TESS dates an ancient collision with our galaxy


Share post:

A single bright star in the constellation of Indus, visible from the southern hemisphere, has revealed new insights on an ancient collision that our galaxy the Milky Way underwent with another smaller galaxy called Gaia-Enceladus early in its history.

TESS dates an ancient collision with our galaxy
A snapshot from TESS of part of the southern sky showing the location of ν Indi (blue circle), the plane of the
Milky Way (bottom left) and the southern ecliptic pole (top). These snapshots come from data collected
in TESS observing sectors 1, 12 and 13 [Credit: J. T. Mackereth]

An international team of scientists led by the University of Birmingham adopted the novel approach of applying the forensic characterisation of a single ancient, bright star called ν Indi as a probe of the history of the Milky Way. Stars carry “fossilized records” of their histories and hence the environments in which they formed. The team used data from satellites and ground-based telescopes to unlock this information from ν Indi. Their results are published in the journal Nature Astronomy.

The star was aged using its natural oscillations (asteroseismology), detected in data collected by NASA’s recently launched Transiting Exoplanet Survey Satellite (TESS). Launched in 2018, TESS is surveying stars across most of the sky to search for planets orbiting the stars and to study the stars themselves. When combined with data from the European Space Agency (ESA) Gaia Mission, the detective story revealed that this ancient star was born early in the life of the Milky Way, but the Gaia-Enceladus collision altered its motion through our Galaxy.

The animation shows a schematic of the orbits of three stars within our Galaxy the Milky Way – whose extent is marked by
 the dashed line — as viewed from above (left) and side-on (right), projected over the next half a billion years. The three 
stars are: nu Indi, the subject of the Nature Astronomy paper; a star accreted from Gaia-Enceladus (after its collision 
with the Milky Way); and the Sun. The accreted star came from outside the Galaxy, as part of the Gaia-Enceladus 
collision, and so has a very elongated orbit. The collision affected the motion and orbit of nu Indi. 
Notice how its orbit is quite different to that of the Sun [Credit: J. T. Mackereth] 

Bill Chaplin, Professor of Astrophysics at the University of Birmingham and lead author of the study said: “Since the motion of ν Indi was affected by the Gaia-Enceladus collision, the collision must have happened once the star had formed. That is how we have been able to use the asteroseismically-determined age to place new limits on when the Gaia-Enceladus event occurred.”

Co-author Dr Ted Mackereth, also from Birmingham, said: “Because we see so many stars from Gaia-Enceladus, we think it must have had a large impact on the evolution of our Galaxy. Understanding that is now a very hot topic in astronomy, and this study is an important step in understanding when this collision occurred.”

Bill Chaplin added: “This study demonstrates the potential of asteroseismology with TESS, and what is possible when one has a variety of cutting-edge data available on a single, bright star”

The research clearly shows the strong potential of the TESS programme to draw together rich new insights about the stars that are our closest neighbours in the Milky Way. The research was funded by the Science and Technology Facilities Council and the European Research Council through the Asterochronometry project.

Source: University of Birmingham [January 13, 2020]



Related articles

The salt of the comet

More than 30 years ago, the European comet mission Giotto flew past Halley's comet. The Bernese ion mass...

NASA’s Juno Spacecraft Spots Jupiter’s Great Red Spot

Images of Jupiter's Great Red Spot reveal a tangle of dark, veinous clouds weaving their way through a...

NASA missions unmask magnetar eruptions in nearby galaxies

On April 15, 2020, a brief burst of high-energy light swept through the solar system, triggering instruments on...

Mystery gas discovered near center of Milky Way

An international team of researchers have discovered a dense, cold gas that's been shot out from the centre...

New study estimates the odds of life and intelligence emerging beyond our planet

Humans have been wondering whether we alone in the universe since antiquity. We know from the geological record...

Breakthrough Listen releases catalog of “Exotica” targets for the search for intelligent life and investigations of new astrophysics

Breakthrough Listen, the initiative to find signs of intelligent life in the universe, today released an innovative catalog...

Little star sheds light on young planets

Astronomers from the Department of Physics at the University of Tokyo discovered a dense disk of material around...

A step closer to understanding the birth of the sun

Researchers are a step closer to understanding the birth of the sun. Published in Science, the team led...