Space and astronomy news
ESA’s Philae lander, the first spacecraft to successfully soft-land on the surface of a comet and former piggyback partner to Rosetta, has not been in communication since July of 2015 and, with 67P now six months past perihelion and heading deeper out into the Solar System, it’s not likely it will ever be heard from again.
Continue reading “Rosetta’s Philae Lander in Permanent Sleep”
One of the greatest things about being a space enthusiast is all of the discoveries that come out on an almost daily basis. One of the saddest things about being a space enthusiast is all of the discoveries and destinations that are so close, just beyond the horizon of our lifespan.
Will we colonize other planets? Sure, but most of us living will be gone by then. Will we spend time in glorious, gleaming space habitats? Obviously, but we’ll just be epitaphs by then. Sentient, alien species that gift us faster-than-light travel and other wonders? Maybe, but not before my bucket list has its final item checked off.
Citizen space travel? Hmmmm, tantalizingly within reach.
But now, new retro style posters from NASA, designed by the team at Invisible Creature, are making us feel nostalgic about things that haven’t even happened yet, and are helping us leave behind gloomy thoughts of being born at the wrong time.
The Grand Tour celebrates a time when our probes toured the planets, using gravity assist to propel them on their missions.
“Grandpa, do you remember the Grand Tour, when spacecraft used gravity assist to visit other worlds?”
“I sure do. Gravity assist. Those were the days. Swooping so close to Jupiter, you could feel the radiation killing your hair follicles. Only to be sling-shotted on to the next planet.”
“But why didn’t you just use a quantum drive to bend space time and appear at your destination?”
“Quantum drives! Those things ain’t natural. And neither is bending space-time. Give me a good old-fashioned chemical rocket any time.”
“Oh Grandpa.”
Visit the Historic Sites of Mars recalls a time when space pioneers colonized and terraformed Mars.
“Grandpa, what was Mars like in the Early Days?”
“You mean before it was terraformed? Very tough times.”
“Because conditions were so difficult? And food was hard to grow?”
“No. Because of the protesters.”
“Protesters? On Mars?”
“Yup. Every time we found a good spot for a Bacterial Production Facility (BPF), it seemed like there was an expired old rover in the way. The protesters didn’t think we should move ’em. Part of our heritage.”
“So what did you do Grandpa?”
“We created a network of computers that everybody would stare at all day. After that, nobody noticed what we did anymore.”
“Oh Grandpa.”
Visit Beautiful Southern Enceladus invites vacationers to visit Saturn’s sixth largest moon to view the ice geysers there.
“Grandpa, did you ever visit Enceladus?”
“I sure did. A beautiful, haunting place.”
“Was it scary? With all of the ice geysers erupting unpredictably?”
“On no. I always knew when one was going to erupt.”
“What? How did you know?”
“My arthritis would flare up.”
“Oh Grandpa.”
NASA has a growing collection of other posters. You can see them here.
SpaceX has their own posters, which you can see here. They also have cool t-shirts with the same designs.
I’ve always liked the idea that Jupiter has acted like a protector to its little brother, Earth. That it has used its massive gravitational pull to divert asteroids and comets from a collision course with Earth. Maybe Jupiter even felt bad when one got through, and doomed the dinosaurs to extinction. But a new study has cast this idea into doubt.
The idea of Jupiter as a protector has been around for a while. The images of comet Shoemaker-Levy 9 breaking apart and crashing into Jupiter in 1994 reinforced the idea. But according to Kevin Grazier, at the Jet Propulstion Laboratory (JPL), rather than acting solely as a shield, re-directing comets and other objects away from the inner solar system, Jupiter may have actually directed planetesimals into the inner solar system.
In the early days of the Solar System, there was much more debris around than there is now. The early days would have been a race between planetesimals to gather enough mass to form the planets we see today. After planets were formed, there would still have been plenty of planetesimals left. This new study shows that, rather than clearing the inner solar system from all this debris that could collide with Earth, Jupiter nudged many of these planetesimals towards Earth, helping to create Earth as we know it.
As reported in January 2016 in Astrobiology, Glazier created a simulator of the solar system, and ran 30,000 particles through this simulation. All of the particles began in “non life-threatening” trajectories, but a significant number of them ended the simulation in orbits that crossed the orbit of the Earth.
So not only did Jupiter—and Saturn—re-direct material into the inner Solar System, but the simulation also showed that Jupiter slowed that material to a speed which allowed it to contribute mass to Earth.
But these planetesimals would have contributed more than just mass to Earth. They would have carried volatiles with them. Volatiles are chemical elements and molecules with low boiling points. They are associated with the atmosphere and the crust. These volatiles, which include nitrogen, hydrogen, carbon dioxide, and others, make up a large portion of the Earth’s crust. Without them, Earth would be a very different place. It may never have developed the atmosphere that has allowed life to flourish.
It’s clear that Jupiter has contributed to the evolution of Earth and the Solar System as we know it. As the largest planet by far, its influence is undeniable. As a result of this study, we better understand the dual-role Jupiter has played. While it no doubt has played the role of protector, by changing the direction of some objects on a collision course with Earth, Jupiter’s presence has also been responsible for slowing and diverting planetesimals—and their life-friendly volatiles—directly into Earth.
If you try to apply simple common sense to how Saturn’s rings really work you’re going to be sorely mistaken: the giant planet’s signature features run circles around average Earthly intuition. This has been the case for centuries and is still true today after recent news from Cassini that the most opaque sections of rings aren’t necessarily the densest; with Saturn looks literally are deceiving.
Continue reading “Saturn’s Rings Continue to Surprise Scientists”
The Moon is the first object in space that fascinates we Earthlings. The Sun might be more prominent, but you can’t stare at the Sun without ocular damage. Anyone can gaze at the Moon, with or without binoculars or a telescope, and wonder where it came from and what it all means.
New evidence from a team at UCLA is clarifying the story of the Moon’s origins. According to this research, the Moon was formed as a result of a massive collision between Earth and a “planet embryo” about the size of Mars called Theia. This collision happened about 100 million years after the Earth was formed. Published on January 29th in the journal Science, this new geological evidence strengthens the case for the collision model.
The researchers compared Earth rocks with rocks retrieved from the Moon over the years. (Over 380kg of rocks have been brought back to Earth.) They found that these samples—collected on Apollo missions 12, 15, and 17—had the same chemical composition as seven rocks collected from Earth’s mantle, in Hawaii and Arizona. The key to the comparison lies in the nature of the oxygen atoms in the rocks.
Oxygen is a highly reactive element. It is easily combined with other elements, and is the most common element in the Earth’s crust. There are several different oxygen isotopes present in the Earth’s crust, and on other bodies in the solar system. The amount of each isotope present on each body is the “fingerprint” that makes the formation of each body different.
But the team at UCLA has shown that Earth and the Moon share the same cocktail of oxygen isotopes. They have the same fingerprint. This means that somehow, someway, their formation is linked. It can’t be pure coincidence. Says Edward Young, lead author of the new study, “We don’t see any difference between the Earth’s and the Moon’s oxygen isotopes; they’re indistinguishable.”
So how did this happen? How do Earth and the Moon share the same oxygen fingerprint? Enter Theia, an embryonic planet that got in the way of Earth’s orbit around the Sun. And as the research shows, this collision had to be more than a glancing blow. The collision had to be direct and cataclysmic.
This video shows how the collision would have played out.
A glancing blow would mean that the Moon would be mostly made of Theia, and would therefore have a different oxygen isotope fingerprint than Earth. But the fact that the Earth and Moon are indistinguishable from each other means that Theia had to have been destroyed, or rather, had to become part of both the Earth and the Moon.
“Theia was thoroughly mixed into the Earth and the Moon, and evenly dispersed between them. This explains why we don’t see a different signature of Theia in the Moon versus Earth,” said Young.
If this collision had not taken place, our Solar System would look very different, with an additional rocky planet in the inner regions. We also would have no Moon, which would have changed the evolution of life on Earth.
This collision theory, called the Theia Impact, or the Big Splash, has been around since 2012. But in 2014, a team of German researchers reported in Science that the Earth and Moon have different oxygen isotope ratios, which threw the collision formation theory into doubt. These new results confirm that it was a cataclysmic collision that gave birth to the Moon, and changed our Solar System forever.
Here on Earth, we to end to not give our measurements of time much thought. Unless we’re griping about Time Zones, enjoying the extra day of a Leap Year, or contemplating the rationality of Daylight Savings Time, we tend to take it all for granted. But when you consider the fact that increments like a year are entirely relative, dependent on a specific space and place, you begin to see how time really works.
Here on Earth, we consider a year to be 365 days. Unless of course it’s a Leap Year, which takes place every four years (in which it is 366). But the actual definition of a year is the time it takes our planet to complete a single orbit around the Sun. So if you were to put yourself in another frame of reference – say, another planet – a year would work out to something else. Let’s see just how long a year is on the other planets, shall we?
Continue reading “The Orbit of the Planets. How Long Is A Year On The Other Planets?”
The Royal Astronomical Society (RSA) has announced the discovery of a planet that orbits its star at a distance of 1 trillion kilometres. This is easily the furthest distance between a star and a planet ever found. For comparison, that’s 7,000 times further than the Earth is from the Sun. At that distance, a single orbit takes about 900,000 years, meaning that the planet has orbited its star less than 50 times.
Continue reading “Lonely But Not Alone: A Planet Orbits its Star at 1 Trillion Kilometres”
The astronomer known worldwide for vigorously promoting the demotion of Pluto from its decades long perch as the 9th Planet, has now found theoretical evidence for a new and very distant gas giant planet lurking way beyond Pluto out to the far reaches of our solar system.
In an obvious reference to the planethood controversy, the proposed new planet is nicknamed ‘Planet Nine’ and its absolutely huge! Continue reading “Astronomers Find Theoretical Evidence for Distant Gas Giant Planet in Our Solar System”
During the many thousand years that human beings have been looking up at the stars, our concept of what the Universe looks like has changed dramatically. At one time, the magi and sages of the world believed that the Universe consisted of a flat Earth (or a square one, a zigarrut, etc.) surrounded by the Sun, the Moon, and the stars. Over time, ancient astronomers became aware that some stars did not move like the rest, and began to understand that these too were planets.
In time, we also began to understand that the Earth was indeed round, and came up with rationalized explanations for the behavior of other celestial bodies. And by classical antiquity, scientists had formulated ideas on how the motion of the planets occurred, and how all the heavenly orbs fit together. This gave rise to the Geocentric model of the universe, a now-defunct model that explained how the Sun, Moon, and firmament circled around our planet.
Continue reading “What Is The Geocentric Model Of The Universe?”
The Scientific Revolution, which took place in the 16th and 17th centuries, was a time of unprecedented learning and discovery. During this period, the foundations of modern science were laid, thanks to breakthroughs in the fields of physics, mathematics, chemistry, biology, and astronomy. And when it comes to astronomy, the most influential scholar was definitely Nicolaus Copernicus, the man credited with the creation of the Heliocentric model of the Universe.
Based on ongoing observations of the motions of the planets, as well as previous theories from classical antiquity and the Islamic World, Copernicus’ proposed a model of the Universe where the Earth, the planets and the stars all revolved around the Sun. In so doing, he resolved the mathematical problems and inconsistencies arising out of the classic geocentric model and laid the foundations for modern astronomy.
While Copernicus was not the first to propose a model of the Solar System in which the Earth and planets revolved around the Sun, his model of a heliocentric universe was both novel and timely. For one, it came at a time when European astronomers were struggling to resolve the mathematical and observational problems that arose out of the then-accepted Ptolemaic model of the Universe, a geocentric model proposed in the 2nd century CE.
In addition, Copernicus’ model was the first astronomical system that offered a complete and detailed account of how the Universe worked. Not only did his model resolves issues arising out of the Ptolemaic system, it offered a simplified view of the universe that did away with complicated mathematical devices that were needed for the geocentric model to work. And with time, the model gained influential proponents who contributed to it becoming the accepted convention of astronomy.
The geocentric model, in which planet Earth is the center of the Universe and is circled by the Sun and all the planets, had been the accepted cosmological model since ancient times. By late antiquity, this model had come to be formalized by ancient Greek and Roman astronomers, such as Aristotle (384 – 322 BCE) – who’s theories on physics became the basis for the motion of the planets – and Ptolemy (ca. 100 – ca.?170 CE), who proposed the mathematical solutions.
The geocentric model essentially came down to two common observations. First of all, to ancient astronomers, the stars, the Sun, and the planets appeared to revolve around the Earth on daily basis. Second, from the perspective of the Earth-bound observer, the Earth did not appear to move, making it a fixed point in space.
The belief that the Earth was spherical, which became an accepted fact by the 3rd century BCE, was incorporated into this system. As such, by the time of Aristotle, the geocentric model of the universe became one where the Earth, Sun and all the planets were spheres, and where the Sun, planets and stars all moved in perfect circular motions.
However, it was not until Egyptian-Greek astronomer Claudius Ptolemaeus (aka. Ptolemy) released his treatise Almagest in the 2nd century BCE that the details became standardized. Drawing on centuries of astronomical traditions, ranging from Babylonian to modern times, Ptolemy argued that the Earth was in the center of the universe and the stars were all at a modest distance from the center of the universe.
Each planet in this system is also moved by a system of two spheres – a deferent and an epicycle. The deferent is a circle whose center point is removed from the Earth, which was used to account for the differences in the lengths of the seasons. The epicycle is embedded in the deferent sphere, acting as a sort of “wheel within a wheel”. The purpose of he epicycle was to account for retrograde motion, where planets in the sky appear to be slowing down, moving backwards, and then moving forward again.
Unfortunately, these explanations did not account for all the observed behaviors of the planets. Most noticeably, the size of a planet’s retrograde loop (especially Mars) were sometimes smaller, and larger, than expected. To alleviate the problem, Ptolemy developed the equant – a geometrical tool located near the center of a planet’s orbit that causes it to move at a uniform angular speed.
To an observer standing at this point, a planet’s epicycle would always appear to move at uniform speed, whereas it would appear to be moving at non-uniform speed from all other locations.While this system remained the accepted cosmological model within the Roman, Medieval European and Islamic worlds for over a thousand years, it was unwieldy by modern standards.
However, it did manage to predict planetary motions with a fair degree of accuracy, and was used to prepare astrological and astronomical charts for the next 1500 years. By the 16th century, this model was gradually superseded by the heliocentric model of the universe, as espoused by Copernicus, and then Galileo and Kepler.
In the 16th century, Nicolaus Copernicus began devising his version of the heliocentric model. Like others before him, Copernicus built on the work of Greek astronomer Atistarchus, as well as paying homage to the Maragha school and several notable philosophers from the Islamic world (see below). By the early 16th century, Copernicus summarized his ideas in a short treatise titled Commentariolus (“Little Commentary”).
By 1514, Copernicus began circulating copies amongst his friends, many of whom were fellow astronomers and scholars. This forty-page manuscript described his ideas about the heliocentric hypothesis, which was based on seven general principles. These principles stated that:
Thereafter he continued gathering data for a more detailed work, and by 1532, he had come close to completing the manuscript of his magnum opus – De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres). In it, he advanced his seven major arguments, but in more detailed form and with detailed computations to back them up.
By placing the orbits of Mercury and Venus between the Earth and the Sun, Copernicus was able to account for changes in their appearances. In short, when they are on the far side of the Sun, relative to Earth, they appear smaller but full. When they are on the same side of the Sun as the Earth, they appear larger and “horned” (crescent-shaped).
It also explained the retrograde motion of planets like Mars and Jupiter by showing that Earth astronomers do not have a fixed frame of reference but a moving one. This further explained how Mars and Jupiter could appear significantly larger at certain times than at others. In essence, they are significantly closer to Earth when at opposition than when they are at conjunction.
However, due to fears that the publication of his theories would lead to condemnation from the church (as well as, perhaps, worries that his theory presented some scientific flaws) he withheld his research until a year before he died. It was only in 1542, when he was near death, that he sent his treatise to Nuremberg to be published.
As already noted, Copernicus was not the first to advocate a heliocentric view of the Universe, and his model was based on the work of several previous astronomers. The first recorded examples of this are traced to classical antiquity, when Aristarchus of Samos (ca. 310 – 230 BCE) published writings that contained references which were cited by his contemporaries (such as Archimedes).
In his treatise The Sand Reckoner, Archimedes described another work by Aristarchus in which he advanced an alternative hypothesis of the heliocentric model. As he explained:
Now you are aware that ‘universe’ is the name given by most astronomers to the sphere whose center is the center of the earth and whose radius is equal to the straight line between the center of the sun and the center of the earth. This is the common account… as you have heard from astronomers. But Aristarchus of Samos brought out a book consisting of some hypotheses, in which the premises lead to the result that the universe is many times greater than that now so called. His hypotheses are that the fixed stars and the sun remain unmoved, that the earth revolves about the sun in the circumference of a circle, the sun lying in the middle of the orbit, and that the sphere of the fixed stars, situated about the same center as the sun, is so great that the circle in which he supposes the earth to revolve bears such a proportion to the distance of the fixed stars as the center of the sphere bears to its surface.
This gave rise to the notion that there should be an observable parallax with the “fixed stars” (i.e an observed movement of the stars relative to each other as the Earth moved around the Sun). According to Archimedes, Aristarchus claimed that the stars were much farther away than commonly believed, and this was the reason for no discernible parallax.
The only other philosopher from antiquity who’s writings on heliocentrism have survived is Seleucis of Seleucia (ca. 190 – 150 BCE). A Hellenistic astronomer who lived in the Near-Eastern Seleucid empire, Seleucus was a proponent of the heliocentric system of Aristarchus, and is said to have proved the heliocentric theory.
According to contemporary sources, Seleucus may have done this by determining the constants of the geocentric model and applying them to a heliocentric theory, as well as computing planetary positions (possibly using trigonometric methods). Alternatively, his explanation may have involved the phenomenon of tides, which he supposedly theorized to be related to the influence of the Moon and the revolution of the Earth around the Earth-Moon ‘center of mass’.
In the 5th century CE, Roman philosopher Martianus Capella of Carthage expressed an opinion that the planets Venus and Mercury revolved around the Sun, as a way of explaining the discrepancies in their appearances. Capella’s model was discussed in the Early Middle Ages by various anonymous 9th-century commentators, and Copernicus mentions him as an influence on his own work.
During the Late Middle Ages, Bishop Nicole Oresme (ca. 1320-1325 to 1382 CE) discussed the possibility that the Earth rotated on its axis. In his 1440 treatise De Docta Ignorantia (On Learned Ignorance) Cardinal Nicholas of Cusa (1401 – 1464 CE) asked whether there was any reason to assert that the Sun (or any other point) was the center of the universe.
Indian astronomers and cosmologists also hinted at the possibility of a heliocentric universe during late antiquity and the Middle Ages. In 499 CE, Indian astronomer Aaryabhata published his magnum opus Aryabhatiya, in which he proposed a model where the Earth was spinning on its axis and the periods of the planets were given with respect to the Sun. He also accurately calculated the periods of the planets, times of the solar and lunar eclipses, and the motion of the Moon.
In the 15th century, Nilakantha Somayaji published the Aryabhatiyabhasya, which was a commentary on Aryabhata’s Aryabhatiya. In it, he developed a computational system for a partially heliocentric planetary model, in which the planets orbit the Sun, which in turn orbits the Earth. In the Tantrasangraha (1500), he revised the mathematics of his planetary system further and incorporated the Earth’s rotation on its axis.
Also, the heliocentric model of the universe had proponents in the medieval Islamic world, many of whom would go on to inspire Copernicus. Prior to the 10th century, the Ptolemaic model of the universe was the accepted standard to astronomers in the West and Central Asia. However, in time, manuscripts began to appear that questioned several of its precepts.
For instance, the 10th-century Iranian astronomer Abu Sa’id al-Sijzi contradicted the Ptolemaic model by asserting that the Earth revolved on its axis, thus explaining the apparent diurnal cycle and the rotation of the stars relative to Earth. In the early 11th century, Egyptian-Arab astronomer Alhazen wrote a critique entitled Doubts on Ptolemy (ca. 1028) in which he criticized many aspects of his model.
Around the same time, Iranian philosopher Abu Rayhan Biruni 973 – 1048) discussed the possibility of Earth rotating about its own axis and around the Sun – though he considered this a philosophical issue and not a mathematical one. At the Maragha and the Ulugh Beg (aka. Samarkand) Observatory, the Earth’s rotation was discussed by several generations of astronomers between the 13th and 15th centuries, and many of the arguments and evidence put forward resembled those used by Copernicus.
Despite his fears about his arguments producing scorn and controversy, the publication of Copernicu’s theories resulted in only mild condemnation from religious authorities. Over time, many religious scholars tried to argue against his model. But within a few generation’s time, Copernicus’ theory became more widespread and accepted, and gained many influential defenders in the meantime.
These included Galileo Galilei (1564-1642), who’s investigations of the heavens using the telescope allowed him to resolve what were seen as flaws in the heliocentric model, as well as discovering aspects about the heavens that supported heliocentrism. For example, Galileo discovered moons orbiting Jupiter, Sunspots, and the imperfections on the Moon’s surface – all of which helped to undermine the notion that the planets were perfect orbs, rather than planets similar to Earth. While Galileo’s advocacy of Copernicus’ theories resulted in his house arrest, others soon followed.
German mathematician and astronomer Johannes Kepler (1571-1630) also helped to refine the heliocentric model with his introduction of elliptical orbits. Prior to this, the heliocentric model still made use of circular orbits, which did not explain why planets orbited the Sun at different speeds at different times. By showing how the planet’s sped up while at certain points in their orbits, and slowed down in others, Kepler resolved this.
In addition, Copernicus’ theory about the Earth being capable of motion would go on to inspire a rethinking of the entire field of physics. Whereas previous ideas of motion depended on an outside force to instigate and maintain it (i.e. wind pushing a sail) Copernicus’ theories helped to inspire the concepts of gravity and inertia. These ideas would be articulated by Sir Isaac Newton, who’s Principia formed the basis of modern physics and astronomy.
Although its progress was slow, the heliocentric model eventually replaced the geocentric model. In the end, the impact of its introduction was nothing short of a revolutionary. Henceforth, humanity’s understanding of the universe and our place in it would be forever changed.
We have written many interesting articles on the heliocentric model here at Universe Today. For starters, here’s Galileo Returns to the Vatican and The Earth Goes Around the Sun, Who Was Nicolaus Copernicus? and What is the Difference Between the Geocentric and Heliocentric Models?
For more information on heliocentrism, take a look at these articles from NASA on Copernicus or the center of the galaxy.
Astronomy Cast also has an episode on the subject, titled Episode 77: Where is the Center of the Universe and Episode 302: Planetary Motion in the Sky.