Black hole closer to Earth than thought

Astronomers have accurately measured the distance between Earth and a particular black hole for the first time. And wow, is it close.

The researchers determined that the black hole V404 Cygni is located 7,800 light-years from Earth — or just slightly more than half the distance that was previously assumed.

That puts it relatively nearby to Earth, where the distance to the center of the galaxy is about 26,000 light-years, and the nearest star beyond the sun is a mere 4.2 light-years away.
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The more accurate distance measurement will enable scientists to paint a better picture of how black holes evolve, the team says.

“For example, we hope to be able to answer the question as to whether there is a difference between black holes that evolve directly from the collapse of a star without a supernova and black holes that evolve via a supernova and a temporary intermediate star,” said study team member Peter Jonker of SRON Netherlands Institute for Space Research.

“We expect that the black holes in the last group can get a kick. Black holes formed in this way could then move through space faster.”

Jonker and his team measured the distance to V404 Cygni by measuring radio emissions from the black hole and its associated dying star.

The outermost layers of the star are being siphoned by the black hole. The swirling gas forms a hot plasma disk around the black hole before it disappears, and the process emits a lot of X-rays and radio waves.

Using an international system of radio telescopes called the High Sensitivity Array, the team measured the so-called parallax shift of the black hole system. This method involves measuring the annual movement in the sky of the black hole system as a consequence of Earth’s orbit around the sun.

The team says the previous overestimation of V404 Cygni’s distance was due to an underestimation of the absorption and diffraction of interstellar dust, which can give an error margin of about 50 percent. The error margin of the new measurement is less than 6 percent.

New NASA space telescope launched

by CBC news

NASA launched its Wide-field Infrared Survey Explorer (WISE) space telescope Monday morning, a device which will be able to survey the entire sky in six months.

A Delta II rocket carrying the WISE space telescope lifts off from Vandenberg Air Force Base in California. A Delta II rocket carrying the WISE space telescope lifts off from Vandenberg Air Force Base in California. (NASA TV) The WISE telescope launched aboard a Delta II rocket at from Vandenberg Air Force Base in California at 9:09 ET.

The satellite will orbit the Earth over the north and south poles and will detect objects that are difficult to see from the ground, including asteroids, cool stars such as brown dwarfs, and galaxies that shine brightly in infrared light.

“The last time we mapped the whole sky at these particular infrared wavelengths was 26 years ago,” said Edward Wright of UCLA, the principal investigator of the mission.

“Infrared technology has come a long way since then. The old all-sky infrared pictures were like impressionist paintings. Now, we’ll have images that look like actual photographs,” he said in a statement.

Once in orbit, the valves in the telescope’s cooling system will automatically open, venting super-cooled hydrogen into space.

An artist’s concept of NASA’s WISE space telescope. An artist’s concept of NASA’s WISE space telescope. (NASA/JPL) “By venting the hydrogen to space, we cool our instrument down to extremely low temperatures so that the eyes of WISE won’t be blinded by their own heat,” said William Irace, the mission’s project manager at NASA’s Jet Propulsion Laboratory.

Because WISE has a limited supply of hydrogen coolant, the satellite’s mission will last only about 10 months, enough time to survey the entire sky about one-and-a-half times.