Astronomy

[YesNo]

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.

[Dreamwoven]

I guess we will see how the work being done on Ceres will be improved by the one year extension of the visit.

[Dreamwoven]

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.

[YesNo]

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.

[Dreamwoven]

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.

[YesNo]

It looks like tens of billions of potentially habitable planets in the Milky Way.

[Dreamwoven]

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...

[Dreamwoven]

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).

[YesNo]

It seems that Snow White should have been nicknamed Rose Red. The oblong shape of Haumea is also unusual.

[Dreamwoven]

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.

[YesNo]

I wonder how those Manx comets got out that far. Perhaps the inner planets kept pushing them away rather than attracting them.

[Dreamwoven]

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?

[YesNo]

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.

[Dreamwoven]

I've never heard of that myself. I don't suppose you can cite a reference...

[YesNo]

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.