After a 16 year wait, the star SO-2 will speed past our galaxy’s supermassive black hole at 2.5% the speed of light. It will be the first-of-its-kind test of Einstein’s theory.
This year, for the first time, astronomers will observationally measure a gravitational redshift around a supermassive black hole.
When an object gets close to a massive source, its light must “climb out” of the deformed spacetime predicted by Einstein.
The gravitational potential well can cause the light to lose enough energy that it becomes observably redshifted.
The largest, closest single mass to Earth is Sagittarius A*, our Milky Way’s supermassive black hole, weighing in at 4,000,000 solar masses.
The star S0–2 makes the closest known approach to this black hole, reaching a minimum distance of just 18 billion kilometers.
That’s only three times the Sun-Pluto distance, or a meager 17 light-hours.
Later in 2018, S0–2 will reach a maximum speed of 2.5% the speed of light as it zips past Sagittarius A*.
This event will test Einstein’s predictions for gravitational redshift as never before.
Einstein also predicts a slight kick to the orbit as the star makes its closest approach, an effect astronomers hope to measure.
With no evidence for a binary companion, conditions are ideal for this test.
Someday, we hope to learn how stars like S0–2 can form in such an extreme environment.
Mostly Mute Monday tells the scientific story of an astronomical object, event, or phenomenon in images, visuals, and no more than 200 words.Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.