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Space Museum delves into the mystery of black holes

“Exploring The Black Holes”, the latest Sky Show production by the Hong Kong Space Museum, will be screened from tomorrow (December 12) until May 31 next year. Through the show, audiences will follow the footsteps of astronomers to explore black holes - the most mysterious objects in the universe.

Black holes are regions of space that have such a strong gravitational pull that they can engulf everything around them. Normal stellar black holes are believed to have been formed from the collapse of massive stars that could no longer resist the pressure of their own gravity. A normal star can remain stable for a long time by maintaining the equilibrium of its gas pressure and radiation pressure. However, when this equilibrium is lost, the star’s core will collapse and become an ultra-dense object such as a white dwarf star, neutron star or a non-luminous and non-reflective celestial body, which is called a black hole. The gravitational force of a black hole is so powerful that even light, the fastest thing in the universe, cannot escape from it.

After a black hole forms, all matter inside it is compressed into a massively dense point called the “singularity”, the centre of a black hole. The boundary of a black hole from which not even light can escape is called the “event horizon”. Immediately outside the event horizon is a spherical region called the “photon sphere”. Whenever light passes the sphere tangentially, the gravitational force of the black hole will capture it, and it will revolve around the black hole endlessly like a satellite orbiting a star. The black hole may seem terrifying, but its gravitational force outside the event horizon is the same as that of a star with similar mass. More than 50 suspected black holes have been identified so far. Cygnus X-1 was considered the earliest celestial body to be defined as a black hole.

The show also introduces two kinds of black holes: the supermassive black hole and the intermediate-mass black hole. The supermassive black hole, whose mass is billions of times that of a solar mass, swallows matter and creates an “accretion disk”. Jets of electrons and other sub-atomic particles are emitted from the poles of the supermassive black hole. Although astronomers do not have enough concrete information about the formation of the intermediate-mass black hole, they have inferred from the data collected by Hubble’s Space Telescope in 2002 that the centre of M15, a globular star cluster, may be an immediate-mass black hole with a mass 4,000 times that of solar masses.

The black hole is always depicted as having enormous power and the ability to pull and suck in anything nearby, and it seems nothing can escape from it. However, the show also presents another perspective introduced by Stephen Hawking, the famous British physicist, who suggested that black holes release particles and emit radiation, and hence lose mass. The smaller the black hole, the more particles will be emitted, causing it to shrink faster. The process is called “Hawking radiation”. The radiation from a massive black hole is very weak, and has little impact on it. But “Hawking radiation” can consume the mass of a small black hole, making it disappear.

The 40-minute Sky Show "Exploring The Black Holes" will be screened daily at 2.40pm and 6.10pm at the museum’s Stanley Ho Space Theatre. There will be an additional screening at 11.10am on Sundays and public holidays. The museum closes at 5pm on Christmas Eve and Lunar New Year’s Eve, and on Tuesdays (except public holidays) and the first two days of the Chinese New Year.

Tickets priced at $24 (front stalls) and $32 (stalls) are now available at the Space Museum box office and at all URBTIX outlets. Full-time students, senior citizens aged 60 or above and people with disabilities can enjoy a half-price concession.

The Space Museum is located at 10 Salisbury Road, Tsim Sha Tsui, Kowloon. For further information, please call 2721 0226 or visit the website at .

Ends/Tuesday, December 11, 2007

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