Discover - USA (2020-01 & 2020-02)

JANUARY/FEBRUARY 2020. DISCOVER 11

says. “And at the end we synthesize it into a single image.” But

that’s still not the end of the work, she says. “[You] spend another

six months worrying about all the things you might have done

wrong, and ask yourself more and more questions, until finally

you can be certain that what you have is real.”

TARGETING OUR GALAXY’S BLACK HOLE

And that real image is just the first that astronomers expect the

EHT will produce. The global array’s other main target is the

black hole at the center of the Milky Way, Sagittarius A* (pro-

nounced A-star). While it sits 1,000 times closer than M87, it’s

also roughly 1,000 times smaller, so it takes the same amount of

observing power. But because it’s smaller, the material swirling

around its event horizon moves much faster, completing one

circuit every few minutes; for M87, it’s once every few days. “It

makes Sagittarius A* harder,” Özel says.

What’s more, astronomers aiming at Sagittarius A* must look

through the disk of the galaxy, which means dealing with more

dust and other interfering material. But they still expect to release

images of our galaxy’s black hole in the near future.

Even more exciting are the repeat images of M87 and other black

holes yet to come. By watching how the black hole does or doesn’t

change with time, astronomers can learn about its stable features

and watch how material disappears past the event horizon.

SPT

South Pole

Telescope

South Pole Station,

Antarctica

PV

IRAM 30-Meter

Telescope

on Pico Veleta, Spain

GLT

Greenland Telescope

at Thule Air Base,

Greenland

GLT

SMT

LMT

APEX

ALMA

SPT

PV