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The first stars appeared about 200 million years after the Big Bang. It formed in the denser regions of gas inside the protogalaxies. The protogalaxies in turn would be most likely located at the nodes of the filaments in the large structure. Since there was little metals present in the early universe, the production of nuclear energy is less efficient, the first stars were able to assemble more mass and still maintained a stable structure. The limit should be no more than 1000 solar mass. Figure 08-02a compares the calculated characteristics of the first stars with those for the Sun. The most iron-deficient star HE0107-5240 was discovered in late 2002. This primitive star has a |
Figure 08-02a First Stars |
Figure 08-02b First Stars 2 [view large image] |
measured abundance of iron less than 1/200000 that of the Sun. It seems to have formed shortly after the Big Bang. Figure 08-02b offers further explanation (in 2014) for the large size of the first stars. |
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These oldest stars belong to the population III category opposing to the older population II objects in galactic halo and the young population I objects in galactic disk. It is not clear if the small trace of iron was generated within HE0107-5240 itself, or contaminated by materials from stars of later/earlier generations. Figure 08-02c compares the abundance of elements between the HE0107-5240 data (red circles) and those produced by the 25 Msun population III supernova model. Meanwhile, measurements of quasar absorption spectrum indicate that there is neutral hydrogen (not re-ionized) billion years after the Big Bang in contradiction to the 200 million years derived from the observation of first star. Perhaps reionization was a slow process, which only gradually encompassed the whole universe. Further study is required to resolve the discrepancy. |
Figure 08-02c HE0107-5240 |
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In the June 2011 issue of the Astronomy magazine, there is an article to describe a more detailed development of the first stars. Figure 08-02d is a pictorial summary of the birth and death of the first stars as presented in the article (with slight modification). Although the first stars have yet to be found in the future (may be by the James Webb Space Telescope - the successor to the |
Figure 08-02d Evolution of First Stars [view large image] |
HST), the first galaxy have already been detected with an estimated age of about 480 million years after the Big Bang. |
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Figure 08-02e presents the images of a portion of sky in the Hubble Deep Field North at two different infrared wavelengths, 3.6 ![]() ![]() |
Figure 08-02e Signatures of First Stars as Infrared Blobs |
distinguished from other sources of noise and emission. In short, these puffy blobs are just the signatures of the early stars (not the real thing). See "Angular-Size Redshift Relation" for an explanation of the large angular size of the blobs. |
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cm radio wave. The process started with small holes around the stars, the holes enlarged and emerged and finally all the hydrogen atoms are re-ionized leaving no trace of 21 cm emission. An observational plan is to detect the turn-off time, which would be closely related to the birth of the first stars (Figure 08-02f). Currently, the Precision Array to Probe the Epoch of Re-ionization (PAPER) is dedicated to such search of first star via 21 cm radio emission. |
Figure 08-02f First Star Detection by 21 cm Radio Wave [view large image] |
Figure 08-02g Early Universe, 21 cm Radio wave [view large image] |
Figure 08-02g depicts another view of the 21 cm line in the Early Universe. |
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Figure 08-02h 21 cm Absorption |
Figure 08-02i Process of Re-ionization [view large image] |
(lifetime of first stars ~ 3 Myr, see Figure 08-02a). The surface temperature of these stars were more than 105 K - enough to ionize the hydrogen atoms having a ground |
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configurations. The thick black line of H2 is the model fit for the highest signal-to-noise ratio (= 52). The dash-dotted line of P8 is an extension of H2 with a different foreground model. All the previously quoted cosmic data are derived from the analysis of such measurements. |
Figure 08-02j EDGES Antenna [view large image] |
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Figure 08-02k Cosmic Timeline (Graphic) [view large image] |
(Schematic) |
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Figure 08-02l |
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otherwise it would collapse under its own weight. Thus generally, star would born in a cool and dense region. In Eq.(2), kB = 1.38x10-16 erg/K is the Boltzmann constant, G = 6.6742x10-8 cm3/sec2-gm is the Gravitational Constant, m the molecular weight ~ 2x10-24 gm, TC the temperature in K, and ![]() |
Figure 08-02m GMC in Dark Age |
Figure 08-02m shows the general characteristics of GMC and its role in the Dark Age epoch. |
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Figure 08-02n 21-cm Line Transition [view large image] |
See a slightly different version with no mathematical formulas : "What Was It Like When The First Stars Began Illuminating The Universe?". |
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Figure 08-02o Evolutionary Time of Stars [view large image] |
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The poor metal characteristics indicates that the globular clusters are really created very early close to the Dark Age epoch. The occasional exceptions are just later addition when they acquire more recent material. |
Figure 08-02p M5 Globular Cluster HR Diagram [view large image] |
In Figure 08-02p for the HR diagram of M5 globular cluster, star in Red Giant Branch (RGB) lives about 1 Gyr, and would spend another 100 Myr in Asymptotic Giant Branch (AGB) + Horizontal Branch (HB). TO stands for Turn-Off (from the Main Sequence). |
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Figure 08-02q High Z Galaxy from GLASS [view large image] |
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These three objects are cataloged in the Near Infrared Spectrograph (NIRSpec) with (red-shifted) wavelength range from 0.6 to 5 microns (= 10-4 cm) or red-shifted by ~ z ![]() ![]() |
Figure 08-02r Green Pea Galaxy [view large image] |
See original paper "Finding Peas in the Early Universe with JWST" published in January 1, 2023. |
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The cosmic GPs look red because of the high red shift. See Figure 08-02s for the green light in auroras, which is primarily due to the emission of atomic oxygen in Earth's atmosphere. When charged particles from the Sun (solar wind) collide with oxygen atoms and molecules in the Earth's upper atmosphere. |
Figure 08-02s Green Color in Auroras [view large image] |
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Figure 08-02t GP Characteristics [view large image] |
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This was when the galactic bulge of the present day elliptical galaxies assembled from stars + dust and Gas. It involved a series of violent mergers. The collisions of gas and dust triggered high star formation rate (SFR), which is one of the GP's characteristics. The size and mass of the GPs are also within ranges of the galactic bulge. It seems that the GPs are located in an environment with a lot of star clouds but no galaxies and hence getting stuck at the phase existing in 0.8 billion years after BB (see Figure 08-02u). |
Figure 08-02u Elliptical Galaxy Evolution [view large image] |
When the overall angular momentum was small, and star formation proceeded rapidly (thereby mopping up most of the gas early on in the evolutionary process), the end result would be an elliptical galaxy dominated by older stars and containing little, if any, gas (see Figure 08-02u). |
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As for the "local" GPs, they could be close to us but in old age. For example, the Magellanic clouds (a pair of irregular galaxies, see Figure 08-02v) are located in Milky Way's back yard about 60 kpc away, but they were born around 500 million years after Big Bang (with age ~ 13.2 billion years). |
Figure 08-02v |
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Figure 08-02w Early Galaxies |
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The latest (May 17, 2023) addition to JWST's "High Z Treasure Trove" is JD1 with z ~ 9.79, M ~ 107 MSun and size D ~ 0.15 kpc (see "The nature of an ultra-faint galaxy in the cosmic dark ages seen with JWST"). Comparing to the Green Pea (GP) galaxies, its mass and size is at the low end of the group while the red-shift is somewhat higher; it implies that JD1 is a GP at its early formation stage. It has been placed in "JWST's "Glass" dataset" earlier with red-shift estimated to be around z ~ 11. |
Figure 08-02x Early Galaxy JD1 [view large image] |
See Figure 08-21m about the Giant Molecular Cloud (GMC) in an even earlier time with mass M ~ [0.001-0.1]x107 MSun, D ~ [0.005-0.1] kpc emerging from the Dark Age. |
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Figure 08-02y Production of Heavy Elements [view large image]Figure 08-02z Star Dust | for the latest JWST star dust detection. |
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