
Our Part of the Milky Way Is Bigger Than Previously Thought - wrongc0ntinent
http://news.nationalgeographic.com/2016/09/milky-way-local-arm-four-times-bigger-than-expected/
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f_allwein
Well, I suppose we're still at the unfashionable end of the western spiral arm
of the Galaxy...

[http://www.goodreads.com/quotes/54481-far-out-in-the-
unchart...](http://www.goodreads.com/quotes/54481-far-out-in-the-uncharted-
backwaters-of-the-unfashionable-end)

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nashashmi
What does it mean by saying "our section of the Milky Way galaxy"? If the
section is somehow larger, does that mean that the Milky Way galaxy is also
larger?

~~~
qbrass
The Milky Way is a spiral galaxy and Earth is located on one of the arms of
the spiral.

[https://en.wikipedia.org/wiki/File:Artist%27s_impression_of_...](https://en.wikipedia.org/wiki/File:Artist%27s_impression_of_the_Milky_Way_\(updated_-
_annotated\).jpg)

The Earth is on that little strip at the bottom center of that picture, which
looks like it's crossing between two of the larger arms.

Because the galaxy is disc-like and Earth is located about halfway between the
center of the disc and it's edge, we're not in a great place to get a good
perspective of how the galaxy actually looks. We basically watch stuff spin
around us and try to estimate what it looks like from a top-down view.

The study concludes that parts of what we previously attributed to other arms
actually belong to the arm that Earth is located on, making the arm longer
than previously estimated.

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ramgorur
the answer here has more background:

[http://astronomy.stackexchange.com/questions/10175/how-
many-...](http://astronomy.stackexchange.com/questions/10175/how-many-arms-
does-the-milky-way-galaxy-have)

~~~
acqq
Thanks! It also has some pictures, which more commenters expected to see.

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amoruso
Here's what they're talking about, for those who want a picture:

[https://en.wikipedia.org/wiki/Orion_Arm](https://en.wikipedia.org/wiki/Orion_Arm)

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Pxtl
This article really needed illustrations.

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siquick
Noob here - how do they know what the Milk Way looks like?

~~~
acqq
The starting principle is simple, then the scientists build a lot of clever
stuff, the telescopes on Earth, the telescopes on the satellites and the
remote controlled radio telescopes...

Parallax. Telescopes.

[https://medium.com/starts-with-a-bang/how-do-we-know-the-
dis...](https://medium.com/starts-with-a-bang/how-do-we-know-the-distance-to-
the-stars-c7af9035a866)

"the same math that enables you to hold your thumb at arm’s length, close one
eye and then switch eyes and watch your thumb appear to shift, allowed us to
measure the distances to the stars."

"Known as parallax, the fact that our planet’s orbit is some 300 million
kilometers in diameter around the Sun means that if we view the stars today
versus six months from now, we’ll see the closest stars appear to shift
position in the sky relative to the other, more distant stars."

There's more in the link above. Then...

Satellites.

[http://news.nationalgeographic.com/2016/09/gaia-milky-way-
ma...](http://news.nationalgeographic.com/2016/09/gaia-milky-way-maps-billion-
stars-atlas-space-science/)

"For thousands of years, astronomers from the ancient Babylonians to Tycho
Brahe had preoccupied themselves with noting the stars’ precise locations, a
crucial foundation to understanding the cosmos. But the field sputtered in the
1960s, when scientists reached the smallest parallaxes that Earth-based
telescopes could measure, stymied by interference from our rippling
atmosphere.

It wasn’t until the 1980s and 1990s that the ESA satellite Hipparcos took
astrometry to space, where it ultimately measured the precise distances of
more than 100,000 stars. Gaia is even better: Hipparcos’s gaze reached only as
far as 1,600 light-years away, barely leaving our celestial backyard, but Gaia
is able to spy on stars up to 30,000 light-years away."

Remote controlled radio telescopes across the Earth, as in the article we
comment to:

[https://science.nrao.edu/facilities/vlba](https://science.nrao.edu/facilities/vlba)

"The Very Long Baseline Array (VLBA) is an interferometer consisting of 10
identical antennas on transcontinental baselines up to 8000 km (Mauna Kea,
Hawaii to St. Croix, Virgin Islands). The VLBA is controlled remotely from the
Science Operations Center in Socorro, New Mexico. Each VLBA station consists
of a 25 m antenna and an adjacent control building. The received signals are
amplified, digitized, and recorded on fast, high capacity recorders. The
recorded data are sent from the individual VLBA stations to the correlator in
Socorro."

"Precision astrometry is a VLBA science centerpiece. The relative astrometric
accuracy of ~ 10 micro-arcseconds achievable with the VLBA is better than what
the Gaia satellite is designed to achieve for most stars in its catalog
(scheduled for release after 2015"

~~~
nonbel
>"math that enables you to hold your thumb at arm’s length"

This person seems to be using a non-standard definition of "math".

~~~
acqq
The clearer formulation would probably be: the same effect that we see by
closing one then another eye is seen from the Earth when we look at the stars
months apart, and the formulas that could be derived using the distance of
your eyes and your arm can also be applied to the cosmic distances.

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thpalmear
When it comes to the Universe/Multiverse, everything is always bigger than we
think.

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awais1122
great article

