Small satellite begins the search for missing Milky-Way case

The International Space Station used HaloSat, a small satellite for the study of the Milky way’s halo, on July 13, 2018.


A small satellite has to do research on the halo of very hot gas around the milky way Galaxy — and it could help scientists trace the huge amount of missing matter in the universe.

NASA deployed the 26-lb. (12 kg) satellite, called HaloSat, on July 13, the International Space Station.

Scientists can’t find it but less than a third of all the matter that must exist in the universe. It is no dark matter; it’s just … missing. They have calculated how much matter in the universe 400,000 years after the big Bang, based on information that is encoded in the cosmic microwave background. And they have calculated how much mass they now see in galaxies, stars, planets, dust and gas. But the figures are not correct. [Our Milky Way Galaxy Has Cosmic Halo 11.4 Billion Years Old]

“We have to be the case today, we had back when the universe was 400,000 years old,” said Philip Kaaret, HaloSat the principal investigator and an astronomer at the University of Iowa, said in a statement NASA. “Where is it?”

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Scientists have made some progress in the detection of the pellets of missing matter, and they have narrowed it down to two shelters: in the galaxies themselves, or spread out in the space between them. So, scientists start close to home by searching for the matter that is missing in the Milky way.

HaloSat will try to find the missing matter map of the galaxy’s halo of superhot gas, which can reach up to 3.6 million degrees Fahrenheit (2 million degrees Celsius), according to NASA. That is hot enough to produce oxygen, X-rays, which HaloSat measure on the other side of the sky to figure out the shape of the halo and determine whether it is evenly around the Milky way, or in a flattened disk, such as a fried egg.

“If you think of the galactic halo in the fried egg model, it will be a different distribution of the brightness when you look straight up from the Earth, than if you look at a wider angle,” Keith Jahoda, a HaloSat co-researcher and a NASA astrophysicist, said in the statement. “If it’s in some quasi-spherical shape, in comparison with the dimensions of the galaxy, then you would expect it to be almost the same brightness in all directions.”

Once scientists know how the halo is in place, they can estimate the mass and determine whether it is hiding all that missing matter.

But to those measurements, HaloSat must be careful not to fall for an imposter signal. That signal is caused by the solar wind, the stream of charged particles that the sun, which provides the X-ray signatures that are similar to those of the galactic halo.

To prevent being cheated, HaloSat will switch between tasks on the basis of the place in its orbit around the Earth: If it is over the night side, will collect data and when on the daylight side, the charging and send that information home. That should HaloSat the data of a lot cleaner than the other X-ray observations, the researchers think.

The mission lasts seven months and a year.

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