Galactic Centre: Artist's impression showing a supermassive black hole at the centre of a galaxy.
Credit: NASA/JPL-Caltech
PARIS: Studies of the movement of stars provide the best evidence yet that a huge, gravity-sucking hole sits at the heart of our galaxy.
The observations, to be published in the Astrophysical Journal, also offer the best proof that supermassive black holes – among the most enigmatic and powerful forces in the universe – really do exist.
By tracking the orbit of 28 stars inside the Milky Way for more than 16 years, scientists in Germany were able to trace the most detailed portrait ever obtained of these invisible monsters.
Invisible monster
Black holes are believed to be concentrated fields of gravity so powerful that nothing – not even light – can escape their grasp. The only way to perceive them is by observing their impact on neighbouring celestial bodies.
This black hole is known as Sagittarius A* (pronounced "A star").
"The stellar orbits in the Galactic Centre show that the central mass concentration of four million solar masses must be a black hole, beyond any reasonable doubt," said Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics near Munich, Germany.
One "solar mass" is equivalent to our Sun. Researchers were also able to calculate with far greater precision Earth's distance from the centre of the Galaxy: 27,000 light years.
A light year is the distance light travels in a year, which is about 10 trillion kilometres.
"The centre of the Galaxy is a unique laboratory where we can study the fundamental processes of strong gravity, stellar dynamics and star formation," Genzel said.
Sagittarius A*
Sagittarius A* give us the most detailed view we will ever have of a supermassive black hole because of its proximity to Earth, he said.
The interstellar dust that fills the Galaxy blocks our direct view of the Milky Way's central region in visible light, so astronomers used infrared wavelengths to penetrate the dust.
The position of the stars was measured with a precision six times greater than in previous studies, equivalent to seeing a coin from a distance of roughly 10,000 km.
Observations were made using the SHARP camera at the European Southern Observatory's New Technology Telescope in Chile, and instruments aboard ESO's Very Large Telescope.
Gravity caused by the black hole
How do they distinguish between the gravity caused by the black hole at the center of the Milky Way galaxy on the stars they studied for 16 years and the dark matter that is in the galaxy, and outside the galaxy if that does contribute? Can they determine the location, density and mass of dark matter spread through the galaxy and universe so they can determine its gravatational contribution to the 16 stars? Is the study published online somewhere?
Steve Smarsh
s.smarsh@hotmail.com
S2 Orbital Period
Good comment about the Dark Matter influence on the orbit.
I suspect it is small for a remarkable reason: From the data in the paper, one can calculate the size of the orbit using the 400 yr old Kepler's 3rd law. I ground out a number off by about 10%.
Johannes Kepler would have blown his mind to know that not only did his beautifully simple law explain the motion of the planets 60 yrs prior to Newton, but that we can still use it today, to calculate the orbits of stars, thousands of light years away, bound by black holes millions of times as massive as the sun.
Kepler Rules !
proper semantics
"so astronomers used infrared wavelengths to penetrate the dust."
Don't want to bash informative articles, but we can surely use proper semantics such as: 'so astronomers performed observations in the infrared wavelengths which penetrate the dust.'
Cheers.