CLOCK
To evolve from apes 7 hrs
Homo Sapiens so far 10mins
Human history 30secs
1000 years 3secs
I year 3msec
To make sense of which parts of the universe is visible, I have tried to construct some simple concepts of our place in the universe.
The view from earth at midnight, is much like light from a lighthouse. The view, shown as a "tube", following earths orbit around the sun. In June the view is of the core of the Milky Way. The core blocks the view of the universe beyond the core.
Understanding the view from earth is a bit of a brain-tease that has confused people on and off for thousands of years. For the purposes of viewing the Universe, we need the darkest possible skies.
Days - Earth spins on its axis, giving rise to our days and nights.
Months - determined by the orbit of the moon around the earth that gives rise to our monthly cycle and the daily tides. The best viewing are found with the darkest skies that occur when at midnight, the moon is on the same side as the sun. The moon appears during the day and is backlite by the sun - a "New Moon".
Earth orbits the sun, giving rise to our year. The Earths spin axis points at the star Polaris and is tilted 23 degrees to the plane earth/sun orbit, giving rise to the seasons. In June with summer in the northern hemisphere occurring when oriented with the spin axis. For the observer, the nights in the northern hemisphere are longest.
The darkest sky occurs at midnight when the observer is on the opposite side of earth to the sun. The simplest reference view is 180 degrees centered on directly overhead. In the spin direction, the view from dark skies after sunset to sunset covers a roughly 270 degree view.
The by month view of the Milky Way at midnight from Austin TX, 35 degrees North. Best views overhead in August and January.
The ecliptic at night is the opposite of the day, overhead in the winter, low in the sky in summer. The ecliptic is fixed relative to Milky Way,
In March, the Milky way is just on the horizon, hence my photo in Marathon in 2021.
The white hemispheres illustrate the 180 degree view from the equator The plane of the earths spin rotation relative to the plane of the orbit around the sun (ecliptic) , affects the view in June and December.
The sketch shows the how the view of the Milky Way works. It starts from the Suns location in the plane of the Milky Way.
The earth-sun orbital plane (ecliptic) is oriented at 63 degrees to the plane of the Milky Way pointing at the galactic center. The north spin axis of the Earth at 23 degrees to the ecliptic, is oriented away from the center of the Milky Way, fixing the seasons so that earth is positioned between the core and sun in June. The overhead view from the equator on earth at midnight is always directly away from the Sun. At midnight in June, the view is of the center of the Milky Way. At midnight in December, the overhead view from earth is directly way from the center of the Milky Way.
The "pictures" of the Milky Way are for an observer at the equator. As the observer moves towards the poles, portions of the core get obscured.
Andromeda and other deep sky objects outside Milky Way are visible in mid-winter.
For the northern deep sky galaxies, June will position the galaxies low in the E-NE sky to give a good alignment with foreground objects. Moon in the SE.
For galaxies just south of the Milky Way, they are low in the NE sky Aug and Sept.
The target galaxies and moon all to scale are shown. The idea is to show all these behind elements of the capitol for scale.
DARK ENERGY 68% of universe
The universe is expanding more quickly over time, ie. there is a force pushing the universe apart.
In late 1998, a team of astronomers aimed to calculate the expansion rate of the universe in the form of a constant value, known as the Hubble Constant.
They were studying supernovas in distant galaxies and they discovered that distant galaxies were drifting away from us much faster than the nearby galaxies.
They realized that the universe wasn’t expanding at a consistent rate but an accelerating rate of pace. Hence, the concept of the Hubble Constant was contradicted.
Albert Einstein was the first person to state that space is not empty, and it consists of some invisible force. He gave the property of space that it was capable to expand beyond reach.
In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the universe does not expand at a constant rate; rather, the universe's expansion is accelerating.[1][2] Understanding the universe's evolution requires knowledge of its starting conditions and composition. Before these observations, scientists thought that all forms of matter and energy in the universe would only cause the expansion to slow down over time. Measurements of the cosmic microwave background (CMB) suggest the universe began in a hot Big Bang, from which general relativity explains its evolution and the subsequent large-scale motion. Without introducing a new form of energy, there was no way to explain how scientists could measure an accelerating universe. Since the 1990s, dark energy has been the most accepted premise to account for the accelerated expansion. As of 2021, there are active areas of cosmology research to understand the fundamental nature of dark energy.[3] Assuming that the lambda-CDM model of cosmology is correct,[4] as of 2013, the best current measurements indicate that dark energy contributes 68% of the total energy in the present-day observable universe. The mass–energy of dark matter and ordinary (baryonic) matter contributes 26% and 5%, respectively, and other components such as neutrinos and photons contribute a very small amount.[5][6][7][8] Dark energy's density is very low (~{\displaystyle 7\times 10^{-30}} g/cm3), much less than the density of ordinary matter or dark matter within galaxies. However, it dominates the universe's mass–energy content because it is uniform across space.[9][10][11]
Two proposed forms of dark energy are the cosmological constant[12][13] (representing a constant energy density filling space homogeneously) and scalar fields (dynamic quantities having energy densities that vary in time and space) such as quintessence or moduli. Contributions from scalar fields that are constant in space are usually also included in the cosmological constant. The cosmological constant can be formulated to be equivalent to the zero-point radiation of space, i.e., the vacuum energy.[14] However, scalar fields that change in space can be difficult to distinguish from a cosmological constant because the change may be prolonged.
Inflationary dark energy[edit]
Alan Guth and Alexei Starobinsky proposed in 1980 that a negative pressure field, similar in concept to dark energy, could drive cosmic inflation in the very early universe. Inflation postulates that some repulsive force, qualitatively similar to dark energy, resulted in an enormous and exponential expansion of the universe slightly after the Big Bang. Such expansion is an essential feature of most current models of the Big Bang. However, inflation must have occurred at a much higher energy density than the dark energy we observe today and is thought to have completely ended when the universe was just a fraction of a second old. It is unclear what relation, if any, exists between dark energy and inflation. Even after inflationary models became accepted, the cosmological constant was thought to be irrelevant to the current universe.
Nearly all inflation models predict that the total (matter+energy) density of the universe should be very close to the critical density. During the 1980s, most cosmological research focused on models with critical density in matter only, usually 95% cold dark matter (CDM) and 5% ordinary matter (baryons). These models were found to be successful at forming realistic galaxies and clusters, but some problems appeared in the late 1980s: in particular, the model required a value for the Hubble constant lower than preferred by observations, and the model under-predicted observations of large-scale galaxy clustering. These difficulties became stronger after the discovery of anisotropy in the CMB by the COBE spacecraft in 1992, and several modified CDM models came under active study through the mid-1990s: these included the Lambda-CDM model and a mixed cold/hot dark matter model. The first direct evidence for dark energy came from supernova observations in 1998 of accelerated expansion in Riess et al.[22] and in Perlmutter et al.,[23] and the Lambda-CDM model then became the leading model. Soon after, dark energy was supported by independent observations: in 2000, the BOOMERanG and Maxima CMB experiments observed the first acoustic peak in the CMB, showing that the total (matter+energy) density is close to 100% of critical density. Then in 2001, the 2dF Galaxy Redshift Survey gave strong evidence that the matter density is around 30% of critical. The large difference between these two supports a smooth component of dark energy making up the
DARK MATTER 27% of universe
In the 1930s, Fritz Zwicky, an astronomer researched thousands of galaxies and while he was studying some images, he made a surprising discovery.
The galaxies he studied were moving so fast that they should have distorted from each other into different directions but they didn’t. He concluded that some form of invisible dark matter held them together.
Scientifically, dark matter has never been physically detected as it simply does not absorb, reflect or emit light.
It is partially evident that dark matter provides the galaxies extra mass, which results in the induction of extra gravity. As a result, the galaxies stay intact.
While examining the Coma galaxy cluster in 1933, Zwicky was the first to use the virial theorem to discover the existence of a gravitational anomaly, which he termed dunkle Materie 'dark matter'.[3] The gravitational anomaly surfaced due to the excessive rotational velocity of luminous matter compared to the calculated gravitational attraction within the cluster. He calculated the gravitational mass of the galaxies within the cluster from the observed rotational velocities and obtained a value at least 400 times greater than expected from their luminosity. The same calculation today shows a smaller factor, based on greater values for the mass of luminous material; but it is still clear that the great majority of matter was correctly inferred to be dark.[21]
In the standard Lambda-CDM model of cosmology, the total mass-energy content of the universe contains 5% ordinary matter, 26.8% dark matter, and 68.2% of a form of energy known as dark energy.[6][7][8][9] Thus, dark matter constitutes 85%[a] of the total mass, while dark energy and dark matter constitute 95% of the total mass-energy content.[10][11][12][13]
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Dark matter is a form of invisible matter or mass whereas dark energy is a form of energy.
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Dark matter slows down the universe’s expansion whereas dark energy accelerates the expansion.
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Dark matter exists in space only whereas dark energy exists in both space and time.
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When compared to dark matter, dark energy is a far more dominating force in the universe.
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Dark matter is ideal for the co-existence of galaxies and the sustainability of the universe whereas dark energy is non-ideal.
Dark matter must exist to account for the gravity that holds galaxies together. If the only matter in the universe was matter we could directly detect, galaxies would not have had enough matter to have ever formed. The galaxies we observe today would fly apart because they wouldn't have enough matter to create a strong enough gravitational force to hold themselves together. Dark matter is also responsible for amplifying small fluctuations in the Cosmic Microwave Background back in the early universe to create the large scale structure we observe in the universe today.
Dark energy, which also goes by the names of the cosmological constant or quintessence, must exist due to the rate of expansion we observe for our universe. Not only is the universe expanding, but this expansion is also accelerating so the unknown 'anti-gravity' force at work is termed 'dark energy'.
Some researchers are searching for an explanation that encompasses both dark matter and dark energy. One example of such a theory uses a form of energy called a scalar field (it is a field because it has magnitude, energy and pressure, but it is scalar so it has no direction). Things would certainly be easier if we didn't need to have separate theories to explain dark matter and dark energy. However, other researchers look at dark matter and dark energy as two separate problems. For example, many string theories use supersymmetric particles to explain dark matter and make no connection to dark energy at all.
Greater mass out at the edge would allow the rotational velocity to be constant and therefore the spiral to be stable. Seems a remarkable coincidence.
Not enough mass to explain a number of things including gravitational lensing. Cosmic microwave background patterns, structure formation.
To solve galaxy rotation has be inverse of visible.
A new study theorizes that primordial black holes formed after the Big Bang (the far left panel) constitute all dark matter in the universe. At early epochs they cluster and seed the formation of early galaxies and then eventually grow by feeding off gas and merging with other black holes to create the supermassive black holes seen at the center of galaxies like our own Milky Way today. (Credit: Yale and ESA)
https://news.yale.edu/2021/12/16/black-holes-and-dark-matter-are-they-one-and-same
Seigar's group looked at images of 27 nearby spirals for which the mass of each central supermassive black hole is already known by other means. They noted that galaxies with the biggest black holes have tight spiral arms, emerging from the central bulge at angles of about 7°. But galaxies hosting smaller central black holes have looser spiral arms, with angles of up to 43° where the arms and the central bulge meet.
The next step is to expand this study to larger numbers and to look beyond the local region by examining galaxies at cosmological distances. Seigar expects that really remote galaxies, seen when the universe was significantly younger, contain smaller supermassive black holes than what we see in closer locales.
https://skyandtelescope.org/astronomy-news/black-holes-shape-spiral-galaxy-arms/
Our Milky Way galaxy has an elegant spiral shape with long arms filled with stars, but exactly how it took this form has long puzzled scientists. New observations of another galaxy are shedding light on how spiral-shaped galaxies like our own get their iconic shape.
Magnetic fields play a strong role in shaping these galaxies, according to research from the Stratospheric Observatory for Infrared Astronomy, or SOFIA. Scientists measured magnetic fields along the spiral arms of the galaxy called NGC 1068, or M77. The fields are shown as streamlines that closely follow the circling arms.
Magnetic fields in NGC 1068, or M77, are shown as streamlines over a visible light and X-ray composite image of the galaxy from the Hubble Space Telescope, the Nuclear Spectroscopic Array, and the Sloan Digital Sky Survey. The magnetic fields align along the entire length of the massive spiral arms — 24,000 light years across (0.8 kiloparsecs) — implying that the gravitational forces that created the galaxy’s shape are also compressing its magnetic field. This supports the leading theory of how the spiral arms are forced into their iconic shape known as “density wave theory.” SOFIA studied the galaxy using far-infrared light (89 microns) to reveal facets of its magnetic fields that previous observations using visible and radio telescopes could not detect.
Credits: NASA/SOFIA; NASA/JPL-Caltech/Roma Tre Univ.
“Magnetic fields are invisible, but they may influence the evolution of a galaxy,” said Enrique Lopez-Rodriguez, a Universities Space Research Association scientist at the SOFIA Science Center at NASA’s Ames Research Center in California’s Silicon Valley. “We have a pretty good understanding of how gravity affects galactic structures, but we’re just starting to learn the role magnetic fields play.”
The M77 galaxy is located 47 million light years away in the constellation Cetus. It has a supermassive active black hole at its center that is twice as massive as the black hole at the heart of our Milky Way galaxy. The swirling arms are filled with dust, gas and areas of intense star formation called starbursts.
SOFIA’s infrared observations reveal what human eyes cannot: magnetic fields that closely follow the newborn-star-filled spiral arms. This supports the leading theory of how these arms are forced into their iconic shape known as “density wave theory.” It states that dust, gas and stars in the arms are not fixed in place like blades on a fan. Instead, the material moves along the arms as gravity compresses it, like items on a conveyor belt.
The magnetic field alignment stretches across the entire length of the massive, arms — approximately 24,000 light years across. This implies that the gravitational forces that created the galaxy’s spiral shape are also compressing its magnetic field, supporting the density wave theory. The results are published in the Astrophysical Journal.
https://www.nasa.gov/feature/how-to-shape-a-spiral-galaxy
CONUNDRUM
Galaxy speeds up at the edges of the spiral, exactly offsets luminous mass
The universe speeds up as it gets further more dispersed.
The additional mass and energy hits critical density for a steady state universe.
Time to big bang 13.8 B years. I can see back 30 million years (9 Mag with a 80 mm aperture), professional ground based systems can see back 7 B years.
