Where to "Put" All the New Planets?

Artist concept of 100th planet. NASA

Planets, outside our solar system, are being discovered by the dozen. So many announcements are being made, that there is no globally recognized count of extra-solar planets. Nor has the pace of discovery allowed time for peer-reviewed publication and follow-up study of all announced planets: duplicates, retractions, and whether to count only published results cloud the count. The web-based Extrasolar Planets Encyclopaedia recently posted the 100th planetary discovery - based on public announcement - but doesn't include free-floaters not bound to a star. One researcher believes the count will grow to several hundred, when several space-based planet-hunting telescopes are launched in the next few years. The need for a planetary discovery clearing-house is evident.

The International Astronomical Union (IAU) expects to take-up that role. It already acts as the "book-keeper" for all things astronomical: from constellation boundaries to naming of planetary features. Its Working Group on Extrasolar Planets is developing a system, to be presented by October, to determine how to assign credit for discoveries, how to verify and count these objects, and perhaps naming these planets.

More information:

MSNBC/Space.com; July 2, 2002; Space News: "Astronomers hurry to log new planets"

Earth Times 30 x 10⁹

With the announcement of the 100th extra-solar planet, scientists have just about looked at all the stars within 100 light-years of the Earth. This large sample gives them enough confidence to offer ballpark estimates of the number of planets in our galaxy. Of the roughly 1000 stars within 100 light-years of Earth, 10% have planets. If this is representative of the 300-billion stars in the Milky Way, there are 30-billion planets in our galaxy.

Due to limitations in detection ability, only gas-giants have been detected so far - no smaller than our planet Saturn. Future Earth and space-based observations will undoubtedly detect smaller worlds, and increase the number of known planets in our 100 light-year neighborhood. Instruments to detect Earth-like planets may be put into orbit in the mid to later years of this decade. If galactic solar systems are anything like ours, they'll have a distribution of planets - from gas-giant to rocky Earth-like. With that assumption, it is reasonable to say there are 30-billion Earths out there to be discovered.

More information:

BBC.com; July 1, 2002; Sci/Tech: "Scientists estimate 30 billion Earths"

Black Holes Hiding in Their Shells

A new hypothesis as to the make-up of stellar black-holes has emerged from researchers at the U.S. Department of Energy's Los Alamos National Laboratory and the University of South Carolina: black holes, according to these theorists, are actually Gravitational Vacuum Stars (Gravastars) -- bubbles of super-dense matter.

The new theory is based on studies of Bose-Einstein condensate -- a phase of matter recently observed in the laboratory. Produced by freezing matter to near absolute zero, Bose-Einstein condensate is created when subatomic particles cease to move and coalesce into a single "super atom."

In the new black-hole hypothesis, some massive stars run out of fuel and begin gravitational collapse. When the star reaches the size of the "Event Horizon", the intense gravity transforms matter into the Bose-Einstein condensate. This material forms an ultra cold, dark, and thin shell of indestructible, yet somewhat flexible, material. The interior of the shell is a void where space-time is warped. This has the effect of producing an outward force on the Bose-Einstein shell, reinforcing it. Anything entering the Event Horizon is smashed against the shell of the Gravistar and becomes part of the shell. This contrasts with accepted black-hole theory that has the star collapse to a point and the Event Horizon - the point at which light cannot escape from the orbit of the hole -- is some distance from this point.

The new theory resolves problems involving the entropy of black-holes, and the theorists even suggest that our present Universe may be the interior of a Gravastar!

More information:

Los Alamos National Laboratory; April 21, 2002; Press Release: "Los Alamos researcher says 'black holes' aren't holes at all"

Never Too Old …

Circles mark older (red) and young (blue) clusters in NGC 4365.  ESO

A key question in understanding the development of the Universe is galaxy evolution. And key to galaxy evolution is the question of when and how stars formed within them. Was there a rapid rise of star formation or is it gradual? One important class of galaxies that astronomer's study is elliptical galaxies: they have traditionally been thought to undergo one period of star formation and that was early in the history of the Universe. Recently, the Hubble Space Telescope, the Keck telescope in Hawaii, and the Very Large Telescope in Chile studied NGC 4365 --an elliptical galaxy in the Virgo Cluster.

While most of the stars were found to be a uniform 12-billion years old (no surprise), stellar clusters of stars (globular clusters) a few billion years old were discovered. The distinct periods of star formation in NGC 4365 are as follows: old clusters of metal-poor stars, old clusters of metal-rich stars, and clusters of young metal-rich stars. Textbook writers must now revise their text to say that ellipticals do not have only one period of star formation at the beginning of the Universe.

More information:

European Southern Observatory; June 26, 2002; Press Release: "Young Stars in Old Galaxies - a Cosmic Hide and Seek Game"