From 2MASS To You… The Most Complete 3-D Map of Local Universe


Isn’t this era of astronomy incredible? There are times when I thumb through my old astronomy books with their outdated information and simply marvel over today’s capabilities. Who would have believed just 50 years ago that we’d be peering into the far reaches of our Universe – let alone mapping them? Thanks to an endeavor that took more than 10 years to complete, the 2MASS Redshift Survey (2MRS) has provided us with 3-D map which cuts through the dust and pushes the envelope of the Galactic Plane out to 380 million light-years – encompassing more than 500 million stars and resolving more than 1.5 million galaxies.

With our current understanding of expansion, we accept a distant galaxy’s light is stretched into longer wavelengths – or redshifted. By default, this means the further a galaxy is away, the greater the redshift will be. This then becomes a critical factor in producing a three-dimensional point in mapping. To cut through the layers of obscuring dust, the original Two-Micron All-SkySurvey (2MASS) visualized the entire visible sky in three near-infrared wavelength bands. While it gave us an incredible look at what’s out there, it lacked a critical factor… distance. Fortunately, some of the galaxies logged by 2MASS had known redshifts, and thus began the intense “homework” of measurements in the late 1990s using mainly two telescopes: one at the Fred Lawrence Whipple Observatory on Mt. Hopkins, AZ, and one at the Cerro Tololo Inter-American Observatory in Chile.

“Our understanding of the origin and evolution of the Universe has been fundamentally transformed with seminal redshift, distant supernovae and cosmic microwave background surveys. The focus has shifted to the distribution and nature of dark matter and dark energy that drive the dynamics of the expanding cosmos.” says team member, Thomas Jarrett. “The study of the local Universe, including its peculiar motions and its clustering on scales exceeding 100 Mpc, is an essential ingredient in the connection between the origin of structure in the early Universe and the subsequent formation of galaxies and their evolution to the state we observe today. Key issues include the location and velocity distribution of galaxies, leading to the mass-to-light relationship between what is observed and what is influencing the mass density field.”

What makes this work so impressive? The 2MRS has logged what’s been previously hidden behind our Milky Way – allowing us to comprehend the impact they have on our motion. From the time astronomers first measured our movement relative to the rest of the Universe and realized it couldn’t be explained by the gravitational attraction from any visible matter, it became a huge jigsaw puzzle just waiting to have the pieces match up. Now massive local structures, like the Hydra-Centaurus region (the “Great Attractor”) which were previously hidden almost behind the Milky Way are shown in great detail by 2MRS. The Galactic “zone of avoidance” (ZoA) is still, however, a formidable barrier due to the sheer number of stars that produce a foreground (confusion) “noise”. Near the center of the Milky Way the confusion noise is extreme, blocking nearly 100% of the background light; whereas far from the Galactic center the confusion noise is minimal and the veil of the Milky Way is lifted at near-infrared wavelengths

“The 2MASS catalog has proven to be quite versatile to the astronomical community: supporting observation and future mission planning, seeding studies of star formation and morphology in nearby galaxies, penetrating the zone of avoidance, providing the base catalog of redshift and Tully-Fisher HI surveys, and so on. But perhaps its most important function is to provide the “big picture” context for analysis and interpretation of data concerning galaxy clusters, large scale structure and the density of matter in the Universe.” says Jarrett. “And so the primary motivation of this work, with the construction of qualitative “road” maps to the local Universe, is to provide a broad framework for studying the physical connection between the local Universe (Milky Way, Local Group, Local Supercluster, “Great Wall”, etc) and the distant Universe where galaxies and the cosmic web first formed. The best is yet to come.”

28 Replies to “From 2MASS To You… The Most Complete 3-D Map of Local Universe”

    1. You’ve GOT to be kidding… The level of “English” used on that site is rivaled by emails from expat princes looking for a bank account in which to deposit their fortunes… IE: How can it possibly be taken seriously?

      1. that’s a great site and 100% true. all you have to do is read this quote, which puts the entire 150 million km universe into perspective:

        “Since we are created from earth, the power of our eyes has merged with the earth and since the earthlike object disappears at a distance of 150 million Kilometers, the eyes power can not see anything ahead of it. Here starts the game of reflection.”

        PURE GENIUS.

      2. that’s a great site and 100% true. all you have to do is read this quote, which puts the entire 150 million km universe into perspective:

        “Since we are created from earth, the power of our eyes has merged with the earth and since the earthlike object disappears at a distance of 150 million Kilometers, the eyes power can not see anything ahead of it. Here starts the game of reflection.”

        PURE GENIUS.

      3. Genius does not even begin to describe it really. I am certainly astounded.

      4. Tammy, it’s your article that Pradipta is spamming, so why don’t you disable the link to his asinine website?

      5. @Efreet

        You are being sarcastic, I hope — you comment ‘the site is pure genius” is in upper case after all. You, like myself, should find the site to be very disturbing, in fact I hope you find the site you gush over as idiotic as I do rather than idyllic as you words seemingly suggest. Pure rubbish is my findings, please tell me you are not serious in your respect for that site, please.


      6. Don’t be so chauvinist Jeffrey. Correct use of English is not a pre-requisite for scientific excellence. Yes, the site is full of crap, but the quality of the English is not necessarily a measure of the science.

    2. That’s funny; our deep space probes did not crash into any barrier (mirror) on their way to the outer planets.

      Why do people want to believe in things that are so utterly wrong?


      1. To answer your question, it is probably for the same reason that, thirty-odd years ago, you could have travelled thousands of miles throughout the United States and never seen a baseball cap turned back to front; whereas today, the reverse baseball cap is ubiquitous.

      2. They are all forwards, you’re just looking through an invisible cap-reversing mirror.

      3. LC, go ahead and flag silly stuff when you read it. UT staff have made me a moderator. Flagged comments will be sent to my mail.

      4. i see my comment was also removed, although other poster’s sarcastic replies were allowed to stay. good work fred. nice unbiased admin work.why the heck would they make you a moderator? you have picked fights with posters in the past under the old system.

        it’s a sign to me that it’s time to go. thanks tammy, nancy, and mr.nerlich. i’ve really enjoyed your work. dark gnat, astrofiend, mr.crowell (and others), thanks for the lessons over the years.

    3. I thought this sort of free advertising for pet theories (i.e. spam) was to be deleted upon sight here; what went wrong?

      1. Lots of comments per hour and a lot of news articles. It’s hard to keep up.

        If you see a comment that violates UT policy, you can flag it and I will catch it faster.

    4. awesome, so the outer planets of the solar system are at 10 km from each other? and jupiter is twice the earth muahahahahah xd, and the reptilians rule the earth?

  1. All I want for Christmas is the raw dataset, the time to explore it in R, and a decent computer to do it on.

  2. So at ~ 0.4 Gly it is ~ 1/200 of the ~ 90 Gly radius of the observable universe, or ~ 10^-4 of the volume.

    That is neat, with better methods we could do the remaining volume in much less than 10^5 years. “The Universe in 3D – now in a browser near you.”

  3. So redshift was used to determine relative distance. However, was the relative motion of the visible objects combined with the relative distance to adjust objects to their actual relative positions or is this still a map of objects as seen from Earth? If the latter, it can be a useful guide for stargazing. However, viewing the universe as it appears from Earth does not strike me as being terribly useful in studying the large-scale structure of the universe and the consequent distribution of mass unless relative positions are corrected for distance and the differences in age of the light used in producing this map.

    1. I would imagine it is indeed the latter. Hopefully someone will take on the task of trying to correct for the time factor, although it would be a pretty daunting undertaking. Even still, just correcting for position of areas as a whole would be informative.

      1. Yes, it would be very daunting. In fact, even a first approximation is almost certainly impossible without regularly repeating this survey over decades–or even centuries–to assemble sufficient data to make the kinds of adjustments necessary for the interpolations that would enable us to visualize the universe as it is rather than as it appears.

        It is an interesting problem of cosmology that all interpretations of the evolution of the universe must come by necessity from an understanding of atomic and sub-atomic physics as well as very narrow-field observations of large, distant objects. Wide-field observations are of little value in identifying actual structure. Instead, there is a real risk that a researcher will be mislead by patterns in the observed projection of the cosmos we see.

        What we see is not reality, but a time distorted projection of what was at different times and places. Of course, everyone familiar with relativity, redshift, and the constant speed of light is aware of this, but even they are unlikely to give much thought to those considerations when simply examining a star map, no matter how detailed or meticulously assembled from comprehensive sky surveys.

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