Globular Clusters Surrounding the Milky Way (Artist’s Impression) Credit: ESA/Hubble, NASA, L. Calçada, M. Kormesser
In a striking example of multi-mission astronomy, measurements from the NASA/ESA Hubble Space Telescope and the ESA Gaia mission have been combined to improve the estimate of the mass of our home galaxy the Milky Way: 1.5 trillion solar masses.
The mass of the Milky Way is one of the most fundamental measurements astronomers can make about our galactic home. However, despite decades of intense effort, even the best available estimates of the Milky Way’s mass disagree wildly. Now, by combining new data from the European Space Agency (ESA) Gaia mission with observations made with the NASA/ESA Hubble Space Telescope, astronomers have found that the Milky Way weighs in at about 1.5 trillion solar masses within a radius of 129 000 light-years from the galactic centre.
Previous estimates of the mass of the Milky Way ranged from 500 billion to 3 trillion times the mass of the Sun. This huge uncertainty arose primarily from the different methods used for measuring the distribution of dark matter — which makes up about 90% of the mass of the galaxy. ...
Ergo: at almost 5 times the distance that the Sun is from the Galactic Center
the "almost constant" orbital velocity has only dropped by about one sixth
(; hence, taking 6 times as long to orbit the galaxy than the Sun).
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Arp 271 is a pair of interacting spiral galaxies: NGC 5426 (the more oblique galaxy at left) and NGC 5427 (the nearly face-on spiral galaxy at right). Together they are about 130,000 light-years across and located some 90 million light-years away towards the constellation of Virgo.
The galaxies are in the throes of a slow but disturbing interaction, that began likely a several million years ago. These twin galaxies — which have similar sizes, masses, structures, and shapes with expansive arms and a compact core – appear undisturbed. But the mutual pull of gravity has already begun to alter and distort their visible features.
So are the Milky Way and Andromeda also similar in mass and size, if not in structure and shape?