A Newly Discovered Galaxy Has a Shocking Feature—No Dark Matter

Gemini Observatory/NSF/AURA/Keck/Jen Miller
Gemini Observatory/NSF/AURA/Keck/Jen Miller

Astronomers have discovered a galaxy that upends what we thought about galaxies. A new study in Nature reports that this one has almost no dark matter—unlike just about every other galaxy ever observed.

Called NGC1052-DF2, the new galaxy is an ultra-diffuse galaxy, a type that is large but still appears faint and contains few stars. Ultra-diffuse galaxies in themselves aren't very rare, but scientists have never observed one without a significant amount of dark matter, a component thought to be a vital part of the galaxy-formation process.

"For decades, we thought that galaxies start their lives as blobs of dark matter," said Yale University astronomer Pieter van Dokkum, lead author of the study, in a press release. "NGC1052-DF2 challenges the standard ideas of how we think galaxies form."

An image of a faint galaxy next to another image of a globular cluster in that galaxy
Gemini Observatory/NSF/AURA/Keck/Jen Miller/Joy Pollard

The research team first observed the galaxy, located 6.5 billion light-years from the Milky Way, using the Dragonfly Telephoto Array in New Mexico, a telescope designed specifically for finding ultra-diffuse galaxies. They also gathered data from the Gemini North Observatory and W.M. Keck Observatory in Hawaii and several other telescopes around the world.

They discovered the lack of dark matter in the galaxy from spectral data that showed that objects in the system were moving slower than expected, meaning the system didn't have a lot of mass. By their calculations, the mass of the galaxy can be almost entirely attributed to the stars, meaning there is little dark matter there—a contrast to just about any other galaxy observed. (Meanwhile, in 2016, van Dokkum and his team found an ultra-diffuse galaxy that is made up of 99.9 percent dark matter.)

"There is no theory that predicted these types of galaxies," van Dokkum said. “The galaxy is a complete mystery, as everything about it is strange. How you actually go about forming one of these things is completely unknown."

The discovery provides more evidence for the dark matter hypothesis, and means that it isn't just a part of galaxy formation. It exists on its own, separate from its role as a galaxy component. The research team has already found a few other diffuse galaxies that appear to resemble this new galaxy, and plans to continue searching for and analyzing these dark-matter-free systems.

A Super Pink Moon—the Biggest Supermoon of 2020—Is Coming In April

April's super pink moon will be extra big and bright (but still white).
April's super pink moon will be extra big and bright (but still white).
jakkapan21/iStock via Getty Images

The sky has already given us several spectacular reasons to look up this year. In addition to a few beautiful full moons, we’ve also gotten opportunities to see the moon share a “kiss” with Venus and even make Mars briefly disappear.

In early April, avid sky-gazers are in for another treat—a super pink moon, the biggest supermoon of 2020. This full moon is considered a supermoon because it coincides with the moon’s perigee, or the point in the moon’s monthly orbit when it’s closest to Earth. According to EarthSky, the lunar perigee occurs on April 7 at 2:08 p.m. EST, and the peak of the full moon follows just hours later, at 10:35 p.m. EST.

How a supermoon is different.

Since the super pink moon will be closer to Earth than any other full moon this year, it will be 2020’s biggest and brightest. It’s also the second of three consecutive supermoons, sandwiched between March’s worm moon and May’s flower moon. Because supermoons only appear about 7 percent bigger and 15 percent brighter than regular full moons, you might not notice a huge difference—but even the most ordinary full moon is pretty breathtaking, so the super pink moon is worth an upward glance when night falls on April 7.

The meaning of pink moon.

Despite its name, the super pink moon will still shine with a normal golden-white glow. As The Old Farmer’s Almanac explains, April’s full moon derives its misleading moniker from an eastern North American wildflower called Phlox subulata, or moss pink, that usually blooms in early April. It’s also called the paschal moon, since its timing helps the Catholic Church set the date for Easter (the word paschal means “of or relating to Easter”).

[h/t EarthSky]

Are Any of the Scientific Instruments Left on the Moon By the Apollo Astronauts Still Functional?

Apollo 11 astronaut Neil Armstrong left the first footprint on the Moon on July 20, 1969.
Apollo 11 astronaut Neil Armstrong left the first footprint on the Moon on July 20, 1969.
Heritage Space/Heritage Images/Getty Images

C Stuart Hardwick:

The retroreflectors left as part of the Apollo Lunar Ranging Experiment are still fully functional, though their reflective efficiency has diminished over the years.

This deterioration is actually now delivering valuable data. The deterioration has multiple causes including micrometeorite impacts and dust deposition on the reflector surface, and chemical degradation of the mirror surface on the underside—among other things.

As technology has advanced, ground station sensitivity has been repeatedly upgraded faster than the reflectors have deteriorated. As a result, measurements have gotten better, not worse, and measurements of the degradation itself have, among other things, lent support to the idea that static electric charge gives the moon an ephemeral periodic near-surface pseudo-atmosphere of electrically levitating dust.

No other Apollo experiments on the moon remain functional. All the missions except the first included experiment packages powered by radiothermoelectric generators (RTGs), which operated until they were ordered to shut down on September 30, 1977. This was done to save money, but also because by then the RTGs could no longer power the transmitters or any instruments, and the control room used to maintain contact was needed for other purposes.

Because of fears that some problem might force Apollo 11 to abort back to orbit soon after landing, Apollo 11 deployed a simplified experiment package including a solar-powered seismometer which failed after 21 days.

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