The good news is that measures are being taken to sharpen their observation tools to enable finer pinpointing of the source of FRBs. "The event must be extremely energetic to be detectable from earth" (p.6).
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The good news is that measures are being taken to sharpen their observation tools to enable finer pinpointing of the source of FRBs. "The event must be extremely energetic to be detectable from earth" (p.6).
In the same issue there is an article on ice giants (Neptune and Uranus). We know very little about them, all from Voyager 2 over 30 years ago. They are definitely different from Jupiter and Saturn which are not ice giants but which have gaseous envelopes. So many questions need to be addressed.
It is interesting that Neptune and Uranus are ice giants and unlike Jupiter and Saturn. I previously assumed those four planets were similar being so large.
I remember looking at Mars and Saturn in the early morning last week as the Moon passed above them.
I also assumed the four giant planets were similar, but they are not. The further out ice giants are also different from each other, as well as from the two gaseous giants, Jupiter and Saturn. Neptune's surface is tossed by violent tornados and supersonic winds and has an earth-sized "Great Dark Spot". Uranus is deep-frozen.
There is a lot more about the ice giants, especially their many moons. Neptune has 14 moons, one, Triton, being bigger than Pluto and accounting for 99 percent of the mass of matter encircling Neptune. It orbits Neptune in the opposite direction to the planet's rotation, suggesting it was captured by Neptune, so is probably a dwarf planet from the Kuiper Belt.
There is a lot more about the moons of the ice giants, planets which, until the 1980s were just specks in space. They need re-visiting to understand them better.
Uranus has 27 moons (!), two of which Cordelia and Ophelia are described as shepherd moons for the epsilon ring around Uranus.
Source: Popular Astronomy May/June 2016 "Return to the Ice Giants" by Joseph Scaife (pp. 15-17).
That Triton might have been captured by Neptune is a nice way to think about it. I didn't know it had an orbit opposite to the planet's rotation. If Neptune has tornadoes it must have an atmosphere.
I think "tornado-like" would be more accurate. Neptune doesn't have an atmosphere as we think of it on earth.
Most planets have an atmosphere, commonly dominated by ammonia or methane. No other planet discovered so far has oxygen and hydrogen (H20) other than earth.
Why are ammonia or methane so common?
I have no idea.
I suspect it is because we have studied so few worlds in enough detail. We know about 9 worlds in our solar system. Perhaps in time we will have more world's to study and be able to see patterns better.
Perhaps the existence of life on Earth helps change the atmosphere.
Or indeed, vice versa...
Re: Atmospheres - Temperature and pressure appear to be the main determinate on how hydrogen (being the most abundant element along with helium in the universe) and other elements combine/sublime/condense on colder planets.
Sol System Planet atmospheres: http://www.universetoday.com/35796/a...f-the-planets/
http://lasp.colorado.edu/education/o...atandwhere.php
Ta ! (short for tarradiddle),Quote:
ATMOSPHERES... The atmospheres of Jupiter and Saturn are made almost entirely of hydrogen and helium, although there is some evidence they contain hydrogen compounds. Uranus and Neptune are made primarily of hydrogen compounds, with smaller traces of hydrogen, helium, metal and rock. The most common hydrogen compounds are methane (CH4), ammonia (NH3), and water (H2O).
The farther away a planet is from the Sun, the cooler its atmosphere will be. This means that the same gases will condense to form clouds at different altitudes on different planets because the condensation of a gas requires a specific amount of pressure and temperature. Ammonia, ammonium hydrosulfide and water make up the 3 cloud layers of Jupiter and Saturn. You can see from the graph to the right that these condense at lower altitudes in Saturn's atmosphere than they do in Jupiter's atmosphere.
tailor STATELY
The Universe Today articles in your link, tailor, are interesting but don't tell us more than the Popular Astronomy article in an earlier post in this thread.
Its been 30 years since the Voyager 2 flyby, so these planets need to be revisited. The 2 ice giants Uranus and Neptune remain the planets we know little about. They are very different. Neptune radiates more heat out into space than it receives from the sun, while Uranus is more sealed in under its icy mantle. The many moons of these two ice giants also remain largely unexplored.
The Voyager 2 Flyby was not enough to even identify and describe many of these moons. Uranus has 27 "known" moons, while Neptune has 14, one of which, Triton, is probably a captured dwarf planet, accounting for 99% of all the mass in orbit around Neptune. See post #524.
Three alien planets around a tiny cold star might be a good place to search for life. Doesn't mean intelligent life or even advanced forms of non-intelligent life.
Also, it seems we are still getting info from Cassini on Saturn's moon Titan. This despite the claims in Popular Astronomy that we are not getting any new material to add to what we knew from the Voyager 2 probe 30 years ago.
I've got my Mac back and can now create links again! Windows 10 was useless, while I used it the links disappeared!
For some reason those exoplanets around tiny stars are easier to study given our current technology. At least that is what I got from the article, but I would have thought larger systems would be easier to spot. Perhaps these smaller ones must be compact for the exoplanets to be in their sun's habitable zone and that compactness is easier for us to spot.
I will expect a retraction in the next issue of Popular Astronomy of the claim that we get no new material since Voyager 2. Cassini is still sending back data from Saturn's moon, Titan, and the lakes of pure methane on that moon.
Knowing that the lakes are pure methane does seem to be new information. The missions to Ceres and Pluto offered plenty of new information. I still wonder what those bright spots are on Ceres.
The bright spots on Ceres is a quite separate issue. The close-up views of Ceres suggest they may be salt deposits. This 2016 discussion of the Ceres project (to be extended to 2017) is the latest I have found: https://spaceflightnow.com/2016/04/0...time-at-ceres/
They mentioned that it is hard to keep things bright on a planetary surface, but this one has no atmosphere to deposit dust on the surface.
I guess we will see how the work being done on Ceres will be improved by the one year extension of the visit.
Planet 9 (or Planet 10 if we include Pluto) has a very wide and distant orbit round the sun. The theory is that it was captured and is in a bizarre highly elongated orbit. See also this post from EarthSky.
If it is verified - and that could take a long time, with such an orbit, many centuries perhaps, it would be sensational.
Read the two EarthSky posts for more information.
It is an interesting idea that the elliptical orbit of planet 9 might have been caused by a star early in the formation of the solar system rather than something wandering about that the Sun picked up.
Kepler is finding many Milky Way planets that could harbour life. That is a long way from finding planets that do harbour life, but it is quite a radical change.
We took the train to Bollnäs yesterday and I borrowed a copy of Populär Astronomi. I may make a post on some of the material in it.
It looks like tens of billions of potentially habitable planets in the Milky Way.
In Populär Astronomi June 2014 (2 years ago) there was an item on a dwarf planet that I had never before heard of. It's called Sedna, with a diameter of only 450 km, just a fifth of Pluto's. This is an Oort Cloud denizen, not a Kuiper Belt denizen like Pluto. It takes 11,400 years for Sedna to complete one orbit round the sun.
There are in fact many such Trans-Neptunian objects, some 270 (!) counted so far. Some are not even dwarf planets, as they could easily have their course changed by a large outer planet. They are also known as Centaurs.
So there we are, I have been ignorant of this and now start to catch up...
Space.com has an article on a dwarf planet informally dubbed Snow White. It is larger than hitherto estimates as its surface is darker than expected. This makes it the third largest dwarf planet in our solar system after Pluto and Eris, though this is just a guess. It completes an orbit of the sun every 547.5 years, while Pluto's orbit is 248 years.
These outer bodies of the solar system make them less likely to receive a visit in the near future, especially as their orbits are in many cases highly elliptical. For now we will have to await newer and more powerful telescopes to learn more about them. The same is likely to be true of the 9th planet (see an earlier post on this).
It seems that Snow White should have been nicknamed Rose Red. The oblong shape of Haumea is also unusual.
This is from my subscription to Popular Astronomy in the periodic newsletters they send out. It is the strange sausage shaped object that YesNo mentioned in his latest post in this thread.
FRAGMENT PROBABLY FROM THE EARTH'S FORMATION RETURNS
ESO
Astronomers have found a unique object that appears to be made of inner-Solar-System material from the time of the Earth's formation, which has been preserved in the Oort Cloud far from the Sun for thousands of millions of years. Observations with the Very Large Telescope, and the Canada-France-Hawaii Telescope, show that C/2014 S3 (PANSTARRS) is the first object to be discovered on a long-period cometary orbit that has the characteristics of a pristine inner-Solar-System asteroid. It may provide important clues as to how the Solar System formed. Observations indicate that it is an ancient rocky body, rather than a contemporary asteroid that strayed out. As such, it is one of the potential building blocks of the rocky planets, such as the Earth, that was expelled from the inner Solar System and preserved in the deep freeze of the Oort Cloud for thousands of millions of years. C/2014 S3 (PANSTARRS) was originally identified by the Pan-STARRS1 telescope as a weakly active comet a little over twice as far from the Sun as the Earth. Its current long orbital period (around 860 years) suggests that its source was in the Oort Cloud, and it was nudged comparatively recently into an orbit that brings it closer to the Sun. The team immediately noticed that C/2014 S3 was unusual, as it does not have the characteristic tail that most long-period comets have when they approach so close to the Sun. As a result, it has been dubbed a Manx comet, after the tailless cat. Within weeks of its discovery, the team obtained spectra of the very faint object with the Very Large Telescope in Chile.
Study of the light reflected by C/2014 S3 indicates that it is typical of asteroids known as S-type, which are usually found in the inner asteroid main belt. It does not look like typical comets, which are believed to form in the outer Solar System and are icy rather than rocky. It appears that the material has undergone very little processing, indicating that it has been deep-frozen for a very long time. The very weak comet-like activity associated with C/2014 S3, which is consistent with the sublimation of water ice, is about a million times lower than is exhibited by active long-period comets at similar distances from the Sun. Astronomers conclude that the object is probably made of fresh inner-Solar-System material that has been stored in the Oort Cloud and is now making its way back into the inner Solar System. Various theoretical models are able to reproduce much of the structure that we see in the Solar System. An important difference between the models is what they predict about the objects that make up the Oort Cloud. Different models predict significantly different ratios of icy to rocky objects. This first discovery of a rocky object from the Oort Cloud therefore initiates a potentially important test of the different predictions of the models. The authors estimate that observations of 50--100 such Manx comets will be needed to distinguish between the current models, so it promises to be a long time before such a study can throw much light on the origins of the Solar System.
I wonder how those Manx comets got out that far. Perhaps the inner planets kept pushing them away rather than attracting them.
I had to look up Manx Comet to find out more about them, tail-less comets like the manx cat. But I still can't understand how "the inner planets keep pushing them away rather than attracting them." What do you mean by that?
I used to think that objects where drawn into a planet by the planet's gravity and then I recall reading that objects can also be pushed away by gravity as well. This would help push objects originating close to the Sun further out.
I've never heard of that myself. I don't suppose you can cite a reference...
I don't have a reference. I learnt it from this thread. It would be how probes use the gravity of other planets to extend their range. I'll see if I can find some reference later today.
Here's a reference you provided for gravity assist that is what I was referring to when using a planet's gravity to move a probe further. I assume this is similar to the way a planet would clear its path by pushing objects out of the way rather than absorbing those objects.Quote:
Originally Posted by Dreamwoven
It is most unlikely that any Oort Cloud objects will come anywhere near the solar system. A Kuiper Belt object like Pluto is vastly nearer but one probe, New Horizons did make it, taking advantage of a one-in-250 years conjunction that brought Pluto nearer. We may just be lucky - or at least later generations - 11+ thousand years for one orbit is a long time to wait...
Quote:
Originally Posted by Dreamwoven
Yesterday we saw the first half of a Swedish TV Program on Origami as applied to nature, how leaves and flowers open up to their full size from buds. They fold out to their full size. The Swedish language uses the origami principle to describe development. The word utvekla means to develop but also means to bend out.
Apart from being interesting in itself I remembered that there are plans in development to use solar wind for space travel. The applications of this are many and potentially far-reaching. There is a lot of material on this in all it variations in the above Wikipedia article on Solar Sail applied to un-manned space travel. Speed builds up slowly but faster and faster. Travel to the outer planets (e.g. Neptune 8.5 years) and even to the Oort Cloud are possible: "Such a sail would take "Two and a half years to reach the heliopause, six and a half years to get to the Sun’s inner gravitational focus, with arrival at the inner Oort Cloud in no more than thirty years."
Thirty years seems a reasonable time to wait. You mentioned earlier about using lasers to send very small probes even faster and further should those ideas get developed.
I suspect some of the nearer places would be high priority, like the moons of the outer planets, Uranus and Neptune, for example. It would be handy to complete the mapping of many moons of the outer planets, and after that the nearer reaches of the Oort Cloud.