Finding common table salt — sodium chloride — on the surface of a moon is more than just a scientific curiosity when that moon is Europa, a potential abode of life.

If the salt came from the briny subsurface ocean of Europa, a satellite of Jupiter, that ocean may chemically resemble Earth's oceans more than previously thought. Because Europa's solid, icy crust is geologically young it has been suspected that whatever salts exist on the surface may come from the ocean below, which might host microorganisms.

Using visible-light spectral analysis, planetary scientists at Caltech and NASA's Jet... Read more

In order to grow to Jupiter size or larger, a gas giant planet must slurp large quantities of hydrogen and other gases from the disk in which it forms. Astronomers have looked for evidence of this process, but direct observations are challenging because planets become lost in the glare of their star. A team has succeeded in making ground-based observations of two planets accreting matter from a disk. It represents only the second multi-planet system to be directly imaged.

One doesn't need a Ph.D. in astrophysics to recognize there is something odd-looking about this otherwise beautiful galaxy, NCG 4485. Like the Batman character Two-Face, one side looks normal, but the other side looks contorted with a firestorm of star formation going on. Why the colorful asymmetry in an island star city many thousands of light-years across? The clue is off the edge of the photo. It's another galaxy, NGC 4490, that swept by NGC 4485 millions of years ago. The gravitational taffy pull between the two galaxies compressed interstellar gas to trigger a flurry of new star birth as seen in... Read more

How far is far? And, how do you know when you get there? In 1995, astronomers decided to use the Hubble Space Telescope to conduct a bold and daring experiment to address this puzzle. For 10 consecutive days, Hubble stared at one tiny, seemingly empty patch of sky for 1 million seconds.

The gamble of precious telescope time paid off. Hubble captured the feeble glow of myriad never-before-seen galaxies. Many of the galaxies are so far away it has taken billions of years for their light to reach us. Therefore, the view is like looking down a "time corridor," where galaxies can be seen as they looked... Read more

There is something wrong with our universe. Or, more specifically, it is outpacing all expectations for its present rate of expansion.

Something is amiss in astronomers' efforts to measure the past and predict the present, according to a discrepancy between the two main techniques for measuring the universe's expansion rate – a key to understanding its history and physical parameters.

The inconsistency is between the Hubble Space Telescope measurements of today's expansion rate of the universe (by looking at stellar milepost markers) and the expansion rate as measured by the European Space... Read more

This Hubble image shows the results of two stellar companions in a gravitational waltz, several thousand light-years from Earth in the southern constellation Centaurus. The stellar duo, consisting of a red giant and white dwarf, are too close together to see individually in this view. But the consequences of their whirling about each other are two vast shells of gas expanding into space like a runaway hot air balloon. Both stars are embedded in a flat disk of hot material that constricts the outflowing gas so that it only escapes away above and below the stars. This apparently happens in episodes... Read more

NASA has selected 24 new Fellows for its prestigious NASA Hubble Fellowship Program (NHFP). The program enables outstanding postdoctoral scientists to pursue independent research in any area of NASA Astrophysics, using theory, observation, experimentation, or instrument development. Each fellowship provides the awardee up to three years of support.

Astronomers once thought asteroids were boring, wayward space rocks that simply orbit around the Sun. These objects were dramatically presented only in science fiction movies.

But recent observations show that asteroids are anything but dull. In reality they are dynamic, active worlds that can ultimately disintegrate due to the long-term subtle effects of sunlight, which can slowly spin them up until they begin to shed material.

Several telescopes, including NASA's Hubble Space Telescope, have caught the gradual self-destruction of the asteroid (6478) Gault. Images from Hubble show two... Read more

We live in a gigantic star city. Our Milky Way galaxy contains an estimated 200 billion stars. But that's just the bare tip of the iceberg. The Milky Way is surrounded by vast amounts of an unknown material called dark matter that is invisible because it doesn't release any radiation. Astronomers know it exists because, dynamically, the galaxy would fly apart if dark matter didn't keep a gravitational lid on things.

Still, astronomers would like to have a precise measure of the galaxy's mass to better understand how the myriad galaxies throughout the universe form and evolve. Other galaxies can... Read more

NASA has recovered the Hubble Space Telescope's Advanced Camera for Surveys instrument, which suspended operations on Thursday, Feb. 28, 2019. The final tests were conducted and the instrument was brought back to its operational mode on March 6.