Galactic Crash With Sagittarius May Have Triggered the Formation of Our Solar System

Collisions With Sagittarius Trigger Star Formation

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The Sagittarius dwarf galaxy has actually been orbiting the Milky Way for billions for many years. As its orbit around the 10,000 more enormous Milky Way slowly tightened up, it began hitting our galaxy’s disc. The 3 understood accidents in between Sagittarius and the Milky Way have, according to a brand-new research study, set off significant star development episodes, among which might have generated the Solar System. Credit: ESA

The development of the Sun, the Solar System and the subsequent introduction of life on Earth might be a repercussion of an accident in between our galaxy, the Milky Way, and a smaller sized galaxy called Sagittarius, found in the 1990s to be orbiting our stellar house.

Astronomers have actually understood that Sagittarius consistently smashes through the Milky Way’s disc, as its orbit around the galaxy’s core tightens up as an outcome of gravitational forces. Previous research studies recommended that Sagittarius, a so called dwarf galaxy, had actually had an extensive impact on how stars relocate the Milky Way. Some even declare that the 10,000 times more enormous Milky Way’s hallmark spiral structure may be an outcome of the a minimum of 3 understood crashes with Sagittarius over the previous 6 billion years.

A brand-new research study, based upon information collected by ESA’s galaxy mapping powerhouse Gaia, exposed for the very first time that the impact of Sagittarius on the Milky Way might be much more considerable. The ripples brought on by the accidents appear to have actually set off significant star development episodes, among which approximately accompanied the time of the development of the Sun some 4.7 billion years back.

“It is known from existing models that Sagittarius fell into the Milky Way three times – first about five or six billion years ago, then about two billion years ago, and finally one billion year ago,” states Tomás Ruiz-Lara, a scientist in Astrophysics at the Instituto de Astrofísica de Canarias (IAC) in Tenerife, Spain, and lead author of the brand-new research study released in Nature Astronomy.

“When we looked into the Gaia data about the Milky Way, we found three periods of increased star formation that peaked 5.7 billion years ago, 1.9 billion years ago and 1 billion years ago, corresponding with the time when Sagittarius is believed to have passed through the disc of the Milky Way.”

Sagittarius Collisions Trigger Star Formation in Milky Way

Sagittarius accidents set off star development in Milky Way. Credit: ESA

Ripples on the water

The scientists took a look at luminosities, ranges and colors of stars within a sphere of about 6500 light-years around the Sun and compared the information with existing excellent advancement designs. According to Tomás, the idea that the dwarf galaxy might have had such a result makes a great deal of sense.

“At the beginning you have a galaxy, the Milky Way, which is relatively quiet,” Tomás states. “After an initial violent epoch of star formation, partly triggered by an earlier merger as we described in a previous study, the Milky Way had reached a balanced state in which stars were forming steadily. Suddenly, you have Sagittarius fall in and disrupt the equilibrium, causing all the previously still gas and dust inside the larger galaxy to slosh around like ripples on the water.”

In some locations of the Milky Way, these ripples would cause greater concentrations of dust and gas, while clearing others. The high density of product in those locations would then set off the development of brand-new stars.

“It seems that not only did Sagittarius shape the structure and influenced the dynamics of how stars are moving in the Milky Way, it has also led to a build-up of the Milky Way,” states Carme Gallart, a co-author of the paper, likewise of the IAC. “It seems that an important part of the Milky Way’s stellar mass was formed due to the interactions with Sagittarius and wouldn’t exist otherwise.”

Dwarf galaxy accidents make stars from in Milky Way

The birth of the Sun

In reality, it appears possible that even the Sun and its worlds would not have actually existed if the Sagittarius dwarf had actually not gotten caught by the gravitational pull of the Milky Way and ultimately smashed through its disc.

“The Sun formed at the time when stars were forming in the Milky Way because of the first passage of Sagittarius,” states Carme. “We don’t know if the particular cloud of gas and dust that turned into the Sun collapsed because of the effects of Sagittarius or not. But it is a possible scenario because the age of the Sun is consistent with a star formed as a result of the Sagittarius effect.”

Every accident removed Sagittarius of a few of its gas and dust, leaving the galaxy smaller sized after each passage. Existing information recommend that Sagittarius may have travelled through the Milky Way’s disc once again rather just recently, in the last couple of hundred million years, and is presently really near to it. In reality, the brand-new research study discovered of a current burst of star development, recommending a possible brand-new and continuous wave of excellent birth.

According to ESA Gaia task researcher Timo Prusti, such comprehensive insights into the Milky Way’s star development history wouldn’t be possible prior to Gaia, the star-mapping telescope released in late 2013, whose 2 information releases in 2016 and 2018 changed the research study of the Milky Way.

“Some determinations of star formation history in the Milky Way existed before based on data from ESA’s early 1990s Hipparcos mission,” states Timo. “But these observations were concentrated on the instant community of the Sun. It wasn’t actually representative therefore it couldn’t reveal those bursts in star development that we see now.

“This is really the first time that we see a detailed star formation history of the Milky Way. It’s a testament to the scientific power of Gaia that we have seen manifest again and again in countless ground-breaking studies in a period of only a couple of years.”


“The recurrent impact of the Sagittarius dwarf on the star formation history of the Milky Way” by Tomás Ruiz-Lara, Carme Gallart, Edouard J. Bernard and Santi Cassisi, 25 May 2020, Nature Astronomy.
DOI: 10.1038/s41550-020-1097-0

“Uncovering the birth of the Milky Way through precise excellent ages with Gaia’ by Carme Gallart, Edouard J. Bernard, Chris B. Brook, Tomás Ruiz-Lara, Santi Cassisi, Vanessa Hill and Matteo Monelli, 22 July 2019, Nature Astronomy.
DOI: 10.1038/s41550-019-0829-5