Daily Archives: March 19, 2017

Space Sunday: 100+ planets, taking a balloon to orbit, and budgets

A chart showing the to-scale sizes of two planets, 19 moons, 2 asteroids, and 87 trans-Neptunian objects, all of which could technically be considered planets orbiting our Sun. Credit: Emily Lakdawalla. Data from NASA / JPL, JHUAPL/SwRI, SSI, and UCLA / MPS / DLR / IDA, processed by Gordan Ugarkovic, Ted Stryk, Bjorn Jonsson, Roman Tkachenko, and Emily Lakdawalla

When is a planet not a planet – or more precisely, when should what is not regarded as a planet be a planet?

Right now, according to the International Astronomical Union (IAU), our solar system comprises eight formally recognised planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. That’s been the case since 2006, when the IAU opted to classify bodies orbiting the Sun in three ways:

  • As planets – defined as a) celestial bodies that (a) are in orbit around the sun; b) have  sufficient mass for their self-gravity to overcome rigid body forces so they assume a hydrostatic equilibrium (nearly round) shape; c) have cleared the neighbourhood around their orbit of other objects
  • As Dwarf planets – defined as celestial bodies which a) orbit the sun; b) have sufficient mass for their self-gravity to overcome rigid body forces to assume hydrostatic equilibrium (aka “is nearly round” in shape);  c) have not cleared the neighbourhood around their orbit; and d) is not a natural satellite
  • As Small Solar System bodies:  all other objects except satellites orbiting the Sun.

A composite image showing Pluto and Charon to scale to one another (but not at a scale separate from one another) using images returned by the New Horizons mission. Credit: NASA / John Hopkins University APL / SwRI

Thus, since 2006, Pluto has been a dwarf planet. However, moves are afoot to get things changed – and not just for Pluto.

In a paper authored by planetary scientists involved in the New Horizons mission which zipped through the Pluto system in July 2015, there is a call for the term “planet” to be redefined; if not by the IAU then at least in popular use. Should it happen, it could see the number of planets in the solar system leap from 8 to over 100.

The scientists argue that the IAU definition of “planet” focuses only on the intrinsic qualities of the body itself, rather than external factors such as its orbit or other objects around it. In fact, under the IAU’s definition, Earth, Mars, Jupiter and Neptune don’t actually qualify as “planets” as none meet the third criteria (c) – Earth, for example, has regular “close encounters” with asteroids which cross its orbit. Instead, the team offer a simpler definition:

A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has enough gravitation to be round due to hydrostatic equilibrium regardless of its orbital parameters.

Such a definition would mean that Pluto could regain its planetary status – as would the proto-planet (or small solar system body) Ceres, the dwarf planets of 136199 Eris (discovered in 2005, and the trigger-point for Pluto’s “downgrading”) , 136472 Makemake, and 136108 Haumea, together with (possibly) 50000 Quaoar, 90377 Sedna, 90482 Orcus and a host of trans-Neptunian objects tumbling around the Sun. Nor is that all; the new definition would also mean that the likes of  Jupiter’s Galilean moons, Saturn’s Titan and  Enceladus, Neptune’s Triton and many other bodies we regard as “moons” would be lifted to planetary status – including our own Moon.

A composite image using data gathered by the radar imager aboard NASA’s Cassini mission to Saturn to look through the normally opaque haze of Titan’s dense atmosphere to reveal its planet-like surface. Credit: NASA/JPL / University of Arizona

The paper proposing the change will be presented at the Lunar and Planetary Science Conference on March 20th to 24th, 2017 in Texas. And it has already come in for some criticism.

Mike Brown is the scientist largely behind Pluto’s demotion. Currently engaged in the search for the elusive “Planet Nine”, he (somewhat harshly) sees the efforts of the New Horizons team to get Pluto reclassified as being  about them wanting the prestige of having run a planetary mission, more than anything else.

However, there are valid reasons for seeking some kind of change, even if it is only informal. One is as basic as gaining more public interest in efforts to explore and understand the many environments found on planets and moons alike within our solar system.

“Every time I talk about this [the science and data gathered about Pluto by New Horizons] to the general public, the very next thing people say is ‘Pluto is not a planet any more’,” said Kirby Runyon, the lead author of the paper. “People’s interest in a body and exploring it seems tied to whether or not it has the name ‘planet’ labelled on it.”

How Pluto compares with other large Trans-Neptunian Objects, some of which also have their own moons. Earth and our moon can be seen at the bottom of the picture. Credit: Lexicon / Wikipedia, using NASA / Hubble Space Telescope data

There are scientific reasons for the definition to be broadened as well. Places like Pluto, Ceres, Europa, Io, Ganyemede, Callisto and Triton all evidence geophysical, hydrothermal, atmospheric and other characteristics very much in keeping with bodies such as Earth, Mars, and Venus. They are thus of exceptional interest to planetary scientists the world over. In fact, many of them (like Pluto) are completely re-writing our understanding of “planetary bodies”.

Ultimately, the team behind the paper aren’t going to put their proposal before the IAU for a change in the “official” definition of “planet”.  “As a geophysical definition, this does not fall under the domain of the IAU, Runyon notes, “[It]  is an alternate and parallel definition that can be used by different scientists. It is “official” without IAU approval, partly via usage.”

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Journey of Life in Second Life

Paris METRO: Journey of life

Journey of Life is the title of a new exhibition of art by Satus Voltz (satus9), which opened at the Paris METRO Art Gallery on Saturday, March 18th. In terms of broad theme, it in some ways continues and extends the examination of life seen in the previous exhibition at the gallery, Life Is A Journey by Elin Egoyan (which you can read about here). However, where Elin considered our physical lives in her exhibition, Satus here considers time and travels through Second Life.

Twenty-three pieces of art are offered for display. They offer both an intriguing presentation of evocative individual pieces and a finely balanced collection when taken as whole, bringing together a number of subtle pairings, from the balance between monochrome and colour in the landscapes, through the use of either anticipation or pensiveness as an emotional driver in the avatar studies or the subtle mixing of purely 2D images with those with a 3D aspect; all the way through to the mix of landscapes and avatar-focused  images. In short, this is a richly diverse collection of pieces which are not only encapsulated within the overall theme, they beautifully demonstrate Satus’ artistry and expression.

Paris METRO: Journey of life

The use of 3D elements with a 2D art display perhaps isn’t new. Several artists  – notably Molly Brown – have incorporated 2D and 3D art into a single whole in the past; and on entering the gallery to encounter Shattered (in the foreground of the banner image at the top of this piece), I was immediately put in mind of her work. However, the sheer dynamism and narrative in Shattered is breathtaking. Elsewhere, the use of a 3D element is more subtle but no less emotive and effective; from starlight filtering through the fan of branches of distant trees, to the fall of rain or the use of dandelion seeds and dust motes drifting through the air.

Then there is balance between monochrome and colour in the landscape pieces, which brings a certain harmonic tension to them. We are at once drawn towards the three black-and-white images sitting among their more numerous colour companions, but at the same time, they encourage is to consider the use of colour as well as light and shade within the colour pieces.  A similar tension can be found within the more avatar focused studies. Within these, the pensiveness within pieces like Departure, Burning House (both of which are shown below), and I Don’t Wanna Live Forever, is countered by the depth of anticipation evidenced in Silent Awakening, Polar Express and Confetti of The Sky, with both emotions perfectly brought together in  Can’t Take You With Me.

Paris METRO: Journey of life

Evocative, emotive, beautifully (and naturally) composed, the images in this exhibition are utterly entrancing and perfectly set within an environment accented by Satus. Absolutely not to be missed.

SLurl Details

Mysteries, aliens, mice and poems

It’s time to kick-off another week of storytelling in Voice by the staff and volunteers at the Seanchai Library. As always, all times SLT, and events are held at the Library’s Second Life home at Bradley University, unless otherwise indicated.

Sunday, March 19th 13:30: Tea Time Mysteries!

Seanchai Library launches a Tea Time series, featuring everything non-Holmesian from Christie to Hamett, classic sleuthing to hard-boiled detectives of the noir-ish hue.

This week: more Agatha Christie with Caledonia, Kayden, Corwyn and John.

Monday, March 20th 19:00: Enemy Mine

Gyro Muggins continues reading Barry B. Longyear’s novella which first appeared in a 1979 issue of Isaac Asimov’s Science Fiction Magazine, before becoming the basis of the of the 20th Century Fox film of the same name, starring Dennis Quaid  and Louis Gossett, Jr. This led to Longyear producing an expanded version of the story, written with David Gerrold.

In the midst of an interstellar war between humans and Dracs (a race of humanoid reptilians), Willis Davidge, a human fighter pilot, crashes on a hostile planet after a dogfight with a Drac – who is also forced down on the same planet.

The two initially continue their hostilities towards one another. But the planet proves so hostile that Davidge and the Drac, Jeriba Shigan (whom Davidge nicknames “Jerry”), are forced to join forces in order to ensure their survival. Then Davidge learns Jeriba is pregnant – Drac being entirely asexual …

Tuesday, March 21st 19:00: Of Mice and Magic

Faerie Maven-Pralou reads the forst in the Ravenspell series by David Farland

More than anything, Benjamin Ravenspell wants a pet. But when he buys a mouse named Amber, he gets more than he bargained for. No sooner does Ben take her home, than Amber turns him into a mouse too.

You see, Amber has magical abilities, and it so happens that Ben is a familiar, a creature that stores magical energy. Together they each form half of a powerful wizard. Alone, they’re just vermin.

Soon Ben and Amber find themselves pitted in an epic battle against a magical enemy who is as crazed as he is evil, and the fate of the world will rest on them learning to work together.

Wednesday, March 22nd 19:00: Poems Aloud

With Caledonia.

Thursday, March 23rd

19:00: From The Hearth

Celtic Darkness, Tales from the otherworld with Shandon Loring (also presented in Kitely, and InWorldz).

21:00 Seanchai Late Night

With Finn Zeddmore.

Sunday March 26th: Volume IX

Senchai Library’s anniversary celebrations, licking-off at 13:00 SLT. More details in my preview next week!


Please check with the Seanchai Library’s blog for updates and for additions or changes to the week’s schedule.

The featured charity for March April is Project Children, building peace in Ireland one child at a time.