I once accidentally took a photo with one of the most important stars of the Universe …
This star highlighted in the photo is called M31_V1 and lives in the galaxy of Andromeda. Andromeda – AKA M31 – is the closest galaxy to our own Milky Way. But before that it was not known as a galaxy, it was called the Nebula of Andromeda. Before this particular Andromeda star was studied by Edwin Hubble, the name of the Hubble Space Telescope, we didn’t really know if other galaxies even existed. Think about it! More recently, a hundred years ago, we thought the Milky Way could be the ENTIRE Universe. Even then … it’s pretty big. The Milky Way is about 150,000 light-years away. The light-year is about 10 trillion kilometers, so even at the speed of light, crossing the Milky Way would take almost as long as humans existed on planet Earth. M31_V1 has changed all that.
This star of Andromeda has the name “V” because it is known as kefid variable. Cepheid variables can be used as a “standard candle” to measure distance through the Universe. We usually know how brightly changing stars. So if we compare two of them and one is much weaker than the other, we can conclude that it is further in space. In 1924, using this technique, Hubble measured the light of V1 and 35 subsequent variable stars to measure the distance to Andromeda in an incredible 900,000 light-years… too far to be part of our own galaxy. I didn’t imagine capturing the same star in my field of vision until it was pointed out by Dr. Howard Trottier, who founded the SFU Trottier Observatory, where I captured the image.
With improved imaging techniques and more accurate measurements, we now know that Andromeda is more than 2.4 million light-years away. However, Hubble’s values of 900,000 liters were enough to reveal our galaxy, but it was just one “island universe” in a much bolder universe. And how many galaxies are there? We got to know at least two with Andromeda. But since then we have learned that there are neither two, nor ten, nor hundreds, nor thousands, nor millions, but it is likely that the TRILIA galaxies are each filled with hundreds of billions of stars. Our own Milky Way is a collection of 100-400 billion stars (we orbit one them). There are more stars in the entire Universe than grains of sand on all the beaches of the earth put together. But how can we know? Well, and since the days Hubble measured a handful of variable stars in one galaxy, Sloan’s digital sky study on July 19th. Released a new map that is the most comprehensive image the Universe has ever taken. It took twenty years and has 4 MILLION marked galaxies in it !!
Each of these dots in the picture is not a star, but a GALAXY filled with stars. Using a specialized telescope in New Mexico, the Sloan Digital Sky Survey created a series of distant galaxy catalogs to create this map of the Universe. The catalogs contain large red (older) galaxies closer to the Milky Way, more distant blue (younger) galaxies, and the most distant are galaxies whose central supermassive blackheads, which we believe are at the core of most galaxies, actively feed on dust. , gas and stars. These feeding blackheads may become the most luminous objects in the Universe, called quasars. The image “fan” shape shows regions where we can only observe dust and gas in our Milky Way galaxy that obscures our view of parts of the Universe.
Hubble made another incredible discovery. Specified as Hubble constant, Hubble realized that all distant galaxies are moving away from us. It was the first proof that our Universe was actually expanding. The expansion itself can be used to measure our distance from these galaxies. SDSS uses a different methodology than the one used to measure the distance to Andromeda. An ordinary candle, like a kefid variable, works in the order of millions of light-years, but we cannot solve individual stars in very distant galaxies. Instead, SDSS measures the red shift of the galaxy. As the light of a distant galaxy travels through space, it travels through an expanding Universe that literally stretches out the light, making it red. How much the red light has shifted by the time it reaches us gives us an idea of how far the light has traveled.
Observing these galaxies also helps track the expansion of the Universe over time, such as showing a movie backwards. The further into the space we are looking at, called the “recurring time”, the further time we see because it takes time for light from the distant Universe to reach us. For example, imagine if I sent you a photo of my photo, but the letter took you twenty years because I was so far away. You see me the way I appeared twenty years ago. Similarly, the SDSS map looks at the time that has elapsed about 400,000 years after the birth of the Universe and how it has expanded over time. Until very recently, a large time span of over 11 billion years existed between the ancient-ancient past and the present (the large gap, given the age of the Universe, is 13.8 billion years). This gap has been filled by the latest SDSS catalog called eBOSS (Extended Baryon Oscillation Spectroscope Study). In addition to having a new map of the Universe, the SDSS fills the pieces with another key question … why and how is the Universe expanding? At present, the “force” that causes the expansion of the Universe is called the mysterious and unknown “Dark Energy.” The new map helps determine if the impact of dark energy has changed over time. Based on SDSS measurements, the rates of expansion of the Universe appear to vary across the history of the Universe, which may be an indication of the action of dark energy. Therefore, SDSS maps allow for possible future discoveries that will lead to a better understanding of dark energy.
And now, a flight through space and time. BEHOLD, the journey of the Universe itself !!
Interview with the SDSS collaboration team https://youtu.be/TKiYOnsE8Y4
Waterloo University Press Release: https://uwaterloo.ca/astrophysics-centre/news/astrophysicists-release-largest-3d-map-universe-ever-created
SDSS press release: https://www.sdss.org/press-releases/no-need-to-mind-the-gap/