Tag Archives: universe

Scientists puzzled by exotic distant galaxy lacking dark matter

The galaxy named NGC 1052-DF2, a large fuzzy-looking galaxy so diffused that astronomers call it a 'see-through' galaxy because its missing most, if not all of its dark matter, is shown in this photo obtained from NASA on March 28, 2018. NASA, ESA, and P. van Dokkum (Yale University)/Handout via REUTERS

By Will Dunham

WASHINGTON (Reuters) – Astronomers have detected for the first time a galaxy that is devoid of dark matter, the plentiful but enigmatic material that does not emit light or energy and had been considered a fundamental part of all galaxies including our own Milky Way.

The discovery, announced on Wednesday, is forcing scientists to rethink their ideas about the formation of galaxies.

“We didn’t expect that this could happen,” said Yale University astronomer Pieter van Dokkum, lead author of the research published in the journal Nature.

Paradoxically, the discovery of a galaxy without dark matter may actually confirm that the stuff actually exists by contradicting hypotheses advanced by dark matter doubters.

Van Dokkum said the galaxy, called NGC1052-DF2 and located about 65 million light years away from Earth, also appears to be devoid of gas and is relatively sparsely populated by stars.

It is about the same size as the Milky Way, but has roughly 250 times fewer stars: 400 million compared to the Milky Way’s 100 billion stars. It is classified as an ultra-diffuse galaxy, a kind first recognized in 2015.

Dark matter, which is invisible, is thought to comprise about a quarter of the universe’s combined mass and energy and about 80 percent of its total mass, but has not been directly observed. Scientists believe it exists based on gravitational effects it seems to exert on galaxies.

The universe’s ordinary matter includes things like gas, stars, black holes and planets, not to mention shoes, umbrellas, platypuses and whatever else you might see on Earth.

“Dark matter is not something that galaxies can sort of swap in or out of, like it’s kind of an optional thing that galaxies sometimes have and sometimes don’t,” van Dokkum said.

“We really thought that this is the essence of what a galaxy is, that galaxies are built from, initially, a bunch of dark matter and that all the stars and all the planets and everything else is just a little frost on top,” van Dokkum added.

The scientists spotted NGC1052-DF2 using the Dragonfly Telephoto Array, a telescope in New Mexico. They do not know how it formed, but have some hypotheses, including the possibility that a cataclysm within NGC1052-DF2 swept away all its gas and dark matter or that a massive nearby galaxy played havoc with it.

Van Dokkum said NGC1052-DF2 is so sparse that “it is literally a see-through galaxy.”

(Reporting by Will Dunham; Editing by Sandra Maler)

Astronomers say universe expanding faster than predicted

The 'Milky Way' is seen in the night sky over rocks in the natural reserve area of Wadi Al-Hitan, or the Valley of the Whales, at the desert of Al Fayoum Governorate, southwest of Cairo

By Irene Klotz

CAPE CANAVERAL, Fla. (Reuters) – The universe is expanding faster than previously believed, a surprising discovery that could test part of Albert Einstein’s theory of relativity, a pillar of cosmology that has withstood challenges for a century.

The discovery that the universe is expanding 5 percent to 9 percent faster than predicted, announced in joint news releases by NASA and the European Space Agency, also stirs hypotheses about what fills the 95 percent of the cosmos that emits no light and no radiation, scientists said on Thursday.

“Maybe the universe is tricking us,” said Alex Filippenko, a University of California, Berkeley astronomer and co-author of an upcoming paper about the discovery.

The universe’s rate of expansion does not match predictions based on measurements of the remnant radiation left over from the Big Bang explosion that gave rise to the known universe 13.8 billion years ago.

One possibility for the discrepancy is that the universe has unknown subatomic particles, similar to neutrinos, that travel nearly as fast as the speed of light, which is about 186,000 miles (300,000 km) per second.

Another idea is that so-called “dark energy,” a mysterious, anti-gravity force discovered in 1998, may be shoving galaxies away from one another more powerfully than originally estimated.

“This may be an important clue to understanding those parts of the universe that make up 95 percent of everything and that don’t emit light, such as dark energy, dark matter and dark radiation,” physicist and lead author Adam Riess, with the Space Telescope Science Institute in Baltimore, Maryland, said in a statement.

Riess shared the 2011 Nobel Prize in Physics for the discovery that the expansion of the universe was speeding up.

The speedier universe also raises the possibility that Einstein’s general theory of relativity, which serves as the mathematical scaffolding for calculating how the basic building blocks of matter interact, is slightly wrong, NASA said.

Riess and colleagues made their discovery by building a better cosmic yardstick to calculate distances. They used the Hubble Space Telescope to measure a particular type of star, known as Cepheid variables, in 19 galaxies beyond our own Milky Way galaxy.

How fast these stars pulse is directly related to how bright they are, which in turn can be used to calculate their distances, much like a 100-watt light bulb appears dimmer the farther away it is.

The research will be published in an upcoming edition of The Astrophysical Journal.

(Reporting by Irene Klotz; editing by Daniel Trotta and Tom Brown)