On this day in science history: the earliest recorded confirmed total solar eclipse occurred

In 709 BC, the earliest record of a confirmed total solar eclipse was written in China. From: Ch'un-ch'iu, book I: "Duke Huan, 3rd year, 7th month, day jen-ch'en, the first day (of the month). The Sun was eclipsed and it was total." This is the earliest direct allusion to a complete obscuration of the Sun in any civilisation. The recorded date, when reduced to the Julian calendar, agrees exactly with that of a computed solar eclipse. Reference to the same eclipse appears in the Han-shu ('History of the Former Han Dynasty') (Chinese, 1st century AD): "...the eclipse threaded centrally through the Sun; above and below it was yellow." Earlier Chinese writings that refer to an eclipse do so without noting totality.

Total Solar Eclipse. I, Luc Viatour [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons

Having fascinated mankind for years, the Sun is the star at the centre of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99.86% of the total mass of the Solar System. About three quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron.

The Sun is a G-type main-sequence star (G2V) based on its spectral class. As such, it is informally referred to as a yellow dwarf. It formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core. It is thought that almost all stars form by this process.

The Sun is roughly middle-aged; it has not changed dramatically for more than four billion years, and will remain fairly stable for more than another five billion years. After hydrogen fusion in its core has diminished to the point at which it is no longer in hydrostatic equilibrium, the core of the Sun will experience a marked increase in density and temperature while its outer layers expand to eventually become a red giant. It is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury and Venus, and render Earth uninhabitable.

The enormous effect of the Sun on Earth has been recognized since prehistoric times, and the Sun has been regarded by some cultures as a deity. The synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today.

For more information, visit:

https://todayinsci.com/7/7_17.htm

https://en.wikipedia.org/wiki/Sun

http://www.prlabs.co.uk/lab-supplies.php?N=iron-1000ppm-for-icp&Id=60140

Which Earth-Size Planets are Habitable?

A University of Oklahoma post-doctoral astrophysics researcher, Billy Quarles, has identified the possible compositions of the seven planets in the TRAPPIST-1 system. Using thousands of numerical simulations to identify the planets stable for millions of years, Quarles concluded that six of the seven planets are consistent with an Earth-like composition. The exception is TRAPPIST-1f, which has a mass of 25 percent water, suggesting that TRAPPIST-1e may be the best candidate for future habitability studies.

"The goal of exoplanetary astronomy is to find planets that are similar to Earth in composition and potentially habitable," said Quarles. "For thousands of years, astronomers have sought other worlds capable of sustaining life."

The Earth seen from space, by NASA/Apollo 17 crew; taken by either Harrison Schmitt or Ron Evans [Public domain or Public domain], via Wikimedia Commons

Quarles, a researcher in the Homer L. Dodge Department of Physics and Astronomy, OU College of Arts and Sciences, collaborated with scientists, E.V. Quintana, E. Lopez, J.E. Schlieder and T. Barclay at NASA Goddard Space Flight Center on the project. Numerical simulations for this project were performed using the Pleiades Supercomputer provided by the NASA High-End Computing Program through the Ames Research Center and at the OU Supercomputing Center for Education and Research.

TRAPPIST-1 planets are more tightly spaced than in Kepler systems, which allow for transit timing variations with the photometric observations. These variations tell the researchers about the mass of the planets and the radii are measured through the eclipses. Mass and radius measurements can then infer the density. By comparing Earth's density (mostly rock) to the TRAPPIST-1 planets, Quarles can determine what the planets are likely composed of and provide insight into whether they are potentially habitable.

TRAPPIST-1f has the tightest constraints with 25 percent of its mass in water, which is rare given its radius. The concern of this planet is that the mass is 70 percent the mass of Earth, but it is the same size as Earth. Because the radius is so large, the pressure turns the water to steam, and it is likely too hot for life as we know it. The search for planets with a composition as close to Earth's as possible is key for finding places that we could identify as being habitable. Quarles said he is continually learning about the planets and will investigate them further in his studies.

TRAPPIST-1 is a nearby ultra-cool dwarf about 40 light-years away from Earth and host to a remarkable planetary system consisting of seven transiting planets. The seven planets are known as TRAPPIST 1b, c, d, e, f, g and h.

For more information visit:-

https://www.sciencedaily.com/releases/2017/06/170608145559.htm

https://en.wikipedia.org/wiki/Earth

http://www.prlabs.co.uk/lab-supplies.php?N=water-demineralized&Id=58121

The chemistry behind the new one pound coin

We all know that money makes the world go around, but do you know what goes into it? The new pound coin arrived on 28th March, largely as a preventative measure against counterfeiting.  Take a look at the graphic below for more information about its composition.

Source: Compound Interest

Why the new coin is harder to counterfeit:

1. 12-sided - its distinctive shape means it stands out by sight and by touch
2. Bimetallic - The outer ring is gold coloured (nickel-brass) and the inner ring is silver coloured (nickel-plated alloy)
3. Latent image - it has an image like a hologram that changes from a '£' symbol to the number '1' when the coin is seen from different angles
4. Micro-lettering - around the rim on the heads side of the coin tiny lettering reads: ONE POUND. On the tails side you can find the year the coin was produced
5. Milled edges - it has grooves on alternate sides
6. Hidden high security feature - an additional security feature is built into the coin to protect it from counterfeiting but details have not been revealed

For more information, visit:- 

http://www.compoundchem.com/2017/03/28/new-pound/

http://www.prlabs.co.uk/lab-supplies.php?N=nickel-1000ppm-for-icp&Id=60172