Interstellar

Voyoager 2 satellite interstellar

The second man-made object in history has now broken free of the sun’s influence and embarked on the long, cold journey into interstellar space:

After launching in 1977, NASA’s trailblazing spacecraft Voyager 2 has finally escaped the heliosphere, the Sun’s protective bubble of charged particles. It follows in the path of its sibling, Voyager 1, which crossed into interstellar space in 2012.

The Sun’s solar wind makes up the heliosphere, which surrounds all the planets in our solar system. The boundary where the hot solar winds of the heliosphere end and give way to the cold interstellar medium is known as the heliopause, and it’s also the border of interstellar space. On November 5, 2018, instruments aboard NASA’s Voyager 2 spacecraft sent back data indicating the craft had crossed the heliopause. The craft is now traveling and collecting data in interstellar space more than 11 billion miles (17 billion kilometers) from Earth.

Safe travels!

Speaking of space, this caught my eye:

In a study published March 9 in The Monthly Notices of the Royal Astronomical Society, astronomers announced the discovery that all disk galaxies rotate about once every billion years, no matter their size or mass.

“It’s not Swiss watch precision,” said Gerhardt Meurer, an astronomer from the International Centre for Radio Astronomy Research (ICRAR), in a press release. “But regardless of whether a galaxy is very big or very small, if you could sit on the extreme edge of its disk as it spins, it would take you about a billion years to go all the way round.”

An awful lot of photons

NASA Fermi 5 years gamma

Or, to be precise, 4×10^84 (that’s 4 with 84 zeros): the total amount of photons emitted by stars in the entire universe.

Clemson University scientists, relying on imagery from NASA’s Fermi Gamma-ray Space Telescope, claim for the first time to have measured all of the starlight ever generated throughout the history of the observable universe.

By the numbers: According to the new data, which was published in the journal Science on Friday, the number of photons — particles of visible light — emitted by stars amounts to 4 times 10 to the 84th power.

Confirmed! Monster black hole at center of Milky Way galaxy

The enormous object with a mass of millions of suns at the center of our galaxy, 26,000 light-years away from the Earth, has long been believed to be a supermassive black hole. Now we have proof:

Researchers used the European Southern Observatory’s sensitive GRAVITY instrument on the Very Large Telescope (VLT) to observe infrared radiation flares coming from the accretion disc around Sagittarius A* — the massive object at the center of our galaxy. Scientists think that most galaxies have a supermassive black hole at their center, but they’d never before had the data and observations to prove it.

To measure the effects of gravity near to a black hole, scientists needed to observe an object actually traveling close to it. They found their mark in a small star called S2 whose orbit takes it deep within Sagittarius A*’s gravity well every 16 years. As they watched, they saw three bright flares traveling around the black hole’s event horizon at about 30 percent of the speed of light — around 216 million miles per hour.

It’s exactly what Einstein’s theory of general relativity predicts would occur when a hot spot (like S2) passes close to a black hole weighing as much as 4 million suns, and the observation helps to confirm that it’s really there.

Never before have scientists observed material orbiting so close to a black hole’s event horizon.

Oh, and in case you were worried:

If the Milky was does in fact have a black hole in the center, will the entire Milky Way eventually be drawn in, (like vacuuming a sheet off of a bed), or are certain parts too far away? Is there a big sphere of empty space around a black hole?

No, the popular picture of a black hole as a huge vacuum cleaner sucking in everything around it is inaccurate. Black holes, even the one at the center of our galaxy, are very small. Only if you get very close to a black hole’s event horizon does it start pulling everything in. So no, most of the galaxy will not eventually fall into the hole. Whether black holes have empty space around them or not depends on their environment. There may be objects or gas close enough to fall in, or there may not be. Many black holes have disks of infalling material around their equators. –Dave Kornreich

Sagittarius A NASA

Supermassive black hole Sagittarius A* (Source: NASA)