Γαλαξίες παρόμοιοι με τον δικό μας. Tracing the growth of Milky Way-like galaxies

Η εξέλιξη γαλαξιών (σαν τον δικό μας). Μια σύνθεση φωτογραφιών από το διαστημικό τηλεσκόπιο Hubble. This composite image shows examples of galaxies similar to our Milky Way at various stages of construction over a time span of 11 billion years. The galaxies are arranged according to time. Those on the left reside nearby; those at far right existed when the cosmos was about 2 billion years old. The bluish glow from young stars dominates the color of the galaxies on the right. The galaxies at left are redder from the glow of older stellar populations. Astronomers found the distant galaxies in two Hubble Space Telescope surveys: 3D-HST and the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, or CANDELS. The observations were made in visible and near-infrared light by Hubble's Wide Field Camera 3 and Advanced Camera for Surveys. The nearby galaxies were taken from the Sloan Digital Sky Survey. This image traces Milky Way-like galaxies over most of cosmic history, revealing how they evolve over time. Hubble's sharp vision resolved the galaxies' shapes, showing that their bulges and disks grew simultaneously. Credit: NASA, ESA, P. van Dokkum (Yale University), S. Patel (Leiden University), and the 3D-HST Team

Mια σύνθετη εικόνα που περιέχει γαλαξίες παρόμοιους με τον δικό μας στα διάφορα στάδια της εξέλιξής των μέσα σε ένα χρονικό διάστημα 11 δισεκατομμυρίων χρόνων.

“For the first time, we have direct images of what the Milky Way looked like in the past,” said Pieter van Dokkum, a co-author of the study and an Astronomer at Yale University. “Of course, we can’t see the Milky Way itself in the past. We selected galaxies billions of light-years away that will evolve into galaxies like the Milky Way. By tracing the Milky Way’s siblings, we find that our galaxy built up 90 percent of its stars between 11 billion and 7 billion years ago, which is something that has not been measured directly before.” (Image courtesy NASA/ESA)

Οι γαλαξίες είναι τοποθετημένοι συναρτήσει του χρόνου. Αριστερά βρίσκονται γαλαξίες παρόμοιας ηλικίας με τον δικό μας, ενώ προς τα δεξιά περιέχονται γαλαξίες μεγαλύτερης ηλικίας. Η γαλαζωπή λάμψη από τα νέα άστρα κυριαρχεί στο χρώμα των γαλαξιών προς τα δεξιά, ενώ το χρώμα των γαλαξιών αριστερά είναι προς το ερυθρό, εξαιτίας της λάμψης των γηραιότερων άστρων.