The sky is great. If you want to map it in detail, you also have to think big.
Astronomers are good at this. A huge international team has just published a sky survey so huge that it’s hard for me to catch it.
The map is the culmination of six years with 1405 nights of observations, three telescopes (and a space telescope) and a supercomputer moving away from the data … because the survey has a total of 10 billions pixels and constitutes a file petabyte of data: one thousand terabytes or one million gigabytes.
Oh, it’s over too billion galaxies in it. A. Billions.
Like I said: Vast.
It is the result of DESI Legacy Imaging Surveys, maps of the sky made by the three observatories (Dark Energy Camera Legacy Survey, Beijing-Arizona Sky Survey and Mayall zband Legacy Survey, in combination with the orbiting infrared observatory WISE). . They mapped the northern sky in seven colors, covering a third of the entire sky: 14,000 square degrees, or the equivalent area of 70,000 full moons in the sky.
The ultimate goal is to better understand dark energy, the mysterious substance that accelerates the expansion of the Universe, by looking at the distribution of galaxies throughout the Universe. They will do so by collecting tens of billions of galaxies in the data and obtaining follow-up observations with the Dark Energy Spectroscopic Instrument (DESI), which will take spectra from these galaxies and find their distances.
Because we will know their positions on the sky and their distances, this will make a map of the 3D Universe bigger than ever.
Also as I said: Think great.
Spectroscopic observations will not be made until 2024, but there has already been a science reward from the survey’s observations.
For example, astronomers, including “citizen scientists,” only science-loving people who do not necessarily have formal scientific training, collected data in search of brown dwarfs, mass-mediated objects between planets and stars, and in vain. found 525 about 65 light-years from the Sun in surveys, 38 of which had never been seen before. Combined with data from the Spitzer Space Telescope, they were able to obtain distances, making it the best 3D map of brown dwarfs to date.
Because the survey includes infrared light, it is sensitive to warm objects such as brown dwarfs, and they think that this survey should see any brown dwarf less than 65 light-years higher than about 330 ° C (620 ° F). They get cooler than that, in fact, a few years ago some brown dwarfs were found that really have room temperature, and there may be even cooler ones, so there may be many more. to detect. Still, this is a great start. Brown dwarfs are weak (the first ones were not even discovered until the 1990s) and are hard to find.
These kinds of things are important because we know that stars form when clouds of gas and dust sink, but when that happens stars of all different masses are born. Massive stars are bright, so they are easy to see, but at the low-mass end the stars are faint. However, much more is created than high-mass stars, so to get a census of objects we need to better understand that faint end of the spectrum. This survey will help you.
Another group of astronomers looked at much more distant objects: individual galaxies and clusters of galaxies, in order to find gravitational lenses. When light from an even more distant galaxy passes near a galaxy or cluster on its way to Earth, the gravity of the intervening object bends the path of light like a lens, creating distorted images of the Earth. background galaxy. Light can also be amplified a lot, which makes weaker objects appear brighter.
This phenomenon allows us to observe weak and distant galaxies and see what happens there. It also tells us about the distribution of mass and dark matter in the galaxy and galaxy clusters, so it’s a twofer.
The group applied machine learning to DESI data, teaching an algorithm how to find gravitational lenses in observations … and hoo, it did. He found more than 1,200 new targets, doubling the number known until then. I note that technically they are candidate lenses, which needs to be confirmed, but they were inspected visually, so I’m sure most are real.
This is really just a taste of what is possible. Huge surveys like this are treasures, just huge stacks of data waiting for scientists to go in and use them for whatever research they do. This is the beauty of them. They become widespread, so if you’re studying brown dwarfs or gravitational lenses or bright stars or dwarf galaxies or galaxy collisions, whatever it is, there’s probably something useful in the survey.
You can also take a look at the interactive viewer your computer has created. It’s pretty intuitive; you can move in and out, move around, or look for your favorite object … as long as the survey has covered that part of the sky. There is also a chat room where (if you register) you can point out interesting items and discuss them with other people. Maybe you will discover something!
Have fun. With over a billion objects in the database, this should occupy everyone for a long time.