Scientists discover date when a dwarf galaxy and Milky approach collided from a single star

The dwarf galaxy Gaia-Enceladus collided with the Milky Manner in all probability roughly 11.5 billion years in the past. The Milky Manner has encountered a number of different galaxies in its 13.5 billion-year historical past. Certainly one of them is the dwarf galaxy Gaia-Enceladus. To grasp how this occasion affected our galaxy and adjusted it completely, it is very important reliably date the collision.

A group of researchers together with scientists from the Max Planck Institute for Photo voltaic System Analysis (MPS) in Germany for the primary time utilizing a single star affected by the collision as a clue for courting.

Utilizing observational information from ground-based observatories and house telescopes, the scientists led by the College of Birmingham have been capable of decide the age of the star and the function it performed within the collision. The analysis group describes its ends in the difficulty of Nature Astronomy.

 Scientists find date when a dwarf galaxy and Milky way collided from a single star

The Milky Manner as seen from Yellowstone Nationwide Park. Picture courtesy: Neal Herbert/Flickr

The researchers led by Prof. Dr Invoice Chaplin of the College of Birmingham turned their consideration to a single star: nu Indi is discovered within the constellation Indus; with an obvious brightness akin to that of Uranus, it’s seen even to the bare eye and will be simply studied intimately.

“The space telescope TESS collected data from nu Indi already in its first month of scientific operation,” says Dr Saskia Hekker, head of the analysis group “Stellar Ages and Galactic Evolution (SAGE)” at MPS and co-author of the brand new examine.

The house telescope was launched in 2018 to carry out a full-sky survey and characterise as many stars as doable. “The data from TESS allow us to determine the age of the star very accurately,” Hekker provides.

Furthermore, nu Indi supplied clues on the historical past of the collision with the dwarf galaxy Gaia-Enceladus. To reconstruct its function within the collision, the analysis group evaluated quite a few information units on nu Indi obtained with the assistance of the spectrographs HARPS (Excessive Accuracy Radial velocity Planet Searcher) and FEROS (Fiber-fed Prolonged Vary Optical Spectrograph) of the European Southern Observatory, the Galaxy Evolution Experiment of the Apache Level Observatory in New Mexico, and ESA’s Gaia Area Telescope. This allowed them to specify each the chemical composition of the star and its motion throughout the galaxy with nice precision.

The dwarf galaxy Gaia-Enceladus also known as Gaia Sausage. Image credit: Wikipedia

The dwarf galaxy Gaia-Enceladus also referred to as Gaia Sausage. Picture credit score: Wikipedia

The cosmic detective work produced a transparent image: nu Indi has been a part of the halo, the outer area of the Milky Manner, and the collision modified its trajectory. “Since the motion of nu Indi was affected by the collision, it must have taken place when the star was already formed,” Chaplin explains the road of argument. The age of the star, subsequently, places a constraint on the time of the collision.

To find out the age of a star, researchers use its pure oscillations, which will be noticed as brightness fluctuations. “Similar to the way seismic waves on Earth allow conclusions about the interior of our planet, stellar oscillations help us to reveal the internal structure and composition of the star and thus its age,” explains MPS scientist and co-author Dr Nathalie Themessl.

The calculations carried out by MPS researchers and different analysis teams confirmed that with a likelihood of 95 p.c the galaxy merger should have occurred 13.2 billion years in the past. With a likelihood of 68 p.c, the collision befell roughly 11.5 billion years in the past. “This chronological classification not only helps us to understand how the collision changed our galaxy,” says Hekker. “It additionally offers us a way, of how collisions and mergers impacted different galaxies and influenced their evolution.

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