What is a Star?

A star is an astronomical object consisting of a luminous ball of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, the brightest of which gained proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable Universe contains an estimated 1×1024 stars, but most are invisible to the naked eye from Earth, including all stars outside our galaxy, the Milky Way.

For most of its active life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space. Almost all naturally occurring elements heavier than helium are created by stellar nucleosynthesis during the star's lifetime, and for some stars by supernova nucleosynthesis when it explodes. Near the end of its life, a star can also contain degenerate matter. 

Astronomers can determine the mass, age, metallicity (chemical composition) and many other properties of a star by observing its motion through space, its luminosity, and spectrum respectively. The total mass of a star is the main factor that determines its evolution and eventual fate. Other characteristics of a star, including diameter and temperature, change over its life, while the star's environment affects its rotation and movement. A plot of the temperature of many stars against their luminosities produces a plot known as a Hertzsprung–Russell diagram(H–R diagram). Plotting a particular star on that diagram allows the age and evolutionary state of that star to be determined.

A star's life begins with the gravitational collapse of a gaseous nebula of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. When the stellar core is sufficiently dense, hydrogen becomes steadily converted into helium through nuclear fusion, releasing energy in the process. The remainder of the star's interior carries energy away from the core through a combination of radiative and convective heat transfer processes. The star's internal pressure prevents it from collapsing further under its own gravity. 

A star with mass greater than 0.4 times the Sun's will expand to become a red giant when the hydrogen fuel in its core is exhausted. In some cases, it will fuse heavier elements at the core or in shells around the core. As the star expands it throws a part of its mass, enriched with those heavier elements, into the interstellar environment, to be recycled later as new stars. Meanwhile, the core becomes a stellar remnant: a white dwarf, a neutron star or, if it is sufficiently massive, a black hole.

Binary and multi-star systems consist of two or more stars that are gravitationally bound and generally move around each other in stable orbits. When two such stars have a relatively close orbit, their gravitational interaction can have a significant impact on their evolution. Stars can form part of a much larger gravitationally bound structure, such as a star cluster or a galaxy.

What is the Cosmos?

The Cosmos is the Universe. Using the word cosmos rather than the word universe implies viewing the universe as a complex and orderly system or entity; the opposite of chaos. 

The cosmos, and our understanding of the reasons for its existence and significance, are studied in cosmology - a very broad discipline covering any scientific, religious, or philosophical contemplation of the cosmos and its nature, or reasons for existing. Religious and philosophical approaches may include in their concepts of the cosmos various spiritual entities or other matters deemed to exist outside our physical universe.

What is the Universe?

The Universe (Latin: universus) is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. While the spatial size of the entire universe is unknown, it is possible to measure the size of the observable universe, which is currently estimated to be 93 billion light-years in diameter. In various multiverse hypotheses, a universe is one of many causally disconnected constituent parts of a larger multiverse, which itself comprises all of space and time and its contents; as a consequence, ‘the universe’ and ‘the multiverse’ are synonymous in such theories.

The earliest cosmological models of the universe were developed by ancient Greek and Indian philosophers and were geocentric, placing Earth at the centre. Over the centuries, more precise astronomical observations led Nicolaus Copernicus to develop the heliocentric model with the Sun at the centre of the Solar System. In developing the law of universal gravitation, Isaac Newton built upon Copernicus' work as well as Johannes Kepler's laws of planetary motion and observations by Tycho Brahe.

Further observational improvements led to the realisation that the Sun is one of hundreds of billions of stars in the Milky Way, which is one of at least hundreds of billions of galaxies in the universe. Many of the stars in our galaxy have planets. At the largest scale, galaxies are distributed uniformly and the same in all directions, meaning that the universe has neither an edge nor a centre. At smaller scales, galaxies are distributed in clusters and superclusters which form immense filaments and voids in space, creating a vast foam-like structure. Discoveries in the early 20th century have suggested that the universe had a beginning and that space has been expanding since then, and is currently still expanding at an increasing rate.

The Big Bang theory is the prevailing cosmological description of the development of the universe. According to estimation of this theory, space and time emerged together 13.799±0.021 billion years ago and the energy and matter initially present have become less dense as the universe expanded. After an initial accelerated expansion called the inflationary epoch at around 10−32 seconds, and the separation of the four known fundamental forces, the universe gradually cooled and continued to expand, allowing the first subatomic particles and simple atoms to form. 

Dark matter gradually gathered, forming a foam-like structure of filaments and voids under the influence of gravity. Giant clouds of hydrogen and helium were gradually drawn to the places where dark matter was most dense, forming the first galaxies, stars, and everything else seen today. It is possible to see objects that are now further away than 13.8 billion light-years because space itself has expanded, and it is still expanding today. This means that objects which are now up to 46.5 billion light-years away can still be seen in their distant past, because in the past, when their light was emitted, they were much closer to Earth.

From studying the movement of galaxies, it has been discovered that the universe contains much more matter than is accounted for by visible objects; stars, galaxies, nebulas and interstellar gas. This unseen matter is known as dark matter (dark means that there is a wide range of strong indirect evidence that it exists, but we have not yet detected it directly). 

The ΛCDM model is the most widely accepted model of our universe. It suggests that about 69.2%±1.2% of the mass and energy in the universe is a cosmological constant (or, in extensions to ΛCDM, other forms of dark energy, such as a scalar field) which is responsible for the current expansion of space, and about 25.8%±1.1% is dark matter. Ordinary ('baryonic') matter is therefore only 4.84%±0.1% of the physical universe. Stars, planets, and visible gas clouds only form about 6% of ordinary matter, or about 0.29% of the entire universe.

There are many competing hypotheses about the ultimate fate of the universe and about what, if anything, preceded the Big Bang, while other physicists and philosophers refuse to speculate, doubting that information about prior states will ever be accessible. Some physicists have suggested various multiverse hypotheses, in which our universe might be one among many universes that likewise exist.

What is Astrology?

Astrology is a pseudoscience that claims to divine information about human affairs and terrestrial events by studying the movements and relative positions of celestial objects. Astrology has been dated to at least the 2nd millennium BCE, and has its roots in calendrical systems used to predict seasonal shifts and to interpret celestial cycles as signs of divine communications. 

Many cultures have attached importance to astronomical events, and some—such as the Hindus, Chinese, and the Maya—developed elaborate systems for predicting terrestrial events from celestial observations. Western astrology, one of the oldest astrological systems still in use, can trace its roots to 19th-17th century BCE Mesopotamia, from where it spread to Ancient Greece, Rome, the Arab world and eventually Central and Western Europe. Contemporary Western astrology is often associated with systems of horoscopes that purport to explain aspects of a person's personality and predict significant events in their lives based on the positions of celestial objects; the majority of professional astrologers rely on such systems.

Throughout most of its history, astrology was considered a scholarly tradition and was common in academic circles, often in close relation with astronomy, alchemy, meteorology, and medicine. It was present in political circles and is mentioned in various works of literature, from Dante Alighieri and Geoffrey Chaucer to William Shakespeare, Lope de Vega, and Calderón de la Barca. 

Following the end of the 19th century and the wide-scale adoption of the scientific method, researchers have successfully challenged astrology on both theoretical and experimental grounds, and have shown it to have no scientific validity or explanatory power. Astrology thus lost its academic and theoretical standing, and common belief in it has largely declined. While polls have demonstrated that approximately one quarter of American, British, and Canadian people say they continue to believe that star- and planet-positions affect their lives, astrology is now recognised as a pseudoscience - a belief which its advocates incorrectly present as scientific.

My blog is about Astronomy, not Astrology.

What is Astronomy?

Astronomy (from Greek: ἀστρονομία) is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates outside Earth's atmosphere. Cosmology is a branch of astronomy which studies the Universe as a whole.

Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky. These include the Babylonians, Greeks, Indians, Egyptians, Chinese, Maya, and many ancient indigenous peoples of the Americas. In the past, astronomy included disciplines as diverse as astrometry, celestial navigation, observational astronomy, and the making of calendars. Nowadays, professional astronomy is often said to be the same as astrophysics.

Professional astronomy is split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects. This data is then analyzed using basic principles of physics. Theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. These two fields complement each other. Theoretical astronomy seeks to explain observational results and observations are used to confirm theoretical results.

Amateurs play an active role in astronomy. It is one of the few sciences in which this is the case. This is especially true for the discovery and observation of transient events. Amateur astronomers have helped with many important discoveries, such as finding new comets.

What is a Galaxy?

A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. The word galaxy is derived from the Greek galaxias (γαλαξίας), literally "milky", a reference to the Milky Way. Galaxies range in size from dwarfs with just a few hundred million stars to giants with one hundred trillion stars, each orbiting its galaxy's centre of mass.

Galaxies are categorised according to their visual morphology as elliptical, spiral, or irregular. Many galaxies are thought to have supermassive black holes at their centres. The Milky Way's central black hole, known as Sagittarius A*, has a mass four million times greater than the Sun. As of March 2016, GN-z11 is the oldest and most distant observed galaxy with a co-moving distance of 32 billion light-years from Earth, and observed as it existed just 400 million years after the Big Bang.

Research released in 2016 revised the number of galaxies in the observable universe from a previous estimate of 200 billion to a suggested two trillion or more and there are more stars in the universe than all the grains of sand on planet Earth.

Most of the galaxies are 1,000 to 100,000 parsecs in diameter (approximately 3,000 to 300,000 light years) and separated by distances on the order of millions of parsecs (or megaparsecs). For comparison, the Milky Way has a diameter of at least 30,000 parsecs (100,000 ly) and is separated from the Andromeda Galaxy, its nearest large neighbour, by 780,000 parsecs (2.5 million ly.)

The space between galaxies is filled with a tenuous gas (the intergalactic medium) having an average density of less than one atom per cubic meter. The majority of galaxies are gravitationally organized into groups, clusters, and superclusters. The Milky Way is part of the Local Group, which is dominated by it and the Andromeda Galaxy and is part of the Virgo Supercluster. At the largest scale, these associations are generally arranged into sheets and filaments surrounded by immense voids. Both the Local Group and the Virgo Supercluster are contained in a much larger cosmic structure named Laniakea.

Return to Bowland

On Tuesday I went out for the first time in four months to look for the Milky Way. With it only just being past the summer solstice it wasn't the best time I know, but I was I was wondering how dark it got in our usual spot in the Forest of Bowland. The answer is, not very - certainly not dark enough to see the Milky Way properly, although the murky high level clouds didn't help. No noctilucent clouds either, which was another thing I was hoping for.

As my broken tracking mount has still not been returned, I could only take a wide angle set up with me to do some constellation shots.

So I didn't come back with much except for a few shots like this one showing Cassiopeia and Andromeda - can you see it? The best thing was meeting up with John and Susan Walsh and having a chat at an appropriate distance.

A very small and faint Andromeda is ringed in the above photo.

Jupiter and Saturn over Pendle Hill, looking south from Bowland. It wasn't this light, but the camera can make it seem brighter. And that's no sunset, it's the light pollution from Clitheroe. A bit over-sharpened I'm afraid.

So not many photos to process for once, but here's a couple of annotated asterisms to finish with:

Astronomy and Space Sessions for Primary Schools

Attention all primary school teachers, governors, youth workers and anyone connected to primary schools or youth groups. I'm looking to offer astronomy sessions to schools.

I'm a former secondary school Computing and IT teacher who took early retirement from being Head of Faculty a few years ago. I did some IT support work for a while before going on to work one day a week for four years in a primary school where I taught the basics of computer programming to Years 3-6.

In addition, for the last six years or so I've coordinated a team of five volunteers who visit primary schools and youth groups giving free presentations about birds, wildlife and nature as part of Leigh Ornithological Society's education programme in the Wigan and Leigh area. This team were instrumental in helping the Society receive the Queen's Award for Voluntary Service in June 2020.

But now I'm looking to branch out and hopefully earn a bit of pocket money to help fund my astrophotography habit. So I'm looking to offer primary schools a two hour afternoon (paid) session about astronomy, the solar system and space topics in general. The session would include a presentation with high quality information slides and photographs, demonstrations, a practical activity, quizzes and worksheets all in line with National Curriculum topics. The exact content can be tailored to individual schools.

So if you are a primary school teacher, governor or have some other connection with a school or youth group who you think would be interested in this sort of session, please get in touch via an email to jones_mp@yahoo.com.

Obviously, these sessions will only be able to take place when we are back to normal after the current Coronavirus situation has passed. But that will give me some time to prepare the materials!

I'm Not Phased By These Moonshots

My first attempt at showing a sequence of moon phases for the end of May 2020.

Far from perfect as it was a bit of an afterthought really. I'd need to set up more consistently each night to improve the quality. But I'm sure that sooner or later, everyone wants to try to do something like this.

Strawberry Moon in June 2020

The best I could do with last night's 'Strawberry Moon' (5/6/20).
Too cloudy and dull all night and this shot was taken through thin cloud.

It's called a Strawberry Moon because it coincides with when strawberries were originally harvested. Less common nicknames for this month's full moon, based on old European naming traditions, are the Mead Moon, Honey Moon, and Rose Moon.

Reprocessed Sunspot AR 2765

Sunspot AR 2765 - (13:24pm 5/6/20)

Reprocessed to enhance the faculae or bright areas near the actual sunspot.

Sunspots are temporary phenomena on the Sun's photosphere that appear as spots darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection. Sunspots usually appear in pairs of opposite magnetic polarity. The Sun's magnetic field wells up to the photosphere which is the Sun's visible "surface". The powerful magnetic fields around sunspots produce active regions (AR) on the Sun, which often lead to solar flares and Coronal Mass Ejections (CMEs).

You Never Forget Your First Sunspot

Wow! I've just taken my first ever photo of a sunspot! Thanks to Anthony Wallace Cross from the Manchester Astronomical Society for the heads up.

AR 2765 (Lower left side)

A closer view:

WARNING: DO NOT LOOK DIRECTLY AT THE SUN THROUGH A CAMERA VIEWFINDER, BINOCULARS OR A TELESCOPE. ALWAYS USE A SPECIAL SOLAR FILTER AND CHECK THAT IT IS NOT DAMAGED.