Astronomy

[Dreamwoven]

A couple of items on the asteroid belt. It lies between Mars and Jupiter.

http://www.universetoday.com/130231/...asteroid-belt/

http://www.universetoday.com/130136/...id-belt-earth/

[YesNo]

I think the theoretical EM Drive is the most interesting way to get to the asteroid belt. However, I don't think we would be able to send humans there, so robotics would have to also advance before it is feasible to mine on the asteroids.

[Dreamwoven]

The Universe Today published an article on how many moons there are in the solar system. You can read the article here: http://www.universetoday.com/15516/h...-solar-system/. The question is not as simple as one might think...

[Dreamwoven]

Earth-like planet discovered around Proxima Centauri: http://www.universetoday.com/130276/...ri-discovered/

[YesNo]

Having an Earth-like exoplanet so close is good news. The article mentioned that the data is at the limit of current measurement abilities. So before sending a nanocraft there we need to improve our ability to measure what is out there.

[Dreamwoven]

Another contribution from Journal of Popular Astronomy:

NEW DISTANT DWARF PLANET BEYOND NEPTUNE
University of British Columbia

Astronomers have discovered a new dwarf planet orbiting in the disc of
small icy bodies beyond Neptune. The new object is about 700 km in
diameter and has one of the largest orbits for a dwarf planet.
Designated 2015 RR245 by the International Astronomical Union's Minor
Planet Center, it was found with the Canada-France-Hawaii Telescope on
Mauna Kea, Hawaii, as part of the ongoing 'Outer Solar System Origins
Survey' (OSSOS). The OSSOS project uses computers to hunt for the
images, and the team was presented with a bright object moving at such a
slow rate that it was clearly at least 120 times further from the Sun
than the Earth. The size of RR245 is not yet exactly known, as its
surface properties need further measurement. The vast majority of dwarf
planets like RR245 were destroyed or thrown from the Solar System as the
giant planets moved out to their present positions. RR245 is one of the
few that survived to the present day, along with Pluto and Eris, the
largest known dwarf planets. RR245 now circles the Sun among the remnant
population of tens of thousands of much smaller trans-Neptunian bodies,
most of which orbit unseen. RR245 has been on its highly eccentric orbit
for at least the last 100 million years. After hundreds of years further
than 80 astronomical units (AU) from the Sun, RR245 is travelling towards
its closest approach at five billion km (34 AU), which it will reach
around 2096. As RR245 has been observed for only one of the 700 years it
takes to orbit the Sun, where it came from and how its orbit will slowly
evolve in the far future is unknown. Its precise orbit will be refined
over the coming years, after which RR245 will be given a name. As
discoverers, the OSSOS team can submit their preferred name for RR245 to
the International Astronomical Union for consideration. RR245 is the
largest discovery and the only dwarf planet found by OSSOS, which has
discovered more than five hundred new trans-Neptunian objects.

This will take 700 years to orbit the sun. Planet 9 a giant planet which would orbit the sun in 10,000 to 20,000 years, looks increasingly unlikely.

[YesNo]

Pluto is about 2370 km in diameter: http://www.space.com/18568-how-big-is-pluto.html So 700 km is pretty small.

This could be on the lower edge of what constitutes a dwarf planet although having enough gravity to have a spheroidal shape is what counts: https://www.spaceanswers.com/solar-s...-dwarf-planet/

[Dreamwoven]

That's true, YesNo. Many are still smarting from the demotion of Pluto from a planet to a dwarf planet. Ceres is also a dwarf planet, spheroid, but without any moons of its own, unlike Pluto.

[Dreamwoven]

Cassini is still orbiting the only moon (Saturn's Titan) with extensive regions of open seas. See http://earthsky.org/space/saturns-mo...looded-canyons

[Dreamwoven]

The SOCIETY for POPULAR ASTRONOMY

Electronic News Bulletin No. 427 2016 August 14

Also has a post on the above,more detailed. Copied it below:

CASSINI FINDS FLOODED CANYONS ON TITAN
NASA

The Cassini spacecraft has found, on Saturn's large moon Titan, deep,
steep-sided canyons that are flooded with liquid hydrocarbons. The
finding represents the first direct evidence of the presence of liquid-
filled channels on Titan, as well as the first observation of canyons
hundreds of metres deep. The Cassini observations reveal that the
channels -- in particular, a network of them named Vid Flumina -- are
narrow canyons, generally a bit less than a kilometre wide, with slopes
steeper than 40 degrees. The canyons also are quite deep -- those
measured are 240 to 570 metres from top to bottom. The branching
channels appear dark in radar images, much like Titan's methane-rich
seas. That suggested to scientists that the channels might also be
filled with liquid, but a direct detection had not been made until now.
Previously it was not clear if the dark material was liquid or merely
saturated sediment -- which at Titan's frigid temperatures would be made
of ice, not rock. Cassini's radar is often used as an imager, providing
a window to see through the dense haze that surrounds Titan to reveal the
surface below. But during a recent pass, the radar was used as an
altimeter, sending pings of radio waves to the moon's surface to measure
the height of features there. The researchers combined the altimetry
data with previous radar images of the region to make their discovery.

The key to understanding the nature of the channels was the way Cassini's
radar signal reflected off the bottoms of the features. The radar
instrument observed a glint, indicating an extremely smooth surface like
that observed from Titan's hydrocarbon seas. The timing of the radar
echoes, as they bounced off the canyons' edges and floors, provided
direct measures of their depths. The presence of such deep cuts in the
landscape indicates that whatever process created them was active for a
long time or eroded down much faster than in other areas of Titan's
surface. The researchers' proposed scenarios include uplift of the
'terrain' and changes in sea level, probably both. It is likely that a
combination of those processes led to the formation of the deep canyons,
but it is not clear to what degree each was involved. What is clear is
that any description of Titan's evolution needs to be able to explain how
the canyons got there. Terrestrial examples of both of those types of
canyon-carving processes are found along the Colorado River in Arizona.
An example of uplift powering erosion is the Grand Canyon, where the
terrain's rising altitude caused the river to cut deeply downward into
the landscape over the course of several million years. For canyon
formation driven by variations in water level, look to Lake Powell. When
the water level in the reservoir drops, it increases the river's rate of
erosion. While the altimeter data also showed that the liquid in some of
the canyons around Ligeia Mare is at sea level -- the same altitude as
the liquid in the sea itself -- in others it sits tens of metres higher
in elevation. The researchers interpret the latter to be tributaries
that drain into the main channels below. Future work will extend the
methods used in this study to all the other channels that Cassini's radar
altimeter has observed on Titan. The researchers expect their continued
work to produce a more comprehensive understanding of forces that have
shaped Titan's landscape.

[YesNo]

It is interesting that the terrain needs to rise as the water erodes the surface for the canyons to get as deep as they are. That sort of makes sense. I normally think of the process as just the effect of water rather than the rising ground.

[desiresjab]

It is interesting that the terrain needs to rise as the water erodes the surface for the canyons to get as deep as they are. That sort of makes sense. I normally think of the process as just the effect of water rather than the rising ground.

What would happen if the fluid keeps digging but the ground does not rise?

[YesNo]

What would happen if the fluid keeps digging but the ground does not rise?

It would take a longer time to dig the same size hole because more ground further along the water way would have to be moved out of the way.

[Dreamwoven]

http://earthsky.org/brightest-stars/...ars-to-be-seen

[YesNo]

I remember watching Deneb as the Swan constellation descended into the waters of Green Bay last autumn. I was sheltered by a warm cabin and with a large window facing south-west. Nice sunsets as well.

What amazes me is the margin of error reported in the article. Deneb could be between 1425 and 7000 light years away. That means that other estimates, including those about its size, should have similar ranges.