Insomnia Can Worsen Chronic Pain Conditions

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Insomnia Can Worsen Chronic Pain Conditions

People who have problems sleeping may also be more sensitive to pain, thus potentially worsening the effects of chronic pain conditions, new research from Norway shows.

In the study, researchers measured pain sensitivity in more than 10,000 adults who were participants in the Tromsø Study, anongoing public health study in Norway that began in 1974.

The results of the study showed that people who had insomnia were more sensitive to pain than people who didn’t have sleep problems. In particular, people who were experiencing chronic pain and who also had insomnia showed a greater increased sensitivity to pain. Pain sensitivity was also linked to the amount of time it took to get to sleep.

The findings show that “the need to improve sleep among chronic pain patients, and vice versa, is evident,” the study authors, led by Børge Sivertsen of the Norwegian Institute of Public Health in Bergen, Norway, wrote in their article.

In the study, the researchers first asked questions of the participants about their experience with insomnia, how long it took them to fall asleep and other sleep issues. For example, participants rated their experiences with insomnia during the previous year on a four-point scale, ranging from “never” to “more than once a week.” Out of all of the participants, 10.5 percent had what the researchers considered an insomnia disorder. [7 Strange Facts About Insomnia]

The participants then completed the cold-pressor test — a standard method used to mimic chronic pain in which people are asked to place their hands in cold water for a set period of time. People who remove their hands early show a decreased tolerance to pain. In this study, the participants were asked to keep their hands in water at 3 degrees Celsius (37 degrees Fahrenheit) for 106 seconds.

The results showed that 42 percent of patients who had insomnia took their hands out of the water before the 106 seconds were up, whereas only 31 percent of all of the participants did so. This increased sensitivity to pain was greater in those with more severe or more frequent insomnia. For example, people who had insomnia once a week were 52 percent more likely to take their hands out of the water early, compared to those without insomnia. Moreover, patients who had insomnia monthly were 24 percent more likely to take their hands out of the water early.

The total amount of time that people spent sleeping showed no effect on their pain tolerance, according to the study.

The link between sleep problems and chronic pain appeared especially pronounced, according to the study. The patients with both severe insomnia and chronic pain were more than twice as likely to take their hands out of the water earlyas participants who had neither condition. This effect was “synergistic,” meaning the two conditions combined had a greater effect than one would expect from just summing their individual effects, the study authors reported.

That synergy between chronic pain and sleep disorders suggests health care providers should consider jointly treating the two conditions in some patients, the authors stated. Both cognitive-behavioral therapy and medications are used to treat the two conditions separately, the authors noted, so further studies should look at using these methods to treat the conditions together.

Future research should look into not only clinical implications, but also the role of neurotransmitters in the co-occurrence of sleep disorders and pain, the authors said.

The study was published April 30 in the journal Pain.

Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Deadly, Lesser-Known Head and Neck Cancers Can’t be Ignored (Op-Ed)

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Deadly, Lesser-Known Head and Neck Cancers Can’t be Ignored (Op-Ed)

Dr. Kavita Pattani and Dr. Rafael Torro-Serra, surgical oncologists at UF Health Cancer Center-Orlando Health, contributed this article to Live Science’s Expert Voices: Op-Ed & Insights.

The public doesn’t hear about head and neck cancers as often as other cancers, possibly because they comprise about three percent of all forms of the disease.

But, the statistics are still shocking. According to an estimate from the National Cancer Institute, in 2012 alone, more than 52,000 men and women were diagnosed with head and neck cancers in the United States.

Realizing the risks

The reality is, the risk for head and neck cancer is present in more Americans than you might think, particularly those of us who smoke and drink alcohol, the two biggest risk factors for head and neck cancers of the mouth, oropharynx, hypopharynx and larynx.

In fact, at least 75 percent of head and neck cancers are caused by tobacco and alcohol use, according to the National Cancer Institute. However, environmental exposures may also play a role. For instance, individuals working in some jobs in the construction, textile, ceramic, wood and metal industries could have an increased risk of paranasal sinus and nasal cavity cancer. Exposure to smoking and Epstein Barr Virus (EBV) is a risk factor for nasopharyngeal cancer, while certain other industrial exposures, like asbestos and synthetic fibers, have been linked to larynx cancer.  [Smoking Causes 14 Million Medical Conditions in US Yearly, Study Finds  ]

Human papillomavirus virus (HPV) is also a big risk factor for some kinds of head and neck cancers, specifically ones that involve the tonsils or base of the tongue. In fact, a large amount of oropharyngeal cancers, even reaching back 40 years, have actually been from HPV-positive tumors. Today in the United States, cancers caused by HPV infection are rising while cancers caused by smoking are falling.

Additionally, sun exposure to the head and neck is a risk factor for skin cancers, and genetics can also play a role. Extended periods of sun exposure, history of prior sunburns and cumulative lifetime exposure to the sun can result in various forms of skin cancers. This is especially true for patients with fair skin, and those who may not use sun precautions. Patients with a family history of skin cancers such as melanoma are at increased risk of being predisposed to developing skin cancers, as well. And, a prior history of radiation exposure or metastatic disease from skin cancers can result in cancers of the salivary glands.

A cancer with subtle warning signs

By definition, head and neck cancer arises in the head or neck region, impacting such sites as the nasal cavity, sinuses, oral cavity, salivary glands, throat and larynx or voice box.

When patients get screened for cancer, it’s usually because that individual felt pain in a certain area of the body. Unfortunately, there is little warning that someone may have a head or neck cancer, because often pain is not involved, which may lead to delay in care. As surgical oncologists at Orlando Health, we’ve seen patients who think they simply have a sinus infection or allergic rhinitis that can be treated with antibiotics and medical management. Many times, however, they actually have sinus cancer.

While something like a sinus infection is not always cancerous, there a few telltale signs that it may be more than just an infection, like pain or numbness in the teeth, decreased sense of smell, difficulty opening the mouth, a lump or sore inside the nose that does not heal, or pain and swelling in the face. When these warning signs persist or worsen over several weeks, it’s time to schedule a detailed physical exam with a doctor.

Many of these symptoms can be caused by other noncancerous health conditions, but that’s why it’s so important to receive regular health and dental exams, especially if you routinely smoke or drink alcohol. It’s much easier to successfully treat sinus cancer when detected early.

According to a Harris Interactive survey on behalf of the Head and Neck Cancer Alliance, 71 percent of Americans say they have not been examined by a medical professional for oral, head or neck cancer. Given the rise in oropharynx cancers related to human papillomavirus (HPV), routine examinations for early detection of this disease are more important than ever.

If any abnormality is suspected, such as difficulty swallowing, persistent pain, a mass in the neck, changed or muffled voice and non-healing ulcers or sores, it is necessary to make an appointment with a dentist, oral surgeon, primary care physician, and when appropriate, an Ear-Nose-Throat (ENT)/head and neck specialist.We recommend routine checkups at least annually, but in addition to this, further evaluation is recommended with any worrisome or persistent findings.

Symptoms of head and neck cancers

Understanding some of the different kinds of head and neck cancers and their symptoms is the first step in prevention. Here are the main types everyone should be aware of:

HPV (Human Papillomavirus) Induced Cancer HPV is a type of virus that more commonly causes abnormal tissue growth, like warts, and other changes to cells. Certain strains of HPV are associated with oropharynx cancers in the head and neck. This type of infection can also lay dormant for many years and even decades prior to manifesting as a malignancy. A large majority of sexually active people will have some lifetime exposure to HPV. Most tend to clear the virus from the system and only a small percentage of the population exposed will develop cancer. At this time a routine screening is not performed for the HPV virus for head and neck cancers. The HPV is tested for its prognosticator value in those patients who develop oropharyngeal cancer.

Sinus and Nasal Cavity Cancer The paranasal sinuses are small, narrow spaces in the bones of the head around the nose. The most common type of paranasal sinus and nasal cavity cancer is squamous cell carcinoma. This type of cancer forms in the squamous cells (thin, flat cells) lining the inside of the paranasal sinuses and the nasal cavity. Some risk factors can include environmental exposures such as exposure to wood or nickel dust or formaldehyde. Some of the most likely symptoms of this type of cancer are blocked sinuses that do not clear, or frequent sinuses that do not respond to treatment with antibiotics, bleeding through the nose, headaches, and pain in the upper teeth. Many of these symptoms are not always cancerous, but it’s still key to get regular examinations, especially for people who routinely smoke or drink alcohol. These individuals should actually receive a physical exam at least once a year even if symptoms do not surface. Even if you don’t consistently drink alcohol or smoke, if you notice pain, swelling or blockage that continues for a few weeks or a month, schedule an appointment with a specialist.

Oropharyngeal Cancer The oropharynx is the middle part of the pharynx (throat) behind the mouth. It includes the back one-third of the tongue (base of tongue), the soft palate, side and back walls of the throat and the tonsils. Some common symptoms of this cancer include a sore throat that does not go away, trouble swallowing and opening the mouth fully, or difficulty moving the tongue. Other signs include a change in voice like persistent hoarseness and/or continuous ear pain. Many times, the presenting symptoms will be a lump or swelling in the neck.

Salivary Gland Cancer This type of cancer may be found during a regular dental check-up or physical exam. The major salivary glands are in front of the ear (parotid), at the bottom of the mouth (sublingual) and near the jawbone (submandibular). Minor salivary glands line the entire aerodigestive tract. A persistent lump (usually painless) occurs in the area in front of or just below the ear, cheek, jaw, lip, or inside the mouth. Sometimes there is numbness or pain in the face that does not go away or the facial nerve can lose function.

Avoiding cancer risks

Alcohol and tobacco use are two of the biggest risk factors for head and neck cancers. In fact, a huge majority of the patients we see use, or formerly used, these substances. Oral, head and neck cancers tend to form in the areas where tobacco or alcohol has had the most contact. For example, where a cigarette sits on the lip, where the chewing tobacco is placed in the mouth, and other areas of inhalational contact.

The best way to prevent oral, head and neck cancer is to avoid these substances altogether, or to work with your doctor on figuring out how to quit. [Top 10 Cancer-Fighting Foods  ]

A red or white patch in the mouth, a non-healing ulcer or a sore throat can also be the first signs of cancers of the mouth and throat. Hoarseness or a change in the voice can be the first sign of cancer of the voice box.

The bottom line is, when pain, swelling, soreness and other abnormalities persist over a reasonable period of time, which is usually no more than a few weeks to a month, it’s time to see a doctor. Some of our patients have allowed pain to persist for several months at a time — and that’s not normal. Earlier detection could mean detecting the cancer at an earlier stage. This, in turn, would pose a better prognosis, in general.

While taking courses of antibiotics will help curb pain and swelling, and in many cases it is the appropriate course of first action, if a physician is indeed dealing with cancer, antibiotics won’t actually treat the cancer. Further antibiotic courses may just be delaying the treatment process. Ignoring the pain, nodule or lump is the largest factor that leads to delay of care; listening to your body is key in prevention of head and neck cancers.

We can’t stress enough the importance of early detection. If you start to notice any of these signs, don’t wait. See a specialist right away.

To find screening locations in your area, visit the Head and Neck Cancer Alliance website.

Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google+. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Live Science.


Even a Little Walking Can Improve Your Health, Study Suggests

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Even a Little Walking Can Improve Your Health, Study Suggests

Want to reduce your risk of dying at a young age? Try walking casually for as little as 2 minutes per hour.

While it is well known that intense exercise can help you get fitter, a new study has found that even a little exercise can still go a long way. Study participants who traded time on the sofa for a total of 30 minutes of walking during the day reduced their risk of dying over a three-year period by 33 percent.

For the participants with chronic kidney disease, the risk of dying was reduced by more than 40 percent, according to the findings, published today (April 30) in the Clinical Journal of the American Society of Nephrology.

The Physical Activity Guidelines for Americans, a complement to the government’s diet guidelines, recommend that people do at least 75 minutes of high-intensity aerobic physical activity (such as running, swimming or biking), or 150 minutes of moderate-intensity activity (such as brisk walking) every week to reduce the risk of obesity, diabetes and other chronic diseases.

But the researchers on the new study wanted to know what the minimum threshold was — the lowest amount of physical activity that could still provide health benefits, said Dr. Srinivasan Beddhu, a kidney specialist at the University of Utah School of Medicine in Salt Lake City and lead author of the new study. [How Many Calories Am I Burning? (Infographic)]

“We know prolonged sitting is associated with poor [health] outcomes,” Beddhu told Live Science. “This study specifically looked at what intensity of activity should be used to replace sedentary activity. The term ‘sedentary activity’ might sound like an oxymoron, but being sedentary is an active choice to indulge in activities that barely raise the energy expenditure above basal metabolic rate.”

That threshold of intensity, Beddhu said, appears to be low. The study found that “light-intensity activities,” such as casual walking, are beneficial. In contrast, activities that are “low intensity,” such as standing or writing at a desk, aren’t enough to provide any meaningful health benefits, the study found.

For this study, Beddhu and his colleagues at the University of Utah and the University of Colorado used information from the National Health and Nutrition Examination Survey, which includes data collected from an accelerometer, a device that measures motion. This enabled the researchers to study the activities of more than 3,600 adults representing the general U.S. population, including 383 adults with chronic kidney disease.

Over the course of three years, 137 of these participants died as a result of various causes. In general, those who exercised more were less likely to die during the study period.

Positive effects of exercise could be seen down to the level of 30 minutes per day of any kind of light activity. Beddhu said that, from the data obtained in the study, he could not discern the precise nature or duration of this light activity, but he surmised that it could be attained merely by getting up to move around a few minutes every hour. The finding could be particularly beneficial for people with kidney disease, who tend to be sedentary and inactive throughout most of the day, Beddhu added.

The latest analysis supports the results of previous studies on the perils of inactivity. For instance, a finding published by researchers at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, in 2009 said that longer lengths of sitting were directly proportional to an increased risk of death from cardiovascular disease and most causes of death other than cancer.

Similarly, a study published in 2003 by Harvard researchers in the Journal of the American Medical Association (JAMA) found that each 2-hour increment of daily television watching raised people’s risk of obesity by about 25 percent and their risk of diabetes by 15 percent. Walking around the home, however, reduced these risks.

“We are not advocating for a total of 2 minutes per hour of light activity,” Beddhu said. “If a person is already doing 10 minutes per hour of light activity, going to 12 minutes per hour might further decrease their mortality risk.”

“It was fascinating to see these results because so much of the current focus is on moderate and vigorous activity,” Beddhu added. “A lot of little adds up to a lot.”

The assumption here, of course, is that those casual walks around the house don’t take you to the refrigerator for a snack.

Follow Christopher Wanjek @wanjek for daily tweets on health and science with a humorous edge. Wanjek is the author of “Food at Work” and “Bad Medicine.” His column, Bad Medicine, appears regularly on Live Science.

Ebola Survivors Should Use Condoms Indefinitely, CDC Says

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Ebola Survivors Should Use Condoms Indefinitely, CDC Says

The Ebola virus can remain in semen for longer than previously thought, and so men who survive the disease should always use a condom during sex until more information is known, the Centers for Disease Control and Prevention says.

This new recommendation follows the report of a woman in Liberia who may have contracted Ebola through sex with a man who had survived the disease.

The woman, who developed Ebola in mid-March, had not had contact with anyone with Ebola symptoms, and hadn’t traveled to other areas where people have Ebola. But about a week before her symptoms began, she had unprotected sex with a man who had survived Ebola.

Although the man had been declared Ebola-free six months earlier, in October 2014, a sample of his semen taken in late March of this year found genetic material from the Ebola virus. What’s more, when researchers looked at part of the genetic sequence of the Ebola virus in the man’s semen, this part matched the Ebola virus found in the woman, according to a new report of the case.

The researchers can’t say for certain that the woman caught Ebola through sex, but the information they have so far suggest that it’s possible, they said.

There has been just one other report of a person who possibly contracted Ebola through sex — the case occurred during a 1995 Ebola outbreak in the Democratic Republic of the Congo — but this report was also not conclusive. [What Are the Long-Term Effects of Ebola?]

Researchers knew that the Ebola virus could survive for months in semen, and have previously recommended that Ebola survivors either abstain from sex or use a condom for at least three months following their illness.

But the new report suggests that the man transmitted Ebola through sex about five months after he recovered, and nearly 200 days after he first showed Ebola symptoms.

“To prevent transmission of Ebola, contact with semen from male survivors should be avoided,” the researchers wrote in the report, published today (May 1) in the journal Morbidity and Mortality Weekly Report. “If male survivors have sex (oral, vaginal or anal), a condom should be used correctly and consistently every time until further information is known.”

Additional studies are now planned to determine how long the Ebola virus stays in the bodily fluids of survivors, to better understand the risk of Ebola spread through sex, the researchers said.

Still, if Ebola is transmitted through sex, it’s not known how often it happens. The Ebola survivor in the report also had sex with another woman during February and March, but she did not contract Ebola, the report said.

Follow Rachael Rettner @RachaelRettner. Follow Live Science@livescience, Facebook & Google+. Original article on Live Science.

Colorado Plague Outbreak Shows It’s Hard to Diagnose the Disease

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Colorado Plague Outbreak Shows It’s Hard to Diagnose the Disease

Doctors and veterinarians in the southwestern United States should keep an eye out for cases of plague, according to a new report from the Centers for Disease Control and Prevention.

During the summer of 2014, four people in Colorado became ill with pneumonic plague, in the United States’ largest outbreak of the illness since 1924. Pneumonic plague is a very rare disease caused by the same type of bacteria as the bubonic plague, which is perhaps best known for causing the Black Death in Europe during the Middle Ages. In people with pneumonic plague, the bacteria infect the respiratory system.

In the cases in Colorado, three of the people were initially diagnosed incorrectly, and the fourth, without knowing why she was sick, had self-medicated with antibiotics, the report found.

Hallmark of Plague

Credit: CDC
Bubonic plague, the most common form, is associated with painful, swollen lymph nodes, called buboes as shown above. After an incubation period of two to six days, symptoms appear, including severe malaise, headache, shaking chills and fever. Plague can also infect the blood or lungs. The latter form, pneumonic plague, can be transmitted person to person.

All four people have since recovered, but a veterinarian euthanized the 2-year-old American pit bull terrier that got the deadly bacterial infection in June and had passed it on to its owner and at least two of the other infected people. [Pictures of a Killer: Plague Gallery]

The fourth person may have caught pneumonic plague from the dog’s owner, which would make it “the first instance of possible human-to-human transmission” in the United States in 90 years, according to the CDC report, released today (April 30).

In the Blood

Credit: CDC
Yersinia pestis, the bacterium that causes plague, appears in this microscope image of the bacteria in the blood of the patient. Its cells are the tinyand safety-pin shaped. It kills between 50 and 90 percent of its untreated victims, and about 15 percent of those who are diagnosed and treated, according to the CDC.

The outbreak started with a 28-year-old man, who developed a fever and began coughing up blood on June 28. Doctors diagnosed him with pneumonia, and a test indicated that the bacterium Pseudomonas luteola was to blame. However, some of the doctors questioned the results because they knew the bacterium that causes plague, Yersinia pestis, can often be mistaken in tests for P. luteola.

A second test one week later confirmed that the man had pneumonic plague. Doctors gave him broad-spectrum antibiotics and hospitalized him for 23 days until he recovered.

It’s likely the man caught pneumonic plague from his dog, which had shown symptoms including a fever, jaw rigidity and drooling, and had problems walking and breathing. The man had the dog humanely euthanized. Once doctors realized that the man had pneumonic plague, they ordered a test of the dog’s remains, and found that it tested positive for plague bacteria, according to the report.

The veterinarian who treated the dog also got pneumonic plague, but was incorrectly diagnosed with bronchitis. Another person had contact with the dog’s body as well as its owner, and was initially diagnosed with pneumonia, but not plague. A veterinary clinic employee got sick too but self-medicated with antibiotics.

Plague by the numbers

Though rare, plague is a life-threatening disease. About eight people get plague in the United States every year, primarily in the semirural regions of New Mexico, Arizona, Colorado and California, according to the report. Typically, people get sick if infected fleas on rodents bite them, or if they have direct contact with the wounds or bodily fluids of infected animals, the researchers said.

Blood Suckers

Credit: CDC
Some have questioned whether plague caused the 14th century Black Death because the modern version of the disease does not spread as rapidly or kill as many as the Black Death did. Research in recent years has shown that fleas can transmit the bacterium much sooner after picking it up than thought. Previously, it was believed that transmission only happened after the bacterium blocked the flea’s stomach, starving it and causing it to regurgitate. This process could take several weeks, but now it appears some can transmit the disease in as little as four days.

Bubonic plague is the most common type of the disease, accounting for about 85 percent of reported cases. It’s known for causing fever and painful “buboes,” or swollen lymph nodes. Pneumonic plague can develop if someone with bubonic plague goes untreated, or if someone inhales droplets from an infected person’s cough or sneeze.

Pneumonic plague kills about 93 percent of people who catch it if they don’t receive medical treatment, the researchers said. But it’s also very uncommon: The U.S. had 74 reported cases of pneumonic plague between 1900 and 2012, the researchers said.

Doctors and veterinarians can learn several lessons from the Colorado outbreak, the researchers said.

The Bug

Credit: CDC/ Courtesy of Larry Stauffer, Oregon State Public Health Laboratory
A petri dish culture of the bacterium responsible for plague, Yersinia pestis. Genetic research has shown that this microbe evolved in or around Chinamore than 2,600 years ago and followed humans around the globe.

Early recognition of plague, especially the pneumonic form, is critical to effective clinical management and a timely public health response,” the researchers said in the study. “Veterinarians should consider plague in the differential diagnosis of ill domestic animals, including dogs, in areas where plague is endemic.”

Follow Laura Geggel on Twitter @LauraGeggel. Follow Live Science@livescience, Facebook & Google+. Original article on Live Science.

Millions of Dollars in Ivory Sold on Craigslist

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Millions of Dollars in Ivory Sold on Craigslist

From kitschy trinkets to carved tusks, thousands of objects — possibly worth more than $15 million a year — are being sold on Craigslist in the United States, according to a report.

From March 16 to 20, researchers with the International Fund for Animal Welfare (IFAW) and the Wildlife Conservation Society (WCS) combed through Craigslist postings in 28 geographic areas across the country.

Just in that five-day period, the authors of the new report flagged 456ivory products, 84 suspected ivory products and 75 related wildlife products (such as elephant skin) for sale, for a combined list price of at least $1.4 million. [In Photos: US Destroys Its Elephant Ivory]

If those numbers are representative of the average pace of the trade, that means 6,600 ivory items are being sold on Craigslist for $15.3 million each year, the authors said.

San Francisco and Los Angeles had the highest numbers of ivoryproducts for sale of any geographic area, the report revealed.

The United States abides by an international CITES treaty that partially banned ivory imports beginning more than 20 years ago. But domestic ivory markets continue to thrive and provide a convenient cover for smuggled ivory products. However, last year, the Obama administration proposed a near-complete ban on the commercial ivory trade in the United States, with exceptions for antiquities.

Many buyers may not realize that ivory objects they can pick up on the Internet could have been sourced from the tusks of one of the estimated 96 elephants illegally killed in Africa each day.

Beyond small pieces of jewelry and trinkets, the researchers classified many of the objects they saw for sale online as kitsch, including a “Japanese ivory erotica figurine” listed for $600 in San Diego and a footstool made from an elephant leg and covered in zebra or antelope hide offered for $700 in Chicago.

At the authors’ urging, Craigslist explicitly included ivory products on itsindex of banned items.

“The situation on Craigslist shows just how rampant wildlife trade is on the Internet, especially when host sites don’t do enough to stop it,” Peter LaFontaine, campaigns officer for IFAW, said in a statement. “eBay, Etsy and many other online marketplaces have willingly cooperated with law enforcement to reduce wildlife trafficking on their platforms. Craigslist’s decision to explicitly list ivory among the site’s prohibited items is a step in the right direction, but they must do more to actively enforce this policy and eliminate ivory sales from their site.”

Follow Megan Gannon on TwitterFollow us @livescienceFacebookGoogle+. Original article on Live Science.

How Do Strange, Scorching-Hot ‘Vulcan Planets’ Form?

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How Do Strange, Scorching-Hot ‘Vulcan Planets’ Form?

The mystery of how blisteringly hot “Vulcan planets” form may now be one step closer to being solved, researchers say.

In the past two decades or so, researchers have confirmed the existence of more than 1,800 exoplanets orbiting distant stars. These discoveries have revealed very different kinds of planets from those seen in the solar system, such as super-Earths, which are rocky worlds up to 10 times the mass of Earth.

Unexpectedly, astronomers recently found a strange new class of alien planets — worlds in the Earth- to super-Earth size range whose orbits, which are tightly packed together very near their host stars, range from just 1 to 100 days long. Most of these planets are both far larger and much closer to their stars than Mercury, which is only about two-fifths the diameter of Earth and has an orbit 88 days long. [The Strangest Alien Planets]

“Almost 99 percent of the Vulcans are on orbits that are smaller than Mercury’s orbit,” said study co-author Jonathan Tan, an astrophysicist at the University of Florida in Gainesville. “Some are 100 times closer to their star than the Earth is to the sun.”

Scientists have nicknamed these large, hot, rocky worlds “Vulcan planets.” The name does not come from the home world of Spock’s race in “Star Trek,” but from the Roman god of fire, and it was also the name given to a planet that some astronomers had thought might exist inside Mercury’s orbit in our solar system. The temperatures of Vulcans can be as high as about 1,340 degrees Fahrenheit (725 degrees Celsius), “similar to that of molten lava,” Tan said. “Oceans of lava are a distinct possibility.”

These compact systems of Vulcan planets “appear to be very common,” Tan told “Perhaps most planets in the galaxy are found in such systems.”

However, explaining how Vulcan worlds could have formed remains a challenge for scientists. Some theorists propose Vulcan planets may have originated farther from their host stars, and each other, than they exist today. They would have then spiraled in to their present orbits, explaining what astronomers see now. However, some details of the spacing between these tightly packed exoplanets do not fit the pattern one would expect if this migration scenario were true.

Another possibility is that Vulcan planets gradually formed where they are now from a disk of so-called planetesimals — rocks the size of asteroidsand moons. However, to get Vulcan planets to form this way so near their stars, one would need disks of planetesimals at least 20 times more massive than the disk that gave rise to Earth and the other planets in the solar system — an unlikely scenario, researchers say.

Recently, Tan and his colleague Sourav Chatterjee proposed a theory known as “inside-out planet formation” that may solve the mystery of how Vulcans take shape. It suggests that these worlds originated in the scorching-close orbits they occupy now from a stream of pebbles and small rocks that spiraled inward from more distant parts of their system. These stones accumulate in a ring around their star, and are kept from getting any closer by pressure forces in the inner disk around the star.

“We hypothesize that a planet will eventually form from this ring and will keep growing,” Tan said.

Eventually, this planet grows massive enough to scoop up most of the matter near it, creating a mostly empty gap in the disk of gas and dust around the star. Pebbles and small rocks that continue to spiral inward from more distant parts of the system then form into a ring slightly farther away from the star, and this process of planetary formation begins anew.

“Planets form sequentially, one after another, from inner orbits to outer orbits, hence ‘inside-out,'” Tan said.

In a new study of 629 Vulcan planets, the researchers now find that the greater the distance of these exoplanets from their parent star, the larger their mass. This matches a prediction of inside-out planetary formation.

“I am very excited to see that the observations appear to match the prediction,” Tan said. “This may indicate that we are on the right track in understanding how they formed.”

There are many aspects of this new theory that still need to be worked out in detail, Tan said. “One big question is why don’t all disks form planets in this way — for example, why is our solar system different?”

Chatterjee and Tan detailed their findings online Dec. 29 in the Astrophysical Journal Letters.

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