π Mensae c (HD 39091 c) illustration
APRIL 4, 2019

Empowering Astronomical Researchers

Our archive team prepares data releases and creates software to further astronomical research worldwide.


Envision a planet about 60 light-years away. It whips around its Sun-like star in under seven days. It may be filled with layers of water—or made mostly of hydrogen and helium—but isn’t rocky like Earth. In fact, astronomers don’t yet know what makes up the planet’s composition. And, despite the alluring possibility of molecular water, it doesn’t lie within the habitable zone, where liquid water can exist on the planet’s surface.

Meet π Mensae c (HD 39091 c), an exoplanet identified by researchers using data from NASA’s Transiting Exoplanet Survey Satellite (TESS), which launched in April 2018 and sends its data to our staff at the Barbara A. Mikulski Archive for Space Telescopes (MAST). Although we may not know the precise makeup of this planet’s surface, observations from TESS, combined with radial velocity data from observatories in Australia and Chile, allowed researchers to determine its mass and estimate its density, which is roughly 4.82 Earth masses and 57 percent of Earth’s average density.

What the astronomers did in this case—revisit older data sets to review and confirm new findings—isn’t unusual. In fact, it’s one of the primary reasons MAST exists. Teams at the institute also build and share data analysis software, upload fully processed images and spectra that are ready for scientific analysis, and support the exchange of data between institutions.

Best of all? Astronomers and scientists who use MAST’s resources are constantly contributing to its holdings. Once researchers process data, they often return the improved information to MAST, where it is shared widely. Don’t think of the archive as a quiet library, but instead as a bustling hive of activity.

Passing the Baton

In 2018, astronomers, scientists, and engineers within MAST offered a slew of new products to help researchers analyze data more accurately and quickly. Several of these initiatives focused on the milestones of two NASA missions: TESS and the Kepler/K2 spacecraft, which was decommissioned in November 2018. (During the overlap, the pair simultaneously observed more than 100 of the same stars.) Since MAST holds the data for both observatories, our team strove to highlight the synergies between these two missions.

One tool astronomers use to identify exoplanets is a light curve, a plot that shows the changes in a star’s light over time. These plots are extremely important data sets for Kepler and K2 data, but those for K2 were less constraining since the number of reaction wheels the observatory used to point its instruments were reduced from four to two, affecting its ability to point precisely for extended periods.

This year, astronomers reprocessed K2’s data to understand the noise, characterize it, and make it easier to pinpoint exoplanet candidates by releasing K2SFF, a database of extracted light curves and diagnostic plots for each target the Kepler/K2 observatory observed in its extended mission phase, which was developed by external researchers. This database has been incorporated into MAST and is available for use by all. As a result, researchers will be able to identify more potential exoplanet candidates in K2 data.

The MAST team also began hosting EVEREST, a tool created by astronomers elsewhere that contains corrected light curves for K2 data that have precision comparable to the original Kepler mission and allows researchers to toggle the plots based on known exoplanet candidates. Since it’s open source, researchers may adapt the software to use it with other photometric surveys, making the resource even more valuable to the astronomical community.

Releasing New TESS Data

The Kepler/K2 mission discovered that exoplanets orbit nearly every star in the sky, and that about 20 percent of those are similar to Earth in size and orbit. It is easy to imagine why astronomers are excited about comparing this data with that from NASA’s newest planet hunter, TESS.

The first TESS data release covers one-twelfth of the sky, and includes over 400,000 transit light curves and 200,000 full-frame images. Plus, the data were available to all researchers immediately upon their storage in MAST, which means more scientists began working with them at the outset. Within the first few weeks after the release, researchers across the world had retrieved more than 70 terabytes of TESS data, marking the fastest outflow of data from MAST to the community to date.

The data science team simultaneously released a suite of products to support TESS data, allowing queries to be performed programmatically by community-written open source tools such as eleanor and lightkurve, examined within the context of exoplanets identified by other missions, searched within full-frame images, or downloaded in bulk. Plus, every tool is supported by an in-depth tutorial.

Supporting Future Missions

Want to know if a particular exoplanet is a water world? A gas giant? A rocky planet devoid of an atmosphere? Cue the Exoplanet Characterization Toolkit (ExoCTK), built with significant help from scientists located around the world to assist astronomers model the atmospheres of planets and understand what a planet may look like with NASA’s James Webb Space Telescope.

The archive team is constantly working with the astronomical community to connect data from more than 20 missions in new ways, which includes thinking about how to characterize an exoplanet with upcoming missions like Webb, and accelerating the pace at which astronomers go from receiving their initial observations to completing their analyses.

As demonstrated by these examples, all the work the archive team completes supports scientific discovery by streamlining and strengthening researchers’ work, allowing them to produce new results and create new areas of research rapidly, which may lead to discoveries of nearby Earthlike exoplanets sooner than expected.

Surprising Skies: Super-Earths and Hot-Jupiters

Increasingly, researchers have made discoveries about known exoplanets by combining data from multiple missions. Are they terrestrial planets, water worlds, or gas giants? Do they have cloudy or clear skies? Are their surfaces within the temperature ranges conducive to supporting life? In 2018, our staff collaborated with astronomers around the world to create two new products, Exo.MAST and ExoCTK, to allow researchers to review, visualize, download, and analyze multi-mission exoplanet data, making this process faster and simpler. What do the data hold? Here, we highlight samples both close to Earth and light-years away.


TRAPPIST-1 d illustration
39 light-years away 

This planet may have a large atmosphere, a deep worldwide ocean, or an ice layer, each composed of less dense, more fragile substances that don’t survive long close to a star. 

GALEX, Hubble, Webb, Pan-STARRS1, Swift
Proxima Centauri b illustration
Proxima Centauri b
4 light-years away 

This notable discovery of a planet around a nearby star means our solar neighborhood may be teeming with planets. Although it orbits much closer to its star than Mercury does to the Sun, the star is far fainter, which means this planet lies within the habitable zone where liquid water may be possible. 

EUVE, FUSE, GALEX, Hubble, IUE, Swift
Kepler-186 f illustration
Kepler-186 f
492 light-years away 

Discovered in 2014, this planet was the first Earth-sized exoplanet found to reside firmly in its star’s habitable zone. Despite being much closer to its star, it receives only one third of the energy Earth does from the Sun. This is because its star is much smaller and cooler. 

Kepler/K2, Pan-STARRS1


51 Pegasi b illustration
51 Pegasi b
51 light-years away 

This giant planet is about half the size of Jupiter and orbits its star in about four days. One side of the planet always faces the star; the other is in permanent darkness. 

TrES-2 b illustration
TrES-2 b
694 light-years away 

This gas giant reflects less than 1 percent of the sunlight falling on it, making it blacker than coal. It is also believed to be tidally locked, with one side of the planet always facing its star. 

Hubble, Kepler, Pan-STARRS1
π Mensae c illustration
π Mensae c
60 light-years away

This is TESS’s first confirmed exoplanet discovery: A world about twice Earth’s size that orbits its star every six days. 

GALEX, Hubble, Swift, TESS


MAST includes data from more than 20 telescopes.

Those highlighted include: Extreme Ultraviolet Explorer (EUVE) • Far Ultraviolet Spectroscopic Explorer (FUSE) • Galaxy Evolution Explorer (GALEX) • Hubble Space Telescope • International Ultraviolet Explorer (IUE) • James Webb Space Telescope (planned observation) • Kepler/K2 mission • Pan-STARRS1 • Neil Gehrels Swift Observatory (Swift) • Transiting Exoplanet Survey Satellite (TESS)