Penticton Western News letters to the editor. Astronomer Ken Tapping looks over some of the electronics at the Dominion Radio Astrophysical Observatory. Western News file photo

Star Gazing: Colliding stars

Astronomer Ken Tapping with the NRC’s Dominion Radio Astrophysical Observatory, Penticton

About 130 million years ago, two neutron stars collided. Their impact created waves in spacetime ñ gravity waves, which radiated off into space at the speed of light.

Here, 130 million light years from the event, our gravity wave detectors have just picked it up. A light year is the distance light travels in a year, just under 1E13 (1 followed by 13 zeros) kilometres. This event is especially interesting in that it was first detected through gravity wave observations, and then monitored with other telescopes, providing a wealth of data on an unusual event. Moreover, we might have for the first time obtained multiple observations of the formation of a new, small black hole.

The idea of gravity waves was first raised by Albert Einstein in 1916, when he proposed gravity is not a force, as proposed by Newton, but is in fact due to distortions of the fabric of space-time by material objects. The more massive or more compressed a body is, the greater the distortion. Imagine dropping balls of different sizes and weights onto stretched rubber sheet. Just as the impacts make ripples run over the sheet, explosions and other dramatic cosmic events make ripples in spacetime, and bodies moving through it make a bow wave and a wake. However, Einstein thought gravity waves would remain of academic interest only, being too weak to observe. On the other hand, successfully detecting them would be the ultimate vindication of Einsteinís General Theory of Relativity, so the search was on, and it was a long one.

In 2015 the Laser Interferometer Gravitational Wave Observatory (LIGO), built in 2002, which had to that point detected nothing, was upgraded with new, more sensitive detectors. In 2016 it successfully detected the collision of two black holes and then went on to detect gravity waves from two more black hole collisions. Einstein was right. However, in August this year, something really interesting turned up. On Aug. 17 LIGO detected a ‘chirp’ of gravity waves. Two seconds later the Fermi Space Telescope received a short burst of gamma rays. These are the highest-energy electromagnetic waves and an indicator of a really dramatic event. The LIGO and Fermi observations identified the patch of sky the waves came from, so around the world telescopes got to work searching. Eleven hours later, a telescope in Chile found it, in the galaxy NGC 4993, in the constellation of Hydra. Lots of telescopes monitored the object over the following days as the explosion faded. Observers realized that what they had seen was a collision between two neutron stars, and possibly the birth of a new black hole.

Neutron stars are formed in the explosive deaths of large stars. Shock waves compress the cores of the stars so hard that the atoms collapse. Atoms are mostly empty space, with a number of electrons orbiting around a nucleus consisting of a number of protons and neutrons. The shock wave pushes the electrons right into the nucleus, where the electrons and protons combine to form more neutrons. The result is a ball of neutrons, a few kilometres across, with the mass of a star. A teaspoonful of neutron star material would weigh around 100 million tonnes.

A collision between two neutron stars can produce even greater compression. There is a point in the compression where an objectís own gravity overcomes its ability to resist. Theoretically the object will then shrink without limit. The idea that something can achieve zero size and infinite density is questionable, but if the object shrinks enough, it will distort spacetime enough to close itself off behind a one-way, no return frontier called an event horizon. It has become a black hole.

Saturn lies low in the southwest, getting lost in the twilight. Brilliant Venus lies very low in the dawn glow, with Mars, much fainter, above it. The Moon will reach First Quarter on Oct. 28.

Ken Tapping is an astronomer with the NRC’s Dominion Radio Astrophysical Observatory.

Just Posted

Grizzlies receive experienced player in exchange for rookies

Jordan Robertson will play his first game as a Grizzly Friday at the Forum

From darkroom to jewellery studio

Revelstoke Visual Arts Centre welcomes new space for artists

What’s on for Welcome Week

Series of events are designed to welcome newcomers to Revelstoke

Uber official says public needs to push for ridesharing in B.C.

Mike van Hemmen tells Kelowna Chamber of commerce ridesharing would be ‘win-win-win’

‘We want to find ways for people to thrive,’ says life coach

New free talk during Welcome Week will offer strategies to feel at home in Revelstoke

Okanagan ski hills open for the season

Both Big White and Silverstar Resort open for the 2017-18 season Thursday

Panda picks Argonauts for the win

Giant panda at the Toronto Zoo picks Argos to win Grey Cup on Sunday

Black Friday fervour wanes as some consumers, retailers shun practice

Some businesses are choosing to opt out, while some shoppers are turning to buying online

Stay safe on B.C. roads this holiday season

RCMP warn drivers to plan a safe ride home or suffer the consequences this holiday season

Trudeau apologizes to excluded residential school students

PM makes statement to former students in Nfld who were left out of previous compensation, apology

Traci Genereaux: Gone, but not forgotten

COLUMN: Family, friends want justice for Vernon teen

An adopted cat is the best 10 pounds you’ll gain this season

BC SPCA encouraging families to add a forever feline friend during adoption event Nov. 24 to Dec. 3

Uber official says public needs to push for ridesharing in B.C.

Mike van Hemmen tells Kelowna Chamber of commerce ridesharing would be ‘win-win-win’

Most Read