Mohan:
More on Chandra:
From Chandrasekhar to Chandra
Dr Somak Raychaudhury was a member of the team at Harvard University that
designed and built the High-resolution Camera on board the Chandra Observatory.
He writes on his experience. One of the busiest places in Cambridge,
Massachusetts, these days is the top floor of a building across the street from
Massachusetts Institute of Technology (MIT).
Round the clock, astronomers at the Chandra Operations Control Center are
painstakingly checking the functioning of the computers and instruments on board
the Chandra X-ray Observatory (CXO).
This will continue until the front lid of the telescope is opened on August 13, and
scientific observations begin. The astronomers are pleased: everything looks fine.
Meanwhile, the CXO gave itself the fourth of its five boosts on Saturday. It's now
swinging between 10,000 km and 1,40,000 km from Earth in its orbit that lasts 55
hours. By next Tuesday, it will have settled into its 64-hour orbit, reaching as far as
one-third the distance to the Moon.
It took astronomers almost four centuries to advance from Galileo's first optical
telescope to NASA's Hubble Space Telescope — an increase in observing power
of about half-a-billion. NASA's CXO is about one billion times more powerful than
Uhuru, the first X-ray telescope which was launched only three decades ago. X-ray
astronomy can only be done from space because the Earth's atmosphere blocks
X-rays. Also, X-rays are notoriously difficult to focus, must be caught at grazing
incidence, and then deflected with a long series of mirrors, very slightly each time.
That is why the Observatory is 45 feet long — the largest and heaviest satellite ever
launched. There are four instruments at one end of the 45-foot long satellite — two
cameras and two spectrographs, to record images and spectra of hot remnants of
dead stars and the invisible million-degree hot gas in which galaxies are sloshing
around in rich clusters.
The telescope's resolving power is half an arcsecond, equal to the ability to read
the letters of a no-entry sign at a distance of 20 km. To match this resolution, one
had to build the high-resolution camera, 69 million ultra-thin tubes of lead oxide on
two 10 by 10 cm plates.
The Advanced X-ray Astrophysics Facility (AXAF), which is what it was called
when I worked on the project, was renamed the Chandra X-ray Observatory last
December, in honour of the late Indian-American Nobel Laureate Subrahmanyan
Chandrasekhar.
The naming contest launched by NASA on the Internet attracted over 6,000 entries
from 61 countries. Curiously enough, of the 59 people who submitted the name
“Chandra”, only two were from India. The two winners, who won free tickets to the
launch last week for their essays justifying their choice, were a high school student
from Idaho and a school teacher from California.
The Chandra Observatory will give us the best images ever of such events. Half a
century ago, Chandrasekhar gave us the physics we needed to understand them. |
