MAP

Wednesday, 26 June 2013

Astronomers discover pulsations from crystalized dying star This discovery will allow scientists to see below the white dwarf’s atmosphere and into its interior. By McDonald Observatory at University of Texas, Austin — Published: June 24, 2013

Astronomers from the University of Texas at Austin and colleagues have used the 2.1-meter Otto Struve Telescope at the university's McDonald Observatory to discover pulsations from the crystalized remnant of a burnt-out star. The finding will allow astronomers to see below the star's atmosphere and into its interior, much like earthquakes allow geologists to study compositions below Earth's surface.

The Texas astronomers made their discovery in collaboration with astronomers from Brazil's Federal University of Rio Grande of the South, the University of Oklahoma, and the Smithsonian Astrophysical Observatory.

The star, GD 518, is roughly 170 light-years from Earth in the constellation Draco but far too faint to be seen without a telescope. It is a white dwarf, a star at the end of its life cycle that is essentially just a burnt-out core, the ashy byproduct of previous epochs of nuclear fusion. The star is unique in that much of it is likely suspended in a state more akin to a solid than a liquid or gas. The interiors of dying stars can become
crystalized similar to the way in which frigid water freezes into ice.

"GD 518 is special because it is a very massive white dwarf; it has about 1.2 times the mass of the Sun packed into a volume smaller than Earth," said J. J. Hermes, a graduate student at the University of Texas. "Few white dwarfs are endowed with so much mass, and this is by far the most massive white dwarf discovered to pulsate."

The star also likely has an interior composed of heavier elements than those found in typical burnt-out stars.

Our Sun will only get hot enough in its center for nuclear fusion to burn hydrogen into helium, and in turn the helium to carbon and oxygen. The Sun will end its life in more than 5 billion years as a white dwarf with its central regions composed mostly of the nuclei of carbon and oxygen atoms.

But unlike the Sun, the star that died to become the white dwarf GD 518 was so massive — probably more than seven times the Sun's mass — that it burned elements heavier than carbon and oxygen and is now likely a white dwarf composed of oxygen and neon nuclei.

The discovery of pulsations — periodic brightness changes on the surface of a star that, in this case, keep a regular tune every 400–600 seconds — will allow astronomers an unprecedented opportunity to understand what makes up this highly evolved star's interior.

"Like a child at a museum, astronomers are only allowed to look, not touch, when they perform experiments," said Barbara
Castanheira from the McDonald Observatory. "This means we usually can only understand the surface of a star. Pulsations, like the sound of a bell, tell us more of the story, since they can unravel secrets about the much deeper interior of a star."

White dwarf stars no longer fuse elements in their interior to generate energy — they simply cool like coal embers removed from a fire. But at a certain point, the atomic nuclei in the star's interior get cool enough to begin to settle into a lattice structure and
crystalize, just like water freezing into ice. This happens sooner in the interiors of more massive white dwarfs, and in the case of GD 518, it has likely started before the star had the right conditions to excite pulsations. The transition to a solid-like star should also affect the way the white dwarf vibrates from these pulsations.

Astronomers now face the difficult task of matching the pulsation periods observed in the star with those predicted by different models of the structure of its interior. The discovery observations show promise in this direction, Hermes said.

"We see evidence that the strength of pulsations in this star are very inconsistent; some nights the star is as still as a whisper," he said. "This could be because the white dwarf is highly
crystalized, and the pulsations are only allowed to propagate in a tiny bit of the outermost parts of the star. Thus, they have little inertia and are more susceptible to changes than the pulsations in a typical pulsating white dwarf."

University of Texas astronomers will continue watching GD 518 from McDonald Observatory, listening closely for any new notes that can unravel the song being sung by light from this
ultramassive dying star.

Sunday, 23 June 2013

Spectacular Sun Storm Sheds Light on Star Formation by Mike Wall, SPACE.com Senior WriterDate: 20 June 2013 Time: 02:01 PM ET

A stunning eruption unleashed by the sun two years ago is providing clues about how stars form, scientists say.
On June 7, 2011, the sun blasted out an enormous cloud of superheated plasma called acoronal mass ejection. Some of this material rained back down on the sun in a dazzling display that researchers say is helping them understand how newborn stars suck up plasma from their surroundings.
"This opens the way to new studies that link the sun to young stars, by both solar and stellar physicists," said study lead author Fabio Reale, of the University of Palermo and the Palermo Astronomical Observatory in Italy. [Watch video of the spectacular June 2011 solar eruption]
Newly forming stars siphon off material from a surrounding circumstellar disk. Such accretion plays a key role in the late phases of star formation, but the complex dynamics of the process — which involves plasma slamming into the stellar surface at hundreds of miles per second — make it difficult to understand in detail, researchers said.
The June 2011 solar eruption provides a window into the accretion process, Reale and his colleagues said. They studied images of the dramatic sun storm snapped by NASA's Solar Dynamics Observatory spacecraft in ultraviolet (UV) and extreme-UV light, and then compared those observations against the results of hydrodynamic simulations.
The team determined that the density (far more than 10 billion particles per cubic centimeter, or 164 billion particles per cubic inch) and impact velocity (670,000 to 1 million mph, or 1.1 million to 1.6 million km/h) of infalling material were similar to those seen during stellar accretion flows.
The sun on June 7, 2011, starting at about 06:41 UT, unleashed one of the most spectacular prominence eruptions ever observed.
CREDIT: SOHO (ESA & NASA)View full size image
Impacts were spread over a large fraction of the solar surface, researchers said. Sun-striking plasma blobs typically measured between 1,250 and 2,500 miles (2,000 to 4,000 km) in diameter, and they generated detectable high-energy emissions when they crashed into the sun.
Most stellar accretion flows emit surprisingly little high-energy light. The new study could help explain this puzzle, suggesting that such light is produced but absorbed by surrounding dense material, Reale said.
"The analysis of the high-energy light should be able to tell us about the composition of the disk material," he told SPACE.com via email.
It may seem odd that observations of this solar system's 4.5-billion-year-old sun can yield insights about stars just bursting into existence. But scientists use templates and proxies to investigate phenomena all the time, Reale said.
"Some physical processes are universal," he said. "If we can zoom in, and make the correct scaling and extrapolations, they can be investigated in different — even very different — systems. The sun has been used to study much brighter stellar coronae and flares, for instance. Probably, even people studying accretion in neutron stars or black holes may find this work interesting."
The new study was published today (June 20) in the journal Science.

Saturday, 22 June 2013

Giant Black Hole's Dust Oddity Surprises Scientists by Clara Moskowitz, SPACE.com Assistant Managing EditorDate: 20 June 2013 Time: 06:00 AM ET

The most detailed observations to date of the material surrounding a gigantic black hole have surprised scientists, who say what they see conflicts with common theories about these powerful objects.
Astronomers used the European Southern Observatory's Very Large Telescope Interferometer in Chile to observe the dust around the supermassive black hole at the center of the NGC 3783 galaxy, which lies tens of millions of light-years awayin the constellation Centaurus. The black hole, like many at the centers of galaxies, is gorging on a feast of mass that's fallen toward it from the surrounding area. As the dust falls in, it releases powerful radiation that can be spotted from across the universe.
When observing NGC 3783's center, the researchers expected to find almost all of the dust in the shape of a doughnut orbiting the black hole, but instead found significant amounts of material above and below the doughnut, or torus, shape. [Images: How Magnetic Fields Shape Black Holes]
The dust inside the doughnut is hot, reaching temperatures of 1,300 to 1,800 degrees Fahrenheit (700 to 1,000 degrees Celsius), but the dust that's been blown away has cooled down, the astronomers reported. A paper detailing the findings was published today (June 20) in the Astrophysical Journal by lead author Sebastian Hönig of the University of California, Santa Barbara and Christian-Albrechts-Universität zu Kiel in Germany, and his colleagues.
These observations suggest that the intense radiation produced when black holes feed on surrounding material also pushes some of this material outward. The discovery could lead to a "paradigm shift" in the understanding of how active supermassive black holes like this operate, scientists with the European Southern Observatory wrote in a statement.
"This is the first time we’ve been able to combine detailed mid-infrared observations of the cool, room-temperature dust around an AGN with similarly detailed observations of the very hot dust," Hönig said in a statement.
This image shows the region of sky around the active galaxy NGC 3783 in the southern constellation of Centaurus (The Centaur). The galaxy is the face-on spiral right at the center. Image released on June 20, 2013.
CREDIT: ESO/Digitized Sky Survey 2. Acknowledgement:
Davide De MartinView full size image
Astronomers hope to use this new knowledge to piece together a fuller picture of how black holes evolve within galaxies.
A new instrument being developed for the Very Large Telescope Interferometer called Matisse should help scientists gather even more detailed observations of super massive black holes. The Very Large Telescope Interferometer combines light from four separate telescopes to create extremely detailed amalgam observations.

"I am now really looking forward to Matisse, which will allow us to combine all four VLT Unit Telescopes at once and observe simultaneously in the near- and mid-infrared — giving us much more detailed data," Hönig said.

Thursday, 20 June 2013

OUT OF BOX THINKING’ IS ESSENTIAL IN BASIC SCIENCE

We can get success by using different assumptions [like different people find success by following their own god & religion]. Present theories are not the only way of success. Success comes because we are thinking more religiously on these theories.

If we think that by using the knowledge [property] of 4-6%[White (Baryonic) Matter], we have correctly explained or going to explain the 100%, then we are in confusion.
The knowledge of 76-74% [Dark Atom, Matter & Energy] may not change the process, effects & formula, but certainly changes the basic theory behind it.

Think why we are reaching iss in less than 6 hours instead of 51-52 hours?

Why universe is expanding instead of so many types of pulling force?

We should focus on the new theory based on dark matter, dark atom & dark energy. We cant ignore these, as previously.

Our mathematical approach is good, but it is for justifying/proving our assumption & theory not always for explaining theory & assumption

Take an example of gravitational force F=GMm/r²
                                                                    here the value of F depends on certain factors only, as shown in the formula. It is also true that this is proved many times.

But no one claim that the value of F at particular point is only due to above mentioned factor only. 

Let us take Virial theorem, is the reason of particular value of F is so simple?
At earth it is due to some different set of situation & at Neptune or at the planet of other stars [situated in another galaxy]; it is due to different set of situation.

GOD IS SIMPLE SO BASICS BEHIND HIS CREATURE MUST ALSO BE SIMPLE

I am not claiming that this concept is right or that concept is wrong [in my case, I have not yet given anything, because it is not a platform

All the new thought seems GARBAGE at first, but before throwing it in DUSTBIN, we must understand it with full Empathy & zero Halo effect. Scopes of amendment - ALWAYS EXISTS.

What you say when a SINGLE GARBAGE TYPE OF CONCEPT explain/re-explain the following- [using 74-76% with 6-4%]

Formation Of Galaxy, Regeneration Of Galaxy, Formation Of Black Hole, Formation Of S-Star, Types Of Galaxy, Reason of inter connecting arm, Formation Of Star, Regeneration of Stars, Why heavier metal comes out 1st during Supernova explosion?, Role of Temperature in the birth of Stars, Planet?, Formation of Planet, Satellite, Asteroid Belt, Kuiper Belt, About Jupiter, Saturn, Uranus, Neptune, About Pluto & Comet, Explain About Dooms Day-21.12.12 Situation, Reason Of Gravity, Why It Is More On Surface?, Why Satellite feels more pull towards the darker side of Moon?, Why Virial Theorem is very near to explain Gravitation?, Why Sun is hard to Hit by?, Why Universe is expanding, in spite of so many attractive force?, Why g is same for all objects?, Why Orbital velocity of planet increases near the Sun?, What is Dark Matter, Dark Atom & Dark Energy, where they Are? Why Dark Matter gone, which was more in early Earth?, Role of Dark Energy?, Source of Binding Energy?, Is number of Elements are only, what we see in Periodic Table?, Why water molecules immediately reach the chilled water bottle to lose Energy?, Why Oxygen rush to fire, carbon dioxide away, Why Oxygen go inside body, but comes out in Plant?, How Dark Matter, Dark Atom & Dark Energy interact with White Matter?, Why the value of Energy in E=mc² is more than the Calculated Value?, Why Number of Electron is proportional to number of Proton? Or Why Electron cloud holds only the same no. of Electron, as Proton in Nucleus? And many-many more

[Above topics are only a main topics, many sub-topics are also studied] 

Biology is also not much away.

[Regularly checking latest outcome published by/through leading journals/organisations in last 3 months with GARBAGE CONCEPTS outcome]

Ref. - my blogs & twitter, where I just start writing, but only few sentences because details are for sending in journal.

STILL CROSS CHECKING WITH DAILY PUBLISHED NEW PAPERS ON ABOVE TOPICS. 

NEED BIGGER PLATFORM TO CROSS CHECK THE CONCEPT? - because work is still on...



Saturday, 15 June 2013

Study explains decades of black hole observations 19 hours ago by Susan Gawlowicz

"We're accurately representing the real object and calculating the light an astronomer would actually see," says Scott Noble, associate research scientist in RIT's Center for Computational Relativity and Gravitation. "This is a first-of-a-kind calculation where we actually carry out all the pieces together. We start with the equations we expect the system to follow, and we solve those full equations on a supercomputer. That gives us the data with which we can then make the predictions of the X-ray spectrum."
Lead researcher Jeremy Schnittman, an astrophysicist at NASA's Goddard Space Flight Center, says the study looks at one of the most extreme physical environments in the universe: "Our work traces the complex motions, particle interactions and turbulent magnetic fields in billion-degree gas on the threshold of a black hole."
By analyzing a supercomputer simulation of gas flowing into a black hole, the team finds they can reproduce a range of important X-ray features long observed in active black holes.
"We've predicted and come to the same evidence that the observers have," Noble says. "This is very encouraging because it says we actually understand what's going on. If we made all the correct steps and we saw a totally different answer, we'd have to rethink what our model is."
Gas falling toward a black hole initially orbits around it and then accumulates into a flattened disk. The gas stored in this disk gradually spirals inward and becomes compressed and heated as it nears the center. Ultimately reaching temperatures up to 20 million degrees Fahrenheit (12 million C)—some 2,000 times hotter than the sun's surface—the gas shines brightly in low-energy, or soft, X-rays.
For more than 40 years, however, observations show that black holes also produce considerable amounts of "hard" X-rays, light with energy 10 to hundreds of times greater than soft X-rays. This higher-energy light implies the presence of correspondingly hotter gas, with temperatures reaching billions of degrees.
The new study bridges the gap between theory and observation, demonstrating that both hard and soft X-rays inevitably arise from gas spiraling toward a black hole.
Working with Noble and Julian Krolik, a professor at Johns Hopkins, Schnittman developed a process for modeling the inner region of a black hole's accretion disk, tracking the emission and movement of X-rays, and comparing the results to observations of real black holes.
Noble developed a computer simulation solving all of the equations governing the complex motion of inflowing gas and its associated magnetic fields near an accreting black hole. The rising temperature, density and speed of the infalling gas dramatically amplify magnetic fields threading through the disk, which then exert additional influence on the gas.
The result is a turbulent froth orbiting the black hole at speeds approaching the speed of light. The calculations simultaneously tracked the fluid, electrical and magnetic properties of the gas while also taking into account Einstein's theory of relativity.
Running on the Ranger supercomputer at the Texas Advanced Computing Center located at the University of Texas in Austin, Noble's simulation used 960 of Ranger's nearly 63,000 central processing units and took 27 days to complete.
Over the years, improved X-ray observations provided mounting evidence that hard X-rays originated in a hot, tenuous corona above the disk, a structure analogous to the hot corona that surrounds the sun.
"Astronomers also expected that the disk supported strong magnetic fields and hoped that these fields might bubble up out of it, creating the corona," Noble says. "But no one knew for sure if this really happened and, if it did, whether the X-rays produced would match what we observe."
Using the data generated by Noble's simulation, Schnittman and Krolik developed tools to track how X-rays were emitted, absorbed and scattered throughout both the accretion disk and the corona region. Combined, they demonstrate for the first time a direct connection between magnetic turbulence in the disk, the formation of a billion-degree corona, and the production of hard X-rays around an actively "feeding" black hole. Results from the study, "X-ray Spectra from Magnetohydrodynamic Simulations of Accreting Black Holes," were published in the June 1 issue of The Astrophysical Journal (ApJ, 769, 156).
In the corona, electrons and other particles move at appreciable fractions of the speed of light. When a low-energy X-ray from the disk travels through this region, it may collide with one of the fast-moving particles. The impact greatly increases the X-ray's energy through a process known as inverse Compton scattering.
"Black holes are truly exotic, with extraordinarily high temperatures, incredibly rapid motions and gravity exhibiting the full weirdness of general relativity," Krolik says. "But our calculations show we can understand a lot about them using only standard physics principles."
The study was based on a non-rotating black hole. The researchers are extending the results to spinning black holes, where rotation pulls the inner edge of the disk further inward and conditions become even more extreme. They also plan a detailed comparison of their results to the wealth of X-ray observations now archived by NASA and other institutions. Black holes are the densest objects known. Stellar-mass black holes form when massive stars run out of fuel and collapse, crushing up to 20 times the sun's mass into compact objects less than 75 miles (120 kilometers) wide.


Thursday, 13 June 2013

Where Is Dark Matter Most Dense? Subaru Telescope Gets Some Hints by ELIZABETH HOWELL on JUNE 13, 2013

Put another checkmark beside the “cold dark matter” theory. New observations by Japan’s Subaru Telescope are helping astronomers get a grip on the density of dark matter, this mysterious substance that pervades the universe.
We can’t see dark matter, which makes up an estimated 85 percent of the universe, but scientists can certainly measure its gravitational effects on galaxies, stars and other celestial residents. Particle physicists also are on the hunt for a “dark matter” particle — with some interesting results released a few weeks ago.
The latest experiment with Subaru measured 50 clusters of galaxies and found that the density of dark matter is largest in the center of these clusters, and smallest on the outskirts. These measurements are a close match to what is predicted by cold dark matter theory, scientists said.
Cold dark matter assumes that this material can’t be observed in any part of the electromagnetic spectrum, the band of light waves that ranges from high-energy X-rays to low-energy infrared heat. Also, the theory dictates that dark matter is made up of slow-moving particles that, because they collide with each other infrequently, are cold. So, the only way dark matter interacts with other particles is by gravity, scientists have said.
To check this out, Subaru peered at “gravitational lensing” in the sky — areas where the light of background objects are bent around dense, massive objects in front. Galaxy clusters are a prime example of these super-dense areas.
Several dark matter maps: one based on a sample of 50 individual galaxy clusters (left), another looking at an average galaxy cluster (center), and another based on dark matter theory (right). Red is the highest concentration of dark matter, followed by yellow, green and blue. At right, in the middle, is a map based on cold dark matter theory that comes close to the average galaxy cluster observed with the Suburu Telescope.
“The Subaru Telescope is a fantastic instrument for gravitational lensing measurements. It allows us to measure very precisely how the dark matter in galaxy clusters distorts light from distant galaxies and gauge tiny changes in the appearance of a huge number of faint galaxies,” stated Nobuhiro Okabe, an astronomer at Academia Sinica in Taiwan who led the study.
Next, the team members could compare where the matter was most dense with that predicted by cold dark matter theory. To do that, they measured 50 of the most massive, known clusters of galaxies. Then, they measured the “concentration parameter”, or the cluster’s average density.

“They found that the density of dark matter increases from the edges to the center of the cluster, and that the concentration parameter of galaxy clusters in the near universe aligns with CDM theory,” stated the National Astronomical Observatory of Japan.

The next step, researchers stated, is to measure dark matter density in the center of the galaxy clusters. This could reveal more about how this substance behaves. Check out more about this study in Astrophysical Journal Letters.


Alien Life Unlikely Around White and Brown Dwarfs, Study Finds Charles Q. Choi, Astrobiology Magazine Contributor Date: 05 June 2013 Time: 07:00 AM ET

The dead and failed stars known as white dwarfs and brown dwarfs can give off heat that can warm up worlds, but their cooling natures and harsh light make them unlikely to host life, researchers say.
Stars generally burn hydrogen to give off light and heat up nearby worlds. However, there are other bodies in space that can shine light as well, such as the failed stars known as brown dwarfs and the dead stars known as white dwarfs.
White dwarfs are remnants of normal stars that have burned all the hydrogen in their cores. Still, they can remain hot enough to warm nearby planets for billions of years. Planets around white dwarfs might include the rocky cores of worlds that were in orbit before the star that became the white dwarf perished; new planets might also emerge from envelopes of gas and dust around white dwarfs.
Brown dwarfs are gaseous bodies that are larger than the heaviest planets but smaller than the lightest stars. This means they are too low in mass for their cores to squeeze hydrogen with enough pressure to support nuclear fusion like regular stars.
Still, the gravitational energy from their contractions does get converted to heat, meaning they can warm their surroundings. NASA's WISE spacecraft and other telescopes have recently discovered hundreds of brown dwarfs, raising the possibility of detecting exoplanets circling them; scientists have already observed protoplanetary disks around a few of them.
White dwarfs and brown dwarfs are bright enough to support habitable zones — regions around them warm enough for planets to sustain liquid water on their surfaces. As such, worlds orbiting them might be able support alien life as we know it, as there is life virtually everywhere there is water on Earth.
"These planets could be like the Earth, but they are relatively unstudied," said study lead author Rory Barnes, a planetary scientist and astrobiologist at the University of Washington at Seattle.
An added benefit of looking for exoplanets around these dwarfs is that they might be easier to detect than ones around regular stars. These dwarfs are relatively small and faint, meaning any worlds that pass in front of them would dim them more noticeably than planets crossing in front of normal stars.
Shifting habitable zones
However, unlike regular stars, white dwarfs and brown dwarfs cool as they age, meaning their habitable zones will move inward over time. Barnes and his colleague René Heller at the Leibniz Institute for Astrophysics Potsdam in Germany were curious as to whether this complicated the habitability of planets there.
The most obvious peril of a shifting habitable zone is that it could result in a planet getting so cold all the liquid water on its surface freezes solid. There are other dangers, however — as white dwarfs and brown dwarfs cool, the light they give off would change as well, possibly meaning they would end up sterilizing worlds with dangerous, high-energy radiation.
To be specific, extreme ultraviolet rays would break a planet's water apart into hydrogen and oxygen. The hydrogen can escape into space, and without hydrogen to bond with oxygen, the world has no water and is not habitable.
This artist’s impression shows the disc of gas and cosmic dust around a brown dwarf.
CREDIT: ALMA (ESO/NAOJ/NRAO)/M.
Kornmesser (ESO)View full size image
Such exoplanets would resemble Venus, with dry atmospheres dominated by carbon dioxide. Young white dwarf stars would bathe nearby planets in extreme ultraviolet radiation; the situation is less clear with brown dwarfs, Barnes and Heller said.
In addition, because white dwarfs and brown dwarfs are so dim, their habitable zones already start off very near them — about one-hundredth the distance between the sun and Earth, which is about one-thirtieth the distance between the sun and Mercury.
At such close distances, the gravitational pull of the dwarfs will significantly flex and heat planets, just as the moon's gravitational tug on Earth results in tides. Too much heating can cause planets to lose all their water, becoming what Barnes and his colleagues dub "tidal Venuses."
Frustratingly, water-rich planets that lose their hydrogen may develop oxygen-rich atmospheres, which astronomers might mistake as a sign of life, the investigators said. Oxygen usually does not stay long in atmospheres — as such, detecting it on an alien world might suggest to scientists that organisms such as plants exist there to generate the gas. [9 Exoplanets That Could Host Alien Life]
Inhospitable white dwarfs
White dwarfs should tidally heat planets more than brown dwarfs, since white dwarves are so massive, the researchers noted. White dwarfs are only about the size of the Earth, but they are remarkably dense, with masses nearly two-thirds that of the sun.
All in all, the scientists found it unlikely that planets orbiting white dwarfs would ever be truly habitable. When they are young, white dwarfs would blast planets in their habitable zones with ultraviolet rays that would strip the worlds of water; when they grow older, their habitable zones would shift closer to them, and the amount of tidal heating might also end up desiccating any planets residing in those zones.
To look at what planets around white dwarfs might be like, the scientists analyzed two exoplanet candidates orbiting the star KOI 55, which will soon die and become a white dwarf.
The star, which is about half the mass of the sun, lies about 3,850 light years away, and the putative worlds KOI 55.01 and KOI 55.02, discovered by NASA's Kepler mission, are about two-fifths and two-thirds the mass of the Earth, respectively.
If these candidates do exist, these roughly Earth-sized exoplanets will fall within the habitable zone of KOI 55 when it becomes a white dwarf. However, these worlds are currently roasting under the star's heat and probably losing their water, if they had any, and are therefore unlikely to become habitable later, the researchers said. Gravitational interactions between the exoplanets may also cause sterilizing levels of tidal heating. [A World of Kepler Planets (Gallery)]
Planets orbiting brown dwarfs also run the risk of never achieving habitable conditions, but they may have a slightly better chance than worlds around white dwarfs, the researchers found. Catastrophic tidal heating remains a problem — because these stars are dim, planets must orbit relatively close in to receive enough light to be habitable, but the chances are that tidal forces might simply tear apart planets that are so close to their star.
Not impossible
Although the chances for life around white dwarfs and brown dwarfs might look slim, they are not zero, the scientists cautioned. "I'm not arguing that all planets around brown dwarfs and white dwarfs are uninhabitable," Barnes said, "just that they have more hurdles to clear."
For instance, a planet might drift into the habitable zone of a white dwarf from a more distant orbit long after the formation of that dead star. It would still have to contend with tidal heating, but it would have avoided radiation that likely would have sterilized its surface.
"The biggest question in my mind is regarding the loss of water," Barnes added. "We don't have a good handle on that process, and also don't know how much water these planets could have to begin with. Therefore estimating the time it takes to lose all water, and hence be uninhabitable, is difficult to quantify at present. It could be that some of these planets retain enough water that, as the habitable zone reaches them, they could still support life."
"I believe that the topic of habitability of planets around brown dwarfs should be investigated more," said astrophysicist Emeline Bolmont at the Astrophysics Laboratory of Bordeaux in France, who did not take part in this study. "However, we would need observation missions to observe planets around brown dwarfs. Such a mission requires a long observation time, and brown dwarfs are very faint objects, so it will not be easy."
Still, Bolmont said he thought a proposal aiming to observe planets around brown dwarfs might be accepted in a few years. "If a planet were observed in transit, the [soon-to-be launched] James Webb Space Telescope would be able to probe its atmosphere and teach us a lot about its composition," Bolmont said.

More research is needed to understand how planets orbiting white dwarfs and brown dwarfs form, and "particularly the amount of water they form with," Barnes said. "We also need to understand how the high-energy radiation of brown dwarfs evolves with time. This is the energy that can remove water, but we don't have any idea how strong it can be, and how long it lasts."