close to one of the three planets orbiting TRAPPIST-1. These worlds have sizes and temperatures similar to those of Venus and Earth – but that’s not all it takes to support life. ESO/M. Kornmesser,  CC BY

Filling out the planetary picture

Being at the right distance to have surface liquid water does not guarantee that an Earth-sized planet is truly Earth-like.

First, the proximity of these planets to their host star means they are likely “tidally locked,” forced to rotate at the same rate as they orbit the star, so that one side of the planet is in perpetual day and one side in perpetual night. (Tidal locking is why we always see the same face of the moon from Earth.) While it has long been held that this configuration would prevent the existence of surface liquid water, recent work suggests that such worlds may still have regions of habitability.

The composition and circulation of an atmosphere, if it exists, also plays a major role in habitability, either by reflecting stellar light or trapping heat through the greenhouse effect.

Finally, both tectonic activity and the existence of a protective planetary magnetic field can play roles. Tectonic forces are of particular interest for the innermost planet, TRAPPIST-1b, which may be squeezed and stretched by tidal forces from the host star, heating it from the inside and producing the kind of extensive volcanism we see on Jupiter’s moon Io.

Technicians continue to work on the Webb telescope’s instrumentation in advance of its launch in 2018. NASA/Chris Gunn, CC BY-NC-ND

The observations obtained by TRAPPIST cannot tell us anything about these planetary details, but the James Webb Space Telescope should tell us more when it is launched in 2018. This advanced replacement to the Hubble Space Telescope will have the sensitivity to detect the even smaller signal of absorption by the planets during their transit. Imprinted on this signal will be the chemical absorption patterns of the gases present in the atmosphere, which may include biogenic gases such as oxygen, methane and nitrous oxide, or volcanic gases such as sulfur dioxide.

The TRAPPIST team will soon be starting the next phase of its search for Earth-like worlds around ultracool dwarfs with the SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars) survey. This program will monitor 500 of the nearest ultracool dwarfs using four 1-meter robotic telescopes in Cerro Paranal, Chile. Construction of the site is already underway, and the team is looking forward to expanding our census of nearby habitable worlds around the smallest stars.

The ConversationAdam Burgasser, Professor of Physics, University of California, San Diego

This article was originally published on The Conversation. Read the original article.

Featured Image Credit:  ESO/M. Kornmesser, CC BY

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Science Rocks My Week: Our Most Popular Stories of the Week

It was another mixed bag of science this week, including the resurgence of an amazing article (including video) on a recent breakthrough from neuroscience research team that was able to grow neurons in the lab that are implantable.

Other surprising breakthroughs and first discoveries this week included:

  • The first fossilized heart was discovered
  • A scorpion turns out to have venom that may be beneficial to humans
  • A robotic diver that is getting close to being a real avatar
  • More very interesting news about what’s happening at Chernobyl 30 years later.

And… with no further ado, here are this week’s most popular stories on Science Rocks My World as voted by your clicks:

Neuroscience Breakthrough: Artificial, Implantable Neurons [Video]

neuron-modelScientists at McGill University have achieved a huge breakthrough in neuroscience – they have discovered how to make artificial neurons that are indistinguishable from normal human neurons and can be implanted to make new connections in the nervous system.

This is the first time scientists have managed to create new functional connections between neurons…

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The first fossilised heart ever found in a prehistoric animal

fossilzed-fishPalaeontologists and the famous Tin Man in The Wizard of Oz were once in search of the same thing: a heart. But in our case, it was the search for a fossilised heart. And now we’ve found one.

A new discovery, announced today in the journal eLife, shows the perfectly preserved 3D fossilised heart in a 113-119 million-year-old fish from Brazil called Rhacolepis.

This is the first definite fossilised heart found in any prehistoric animal…

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This Scorpion’s Sting May Be Good for You

Scorpio-maurus_1170-770x460Because of their venomous sting, scorpions are usually avoided at all costs. But a new discovery suggests the toxins found in some venom might actually have a unique benefit.

Published in the Proceedings of the National Academy of Sciences, the findings show that when a toxin produced by Scorpio maurus—a scorpion species found in North Africa and the Middle East—permeates the cell membrane it loses its potency and may actually become healthful.

“This is the first time a toxin has been shown to chemically reprogram once inside a cell, becoming something that may be beneficial…”

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How Astronomers Determined Whether This Object is an Exoplanet or a Brown Dwarf

WISEA1147-770x460Our galaxy may have billions of free-floating planets that exist in the darkness of space without any companion planets or even a host sun.

But scientists say it’s possible that some of those lonely worlds aren’t actually planets but rather light-weight stars called brown dwarfs.

Take, for example, the newfound object called WISEA 1147. It’s estimated to be between roughly five to 10 times the mass of Jupiter…

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Losing your virginity: how we discovered that genes could play a part

Couple_on_beachAs far as big life decisions go, choosing when to lose your virginity or the best time start a family are probably right up there for most people. It may seem that such decisions are mostly driven by social factors, such as whether you’ve met the right partner, social pressure or even your financial situation. But scientists are increasingly realising that such sexual milestones are also influenced by our genes…

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To fight Zika, let’s genetically modify mosquitoes – the old-fashioned way

An Aedes Aegypti mosquito is seen in a lab of the International Training and Medical Research Training Center (CIDEIM) in Cali, ColombiaThe near panic caused by the rapid spread of the Zika virus has brought new urgency to the question of how best to control mosquitoes that transmit human diseases. Aedes aegypti mosquitoes bite people across the globe, spreading three viral diseases: dengue,chikungunya and Zika. There are no proven effective vaccines or specific medications to treat patients after contracting these viruses.

Mosquito control is the only way, at present, to limit them. But that’s no easy task…

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This Robot ‘Mermaid’ can Grab Shipwreck Treasures [Video]

This Robot ‘Mermaid’ can Grab Shipwreck Treasures [Video]A robot called OceanOne with artificial intelligence and haptic feedback systems gives human pilots an unprecedented ability to explore the depths of the oceans.

Oussama Khatib held his breath as he swam through the wreck of La Lune, over 300 feet below the Mediterranean. The flagship of King Louis XIV sank here in 1664, 20 miles off the southern coast of France, and no human had touched the ruins—or the countless treasures and artifacts the ship once carried—in the centuries since…

READ MORE…


At Chernobyl and Fukushima, radioactivity has seriously harmed wildlife

Chernobyl-storksThe largest nuclear disaster in history occurred 30 years ago at the Chernobyl Nuclear Power Plant in what was then the Soviet Union. The meltdown, explosions and nuclear fire that burned for 10 days injected enormous quantities of radioactivity into the atmosphere and contaminated vast areas of Europe and Eurasia. The International Atomic Energy Agency estimates that Chernobyl released 400 times more radioactivity into the atmosphere than the bomb dropped on Hiroshima in 1945…

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How Monarch Butterflies Make it to Mexico Without a Map

Each fall, monarch butterflies across Canada and the United States turn their colorful wings toward the Rio Grande and migrate more than 2,000 miles to the relative warmth of central Mexico.

The journey, repeated instinctively by generations of monarchs, continues even as their numbers have plummeted due to loss of their sole larval food source—milkweed. Now, scientists think they have cracked the secret of the internal, genetically encoded compass monarchs use to determine the southwest direction they should fly each fall.

“Their compass integrates two pieces of information—the time of day and the sun’s position on the horizon—to find the southerly direction,” says Eli Shlizerman, assistant professor at the University of Washington, who has joint appointments in the applied mathematics and the electrical engineering departments.

While the nature of the monarch butterfly’s ability to integrate the time of day and the sun’s location in the sky are known from previous research, scientists have never understood how the monarch’s brain receives and processes this information. For the study, researchers wanted to model how the monarch’s compass is organized within its brain.

“We wanted to understand how the monarch is processing these different types of information to yield this constant behavior—flying southwest each fall,” Shlizerman says.

Monarchs use their large, complex eyes to monitor the sun’s position in the sky. But the sun’s position is not sufficient to determine direction. Each butterfly must also combine that information with the time of day to know where to go. Fortunately, like most animals including humans, monarchs possess an internal clock based on the rhythmic expression of key genes.

This clock maintains a daily pattern of physiology and behavior. In the monarch butterfly, the clock is centered in the antennae, and its information travels via neurons to the brain.

Biologists have previously studied the rhythmic patterns in monarch antennae that control the internal clock, as well as how their compound eyes decipher the sun’s position in the sky. For the study, published in the journal Cell Reports, researchers recorded signals from antennae nerves in monarchs as they transmitted clock information to the brain as well as light information from the eyes.

Migrating monarch butterflies. Credit:
Migrating monarch butterflies. Credit: babybluebbwCC BY-SA 2.0

SHORTEST ROUTE ISN’T THE BEST

“We created a model that incorporated this information—how the antennae and eyes send this information to the brain,” Shlizerman says. “Our goal was to model what type of control mechanism would be at work within the brain, and then asked whether our model could guarantee sustained navigation in the southwest direction.”

In their model, two neural mechanisms—one inhibitory and one excitatory—controlled signals from clock genes in the antennae. Their model had a similar system in place to discern the sun’s position based on signals from the eyes. The balance between these control mechanisms would help the monarch brain decipher which direction was southwest.

Based on their model, it also appears that when making course corrections monarchs don’t simply take the shortest turn to get back on route. Their model includes a unique feature—a separation point that would control whether the monarch turned right or left to head in the southwest direction.

“The location of this point in the monarch butterfly’s visual field changes throughout the day,” Shlizerman says. “And our model predicts that the monarch will not cross this point when it makes a course correction to head back southwest.”

Based on their simulations, if a monarch gets off course due to a gust of wind or object in its path, it will turn whichever direction won’t require it to cross the separation point.

Additional studies would need to confirm whether the researchers’ model is consistent with monarch butterfly brain anatomy, physiology, and behavior. So far, aspects of their model, such as the separation point, seem consistent with observed behaviors.

“In experiments with monarchs at different times of the day, you do see occasions where their turns in course corrections are unusually long, slow, or meandering,” Shlizerman says. “These could be cases where they can’t do a shorter turn because it would require crossing the separation point.”

Their model also suggests a simple explanation why monarch butterflies are able to reverse course in the spring and head northeast back to the United States and Canada. The four neural mechanisms that transmit information about the clock and the sun’s position would simply need to reverse direction.

“And when that happens, their compass points northeast instead of southwest,” says Shlizerman. “It’s a simple, robust system to explain how these butterflies—generation after generation—make this remarkable migration.”

Daniel Forger at the University of Michigan and James Phillips-Portillo at the University of Massachusetts are coauthors of the study, which was funded by the National Science Foundation and the Washington Research Fund and is published in the journal Cell Reports.

Source: Republished from Futurity.org as a derivative work under the Attribution 4.0 International license. Original article posted to Futurity by  .

Featured Photo Credit: Dwight Sipler via flickr, CC BY 2.0.

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Genetic detectives: how scientists use DNA to track disease outbreaks

By Emily Toth Martin, University of Michigan.

They’re the top questions on everyone’s mind when a new disease outbreak happens: where did the virus come from? When did this happen? How long has it been spreading in a particular country or group of people?

These questions have been the foundation of epidemiology, the study of the occurrence and spread of disease, since the days when outbreaks were tracked by hundreds and hundreds of questionnaires linking people with similar symptoms.

John Snow’s map tracking cholera cases to their source.
John Snow’s map tracking cholera cases to their source.
By John Snow, via Wikimedia Commons

John Snow, widely regarded as the one of the first epidemiologists (and somewhat of a folk hero in scientific circles), conducted one of the first known epidemiologic investigations during a London cholera outbreak in 1854. He went door to door, mapping cases of illness, and ultimately identified a water pump at the center of the outbreak.

These same fundamentals of so-called “shoe-leather epidemiology” are used every day by health departments, government agencies and research teams around the world to identify and track outbreaks. Thanks to improvements in the speed and cost of DNA analysis, these old methods are increasingly being paired with genomic technology.

Today, genetic sequencing allows us to determine how an infection travels – even tracing it across continents – with incredible precision.

The molecular clock – a stopwatch for infection

Viruses and bacteria contain DNA and RNA, which means they can evolve. As viruses and bacteria make copies of themselves, their molecular material changes. This is because the enzyme that copies DNA and RNA makes random errors as the virus or bacteria replicates.

This evolution is akin to the development of mammals over evolutionary history, but with an important difference. The lifespan of a bacterium or virus is short, and they replicate quickly in astonishing quantities. This means we can observe evolutionary change in as short a span as just a few hours or days.

This constant change is called a molecular clock. Once an infection is transmitted to a new victim, starting a new branch on that infection’s genetic tree, the clock starts anew and continues to tick until the victim’s body defeats the infection or until the infection kills the victim.

We can observe this change directly by sequencing infections in different people and comparing how similar or different they are. This is work that is done by my laboratory and many others around the world. We assume that infections with similar sequences come from the same location at the same time, giving clues into when an infection entered a particular area, or how an infection traveled from one group of people to another.

For viruses with a very high mutation rate, the detective work can get more complicated. A single person’s infection will evolve to the point where he or she has many different versions of the pathogen in the body, and only one copy, with one genetic version, may actually infect another person. Investigating these types of viruses requires the latest technology in whole-genome sequencing technology and bioinformatics, the computational analysis required to interpret large amounts of sequence data.

Tracing outbreaks both old and new

Genetic analysis has lead scientists to hypothesize that Zika probably entered Brazil during a 2014 international canoe competition, likely carried by a person from French Polynesia or another Pacific Island. Genetic analysis also pinpointed that cholera was introduced into Haiti by peacekeepers after the 2010 earthquake, linked through sequencing data. Tracing how an infection moves into and through a country or a group of people helps public health officials determine what interventions may work to prevent future spread.

Genomics have even busted myths about disease, such as the oft-repeated story of Patient Zero, the man who purportedly introduced HIV into the United States in the 1980s. Molecular clock calculations have shown this scenario to be incorrect. It turns out HIV had been circulating in the United States since the late 1960s, over a decade before the Centers for Disease Control and Prevention (CDC) identified the first AIDS cases.

One of my favorite examples of the power of genetic detective work is the studies of the measles virus before and after vaccination largely eliminated the disease in the United States. Before the measles vaccine was developed, the virus was common, spreading from person to person within the U.S. After the introduction of the vaccine in 1963, the virus largely disappeared, with the occasional resurgence in areas where vaccination rates are low.

The genetics of the virus tell us that U.S. measles cases after 1963 are mostly due to people with infections traveling to the U.S. from other countries, rather than spreading from person to person within the U.S.

A vial of measles, mumps and rubella vaccine and an information sheet is seen at Boston Children’s Hospital in Boston, Massachusetts, February 26, 2015.
Brian Snyder/Reuters

When sequencing technology was first available, it was a long and expensive process that could clarify outbreaks only in hindsight. Now, it is inexpensive and fast enough to use while an outbreak is ongoing. During the measles outbreak that began at Disneyland in California in December 2014, the CDC was able to quickly determine that it started with a strain similar to measles cases in the Philippines, where measles outbreaks are more common.

We can even use genomics on a case-by-case basis to tell whether one person infected another, because infections on either side of a transmission event will be more similar to each other than to unrelated samples.

This technology has already been useful in untangling the spread of hospital-associated infections, which occur within notoriously complex webs of connections and risk factors. Whole-genome sequencing allows researchers to trace these infections as they move from one patient to another. Hopefully future developments will allow us to identify and interrupt these chains of transmission in real time.

We still need old-fashioned shoe-leather epidemiology

Even with all of the advances in sequencing over the past decade, our ability to conduct genetic investigations is only as good as our public health infrastructure. The most advanced technologies are useless without ongoing disease surveillance.

A trained, funded and sustainable public health workforce must be in place to identify outbreaks early, collect samples and respond quickly to interrupt transmission. Molecular epidemiology works only to the extent that samples are collected for researchers to use to compare and contrast sequences.

When outbreaks are not identified early, or when the right samples aren’t collected, the investigation will be unable to find links between people in the outbreak and the source of the infection. We need both cutting-edge genetic technology and centuries-old epidemiologic methods to continue to work to stop the spread of infectious diseases.

The ConversationEmily Toth Martin, Assistant Professor of Epidemiology , University of Michigan

This article was originally published on The Conversation. Read the original article.

Featured Photo Credit: Maria Armas/Reuters

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