- 2097 -
Gaia, mapping the stars in the Milky Way. The Gaia
spacecraft launched in 2013 has cataloged nearly 1,700,000,000 stars in our
Milky Way Galaxy and beyond. Gaia has made a
significant contribution to our knowledge of stars in the Milky Way. Yet, it has only mapped 1% of the stars. This alone is information overload. The data set of position and motion is a 3-D
map of 1,300,000,000 stars.
-
-
-
----------------------------- 2097 - Gaia, mapping the stars in the Milky
Way.
-
- We can see 2,000
to 6,000 stars in the night sky depending on how clear the atmosphere is and if
you are using binoculars. What if you were using an orbiting spacecraft? The Gaia spacecraft launched in 2013 has
cataloged nearly 1,700,000,000 stars in our Milky Way Galaxy and beyond.
-
- This spacecraft is charting the entire
sky. It can measure stars’ motions and distances,
properties which haven’t been inventoried on such a large scale before. The spacecraft is in a parking orbit on the
side of the Earth opposite the Sun. This
minimizes the Sun's rays interfering with the star measurement exposures.
-
- Based on many
separate observations of individual stars over 3 years, measurements can be
calculated backward and forward over time.
The Gaia spacecraft's two optical telescopes and three other instruments
can measure star brightness, star temperature, and star composition. The star's color reveals the data to
calculate surface temperatures.
-
- The
telescopes can very accurately measure stars 30,000 lightyears away. The resolution is equivalent to a person on
Earth spotting a penny on the Moon. The
data collected allows calculations of the radial velocity of each star. This is the speed that the star coming
directly toward or directly away from the Earth. These precise measurements of stellar motions
improve our understanding of our galaxy's history and evolution.
-
- In addition to the stars, over 14,099 asteroids
have been tracked in their orbits inside our solar system.
-
- Further and
continued analysis of all this data may bring new clues about the nature and
distribution of Dark Matter. Much of the Milky Way’s mass is hidden in the form
of a Dark Matter halo, a shroud of matter that is invisible except for its
gravitational pull. But scientists can gauge the galaxy’s unseen bulk by
observing objects moving at the outskirts of the galaxy.
-
- Exoplanet
updates are also on the agenda. Because NASA’s exoplanet-hunting Kepler
telescope has limited ability in gauging how big stars are, the diameters of
exoplanets passing in front of those stars were not well understood. And knowing both the brightness and distance
of a star helps determine its size.
-
- A
disagreement over how fast the universe is expanding persists. Gaia
data reinforced the discrepancy in results between two of the methods for
measuring the expansion rate.
-
- One of these
techniques involves estimating the distances of exploding stars, or supernovas,
and measuring how their light is stretched by the expansion of space. Gaia
improved distance estimates for variable stars called Cepheids, which
scientists use to estimate how far away the supernovas are has resulted in an
expansion rate mismatch is now slightly worse.
-
- The Milky Way
looks so passive from our vantage point.
But there is a lot of violent activity ripping up clumps of stars and
stretching them into strands known as stellar streams.
- Gaia’s
measurements of stars’ motions, combined with information about their
brightness and color allows astronomers to pinpoint which stars were going with
the flow of the stellar stream and reveals gaps where stars seem to be missing.
That could indicate the stream was disturbed in the past by a close encounter
with a clump of dark matter.
-
- Some fast-moving
stars are speeding through the galaxy at speeds of more than 1,000 kilometers
per second. Such high speeds must have
been created by some type of enormous explosion. In one theory, two white dwarfs swirl around
one another as one steals material from the other. The thief eventually
explodes and its partner is flung away at these enormous speeds.
-
-
Gaia has made a significant contribution to our knowledge of stars in
the Milky Way. Yet, it has only mapped
1% of the stars. This alone is
information overload. The data set of
position and motion is a 3-D map of 1,300,000,000 stars.
-
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------------------------- Wednesday, June 6, 2018
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