Aylesbury

Astronomical

Society

MAY 2017 NEWSLETTER - ISSUE 588

“Never follow anybody who hasn't asked "why".”
Aniekee Tochukwu Ezekiel

Future Meetings (at 7.30pm unless noted)

May 8th        AGM  plus talk by Steve on "How to set up a Telescope"

May 22nd         Committee meeting venue Winchendon observatory.

June 5th         Speaker Mike Frost on "The arms of Buddha".

June 19th         Committee meeting 7.30 at the Observatory.

July 3rd         Talk by Jeremy Batch on the history of Navigation

July 24th        Committee meeting at Winchendon observatory

July 29th         AAS annual BBQ at the Winchendon observatory.

August 7th           Dr Allan Chapman awaiting date confirmation.

August 21st          Committee meeting at Winchendon observatory

September 4th          AAS meeting cancelled due to trip.

September 5th          AAS trip to Diamond Lite

Observing.

This month true darkness begins rapidly to diminish due to the Earth’s angle of inclination in relation to the plane of our solar system.  Astronomical dusk begins at just before 11pm on the 1st May and ends at just past 3 in the morning.  By the 14th astronomical dusk begins at 11.46pm and ends at 2.11am.  By the end of the month, there is no astronomical dusk and dawn for those at this latitude, as the Sun never sets more than 18 degrees below the horizon - and true astronomical darkness is not achieved again until the end of July. Until then the main focus has to be on the solar system.

Planets.

Mercury is now a morning object, having emerged from behind the Sun. It will be extremely difficult to observe this month since its elevation will be similar to the Sun's.

Venus begins May as a morning object, a 37.8 arc second diameter, 27.1% illuminated crescent, -4.5 mag in brightness, separated from the Sun by nearly 40 degrees and standing just under 12 degrees high at sunrise. It should be visible to the naked eye in daylight. If you have a planetarium app on your mobile phone it will be helpful in locating the planet.

Jupiter is moving further away from us and is beginning to diminish slightly in size and brightness, though it is still the largest solar system object in the sky after the sun and moon. This remains a prime time to observe the planet: it transits around 10.30pm, negating the need for keeping unsociable hours to see it at its best.

Mars is heading towards inferior conjunction in July and its diameter is now not much greater then Uranus. Best forget it for a while unless you're feeling adventurous.

At the beginning of the month, Saturn rises in Sagittarius a little after midnight, shining at +0.3 mag and 17.8 arc seconds in diameter.  By the 15th May, it will have brightened to +0.2 mag and increased fractionally in diameter, rising a little after 11pm and transiting at 3.13am. 

At the end of the month, Saturn will have brightened to +0.1 mag and grown to 18.3 arc seconds in diameter.  The Ringed Planet now rises at a little after 10pm and transits in the south at 2.10am. Unfortunately, the planet will only achieve a little over 15 deg elevation, so a decent southern view and favorable sky conditions will be needed to see it to full advantage.

The Moon.

On 1st May, the moon is a 24% illuminated waxing crescent about 55deg high at sunset. Because of the moon's altitude, this time of year is great for Lunar observing - the effects of atmospheric turbulence are reduced and the residue of summer daytime heat is not yet having an effect on seeing.

On the 7th May, the nearly-full moon and Jupiter will be less than 2 degrees apart. Weather permitting, this will be an excellent photographic opportunity.

The Eta Aquariids meteor shower peaks on the nights of May 5th-7th. This shower is seeded by Halley’s Comet, whose debris is quite fast-moving, resulting in bright, energetic meteors. The shower is expected to peak at around 20 meteors per hour and will be best observed with the naked eye, the optimum time being a couple of hours before dawn. The radiant is in the east south-east.

Deep sky.

With the imminent loss of astronomical darkness, this will be a last chance for a while to go galaxy hunting. However, it will still be possible to pick out some of the brightest objects. Try to find NGC4565, the Needle Galaxy, in Coma Berenices. It lies at the apex of a triangle formed with the bright star Arcturus and Alkaid - the last star in the 'handle' of the Big Dipper. At mid month it will reach a maximum elevation of about 65 degrees by 22.00 BST. The galaxy lies about 40 million light-years distant and spans some 100,000 light-years. It is easily spotted with small telescopes, and is one of the more prominent objects missed by Charles Messier. NGC 4565 has at least two satellite galaxies, one of which is interacting with it. It has a population of roughly 240 globular clusters, more than the Milky Way, and is more luminous than the Andromeda galaxy.

NGC 4565 - The Needle Galaxy

Image credit: Ken Crawford

While in Coma Berenices, look for the globular cluster M53. At 58,000 light years from us, the cluster is rather dimmer at +7.6 mag than other major globulars, but should be reasonably easy to spot in any telescope. Here it is in a Hubble image:

M 53

Image credit: NASA / HST

Cassini.

On 26th April, the Cassini space probe, having been manoeuvred into a highly elliptical orbit, performed the first of 22 planned dives through the rings around Saturn. The spacecraft is almost out of fuel for navigation, and these dangerous trips inside the rings will be its last mission before being crashed into the planet. The spacecraft was turned so that its large dish antenna was pointing in the direction of travel to act as a shield against particles of ring material. Cassini survived its first dive and has sent images back to earth. At this time, they have not been processed, but some of the initial raw images can be seen on NASA's site here:

https://saturn.jpl.nasa.gov/galleries/raw-images/

(for the above link, filter the images between the dates 2017-04-26 and the current date and sort by oldest)

After the close passes, Cassini will be consumed by Saturn in order to prevent any chance of it being captured by one of Saturn's moons, crashing onto it and causing contamination. The worry applied particularly to Enceladus which is thought to be a prime candidate for harbouring extraterrestrial life. Enceladus is an active moon that hides a global ocean of liquid salty water beneath its crust. Jets of icy particles from that ocean, laced with a brew of water and simple organic chemicals, gush out into space continuously from this fascinating ocean world. The material shoots out at about 400 meters per second and forms a plume that extends hundreds of miles into space. Some of the material falls back onto Enceladus, and some escapes to feed Saturn’s vast E ring

Graphic showing probable sub-surface structure of Enceladus and possible life-supporting hydrothermal vents.

Credit: NASA

"Where Do We Come From? What Are We? Where Are We Going? "

Paul Gauguin inscribed this title in French in the upper left corner of his enigmatic painting. The inscription the artist wrote on his canvas has no question mark, no dash, and all words are capitalized. In the upper right corner he signed and dated the painting: P. Gauguin / 1897.

It is the fundamental question that drives the whole of science and philosophy. Within the context of the astronomical, physical and mathematical sciences we have many clues.

Where do we come from?

The Big Bang, some 13.8 billion years ago, was the beginning of our physical universe, and the point at which the laws of nature manifested. The concept of a Big Bang derived from the observations of  Edwin Hubble in 1929. From an analysis of galactic redshifts, Hubble concluded that galaxies are drifting apart; providing important observational evidence of the concept of an expanding universe. Georges Lemaître had earlier pointed out that if the universe were expanding, it could be traced back to a specific point in time where that expansion began. Backward extrapolation of the expansion using general relativity yields an infinite density and temperature at a finite time 13.8 billion years in the past. This mathematical 'singularity' indicates that general relativity is not an adequate descriptor of the laws of physics in this regime. However, the Big Bang more properly represents the point in history where the universe can be verified to have entered into a state where the laws of physics as we understand them - specifically general relativity and the standard model of particle physics - work.

Pascual Jordan, a theoretical and mathematical physicist who made significant contributions to quantum mechanics and quantum field theory, first suggested that since the positive energy of a star’s mass and the negative energy of its gravitational field together may have zero total energy, conservation of energy would not prevent a star being created by a quantum transition of the vacuum. George Gamow recounted putting this idea to Albert Einstein: “Einstein stopped in his tracks and, since we were crossing a street, several cars had to stop to avoid running us down”. A zero-energy universe theory originated in 1973, when Edward Tryon proposed in the journal Nature that the universe may have emerged from a large-scale quantum fluctuation of vacuum energy, resulting in its positive mass-energy being exactly balanced by its negative gravitational potential energy.

It is this balancing of the total universal energy budget that enables the open-ended growth possible. During inflation, energy flows from the gravitational field to the inflation field - the total gravitational energy decreases (i.e. becomes more negative) and the total inflation energy increases (becomes more positive), but the respective energy densities remain constant and opposite. Consequently, inflation explains the otherwise curious cancellation of matter and gravitational energy on cosmological scales, which is consistent with astronomical observations.

From the beginning[1], the germinal universe underwent extremely rapid expansion and continued to decrease in density and fall in temperature until it had cooled sufficiently to allow the formation of subatomic particles. After about 10−11 seconds, particle energies dropped to values that can be attained in particle accelerators where their properties can now be studied directly. At about 10−6 seconds, primordial quarks and gluons combined to form baryons such as protons and neutrons. Temperatures were so high that the random motions of particles were at relativistic speeds, and particle–antiparticle pairs of all kinds were being continuously created and destroyed in collisions. At some point, an unknown reaction called baryogenesis led to a small excess of baryons over anti-baryons. The temperature was now no longer high enough to create new particle–antiparticle pairs, so a mass annihilation immediately followed, leaving just one in 1010 of the original protons and neutrons, and virtually none of their antiparticles. A similar process happened at about 1 second for leptons (electrons and positrons). These events resulted in the predominance of matter over antimatter in the present universe.

A few minutes into the expansion, when the temperature was about a billion degrees kelvin and the density was about that of air, neutrons were able to combine with protons to form a plasma of deuterium and helium nuclei, with most protons remaining uncombined as hydrogen nuclei. This state continued for about 379,000 years, after which the temperature had dropped sufficiently to allow these nuclei to combine with electrons and condense into atoms. Thus radiation (energy) decoupled from matter (mass) and continued through space largely unimpeded. This relic radiation permeates space and is known as the cosmic microwave background radiation.

Giant clouds of primordial elements later coalesced through gravity in halos of dark matter, eventually forming the stars and galaxies visible today.

Primordial hydrogen fuelled the first-generation of stars which, through nuclear synthesis, generated heavier elements. These elements were distributed into space on the death of these stars and contributed to the materials that accreted to form subsequent generations of solar systems. All the elements heavier than iron (atomic weight 55) cannot be formed by nuclear fusion reactions within stars: such elements need a net input of energy to be created and are formed only in supernova explosions[2].

The eXtreme Deep Field, or XDF.

The XDF image was assembled by combining 10 years of Hubble Space Telescope photographs taken of a patch of sky at the centre of the original Hubble Ultra Deep Field. The field of the XDF is a small fraction of the angular diameter of the full moon and contains about 5,500 galaxies, some of which are ten billion times dimmer than the human eye can see. The history of galactic formation is laid out in this one remarkable image, revealing galaxies that span back 13.2 billion years to when most of these galaxies were young, small, and growing.

What are we?

It is believed that the elements essential to life may have formed by the time the universe was only 10–17 million years old. What is certain is that we, and everything around us, are made from the ashes of dead stars.

If we respectfully put to one side the Creationist belief, we are very much in the dark as to how life began on Earth. We do know that the early atmosphere was very different from the atmosphere now. In 1952, Stanley Miller and Harold Urey designed an experiment to see how complex organic molecules might have formed under the conditions of the early Earth. They believed the early atmosphere would have been composed of methane, ammonia, hydrogen and water vapour. They sealed these gases in an airtight container, and then exposed the gases to sparks of electricity to simulate lightning. They continued the lightning for a week, and by the end, a reddish-brown substance had coated the walls of the container. This substance contained 11 of the 20 amino acids used by life on earth. Since this experiment was first performed, its results have been confirmed many times by other scientists (although many scientists now believe that the early Earth’s atmosphere was more probably composed of carbon dioxide, nitrogen and water vapour).

The Miller - Urey experiment.

Scientists have not been able to replicate the formation of even simple organisms, or anything that can really replicate itself. However, there are several theories as to how the amino acids might have made the leap into the complex, self-replicating life we see today.

One theory supposes that metabolism (for example, the ability to upgrade inorganic molecules in the presence of a catalyst into small organic molecules) was the precursor to the first life. There are many different theories as to exactly what types of molecules and catalysts would have been involved.

Other theories postulate that the first living organisms may have been genes. These genes were single molecules that had developed in such a way as to be able to catalyze their own replication. This theory seems more likely, since even simple systems such as crystals, have been demonstrated to evolve with modifications that breed true. Some scientists have suggested that certain compositions of clay create the right environment for these reactions to propagate.

RNA is a complex molecule found in all living things that seems to be able to catalyze its own reproduction. It may be that simple RNA molecules developed and eventually became more complex and evolved into primitive organisms.

Astrobiologists and biochemists are investigating a concept called LUCA (the Last Universal Common Ancestor). The idea is that all life on Earth has a common ancestor, kind of like a great-great-great-....-great grandmother. They search for traits that are common across all life forms and assume that these traits must have been inherited from this common ancestor. Results of these studies indicate that if LUCA existed, it lived at least 2 billion years ago, before there was much oxygen in the atmosphere. It used enzymes containing iron in its metabolic pathways. It stored genetic information in DNA, had several hundred proteins performing a variety of functions, and used the same 20 amino acids we use in our own proteins. LUCA also used RNA and had some kind of double-layer lipid membrane. It was probably the ancestor of the three kingdoms of life: Archaea, Eukaryotes and Bacteria.

Studying how life arose on Earth is useful to astro-biologists, but they keep in mind that the way life formed on Earth is not the only way life could have formed. It is simply one way that it did.

Thomas Gold, a professor of astronomy, suggested in 1960 the hypothesis of "Cosmic Garbage", that life on Earth might have originated accidentally from a pile of waste products dumped on Earth long ago by extraterrestrial beings...

Fred Hoyle and Chandra Wickramasinghe have speculated that several outbreaks of illnesses on Earth are of extraterrestrial origin, including the 1918 flu pandemic, and certain outbreaks of polio and mad cow disease. For the 1918 flu pandemic they hypothesized that cometary dust brought the virus to Earth simultaneously at multiple locations (a view almost universally dismissed by experts on this pandemic). After Hoyle's death, The Lancet published a letter to the editor from Wickramasinghe and two of his colleagues, in which they hypothesized that the virus that causes severe acute respiratory syndrome (SARS) could be extraterrestrial in origin and not originated from chickens. Calculations by Hoyle and Wickramasinghe, based on various assumptions about the frequency of random chemical reactions and mutations, have suggested that the earth is much too young for the molecular specializations and metabolic complexities needed for life to have evolved here. This is consistent with the concept of 'Panspermia' - the hypothesis that life exists throughout the Universe and is distributed by meteoroids, asteroids, comets, etc. The hypothesis proposes that highly organised molecules or proto-biotic life-forms that can survive the effects of space, become trapped in debris that is ejected into space after collisions between planets that harbor life and small solar system bodies. They may travel dormant for an extended amount of time before colliding randomly with other planets or intermingling with protoplanetary disks. If met with ideal conditions on a new planet's surface, the organisms become active and continue the process of chemical or biotic evolution. Thus Panspermia sees the evolution of life as a cosmic event, occurring alongside the evolution of the universe and on a comparable timescale. Panspermia does not address how life began, just the method that may cause its distribution in the Universe.

Where are we going?

Putting aside the metaphysical, and the certainty that our own lives are very brief in cosmic terms, the future of the universe itself is unclear. There are many theories concerning its possible fate.

Possible scenarios include:

... the Big Freeze, in which continued expansion results in a universe that tends towards absolute zero temperature. In this scenario, stars are expected to form normally for 1012 to 1014 (1–100 trillion) years, but eventually the supply of gas needed for star formation will be exhausted. As existing stars run out of fuel and cease to shine, the universe will inexorably grow darker. Eventually black holes will dominate the universe, which themselves will eventually disappear as they emit Hawking radiation. One (dubious) extension of this theory is that after a Big Freeze, random quantum fluctuations could produce another Big Bang in 10 to the power 10, all to the power 10, all to the power 56 years - long after bed-time and not worth waiting up for.

... the Big Rip, in which one possible form of dark energy increases in density over time, causing an acceleration of the universe's rate of expansion and leading to a steady increase in the Hubble constant. As a result, all material objects in the universe will disintegrate into unbound elementary particles and radiation, ripped apart by the dark energy force and shooting apart from each other. Paradoxically, the end state of the universe, as was its beginning, is then a mathematical singularity, as the dark energy density and expansion rate approaches infinity.

... the Big Crunch, in which it is assumed that the average density of the universe is enough to stop its expansion and begin contracting. The end result is unknown; a simple estimation would have all the matter and space-time in the universe collapse into a dimensionless singularity, but at these scales unknown quantum effects such as quantum gravity need to be considered. Recent evidence suggests that this scenario is unlikely, but it has not been ruled out.

... the Big Bounce, in which a cyclic repetition of the Big Bang is proposed and where the first cosmological event was the result of the collapse of a previous universe. According to the Big Bang theory, in the beginning the universe was infinitely dense. This seems to be at odds with everything else in physics, and especially quantum mechanics, but would predict that once this universe collapses it will spawn another universe in an event similar to the Big Bang after a universal singularity is reached or a repulsive quantum force causes re-expansion.

... the False Vacuum theory requires an understanding of the Higgs field which permeates the universe. If the vacuum of space is not in its lowest energy state (i.e. a false vacuum), it could tunnel into a lower energy state. This is referred to as the vacuum metastability event. This has the potential to fundamentally alter our universe; in the most audacious scenarios even the various physical constants could have different values, severely affecting the foundations of matter, energy, and spacetime. It is also possible that all structures will be destroyed instantaneously, without any forewarning (Yikes!!). Studies of a particle similar to the Higgs boson support the possibility of a false vacuum collapse billions of years from now. However, according to the many-worlds interpretation of quantum mechanics, the universe would not end quite in this way. Instead, each time a quantum event happens that causes the universe to decay from a false vacuum to a true vacuum state, the universe splits into several new worlds. In some of the new worlds the universe decays; in some others the universe continues as before...

And finally...

A personal note.

It has been a great pleasure to have produced the AAS Newsletter these past two years. I have enjoyed the trip, and I have learned a lot on the way, but it is now time to pass the baton.

I wish you all good fortune and good skies. Keep looking up and never stop wondering at the glory of the universe.

“Revere those things beyond science which really matter and about which it is so difficult to speak.”


Werner Heisenberg


[1] There is no well-supported model describing the action prior to 10−15 seconds or so. Apparently a new unified theory of quantum gravitation is needed to break this barrier. Understanding this earliest of eras in the history of the universe is currently one of the greatest unsolved problems in physics.

[2] One of the most curious of the heavy elements is bismuth. It has an atomic weight of 208.98 and is about twice as abundant as gold in the earth's crust. Its immediate neighbour in the periodic table, polonium (atomic weight 209), is extremely toxic and highly radioactive. Bismuth is non-toxic (bismuth subsalicylate is the active ingredient of Pepto-Bismol) and was long thought to be the element with the highest atomic mass that is stable. However, in 2003 it was discovered to be weakly radioactive: it decays via alpha decay with a half life more than a billion times the estimated age of the universe.