Tag Archives: density

Mid-Sized Planetary Body in Kuiper Belt Could Float In Water

Planetary scientist Michael Brown from CalTech has measured the density of a planetary body in the Kuiper Belt that is over 400 miles (650 km) wide – and he found that it has a lower density of than water. This is the largest rock discovered in the solar system which would be capable of floating. Brown published the results in The Astrophysical Journal Letters, which appeared online this week.

The body is known as 2002 UX25 and may shake up current theories about how planetary bodies are formed, as it is the first mid-sized body measured for density. Traditionally, it has been believed that planetary bodies were formed by bits of dust whipping around the sun in its infancy. Eventually, the dust particles slammed into one another to form larger rocks. It has been thought that all of the rocky planets formed this way, along with all of the planetary bodies in the Kuiper Belt at the edge of the solar system.

However, if that model was entirely correct then all of the bodies in the Kuiper Belt should have roughly the same density. In fact, smaller bodies are reported to be less dense than water. This was thought to have been reconciled by the idea that the larger rocks have a greater gravitational pull and bring the dust in closer and tighter. Since 2002 UX25 is mid-sized and has a density more similar to a small body instead of one halfway between the small and large as would be expected, there might be something else going on.

Because 2002 UX25 only has a density of about 0.8 grams per cubic centimeter, it is assumed that it contains a great deal of ice. This allowed other planetary scientists to propose a new theory of planetary formation: the solar system was made from the outside in. As the dust flew around creating small rocks, it collected a lot of ice. Larger rocks that had been hit many times had some of the ice knocked out of them, creating a more dense, larger rock. The largest of the proto-planets were drawn inward toward the sun, while the icy remnants remained out at the Kuiper Belt. 

It’s an interesting thought, but several other 2002 UX25-sized planetary bodies will need to be measured before strong assertions of a new theory for formation can be made.

Read more: http://www.iflscience.com/space/mid-sized-planetary-body-kuiper-belt-could-float-water

Newly discovered gassy exoplanet has Earth-like mass

When scientists look for exoplanets out in the Universe, a considerable amount of time is being spent looking for the holy grail – an Earth twin that matches our home in size, mass, and habitability. Most of the exoplanets found so far are much larger than our planet, simply because they are easier to see, but as technology improves and we have more time to analyze data, smaller planets have come to light. A newly discovered planet has just been announced from scientists at the Harvard-Smithsonian Center for Astrophysics: a gassy planet with an Earth-like mass.  A newly discovered planet has just been announced from scientists at the Harvard-Smithsonian Center for Astrophysics: a gassy planet with an Earth-like mass. The paper has been submitted for publication in The Astrophysical Journal, though the results were presented today at the 223rd Meeting of the American Astronomical Society by lead author David Kipping.

The planet KOI-314c is about 200 light years away and orbits a red dwarf star, which has considerably less mass than our sun and belongs to a different spectral class. The planet has an orbit of only 23 Earth days and its proximity to the star puts the surface temperature at an estimated 220 F (104 C). Unfortunately, this is much too hot to sustain the kind of life that we can detect. As a comparison, the highest temperature ever recorded on Earth was 136 F (57.8 C).

The diameter of KOI-314c is about 60 percent larger than Earth, though it is strikingly similar in mass. This is the smallest and lightest planet to have both of these parameters measured. Researchers have been able to deduce that the planet is quite gassy with an atmosphere of helium and hydrogen that could be hundreds of miles thick.

The mass of the planet was determined using a relatively new method called transit timing variations (TTV). It has only been in use since 2010, but allows astronomers are confident that it provides accurate measurements of low-mass planets. As the planet in question transits another planet within the system, the fluctuation in gravity forces the planet to “wobble” slightly and it alters the time it takes a planet to transit, which means it changes the amount of time it takes for the planet to cross in front of the star. The team monitored the light KOI-314c against its neighbor KOI-214b which matches it in size, though it is about four times more dense.

This discovery is exceptionally cool because it wasn’t even what the astronomers were searching for. The team was combing through data obtained from the Kepler Space Telescope in search for exomoons around potentially habitable planets when it came across KOI-314c. Though the team initially reports being disappointed that the planet wasn’t an exomoon, the significance of their discovery more than made up for it.

Read more: http://www.iflscience.com/space/newly-discovered-gassy-exoplanet-has-earth-mass