Posts tagged planets
Posts tagged planets
(Not including Earth)
Our of curiosity, I made a survey for this. Mostly because I’m interested in what people consider “interesting” when it comes to these things, but also whether or not that impacts how much you like it. But please do not answer the questions unless you have an actual answer for both of them. In other words, don’t just choose one randomly without giving it any thought.
The survey can be found here. I’ll post the results a week from today, on January 13th.
An interactive 3-D model of the solar system
Two decades of searching have failed to turn up another planetary system like ours. Should we be worried?
The image [above] is an up to date map of the solar system displaying the orbits of the terrestrial planets and the estimated position of thousands of known asteroids. This diagram is missing comets, space probes and, of course, the undiscovered asteroids. Even conservative estimates would suggest that for every asteroid on a dangerous Earth-Approaching orbit there are hundreds more which have yet to be discovered. There are over 300 known objects on Earth-crossing orbits, the majority of which are potentially capable of causing death and destruction on a scale unheard of in human history.
The terrestrial planets (Mercury, Venus, Earth and Mars) are shown on the diagram by Cyan or White squares, and their orbits are represented by the blue ellipses around the Sun (the yellow dot at the centre). The Earth is highlighted because of its special importance to us. Small green points mark the location of asteroids which do not approach close to the Earth right now. This does not exclude the possibility that they will do so in the future but generally we can consider the Earth to be safe from these for the near future. Yellow objects (with the exception of the one in the middle which we astronomers call the Sun ;-) are Earth approaching asteroids which are called Amors after the first one discovered. Amors have orbits which come close to the Earth but they don’t cross the Earth’s orbit. However, their orbits are close enough to the Earth that they could potentially be perturbed by the influence of the planets and begin to cross the Earth’s orbit in a short time. There are over 300 known objects on such orbits.
Finally the red boxes mark the location of the Apollo and Aten asteroids. These cross the Earth’s orbit and are the most directly identifiable astronomical threat for the near future. Included in this selection is the infamous asteroid, 1997XF11, which made a major impact on the world’s headlines in March 1997 when observations indicated that it had a good chance of colliding with the Earth in 2028. Thankfully, new observations were made and the newly calculated orbit predicts a close approach of about 600,000 kilometres. Other asteroids which have orbits which may hit the Earth are 1999 AN 10 and 1998 OX 4. Further observation is required to determine their orbits in sufficient detail to predict an impact or a near miss.
It is estimated that there are perhaps 100,000 to 1,000,000 undiscovered asteroids on similar Earth crossing orbits.
Have a Nice Day.
Video Created by Scott Manley, this is a view of the solar system showing the locations of all the asteroids starting in 1980, as asteroids are discovered they are added to the map and highlighted white so you can pick out the new ones.
The final colour of an asteroids indicates how closely it comes to the inner solar system.
Earth Crossers are Red
Earth Approachers (Perihelion less than 1.3AU) are Yellow
All Others are Green
Notice now the pattern of discovery follows the Earth around its orbit, most discoveries are made in the region directly opposite the Sun. You’ll also notice some clusters of discoveries on the line between Earth and Jupiter, these are the result of surveys looking for Jovian moons. Similar clusters of discoveries can be tied to the other outer planets, but those are not visible in this video.
As the video moves into the mid 1990’s we see much higher discovery rates as automated sky scanning systems come online. Most of the surveys are imaging the sky directly opposite the sun and you’ll see a region of high discovery rates aligned in this manner.
At the beginning of 2010 a new discovery pattern becomes evident, with discovery zones in a line perpendicular to the Sun-Earth vector. These new observations are the result of the WISE (Widefield Infrared Survey Explorer) which is a space mission that’s tasked with imaging the entire sky in infrared wavelengths.
The scale of the video at 1080P resolution is roughly 1million kilometers per pixel, and each second of video corresponds to 60 days.
Currently we have observed over half a million minor planets, and the discovery rates show no sign that we’re running out of undiscovered objects, scientific estimates suggest that there are about a billion asteroids larger than 100metres (about the size of a football field).
28 April 2011 by Richard Webb
Every four years, Wood’s committee revises these numbers, and the results of the latest overhaul are due any day. Normally it is a routine celebration of the onward march of precision metrology, as the constants are redefined with accuracies that edge ever closer to 1 part in a billion.
All except gravity, that is, which has always been a bit of a party pooper. More than 200 years of measurements of Newton’s constant - “big G” to its friends - have delivered a number accurate to a measly 1 part in 10,000. The latest round of experiments, Parks and Faller’s included, raise the dismal prospect that this could get even worse. Wood’s jury is still out, but depending on what they agree this month it could become official: gravity is going down.
Gravity’s ways are as mysterious as its effects are ubiquitous. Ever since Isaac Newton grappled with an apple over 300 years ago to produce the first quantitative description of the force, we have been puzzling over what it means. While Newton had no answer, he at least came up with a definition - a handy formula that allows us to work out its effects. According to his inverse square law, gravity makes any two objects attract one another with a force proportional to their masses divided by the square of the distance separating them. Riding at the front of that equation, telling us how big that force should be, is big G.
Pending a shiny new quantum depiction of gravity, no theory tells us where this number comes from, or what its value should be. “Big G is just there,” says Clive Speake of the University of Birmingham, UK, who has spent 30 years investigating the ups and downs of gravity. It is there in Newton’s inverse square law and in Einstein’s general theory of relativity, our most accurate description of gravity to date.
The only way to reveal gravity’s true worth is to measure it in highly controlled experiments - which is easier said than done. Earth’s hulking mass sucks everything towards it, masking a fundamental truth: gravity is by far the weakest of nature’s four fundamental forces. And that means it is by far the trickiest to measure.
Since Henry Cavendish first attempted to measure it a little more than two centuries ago, progress has been painfully slow (see “Big G, little g”). “It is not a case of someone pops into a lab, stays a week and comes out with a number,” says Wood. “Most of the experiments take a decade.” Few people have the time, resources or nerve to stick at it that long.
It doesn’t help that there is no obvious pay-off to pinning down big G. A precise number would help us predict the motions of planets and stars more accurately, but no applications depend on it in the way that, say, GPS depends on knowing how long a second lasts to 1 part in a trillion.
Explanation: On June 4, 2010 Regulus, alpha star of the constellation Leo, and wandering planet Mars were at about the same apparent brightness, separated on the sky by 1.5 degrees. An ingenious and creative 10 second exposure from a swinging camera recorded these gyrating trails of the celestial pairing. Can you tell which trail belongs to the star and which to the planet? Hint: atmospheric turbulence causes the image of the star to scintillate or vary in brightness and color more readily than the planet. The scintillation is more pronounced because the star is effectively a point source of light seen as a narrow bundle of light rays. Rapidly changing refraction due to turbulence along the line of sight affects different colors of light by different amounts and generally produces a twinkling effect for stars. But Mars is much closer than the distant stars and an extended source of light. Though tiny, its disk is seen as a bundle of light rays that is substantially broader compared to a star’s and so, on average, less affected by small scale turbulence. The result is the varied, rainbow like trail for Regulus (left) and the steadier, consistently reddish trail for Mars.
By John Roach
Financial woes have delivered a serious blow to the search for E.T. One of its best tools, the Allen Telescope Array in northern California, has been put on hold until new funding is located.
“It is a huge irony,” Jill Tarter, director of SETI research at the SETI Institute in Mountain View, Calif., told me today. ”Now we actually know where to point the telescopes to look at planets, but we don’t have the telescopes to point right now, so a very ironic situation.”
For decades, astronomers have pointed their telescopes at stars they thought were likely to have planets around them. This February, the first results from the NASA’s Kepler Mission revealed 1,235 potential worlds in orbit around distant stars.
ATA financial woes