The Black Hole Sagittarius A*

Posted on by onespaceman2000
Image (Credit): The first image of Sagittarius A*, the supermassive black hole at the center of our galaxy. (EHT Collaboration)

The Event Horizon Telescope (EHT), an array linking together eight existing radio observatories across the planet, has created the first image of the supermassive black hole at the center of the Milky Way galaxy. Named Sagittarius A* after a radio signal coming from a location in the direction of the constellation of Sagittarius (the A and * came later), the black hole is 27,000 light-years away and estimated to be four million times more massive than our Sun. The presence of the black hole was not in question, but capturing an image such as this took many years of work.

A press release from the European Southern Observatory (ESO) quoted EHT Project Scientist Geoffrey Bower from the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei:

We were stunned by how well the size of the ring agreed with predictions from Einstein’s Theory of General Relativity…These unprecedented observations have greatly improved our understanding of what happens at the very centre of our galaxy, and offer new insights on how these giant black holes interact with their surroundings.

For more on the recent breakthrough, you may want to view the ESO Press Conference on the new Milky Way results from the EHT team (here on Youtube), which is followed by a public question and answer event.

Another Exoplanet Discovered Nearby

Posted on by onespaceman2000
Source/Credit: Artist rendering of a candidate exoplanet orbiting Proxima Centauri from the ESO.

Earlier this month, astronomers utilizing the European Space Observatory’s (ESO) Very Large Telescope identified what appears to be a third exoplanet orbiting Proxima Centauri, the closest star to our solar system at about 4.2 light years away. The ESO press release shared the following details:

The newly discovered planet, named Proxima d, orbits Proxima Centauri at a distance of about four million kilometres, less than a tenth of Mercury’s distance from the Sun. It orbits between the star and the habitable zone — the area around a star where liquid water can exist at the surface of a planet — and takes just five days to complete one orbit around Proxima Centauri.

The star is already known to host two other planets: Proxima b, a planet with a mass comparable to that of Earth that orbits the star every 11 days and is within the habitable zone, and candidate Proxima c, which is on a longer five-year orbit around the star.

…At just a quarter of the mass of Earth, Proxima d is the lightest exoplanet ever measured using the radial velocity technique, surpassing a planet recently discovered in the L 98-59 planetary system. The technique works by picking up tiny wobbles in the motion of a star created by an orbiting planet’s gravitational pull. The effect of Proxima d’s gravity is so small that it only causes Proxima Centauri to move back and forth at around 40 centimetres per second (1.44 kilometres per hour).

It’s great to learn a little more about our nearest neighbor.