|
01/30/2008
Black Stuff
With my wife in rehab and other medically related matters, I
must admit to being in a rather dark mood these days. So, why
not write about dark, or if you will, black things that have been in
the news recently. Some time ago, I saw an article somewhere
and may even have written about the development of a nickel-
phosphorus alloy that was claimed to be the world’s blackest
material. What is blackness? Essentially it is a measure of how
much light is reflected back to your eyeballs by a material. The
National Institute of Standards and Technology (NIST) maintains
a standard of blackness and the nickel-phosphorus alloy reflected
about 10 times less light than that standard. A more familiar
item would be ordinary black paint, which reflects 5 to 10
percent of light striking it.
Now, in a January issue of the journal Nano Letters, a team led
by Shawn-Yu Lin of Renssellaer Polytechnic Institute (RPI)
reports an even blacker material. I’ve drawn on brief news items
in the January 18 issue of Science, the January 21 issue of
Chemical and Engineering News and a visit to the RPI Web site
for the information that follows. While an etched surface of the
nickel-phosphorus alloy reportedly reflects a mere 0.16 – 0.18
percent of the light you shine on it, the new material reflects
some three times less than that – a paltry 0.045 percent. Put
another way, 99.955 percent of the light gets trapped.
The super black material is a thin film of loosely aligned carbon
nanotubes standing up like trees in a forest. The height of the
carbon “trees” ranges up to one millimeter and the diameters of
the nanotubes are about 10 nanometers (billionths of a meter).
By engineering how the loosely packed nanotubes intertwine
with each other, thus creating nanovoids and gaps, light is
trapped and scattered within the “forest”. What good is this
blackest of materials? It may not set the world on fire but there
may be stealth military applications if the material shows the
same darkness with respect to infrared and ultraviolet radiation
as it does with visible light. Researchers also envision that the
material might have use in increasing the amount of light
absorbed in solar energy applications.
On a vastly different scale, another black object made news in
the astronomical community recently. Coincidentally, the object
is an OJ, but not the OJ flaunting the legal system recently. This
object is OJ287, a black hole some 3.5 billion light-years from
Earth. This OJ287 is not your ordinary run-of-the-mill black
hole. No, it’s the mother of all black holes found to date,
weighing in at a phenomenal 18 billion times the mass of our
sun! That’s six times bigger than the largest previously known
black hole. According to a report by Govert Schilling in the
January 18 issue of Science, twenty years ago astronomers were
looking through photographs of the galaxy in which OJ287
makes its home. These photos dated all the way back to 1891
and the researchers found that every 12 years the radiation from
this galaxy flared up about 100 thousand times the normal
intensity. These monumental periodic flares took place in two
bursts a year apart.
When an astronomer hears about something that happens on a
periodic schedule, the gut reaction is that there some sort of
orbiting going on. Astronomer Mauri Valtonen of the University
of Turku in Finland proposed that, while OJ287 was busy
gobbling up gas and anything else that came its way, there was
another black hole orbiting OJ. He further proposed that the
orbit was very elongated and that the black hole’s orbit was tilted
quite strongly with respect to the main disc of gas, stars and what
have you surrounding OJ287. This means that the orbiter
spends most of its time outside the main disc, crossing the disc
every 12 years and then coming back and crossing it again a year
later on its way back out in the longest part of its orbit.
Each time the orbiting black hole crosses the main disc, it whips
up the surrounding matter in the disc to high temperatures
resulting in the intense radiation in the flares a year apart. There
had been flare-ups in 1994 and 1995 and in November of 2005.
Voltonen and his team predicted another flare would occur on
September 13, 2007. Some 30 professional and amateur
observatories were tuned in to OJ287’s galaxy and, at a meeting
of the American Astronomical Society this month, Voltonen
announced that the flare had indeed occurred at the predicted
time. From the orbital motion, the astronomers calculated that
the mass of the orbiting black hole was only a mere 100 million
suns, puny compared to the 18 billion sun mass calculated for
OJ287.
Just think, astronomers can follow this for about 10 thousand
more years, at which time the two black holes will merge. That
should result in quite a show. Actually, I presume that the
merger took place long ago since OJ287 is 3.5 billion light-years
away and the light from the merger has already been traveling
our way for billions of years! The telescope is a great time
machine.
The precise prediction of the date of the most recent flare not
only confirmed Voltonen’s model but also was a spectacular
confirmation of Einstein’s theory of general relativity. With
these humongous black holes, Einstein predicted that spacetime
would be greatly distorted. If spacetime were not distorted, the
second flare would have occurred 10 days earlier than predicted.
The interaction should also generate gravitational waves,
according to Einstein. If there were no gravitational waves the
flare would have happened 20 days later than predicted. Once
again, Einstein comes through with flying colors.
Well, there you have it. The “blackest” black hole and the
blackest material here on Earth. I’m sure we can expect many
more spectacular developments in both the vast expanses of the
universe and in the teensy nano-world.
Allen F. Bortrum
|
