Category: Astronomy

Well, the votes were counted and the decision made: Pluto was demoted to less than planetary status. The astronomy and science textbook publishers are rubbing their hands with glee as new editions will have to be printed and plucked from their shelves by eager homeschoolers and teachers keen to get their facts right.

Unfortunately, things are never so clear cut.

A fierce backlash has begun against the decision has begun, says the BBC. The lead scientist on NASA’s robotic mission to Pluto, Alan Stern, called the ruling “embarrassing”, while the chair of the committee, Owen Gingerich, implied that the vote had been “hijacked”.

http://news.bbc.co.uk/1/hi/sci/tech/5283956.stm

It seems, however, that many of those arguing against the demotion of Pluto to dwarf planet status had already left the meeting because of other commitments before the final voting took place. Indeed, only 10% of the 2700 delegates at this meeting actually voted!

Gingerich, was among the 90% who couldn’t vote as he had to return to the US. He says electronic balloting must be introduced in the future. Stern too was unable to vote, “I was not allowed to vote because I was not in a room in Prague on Thursday 24th. Of 10,000 astronomers, 4% were in that room – you can’t even claim consensus,” he told the Beeb.

This left the anti-Plutonists with an open field to throw this tragic rock into a lower orbit.

Stern expressed even further consternation but added that he could not see the resolution standing for very long and wasn’t planning on editing the manuscript for his forthcoming astronomy textbook just yet.

Caltech’s Mike Brown, co-discoverer of UB313 is quite happy to live in a solar system with just eight planets thought. “Eight is enough,” he told the Associated Press, jokingly adding: “I may go down in history as the guy who killed Pluto.”

Whichever way the solar count finally goes, it seems that the arguments are adding a frisson to astronomy that has been sadly lacking for many years. Even if the textbooks stay the same, bookshops would be well advised to stock up early for the Christmas rush as a whole new wave of budding astronomers clamber for space books and maps of the night skies.

Astronomers working under the proverbial umbrella of the International Astronomical Union (IAU), have come up with a new definition of “planets” and smaller “solar system bodies” such as comets and asteroids, this week, but the definition is not without controversy.

If the definition is approved by the astronomers who are pointing their telescopes at each other at the IAU General Assembly in Prague, this week, then our Solar System will have 12 not nine planets, with more to come.

Our heavenly neighbours will be the eight classical planets that dominate the system, including Pluto, whose status hung in the balance for a while. But, there will be an additional three planets in the new burgeoning category of “plutons” described as Pluto-like objects — and Ceres. Pluto will at the time of writing remain a planet but be the prototype for the new category of “plutons.” Anything smaller than Pluto but with similar properties, presumably, will become a pluton rather than a planet.

With the advent of powerful new telescopes on the ground and in space, planetary astronomy has gone though an exciting development over the past decade. For thousands of years very little was known about the planets other than they were objects that moved in the sky with respect to the background of fixed stars. In fact the word “planet” comes from the Greek word for “wanderer”. But today hosts of newly discovered large objects in the outer regions of our Solar System present a challenge to our historically based definition of a “planet”.

The new definition accommodates the eight bodies from Mercury to Neptune and Pluto because they orbit a star and aare in “hydrostatic equilibrium,” which basically means they’re “almost round.”

Not everyone is happy with the new definition. Caltech’s Mike Brown co-discoverer of UB313 (aka Xena) is appalled by the notion that there could be many more than the “special” nine planets orbiting our sun. Estimates put the figure at 53 round objects are already known.

He told the Globe and Mail, that ‘To me, the word ‘planet’ always meant something special. Nine was special. Maybe 10. Fifty-three? No,…in some ways it drains the excitement of what I thought was an exciting find. Turns out it was the 12th planet. Who knew?’

Moreover, a counter definition that knocks Pluto off the list altogether is being mooted by rebel astronomers at the same meeting, according to New Scientist. This version tacks on the idea that to be a planet the object must be the dominant heavenly body in its orbital region. Unfortunately for Pluto, Neptune (not to mention Uranus) is much bigger and their orbits cross…so Pluto would, according to The Register, be planet-ish but not quite planetary.

Final voting will take place Thursday.

But, never mind the astronomers’ concerns, what are astrologers making of all this? Surely, their charts will all have to be redrawn if Xena is in the ascendent and Pluto on the decline! Maybe in the Age of Aquarius we shouldn’t be worrying about such trivia as planetary definitions and get back to solving other more pressing matters here on earth.

It might seem like a trivial question, and most people would probably say 28 days. But, it isn’t so simple.

On average it takes 27.322 days (that’s a sidereal month, and a nice number of significant figures for something astronomical, especially when defining the day is not so clear cut) for the Moon to complete one orbit around Earth. However, the number of days between Full Moons is about 29.5306 days as the Moon has to “catch up with the sun” as it were. So, the actual number of days may differ from the average number by more than a half day. From one Full Moon to the next, the number of days in one lunation can vary between 29.272 and 29.833 days (another nice clutch of significant figures).

The age and apparent size of the Full Moon vary in a cycle of just under 14 synodic months, which is called the Full moon cycle.

The true Full Moon may differ from the calculated peak by up to about 14.5 hours, due to the normal irregularity in the Moon’s Keplerian orbit, and due to the periodic perturbations in that orbit caused by the Sun, the equatorial bulge of the Earth, and the proximity of other planets.

Anyway, I hope this little snippet answer the search query a recent visitor plugged into the sciencebase search box – “moon orbit earth how long”

The environmental impact of black holes is perhaps a distant and esoteric concept, unless you’re waiting for part 2 of the latest Doctor Who story, but US astronomers have used the latest observations of nine black holes with NASA’s Chandra X-ray Observatory to estimate directly the efficiency of black holes. Their calculations show that black holes are perhaps the most fuel efficient engines in the universe, with a remarkably high fraction of the energy they consume being converted into work. Read on in the latest issue of our physical sciences webzine – Spotlight.

There’s an interesting feature article by Frank Schaefer in the latest issue of ERCIM News (No. 65, Apr 2006) all about space junk. Schaefer points out that the historic practice of abandoning spacecraft, rocket stages, and defunct satellites has led to something like 2000 tonnes of debrit accumulating in earth’s orbit. He produces a diagram showing the catalogued distribution of this junk, much of which is in the form of tiny, but incredibly fast-moving particles.

Obviously, it is a real concern for anyone sending up new equipment as these high-energy particles can rip through equipment and space-suits with rather inconvenient results.

The caption for a photo showing a piece of irreperably damaged circuitry says it all: Degradation of computer performance follwed by cease of operation shortly after encounter of the hypervelocity particle”.

Why they had to say it in such a flamboyant way, I don’t know.

Like an adolescent unfortunate, Jupiter has got spots and it’s all down to climate change. The latest images from the Hubble space telescope reveal details of the second red spot that formed in the atmosphere of the gas giant.

This dramatic change to the Jovian weather, nicknamed most unimaginitavely, Red Spot Jr., will provide planetary scientists with an unprecedented chance to study the storms and climate of our solar system’s largest planet. RSJ was formed as a white oval between 1998 and 2000 when three white storms merged, but Hubble’s latest snaps reveal that the planet’s climate is changing. When viewed at near-infrared wavelengths (specifically 892 nm – a methane gas absorption band) RSJ is almost as prominent in Jupiter’s cloudy atmosphere as the Great Red Spot. This may mean that the storm rises miles above the top of the main cloud deck on Jupiter just as its larger cousin is thought to do. Some astronomers think the red hue could be produced as the spots dredge up material from deeper in Jupiter’s atmosphere, which is then chemically altered by the Sun’s ultraviolet light.

A vast cloud of methyl alcohol, spanning some 463 billion kilometres and wrapped around a stellar nursery could help astronomers explain the formation of some of the most massive stars in our galaxy. Lisa Harvey-Smith revealed details of the observations at the Royal Astronomical Society’s National Astronomy Meeting on 4th April.

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David Bradley turns the spotlight on the astronomical revelations in this month’s Spotlight physical sciences webzine

The strongest magnetic fields in the universe have been simulated on the computer by researchers in the UK and Germany. The fields, which are thousand million million times stronger than the magnetic field of the Earth are produced when two magnetised neutron stars collide. Theory suggests these fields could be the source of violent gamma-ray burst explosions.

Neutron stars have a mass similar to that of our Sun but are just 20 km across, which makes them denser than atomic nuclei. According to the theory of general relativity, two neutron stars orbiting each other will ultimately collide violently.

Daniel Price of the University of Exeter, UK and Stephan Rosswog from the International University of Bremen, Germany, revealed their simulations of this processat at the Royal Astronomical Society’s National Astronomy Meeting on 5th April and at the Ringberg-conference on Nuclear Astrophysics on the 7th April. The results are also published today in Science Express.

“It is only recently that we have the computing power available to model the collisions and take into account the effects of magnetic fields,” explains Price, “It has taken us months of nearly day and night programming to get this project running,” he adds. Everyday magnetic fields produced by domestic electrical products such as the pump in a refrigerator are about 100 Gauss, says Rosswog. The colliding neutron stars produce a field an incredible 10 million million times stronger.

In the supercomputer simulations, Price and Rosswog show that within the first millisecond of the collision, magnetic fields are produced that are stronger than any other magnetic field that is known in the Universe. The calculations are a computational challenge because they include a lot of exotic physics, including effects of high-density nuclear physics, particle physics and General Theory of Relativity. To calculate only a few milliseconds of a single collision takes several weeks on a parallel supercomputer.

Scientists have long suspected that such a collision may be at the heart of some of the brightest explosions in the Universe since the Big Bang, so-called short gamma-ray bursts. Recent detections of ‘afterglows’ of such bursts have confirmed this idea, but much of the physics behind these explosions still lies in the dark. (Boom, Boom!)