Mars Orbit Rar
Kepler managed to discover the actual shape of the orbit of the planet Mars in its circulation around the Sun, as well as the rule governing its motion in the orbit. It was an astonishing accomplishment, and in this column and a few subsequent ones I hope to give some idea of what he did. ...Bill CasselmanUniversity of British Columbia, Vancouver, CanadaEmail Bill Casselman
Mars Orbit rar
The problem of inadequate observations was mostly solved by the vast collection of data assembled by the Danish astronomer Tycho Brahe. But Tycho had not agreed with Copernicus' point of view (no pun intended), and until Kepler arrived as his assistant his data on planetary motions did not contribute much to clarity. After Tycho's death, Kepler managed to discover the actual shape of the orbit of the planet Mars in its circulation around the Sun, as well as the rule governing its motion in the orbit. It was an astonishing accomplishment, and in this column and a few subsequent ones I hope to give some idea of what he did. Of course there have already been many attempts to do this, but with a topic like this, there should always be room for more.
For our purposes there are two coordinate systems of interest to an astronomical observer on earth. And in any coordinate system there are two kinds of coordinates, rectangular and polar. (1) The equatorial system. The origin is the center of the earth (which moves). The positive $z$-axis passes through the North Pole, the $(x, y)$ plane passes through the equator, and the positive $x$-axis is parallel to the ray towards the Sun from the Earth on the day of the Spring equinox. (2) The ecliptic system. The origin is again the center of the Earth, but the $(x, y)$-plane is that containing the Earth's orbit. The positive $z$-axis is located according to the right-hand rule regarding the Earth's motion in its orbit. The $x$-axis is the same as in the equatorial system. This is legitimate, because the line containing this ray is also the intersection of the equatorial plane with the orbital plane.
There is a problem with many aspects of coordinate systems in astronomy --- with respect to the fixed stars, the direction of the North Pole moves at a steady rate ("precession of equinoxes"). But then the length of a day isn't really constant, either (see an earlier Feature Column, Solar Daze), and the "fixed" stars aren't really fixed. Furthermore, no planet actually moves periodically in a fixed orbit. I'll ignore all these problems, which cause what are for us only secondary effects.
The rotation angle is the angle between the equatorial plane and that of the Earth's orbit. It can be estimated from knowing the highest latitude at which the Sun appears directly overhead in the summer. This occurs on the Tropic of Cancer at latitude $\varepsilon \sim 23.5^\circ$. Therefore $$ M = \left [ \matrix 1 & 0 & 0 \cr 0 & \cos(\varepsilon) & -\sin(\varepsilon) \cr 0 & \sin(\varepsilon) & \phantom-\cos(\varepsilon) \cr \right ] \cdot \hbox ecliptic = \hbox equatorial \, . $$
The pale path approximating the orbit of Mars shows the intersection of the celestial sphere with the plane of the Earth's orbit. I plotted it by computing the equatorial coordinates of a circular path in that plane, according to the procedure I sketched above. We can see that Mars sometimes lies above this ecliptic path, and sometimes below.
We can see from the second plot that these loops mark points in the orbit where the planet seems to be stationary and even moves backwards. Motion in this part of the orbit is called retrograde.
Moreover, the tilt of the orbit relative to our path around the sun is steep and retrograde, meaning the comet goes around the sun in the opposite direction than do the planets. As a result, this means it will, at some point, move quickly through our sky.
The full moon on June 13-14 qualifies as a supermoon, a term coined by astrologer Richard Nolle in 1979 to define a supermoon as a new or full moon that occurs when it is at its closest approach to Earth in a given orbit.
Globular clusters are also extremely old. The stars in M13 are thought to be around 12 billion years old, which is approaching the age of the universe itself. Our home galaxy, the Milky Way, is known to have about 150 globular clusters. They orbit outside the galaxy's disk, traveling tens of thousands of light-years above and below its spiral arms and most of its stars.
The question is whether wood has any material properties that make it a better fit for satellites than any alternative material. Nikkei Asia indicates that one potential advantage is that wood is transparent to many wavelengths that satellites use to communicate, potentially eliminating the need for external antennae. If said antennae would otherwise need to unfurl after a satellite reaches orbit, this could eliminate one potential source of hardware failure.
But the coverage by the BBC and others focuses on space junk. This is a real problem, as the amount of defunct satellites and random debris in low Earth orbit has created hazards for the functional stuff we'd like to keep there. Everything from scientific observatories to the International Space Station have had to be maneuvered around passing bits of junk.
Unfortunately, making satellite housings out of wood won't help with this, for many, many reasons. To start with, a lot of the junk isn't ex-satellites; it's often the boosters and other hardware that got them to orbit in the first place. Housings are also only a fraction of the material in a satellite, leaving lots of additional junk untouched by the change, and any wood that's robust enough to function as an effective satellite housing will be extremely dangerous if it impacts anything at orbital speeds.
Most of the coverage seems to present wooden satellites as helping with the space junk problem because of the fact that wood would burn up when it de-orbits. But this stuff is space junk precisely because it doesn't de-orbit. All of our plans for handling the existing abundance of space junk involve finding a way to induce it to leave orbit. Wood won't make any difference here.
The one point that wood might have in its favor, noted in some of the coverage and by Doi himself, is that it won't leave much in the atmosphere if it does de-orbit and burn up. Most other hardware will vaporize into a gas of aluminum and various other metals, perhaps oxidized. Again, having a wood housing won't eliminate these metals, given that many of them come from the satellites components and the rocket that put them in place. And, at least for the foreseeable future, this material won't be present in the atmosphere at high enough levels to be meaningful.
Even more promising for global coverage is SpaceX's Starlink program, which involves thousands of 570-pound satellites, each the size of a desk and orbiting 340 miles above the Earth. (SpaceX is currently authorized to launch 12,000 satellites, but they want to launch a total of 42,000.)
A new alternative to SpaceX's Starlink is a struggling company called OneWeb, which launched as WorldVu in 2012 and collapsed in March after Softbank decided to stop funding it. The company has74 satellites in orbit, and aspires to launch as many as Starlink intends to launch..
Now, their questions are one step closer to being answered thanks to NASA's Mars Atmosphere and Volatile Evolution, or MAVEN, mission, which recently completed one year in orbit around Mars.
MAVEN is a school-bus-sized spacecraft equipped with eight instruments that study the different layers of the Martian atmosphere as well as the space weather that bombards it. It takes about 4.5 hours for MAVEN to complete one orbit around Mars.
Research topics are the ecophysiology, genetic diversity and molecular biology of cyanobacteria from extreme environments, such as hot and cold deserts and Antarctic sub-glacial lakes.Researches aim at deciphering the cellular and molecular basis of cyanobacterial adaptation to extreme conditions on Earth but also to space and Martian simulated conditions.She is leading experiments on cyanobacteria exposed to low Earth orbit conditions outside the International Space Station (EXPOSE-R2 mission). The aim is to investigate the endurance of life, identify biosignatures to search for life on Mars; research deals also with the use of cyanobacteria to develop life-support systems for human outposts on the Moon and on Mars.Since 2015 she has the intellectual and scientific responsibility of about 200 cyanobactaerial of the genus Chroococcidiopsis isolated from hot and cold deserts, part of the Culture Collection of Microorganisms from Extreme Environments (CCMEE) established by E. Imre Friedmann.
Movement 3 gives us the sound of a space shuttle launch, which audiences see as it climbs from the pad, sets the solid rocket boosters and external tank adrift, then arrives in Earth orbit. The payload bay doors open, and the Hubble Space Telescope is deployed.
In an overwhelming entrance, the International Space Station rises into view, and we fly with the shuttle to dock with it, then do a glamour pass around the pair. We then leave the Earth behind and fly around the orbital paths of all the planets.
The universe is a big place, and sometimes researchers use the astronomical units to communicate how far celestial objects are separated from one another. For example, Jupiter orbits about 5 AU from the sun.
Mercury, the planet closest to the sun, gets as close as 29 million miles (47 million km) in its elliptical orbit, while objects in the Oort Cloud, the solar system's icy shell, are thought to lie as far as 9.3 trillion miles (15 trillion km).
NASA and SpaceX are currently in the midst of attempting to get Artemis-I launched and to the Moon, which will send multiple CubeSat satellites and an Orion spacecraft into the lunar orbit. Following engine troubles and a leak, the launch window has now been postponed until late September or early October. 041b061a72