Archive for the 'astronomy' Category

From Dwarf Planets to Hobbit Galaxies

Published
by
Clifford
on August 28, 2006
in astronomy, dark matter, galaxies and science
. 6 Comments

dwarf galaxyI learned from an article in New Scientist by David Shiga that there have been recently found four more small satellite galaxies of our Milky Way galaxy.

The satellites are dwarf galaxies a few hundred to a few thousand light years across. The tiny galaxies are thought to be the building blocks of large galaxies, such as our own Milky Way – which is about 100,000 light years wide.

As you may know, we’ve known for some time that there have been such satellites (the number knwon has gone from 10 to 20 in the last two years, and some models expect as many as 50), but the small ones are very hard to detect. How do you distinguish them from other stars in the way? As part of the Sloan Digital Sky Survey (SDSS), the researchers have been looking for….

the particular types of stars expected to lie in dwarf galaxies, then detect the dwarfs as slight “overdensities” in these types of stars – patches of the sky where there are more of the stars than in surrounding areas.

The Cambridge team named them after the constellations in which they were found:

[...] Coma Berenices, Canes Venatici II, Hercules, and Leo IV, all of them lie between roughly 100,000 and 500,000 light years from Earth.

[...]The largest and smallest are Hercules and Coma Berenices, which are about 1000 and 200 light years across, respectively. Like most of the other dwarfs discovered by SDSS, the new finds are much smaller and fainter than the 10 dwarfs that were known previously, [Vasily] Belokurov [the team leader] says. “They should not really be called dwarfs – they are more like hobbits,” he told New Scientist.

Hobbits. Right. Does that make the Milky Way a Cave Troll? Or maybe a Numenorian? (Picture above is one of them. This one’s Farmer Maggot, I think. They’re not as Continue reading ‘From Dwarf Planets to Hobbit Galaxies’

The Lighter Side of Pluto…

Published
by
Clifford
on August 25, 2006
in astronomy and humour
. 7 Comments

…And from serious protests of the previous post to humourous (fictional!) ones.

Go check out the Worth1000 photoshop competition on the subject, linked here.

Some of them are great! Here’s one I liked:

worth 1000 pluto competition

Creator’s caption: “Don’t argue with him, the man’s a genius.”

-cvj

A Glimmer of Hope for Pluto?

Published
by
Clifford
on August 25, 2006
in astronomy, planets and science
. 20 Comments

So despite the announcement yesterday, reliable sources tell me that some members of the astronomy community are hoping that there is still maybe a small window of opportunity for Pluto.

Some members of the community are preparing a petition which protests the IAU planet definition! They don’t agree with the decision, and point out that a rather small percentage of the astronomical community actually voted at the Prague IAU. They give the following additional reasons for their questioning of the decision:

They say that the community voted….

… for a definition of ‘planet’ that uses dynamics (location) rather than intrinsic properties to decide if an object is or is not a planet. This result is counter to other classification schemes in astronomy (e.g., stars, galaxies, nebulae, even asteroids) in which dynamical context does not play a controlling role. Furthermore, it produces results that are incongruous and cannot be extended within our own solar system or to extra-solar planetary systems without producing immediate results that are patently absurd: e.g., a Neptune-sized object discovered beyond 150 AU could not be a planet, the presence of an Earth orbiting its star between a Jupiter and a Saturn would mean the Earth could not be considered a planet since it could not clear its “neighborhood”. This definition also excludes Pluto from planethood in our solar system, something that is both scientifically questionable and publicly problematic. Both Pluto and a distant Neptune would be classified as a “dwarf planet”, which is not to be considered a subcategory of “planet”.

The petition is to be among the community only, so I will not give you details about how to sign it. Also, I don’t know if I have permission to reveal the names of the people who put forward the petition, so I will not do that, at least until I know more.

This is rather unexpected and quite interesting, I hope you agree.

-cvj

Spinach Blogging

Published
by
Clifford
on August 24, 2006
in astronomy, dark matter, planets, science, science education and science in the media
. 8 Comments

I learned a new term from a producer at a television studio the other day (in a context I do not know if I’m allowed to blog about yet): “Spinach TV”. I love it. This is a term expressing the idea of television programming that is supposed to be “good for you” since it is educational in some way. Some of us are doing this sort of thing in the blogging world, for better or worse. See my about page.

With that in mind, I’d like to offer some words about this week’s science coverage of the two big Astronomy/Astrophysics stories. I’ve heard the issue raised a number of times today (including by my colleague Sean over on CV) that it is somehow to be thought of as a bad thing that there’s more coverage in the press of the Pluto demotion than there is of the new results giving new direct evidence of Dark Matter. The former is supposed to be all about the politics of science while the latter is supposed to be covered more since it is a profound new result.

With all due respect to my friends and colleagues who have expressed that opinion, I would say that such a view is somewhat short-sighted and has more than a whiff of elitism about it. They’re just missing the big picture. I completely agree that the Dark Matter result is vastly more important new science than the simple fact of Pluto’s demotion, but from the perspective of science education, the value of the Pluto coverage is immensely important, and maybe at least as important as the Dark Matter coverage. I can think of several reasons, and here are some:

Continue reading ‘Spinach Blogging’

So Do We Need a New Planetary Mnemonic?

Published
by
Clifford
on August 24, 2006
in astronomy, fun, planets and science
. 6 Comments

So you’ll recall that when we thought we had twelve planets we started trying to think of new mnemonics to help people remember the planets’ ordering.

For example, from Yvette:

My Very Educated Mother Can’t Justify Someone Using New Planetary Conventions… oh no, they haven’t named the last one yet!!!

Or from Amara’s friend Damien Broderick:

My very eccentric mother’s cook just served us nine pastry coated xylophones

(On the assumption that the last planet would be named Xena.)

Or from astromcnaught:

My View Embraces Moving Classifications, Just Stop Uncovering New Planets Called 2003 UB313

Or from Alan Hamilton (via Robert Greenham):

Most Victorian Euphoniums Make Cats Jump Suddenly Unless Neighbours Play Calming Xylophones.

Continue reading ‘So Do We Need a New Planetary Mnemonic?’

Eight Planets!

Published
by
Clifford
on August 24, 2006
in astronomy, planets and science
. 11 Comments

Ok… Let’s try this again shall we?

It’s official! There are eight planets in our solar system. The vote has taken place. Last week’s proposals have been rejected. Pluto has been demoted, apparently.

They were voting on the following (I got this here):

1) A planet1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A dwarf planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects3 orbiting the Sun shall be referred to collectively as “Small Solar System Bodies”.

1The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
2An IAU process will be established to assign borderline objects into either dwarf planet and other categories.
3These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

That was resolution 5A, and then there is 5B:

Insert the word “classical” before the word “planet” in Resolution 5A, Section (1), and footnote 1. Thus reading:

(1) A classical planet1 is a celestial body . . .

And then the Pluto-specific resolutions (actually, 5B seems to lay the groundwork of the attempt to save Pluto):

RESOLUTION 6A
The IAU further resolves:

Pluto is a dwarf planet by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.

RESOLUTION 6B
The following sentence is added to Resolution 6A:

This category is to be called “plutonian objects.”

Anyway, from what I heard, looks like these attempts to keep it have been rejected - those last few resolutions were voted down - and Pluto has been given the chop.

More later…

[Update: BBC story on it here.]

-cvj

It’s Not Over ‘Til It’s Over

Published
by
Clifford
on August 23, 2006
in astronomy, planets and science
. 2 Comments

The saga continues. Nobody yet knows how many planets we have. There has been fierce argument at the International Astronomical Union. As a result, the definitions of last week have been revised. “Pluton” has been discarded as a term (partly because of the clash with a geological term, a clash which was also swiftly noted by one of Asymptotia’s readers), and the vote is very soon.

IAU meeting photo

Pluto and all the loveable little bodies might now in trouble because a revision to the definition says that a planet must be the “dominant body” in its orbital zone, clearing out any little neighbours. New Scientist’s website reports that

Pluto does not qualify because its orbit crosses that of the vastly larger Neptune.

Quoting further:

Continue reading ‘It’s Not Over ‘Til It’s Over’

MOND Laid to Rest?

Published
by
Clifford
on August 21, 2006
in astronomy, cosmology, dark matter and science
. 12 Comments

Well, the press conference I told you about has happened! This is so exciting! There’s new and very direct proof from observations of the Bullet Cluster with the Chandra X-ray Observatory that Dark Matter really exists.

Bullet Cluster Composite

So the need to make modifications to how gravity works on large scales in order to explain observations seems to be something we can put aside for now.

Your mission: Go to the press release website for more information, and lovely Continue reading ‘MOND Laid to Rest?’

Twelve Planets!

Published
by
Clifford
on August 16, 2006
in astronomy, planets and science
. 33 Comments

It’s official!* There are twelve planets in our Solar System (so update all the posters, such as the ESA one on the right). [Update1.... Oh no it's not official! See here.] [Update2: The vote is in... see here.]

ESA diagram of solar system (outdated)Count ‘em:

  1. Mercury
  2. Venus
  3. Earth
  4. Mars
  5. Ceres
  6. Jupiter
  7. Saturn
  8. Uranus
  9. Neptune
  10. Pluto
  11. Charon
  12. 2003 UB313

In addition, you’ll have to add a new word or two to your vocabulary, such as “pluton”, of which Pluto is the prototype. From the 16th August press release of the International Astronomical Union:

16-August-2006, Prague. The world’s astronomers, under the auspices of the International Astronomical Union (IAU), have concluded two years of work defining the difference between “planets” and the smaller “solar system bodies” such as comets and asteroids. If the definition is approved by the astronomers gathered 14-25 August 2006 at the IAU General Assembly in Prague, our Solar System will include 12 planets, with more to come: eight classical planets that dominate the system, three planets in a new and growing category of “plutons” – Pluto-like objects – and Ceres. Pluto remains a planet and is the prototype for the new category of “plutons.”

-cvj

(Thanks Amara!)

(*almost official. It has to be approved, it says.)

Watch That Space!

Published
by
Clifford
on August 15, 2006
in astronomy, cosmology and science
. 13 Comments

chandra x-ray observatory (NASA image)NASA is about to make an exciting announcement, apparently. On Monday 21st August there will be a press conference, and there will be actual information (they say) at several places mentioned in this link.

I have not the slightest idea of the details of the announcement [but see update below], except that the title of the page is “NASA Announces Dark Matter Discovery”! It concerns observations with NASA’s Chandra X-ray Observatory. The Chandra site says “Astronomers will announce how dark and normal matter have been forced apart in an extraordinarily energetic collision at 1 p.m. EDT Monday, Aug. 21.”, so I infer from this that they might not have completely pinned down the nature of the Dark Matter so much as found a completely new kind of smoking gun pointing to its existence.

On the other hand, Continue reading ‘Watch That Space!’