Two white dwarfs, remnants of stars that have used up all their fuel, are orbiting each other in a death grip and will eventually merge, says a scientist using the Chandra X-ray Observatory.

According to US space agency NASA, data indicate that gravitational waves are carrying energy away from the star system at a prodigious rate, "making it a prime candidate for future missions designed to directly detect these ripples in space-time".

The system observed by Tod Strohmayer of NASA's Goddard Space Flight Centre, Greenbelt, Maryland, is known as RX J0806.3+1527 or J0806.

According to a paper presented by him at the American Astronomical Society meeting in Minneapolis, the white dwarf pair in J0806 might have the smallest orbit of any known binary system. The stars are only about 50,000 miles (80,000 km) apart, which is one-fifth the distance between the Earth and the Moon.

"If confirmed, J0806 could be one of the brightest sources of gravitational waves in our galaxy," Strohmayer was quoted as saying in a formal announcement.

"It could be among the first to be directly detected with an upcoming space mission called LISA, the Laser Interferometer Space Antenna," he added.

White dwarfs along with neutron stars and black holes are extremely dense and pack a huge amount of mass in a small volume. Each of the white dwarfs in question, for instance, has an estimated mass of one-half the sun, yet are only about the size of the Earth.

The Chandra X-ray Observatory is named after Subrahmanyan Chandrasekhar, a Nobel Prize winning physicist of Indian origin who in 1930 first came up with a mathematical formula describing what turned out to be black holes. Chandra, as he was popular known, was also known for his work on white dwarfs.

--Indo-Asian News Service