The sky is big. If you want to map it in detail, you also need to think big.
Astronomers are fine with that. A massive international team has just made an aerial survey that is so large that I can hardly comprehend it.
The map is the highlight of six years with 1405 night observations, three telescopes (and one space telescope) and one supercomputer that drags the data away … because the recording has a total of 10 trillion pixels, and form a petabyte data – one thousand terabytes, or one million gigabytes.
Oh, it’s over too a billion galaxies in it. A. Billion.
Like I said: Great.
This is the result of the DESI Legacy Imaging Surveys, maps of the sky made by the three observatories (the Dark Energy Camera Legacy Survey, the Beijing-Arizona Sky Survey, and the Mayall zband Legacy Survey, in combination with the orbit WISE infrared observatory ). They mapped the northern sky in seven colors and covered 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 this by selecting tens of millions of the billion galaxies in the data and obtaining follow-up observations using the Dark Energy Spectroscopic Instrument (DESI), which will take the galaxies into spectra and find their distances.
Since we will know their positions in the sky and their distances, it will make a 3D map of the universe bigger than ever before.
Also as I said: Think big.
The spectroscopic observations will only be made in 2024, but from the observations of the survey there is already an abundance of science.
For example, astronomers – including ‘civil scientists’, just science lovers who do not necessarily have formal scientific training – selected the data in search of brown dwarfs, objects between the masses between planets and stars, and 525 of them found about 65 light-years from the sun in the recordings, 38 of which have never been seen before. Combined with data from the Spitzer Space Telescope, they were able to reach distances, making it the best 3D map of brown dwarfs to date.
Because the recording includes infrared light, it is sensitive to hot objects such as brown dwarfs, and they think that these brown dwarfs should be closer to 65 light-years warmer than about 330 ° C (620 ° F). They’re getting cooler than that – a few years ago some brown dwarfs were found that are actually room temperature, and there might be even cooler outside – so it’s possible that a lot more could be detected. This is an excellent start after all! Brown dwarfs are faint (the first was only discovered in the nineties) and hard to find.
These kinds of things are important because we know that stars form when clouds of gas and dust collapse, but when they do, stars of all masses are born. Massive stars are bright, so it is easy to see, but at their low mass the stars are faint. However, there are many more than stars with a high mass, so to get a census of objects, we need to better understand the dim end of the spectrum. This survey will help.
Another group of astronomers looked at distant objects: individual galaxies as well as galaxies, to find gravity lenses. When the light of a stellar galaxy moves near a galaxy or cluster en route to Earth, the gravitational force of the intervening object bends the path of light like a lens, creating distorted images of the background system. The light can also be quite amplified, which makes fainter objects appear brighter.
This phenomenon makes it possible to observe dim, distant galaxies and see what is going on in them. It also tells us about the distribution of mass and dark matter in the galaxies and galaxies, so it is a two-way street.
The group applied machine learning to the DESI data, and learned an algorithm on how to find gravity lenses in the observations … and how I did it. More than 1,200 new lenses have been found, doubling the number known so far! I will notice that it is technical candidate lenses, which need to be confirmed, but they have visually inspected it, so I am confident that the majority of it is real.
It’s really just a taste of what’s possible. Huge surveys like these are treasuries, just huge piles of data waiting for scientists to dive in and use it for all the research they do. This is the beauty of them. This is generalized, so if you study brown dwarfs or gravity lenses or bright stars or dwarf systems or galaxies, whatever, then there is probably something useful in the survey.
You can also take a look at the interactive viewer that the team has created. It’s pretty intuitive; you can scroll in and out, move around or search for your favorite object … provided the recording covers that part of the sky. There is also a chat room where you can (if you register) point out interesting objects and discuss them with others. Maybe you will discover something!
Have fun. With over a billion objects in the database, it should all keep busy for a long, long time.