News
 Emmanuël Jehin & others / TRAPPIST Observatory
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Bulletin at a GlanceNews
Observing This Week’s Sky at a Glance Community |
Eris Gets
Dwarfed (Is Pluto Bigger?)
November 7, 2010 | On November 6th, it
only took 76 seconds for astronomers to realize that the distant dwarf planet Eris is substantially smaller
than thought — and now might even be a bit smaller than Pluto. > read more
only took 76 seconds for astronomers to realize that the distant dwarf planet Eris is substantially smaller
than thought — and now might even be a bit smaller than Pluto. > read more
December
Digital Edition Available
November 9, 2010 | The digital edition
of the December 2010 S&T is now available. > read more
of the December 2010 S&T is now available. > read more
Why is the
Milky Way Blowing Bubbles?
November 11, 2010 | Using gamma-ray
eyes on NASA’s Fermi spacecraft, astronomers now see that our home galaxy sports
a matched pair of enormous and recently formed bubbles. It’s a mystery how and
why they formed. > read more
eyes on NASA’s Fermi spacecraft, astronomers now see that our home galaxy sports
a matched pair of enormous and recently formed bubbles. It’s a mystery how and
why they formed. > read more
Observing
 Don
Parker |
Jupiter’s
Lost Belt Reviving?
November 10, 2010 | A sudden bright storm has
erupted in the latitude of Jupiter’s South Equatorial Belt. It’s expected to be
the first of a series of rapid changes in the days ahead, leading to a
reappearance of the missing dark belt. > read more
erupted in the latitude of Jupiter’s South Equatorial Belt. It’s expected to be
the first of a series of rapid changes in the days ahead, leading to a
reappearance of the missing dark belt. > read more
How Dark
Are Your Skies?
October 28, 2010 | Take part in this
year’s Great World Wide Star Count, and you’ll be joining thousands of other
“citizen scientists” in raising dark-sky awareness around the globe. > read more
year’s Great World Wide Star Count, and you’ll be joining thousands of other
“citizen scientists” in raising dark-sky awareness around the globe. > read more
Tour
November’s Sky by Eye and Ear!
October 29, 2010 | The
change back to standard time brings earlier nightfall — and a chance to spot
mighty Jupiter dominating the November evening sky. Host: S&T’s Kelly
Beatty. (5MB MP3 download: running time: 5m 33s) > read more
change back to standard time brings earlier nightfall — and a chance to spot
mighty Jupiter dominating the November evening sky. Host: S&T’s Kelly
Beatty. (5MB MP3 download: running time: 5m 33s) > read more
Encounters
with Comet Hartley 2
October 28, 2010 | Comet Hartley 2 comes
back into moonless view around the morning of November 1st — in time for the
spacecraft encounter on November 4th! > read more
back into moonless view around the morning of November 1st — in time for the
spacecraft encounter on November 4th! > read more
This Week’s Sky at a Glance
 Sky & Telescope diagram
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This Week’s Sky at a Glance
November 12, 2010
| Dramatic telescopic events have begun on Jupiter. Mira is still 3rd magnitude but starting to
fade. And Venus, Spica, and Saturn are climbing
higher in the dawn. > read more
| Dramatic telescopic events have begun on Jupiter. Mira is still 3rd magnitude but starting to
fade. And Venus, Spica, and Saturn are climbing
higher in the dawn. > read more
Community
 S&T: J. Kelly Beatty
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Create
Great Images, Win Cool Stuff!
November 9, 2010 | Are you up for a
challenge? Work some computer magic on images obtained with the ESO telescopes,
and you might win an all-expenses-paid trip to the Very Large Telescope in Chile. > read more
challenge? Work some computer magic on images obtained with the ESO telescopes,
and you might win an all-expenses-paid trip to the Very Large Telescope in Chile. > read more
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Ann
Pluto and Eris are both planets and Kuiper Belt Objects. One does not preclude the other. They are planets because they are large enough to be rounded by their own gravity. They are Kuiper Belt Objects because they are located in the Kuiper Belt. Ceres too is a small planet because it is large enough for its gravity to pull it into a spherical shape. The IAU misappropriated the term “dwarf planet,” which was first coined by Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto, to indicate a third class of planets which are large enough to be rounded by their own gravity but not large enough to gravitationally dominate their orbits. He never intended for “dwarf planets” to be classed as not planets at all. The IAU did not “have” to do anything other than allow Eris’s discoverer to name it while holding off on any additional classification until more information is discovered about remote planets in this solar system and all planets in other solar systems.
Significantly, there are quite a few exoplanet systems in which multiple planets orbit the host star in various different planes. Some have orbits far more eccentric than Pluto’s, yet they are giant planets the size of Jupiter or larger. According to the IAU definition, none of these objects are planets!
Saying there are more differences between Pluto and the eight closer planets to the Sun depends on what aspects one considers. Earth actually has far more in common with Pluto than with Jupiter. Both have surfaces on which we can place rovers and landers. Both have a large moon formed by giant impact; both are geologically differentiated into core, mantle, and crust, and both have nitrogen in their atmospheres. Other than orbiting the Sun, what do Earth and Jupiter have in common?
It is premature to pronounce declarations that these faraway objects are definitively not like the other planets or that one is larger than the other. We just do not have enough data at this point to do more than make educated estimates. What we really need to do is send robotic missions like New Horizons to Eris as well as Haumea and Makemake. Yes, that will take time and money, but it is a far better investment than the black holes the endless wars in Iraq and Afghanistan have become.
Also, memorization is not important. It is much more important to teach the characteristics of each category of planet than to ask kids to memorize a bunch of names. We don’t ask them to memorize the names of rivers or mountains on Earth, so why do so with planets, and why allow a need for convenient memorization to determine how we classify them?