When it came to pulling stars out, Milky Way's nearest galactic neighbors began a slow start. But they are gaining momentum now.
By making the first detailed chemical maps of a galaxy beyond our own, the researchers found that star formation in the large and small magellanic clouds has spiked lately, after a delay. The new results not only provide insight into the most abundant type of galaxy in the universe, but also help improve understanding of Growth development.
Although the large and small magellanic clouds (LMC and SMC respectively) are only 150,000 light-years from the Milky Way – right next door, astronomically – astronomers have found it difficult to study their composition. [Dizzying Array of Stars Dazzles in New Hubble Photo]
"It has been challenging to map their full structure," said David Nidever, an astronomer at Montana State University, last month at the 23rd American Astronomical Society meeting in Seattle. Nidever and his colleagues used the study of the experimental patient Galaxy Evolution Experiment 2 (APOGEE-2) to obtain accurate observations of 5,000 stars in Magellanic Clouds. By mapping out how heavy elements are distributed through the stars of the galaxy, astronomers were able to model roughly when generations of stars were born.
"With this new ability, we can study Magellanic Clouds like never before," Nidever said.
A slow start
Only visible from the southern hemisphere, LMC and SMC were named for the explorer Ferdinand Magellan, who led the first European expedition to circulate the globe. The couple are dwarf salmon, smaller collections of stars that can hold anywhere from 1,000 to 1,000,000,000 times the sun's mass in gas, dust and stars, according to Nidver's paper on the new work. The Milky Way is surrounded by dozens of known dwarf galaxies, and scientists suspect that there are dozens more hidden in the edge, their tiny shaped shapes make it difficult to detect.
Though they qualify as dwarf galaxies, LMC and SMC are exceptional and build stars much slower than their counterparts. The difference has been a long mystery for researchers.
"There must be a relationship between the mass of the galaxy and early star formation speeds," Nidever told Space.com. "Magellanic Clouds are falling far away from the trend."
Sloan Digital Sky Survey's APOGEE-1 project studied the Northern Hemisphere Milky Way from 2011 to 2014, giving "unprecedented insight into the galaxy's dynamic structure and chemical history," according to Sloan's website. Based in New Mexico, the first version of APOGEE was limited to the northern hemisphere.
In 2017, the almost identical instrument APOGEE-2 was installed at Las Campanas Observatory in Chile. The instrument began to observe LMC and SMC that year.
The first stars are formed by dense clouds of hydrogen and helium, which convert a small percentage of the gas into heavier elements. As they exploded in violent supernovae, they sowed their surroundings with these elements, which were drawn into the next generation of stars, and the bike continued – with each generation of stars converting more stock into heavier elements.
With APOGEE-2, Nidever and his colleagues were able to probe the chemical makeup of thousands of stars in LMC and SMC. The researchers folded this makeup into simulations to determine how long it took generations of stars to form. In this way, they could reconstruct the star station history for both galaxies.
Unlike the Milky Way, Magellanic Clouds came to a slow start and built new stars about 50 times slower than our own galaxy, Nidever said. But despite this lazy start, the LMC had a new kick that caused a six-fold jump in new stars.
"It's never too late to become active," Nidever said.
What caused the latest uptick that happened about 2 billion years ago? Nidever said the most likely source is that a recent brush with SMC burned starburst in the larger dwarf galaxy.
"We can see features that they have interacted with in their structure," Nidever said.
Clouds & # 39; slow start as opposed to other dwarf galaxies around the Milky Way. Star formation speeds in the pair are even lower than expected for their mass, Nidever said.
"It's kind of a mystery," he said.
The difference is probably due to different environments. Most of the dwarf galaxies studied so far have made several trips around the Milky Way. Their gravity interactions with our galaxy may have helped make their gas stars.
However, LMC and SMC most likely take their very first spin around the Growth Path, according to previous studies. That means they spent about 10 billion years building stars isolated, without a massive galaxy to increase their starbirth, the researchers said. Only in the last few billion years have the couple started interacting more frequently with the Milky Way and with each other and increasing how quickly they build their stars.
But things have just begun for LMC and SMC. In about 2.5 billion years, the LMC will merge with the Milky Way and set aside a flurry of star formation.
"Many of the stars [in the Magellanic Clouds] will be thrown into the halo of the Milky Way and will dramatically affect the makeup of his halo, "Nidever said.
The fusion will cause an outbreak of star formation in the remaining gas and dust of the Magellanic Clouds, he added. After beating such a slow start, the couple will pack their last year in a storm of star fireworks.
The research is submitted to the Astrophysical Journal and is available on the preprint server arXiv.