Soheil_Esy
Fazanavard فضانورد
- Joined
- Apr 5, 2015
- Messages
- 744
- Reaction score
- 19
- Points
- 18
13.06.2015
Scientists have discovered that Saturn's Phoebe ring – the largest planetary ring known to mankind – is even larger than they once suspected, although they still can't see it with their own eyes.
"I was giving talks saying Saturn has a giant invisible ring, which makes you sound just perfectly crazy," lead author Douglas Hamilton, a planetary scientist at the University of Maryland, told the Los Angeles times.
The Phoebe ring wasn't discovered until 2009 by a team – which included Hamilton – armed with infrared imagery from the Spitzer Space Telescope. At the time, they estimated that the ring stretched from 4.8 million to 7.76 million miles.
Years later, Hamilton and his team have determined that Phoebe is much larger than originally estimated – about 30% larger. Using NASA's Wide-field Infrared Survey Explorer telescope they have found that it stretches from about 3.75 million to 10.1 million miles.
"It is 10 to 20 times larger than the second-biggest ring, so this thing is absolutely gargantuan," said Hamilton, whose team's study was published earlier this week in the journal "Nature."
Carl Engelking, of Discovery Magazine, writes: "If you looked into the night sky from Earth, the Phoebe ring – if it were visible – would appear to be as wide as two of our Moons."
It's important to note that the Moon is only 238,900 miles from Earth, while Saturn is 746 million miles away, at its closest.
Another comparison by Engelking: "If Saturn's famous rings were toe rings, the Phoebe ring would be a monster truck tire, for a simple comparison."
The ring is composed of small particles that are incredibly far apart from each other, but it can be clearly seen at infrared wavelengths as a faint halo. What’s more: Scientists estimate that roughly 90% of the particles that make up Phoebe are smaller than the size of a soccer ball.
http://sputniknews.com/us/20150613/1023301083.html
Scientists have discovered that Saturn's Phoebe ring – the largest planetary ring known to mankind – is even larger than they once suspected, although they still can't see it with their own eyes.
"I was giving talks saying Saturn has a giant invisible ring, which makes you sound just perfectly crazy," lead author Douglas Hamilton, a planetary scientist at the University of Maryland, told the Los Angeles times.
The Phoebe ring wasn't discovered until 2009 by a team – which included Hamilton – armed with infrared imagery from the Spitzer Space Telescope. At the time, they estimated that the ring stretched from 4.8 million to 7.76 million miles.
Years later, Hamilton and his team have determined that Phoebe is much larger than originally estimated – about 30% larger. Using NASA's Wide-field Infrared Survey Explorer telescope they have found that it stretches from about 3.75 million to 10.1 million miles.
"It is 10 to 20 times larger than the second-biggest ring, so this thing is absolutely gargantuan," said Hamilton, whose team's study was published earlier this week in the journal "Nature."
Carl Engelking, of Discovery Magazine, writes: "If you looked into the night sky from Earth, the Phoebe ring – if it were visible – would appear to be as wide as two of our Moons."
It's important to note that the Moon is only 238,900 miles from Earth, while Saturn is 746 million miles away, at its closest.
Another comparison by Engelking: "If Saturn's famous rings were toe rings, the Phoebe ring would be a monster truck tire, for a simple comparison."
The ring is composed of small particles that are incredibly far apart from each other, but it can be clearly seen at infrared wavelengths as a faint halo. What’s more: Scientists estimate that roughly 90% of the particles that make up Phoebe are smaller than the size of a soccer ball.
http://sputniknews.com/us/20150613/1023301083.html
Small particles dominate Saturn’s Phoebe ring to surprisingly large distances
11 June 2015
Saturn’s faint outermost ring, discovered in 2009 (ref. 1), is probably formed by particles ejected from the distant moon Phoebe. The ring was detected between distances of 128 and 207 Saturn radii (RS = 60,330 kilometres) from the planet, with a full vertical extent of 40RS, making it well over ten times larger than Saturn’s hitherto largest known ring, the E ring. The total radial extent of the Phoebe ring could not, however, be determined at that time, nor could particle sizes be significantly constrained. Here we report infrared imaging of the entire ring, which extends from 100RS out to a surprisingly distant 270RS. We model the orbital dynamics of ring particles launched from Phoebe, and construct theoretical power-law profiles of the particle size distribution. We find that very steep profiles fit the data best, and that elevated grain temperatures, arising because of the radiative inefficiency of the smallest grains, probably contribute to the steepness. By converting our constraint on particle sizes into a form that is independent of the uncertain size distribution, we determine that particles with radii greater than ten centimetres, whose orbits do not decay appreciably inward over 4.5 billion years, contribute at most about ten per cent to the cross-sectional area of the ring’s dusty component.
http://www.nature.com/nature/journal/v522/n7555/full/nature14476.html
