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Beyond the Milky Way — a game-changing discovery

As I’ve noted elsewhere (Beyond the infinity of black holes), it wasn’t long ago — maybe a 100 years or so, that our view of the cosmos was much more circumscribed. Those who studied cosmology — physicists, astronomers, et al, viewed our cosmos in a much different way, at a much different scale — basically an island universe: Earth, the solar system and the Milky Way. We existed in a galaxy, but a singular one.

Now, almost one hundred years later, it is difficult to fully appreciate how much our picture of the universe has changed in the span of a single human lifetime. As far as the scientific community in 1917 was concerned, the universe was static and eternal, and consisted of a single galaxy, our Milky Way, surrounded by a vast, infinite, dark, and empty space. This is, after all, what you would guess by looking up at the night sky with your eyes, or with a small telescope, and at the time there was little reason to suspect otherwise. — Krauss, Lawrence. A Universe from Nothing: Why There Is Something Rather than Nothing (pp. 1-2). Atria Books. Kindle Edition.

The game-changing discovery was highlighted back in 2011 by this article “Star That Changed the Universe Shines in Hubble Photo” (May 23, 2011).

In homage to its namesake, the Hubble Space Telescope recently photographed a star that astronomer Edwin Hubble observed in 1923, changing the course of astronomy forever.

The star is a variable star that pulses brighter and dimmer in a regular pattern, which allowed scientists to determine its distance, suggesting for the first time that other galaxies exist beyond our own Milky Way.

“I would argue this is the single most important object in the history of cosmology,” said astronomer David Soderblom of the Space Telescope Science Institute in Baltimore, Md., who proposed pointing the Hubble Space Telescope at the star.

Can you say Cepheid variable?

When I get bogged down in the 10^-n scale of things, a reminder about standard candles at the other end of the scale of things helps restore my perspective on how science works — that, at its best, science moves us beyond circumscribed views.


4 thoughts on “Beyond the Milky Way — a game-changing discovery

  1. January 12, 2018, “Whirlpool Galaxy: Exploding With Supernovas.”

    M51 was first catalogued by Charles Messier in 1773 while the astronomer was plotting objects in the sky that could confuse comet-hunters. “M51” is a reference to “Messier 51,” one of about 110 entries now plotted in his Catalogue of Nebulas and Star Clusters. …

    It would take about 70 years to learn more about the fuzzy object’s structure, however. It was first discerned by William Parsons, using a 72-inch reflector telescope in 1845. “His drawing of the spiral galaxy M51 is a classic work of mid-19th-century astronomy,” said Encyclopedia Britannica of Parsons’ observations.

    Parsons’ discovery was the first so-called “spiral nebula” ever discovered, and in the five years following he found 14 more of these objects, according to the STScI. It was unclear for decades if these objects were a part of the Milky Way Galaxy or things that were independent of that.

    It wasn’t until Edwin Hubble used Cepheid variable stars to chart cosmic distances in M31 (the Andromeda Galaxy) in the 1920s that astronomers understood they were actually distant galaxies.

  2. Regarding the scale of space and time beyond the Milky Way, this brief BBC News article “Hubble scores unique close-up view of distant galaxy“(January 16, 2018) notes the discovery of one of the oldest galaxies.

    Astronomers were lucky when the orbiting observatory captured the image of a galaxy that existed just 500 million years after the Big Bang.

    The image was stretched and amplified by the natural phenomenon of gravitational lensing, unlocking unprecedented detail.

    Such objects usually appear as tiny red spots to powerful telescopes.

    Distance and age are linked in astronomy; because of the time taken for light to traverse the vast expanse in-between, we see the galaxy as it was more than 13 billion years ago.

  3. More in science news on this topic, with this February 26th article “The Universe Is Expanding Faster Than We Thought, Hubble Data Suggests.” The article includes a video by astrophysicist Paul Sutter (a frequent contributor on with some background on Cepheid variable stars and a summary chart “Three Steps to Measuring the Hubble Constant.”

    The article discusses the interplay of recent data from the Hubble Space Telescope and European Space Agency’s (ESA) Planck satellite with the Big Bang theory.

    Researchers analyzed 19 galaxies, including NGC 3972 (left) and NGC 1015 (right), which are 65 million and 118 million light-years from Earth, respectively. Both possessed pulsating stars called Cepheid variables that let researchers determine the distance to the galaxies.

    Researchers measured the universe’s expansion by calculating the distance to several very distant stars called Cepheid variables, which pulse regularly and let researchers determine the distance to them based on their brightness. The eight newly measured Cepheids are 10 times farther away than any studied previously. Then, the researchers compared the brightness of those stars to the brightness of supernovas in the same galaxies, and compare them with the brightness of supernovas that are even farther out.

  4. So, “How Many Galaxies Are There?” asks this March 19, 2018, article. “In our own cosmos … astronomers will be better able to refine the number upon the launch of the James Webb Space Telescope …”

    Whatever instrument is used, the method of estimating the number of galaxies is the same. You take the portion of sky imaged by the telescope (in this case, Hubble). Then — using the ratio of the sliver of sky to the entire universe — you can determine the number of galaxies in the universe.

    “This is assuming that there is no large cosmic variance, that the universe is homogenous,” Livio said. “We have good reasons to suspect that is the case. That is the cosmological principle.”

    “The simplest assumption to make is that if you viewed the contents of the universe with sufficiently poor vision, it would appear roughly the same everywhere and in every direction,” NASA stated. “That is, the matter in the universe is homogeneous and isotropic when averaged over very large scales. This is called the cosmological principle.”

    One example of the cosmological principle at work is the cosmic microwave background, radiation that is a remnant of the early stages of the universe after the Big Bang. Using instruments such as NASA’s Wilkinson Microwave Anisotropy Probe, astronomers have found the CMB is virtually identical wherever one looks.

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