Cloudy with a chance of molten iron

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The first weather map of an unusual type of star called a brown dwarf has revealed a world where it rains molten iron.

The research reported in separate studies in Nature and Astrophysical Journal Letters, has provided astronomers with their clearest view yet of the complicated atmospheric processes occurring in these strange worlds.

A brown dwarf is a low-temperature star that has failed to accumulate enough mass to reach the core temperatures and pressures needed to ignite. Some astronomers suggest brown dwarfs bridge the gap between the largest planets and the smallest stars.

Astronomers used the European Southern Observatory's Very Large Telescope in Chile to directly map out lighter and darker patches on the surface of a brown dwarf known as Luhman 16B.

Located just 6.5 light years away, in the southern constellation of Vela the Sail, Luhman 16B is one half of a pair of brown dwarfs discovered last year.

Written By: Stuart Gary
continue to source article at abc.net.au

17 COMMENTS

  1. The first weather map of an unusual type of star called a brown dwarf has revealed a world where it rains molten iron.

    This iron rain is likely to be because it is in the vicinity of the Solar System where the metallicity is quite high in this part of the galaxy.

    A brown dwarf is a low-temperature star that has failed to accumulate enough mass to reach the core temperatures and pressures needed to ignite.

    That is not enough to ignite a hydrogen fusion reaction.

    • In reply to #1 by Alan4discussion:

      A brown dwarf is a low-temperature star that has failed to accumulate enough mass to reach the core temperatures and pressures >needed to ignite.

      That is not enough to ignite a hydrogen fusion reaction.

      This is interesting. A point on terminology, please. A brown dwarf is a star, but is it a sun? Is hydrogen fusion a defining characteristic of a sun? Or are ‘star’ and ‘sun’ interchangeable?

      • In reply to #2 by Cairsley:

        This is interesting. A point on terminology, please. A brown dwarf is a star, but is it a sun? Is hydrogen fusion a defining characteristic of a sun? Or are ‘star’ and ‘sun’ interchangeable?

        Good question. I think the ABC report is wrong and it’s not called a star but a sub-stellar object. I think there is only one sun which is ours. I don’t think any other stars are called suns.

        Michael

          • In reply to #4 by phil rimmer:

            In reply to #3 by mmurray:

            sun

            3) any star around which planets move

            “Sun” is not really our star’s name either. Sometimes it is called Sol (Latin, but I like to think also a nice good Jewish name….)

            Thanks Phil and Alan. I stand corrected. So now that we know there are other planets beyond this solar system we have a convenient name for the stars they orbit — suns.

            Michael

          • In reply to #4 by phil rimmer:

            “Sun” is not really our star’s name either. Sometimes it is called Sol

            That is likely to cause confusion because the term “SOL” is used by NASA for a Martian day.

            http://en.wikipedia.org/wiki/Timekeeping-on-Mars

            The average length of a Martian sidereal day is 24h 37m 22.663s (based on SI units), and the length of its solar day (often called a sol) is 88,775.24409 seconds or 24h 39m 35.24409s. The corresponding values for Earth are 23h 56m 4.0916s and 24h 00m 00.002s, respectively. This yields a conversion factor of 1.027491 days/sol. Thus Mars’s solar day is only about 2.7% longer than Earth’s.

            http://www.thefreedictionary.com/Sun+%28astronomy%29

            sun

            • 3, The radiant energy, especially heat and visible light, emitted by the sun; sunshine.

            I presume “sol” derives from the other meaning of “sun”, which is “sunlight”.

        • In reply to #3 by mmurray:

          In reply to #2 by Cairsley:

          This is interesting. A point on terminology, please. A brown dwarf is a star, but is it a sun? Is hydrogen fusion a defining characteristic of a sun? Or are ‘star’ and ‘sun’ interchangeable?

          Good question. I think the ABC report is wrong and it’s not called a star but a sub-stellar object. I think there is only one sun which is ours. I don’t think any other stars are called suns.

          One of the problems with terminology in astronomy is that the labels were often invented before the classes of objects were known.

          http://www.thefreedictionary.com/Sun+%28astronomy%29
          >
          sun (sŭn) -n.
          >
          1. often Sun A star that is the basis of the solar system and that sustains life on Earth, being the source of heat and light. It has a mean distance from Earth of about 150 million kilometers (93 million miles) a diameter of approximately 1,390,000 kilometers (864,000 miles) and a mass about 330,000 times that of Earth.
          2. A star that is the center of a planetary system.

          I have a personal convention of capital letters which I use in astronomy (although others also use this).
          ie – That the Sun is the centre of the Solar -System, and a sun is the centre of a solar-system (or star/planetary system). Similarly the Moon is Earth’s moon and a moon is the moon of another planet.

          I also use this in Earth sciences when talking about the planet Earth and the fertile earth of soil science and agriculture.

          Cairsley: – This is interesting. A point on terminology, please. A brown dwarf is a star, but is it a sun? Is hydrogen fusion a defining characteristic of a sun? Or are ‘star’ and ‘sun’ interchangeable?

          As Michael points out, the terminology is evolving as we gain information. While the nature of stars and planets is largely determined by size and composition, I think bodies have been classed as stars if they emit visible light, rather than being determined by the ignition of hydrogen fusion. Hydrogen fusion is however a good star classification tool, as many planets, including Earth, generate some heat from internal radioactive decay. There may be revisions of terminology as understanding progresses.

    • In reply to #1 by Alan4discussion:

      >

      This iron rain is likely to be because it is in the vicinity of the Solar System where the metallicity is quite high in this part of the galaxy.

      Correct me if I am wrong but I believe there is a theory (or more likely a hypothesis) that the Sun was born in another region of the Galaxy and migrated here. It is possible that the Sun and Luhman 16B were born in two entirely separate stellar nurseries, though I have no idea how likely that possibility is.

      • In reply to #8 by SomersetJohn:

        In reply to #1 by Alan4discussion:

        Correct me if I am wrong but I believe there is a theory (or more likely a hypothesis) that the Sun was born in another region of the Galaxy and migrated here.

        The Sun is orbiting the galactic centre at 828,000 km/hr. so it certainly originated away from its present position.

        It is possible that the Sun and Luhman 16B were born in two entirely separate stellar nurseries, though I have no idea how likely that possibility is.

        That is possible if either of them was thrown out of position by earlier gravitational interactions. However star clusters do tend to stay together unless perturbed by other passing bodies or collisions. 6.5 light years away is very close in galactic or star-cluster terms.

        http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question18.html
        >

        the Sun – in fact, our whole solar system – orbits around the center of the Milky Way Galaxy. We are moving at an average velocity of 828,000 km/hr. But even at that high rate, it still takes us about 230 million years to make one complete orbit around the Milky Way!

        The Milky Way is a spiral galaxy. We believe that it consists of a central bulge, 4 major arms, and several shorter arm segments. The Sun (and, of course, the rest of our solar system) is located near the Orion arm, between two major arms (Perseus and Sagittarius). The diameter of the Milky Way is about 100,000 light-years and the Sun is located about 28,000 light-years from the Galactic Center. You can see a drawing of the Milky Way below [see link] which shows what our Galaxy would look like “face-on” and the direction in which it would spin as viewed from that vantage point. Also shown, is the location of the Sun in the big picture view of our Galaxy.

        http://en.wikipedia.org/wiki/Galactic-year
        >

        The galactic year, also known as a cosmic year, is the duration of time required for the Solar System to orbit once around the center of the Milky Way Galaxy.[1] Estimates of the length of one orbit range from 225 to 250 million “terrestrial” years.[2] According to NASA, the Solar System is traveling at an average speed of 828,000 km/h (230 km/s) or 514,000 mph (143 mi/s) relative to the galactic center,[3] which is about one 1300th of the speed of light. If you could travel at that speed in a jet aircraft along the equator, you would go all the way around the world in approximately 2 minutes and 54 seconds.

        • The Sun is orbiting the galactic centre at 828,000 km/hr. so it certainly originated away from its present position.

          And the whole galaxy is moving even faster than that, but relative to what? It’s a lot to take in.

          In reply to #11 by Alan4discussion:

          In reply to #8 by SomersetJohn:

          In reply to #1 by Alan4discussion:

          Correct me if I am wrong but I believe there is a theory (or more likely a hypothesis) that the Sun was born in another region of the Galaxy and migrated here.

          The Sun is orbiting the galactic centre at 828,000 km/hr. so it certa…

          • In reply to #12 by Marktony:

            The Sun is orbiting the galactic centre at 828,000 km/hr. so it certainly originated away from its present position.

            And the whole galaxy is moving even faster than that, but relative to what? It’s a lot to take in.

            Various parts of the universe are moving relative to each other, but as far as our galaxy is concerned, the relative movement of Andromeda is probably most relevant.

            http://www.spaceanswers.com/deep-space/2033/if-the-universe-is-expanding-why-are-we-on-a-collision-course-with-the-andromeda-galaxy/
            >

            The expansion of the Universe, as measurements carried out by astronomer Edwin Hubble in the 1920s show, mean that galaxies are rushing away from us at a rate, recently measured by today’s cosmologists, to be 74 kilometres per second per megaparsec (where one megaparsec equals around 3.26 million light years).

            While it is easy to envision all galaxies moving away from each other, the evidence of smash-ups between these gigantic structures litter the Universe. This means that galaxies are both moving away and crashing into one another – this happens much more often than you think.

            So often, in fact, that our galactic neighbour, Andromeda is moving towards the Milky Way Galaxy at around 250,000 miles per hour – a speed that would get you to the Moon in about an hour.

            Why this is so is all thanks to the gravity of the dark matter surrounding the pair, knitting them together so tightly, that they resist the expansion of the Universe and are instead, drawn together with Andromeda falling towards us. As you may have read in our feature on the Andromeda Galaxy in issue 6 of All About Space, we are unlikely to see the spectacular collision as our Sun evolves and extinguishes life on our planet’s surface.

            However, when the inevitable does happen, and the two coalesce, they will create a single elliptical galaxy with the merger triggering a great burst of star formation and the supermassive black holes that sit at the hearts of both galaxies will combine. While stars in both the Milky Way and Andromeda are unlikely to collide due to their great distances, the gravitational disturbance could cause what is left of our Solar System to change its position – tossing it from its current position in the Orion spur and further from the Milky Way’s core.

            The galaxy merging does not end there either; Andromeda’s companion, the Triangulum Galaxy – which is also attached by dark matter to the pair – will join the collision, taking another two billion years to merge with “Milkomeda” completely.

          • In reply to #13 by Alan4discussion:

            In reply to #12 by Marktony:

            The Sun is orbiting the galactic centre at 828,000 km/hr. so it certainly originated away from its present position.

            And the whole galaxy is moving even faster than that, but relative to what? It’s a lot to take in.

            Is it known if any other major galaxies have merged …If the milky way is at right angles to andromeda…..how will that affect the merging ? Would a roughly spherical super galaxy occur after their merging ?
            Thanks for all the brilliant info you always supply ….

            >

          • In reply to #14 by Light Wave:

            Is it known if any other major galaxies have merged …If the milky way is at right angles to andromeda…..how will that affect the merging ? Would a roughly spherical super galaxy occur after their merging ? Thanks for all the brilliant info you always supply ….

            Large galaxies have built up by smaller galaxies merging.. The disk form would probably be partially preserved, but with all sorts of odd eccentric orbits further out and some stars thrown out into deep space away from the galaxies. There would be lots of perturbation of galactic and planetary orbits until things settled down. – as shown in the animations linked below.

            750,000,000 AD – The Sagittarius dwarf galaxy has been absorbed into the larger Milky Way – http://www.futuretimeline.net/beyond.htm#sagittarius

            1min 17 sec Milky Way – Andromeda Collision Animation -http://www.youtube.com/watch?v=mzgGhpAu2-I

            4min 8sec Andromeda/Milky Way collision (simulation)

            It is quite amusingly strange, when deluded faith-thinkers – with Dunnig-Kruger confidence, explain to me how Genesis, with a “metaphorical” flat Earth under heavenly crystal domes, really explains all these mechanisms.

          • In reply to #15 by Alan4discussion:

            In reply to #14 by Light Wave:

            Is it known if any other major galaxies have merged …If the milky way is at right angles to andromeda…..how will that affect the merging ? Would a roughly spherical super galaxy occur after their merging ? Thanks for all the brilliant info you always supply …….

            The animation is like a magnetic mating dance or something elegant and alive….but surely it will be pretty deadly for some solar systems but not all ?
            Would only one super massive black hole remain at its centre ? or can more than one co – exist ?

          • In reply to #16 by Light Wave:

            In reply to #15 by Alan4discussion:

            The animation is like a magnetic mating dance or something elegant and alive….but surely it will be pretty deadly for some solar systems but not all ?

            Generally stars would be too far apart for many collisions, but gravitational perturbations could cause showers of meteorites or comets to bombard planets. Passing stars could also drag planets into elliptical orbits.

            If humans still survived, we would need to have got organised before this time, as the Sun would probably have engulfed or fried Earth by then.

            Would only one super massive black hole remain at its centre ? or can more than one co – exist ?

            There are already smaller black holes within the Milkyway, but the black holes at the galactic centres could merge eventually. – Not a place to be near while it was happening!

            On the plus side, with all those stars flying past each other, a space-faring species, could hop into passing solar-systems which would otherwise be out of range. That would be likely to be a one-way ticket, so a careful choice would be advisable.

  2. In reply to #7 by Alan4discussion:

    In reply to #4 by phil rimmer:

    “Sun” is not really our star’s name either. Sometimes it is called Sol

    That is likely to cause confusion because the term “SOL” is used by NASA for a Martian day.

    The use is historical and in no sense currently official.
    In the early modern period Latin was the language of science, so sol, solis (m) got used. SF writers seemed to rather like it too…

    It seems a pity to use the term up for just Mars though. As a generic for “day” on any planet or axial rotator in a solar system, to avoid confusion with 24hrs would have been better.

    sol defn. The periodicity of insolation …….or some such???

    • In reply to #9 by phil rimmer:

      In reply to #7 by Alan4discussion:

      It seems a pity to use the term up for just Mars though. As a generic for “day” on any planet or axial rotator in a solar system, to avoid confusion with 24hrs would have been better.

      I think that will be the eventual usage, but Mars is the only planet where landers are currently operating in “daylight” and where “sols” need to be recorded on a local planetary calendar, to avoid confusion with Earth “days”.

      sol defn. The periodicity of insolation …….or some such???

      Plus the individual planet’s name: – Sounds like a good clear definition!

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