Starship Asterisk*

Beyond wrote:Nearly as old as the universe? And it's right in our own back yard?? Coincidence???

Beyond wrote:Nearly as old as the universe? And it's right in our own back yard?? Coincidence???

• Astrophysical Journal Letters 765(1) L12 (2013 Mar 01) DOI: 10.1088/2041-8205/765/1/L12
  arXiv.org > astro-ph > arXiv:1302.3180 > 13 Feb 2013

bystander wrote:
HD 140283: A Star in the Solar Neighborhood that Formed Shortly After the Big Bang - Howard E. Bond et al

• Astrophysical Journal Letters 765(1) L12 (2013 Mar 01) DOI: 10.1088/2041-8205/765/1/L12
  arXiv.org > astro-ph > arXiv:1302.3180 > 13 Feb 2013

The Fine Guidance Sensors on the Hubble Space Telescope can yield parallaxes better than 0.2 mas

MargaritaMc wrote:
Am I correct in thinking that that is, 1/3600÷1/1000 of a degree of arc

1 arcsecond = 1/3600 degree. 1 milli-arc second or mas, which stands for 1/1000 arc second.

bystander wrote:

MargaritaMc wrote:
Am I correct in thinking that that is, 1/3600÷1/1000 of a degree of arc :?: :!: :shock:

1 arcsecond = 1/3600 degree. 1 milli-arc second or mas, which stands for 1/1000 arc second.

You understood correctly, but your mathematical representation is off. It should be:

1/3600 * 1/1000 of a degree of arc

bystander wrote:

MargaritaMc wrote:
Am I correct in thinking that that is, 1/3600÷1/1000 of a degree of arc

1 arcsecond = 1/3600 degree. 1 milli-arc second or mas, which stands for 1/1000 arc second.

You understood correctly, but your mathematical representation is off. It should be:

1/3600 * 1/1000 of a degree of arc

Ann wrote:
A nearby star, HD 140283, is both older, brighter and bluer than the Sun. And not only is it older, it is as old as the universe!

HD 140283 is a subgiant of spectral class F3, hotter than the Sun, with a Johnson B-V index of +0.484 ± 0.010, bluer than the Sun. The apparent luminosity of HD 140283 is +7.20, which, coupled with its well-measured distance of 190 light-years, means that its absolute V luminosity is 3.72 ± 0.30 that of the Sun. Amazingly, HD 140283 is incredibly metal-poor. In other words, it appears to be made of the kind of the almost perfect mixture of hydrogen and helium that came directly from the Big Bang, with just the tiniest seasoning of other elements in the brew.

To me it is absolutely amazing that a star that has been around for as long as the universe can be bluish in color, or at least bluer than the Sun. Normally stars get redder as they age. Really the oldest star in the universe ought to have been a tiny red dwarf, don't you think so?

http://www.skyandtelescope.com/community/skyblog/newsblog/Stellar-Senior-Citizen-191887131.html wrote:
The search for the oldest stars in the Universe has just turned up a new candidate: HD 140283. This 7th-magnitude sub-giant has intrigued astronomers for decades. It was one of the first stars found with an extremely low concentration of heavy elements in its outer atmosphere, compared with the Sun. And this composition makes the star — which has roughly the same [surface] temperature as the Sun — look like a star twice as hot as it is.

http://www.universetoday.com/100147/ wrote:

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HD 140283 is estimated to be 14.46+-0.80 billion years old. On the y-axis is the star’s pseudo-luminosity, on the x-axis its temperature. Computed evolutionary tracks (solid lines ranging from 13.4 to 14.4 billion years) were applied to infer the age (image credit: Bond et al. 2013 by D. Majaess, arXiv).

• Log (Sun's surface temperature: ~5,800 K) ~3.763

http://en.wikipedia.org/wiki/The_Fairy_with_Turquoise_Hair wrote:

Click to play embedded YouTube video.

<<The Fairy With Turquoise Hair (Italian: La Fata dai Capelli Turchini) is a fictional character in Carlo Collodi's book The Adventures of Pinocchio. She repeatedly appears at critical moments in Pinocchio's wanderings to admonish the little wooden puppet to avoid bad or risky behavior. Although the naïvely willful marionette initially resists her good advice, he later comes to follow her instruction. She in turn protects him, and later enables his assumption of human form.

In Walt Disney's Pinocchio, the Fairy (voiced by Evelyn Venable) is referred to as The Blue Fairy, and is one of the four leading protagonists in the film. It is she who brings Pinocchio to life, and she is much less involved in his upbringing than she is in the book, having appointed Jiminy Cricket as Pinocchio's conscience.

In Giuliano Cencis' 1972 adaptation Un burattino di nome Pinocchio, the Fairy (voiced by Vittoria Febbi) is portrayed much more accurately to the book than she is in the Disney adaptation. She has no role in creating Pinocchio, though she does offer him guidance and support. Though she is accurately portrayed as sporting blue hair, she does not physically age as she does in the book.

In Steven Spielberg's 2001 movie A.I.: Artificial Intelligence (2001), the Blue Fairy (voiced by Meryl Streep) appears as a plot MacGuffin. The main character, David, a robotic child played by Haley Joel Osment, believes that the Blue Fairy has the power to turn him into a real boy. It also appears in the form of the Coney Island statue of the Blue Fairy, which David mistakes for a real blue fairy.>>

MargaritaMc wrote:...because I just do not want to continue to be so innumerate.

Beyond wrote:

MargaritaMc wrote:...because I just do not want to continue to be so innumerate.

What's wrong with being innumerate I'm that way all the time, plus rather illiterate when it comes to the inglish language. Looks like I'm well into the "rates". And i have no idea of what the * bystander used, means.

Art wrote:
Nevertheless, HD 140283 is a relatively dim but massive sub-giant star which, due to its low metallicity, "looks like a star twice as hot (i.e., much bluer) than it is."

Harvey B. Richer, Jay Anderson, James Brewer, Saul Davis, Gregory G. Fahlman,
Brad M.S. Hansen, Jarrod Hurley, Jasonjot S. Kalirai, Ivan R. King, David Reitzel,
R. Michael Rich, Michael M. Shara, Peter B. Stetson wrote:
In recent years, it has been appreciated that the white dwarf cooling sequence
is expected to turn back to the blue at faint magnitudes (5-9). As white dwarfs with
hydrogen-rich atmospheres cool below temperatures of 4000 K, they exhibit the
collision-induced absorption (CIA) of molecular hydrogen (10). CIA is strongest at
near-infrared wavelengths, which suppresses the flux near 1 micron (11) and causes the
optical colors to become bluer as the star cools, rather than redder as might be expected
from a blackbody.

Ann wrote:

Art wrote:
Nevertheless, HD 140283 is a relatively dim but massive sub-giant star which, due to its low metallicity, "looks like a star twice as hot (i.e., much bluer) than it is."

I think I beg to differ, Art. Isn't it true that the star is as blue as it is, but it is not as hot as it looks?

Ann wrote:
A metal-rich star will have very many spectral lines, particularly in the short-wave part of the visible spectrum. Its light will be "reddened" by the spectral lines. But a very metal-poor star will mostly lack spectral lines, so that its light will be "unreddened", and way it will look bluer than the metal-rich star.

Thanks for the diagram. Does that "evolutionary curve" tell us that HD 140283 isn't a horizontal branch star after all?

http://en.wikipedia.org/wiki/Sun#Photosphere wrote:

[b][color=#FF0000][size=115]The effective temperature of the Sun (5777 K) is the temperature a black body of the same size must have to yield the same total emissive power. The sun [u]looks like a star that is colder (i.e., redder)[/u] than one would assume simply from its effective temperature.[/size][/color][/b]

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<<The visible surface of the Sun, the photosphere, is the layer below which the Sun becomes opaque to visible light. Above the photosphere visible sunlight is free to propagate into space, and its energy escapes the Sun entirely. The change in opacity is due to the decreasing amount of H⁻ ions, which absorb visible light easily. Conversely, the visible light we see is produced as electrons react with hydrogen atoms to produce H⁻ ions. The photosphere is tens to hundreds of kilometers thick, being slightly less opaque than air on Earth. Because the upper part of the photosphere is cooler than the lower part, an image of the Sun appears brighter in the center than on the edge or limb of the solar disk, in a phenomenon known as limb darkening. Sunlight has approximately a black-body spectrum that indicates its temperature is about 6,000 K, interspersed with atomic absorption lines from the tenuous layers above the photosphere. The photosphere has a particle density of ~10²³ m⁻³. (This is about 0.37% of the particle number per volume of Earth's atmosphere at sea level.) The photosphere is not fully ionized—the extent of ionization is about 3%, leaving almost all of the hydrogen in atomic form.>>

Ann wrote:
Does that "evolutionary curve" tell us that HD 140283 isn't a horizontal branch star after all?

• That's how I understand it.

Ann wrote:

http://www.universetoday.com/100147/ wrote:

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HD 140283 is estimated to be 14.46+-0.80 billion years old. On the y-axis is the star’s pseudo-luminosity, on the x-axis its temperature. Computed evolutionary tracks (solid lines ranging from 13.4 to 14.4 billion years) were applied to infer the age (image credit: Bond et al. 2013 by D. Majaess, arXiv).

Log (Sun's surface temperature: ~5,800 K) ~3.763

Does that "evolutionary curve" tell us that HD 140283 isn't a horizontal branch star after all?

http://en.wikipedia.org/wiki/Horizontal_branch wrote:

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[b][color=#0000FF]Color-magnitude diagram for the globular cluster M3. The horizontal branch stars are those that lie at or slightly above V = 16, to the left of B-V = 0.7[/color][/b]

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<<The horizontal branch (HB) is a stage of stellar evolution that immediately follows the red giant branch in stars whose masses are similar to the Sun's. The helium core flash that occurs to stars at the top of the red giant branch causes substantial changes in stellar structure, resulting in an overall reduction in luminosity, some contraction of the stellar envelope, and surfaces reaching higher temperatures. Horizontal branch stars are powered by helium fusion in the core (via the triple-alpha reaction) and by hydrogen fusion in a shell surrounding the core.

Horizontal branches were discovered with the first deep photographic photometric studies of globular clusters and were notable for being absent from all open clusters that had been studied up to that time. The horizontal branch is so named because in low-metallicity samples like globular clusters, HB stars lie along a roughly horizontal line in a Hertzsprung–Russell diagram (CMD).

In main sequence stars with masses up to 2.3 times the mass of the Sun, the thermonuclear fusion of hydrogen (bearing the name of p-p chain) at the core will steadily build up a concentration of helium at a rate primarily determined by the mass of the star. In due course, the helium-enriched core becomes unable to sustain nuclear fusion of hydrogen and the fusion process migrates outward to a shell. The core becomes a region of degenerate matter that does not contribute to the generation of energy. It continues to grow and increase in temperature as the hydrogen fusion along the shell contributes more helium.

If the star has more than about 0.5 solar masses , the core eventually reaches the temperature necessary for the fusion of helium into carbon through the triple-alpha process. The initiation of helium fusion begins across the core region, which will cause an immediate temperature rise and a rapid increase in the rate of fusion. Within a few seconds the core becomes non-degenerate and quickly expands, producing an event called helium flash. The output of this event is absorbed by the layers of plasma above, so the effects are not seen from the exterior of the star. The star now changes to a new equilibrium state, and its evolutionary path switches from the red giant branch (RGB) onto the horizontal branch of the Hertzsprung–Russell diagram. This term means that the luminosity of the star will stay relatively stable while the effective temperature increases, effectively migrating horizontally across the H-R diagram.

Stars with an initial mass close to the sun dip down to the red end of the horizontal branch when core helium burning starts, but show only a small increase in temperature before core helium is exhausted. More massive stars spend an extended time on the horizontal branch and show a larger increase in temperature as they burn helium in the core. The shape of the horizontal branch is due both to the movement of individual stars bluewards as they age, and to the temperature of stars with different masses when they reach the horizontal branch. There are further variations, both in luminosity and temperature, due to metallicity and helium content.

Although the horizontal branch is named because it consists largely of stars with approximately the same luminosity and a range of temperature, lying in a horizontal bar on colour-magnitude diagrams, the branch is far from horizontal at the blue end. The horizontal branch ends in a "blue tail" with hotter stars having lower luminosity, occasionally with a "blue hook" of extremely hot stars. The hottest horizontal branch stars, referred to as extreme horizontal branch, have temperatures of 20,000-30,000K. This is far beyond what would be expected for a normal core helium burning star. Theories to explain these stars include binary interactions, and "late thermal pulses", where a thermal pulse that AGB stars experience regularly, occurs after fusion has ceased and the stars has entered the superwind phase. These stars are "born again" with unusual properties. Despite the bizarre-sounding process, this is expected to occur for 10% or more of post-AGB stars, although it is thought that only particularly late thermal pulses create extreme horizontal branch stars, after the planetary nebular phase and when the central star is already cooling towards a white dwarf.

Globular cluster CMDs generally show horizontal branches that have a prominent gap in the HB. This gap in the CMD incorrectly suggests that the cluster has no stars in this region of its CMD. The gap occurs at the instability strip, so many stars in this region pulsate. These pulsating horizontal branch stars are known as RR Lyrae variable stars and they are obviously variable in brightness with periods of up to 1.2 days . It requires an extended observing program to establish the star's true (that is, averaged over a full period) apparent magnitude and color. Such a program is usually beyond the scope of an investigation of a cluster's color-magnitude diagram. Because of this, while the variable stars are noted in tables of a cluster's stellar content from such an investigation, these variable stars are not included in the graphic presentation of the cluster CMD because data adequate to plot them correctly are unavailable. This omission often results in the RR Lyrae gap seen in many published globular cluster CMDs.>>

[url=http://hubblesite.org/newscenter/archive/releases/2013/08/image/a/][b][i]HD 140283: Oldest Star in Solar Neighborhood[/i][/b][/url] [b][i]Credit: Digitized Sky Survey (DSS), STScI/AURA, Palomar/Caltech, and UKSTU/AAO[/i][/b]

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[url=http://hubblesite.org/newscenter/archive/releases/2013/08/image/d/][b][i]Backyard View of Sky Around HD 140283[/i][/b][/url] [b][i]Credit: A. Fujii and Z. Levay (STScI)[/i][/b]

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A team of astronomers using NASA's Hubble Space Telescope has taken an important step closer to finding the birth certificate of a star that's been around for a very long time.

"We have found that this is the oldest known star with a well-determined age," said Howard Bond of Pennsylvania State University in University Park, Pa., and the Space Telescope Science Institute in Baltimore, Md.

The star could be as old as 14.5 billion years (plus or minus 0.8 billion years), which at first glance would make it older than the universe's calculated age of about 13.8 billion years, an obvious dilemma.

But earlier estimates from observations dating back to 2000 placed the star as old as 16 billion years. And this age range presented a potential dilemma for cosmologists. "Maybe the cosmology is wrong, stellar physics is wrong, or the star's distance is wrong," Bond said. "So we set out to refine the distance."

The new Hubble age estimates reduce the range of measurement uncertainty, so that the star's age overlaps with the universe's age — as independently determined by the rate of expansion of space, an analysis of the microwave background from the big bang, and measurements of radioactive decay.

This "Methuselah star," cataloged as HD 140283, has been known about for more than a century because of its fast motion across the sky. The high rate of motion is evidence that the star is simply a visitor to our stellar neighborhood. Its orbit carries it down through the plane of our galaxy from the ancient halo of stars that encircle the Milky Way, and will eventually slingshot back to the galactic halo.

This conclusion was bolstered by the 1950s astronomers who were able to measure a deficiency of heavier elements in the star as compared to other stars in our galactic neighborhood. The halo stars are among the first inhabitants of our galaxy and collectively represent an older population from the stars, like our Sun, that formed later in the disk. This means that the star formed at a very early time before the universe was largely "polluted" with heavier elements forged inside stars through nucleosynthesis. (The Methuselah star has an anemic 1/250th as much of the heavy element content of our Sun and other stars in our solar neighborhood.)

The star, which is at the very first stages of expanding into a red giant, can be seen with binoculars as a 7th-magnitude object in the constellation Libra.

Hubble's observational prowess was used to refine the distance to the star, which comes out to be 190.1 light-years. Bond and his team performed this measurement by using trigonometric parallax, where an apparent shift in the position of a star is caused by a change in the observer's position. The results are published in the February 13 issue of the Astrophysical Journal Letters.

The parallax of nearby stars can be measured by observing them from opposite points in Earth's orbit around the Sun. The star's true distance from Earth can then be precisely calculated through straightforward triangulation.

Once the true distance is known, an exact value for the star's intrinsic brightness can be calculated. Knowing a star's intrinsic brightness is a fundamental prerequisite to estimating its age.

Before the Hubble observation, the European Space Agency's Hipparcos satellite made a precise measurement of the star's parallax, but with an age measurement uncertainty of 2 billion years. One of Hubble's three Fine Guidance Sensors measured the position of the Methuselah star. It turns out that the star's parallax came out to be virtually identical to the Hipparcos measurements. But Hubble's precision is five times better than that of Hipparcos. Bond's team managed to shrink the uncertainty so that the age estimate was five times more precise.

With a better handle on the star's brightness Bond's team refined the star's age by applying contemporary theories about the star's burn rate, chemical abundances, and internal structure. New ideas are that leftover helium diffuses deeper into the core and so the star has less hydrogen to burn via nuclear fusion. This means it uses fuel faster and that correspondingly lowers the age.

Also, the star has a higher than predicted oxygen-to-iron ratio, and this too lowers the age. Bond thinks that further oxygen measurement could reduce the star's age even more, because the star would have formed at a slightly later time when the universe was richer in oxygen abundance. Lowering the upper age limit would make the star unequivocally younger than the universe.

"Put all of those ingredients together and you get an age of 14.5 billion years, with a residual uncertainty that makes the star's age compatible with the age of the universe," said Bond. "This is the best star in the sky to do precision age calculations by virtue of its closeness and brightness."

This Methuselah star has seen many changes over its long life. It was likely born in a primeval dwarf galaxy. The dwarf galaxy eventually was gravitationally shredded and sucked in by the emerging Milky Way over 12 billion years ago.

The star retains its elongated orbit from that cannibalism event. Therefore, it's just passing through the solar neighborhood at a rocket-like speed of 800,000 miles per hour. It takes just 1,500 years to traverse a piece of sky with the angular width of the full Moon. The star's proper motion angular rate is so fast (0.13 milliarcseconds an hour) that Hubble could actually photograph its movement in a few hours.

saturno2 wrote:Ann
This topic is super interesting.
Well. I didn´t know that the longevity principle could be aplied to the stars,
too.
I think that HD 140283 is a " longevity star"
It has powerful blue glow as a young star, but his age is oldest than the Universe itself, 14.5 billion of years !!
And as the older people of Vilcabamba Village,walk very fast, HD 140283
" longevity star" travel around the neighborhood of Milky Way at
high speed.
But, what is your secret to longevity?
Maybe it uses fuel very quickly, wich develops much energy, without
wearing much the machine, sorry I meant the star:

Arcturus has a velocity relative to the Sun that is higher than other bright stars. Compared with the set of surrounding stars, which orbit the Galaxy on more or less circular orbits, it falls behind by about 100 kilometers per second (as do several others of the "Arcturus Group").

The lagging movement has long suggested that the star comes from an older population of the Galaxy.

Consistently, it is somewhat deficient in metals, having only about 20 percent as much iron relative to hydrogen as found in the Sun.

As a giant, weighing in at around 1.5 times the mass of the Sun, it has ceased the fusion of hydrogen in its core.