Tag Archives: gravity waves

Another gravity wave detected by LIGO

The LIGO gravitational wave detector has detected its second gravitational wave, thought to come from the merger of two black holes.

The new observation came at 3:38.53 Coordinated Universal Time on 26 December 2015—late on Christmas day at LIGO’s detectors in Livingston, Louisiana, and Hanford, Washington. As in the first event, the detectors sensed an oscillating stretching of space-time, the signal, according to Einstein’s 
general theory of relativity, of massive objects in violent motion. Computer modeling indicated that its source was two black holes spiraling together about 1.4 billion light-years away. (LIGO researchers had seen a weaker signal on 12 October 2015 that may be a third black hole merger.)

Note the last sentence in the quote above. They might have had a third detection, but are uncertain enough to have not claimed it as one.

LISA Pathfinder proves space-based gravity wave detection technology

Engineers have announced that the gravity wave detection technology being tested in orbit by Europe’s LISA Pathfinder works.

To show that the necessary sensitivity is possible, LISA Pathfinder measures the distance between two masses, both of which are inside the spacecraft. “We’ve shrunk the arm of a large gravitational wave antenna to 35 centimeters so we could show it works properly,” Paul McNamara, LISA Pathfinder project scientist, told the press conference.

LISA Pathfinder was launched in December 2015 to a spot 1.5 million kilometers from Earth. When its test masses where first released to float free in February, “the relief was unbelievable,” McNamara says. Science operations began on 1 March and on that first day the team was able to measure distance variations between the masses much smaller than LISA Pathfinder’s mission requirements, Stefano Vitale, the mission’s principle investigator, told reporters. After a month, the variations were even smaller, “very close to [eLISA] requirements,” he says.

They now hope to launch an array of at least three such spacecraft by the mid-2030s.

Lisa Pathfinder lifts off

Lisa Pathfinder, an experimental probe to test the technologies for measuring gravity waves in space, was successfully launched today by Arianespace’s Vega rocket.

At its core is a pair of free-floating, identical 46 mm gold–platinum cubes separated by 38 cm, which will be isolated from all external and internal forces acting on them except one: gravity. “LISA Pathfinder will put these test masses in the best free-fall ever produced in space and monitor their relative positions to unprecedented precision,” says Karsten Danzmann, who also is the Co-Principal Investigator for the LISA Pathfinder Technology Package, the scientific heart of the satellite. “This will lay the foundations for future gravitational-wave observatories in space such as eLISA.”

It is important to point out that this probe will not measure gravity waves. It doesn’t have the sensitivity to do it. Instead it is testing the engineering, as described above, for building a later probe that will have sensitivity. To gain that sensitivity the floating cubes must be much farther apart, and likely will require several independent satellites flying in formation.

For its next science mission the European Space Agency (ESA) has now decided to give first priority to an X-ray space telescope.

For its next science mission the European Space Agency (ESA) has now decided to give first priority to an X-ray space telescope.

They have demoted a space-based gravity wave detector to second place. As is typical for ESA, the pace here is quite slow, as both missions are now scheduled for launch in 2028 and 2034, decades away.