Dwarfs and Other Cool Stuff
Many of us spent some time looking skyward last week,
observing rocketing objects bursting into various forms of
pyrotechnic displays. On the night of the 4th of July, we could
hear the booming of the fireworks going off in surrounding
communities. However, our more conservative recreational
gurus postponed our town''s fireworks extravaganza. Unlike
those in the other towns, they paid attention to the weather radar
indicating incipient thunderstorms. Many people were quite
disappointed and kids were even crying when they arrived at the
fireworks locale to learn of the cancellation. A thunderstorm did
materialize, but an hour after the scheduled display.
I empathized with those who have to endure the criticism for
canceling, especially when the surrounding towns'' events went
off without incident. Many years ago, as a Cubmaster, I
cancelled the annual picnic and award ceremony in the face of a
severe storm warning. The evening was clear and dry! The
storm somehow hopped over our town and then dropped down,
doing considerable damage in an adjoining town. But the fury of
angry den mothers was directed at yours truly and I spent the
evening making demand appearances at several homes to present
the resident Cubbies with their awards.
Astronomers have been looking skyward as well and they''re
finding all kinds of things out there. By now, it''s old hat to find
planets orbiting stars outside our solar system. We''ve mentioned
before that they accomplish this by measuring the wobble in a
star''s motion caused by the gravitational force of the planet as it
orbits around the star. So far, none of the planets come close to
resembling our own. Generally, they''ve been huge bodies, more
like Jupiter. Of course, it would be hard to detect the tiny
wobble resulting from a puny planet like our own.
In addition to planets, there''s another kind of cool object out
there beyond our solar system. This object is the ''brown dwarf''.
The brown dwarf is a star that never quite gets its act together.
Although much bigger than your typical planet, it isn''t big
enough. A real star has enough mass that its gravity leads it to be
compressed and heated up so hot that nuclear fusion occurs, as in
our sun. A brown dwarf just heats up due to its gravity and never
gets very bright. Then it slowly cools down over billions of
years until it''s a very dim object with most of its light in the
infrared part of the spectrum. This makes these ''brown'' dwarfs
actually red dwarfs but it turns out that the name ''red dwarf'' was
already taken for another celestial object.
Because of their dimness, brown dwarfs have been hard to find.
Although their existence was postulated way back in the 1960s,
attempts to detect and positively identify any failed until the past
decade. Having worked on lithium batteries for much of my
career, I was intrigued to find that lithium played a key role in
positively identifying one of these brownies. Why lithium? In a
star, the temperature is so high that any lithium would be
gobbled up in a fusion reaction. So, if an object is a star, there
should be no lithium. Some early reports of brown dwarfs were
rejected when no lithium was found. These were really stars. A
group of workers using the Keck telescope on Mauna Kea in
Hawaii found some dim objects in a young star cluster only 120
million years old. The evidence was that dim objects were not
massive enough to be stars. Finally, the clincher was that one of
the object''s spectrum showed that lithium was present. The
existence of brown dwarfs was finally nailed down.
Of course, the scientific community is always hard to satisfy and
there was still skepticism. But another group at about the same
time was going at it differently and found a case where a very
dim star was being orbited by a companion a thousand times
dimmer. They used a clever method of blocking the light of the
brighter star to be able to see the light from its superdim fellow
traveler. The clincher came when they looked at the spectrum of
the orbiting dim one. There was methane present. Now, no way
could methane form on a star. It''s just too darn hot!
Since these findings, both announced in 1995, the floodgates
were opened and now it is thought that the number of brown
dwarfs might actually equal the number of stars. In which case,
our Milky Way galaxy could have a hundred billion or so of
them. For some time, it was thought that brown dwarfs might be
the strange dark matter that makes up over 90 percent of the
universe. However, because of their low masses, brown dwarfs
don''t contribute significantly to dark matter. We still don''t know
what it is!
What really spurred this column, however, was the detection this
year of an object in our own solar system. As with the brownies,
the past decade has seen remarkable progress in finding out
what''s happening in the outer regions of our own solar system.
Conventional wisdom had been that not much of interest was
going on out beyond the most distant planet, Pluto. Pluto is an
odd duck. Except for Pluto, our other planets orbit the sun in
pretty much the same plane, like in those simple diagrams in
your textbooks. Pluto''s orbit is tilted quite a bit. Not only that,
but it also is strange in that Pluto actually sometimes crosses the
orbit of its well-behaved neighbor, Neptune. You might think
that''s not good - they might bump into each other. Fortunately
for both, they do a kind of dance. Pluto orbits the sun twice for
every three times Neptune goes around. That way they don''t get
in each other''s way.
In an ironic twist, the search for a possible planet out beyond
Pluto has not only failed, but also has reduced the number of
planets from 9 to 8! At least that is the opinion of some. I
understand that, if you go to the Hayden Planetarium in New
York, Pluto has been demoted from a planet to just one of the
known hundreds of so-called Kuiper Belt Objects (KBOs).
Some 50 years ago, this guy Gerard Kuiper decided that there
wasn''t any reason that there shouldn''t be more stuff out there
beyond Pluto. Hence the "Kuiper" Belt. Actually, according to
an article by Jane Luu and David Jewitt in the May 1996
Scientific American credits a "an Irish gentleman-scientist"
Kenneth Edgeworth with the idea a couple of years before
Kuiper. Jewitt was the first, or among the first, to actually detect
a KBO in 1992. As with the brown dwarfs, it took quite a long
time from conception to proof of the existence of KBOs. The
origin of the Kuiper Belt is essentially that in the inner solar
system the major planets have swept up and incorporated
virtually all of the ''dust'' available. Out in the far reaches of the
solar system, there wasn''t as much dust to go around and smaller
chunks of stuff were formed.
Since the discovery of the first confirmed KBO in 1992,
hundreds of these objects have been found. Indeed, it seems that
the actual number of KBOs is in the many tens of thousands.
But, according to an article by David Whitehouse dated July 3,
2001 from BBC online that Brian Trumbore called to my
attention, there''s big breaking news. What has astronomers all in
a tizzy these days is the recent discovery of a new KBO,
colorfully named 2001 KX76. Let''s just call it KX for short.
When a survey known as the Deep Ecliptic Survey showed the
first indication of KX, a suitably technical description was called
for. According to Lawrence Wasserman of the Lowell
Observatory in Arizona, when the image came up they wrote
"wow" on it. Science needs more such precise terms to inform
the public about important findings.
Why the ''wow''? KX is the brightest KBO to date. While the
size isn''t pinned down precisely yet, it may be as much as 788
miles across. That size would make it bigger than any asteroid
and larger than Charon, the moon of Pluto. KX is about 4 billion
miles away from the sun. What has the Kuiper Belt guys and
gals hyped up is that they now expect to find other objects just as
large or larger, possibly the size of Pluto itself. The bottom line
is that we still have a long way to go before we can say we really
know what''s in our solar system, let alone what''s out there
The KX object appears reddish and is probably covered with ice.
Its orbit isn''t pinned down yet but it is known that it''s inclined to
the orbits of the major planets in our solar system. I''ll feel better
when they have that sucker really pinned down. If a KX ever hit
the earth that would unquestionably be the end of all of us! Do
you think Brian Trumbore''s gloomy columns have affected my
outlook on things?
Allen F. Bortrum