The sky is big. If you want to map it in detail, you have to think about the sea.
Astronomers are good at this. A massive international team has just launched a sky poll that is so big that it’s hard for me to understand.
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 trillion pixels and make up a petabyte data – a thousand terabytes or a million gigabytes.
Oh, it’s over one billion galaxies in her. One billion.
As I said: Vast.
It is the result of DESI Legacy Imaging Surveys, sky maps made by the three observatories (Dark Energy Camera Legacy Survey, Beijing-Arizona Sky Survey and Mayall zband Legacy Survey, in combination with the WISE orbiting infrared observatory). 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 analyzing the distribution of galaxies throughout the Universe. They will do this by selecting tens of billions of galaxies in data and obtaining subsequent observations with the Dark Energy Spectroscopic Instrument (DESI), which will take the spectra of those galaxies and find their distances.
Because we will know their positions in the sky and their distances, this will make a 3D map of the Universe bigger than ever.
Also, as I said: Think big.
Spectroscopic observations will not be made until 2024, but from the survey’s observations there has already been an orderly scientific reward.
For example, astronomers – including “citizen scientists”, only science-loving people who do not necessarily have a formal scientific background – have chosen to search for brown dwarfs, intermediate objects in mass between planets and stars, and found 525 of them in about 65 light-years of the Sun in surveys, 38 of which had never been seen before. Combined with data from the Spitzer Space Telescope, they managed to get distances, making it the best 3D map of brown dwarfs to date.
Because the survey includes infrared light, it is sensitive to hot objects, such as brown dwarfs, and I think this survey should see any brown dwarf closer to 65 light-years, which is warmer than about 330 ° Celsius (620 ° F). They get colder than that – in fact, a few brown dwarfs were found a few years ago, which are actually room temperature and may be even colder there – so there may still be many detected. However, this is a great start! Brown dwarfs are weak (the first were not even discovered until the 1990s) and are hard to find.
This is important because we know that stars form when clouds of gas and dust collapse, but when this happens, stars of all different masses are born. The massive stars are bright, so they are easy to see, but at the low table end the stars are faint. However, more of them are created than high-mass stars, so in order to get a census of objects we need to better understand that weak end of the spectrum. This survey will help you.
Another group of astronomers looked at more distant objects: individual galaxies, as well as groups of galaxies, 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 background galaxy. The light can also be amplified quite a bit, making weaker objects appear brighter.
This phenomenon makes it possible to observe faint, distant galaxies and see what is happening in them. It also tells us about the distribution of mass and dark matter in the galaxy and in groups of galaxies, so it is a twofer.
The group applied machine learning to DESI data, learning an algorithm on how to find gravitational lenses in observations … and hoo my, it did. He found over 1,200 new targets, doubling the number known until then! I will notice that I am technical candidate lenses, which need to be confirmed, but inspected them visually, so I’m confident that most of them are real.
This is really just a taste of what is possible. Huge polls like this are treasures, just huge piles of data waiting for scientists to sink and use them for whatever research they do. That’s their beauty. They are generalized, so if you study brown dwarfs or gravitational lenses or bright stars or dwarf galaxies or galaxy collisions, whatever it is, it will probably be something useful in the survey.
You can also watch the interactive viewer created by the team. It’s pretty intuitive; you can scroll in and out, move, or search for your favorite object … provided the survey covers that part of the sky. There is also a chat room where (if you register) you can point out interesting items and chat with others. Maybe you’ll find something!
To have fun. With over a billion items in the database, this should keep everyone busy for a long time.