Contracting white dwarf observed for the first timeNovember 14, 2017
Astrophysicists from MSU (Russia) and his colleagues from Italy and Russian Academy of Sciences have found the first observational evidence for a contracting white dwarf. Constant high spin-up rate of a star of this type, located in an enigmatic binary system, can be easily explained if the white dwarf is contracting, the researchers argue. The discovery is reported in the Monthly Notices of the Royal Astronomical Society.
"Thanks to this discovery, astrophysicists will be able to study and evaluate the evolution patterns of young white dwarfs -- and successfully look for similar systems in the galaxy, " -- noted the main author of the article, astrophysicist Sergei Popov (SAI MSU).
It is widely believed, based on theoretical considerations, that young white dwarfs -- the compact remnants of solar-like stars, -- should experience a phase of contraction in their early life. The radius of a typical white dwarf can decrease by several hundred kilometers during the first million years of its life. However, there was no observational evidence for this effect up to now. First, because most of the known white dwarf are much older. Second, because the scientists do not have a direct and precise way to measure the radii, and their variations, in these stars.
Studying an enigmatic X-ray source in a binary system of a rare type, the scientists might have found the first observational evidence for a contracting white dwarf. The binary system HD49798/RX J0648.0-4418 is at a distance of 2000 light years, in the Puppis constellation, and has been extensively studied with optical, UV, and X-ray telescopes. It contains a massive white dwarf, which spins with a period of only 13 s, the fastest known for a white dwarf, and emits X-rays due to the accretion of matter captured from the stellar wind of its companion star.
Sandro Mereghetti (a coauthor of the new paper) recently discovered that the rotational velocity of this white dwarf has been steadily increasing during the latest 20 years. Its spin period of 13 s is decreasing by 7 nanoseconds every year. This might seem a very small change, but it is actually a very large effect for a body weighting more than our Sun, but with a radius as small as about 5000 km (less than the Earth). Indeed, such a large spin-up rate could not be easily explained in standard ways (e.g. by the captured angular momentum of the accreting matter).
The solution to this puzzle has been now presented by the authors of this new study. They demonstrate that the high spin-up rate can be easily explained if the white dwarf is contracting, exactly as in the case of a spinning skater that brings in her arms to rotate faster. The evolutionary calculations presented in the paper show that the white dwarf has an age of only about 2 million years. The contraction rate of about one centimeter per year expected for this age is exactly of the correct amount to explain the measured spin-up rate, showing that this is the first example of contracting white dwarf ever identified.
"For decades it has been theoretically clear that that young white dwarfs are contracting. Yet, that very phase of contraction has never been observed "in real time". We should thank the uniqueness of the binary system under study: the white dwarf was literally illuminated (due to the accretion of matter from the neighboring star). But it was highlighted so neatly that the accreting matter did not affect its rotation -- an extremely rare phenomenon! In other similar systems, accretion is much more powerful: it determines how the white dwarf rotates, which makes it impossible to notice the beauty of contraction", - Popov explained.
Lomonosov Moscow State University
Related White Dwarf Articles:
For the first time, astronomers have used a novel method to determine the mass of a type of star known as a 'white dwarf' -- the shrunken corpse of a dead star that used to be like our sun.
Astronomers have used the sharp vision of NASA's Hubble Space Telescope to repeat a century-old test of Einstein's general theory of relativity.
Astronomers uncovered a moon orbiting the third largest dwarf planet, 2007 OR10, in the frigid outskirts of our solar system called the Kuiper Belt.
Sometimes a brown dwarf is actually a planet -- or planet-like anyway.
An international team of astronomers has identified a record breaking brown dwarf (a star too small for nuclear fusion) with the 'purest' composition and the highest mass yet known.
Astronomers have found a system of seven Earth-sized planets just 40 light-years away.
For the first time, scientists using NASA's Hubble Space Telescope have witnessed a massive object with the makeup of a comet being ripped apart and scattered in the atmosphere of a white dwarf, the burned-out remains of a compact star.
Scientists using the NASA/ESA Hubble Space Telescope have observed, for the first time, a massive, comet-like object that has been ripped apart and scattered in the atmosphere of a white dwarf.
Many scientists believe the Earth was initially dry and that water, carbon and nitrogen -- the building blocks for life -- likely came as a result of collisions with objects that began their lives in the cold outer reaches of our solar system.
An exotic binary star system 380 light-years away has been identified as an elusive white dwarf pulsar -- the first of its kind ever to be discovered in the universe -- thanks to research by the University of Warwick.
Related White Dwarf Reading:
Snow White and the Seven Dwarfs (Disney Classic) (Little Golden Book)
by RH Disney (Author), RH Disney (Illustrator)
Now new and old fans can relive the magic of Walt Disney's classic Snow White and the Seven Dwarfs as it is retold in a beautiful full-color Little Golden Book! View Details
Snow White and the Seven Dwarfs: The Story of Snow White (Disney Princess)
by Disney Book Group (Author), Disney Storybook Art Team (Illustrator)
Snow White is the fairest in the land. When the wicked queen wants that title for herself, Snow White flees into the forest where she meets the Seven Dwarfs. But the queen is determined to be the fairest in the land. Will Snow White ever escape her evil clutches and live happily ever after? This collectible storybook includes beautiful, full color art in the style of the beloved film, Snow White and the Seven Dwarfs. View Details
Snow and White Coloring Book: And Seven Dwarfs
by Clara Leith (Author)
• Inside the book you wil find 33 high quality illustrations
• Each image is printed on a separate page to prevent bleed-through.
• Perfect book for kids 3+
I would also really appreciate it if you could write a review View Details
Snow White and the Seven Dwarfs Coloring Book: A lovely A4 45 page coloring book on Snow White and the Seven Dwarfs with great fun scenes to color. Perfect for kids aged 3+.
by K W Books (Author)
A lovely A4 45 page coloring book on Snow White and the Seven Dwarfs with great fun scenes to color. Perfect for kids aged 3+ View Details
White Dwarf: First Deployment
by Paul Abbott (Author), Steven Pressfield (Editor), Amanda Brown (Editor), Layla Fisek (Editor), Kate McDaniels McDaniels (Editor)
With a brutal Gulf War pedigree, and in uniform as LAPD patrol officers, Harrington and Vendetti navigate the city’s sprawling terrain, encountering the desperate, the depraved, and the empty. What follows is a series of gruesome occurrences with no apparent logic to them. Allowed to witness their hate and vengeance, it appears they merely cause mayhem for mayhem’s sake. They steal, use, and sell drugs, but that’s only when they're not mutilating corpses or driving people to suicide. Theirs is a filthy and misogynistic world ruled by whores, drugs, and retribution. There is nobody in... View Details
Snow-White and the Seven Dwarfs: A Tale from the Brothers Grimm (Sunburst Book)
by Jacob Grimm (Author), Wilhelm K. Grimm (Author), Nancy Ekholm Burkert (Illustrator), Randall Jarrell (Illustrator)
Retells the tale of the beautiful princess whose lips were red as blood, skin was white as snow, and hair was as black as ebony.View Details
Snow White and the 77 Dwarfs
by Davide Cali (Author), Raphaelle Barbanegre (Illustrator)
Snow White is on the run from an evil witch when she comes across some dwarfs in the forest. They agree to take her in and keep her safe if she will help them with their chores. She soon realizes she's taking on a lot more than she bargained for. 77 breakfasts to make, 77 lunches to pack (don't forget the juice boxes!), 77 pairs of pants to mend and a whole lot of dishes. Eventually Snow White decides to take her chances with the witch. There's a surprise ending... well, it may not be so surprising. This is a hilarious retelling of the classic tale, with bright, energetic illustrations... View Details
Snow White and the Seven Dwarfs: The Art and Creation of Walt Disney's Classic Animated Film
by J.B. Kaufman (Author)
Released in 2012, in conjunction with the 75th anniversary of Snow White and the Seven Dwarfs, this book tells the fascinating story of the making of Walt Disney's groundbreaking animated classic. More than 250 artworks, including rarely seen concept sketches, background paintings, and cels illustrate the genius of Walt Disney and the creative vision of the artists who produced a beloved milestone in cinematic history.
In 1933, Walt Disney was a rising star in the world of animation, just beginning to become a household name. Ambitious new ideas emerged from the Disney studio... View Details
by Warren Mann (Author)
I looked into the mirror and sighed at what stared back. I was 120 pounds at six feet tall. My thick dark hair was wild and bushy—I had decided to let it grow out and it responded by becoming sentient. I was pale and my almost-black eyes were sunken and bloodshot. A steady diet of Coca-Cola, cigarettes, pot and insomnia had taken its toll. View Details
Snow White and the Seven Dwarfs (Read-Along Storybook and CD)
by Disney Storybook Art Team (Illustrator)
Snow White and the Seven Dwarfs View Details