Date: July 25, 2011

Title: A Planet is a Peculiar Place

Podcaster: Maurizio Morabito

Organization: Omnologos Ltd

Description: Wondering about the wonderful wanderers.

Bio: Maurizio is an experienced electronics and computing technologist and scientist, and published journalist and technical and scientific author in English and Italian with a variety of interests, including the study of international relations, economic and social development factors, the energy sector and space technologies. Maurizio has recently been accepted as Fellow of the British Interplanetary Society, the world’s longest established organization devoted solely to supporting and promoting the exploration of space and astronautics.

Sponsor: Today’s podcast is sponsored by Omnologos Ltd, on its quest to find sponsors for a major scientific experiment on the International Space Station. And it is dedicated to Lorenzo: may you take me to the Moon, one day!

Transcript:

Hello and welcome to another podcast by Omnologos. My name is Maurizio Morabito. Today’s topic is…what is a planet. We know of course there’s been quite a controversy since the decision in 2006 by the International Astronomical Union about the definition of a planet.

This controversy most likely will never stop. One thing to remember is that the decision at the time was inspired by the fact that more and more so-called planets were being discovered.

However the number of planets should be inconsequential with regards to the decision of what a planet is. Nobody wll think to find a new definition of a star so that only 8 of them are considered as such. If one planet is in the solar system or one hundred of them, this should be a consequence of what the solar system is.

Another point that particularly striking at the time was that somebody said that a planet like Pluto was demoted to “dwarf planet”. I do find this definition “idiotic” apart from being quite non-politically correct. In fact if we think that to become a dwarf planet is to be demoted as a planet, means that we’re suggesting only the big things in the sky are important and everything else, everything small is of a lesser interest. We know that this is not true. Mars is not less interesting than Earth even if it is much smaller. Think also about Mercury, or tiny Pluto.

Think also of the fact that the Sun itself is defined as a dwarf star.
Who’s going to go around saying that the Sun is not an interesting thing to examine.

All of this actually points the way towards a different understanding of what a planet is. As they say, we know what is a planet is because if we see one then we can tell it is a planet instead of, say, a satellite or an asteroid. What is behind this? Behind this is the fact that planets are interesting places. If we see where we have sent probes in the solar system, that in itself should tell us what we consider actually, a “planet”. In other words a planet is a peculiar place. Every planet we know of, has something very strange about it.
And so it is worth visiting, unique enough to warrant close-up investigation.

What are these peculiarities I am talking about? Think of any planet and then a lot of strange descriptions will come.

For example in the case of MERCURY we see that it is a very dense planet, so dense that somebody says it is an almost-naked core.

Mercury is also the only place where we can see Relativity at work with the changes in its orbit. Furthermore on Mercury one day is actually as long as two years, This means that the Sun rises in the East, as usual, then around mid-day it goes back to the East a little bit, it stops again and then goes to the West. Now let’s think of

VENUS: Venus has the densest atmosphere, it is upside down (that means, it’s rotating clockwise as seen from the North Pole of the Sun, instead of counterclockwise like every other place in the solar system. Venus has no magnetic field and its surface has been completely resurfaced sometimes like 500 mllion years ago. Temperaturs on the surface of Venus are very high but the winds are extremely slow. There is a lot to say about Venus…maybe it’s the strangest place in the solar system.

Think of EARTH where there is liquid water at the surface, there is plate tectonics and that strange chemical fire that is called “life”.

MARS: on Mars there are worldwide storms even if the atmosphere is very very thin. It has the largest canyon, the largest volcano and the largest plain relative to the planet’s size in the entire solar system.

JUPITER: giant magnetic field and there is one long-duration storm, and when we have sent a probe with the Galileo mission inside the atmosphere we didn’t find the water we were expecting.

SATURN:
famous for its rings, the number of moons (there’s 63 or even more), it has a superstorm that is so big it has encircled the planet (it has caught on itself around the planet).

The moon of Saturn, Titan, is the only moon with an atmosphere, and there is a strange, strange cloud pattern, an hexagonal cloud pattern at the North Pole. URANUS is rolling around the orbit, it’s featureless, at least the atmosphere looks featureless but it has a very peculiar magnetic field that ends up doing like some corkscrew magnetotails. The tail of its magnetic field is wound up on itself.
There are extreme seasonal changes, however the winds are not as fast as on Neptune. NEPTUNE has winds that are running at 2,000 kph It also has incomplete rings that are now fading but most likely they keep forming and fading and forming again.

PLUTO: this is something for New Horizon. For now we know it’s a strange place because it’s a binary system where the biggest satellite is so large that the center of gravity of the system is between Pluto and Charon. Also we know that Pluto has a highly-contrastive surface.

Some part of it is very black, some part of it is very white and some part of it is very orange. VESTA has just been reached by the Dawn spacecraft. It has such a giant crater at the South Pole that a large number of meteorites that have reached Earth are coming we know from this so-called asteroid, what I would say is a planet.

Finally the next stop for Dawn is the large asteroid now called a dwarf planet CERES. That is going to be a very strange place too. We know that also because the Hubble Space Telescope has imaged some bright spot, very bright spot on it.

Every extrasolar planet also is a very strange place. Some of them are extremely close to their star and then they become extremely hot. Some of them are tidally locked with the star so there must be one point on them that must be at a temperature we cannot even imagine. Some of them are also in very strange orbits. And so on and so forth.

So we can go back to this new definition of what is a planet. A planet is an object in the solar system that we have investigated, or are investigating, or are planning to investigate because of its uniqueness, rather than, say, being a representative of a class of objects like a small asteroid would be. The only conditions I would keep, is that a planet is not a star or a brown dwarf, a planet does not orbit around another planet, and (mostly, for historical reasons) a planet has or has had at some point in its history a quasi-spherical shape.

A planet is really a peculiar place: because the planets are the wanderers, and for us the planets are also the inspiration of wonder.

Thank you for listening. This is another podcast by Omnologos.

End of podcast:

365 Days of Astronomy
=====================
The 365 Days of Astronomy Podcast is produced by the Astrosphere New Media Association. Audio post-production by Preston Gibson. Bandwidth donated by libsyn.com and wizzard media. Web design by Clockwork Active Media Systems. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. Until tomorrow…goodbye.