Bonn: Enigma of the missing stars in space may be solved

[bystander]

The enigma of the missing stars in space may be solved
University of Bonn | University of St. Andrews | 18 Nov 2010

Researchers from Bonn and St. Andrews provide an explanation for the discrepancy

In the local group of galaxies that also includes the Andromeda Nebula and our Milky Way, there are about 100 billion stars. According to astronomers’ calculations, there should be many more. Now, physicists from the University of Bonn and the University of St. Andrews in Scotland may have found an explanation for this discrepancy. Their study will appear in the upcoming issue of the Monthly Notices of the Royal Astronomical Society.

New stars are born in the Universe around the clock – on the Milky Way, currently about ten per year. From the birth rate in the past, we can generally calculate how populated space should actually be. But the problem is that the results of such calculations do not match our actual observations. ...

For years, astronomers worldwide have been looking for a plausible explanation for this discrepancy. In cooperation with Dr. Carsten Weidner from St. Andrews University, Dr. Pflamm-Altenburg and Professor Dr. Pavel Kroupa, Professor of Astrophysics at the University of Bonn, may now have found the solution. It seems that so far, the birth rate has simply been overestimated. But this answer is not quite as simple as it sounds. Apparently, the error of estimation only occurs during periods of particularly high star production.
...
In our immediate vicinity, these large whoppers occur with a fixed probability. There are always about 300 lightweights to one “big star baby.” This numerical ratio seemed to be universal. So it was sufficient for astronomers to know the number of the large whoppers, for this allowed them to determine the number of new-born stars by simply multiplying the former number by a factor of 300.

Recently, however, some Bonn astronomers around Professor Kroupa began doubting the fixed ratio. Their hypothesis is that at times when the galactic nurseries are booming, they generate a considerably higher number of stellar heavies than normal. The reason for this, according to this theory, is so-called stellar crowding. For stars are not single children; they are born in groups, as so-called star clusters. At birth, these clusters are always of a similar size – no matter whether they contain 100 star embryos - or 100,000.

Consequently, at times of a high birth rate, space can be at a premium in star clusters. Astronomers call such galaxies that are particularly rich in mass “ultra-compact dwarf galaxies,” or UCD’s for short. In these, things are so tight that some of the young stars fuse during formation. Thus, more stars rich in mass than normal emerge. The “small to large” ratio is then only about 50 to 1.

Top-heavy integrated galactic stellar initial mass functions (IGIMFs) in starbursts - C Weidner, P Kroupa, J Pflamm-Altenburg

• arXiv.org > astro-ph > arXiv:1011.3814 > 16 Nov 2010

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X-ray images of the Pleiades reveal stars with the hottest atmospheres. Green squares indicate the 7 optically brightest stars.

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<<The Pleiades (Messier object 45) is an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus. The cluster core radius is about 8 light years and tidal radius is about 43 light years. The cluster contains over 1,000 statistically confirmed members, although this figure excludes unresolved binary stars. It is dominated by young, hot blue stars, up to 14 of which can be seen with the naked eye depending on local observing conditions. The total mass contained in the cluster is estimated to be about 800 solar masses.

The cluster contains many brown dwarfs, which are objects with less than about 8% of the Sun's mass, not heavy enough for nuclear fusion reactions to start in their cores and become proper stars. They may constitute up to 25% of the total population of the cluster, although they contribute less than 2% of the total mass. Astronomers have made great efforts to find and analyse brown dwarfs in the Pleiades and other young clusters, because they are still relatively bright and observable, while brown dwarfs in older clusters have faded and are much more difficult to study.>>

Astronomy Without A Telescope – Brown Dwarfs Are Magnetic Too
Written by Steve Nerlich July 17th, 2010

Brown dwarf TWA 5B compared with the Sun and Jupiter. Although brown dwarfs are similar in size to Jupiter, they are much more dense and massive - between 13 and 80 Jupiter masses. Credit: chandra.harvard.edu

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<<I feel a certain empathy for brown dwarfs. The first confirmed finding of one was only fifteen years ago and they remain frequently overlooked in most significant astronomical surveys. I mean OK, they can only (stifles laughter) burn deuterium but that's something, isn't it?

It has been suggested that a clever way of finding more brown dwarfs is in the radio spectrum. A brown dwarf with a strong magnetic field and a modicum of stellar wind should produce an electron cyclotron maser. Roughly speaking (something you can always depend on from this writer), electrons caught in a magnetic field are spun energetically in a tight circle, stimulating the emission of microwaves in a particular plane from the star's polar regions. So you get a maser, essentially the microwave version of a laser, that would be visible on Earth – if we are in line of sight of it.

While the maser effect can probably be weakly generated by isolated brown dwarfs, it's more likely we will detect one in binary association with a less mass-challenged star that is capable of generating a more vigorous stellar wind to interact with the brown dwarf's magnetic field. This maser effect is also proposed to offer a clever way of finding exoplanets. An exoplanet could easily outshine its host star in the radio spectrum if its magnetic field is powerful enough. So far, searches for confirmed radio emissions from brown dwarfs or orbiting bodies around other stars have been unsuccessful, but this may become achievable in the near future with the steadily growing resolution of the European LOw Frequency ARray (LOFAR), which will be the best such instrument around until the Square Kilometer Array (SKA) is built – which won't be seeing first light before at least 2017.

But even if we can't see brown dwarfs and exoplanets in radio yet, we can start developing profiles of likely candidates. Christensen and others have derived a magnetic scaling relationship for small scale celestial objects, which delivers predictions that fit well with observations of solar system planets and low mass main sequence stars in the K and M spectral classes (remembering the spectral class mantra Old Backyard Astronomers Feel Good Knowing Mnemonics). Using the Christensen model, it's thought that brown dwarfs of about 70 Jupiter masses may have magnetic fields in the order of several kilo-Gauss in their first hundred million years of life, as they burn deuterium and spin fast. However, as they age, their magnetic field is likely to weaken as deuterium burning and spin rate declines.

Brown dwarfs with declining deuterium burning (due to age or smaller starting mass) may have magnetic fields similar to giant exoplanets, anywhere from 100 Gauss up to 1 kilo-Gauss. Mind you, that's just for young exoplanets – the magnetic fields of exoplanets also evolve over time, such that their magnetic field strength may decrease by a factor of ten over 10 billion years. In any case, Reiners and Christensen estimate that radio light from known exoplanets within 65 light years will emit at wavelengths that can make it through Earth's ionosphere – so with the right ground-based equipment (i.e. a completed LOFAR or a SKA) we should be able to start spotting brown dwarfs and exoplanets aplenty.>>

[Ann]

Astronomy Without A Telescope – Brown Dwarfs Are Magnetic Too
Written by Steve Nerlich July 17th, 2010

Brown dwarf TWA 5B compared with the Sun and Jupiter. Although brown dwarfs are similar in size to Jupiter, they are much more dense and massive - between 13 and 80 Jupiter masses. Credit: chandra.harvard.edu

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<<I feel a certain empathy for brown dwarfs. The first confirmed finding of one was only fifteen years ago and they remain frequently overlooked in most significant astronomical surveys. I mean OK, they can only (stifles laughter) burn deuterium but that's something, isn't it?

Poor little brown dwarf, oh my!

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Ann

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Edward Nigma

<<A brownie/brounie or urisk (Lowland Scots) or brùnaidh, ùruisg, or gruagach (Scottish Gaelic) is a legendary creature popular in folklore around Scotland and England (especially the north, though more commonly hobs have this role). It is the Scottish and Northern English counterpart of the Scandinavian tomte, the Slavic domovoi and the German Heinzelmännchen.

In folklore, a brownie is a type of hob, similar to a hobgoblin. Brownies are said to inhabit houses and aid in tasks around the house. However, they do not like to be seen and will only work at night, traditionally in exchange for small gifts or food. Among food, they especially enjoy porridge and honey. They usually abandon the house if their gifts are called payments, or if the owners of the house misuse them. Brownies make their homes in an unused part of the house.

Folklorist John Gregorson Campbell distinguishes between the English brownie, which lived in houses, and the Scottish ùruisg or urisk, which lived outside in streams and waterfalls and was less likely to offer domestic help. The ùruisg enjoyed solitude at certain seasons of the year. Around the end of the harvest, he became more sociable, and hovered around farmyards, stables and cattle-houses. He particularly enjoyed dairy products, and tended to intrude on milkmaids, who made regular libations of milk or cream to charm him off, or to gain his favour. He was usually seen only by those who possessed second sight, though there were instances when he made himself visible to ordinary people as well. He is said to have been jolly and personable, with flowing yellow hair, wearing a broad blue bonnet and carrying a long walking staff.

Every manor house had its ùruisg, and in the kitchen, close by the fire was a seat, which was left unoccupied for him. One house on the banks of the River Tay was even until the beginning of the twentieth century believed to have been haunted by such a sprite, and one room in the house was for centuries called "Seòmar Bhrùnaidh" (Brownie’s room).

In 1703, John Brand wrote in his description of Shetland (which he called "Zetland") that:

“Not above forty or fifty years ago, every family had a brownie, or evil spirit, so called, which served them, to which they gave a sacrifice for his service; as when they churned their milk, they took a part thereof, and sprinkled every corner of the house with it, for Brownie’s use; likewise, when they brewed, they had a stone which they called ‘Brownie’s stane’, wherein there was a little hole into which they poured some wort for a sacrifice to Brownie. They also had some stacks of corn, which they called Brownie’s Stacks, which, though they were not bound with straw ropes, or in any way fenced as other stacks used to be, yet the greatest storm of wind was not able to blow away straw off them.”

Brownies seldom spoke with humans, but they held frequent and affectionate conversations with one another. They had general assemblies as well, usually held on a remote, rocky shore. In a certain district of the Scottish Highlands, "Peallaidh an Spùit" (Peallaidh of the Spout), "Stochdail a’ Chùirt", and "Brùnaidh an Easain" (Brownie of the little waterfall) were names of note at those congresses. Every stream in Breadalbane had an ùruisg once according to Watson the Scottish place name expert, and their king was Peallaidh. (Peallaidh's name is preserved in "Obair Pheallaidh", known in English as "Aberfeldy".) It may be the case, that ùruisg was conflated with some water sprite, or that ùruisg were originally water sprites conflated with brownies.

In the science-fiction novel, The Mote in God's Eye by Larry Niven and Jerry Pournelle, the Watchmaker sub-species of the Moties are nicknamed "brownies" by the crew of the INSS MacArthur...Arthur Stillwell, founder of Port Arthur, Texas, claimed that brownies instructed him to establish the city at its present location.>>

[Ann]

Viktor Rydberg, Tomten (The tomte) from 1881:

Deep in the grip of the midwinter cold
Stars send a sparkling light.
All are asleep on this lonely farm,
Deep in the winter night.
The pale white moon is wanderer,
And snow lies white on pine and fir.
Snow glows on rooftop shake.
The tomte alone is awake.

Gray, he stands by the low barn door,
Gray by the drifted snow,
Gazing, as many winters he’s gazed,
Up at the moon’s chill glow,
Then at the forest where fir and pine
Circle the farm in a dusky line,
Mulling relentlessly
A riddle that has no key.

Rubs his hand through his beard and hair,
Shakes his head and his cap.
“No, that question is much too deep,
I cannot fathom that.”
Then making his mind up in a hurry,
He shrugs away the annoying worry;
Turns at his own command,
Turns to the task at hand.

Goes to the storehouse and toolshop doors,
Checking the locks of all,
While the cows dream on in the cold moon’s light,
Summer dreams in each stall.
And free of harness and whip and rein,
Even Old Palle dreams again.
The manger he’s drowsing over
Brims with fragrant clover.

The tomte glances at sheep and lambs
Cuddled in quiet rest.
The chickens are next, where the rooster roosts
High above straw filled nests.
Burrowed in straw, hearty and hale,
Karo wakens and wags his tail
As if to say, “Old friend, “Partners we are to the end.”

At last the tomte tiptoes in
To see how the housefolk fare.
He knows full well the strong esteem
They feel for his faithful care.
He tiptoes up to the children’s beds,
Silently peers at their tousled heads.
There is no mistaking his pleasure:
These are his greatest treasure.

Long generations has he watched
Father to son to son
Sleeping as babes. But where, he asks,
From where, from where have they come?
Families came, families went,
Blossomed and aged, a lifetime spent,
Then-Where? That riddle again
Unanswered in his brain!

Slowly he turns to the barnyard loft,
His fortress, his home and rest,
High in the mow, in the fragrant hay
Near to the swallow’s nest.
The nest is empty, but in the spring
When birds mid leaves and blossoms sing,
She will be back with her mate.

Then will she talk of the journey tell.
Twittering to all who hear it,
But nary a hint for the question old
That stirs in the tomte’s spirit.
Now through cracks in the haymow wall
The moon lights tomte and hay and all,
Lights his beard through the chinks,
The tomte ponders and thinks.

Still is the forest and all the land,
Locked in this wintry year.
Only the distant waterfall
Whispers and sighs in his ear.
The tomte listens and, half in dream,
Thinks that he hears Time’s endless stream,
And wonders, where is it bound?
Where is its source to be found?

Deep in the grip of the midwinter cold,
Stars send a sparkling light.
All are asleep on this lonely farm,
Late in this winter night.
The pale white moon is a wanderer,
Snow lies white on pine and fir;
Snow glows on rooftop shake.
The tomte alone is awake.

Midvinternattens köld är hård,
stjärnorna gnistra och glimma.
Alla sova i enslig gård
djupt under midnattstimma.
Månen vandrar sin tysta ban,
snön lyser vit på fur och gran,
snön lyser vit på taken.
Endast tomten är vaken.

Står där så grå vid ladgårdsdörr,
grå mot den vita driva,
tittar, som många vintrar förr,
upp emot månens skiva,
tittar mot skogen, där gran och fur
drar kring gården sin dunkla mur,
grubblar, fast ej det lär båta,
över en underlig gåta.

För sin hand genom skägg och hår,
skakar huvud och hätta ---
»nej, den gåtan är alltför svår,
nej, jag gissar ej detta» ---
slår, som han plägar, inom kort
slika spörjande tankar bort,
går att ordna och pyssla,
går att sköta sin syssla.

Går till visthus och redskapshus,
känner på alla låsen ---
korna drömma vid månens ljus
sommardrömmar i båsen;
glömsk av sele och pisk och töm
Pålle i stallet har ock en dröm:
krubban han lutar över
fylls av doftande klöver; ---

Går till stängslet för lamm och får,
ser, hur de sova där inne;
går till hönsen, där tuppen står
stolt på sin högsta pinne;
Karo i hundbots halm mår gott,
vaknar och viftar svansen smått,
Karo sin tomte känner,
de äro gode vänner.

Tomten smyger sig sist att se
husbondfolket det kära,
länge och väl han märkt, att de
hålla hans flit i ära;
barnens kammar han sen på tå
nalkas att se de söta små,
ingen må det förtycka:
det är hans största lycka.

Så har han sett dem, far och son,
ren genom många leder
slumra som barn; men varifrån
kommo de väl hit neder?
Släkte följde på släkte snart,
blomstrade, åldrades, gick --- men vart?
Gåtan, som icke låter
gissa sig, kom så åter!

Tomten vandrar till ladans loft:
där har han bo och fäste
högt på skullen i höets doft,
nära vid svalans näste;
nu är väl svalans boning tom,
men till våren med blad och blom
kommer hon nog tillbaka,
följd av sin näpna maka.

Då har hon alltid att kvittra om
månget ett färdeminne,
intet likväl om gåtan, som
rör sig i tomtens sinne.
Genom en springa i ladans vägg
lyser månen på gubbens skägg,
strimman på skägget blänker,
tomten grubblar och tänker.

Tyst är skogen och nejden all,
livet där ute är fruset,
blott från fjärran av forsens fall
höres helt sakta bruset.
Tomten lyssnar och, halvt i dröm,
tycker sig höra tidens ström,
undrar, varthän den skall fara,
undrar, var källan må vara.

Midvinternattens köld är hård,
stjärnorna gnistra och glimma.
Alla sova i enslig gård
gott intill morgontimma.
Månen sänker sin tysta ban,
snön lyser vit på fur och gran,
snön lyser vit på taken.
Endast tomten är vaken.

Click to play embedded YouTube video.

Ann

[neufer]

Viktor Rydberg, Tomten (The tomte) from 1881:

Click to play embedded YouTube video.

• Ingmar Bergman the early years?

(A young Max von Sydow gave a excellent performance as Tomten but the star of the show was definitely the cat.)

<<Rydberg is a lunar impact crater that is located on the far side of the Moon, just past the southwestern limb. It lies due south of the Mare Orientale, in the outer skirt of ejecta that surrounds the Orientale impact feature. Just to the southeast is the crater Guthnick. This is a little-eroded crater formation with a relatively sharp edge. The inner walls do not have much terracing, although slumped piles of talus lie along the base. At the mid-point of the interior is a central ridge, with a low spur that runs halfway toward the southern inner wall.>>

<<Johannes Robert Rydberg, (‘Janne’ to his friends), (November 8, 1854 – December 28, 1919), was a Swedish physicist mainly known for devising the Rydberg formula, in 1888, which is used to predict the wavelengths of photons (of light and other electromagnetic radiation) emitted by changes in the energy level of an electron in an hydrogen atom.





The physical constant known as the Rydberg constant is named after him, as is the Rydberg unit. Excited atoms with very high values of the principal quantum number, represented by n in the Rydberg formula, are called Rydberg atoms. Rydberg's faith that spectral studies could assist in a theoretical understanding of the atom and its chemical properties was justified in 1913 by the work of Niels Bohr (see hydrogen spectrum). An important spectroscopic constant based on a hypothetical atom of infinite mass is called the Rydberg (R) in his honour.

He was active at Lund University, Sweden, for all of his working life.

The crater Rydberg on the Moon and asteroid 10506 Rydberg are named in his honour.

There is a pub held in Rydberg's honor every Wednesday at the faculty of physics at Lund University.>>

[Ann]

• Ingmar Bergman the early years?

(A young Max von Sydow gave a excellent performance as Tomten but the star of the show was definitely the cat.)

Young Max von Sydow as a gray dwarf,1881.

Old Max von Sydow as a white knight, 1957.

(And as you can see I can't do that float and image 3 thing, so this was the best I could do.)

Ann