Stars as in Astro

Stars As In Astro

Stars have captivated human attention since times immemorial; popular media phenomena Star Wars and cult-inspiring Star Trek are just two among many proofs.

Our solar system is part of the Milky Way Galaxy, one star (the Sun) among billions of stars, among billions of galaxies. The closest spiral galaxy to us is Andromeda; the two are expected to collide in billions of years to form a mega-galaxy, as is often the case elsewhere.

The Sun is young; a middle aged star turns into a red giant, and a dying star becomes a white dwarf (extremely dense). After one tries to ponder just how enormous a star like Vy CM is, one goes further by contemplating that of these stellar masses there are trillions. Still, all these stars, planets, comets, gas and other floating materials in the universe comprise only 4.9% of its totality, ¾ of the universe being dark energy (human comprehension largely pending), and the rest dark matter.

Space travel trough distant starfield - artist's impression. Random darkness. Our solar system is part of the Milky Way Galaxy, one star (the Sun) among billions of stars, among billions of galaxies… (Illustration: Elena - Megan Jorgensen)

In the scientific realm, there are astronomy, astrobiology, astrochemistry and astrophysics.

Due to the impossibility to place a massive gaseous object into empty space and watch it evolve for a million years, astrophysics and astronomy are observational and not experimental sciences. Although physics is indeed a science, debates nonetheless remain. For example, Pluto has recently (circa 2008) lost its planetary status, due to the many “Plutos” in similar elliptical outer orbits. Eris, a planet larger than Pluto, has been discovered and it is expected that similar others will follow in the near future (the Hubble telescopes and the Voyager probes launched in the 1970s have advanced the field tremendously). Similarly, the Moon, essentially a rock, is larger than Pluto and due to the unusual, as compared to other planets, Earth-Satellite proportion, they could be considered as two planets.

Finally, black holes are so dense that even light cannot escape them, which is why we fail to see them since we only perceive objects as photons get reflected from them. A black hole escape velocity is greater than the speed of light; therefore even light gets trapped inside once it reaches the event horizon (the point of no return). Maybe with a telescope from Naturaliste à Québec, the next black hole will be discovered from the province…

Further, astrology is the practice of attempting to foretell the future based on the position of the stars, as in the twelve horoscope signs that stem from the belief that a person born under a particular stellar arrangement has a predetermined destiny and personality.

Stars Are Born in Batches

Stars Are Born in Batches

Where do the naturally occurring elements come from? Our universe, all of it, almost everywhere, is 99 percent hydrogen and helium, the two simplest elements. Helium, in fact, was detected by the Earthlings on the Sun before it was found on the Earth – hence its name (from Helios, one of the Greek sun gods).

But the Earth is an exception, because primordial hydrogen, only weakly bound by this planet’s comparatively feeble gravitation attraction, has by now largely escaped to space. Jupiter, with its more massive gravity, has retained at least much of its original complement of the lightest element.

Might the other chemical elements have somehow evolved from hydrogen and helium? The answer is “may be”. In fact, to balance the electrical repulsion, pieces of nuclear matter would have to be brought very close together so that the short range nuclear forces are engaged. This can happen only at very high temperatures where the particles are moving so fast that the repulsive force does not have time to act (temperatures of tens of millions of degrees).

Well, as in the families of humans, the maturing stars journey far from home, and the siblings see little of each other. Somewhere in the Milky Way Galaxy there are dozens of stars that are the brothers and sisters of the Sun, formed from the some cloud complex, some 5 billion years ago. Most of them, for all we know, are on the other side of the Milky Way. Illustration: Elena

In nature, such high temperatures and attendant high pressures are common only in the insides of the stars.

Thus stars like the Sun are born in batches, in great compressed cloud complexes such as the Orion Nebula. Seen from the outside, such clouds may seem dark and gloomy. But inside, they are brilliantly illuminated by the hot newborns stars which grow older and wander out of their nursery to seek their fortunes in the Milky Was, stellar adolescents still surrounded by tufts of glowing nebulosity, residues still gravitationaly attached of their amniotic gas.

Let’s evoke a nice example: In the direction of the star Deneb, in the constellation of Cygnus the Swan, is an enormous gloving super-bubble of extremely hot gas, produced by supernova explosions, the death of stars, near the center of the bubble. At the periphery, interstellar matter is compressed by the supernova shock wave, triggering new generations of cloud collapse and star formation. In this sense, stars have parents; and, as is sometimes also true for intelligent creatures, a parent may die in the birth of the child. The Pleiades are another example.

When Stars Raise from the Ashes

When Stars Raise From the Ashes

The end of a life cycle of a star, its fate, depends very much on its initial mass, as hydrogen fusion cannot continue forever and in any star there is a limited hydrogen fuel in its hot interior.

The Sun’s fate is spectacular. When the hydrogen has all reacted to form helium, five or six billion years from now, the zone of hydrogen fusion will migrate outward in continuous thermonuclear reactions, until it reaches the place where the temperatures are less than about ten million degrees.

The hydrogen fusion will shut itself off then. Meanwhile the self -gravity of the Sun will force a renewed contraction of its helium-rich core and a further increase in its interior temperatures and pressures.

Ocean Turquoise. A star is a phoenix destined to rise for a time from its own ashes. But solar evolution is inexorable. Billions of years from now, there will be a last perfect day on Earth. Image: © Elena

The helium nuclei will thus be jammed together still more tightly, so much so that they begin to stick together, the hooks of their short-range nuclear forces becoming engaged despite the mutual electrical repulsion. The ash will become fuel, and the Sun will be triggered into a second round of fusion reactions.

This long process will generate the elements carbon and oxygen and provide additional energy for the Sun to continue shining.

Then, under the combined influence of hydrogen fusion in a thin shell far from the solar interior and the high temperature helium fusion in the core, the Sun will undergo a major change: its exterior will expand and cool. The Sun will become a red giant star, its visible surface so far from its interior that the gravity at its surface grows feeble, its atmosphere expanding into space in a kind of stellar gale. When the Sun, ruddy and bloated, becomes a red giant, it will envelop and devour the planets Mercury and Venus – and probably the Earth as well. The inner solar system will then reside within the Sun.

A star is a phoenix, destined to rise for a time from its own ashes. But stars as Sun may arise once or may be two times before the use all their fuel, their energy.

If, after whatever matter it has lost to space, a star retains two or three times the mass of our Sun, it ends its life cycle in a startlingly different mode than the Sun will. Indeed, stars more massive than the Sun achieve higher central temperatures and pressures to their late evolutionary stages. They are able to rise a dozen times from their ashes, using oxygen and carbon as fuel for synthesizing still heavier elements…

Billions of years from now, there will be a last perfect day on Earth. Thereafter the Sun will slowly become red and distended, presiding over an Earth sweltering even at the poles. The Arctic and Antarctic icecaps will melt, flooding the coasts of the world. The high oceanic temperatures will release more water vapor into the air, increasing cloudiness, shielding the Earth from sunlight and delaying the end a little. But solar evolution is inexorable. Eventually the oceans will boil, the atmosphere will evaporate away to space and a catastrophe of the most immense proportions imaginable will overtake the Earth. And the end will come.

Apollo: 240,000 Miles to the Moon and Back

Apollo: 240,000 Miles to the Moon and Back

On July 16, 1969, the five F-1 engines on the mighty Saturn V ignited for their most critical test of all: generating one and one-half million pounds of thrust each, they launched three Apollo astronauts into the first leg of their journey toward the moon. After the first and second stages were exhausted and jettisoned, the third stage took over, adding just enough speed to achieve Earth orbit. During this “parking” orbit, the astronauts checked out all systems to determine that they were operating correctly. Then, when the “launch window” (best period of time to begin the translunar flight) was opened, the third stage fired again, increasing the speed to escape earth orbit and began the trajectory toward the Moon.

On the way to the Moon, the Command Module (CM) containing the three astronauts, together with the Service Module (SM) containing the electrical power supply equipment and the SM propulsion system, separated from the third stage of the Saturn V, turned 180 degrees in space, and docked nose-to-nose with the Lunar Module (LM), which was contained in the top of the third stage. The combined Command-Service Modules (CSM) and LM then separated from the third stage and continued toward the Moon.

Earth-rise as seen from the Moon, Apollo 8, bearing astronauts Borman, Lovell and Anders, orbited the Moon on Christams Eve, 1968, and returned with this now-famous photo of the Earth as first seen by man from outer space

Approaching the Moon at a speed of about 5200 mph, the astronauts fired the SM rocket engine to slow the spacecraft to about 3600 mph, allowing it to swing into orbit approximately 80 miles above the lunar surface. Transferring to the LM, two astronauts fired TRW’s LM Descent Engine to achieve a transfer orbit (an orbit which intersected the Moon), while the CSM remained in lunar orbit. At an altitude of about 50, 000 feet, the LM Descent Engine fired again, braking the velocity to zero at about 200 feet above the lunar surface. At this point, the astronauts used the Descent Engine together with the control jets on the LM, moving horizontally as necessary, then descended to the selected landing spot.

During their stay on the Moon, the astronauts transmitted direct telecasts and radio descriptions, took photographs, and collected rock samples to bring home in vacuum-sealed containers. In addition, they set up a group of lunar surface experiments, which continued to radio information to Earth for as long as a year. These experiments reported on such phenomena as temperature changes, radiation levels, moonquakes, and micrometeoroids (tiny particles of matter in space).

To begin their return flight, the two astronauts fired the Ascent Engine to rejoin the still-orbiting CSM containing the third astronaut. The lower stage of the LM, having done its job, was used as a launch platform for the upper stage and was left behind on the Moon. Achieving the proper orbit at the proper time, the LM docked with the CSM. The two astronauts transferred to the CSM, and the LM was jettisoned and left in lunar orbit. The SM rocket engine ignited once more to build up lunar escape velocity, of about 5460 mph. Beyond 29,000 miles from the Moon, the Earth’s gravitational pool became dominant, increasing the return speed to about 25,000 mph – the same velocity at which the crew left Earth just eight days before.

After using the SM rocket engine for final course corrections the astronauts jettisoned the SM, and the CM plunged toward the Earth.

The re-entry corridor of correct flight path into Earth’s atmosphere represented one of many phases during the mission when the functioning of men and machines had to be extremely precise – when tolerances were very close, and performing within them could have been a matter of life and death.  Only 40 miles wide, this extremely critical path had to be kept at an angle of 5 ½ degrees to 7 ½ degrees to the Earth horizontal. It the angle was too steep (over 7 ½), re-entry would have been too rapid, and the “g-loads” from hidden deceleration would have exceeded the human limitations of the astronauts inside. If it were not steep enough (under 5 ½ degrees), the CM would skip off the outer surface of the atmosphere like a stone skipping across water and out into Earth orbit.  If that had happened, the astronauts would have been trapped in orbit, with no means of ever getting back.

But the correct path was maintained, the three astronauts re-entered Earth’s atmosphere at about 25,000 miles per hour, with the CM heatshield reaching temperatures at around 5, 000 degrees F, and air resistance rapidly cut the velocity to s safe point for parachute deployment and landing in the South Pacific.

The thrilling climax to the Apollo program, when the astronauts actually made their trip to the Moon, was followed closely by everyone. But like the peak of an iceberg protruding above the water, their launch and safe return were only the visible portion of a program so massive as so complex as to rank among the largest efforts ever undertaken by men. Few of those who witnessed the launch will be able to comprehend the magnitude of preparation, or the number of calculations, trials, failures, and recalculations which preceded the flight.

For example, long before the Saturn V blasted off from Cape Kennedy (Cape Canaveral), it had flown its mission many times under simulated conditions in a TRW computer.  Working from data collected during ground tests, the TRW developed computer models of the Apollo propulsion systems. These models, which were updated and refined as flight data were obtained, have been used to plan Apollo missions and to analyze their results.

The great heat to which the Apollo spacecraft was exposed during ascent and re-entry through Earth’s atmosphere made it necessary to scrutinize very carefully its structure as well as its materials and coatings of the spacecraft for thermal stability, and the internal structure for thermally-induced stress.

A successful lunar landing required the LM landing radar to provide extremely accurate readings of the craft’s altitude, attitude, and speed of approach. The experts provided a comprehensive evaluation of this subsystem through computer simulation.

Fuel, oxygen, hydrogen, electrical energy and water were consumed during the lunar flights. These consumables had to be carefully budgeted to allow margins of safety without unduly increasing spacecraft weight. Scientist prepared consumable budgets and integrated them into preliminary flight plans.

In addition to these systems analysis tasks, scientists and engineers computed launch trajectories and reference mission trajectories; performed ranch safety analysis; short analysis and post-flight trajectory analysis; and provided re-entry mission planning support.

These are only a few of the more than 130 analytical tasks the team performed for Apollo, covering almost every aspect of the various Apollo missions.

A network of tracking stations around the world was established by Project Mercury, augmented for Gemini, and redesigned and expended for Apollo. One group of network stations followed the Apollo spacecraft at launch and during Earth orbit, and again at the end of the flight after the Moon trip was finished. When the spacecraft left the Earth orbit and passed out of range of these stations, tracking them switched to a second group of stations, containing powerful transmitters and sensitive receivers which were dependable for communications at great distances.

To test this vast network and to help train the personnel who operated the stations comprising it, TRW produced two test and training satellites from its ERS series of spacecraft.  Primarily, an orbiting transponder (combination receiver/transmitter capable of increasing the energy level of the received signal and retransmitting it on a different frequency), these satellites were used by NASA to check the Manned Space Flight Network, much as an orchestra conductor sounds each instrument prior to a concert.

44-pound stowaway: Barely noticed as it piggy-backed a ride on the Thrust Augmented Delta rocket that sent TRW`s Pioneer 8 into orbit around the Sun, the TRW-built Test and Training satellite was injected into a low earth orbit. It was used to train communication personnel and check out the equipment of NASA`s Apollo tracking network. A similar spacecraft accompanied Pioneer 9.

The Test and Training satellites belong to the family of TRW Environmental Research Satellites, an entire series of small spacecraft designed specifically for economical “piggyback” launches with larger payloads. A low-coast, reliable, quickly-assembled unit, the ERS may range in weight from 1,5 to 45 pounds. Source de l’image: astronautix.com

In 18 of these world-wide ground locations, as well as in a number of shipboard stations, TRW provided communication units known as Signal Data Demodulator Systems. Whether the astronauts were on the launch pad waiting for blast-off or whether they were on the surface of the Moon, these units relayed astronaut biochemical data (temperature, pulse, etc.), as well as video and voice communications, and – if these had failed – even simple radio telegraph key signals.

Saturn V – The Apollo Moon Rocket. Poised on its launch pad at Kennedy Space Center is a Saturn V rocket like the one which carried three astronauts to the Moon. The Saturn V stands over 363 feet high. It developed over 7, 5 million pounds of thrust at liftoff. Photo in public domain

A highly reliable guidance system in the LM guided the astronauts from the CM to the Moon’s surface and back. This extremely critical system helped the astronauts maintain the correct LM altitude and course for a safe landing in the target area. During the ascent stage, it helped them in the ticklish job of launching into the precise orbit for rendezvous and docking with the CM. These tasks, seemingly simple in themselves, required precise and rapid determination of vehicle position, attitude, velocity, and course, as well as solution of complex guidance and navigation formulas.

Because these were such crucial tasks, the LM was equipped with a backup guidance system which operated in parallel with the primary system. This backup system is known as the LM Abort Guidance System, and would have allowed the astronauts to safely take over direct control of the lunar mission in the event of a primary guidance malfunction.

The LM/AGS is a strapdown inertial guidance system which uses the technique of strapping the inertial instruments required for sensing attitude and velocity to the vehicle. Conventional inertial guidance techniques require the mounting of the gyros and accelerometers on a stable platform. Eliminating this platform reduces the number of moving or electromechanical parts, thereby decreasing the size, weight, and power consumption of the subsystem as compared with a conventional inertial platform.

A Closeup Look At Mars

A Closeup Look At Mars

After centuries of questions about the possibility of life on Mars, one of two spacecraft designed to provide some answers on that subject landed on the surface or the Red Planet in August, 1976. Viking Lander 1 settled to the surface of the western slope of Chryse Planitia. Viking Lander 2 touched down on Utopia Planitia about six weeks later, on September 3, 1976.

The Viking project was the culmination of the first phase of the United States’s Mars exploration effort. During the 1960s and early 70s three Mariner spacecraft snapped photographs as they zipped past Mars; a fourth mapped the planet’s surface in detail during a year in orbit.

Mars, photograph in public domain

Viking, however, greatly expanded on the accomplishments of the Mariner probes. The Viking project consisted of the flotilla of ships – two landers and two orbiters. While the orbiters photographed the entire planet, the landers measured weather conditions, listened for Marsquakes, and obtained the first photographs from the Martian surface.

One of the primary Viking objectives was to search for life. Each lander carried biology experiments to scan the soil for microscopic life and search for evidence of metabolic processes similar of those of earthly organisms. The experiments did, in fact, produce results that could be interpreted as signs of life. But scientists later determined that the findings were caused by unusual properties of the Martian soil, not biological processes.

Nevertheless, Viking was a rousing success. The orbiters beamed more than 51,000 photographs to Earth and the landers added 4,500 more. All four spacecraft performed long past their planned operating lifetimes, with Viking Lander 1 continuing to transmit vital data until November 1982.