• Sunspots are spots darker than the surrounding area on the Sun’s photosphere caused by concentration of magnetic flux field. Their number varies in an approximately 11-year cycle.
• Solar flares are sudden flashes of light on the Sun, usually observed on the surface and close to a sunspot group. They are caused by the interaction between accelerated charges particles and the plasma medium.
• Coronal mass ejections (CMEs) are significant releases of plasma caused by magnetic reconnection. They often accompany powerful solar flares. On July 19, 2012, an eruption occurred on the Sun produced a solar flare, followed with a CME, then a coronal rain. In the video at the beginning of the article, each second corresponds to 6 minutes of real time.
• Solar Winds are streams of charged particles released from the corona.
Effects on Earth
How Solar Winds Impact the Earth’s Magnetosphere (from: NASA)
• Earth’s weather and global climate change can be affected by solar activities. Auroras are indicators of the connection between the Sun and the Earth.
• Solar activities also affect GPS, satellites and other high-tech systems. For example, a solar radiation storm can cause noise in imaging systems and permanent damage to exposed detectors on satellites.
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20 new protoplanetary disks, as imaged by the Disk Substructures at High Angular Resolution Project (DSHARP) collaboration, showcasing what newly-forming planetary systems look like. (S. M. ANDREWS ET AL. AND THE DSHARP COLLABORATION, ARXIV:1812.04040)
Found on Dr. Ethan Sharp’s Starts With A Bang blog
I’d love to show you a whole bunch of videos that show planetary formation! Some showcase certain parts of formation better than others but they all are pretty awesome.
Planetary Formation – by NASA for the James Webb Space Telescope, uses data from computer models (3:21)
Planet Formation – narration by Harrison Ford, I like that it has some timescale information in it, part of a larger series (3:13)
Short animation from the NASA Deep Impact spacecraft – it especially shows comet formation but watch for: a) gravitational forces bringing smaller things to bigger things in orbits (bound and unbound), and b) those conglomerating rocks/metals getting a layer of ices (0:55)
Two renderings (i.e. computer simulations) of protoplanetary disk gravitational instabilities (i.e. planet formation), one is face on (0:44) and one is an oblique angle (0:44)
The California Academy of Sciences has a really nice former planetarium show segment about Simulating Solar System Formation (and it explains why the Kuiper Belt (and Oort Cloud) look the way they do) (4:22)
blocked on copyright grounds From “Space with Sam Neill” Episode: “Star Stuff”, I really like how this one is done (I started it at 1:27) – here
The “Formation of the Moon” video that I commented does happen to be one of my favorites despite the speeding up of some events that they did (3:37)
More Moon formation – this is from a supercomputer simulation and it has the weirdest music! It’s also a bit old and you don’t need to watch until the end… (4:05)
Below is an image of the Orion Nebula (we can see it during our observations this semester ;) ) from the Hubble Space Telescope showing some of the protoplanetary disks that have been found in this nebula. Look!!! New baby planetary systems! :)
A collection of 30 never-before-released images of embryonic planetary systems in the Orion Nebula are the highlight of the longest single Hubble Space Telescope project ever dedicated to the topic of star and planet formation. Also known as proplyds, or protoplanetary discs, these modest blobs surrounding baby stars are shedding light on the mechanism behind planet formation. (from 2009) https://www.spacetelescope.org/news/heic0917/
An aerial view of Newgrange, the “roof-box” above the main entrance, and light streaming in through the roofbox, Newgange.com
Newgrange is a monument located in County Meath, Ireland. This mysterious structure is estimated to be over 5,000 years old and was built by ancient inhabitants of Ireland during the Neolithic period. Since its construction, word of the structure was passed down through generations as part of Irish folklore. In the meantime, the mound-like shape of Newgrange became obscured by overgrowth of vegetation and shifting soil. But in the 1960s, archaeologists unearthed the whole of the structure and carried out a detailed excavation. This excavation confirmed that Newgrange was a passage tomb, which is a monument-like tomb with a single passage.
It was also during this excavation that Newgrange’s most intriguing feature was uncovered – a small opening above the main entrance called a “roof-box.” This roof-box flooded the main room of the tomb with sunlight only during the few days surrounding the winter solstice. This revealed that the ancient peoples who designed Newgrange had a working knowledge of astronomy. Additionally, this roof-box suggested that the entire religion or culture of the ancient people may have revolved around astronomical events.
This gif from DeLeoScience illustrates how the orbits of Earth and Mars around the Sun appear to make Mars move in a retrograde motion across our celestial sphere.
Over a single night, the planets behave much like the stars; they appear to rise in the east and set in the west. However, over the course of many nights, one will recognize that the movement of planets among the stars is quite intricate. The speeds and brightnesses of the planets fluctuate significantly, and while they typically travel eastward through the zodiac, they will periodically reverse course and move westward through the stellar background. This phenomenon is called apparent retrograde motion, and these periods can last anywhere from a few weeks to a few months.
For ancient astronomers who believed in a geocentric universe, this presented a problem. If planets supposedly moved in perfect circles around a stationary Earth, then what could be causing this peculiar backward motion? Greek astronomers like Ptolemy suggested that each planet traveled around Earth on a small circle, or epicycle, that simultaneously moved upon a larger circle, or deferent.
This animation from Kepler College depicts how a planet moving around Earth on an epicycle would show apparent retrograde motion.
Apparent retrograde motion can be explained much more simply with a heliocentric universe. Each of the planets orbits the Sun at a different rate; Mercury and Venus have shorter orbital periods than Earth since they are closer to the Sun, but Mars and the gas giants take a longer time to complete their revolutions. As the Earth passes or is passed by another planet in its orbit, the other planet appears to move back and forth relative to the stars in the distance. We know today that the heliocentric theory is the right one, but it would take almost 2,000 years from the time it was first suggested by Greek astronomer Aristarchus in 260 B.C. to be widely accepted. Nevertheless, the complexities of planetary motion would spur much of the debate over our planet’s place in the cosmos.
Located in Southeast Mexico, Chichen Itza served as the home to one of the largest Mayan cities and possesses pristine examples of complex archeoastronomy. Perhaps the most interesting structure is the pyamid El Castillo which translates to “the castle.” This pyramid serves as a prime example due to its complex engineering and design that highlights the Mayan’s fascination with the cosmos. This building was designed so that twice a year, during the spring and fall equinoxes, the shadow cast by the sun creates a serpentine like pattern that connects to a snakehead at the bottom.
An image of El Castillo casting its serpentine like shadow during an eclipse.
Each side of the pyramid consists of 91 steps, and when considering the top platform as an additional step, there are a total of 365 steps signifying an individual step for each day of the year.
This complex design only serves as an example as to how the cosmos was studied and cherished thousands of years ago.
My blog this spring is devoted to aspects of the Hubble telescope’s mission and operation. This submission, I hope to provide a basic understanding of redshift: the tendency of light’s wavelength to elongate as it travels through the universe.
Hubble was launched to gain a better understanding of faraway
stars that enjoyed prior obscurity from sub-atmospheric telescopes, which
suffer from particulate interference when looking through our sky. Redshift is
integral to the study of these distant, light emitting spheres because the
elements that stars burn are relatively predictable throughout their life. It
describes how far light has moved (‘shifted’) towards the low frequency (‘red’)
side of the electromagnetic spectrum. New stars fuse Hydrogen into Helium and
continue mashing nuclei together up the periodic table’s pecking order until
the star’s massive surplus of entropy has mostly been radiated into the dark
cosmos. Thankfully, each element of the periodic table gives off predictable
emission spectra, which are like fingerprints for combusting elements. The
light emitted might have multiple components, which can be differentiated
between and plotted on a frequency (or wavelength) chart. As the light from our
source travels, the difference between the component frequencies and the
magnitude of each included frequency does not change. That means we can
identify what element(s) produced the light and compare their known emission
spectra to the observed sample, the difference being how red-shifted the light
is.
Each band represents a frequency that light was emitted at originally on the left, and after redshifting on the right. Source: Wikipedia (Redshift article)
There are 3 reasons that Redshift happens. The first is the Doppler effect, which happens when any object change distance with the observer. Sound waves undergo this effect as well- an ambulance’s wail raises in pitch (‘blue’ shift) as it approaches and falls as it speeds away. Doppler Redshift is useful for measurements inside our galaxy, since light doesn’t have as monumental a journey to reach our sights. The second primary cause of Redshift is due to the expansion of space. As space time expands, any light emitted from one point in that “stretching fabric” must conquer not only the instantaneous distance between it’s source and the viewer, but also any growth of space. This means that older light travels further to reach us, and Edwin Hubble’s namesake law mathematically quantifies the correlation between Redshift, and the age and distance to any light we see. This means that knowing the Redshift of a star tells us it’s distance, and the distance combined with it’s angular size yields the actual size. So, Redshift is the first thing astronomers look to understand about distant objects. Watch this for a better understanding: Crash Course Astronomy Distances.
The final common cause of Redshift is gravitational lensing. I’m going to devote my next blog to that because this one is plenty long and gravitational lensing isn’t an easy concept to understand.
As you know, neutron stars are the result massive stars (many times more massive the the sun) collapsing inward on themselves, leaving behind an extremely dense and energetic core. As you might expect these stars are extremely energetic — what you might not know is that sometimes as a result of the in-falling star materials angular momentum, neutron stars can spin. Sometimes they end up spinning very fast. These are magnetars. And as a result of their extremely rapid periods of rotation, they exhibit egregiously large magnetic fields. These fields are millions of times stronger than any man-made magnet. In fact, the magnetic field is so high around a magnetar that the field itself has an energy density 10,000 greater than that of lead, and distorts the orbit clouds of atoms into cylinders. I.e., you do not want to be close to a magnetar. Fortunately, they are so energetic that after around 10,000 they effectively die, leaving behind a magnetized husk.
Astronauts floating against a starry backdrop. Food suspended in a spacecraft. These images are what have constructed our cultural understanding of space as a place where the gravitational rules are completely different from what we experience on Earth. This has led many to believe that spacecraft are completely devoid of gravity.
This is a picture of what many people call zero-gravity. It comes from the idea that if astronauts in a spacecraft look like they’re weightless, it must be because there’s no gravity weighing them down.
Some quick math calculations will reveal this simply isn’t true. At the height that most spacecrafts orbit, the force of gravity is indeed smaller, but it’s probably not at the level you’d expect. Perhaps this is why you’ve heard people call it micro-gravity? That’s actually wrong too! At a 250 km orbit, there is only a 10% decrease in gravitational force–certainly not enough for you to say it’s micro-gravity. You can see this math here or you can do it yourself, if you have the respective masses and orbit distance. Just plug it into the law of universal gravitation, if you remember that from class!
But we have to go back to that happy student in the picture we saw before. We know that we have weight on Earth because of the planet’s gravity. Why do those astronauts not have weight if there’s still gravity?
Answering this means taking a closer look at what it means to fall. While the spacecraft experiences the Earth’s gravity pulling it down, it is also moving forward at a high speed that brings it into what we call orbit. As vehicles such as the International Space Station circle Earth, they are technically doing a very drawn out fall. Moving forward at the same speed that they’re falling at brings astronauts into what we call free-fall–this looks to us like an absence of gravity. The shuttle’s motion is counterbalancing the Earth’s gravity, which feels to the astronauts like weightlessness. This creates the classic image we have of an astronauts helplessly floating above a dinner they can’t reach.
This means that both zero-gravity and micro-gravity are inaccurate explanations of what’s going on in spacecraft. Weightless is a much better description.
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Before the time of GPS, and all the modern forms of navigation we use today, people used to travel with the stars. Through the use of angular measurements, the sun, moon, planets, and stars could be used to find a position on earth. By looking at the angles between these celestial bodies the horizon, and your current location, you can find your position on the earth. This information allows you to pinpoint where you are and plot a course for where you want to go. Celestial navigation was a way to travel from point A to point B that relied strictly on what you were able to see and your environment around you. As a result, it is still a practice used today by groups such as the navy. It is a reliable means of navigation that does not depend on modern technology, such as electricity. Although, we have forms of navigation that are much more accurate, celestial navigation can be depended on when you have nothing else available. It is good technique to learn because, as the aphorism goes: “If it ain’t broke, don’t fix it”. The stars are not going anywhere anytime soon, so we might as well use them to our benefit.
Like many things in space, the planet Mars has been a point of interest for many since its discovery long ago. Some even believe that it could one day be a place for the human race to relocate. Curiosity, a rover launched back in November of 2011, has been exploring the surface of mars for about 6 years now. Originally its purpose was to establish if microbes could be supported by the environmental conditions present on Mars. More recently, however, gravity measurements on Aeolis Mons, a Martian mountain located in the Gale crater, have been taken by Curiosity in order to come closer to determining how the mountain was formed.
By NASA. Source: The New York Times – Curiosity rover in the Gale craterBy NASA. Source: Universe Today – Shows part of Curiosity’s Path through the Gale crater and up the bottom slope of Aeolis Mons
Gravimetry is the measurement changes in gravitational fields. Realizing that the accelerometers on Curiosity, originally intended to track the rover’s tilt, could also be used to calculate the change in the gravitational field of the Martian mountain was the catalyst for this new mission. As Curiosity traversed Aeolis Mons, the gravimetric measurements suggested that the mountain rock is porous. This data implies that the Gale crater actually was not filled to the brim with sediment, the previous Aeolis Mons formation theory, since porous rocks could not have upheld all the weight without compression. The findings do support previous theories in some aspect though. It seems that the mountain rock was just buried by either less dense material or not much material. Even so, this still adds to the mystery of the mountains formation. More questions have emerged because of this new research, but a valuable piece of the puzzle has been added.
An aerial view of Newgrange, the “roof-box” above the main entrance, and light streaming in through the roofbox, 
