The two images below (as well as the rest of the images on this web page) were created with the attempt to reproduce what the unaided human eye would see. The same software using the same settings shows our familiar night sky and compares it to what we would see if located near a globular cluster. The difference is dramatic.
There are two caveats to mention associated with the data set: (1) the
simulated globular cluster is small, only 12 thousand stars, and (2) the
simulated globular cluster is young and contains too many bright stars.
On balance, the two effects somewhat cancel each other out, but we'll investigate
that at a later date.
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The night sky as seen from Earth (6 kb JPEG file). A 30 degree field centered on the constellation Orion. Less than a hundred stars are easily visible, including a dozen or so bright ones. |
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The night sky as seen near a globlar cluster (45 kb JPEG file). A 30 degree field viewed from a distance of 2 parsecs (6.5 light-years) away from the center of a small globular cluster. Thousands of stars fill the view. |
Please note Copyright & Fair Use at the bottom of this page.
There are 12288 stars in the data set. Each star has a 3D position, luminosity, and mass taken directly from the data set.
For this visualization, we use the 3D position and the luminosity
information about each star. For reference, and to make sure we have the
variables in the right units, the histogram plots of the positions, luminosity,
and mass of the stars are given below:
Please note Copyright & Fair Use at
the bottom of this page.
The visualization parameters are set to approximate what the human eye would see. However, some very bright stars are not well approximated beacuse they reach about 1000 times brighter than the brightest star as seen from Earth (which is Sirius, if you didn't already know). Also, these images are 480 x 480 pixels, but about 4 times as many pixels in each dimension would be required to show the scale the human eye can resolve (around 1 arc minute, or 1800 pixels across a 30 degree field).
Note that astronomers generally use parsecs instead of light-years as
a unit of distance. Rather than provide constant parenthetical references
to light-years below, we'll just state that 1 parsec is equivalent to 3.27
light-years.
430 parsecs away - This distance is equivalent to the distance from
Earth to the Orion nebula. The cluster of stars looks like a single bright
star.
100 parsecs away - The brightest stars of the cluster are apparent,
but appear very close together. It is like taking the 50 brightest stars
across our entire night sky, and squeezing them into a single degree on
the sky.
20 parsecs away - At this resolution, the cluster now begins to break
up into individual stars.
10 parsecs away - The brightest star in this image appears more than
100 times brighter than Sirius, the brightest star in our night sky.
5 parsecs away - The faint stars which dominate the globular cluster
start to become visible.
3 parsecs away - The cluster of stars fills the 30 degree field of
view.
2 parsecs away - Just outside the cluster. The positions of the stars
extend to about 1.5 parsecs from the center.
1 parsec away - Entering into the stars of the cluster.
0.5 parsec away - The core of the globular cluster now fills the 30
degree field.
0.2 parsec away - Entering into the core of the globular cluster. The
core radius is about 0.25 parsec.
At the center of the globular cluster - With the stars of the cluster
now spread all across the sky.
Please note Copyright & Fair Use at the bottom of this page.
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Flight to a Globular Cluster (1.7 MB MPEG file) A 10.7 second MPEG movie at 24 frames per second. The camera flys from 30 parsecs away to the center of the globular cluster. The sequence of images above are similar to the frames of this movie. This movie incorporates a new acceleration feature of my choreography code, so it may look a bit rough as I learn how to use this feature smoothly. |
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Circling a Globular Cluster (4.5 MB MPEG file) A 31 second MPEG movie at 24 frames per second. The camera circles once around the globular cluster from a distance of 4 parsecs, and moving at an angular speed of 12 degrees per second (1/2 degree per frame). Note that the camera is moving counterclockwise, so that the globular cluster foreground stars move to the left and background stars move to the right. I find that a psychological foreground/background confusion is prevalent here - sometimes I see the cluster spinning in the opposite direction. |
Data, images, and visualizations on this page may not be used without prior permission of the author. This includes posting on other web sites and any other electronic, print, or media distribution. Personal use is permitted under the standards of "fair use". We would appreciate an email describing such fair use so that we can justify creating more such visualizations. Comments or feedback are welcome, but we don't guarantee an answer.Credit for the visualization: Frank Summers, Space Telescope Science Institute
Credit for the dataset: Simon Portegies Zwart, Boston University