# Tag Info

14

No. There is no consensus. The discrepancy between the predicted big bang nucleosynthetic abundance of Lithium 7 and the measured value can be summarised as follows. If we take what we know about the the baryonic mass density of the universe and the Hubble constant, we get a self-consistent picture between the cosmic microwave background, observations of ...

12

Doing a bit of reading up on this, I might have an answer, though credit where credit is due, the answer isn't really mine: https://www.reddit.com/r/askscience/comments/3wsy99/why_is_neon_so_rare_on_earth/ When the planets coalesced, it's likely that there was very little ices/gas around the inner planets when they formed and the Earth's atmosphere and ...

9

why Argon specifically? Both helium and neon are pretty lightweight, tend to vaporize easily even at low temperatures, and are chemically inert. For all these reasons combined, they tend to not get trapped when planets are formed - and when they do get trapped they leak out easily. Argon is just heavy enough to not escape easily into space, so some ...

8

There is not much doubt that the abundance of carbon in the protosolar nebula was not abnormal. We can tell that by looking at the carbon abundance in the atmosphere of the Sun - it has an abundance of 8.43 on a logarithmic (base 10) scale where hydrogen has an abundance of 12 (Asplund et al. 2009). This is typical for stars in the solar neighbourhood. ...

8

We have very good data on the heavy metals in the solar wind from the Charge, Element, Isotope Analysis System (CELIAS) on SOHO: Some of these elements were previously known; others were observed for the first time. The new ones are phosphorus, chlorine, potassium, titanium, chromium, and nickel. They were detected in smaller amounts than, say, carbon, ...

7

A page from the Institute for Advanced Study links to data from various modifications to the Standard Solar Model. The newest given there is from Bahcall1 et al. (2005), which I'll use as an example. The authors' calculations depend on data from the Opacity project. Data from two models are available through the IAS link: the BS05(AGS, OP) model and the BS05(...

5

This is a very broad question: its answer involves the full details of stellar evolution, Galactic chemical evolution and nuclear physics. I'll limit myself to the following observations: The elements you mention (actually are all "islands of nuclear stability". Whilst their binding energy per nucleon is not as high as that of iron, it is a little higher ...

4

You can get relatively high metallicity rather quickly in parts of the early universe -- especially some globular clusters and the centers of massive galaxies -- because star formation rates in those places were very high, which means lots of massive stars and several rounds of "massive stars form, go supernova and seed surrounding gas with metals, new ...

4

This is an excellent question. Think about the way in which emission happens. $\text{H}\alpha$ emission happens when an electron makes a transition from the third energy level to the second, emitting a photon in the process with the energy equivalent to the difference of the energies of the two states, roughly $1.9\text{ eV}$. There's a lot of hydrogen in ...

4

Meteorite abundances are referenced to their silicon abundance and then that is bootstrapped onto the hydrogen scale by assuming that the silicon abundance of meteorites is the same as that in the Sun. See for example Asplund et al. (2009). This means there is an additional uncertainty of a couple of hundredths of a dex when comparing meteoritic and solar ...

4

I think it's an interesting question. The trick would be a sustained fission reaction, faster than half life, but slower than a chain reaction. A chain reaction could hardly be considered "star like" - it would just explode. Lets say you had a planet sized object, maybe 100 parts Iron, basically inert, to 1 part Uranium , which would generate heat ...

3

Neither of these, interestingly enough, is the first time iron has been detected in an exoplanetary atmosphere. Other groups (Hoeijmakers et al. 2018, cited by both papers) have detected absorption lines of iron and other metals in the day-night transition zone of exoplanets, during transit. Ehrenreich et al. 2020, the new ESO paper, did something similar. ...

3

If the line emission is optically thin, then the measured line flux is proportional to the abundance $F_{\nu} \sim n$ of a species along the line of sight (if it's only one species). The problem here is that $F_{\nu}$ needs to be measured relative to a baseline. If that fails, e.e. when the stellar signal is too noisy, one doesn't know what this should be. ...

3

Although carbon is highly abundant in the universe, it is not homogeneously distributed. Some regions of the interstellar medium could be rich in carbon and others rich in silicon or oxygen, depending on the source of the heavier elements ("metals"). The region could be enriched from mass loss of evolved stars, or from a SN of a massive star, or from a SN ...

3

The initial stars were made of hydrogen and helium. These enriched the interstellar medium (ISM) with some chemical elements right across the periodic table, when massive primordial stars ended their lives as supernovae. Subsequent generations of stars continue to enrich the ISM, if their lives are short enough. So the general gist of what you suggest is ...

2

I highly recommend Nucleosynthesis and Chemical Evolution of Galaxies by Bernard Pagel. It contains the basics of nuclear reactions andstellar evolution, chapters on big bang nucleosynthesis and light element production, as well as covering the broad swathe of stellar nucleoynthesis and how these link together into predicting the chemical evolution of ...

2

The "lithium test" for a brown dwarf involves measuring two things - the lithium content and the spectral type (a proxy for surface temperature) or luminosity. But you may also need to know (or assume) something about the age of the object. The method is useful because the tracks of low-mass stars and brown dwarfs run together very closely in the usual ...

2

Just to add, while I think Rob Jeffries answer covers it. Now is it expected that in future more stars will be made of more heavy elements or are there causes/laws which prohibit stars forming of e.g. stars made of elements without hydrogen. While this is unlikely to happen because Hydrogen will stick around as the most abundant element for a very ...

2

The measurement of a chemical abundance is not a question of using a simple equation. The simplest it gets is using a "curve of growth", which relates equivalent width to abundance and assumes you already know the temperature of the star and its surface gravity. For the Li 6708A line, the relevant tables, that can be interpolated, are found in Soderblom et ...

2

It is very unlikely with the normal fission process for most of the elements. They can be divided into 2 groups: slow reaction and fast reactions. The elements with slow reactions do not generate enough energy in a short enough time to be able to heat sufficiently to provide light. The elements with fast reactions would disappear before enough accumulated ...

2

First of all, your first question. This source clearly state that Values are given in the usual logarithmic (dex) scale, for the same formula that you quoted (similar job). It is a bit tricky as the article "explains" the values, but you have to pay attention to the exact definition. I think it is better to work out with an example. Let's take the He. ...

2

I just found out the answer to my question from a live press release on You Tube that has been covered by blogs like this: http://news.nationalgeographic.com/2017/10/gravitational-waves-discovered-neutron-stars-pictures-science/ What LIGO does is tell you what is causing the gamma ray burst that can be studied different ways. The highly anticipated ...

1

Since this seems to be a kind of niche question I will answer and leave some comments for future souls with the same problem. To whom it may interest that may be searching for the same problem. The solution is the basic $M = m + 5( \log (parallax) + 1)$. Parallax in arcsec. The reason I'm going with K instead of V is due to a more independent ...

1

From the introduction of the source paper, we can see that what is described is a particular bump in the extinction curve of the galaxy centered at 2175 Ångström (a unit of length used for wavelength). The strength of this bump is large compared to the Large Magellanic Cloud, and is rarer toward the Small Magellanic Cloud. As mentioned in the comments, the ...

1

Yes it will, in the sense that one of the major sources of uncertainty is how common these events are. The detection of (a population) of such events will give us a handle on that number, at least for the present-day milky way. Indeed, the one detection of GW170817 has moved us from an upper limit situation to getting the rate (in the local universe) to an ...

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