The closest point to the Sun in a planet’s orbit is called Perihelion. The furthest point is called Aphelion. The planet moves fastest at perihelion and slowest at aphelion.
GIFs extracted from Year On Earth
Planets in our Solar System orbit the Sun. The orbits of some planets are almost perfect circles, but others are not. Some orbits are shaped more like ovals, or “stretched out” circles.
Scientists call these oval shapes “ellipses”. If a planet’s orbit is a circle, the Sun is at the center of that circle. If, instead, the orbit is an ellipse, the Sun is at a point called the “focus” of the ellipse, which is not quite the same as the center.
Since the Sun is not at the center of an elliptical orbit, the planet moves closer towards and further away from the Sun as it orbits. The place where the planet is closest to the Sun is called perihelion.
When the planet is furthest away from the Sun, it is at aphelion. The words “aphelion” and “perihelion” come from the Greek language. In Greek, “helios” mean Sun, “peri” means near, and “apo” means away from.
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Gene Cernan took this photo of his Gemini 9 spacecraft in 1966
Amazing Sky Photos Show Space Station Near Moon & Jupiter
Imaged Above: Multiple images of the International Space Station flying over the Houston area have been combined into one composite image to show the progress of the station as it crossed the face of the moon in the early evening of Jan. 4, 2012. Credit: NASA
Two photographers have snapped spectacular portraits of the International Space Station streaking across the night sky, catching the orbiting lab crossing the moon and slipping by Jupiter.
In one series of photos, NASA photographer Lauren Harnett captured images of the moon at the exact moment that the space station passed across its face in what scientists call a “transit”.
Harnett took the photos on Wednesday (Jan. 4) from NASA’s Johnson Space Center in Houston. She then combined several images into a composite view that shows the space station just before and after it crossed the moon’s disk.
“She had to struggle with a window of visibility limited by fog and clouds, and I think she got some excellent results,” said NASA spokesman Mike Gentry at the space center.
Lasers Measure Earth’s Rotation and Wobble
The Earth spins around once every 24 hours on its axis, creating the continuous cycle of day and night. But this rotation isn’t as straightforward as it sounds: Forces large and small cause the Earth to wobble as it spins. This wobbling can pose a problem for navigation systems like GPS.
Scientists working with lasers and mirrors are refining a new system to track the Earth’s rotation and its kinks.
The pull of gravity from the sun and the moon contribute to the planet’s wobble. So do variations in atmospheric pressure, ocean loading and the wind, which change the position of the Earth’s axis relative to the surface. Together their effect is called the Chandler wobble, and it has a period of 435 days.
Another force causes the rotational axis to move over a period of a year. This “annual wobble” is due to the Earth’s elliptical orbit around the sun.
Retrograde Mars
Most of the time, the apparent motion of Mars in Earth’s sky is in one direction, slow but steady in front of the far distant stars. About every two years, however, the Earth passes Mars as they orbit around the Sun.
During the most recent such pass, Mars loomed particularly large and bright. Also during this time, Mars appeared to move backwards in the sky, a phenomenon called retrograde motion.
Credit & Copyright: Tunc Tezel
Big Asteroid to Cross Earth-Moon Orbit Tuesday
An asteroid the size of an aircraft carrier is to soar past the Earth this week and, while NASA is certain that the space rock will not hit us, it will be our closest encounter with such a large chunk of rock in three decades.
The 400-yard-wide asteroid is called 2005 YU55 and at the point of closest approach it will graze our planet at 201,700 miles — about 10 percent closer to Earth than the Moon’s typical orbit.
What Does It Feel Like to Fly over Planet Earth?
Have you ever dreamed of flying high above the Earth? Astronauts visiting the International Space Station do this every day, circling our restless planet twice every three hours. A dramatic example of their view was compiled in the above time-lapse video from images taken earlier this month. As the ISS speeds into the nighttime half of the globe, familiar constellations of stars remain visible above. An aerosol haze of Earth’s thin atmosphere is visible on the horizon as an thin multi-colored ring. Many wonders whiz by below, including vast banks of white clouds, large stretches of deep blue sea, land lit up by the lights of big cities and small towns, and storm clouds flashing with lightning. The video starts over the northern Pacific Ocean and then passes from western North America to western South America, ending near Antarctica as daylight finally approaches.
Image Credit: NASA; Acknowledgement: Infinity Imagined
Animation: Kepler-16b: A Planet with Two Suns
If you stay up long enough, you can watch both suns set. Such might be a common adage from beings floating in the atmosphere of Kepler 16b, a planet recently discovered by the space-based Kepler satellite.
The above animated video shows how the planetary system might look to a visiting spaceship. Although multiple star systems are quite common, this is the first known to have a planet. Because our Earth is in the orbital plane of both stars and the planet, each body is seen to eclipse the others at different times, producing noticeable drop offs in the amount of light seen. The frequent eclipses have given Kepler 16b the most accurate mass and radius determination for a planet outside our Solar System. To find a planet like Saturn in an orbit like Venus — so close to its binary star parents — was a surprise and will surely become a focus of research.
Illustrated Video Credit: NASA, JPL-Caltech, T. Pyle; Acknowledgement: djxatlanta
What Does It Feel Like to Fly over Planet Earth?
Have you ever dreamed of flying high above the Earth? Astronauts visiting the International Space Station do this every day, circling our restless planet twice every three hours. A dramatic example of their view was compiled in the above time-lapse video from images taken earlier this month. As the ISS speeds into the nighttime half of the globe, familiar constellations of stars remain visible above. An aerosol haze of Earth’s thin atmosphere is visible on the horizon as an thin multi-colored ring. Many wonders whiz by below, including vast banks of white clouds, large stretches of deep blue sea, land lit up by the lights of big cities and small towns, and storm clouds flashing with lightning. The video starts over the northern Pacific Ocean and then passes from western North America to western South America, ending near Antarctica as daylight finally approaches.
Image Credit: NASA; Acknowledgement: Infinity Imagined
Animation: Kepler-16b: A Planet with Two Suns
If you stay up long enough, you can watch both suns set. Such might be a common adage from beings floating in the atmosphere of Kepler 16b, a planet recently discovered by the space-based Kepler satellite.
The above animated video shows how the planetary system might look to a visiting spaceship. Although multiple star systems are quite common, this is the first known to have a planet. Because our Earth is in the orbital plane of both stars and the planet, each body is seen to eclipse the others at different times, producing noticeable drop offs in the amount of light seen. The frequent eclipses have given Kepler 16b the most accurate mass and radius determination for a planet outside our Solar System. To find a planet like Saturn in an orbit like Venus — so close to its binary star parents — was a surprise and will surely become a focus of research.
Illustrated Video Credit: NASA, JPL-Caltech, T. Pyle; Acknowledgement: djxatlanta
Ganymede Transit of Jupiter
One of Jupiter’s many moons (Ganymede) caught transiting across Jupiter’s orbital belt with almost purpose and beauty.
Copyright: Mark Shelley
Quick Space Fact:
When thinking about space, never rule out the Goldilocks Zone of a celestial body’s gravitational pull on other objects. Like our own Earth, when you have planets and Stars or Solar systems orbiting within a comfortable distance of the body they orbit. The moon safely orbits us, We orbit the Sun safely, Our solar system is safely placed at the edges of the Milky Way. Imagine how chaotic the metropolis of the Milky Way, the center of it is. Without these comfort zones you wouldn’t have life, but always remember these zones can appear in the unlikeliest of places as well. If we were any closer into the Milky Way, life might have arose very differently or never at all. Be grateful not for what you have, but the fact that you and everyone around You were even birthed on such nurturing conditions based on chances.
The Wonders of Orbits.
Ganymede Transit of Jupiter
One of Jupiter’s many moons (Ganymede) caught transiting across Jupiter’s orbital belt with almost purpose and beauty.
Copyright: Mark Shelley
