Astronomy

We are learning new things from Cassini's long visit at the moon, Titan, especially seasonal changes in it polar regions. See http://www.universetoday.com/131636/...amic-business/

It is good that missions last a while so we can observe such seasonal changes.

How many planets are there in our galaxy? A simple question but no simple answer. We have only recently realised just how many planets there are likely to be. See http://www.universetoday.com/30296/h...in-the-galaxy/. We don't even know how many stars there are in our galaxy (The Milky Way). So any attempt to enumerate the planets in the galaxy is even more difficult. Of these, only a tiny fraction can be habitable.

Cassini has been at Saturn now since 2004, and is about to plunge between the rings of Saturn and investigate them.

http://www.space.com/34488-cassini-f...w-science.html

http://www.universetoday.com/131677/...ly-downloaded/. This shows how long it takes to download information on the flyby of Pluto that New Horizons made. Well over a year in this case. New Horizons has continued deeper into the Kuiper Belt, making for a flyby of an object there that is mentioned in an earlier post on p.56.

The article shows there were constraints the New Horizon designers were up against, but it doesn't say exactly what they were. For some reason, the craft could only have a limited power output of 2-10 watts. It could only have a low downlink rate of 1-4 kilobits per second. And it had limited memory since they will have to erase its hard drive so it could continue collecting data for an extended mission.

I would think some of these constraints could be relaxed in future missions with better technology.

Neptune and Uranus: the two outer ice giants of the family of solar planets. Each is described and discussed for what little we know of them:

http://www.universetoday.com/21581/neptune/

http://www.universetoday.com/18855/uranus/

Just about the only information we have on Neptune the large gas giant (and the furthest out of all the planets except the dwarf planet Pluto) is the flyby that Voyager 2 did way back in 1989. See preceding post for the link on Neptune. Neptune has 14 known moons and also five rings around it. But a further visit to this distant and little-known planet might be worth making, perhaps in conjunction with a visit to Uranus. Uranus has 13 "inner moons" and nine "irregular moons". It also has 13 distinct rings around it. Again only Voyager 2 has done a flyby, though there are tentative plans for further visit. It rotates on it's side which is unique among the giant planets.

There is a graph in this link showing the axis of rotation of the various planets with some speculation on why we see such divergence: https://www.quora.com/Why-do-Venus-a...-anticlockwise

Although Uranus rotates on its side, Venus rotates upside down. That is, it rotates in the opposite direction to Earth's rotation.

Yes,its speculation, much like Velikovsky speculated that Venus was a captured comet, but as with all such ideas we don't really know why.

http://www.space.com/16144-kuiper-belt-objects.html.

This discusses the main kuiper belt objects we know a bit about today, including the mysterious Planet 9.

A link in that article led to one on the Oort cloud: http://www.space.com/16401-oort-clou...icy-shell.html

It helped me see the difference between the Kuiper belt and the Oort cloud.

http://www.space.com/34555-how-many-...able-zone.html

An interesting article on habitable planets.

It is interesting from the article that red dwarfs can last trillions of years and most of the stars are red dwarfs.

Not many people read the articles in the links. So I will just elaborate on the reasons why red dwarf stars are of interest in this context:

Van Laerhoven and her colleagues focused on K and M type stars, also known as red dwarfs. These stars are small, cold and about one-fifth the sun's mass and up to 50 times fainter. Red dwarfs constitute up to 70 percent of the stars in the universe, and NASA's Kepler spacecraft has discovered that at least half of these stars host rocky planets that are one-half to four times the mass of Earth.

Red dwarf planets are potentially key places to search for life, not just because there are so many of them, but also because of their incredible longevity. Unlike the sun, which will die in a few billion years, red dwarfs will take trillions of years to burn through their fuel, significantly longer than the age of the universe, which is about 13.8 billion years old. This longevity may give life ample time to develop on the planets that orbit these stars.

The habitable zones of red dwarfs fall close to these stars because of how cool they are — often closer than the distance at which Mercury orbits the sun. This closeness makes red dwarfs appealing to scientists hunting for habitable worlds, since planets in those habitable zones will cross in front of their star more often, making them easier to detect than planets that orbit farther away.

For the new research, the scientists carried out computer simulations involving a red dwarf about half the sun's mass, surrounded by a number of rocky planets with the same mass as Earth revolving around the star in circular orbits. These simulations each lasted up to 10 billion orbits of the innermost planet in each system. A planet at the inner edge of such a red dwarf's habitable zone would take only about one-fifth of an Earth-year to complete an orbit, Van Laerhoven said.

My suspicion is that life doesn't need a lot of time, perhaps a few billion years. What is nice is that it should have a safe place to be for much longer. Of course the habitable zone changes over time. I suspect that is the same with dwarf stars.

Perhaps the next question I would have is how long can a planet with a red dwarf star expect to remain in its habitable zone?

The answer is in the second paragraph in my post:

Red dwarf planets are potentially key places to search for life, not just because there are so many of them, but also because of their incredible longevity. Unlike the sun, which will die in a few billion years, red dwarfs will take trillions of years to burn through their fuel, significantly longer than the age of the universe, which is about 13.8 billion years old. This longevity may give life ample time to develop on the planets that orbit these stars..

In short, longer than the universe has been in existence.

Water, water everywhere: even on a pure metal asteroid...

On Psyche, the largest asteroid in the solar system.

http://www.universetoday.com/131738/...ater-deposits/

The James Webb Space Telescope is ready for launching: http://www.space.com/34593-james-web...18-launch.html. It is the new, much larger and more efficient space telescope since the Hubble Space Telescope. We should learn a lot from it once it is launched and ready to start work.

The telescope will be much more powerful than even Hubble for two main reasons, Mather said at the conference. First, it will be the biggest telescope mirror to fly in space. "You can see this beautiful, gold telescope is seven times the collecting area of the Hubble telescope," Mather said. And second, it is designed to collect infrared light, which Hubble is not very sensitive to.

Earth's atmosphere glows in the infrared, so such measurements can't be made from the ground. Hubble emits its own heat, which would obscure infrared readings. JWST will run close to absolute zero in temperature and rest at a point in space called the Lagrange Point 2, which is directly behind Earth from the sun's perspective. That way, Earth can shield the telescope from the sun's infrared emission, and the sun shield can protect the telescope from both bodies' heat.

The telescope's infrared view will pierce through obscuring cosmic dust to reveal the universe's first galaxies and spy on newly forming planetary systems. It also will be sensitive enough to analyze the atmospheres of exoplanets that pass in front of their stars, perhaps to search for signs of life, Mather said.

NASA has now got an asteroid warning system, with 5 days notice of any major threat to Earth. Sounds good. See: http://www.universetoday.com/131737/...-days-warning/:

Everyone knows it was a large asteroid striking Earth that led to the demise of the dinosaurs. But how many near misses were there? Modern humans have been around for about 225,000 years, so we must have come close to death by asteroid more than once in our time. We would have had no clue.

Of course, it’s the actual strikes that are cause for concern, not near misses. Efforts to predict asteroid strikes, and to catalogue asteroids that come close to Earth, have reached new levels. NASA’s newest tool in the fight against asteroids is called Scout. Scout is designed to detect asteroids approaching Earth, and it just passed an important test. Scout was able to give us 5 days notice of an approaching asteroid.

I found this article interesting and the Max Planck Institute is a top research center in Germany.

"Searching for aliens who already know we're here
Astronomers suggest that future searches focus on that part of the sky in which distant observers can notice the yearly transit of Earth in front of the Sun"
http://www.astronomy.com/news/2016/0...know-were-here

That link you sent me, Danik, was interesting. This quote I found particularly intriguing:

Not every star is equally well suited as a home of extraterrestrial life. The more massive a star, the shorter is its life span. Yet, a long stellar life is considered a prerequisite for the development of higher life forms. Therefore the researchers compiled a list of stars that are not only in the advantageous part of the sky, but also offer good chances of hosting evolved forms of life, that is, intelligent life. The researchers compiled a list of 82 nearby Sun-like stars that satisfy their criteria. This catalog can now serve as an immediate target list for SETI initiatives.

But astronomers are far from knowing every star in our Milky Way. The more distant a star, the dimmer its light appears. And the small, particularly long-lived stars are also particularly faint. In order to estimate how many stars in addition to the 82 nearby ones could reside in Earth’s transit zone, Heller and his Canadian colleague Ralph Pudritz projected the celestial sphere onto a model of the stellar density of our galaxy. The result: About 100,000 nearby stars could harbor planets with inhabitants who could have discovered us and who could be trying to contact us.

A part of these planets might be discovered with the PLATO mission of the European Space Agency, scheduled for 2024. René Heller from MPS is also involved in this mission. PLATO will use the transit method to find small planets, some of them possibly Earth-like, around bright stars.

It makes sense to limit the search to those planets that have stars with a long life time, that are near-by and that if aliens existed on them they could observe Earth transiting the Sun. It am surprised the initial list is as small as 82. It might even encourage us to find ways to detect exoplanets on those stars that do not transit their suns.

http://www.space.com/34611-nasa-cass...nd-finale.html

NASA's Cassini has been a busy spacecraft since it arrived at Saturn in 2004. Some of its key discoveries include seeing active water ice plumes at the moon Enceladus, watching strange storms develop in Saturn's atmosphere and (along with the Europe-led lander Huygens) discovering that the enigmatic moon Titan has lakes and seas just like Earth — but composed of methane and ethane, not water. However, all good things must come to an end and the mission is in its last year of operations. Low on fuel, it will make two daring orbital changes to creep closer to Saturn's rings and the planet before plunging into the planet itself. Here are just a handful of things left on Cassini's "to-do" list.

http://www.space.com/34590-saturn-ri...et-pieces.htmlhttp://www.space.com/34590-saturn-ri...et-pieces.html

The rings of Saturn, Neptune and Uranus are composed of pieces of Pluto-like dwarf planets that strayed too close to the giant worlds long ago, a new study suggests.

Astronomers think that thousands of Pluto-size bodies once dwelled in the Kuiper Belt — the ring of frigid objects beyond Neptune's orbit — shortly after the solar system formed. But things changed about 4 billion years ago, the idea goes: At that time, Jupiter, Saturn, Uranus and Neptune migrated a bit, stirring up both the Kuiper Belt and the main asteroid belt between Mars and Jupiter.

The resulting gravitational jostles sent many objects in these two realms careening toward the inner solar system, causing an era of increased cosmic impacts known as the Late Heavy Bombardment.

The "Late Heavy Bombardment" implies there was an "Early Heavy Bombardment".

Yes, and there was an Early Heavy Bombardment.

For links see https://en.wikipedia.org/wiki/Late_Heavy_Bombardment
and
http://www.space.com/2299-insight-ea...mbardment.html

I also wonder about how the purported extinction of the dinosaurs was done. I wonder what kind of meteorite it was. How large and how widespread was the devastation it caused. All the seems very vague. See http://science.nationalgeographic.co...aur-extinction

I also wonder about how the purported extinction of the dinosaurs was done. I wonder what kind of meteorite it was. How large and how widespread was the devastation it caused. All this remains very vague. What kind of an impact would it have been? How big was the object, a small exomoon, perhaps? The dinosaurs were wiped out in the seas, in the air (flying dinosaurs) and on land. See http://science.nationalgeographic.co...aur-extinction. I also note that National Geographic include a gradualist theory as an alternative.

If I remember what Niles Eldredge said in "Extinction and Evolution" correctly, the dinosaurs were becoming weak long before those meteorites hit the earth. Habitat was being lost because the climate was getting colder. This is not to say the volcanoes or meteorites, whatever deposited the layers containing iridium, did not help make the climate colder.

http://www.space.com/34629-nasa-fema...pact-test.html

It's a scary scenario: an asteroid headed for Earth, just four years away from slamming into our home planet. It may be too short a span to plan an asteroid-deflection mission, but it's long enough to present very different challenges from those of a more typical crisis, like a hurricane or earthquake.

"It's not a matter of if, but when, we will deal with such a situation," Thomas Zurbuchen, NASA's Science Mission Directorate's new associate administrator, said in a statement. "But unlike any other time in our history, we now have the ability to respond to an impact threat through continued observations, predictions, response planning and mitigation."

I wonder how different scales of threats can be taken into account. How about an exomoon propelled into a crash with the Earth? Or is this just about asteroids?

There is the movie "Melancholia" that dealt with the theme. In this case the planet Melancholia is much bigger than the earth and the earth will be the asteroid crashing into it. The assumption in the movie is that life existed no where else in the universe but on earth.

If the asteroid landed in deep water, the impact would probably be less than it if landed on land. However, if it landed on land this is one way that global warming might reverse since it should help cool off the climate. However, a good, hard global recession, even without an asteroid, would also stop global warming, at least, the part that we are causing.

There is a possibility that we are getting too close to the Venus zone and although still in the habitable zone where water is liquid, the atmosphere heats up too much. I suspect an array of satellites that reflected the sun's rays back out to space would help in this case.

I found this article on the astronomic basis of "Melancholia". It is an old comment though (2011):
http://blogs.discovermagazine.com/ba...0/meloncholia/

Outlier body incursions reminds me of the sci-fi movie classic "When Worlds Collide" https://en.wikipedia.org/wiki/When_W...de_(1951_film)

The SOCIETY for POPULAR ASTRONOMY
Electronic News Bulletin No. 433 2016 November 6
CURIOUS TILT OF SUN'S AXIS ATTRIBUTED TO PLANET 9

Europlanet Media Centre


'Planet Nine' -- the undiscovered planet that was predicted by astronomers in January this year to exist at the edge of the Solar System -- has been held responsible for the tilt of the Sun's axis,according to a new study. The large and distant planet may be adding a wobble to the Solar System, giving the appearance that the Sun is tilted slightly. The argument goes that, because Planet Nine is so massive and has an orbit tilted with respect to the orbits of the other planets, the Solar System is slowly twisted out of alignment. All of the known planets' orbits lie close to a particular plane, roughly within a couple of degrees of each other. That plane,however, has a six-degree tilt with respect to the Sun, giving the impression that the Sun's axis of rotation is at that angle from the normal to the planetary orbits. Until now, no one had found a good explanation for that. The discovery of evidence that the Sun is orbited by an as-yet-unseen planet that is about 10 times the size of the Earth, in an orbit that is about 20 times farther from the Sun on average than Neptune's, changes the physics. Planet Nine, according to the calculations, appears to orbit in a plane at about 30 degrees from that of the other planets, influencing the orbits of a large popula-tion of objects in the Kuiper Belt, which is how astronomers came to suspect that a planet existed there in the first place.


The tilt of the Solar System's orbital plane has long been a puzzle to astronomers because of the way the planets formed: as a spinning cloud slowly collapsing first into a disc and then into objects orbiting the central star. Planet Nine's angular momentum is having an outsizedimpact on the Solar System on account of its location and size. A planet's angular momentum equals the mass of the object multiplied by its distance from the Sun, and represents the contribution that the planet makes to the overall system's spin. Because the other planets in the Solar System all orbit in practically the same plane, their angular momenta work to keep the whole disc spinning smoothly. Planet Nine's unusual orbit, however, adds a wobble to the system.Mathematically, given the hypothesized size and distance of Planet Nine, a six-degree tilt fits perfectly. The next question, then, is how did Planet Nine achieve its unusual orbit? Though that remains to be determined, it is suggested that the planet may have been ejected from the neighbourhood of the gas giants by Jupiter, or perhaps may have been influenced by the gravitational pull of other stellar bodies in the Solar System's extreme past. For now, astronomers will be searching the sky for signs of Planet Nine along the path that they predicted in January. That search may take some time.

We still have no idea what Planet 9's orbit is, so it could take a long time to locate it and to have some idea of what its orbit can be.

If Planet 9 is not on the ecliptic it would not be where people are expecting it to be.

I don't think the planet in "Melancholia" is likely to exist, but the idea of looking to space for explanations for evolutionary changes on earth may be putting too much expectation on that source. The habitat/climate changes creating challenges for species and thereby allowing evolutionary changes to occur may have explanations that come from the earth itself, that is, volcanoes rather than meteorites.

http://www.universetoday.com/131818/...o-ula-atlas-v/

In a complete change of plans from less than three weeks ago, NASA has asked Orbital ATK to switch rockets and launch the firms next Cygnus commercial cargo freighter to the space station on the tried and true Atlas V rather than their own Antares rocket – which just successfully delivered another Cygnus to the orbiting outpost with a hefty stash of science and supplies.

The altered schedule “provides margin flexibility for the entire Antares workforce” Orbital ATK noted in a statement to Universe Today.

However, the change of events comes as something of a surprise following the spectacularly successful nighttime blastoff of Antares on Oct. 17 with the Cygnus OA-5 resupply ship from the Mid-Atlantic Regional Spaceport at NASA’s Wallops Flight Facility on Virginia’s picturesque Eastern shore – as I reported on from onsite.

I was attracted by the image:
http://www.astronomy.com/news/2016/1...axy-in-the-eye
"If it looks like spiral galaxy IC 2613 is staring at you, it’s not being rude: a collision with its nearest neighbor sent a wave crashing through the galaxy, which produced the strange eye-like structure."...

I wonder how much damage colliding galaxies would have on the life of a planet in one of those galaxies?

You would have to have read Worlds in Collision to begin to understand that. Velikovsky comments on p. 305 under "The subjective interpretation of events and their authenticity".