Where celestial neighbors are concerned, Andromeda is right next door. This spiral galaxy located 780 kilo parsecs from Earth has just revealed one of its better-kept mysteries. Its massive halo of gas.
This discovery is yet another reason why the scientific community is indebted to the Hubble Space Telescope, which has been providing valuable scientific data since its launch into orbit in 1990.
A somewhat fortuitous discovery, Andromeda’s gigantic halo was only stumbled across after scientists reviewed the archival data of distant quasars. And where halos are concerned, Andromeda’s one is a big deal. According to complex estimates, the halo’s mass is believed to include over 50 percent of the stars located in the galaxy itself.
In fact, as opposed to previous estimates, Andromeda’s halo is now believed to be 1,000 more massive and six times larger than what scientists had previously thought, stretching out approximately 1,000,000 light-years from Andromeda towards the Milky Way.
What is a Galaxy Halo?
According to Notre Dame University professor Nicolas Lehner, a galaxy halo represents the gaseous atmosphere surrounding spiral galaxies such as our own. Depending on the specific properties of each type of halo, star formation rates differ.
Consequently, astronomers now have the opportunity of gaining further insight into the evolution of giant spiral galaxies, their star formation patterns as well as their structure.
Previous research suggests that galaxies and their respective halos form at approximately the same time. Curiously, though, Andromeda’s halo is believed to also be enriched with heavy elements.
Such heavy elements can stem from a variety of celestial events, however, the most likely source is supernova activity. Massive stars that run out of fuel turn into supernovae and experience world-shattering explosions.
After their explosions, the heavy elements remaining in the galactic disk are carried by stellar winds further into space, including the galaxy’s halo.
Lehner explains that, if the halo would be looked at with the naked eye, it would have a diameter of 100 times that of our Moon in the night’s sky. If you’d like a visual representation of that type of diameter, take two basketballs and hold them at arm’s length. They cover a patch of sky equivalent to that of 100 times the Moon’s diameter.
Looking at Andromeda’s Halo
Researchers also attempted to catch better glimpses of this unique halo. Therefore, they searched for bright objects in the halo’s background and analyzed how the halo’s gas changed the light stemming from that chosen celestial object. Quasars are ideal bright background objects because they are the bright cores of active galaxies.
“As the light from the quasars travels toward Hubble, the halo’s gas will absorb some of that light and make the quasar appear a little darker in just a very small wavelength range,” study co-investigator Christopher Howk explains.
Complex formulae allow researchers to then measure the brightness difference corresponding to that specific wavelength rage. This specific brightness dip later allows scientists to understand exactly how much gas is located between the quasar and its observer.
Could the Milky Way also Have a Halo?
Complex models and large scale simulations show that halos form at the same time as their host galaxies, so the assumption that the Milky Way also has a halo similar to that of Andromeda isn’t far-fetched.
However, due to the fact that our Earth is inside the Milky Way galaxy, scientists cannot perform similar determinations in order to prove an equally massive halo around our home galaxy.
The halo’s discovery is quite thrilling. The vast intergalactic space between Andromeda and the Milky Way is by no means a void. Hot stellar gas fills the gap and are already preceding the one-of-a-kind merger awaiting these two spiral galaxies in a few billion years.
Latest posts by Alan O’Leary (see all)
- Woman Found Alive After Missing for 42 Years - Mar 12, 2019
- October Will Welcome The Draconid Meteor Shower And The Orionids - Mar 12, 2019
- Scientists Are At A Loss After Unearthing A Porpoise Grave - Mar 12, 2019