As of July 2025, MAST contains nearly 300 million astronomical observations! That’s a lot of data - but what does it look like? We have the answer!

These new wallpaper images depict MAST’s View of the Sky! This is an image using astronomical coordinates Right Ascension (RA) and Declination (Dec), where each pixel is colored according to the number of observations in MAST at those coordinates. Dark pixels have fewer observations, while brighter pixels have several thousand.

Scroll down for the full story.

Downloadable MAST Wallpapers

Here are the MAST Wallpaper images for you to download and use wherever you’d like!

Different Coordinate Projections

Celestial Coordinates (RA, Dec)

Ecliptic Coordinates (lon, lat)

Galactic Coordinates (l, b)

Different Colors

The wallpapers are available in a variety of different colors! Click on the image to download the full-resolution version.

So, What am I looking at?

There’s a lot going on in this image - here’s an annotated version to help decipher what you are looking at!

This is a plot of celestial coordinates Right Ascension (on the x-axis) and Declination (on the y-axis), where each pixel is colored by the number of observations in MAST at that coordinate, randing from 0 (black) to 1,000 (white).

You might notice some features in this image which highlight different telescopes. For example, the bright rectangles (most obvious in the bottom half of this plot) are TESS Sectors. Similarly, the “+” shaped stamps along the ecliptic plane are the characteristic footprint of the Kepler and K2 Missions.

Many of the most-observed areas of the sky correspond to interesting astronomical objects, Such as the U-shaped curve of the Milky Way, our neighbor galaxies the LMC and SMC, or the various star clusters and nebulae in the Messier catalog. Some big programs from HST and JWST show up as really bright spots in this image too. The most obvious ones here are the CANDELS and COSMOS fields, which were two of the largest observing programs done by HST.

But in general, the bright spots peppered around all throughout the image are the locations of many interesting astronomical targets, from nebulaes like the Orion Nebula to galaxies like Andromeda or M81. The brightest points in this image are locations that scientists observe again and again and again, with different telescopes and instruments and at different times - the most interesting parts of the sky!

The winner for the single most observed area in the sky is the GOODS-South Field near the lower-left of the image, a galaxy rich field containing over 7,500 galaxies used to study the formation history of the Universe!

Different Missions

MAST contains data from over 23 different missions, all of which have their own unique footprint on the sky. This figure shows the footprint for 16 different data collections, showing the sky map and number of observations in each.

You’ll see that the coverage of the sky depends highly on which mission you select! HST and JWST have observed lots of scattered points across the whole sky. Compare that to something like Pan-STARRS, which uniformly covered the entire sky north of declination -30 degrees.

The largest collection, by far, is our High-Level Science Products. This is due, in part, due to intense community interest in reprocessing TESS observations.

Evolution of MAST

This animated movie shows how the archive has built up over time, based on the observation date of each observation in MAST:

Starting with the launch of HST in 1990, only small points of the sky were observed and start to build up over time. Around 2000, data from the Sloan Digital Sky Survey (SDSS) comes into play and starts to cover larger areas of the sky. When TESS launched in 2019, the data really explodes. The upcoming launch of the Roman Space Telescope will add over 20,000 terabytes more data to MAST!

How did you make this?

If you want to know more about this visualization of MAST, check out the new Juptyer Notebook Tutorial: MAST’S View of the Sky which shows how it was made!

MAST is like a library - our collections are open to the public and free of cost. For both libraries and MAST, maintaining a detailed catalog that lists everything in the collection is extremely important to help people find what they are looking for. A library might catalog the book title, author’s name, publishing year, and the location on the shelf for every book in its collection. At MAST, we maintain a list of the filenames, the astronomical coordinates, the exposure date, which telescope was used, and so much more, for every single file in the archive. This information is referred to as ‘metadata’ - important information which describes the contents of every file!

At MAST, this metadata catalog is accessible from your web browser using the MAST Portal, in Python using astroquery.MAST, or using the Table Access Protocal (VO-TAP) service. With this MAST metadata catalog, we can retrieve a huge list of astronomical coordinates for every observation in MAST. Using the central coordinates of all observations in our database, we can create this density plot on the sky!

Conclusions and Other Thoughts

It’s pretty dang cool that through metadata alone, we can reconstruct the shape and even texture of the milky way. These images, which are gorgeous, are also a powerful reminder that MAST has a lot of data. And this is a reminder that those data are free for anyone to access, so check them out through our search forms or our astroquery API!

Stay tuned for more!

If you’ve read this far, thanks! Want more visualizations? Stay tuned to the blog! We’ll post anything new here.

Written by: Julie Imig & Thomas Dutkiewicz

MAST

We are the Barbara A. Mikulski Archive for Space Telescopes! Primarily focused on the optical, ultraviolet, and near-infrared, we host data from Hubble, JWST, and over two dozen other missions.