HaloSat will help scientists to understand whether the missing mass of the universe lies inside galactic halos or not.

Humanity is exploring every dimension of the universe in order to know more and more about our surroundings. The amount of ‘normal matter’ is very less when compared with the total volume of space around us. Astronomers are trying different options for finding the missing matter of the universe but they haven’t found much till date. According to the calculations based on the observations of the Cosmic Microwave Background (CMB), only 5% of the material in our universe is made up of normal matter (protons, neutrons, and other sub-atomic particles) while dark matter accounts for 25% of it. Scientists hardly know anything about this strange substance. The remaining 70% is filled by a negative pressure called Dark Energy, which accelerates the expansion of the universe.

 The CMB is the oldest known light in the universe whose radiations are 400,000 years old. The estimated masses of all the objects including planets, galaxies, stars, and gas don’t fulfill the estimates of cosmologists. Approximately, all these things account for only half of what should have been present. Scientists believe that the hot gas located either in galactic halos or in the space between galaxies could explain the missing matter of our universe. Philip Kaaret, the Principal Investigator of the HaloSat talked about that and said,

“We should have all the matter today that we had back when the universe was 400,000 years old. Where did it go? The answer to that question can help us learn how we got from the CMB’s uniform state to the large-scale structures we see today.”

HaloSat is a newly-launched CubeSat Mission which will observe the gas in the halo of the Milky Way. The temperature of this gas is around 2 million degrees Celsius and that’s the reason why X-rays are emitted from such regions. Oxygen releases all of its 8 electrons at such temperatures which lead to these radiations. HaloSat has been assigned the task to measure these X-rays. Prior to this mission, different X-ray telescopes like Chandra X-ray Observatory and the Neutron star Interior Composition Explorer have analyzed smaller patches of the sky. However, the scope of HaloSat is much broader as it will observe 100 square degrees at a time. Keith Jahoda, an Astrophysicist at the Goddard Space Flight Center of NASA and a Co-investigator of this mission, explained the benefits of such an inspection in the following words:

“If you think of the galactic halo in the fried egg model, it will have a different distribution of brightness when you look straight up out of it from Earth than when you look at wider angles. If it’s in some quasi-spherical shape, compared to the dimensions of the galaxy, then you expect it to be more nearly the same brightness in all directions.”

HaloSat has a mass of about 12 kilograms and its dimensions are 10x20x30 centimeters. It is a first-of-its-kind mission because none of the CubeSat Missions, prior to this one, were linked with Astrophysics. It will minimize the effects of the X-rays produced by the exchange of the solar wind charge. These radiations are generated when charged particles, coming from the Sun, interact with the neutral atoms found in the atmosphere of the Earth. Researchers are hopeful that they will find a similar spectrum from the galactic halo of Milky Way. Kip Kuntz, a Co-investigator of the HaloSat Mission from John Hopkins University acknowledged that by saying,

“Every observation we make has this solar wind emission in it to some degree, but it varies with time and solar wind conditions. The variations are so hard to calculate that many people just mention it and then ignore it in their observations.”

HaloSat revolves around Earth in a 90-minute orbit. It will collect most of the data in the nighttime half of its orbit. During the daytime cycle, the satellite will send data to the Wallops Flight Facility of NASA and recharge itself by making use of the solar panels attached to it. Wallops Facility feeds the data to the operations control center of the mission at Blue Canyon Technologies.