WHAT IS A BROWN DWARF - A PLANET OR A STAR?

we are quite used to perceiving stars as something enormous and bright that has been around for millions and billions of years but just imagine that the planets you live on were located near a jupiter-sized star whose luminosity was slightly stronger than that of a dying amber in a fireplace this would be a gloomy world with no future to speak of it would be doomed to slowly cool off and eventually find itself in eternal darkness and cold [Music] cosmo the first in outer space it may be hard to imagine but our sun which is relatively small for a star is heavier than any of 95 percent of stars in the universe there are also such things as red dwarves 11 times lighter than our host star however they're actually not the lightest objects out there in the wide range between gas giants and the smallest stars in the universe there are some fascinating objects known as brown dwarves or dwarf stars to understand their nature let's have a look at how a star is born according to modern scientific theories stars and brown dwarves originate in the same star nursery when nebulae made up of interstellar gas gradually contract under the influence of gravitational forces pressure and temperature inside the gas increase the enormous nebulae disintegrate into a great number of proto-stellar discs and each of them has a chance of becoming a fully-fledged star at some point its destiny depends on how much matter the young star will manage to capture if the mass of a protest star is over 8 percent of that of the sun thermonuclear reactions are bound to start in its interior nuclei of light elements like hydrogen deuterium helium or lithium blend together emitting a great amount of heat this heats up the interior of the future star even more and more and more matter is involved in these processes this unleashes a chain reaction which may persevere for billions of years until the substances fueling it are totally and so an used star is born somewhere light years away from us and can probably be observed in the sky its future depends on its mass and chemical composition most of its life cycle will be spent in the main sequence phase later the star is likely to turn into a white dwarf or alternatively a neutron star or a black hole but what if the mass of the forming protest star is smaller then the gravitational pressure will not be enough for the heat produced by the thermonuclear reaction to increase the star's temperature to the point when it is able to sustain the burning process without additional help from other sources nuclear fusion will still take place but the heat emitted during the process will not be enough for the star to flare up instead the object will slowly decay until the substance is necessary for thermonuclear reactions are depleted it's worth mentioning that every kind of reaction requires a certain temperature to initiate nuclear fusion if the star's temperature is lower nuclei will not be able to get closer and will be mutually repelled by coulomb force the celestial object we're looking at today is what is known as a brown dwarf in space interestingly in spite of their name not many of them are actually of a brownish hue if we could look at them with a naked eye we would most likely see them crimson orange or even black the color depending on the surface temperature the hottest brown dwarfs have a temperature not higher than 3000 degrees kelvin which corresponds to a faint red glow most of them are much colder from 300 to a couple of thousand degrees kelvin the peak in their radiation is in the infrared range which is invisible to the naked eye just to compare the coolest star's surface temperature is about 4000 degrees kelvin by radiating heat into its environment a brown dwarf gradually depletes its energy and cools off thermonuclear reactions in its interior die down and the object turns into a ball of compressed gas it will cool off gradually and will resemble a gas giant of impressive dimensions after its heat is slowly dissipated a brown dwarf may in theory cool off to as little as four or five degrees kelvin the background temperature of the universe's relic radiation however the temperature of the coolest space objects of this variety that have been discovered are about 300 degrees kelvin there are several celestial objects that may yet earn the title of a brown dwarf one of them is wise six five 1828-2650 it is in the lyra constellation and is 47 light years away from the sun it is considered the coldest brown dwarf to have been discovered although astronomers make scientific contributions every day and perhaps we will soon hear of still cooler objects a brown dwarf's dimensions are usually comparable to those of jupiter while its masses several dozen times that of jupiter for example the object coro 3b in the constellation aquila about 2 200 light years from the earth is similar to jupiter in its diameter but is 22 times heavier a space object qualifies to be called a brown dwarf if its mass is approximately 12 and a half to 80 times that of jupiter objects heavier than that are red dwarves those lighter than that are sub-brown dwarfs super jupiters and planimos it goes without saying that such small and dim celestial bodies are practically impossible to see with a regular telescope the existence of these fascinating objects was predicted back in the 1960s although even special infrared detectors were unable to spot brown dwarves for a long time many years passed before the first brown dwarf had been detected the great event took place in 1995. the find was an object dubbed tayder 1 a rather hot celestial body for its class it is located in the constellation taurus approximately 400 light years away from the sun its surface temperature reaches 2 700 degrees kelvin and its mass is 55 times that of jupiter or 5.2 percent that of the sun in the years that followed a great number of other celestial bodies of this class were discovered about 100 of them were detected within as little a radius as 60 light years from the sun the total number of brown dwarves in our galaxy is estimated at 50 to 100 billion which accounts for about a quarter of the overall number of stars in the milky way the brown dwarf closest to the earth is just nine light years away from the sun brown dwarves are rather cool objects by stellar standards that is why they may contain complex compounds like methane as for the temperature of the coolest main sequence stars it is so high that electrons leave their nuclei and thus the substance turns into scorching plasma even the simplest two atom molecules like hydrogen cannot endure this harsh environment there may be planets orbiting brown dwarfs the first satellite of this kind was detected in 2004 it orbits 2m1207 a comparatively warm brown dwarf in the constellation centauri which is 64.6 or 209 light years away from the earth this planet is rather large its mass is four times that of jupiter can the planets orbiting brown dwarfs be habitable it is positive that the chances are slim but theoretically it is feasible since brown dwarves are much cooler than stars their habitable zone is narrower concentrating closer to the parent dwarf also it should be noted that the eccentricity of the satellite planet's orbit should be low that is practically ideally spherical in shape since a brown dwarf is constantly in the process of cooling its habitable zone gradually shifts closer to it according to some estimates a rather heavy and hot dwarf may sustain conditions suitable for life on its satellite planet for as long as 10 billion years but of course there are admittedly many other objects in the universe which are definitely more favorable for cultivating life i wonder what you think about chances of discovering even primitive life forms close to these harsh celestial bodies feel free to leave your ideas in the comments it is always nice to get some feedback from you it motivates us to make new videos of competitive 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Channel: Kosmo

Views: 42,398

Rating: 4.9135408 out of 5

Keywords: brown dwarf, star, gas planet, dwarf, planet, gas giant, jupiter, universe, astronomy, space, cosmos, popular science, stellar evolution, science, black hole, video about space, the coldest star in the universe, cosmo, kosmo, the first in outer space, dwarf planets, facts, sun

Id: zLL6CoMjVxU

Length: 10min 16sec (616 seconds)

Published: Sat Nov 21 2020