Scorching "Hot Jupiter" Has a Stratospheric Layer

Only when we fly in a commercial jet at an altitude of about 33,000 feet do we enter Earth's stratosphere, a cloudless layer of our atmosphere that blocks ultraviolet light. Astronomers were fascinated to find evidence for a stratosphere on a planet orbiting another star. As on Earth, the planet's stratosphere is a layer where temperatures increase with higher altitudes, rather than decrease. However, the planet (WASP-121b) is anything but Earth-like. The Jupiter-sized planet is so close to its parent star that the top of the... Read more

The Tiny Moon Phobos Is Photographed During Its Quick Trip Around Mars

While photographing Mars, NASA’s Hubble Space Telescope captured a cameo appearance of the tiny moon Phobos on its trek around the Red Planet. Discovered in 1877, the diminutive, potato-shaped moon is so small that it appears star-like in the Hubble pictures. Phobos orbits Mars in just 7 hours and 39 minutes, which is faster than Mars rotates. The moon’s orbit is very slowly shrinking, meaning it will eventually shatter under Mars’ gravitational pull, or crash into the planet. Hubble took 13 separate exposures... Read more

Gravitational lens helps reveal "fireworks" in the early universe

When the universe was young, stars formed at a much higher rate than they do today. By peering across billions of light-years of space, Hubble can study this early era. But at such distances, galaxies shrink to smudges that hide key details. Astronomers have teased out those details in one distant galaxy by combining Hubble’s sharp vision with the natural magnifying power of a gravitational lens. The result is an image 10 times better than what Hubble could achieve on its own, showing dense clusters of brilliant, young stars that resemble cosmic fireworks.

Young, Dead, Compact, Disk Galaxy Surprises Astronomers, Offers New Clues to How Modern-Day Elliptical Galaxies Formed

Astronomers combined the power of a “natural lens” in space with the capability of NASA’s Hubble Space Telescope to make a surprising discovery—the first example of a compact yet massive, fast-spinning, disk-shaped galaxy that stopped making stars only a few billion years after the big bang. Researchers say that finding such a galaxy so early in the history of the universe challenges the current understanding of how massive galaxies form and evolve. Astronomers... Read more

Webb Telescope Guaranteed Time Observations Targets Announced

Mission officials for NASA’s James Webb Space Telescope announced some of the science targets the telescope will observe following its launch and commissioning. These specific observations are part of a program of Guaranteed Time Observations (GTO), which provides dedicated time to the scientists that helped design and build the telescope’s four instruments. The broad spectrum of initial GTO observations will address all of the science areas Webb is designed to explore, from first light and the assembly of galaxies to... Read more

White dwarf shows how gravity can bend starlight

Albert Einstein reshaped our understanding of the fabric of space. In his general theory of relativity in 1915, he proposed the revolutionary idea that massive objects warp space, due to the effects of gravity. Until that time, Isaac Newton's theory of gravity from two centuries earlier held sway: that space was unchanging. Einstein's theory was experimentally verified four years later when a team led by British astronomer Sir Arthur Eddington measured how much the sun's gravity deflected the image of a background star as its light... Read more

Galaxies Shine with the Brilliance of up to 100 Trillion Suns

Astronomers were fascinated in the 1980s with the discovery of nearby dust-enshrouded galaxies that glowed thousands of times brighter than our Milky Way galaxy in infrared light. Dubbed ultra-luminous infrared galaxies, they were star-making factories, churning out a prodigious amount of stars every year. What wasn't initially clear was what powered these giant infrared light bulbs. Observations by the Hubble Space Telescope helped astronomers confirm the source of the galaxies' light output. Many of them reside within... Read more

Solar flares and associated eruptions can trigger auroras on Earth or, more ominously, damage satellites and power grids. Could flares on cool, red dwarf stars cause even more havoc to orbiting planets, even rendering them uninhabitable? To help answer that question, astronomers sought to find out how many flares such stars typically unleash.

A new study of archival ultraviolet observations from the Galaxy Evolution Explorer (GALEX) spacecraft detected dozens of flares from red dwarf stars. Some flares were weaker than any previously detected. Since smaller flares tend to occur more frequently,... Read more

Atmospheres of Two Hot Jupiters: Cloudy and Clear

Astronomers once thought that the family of planets that orbit our sun were typical of what would eventually be found around other stars: a grouping of small rocky planets like Earth huddled close to their parent star, and an outer family of monstrous gaseous planets like Jupiter and Saturn.

But ever since the discovery of the first planet around another star (or exoplanet) the universe looks a bit more complicated — if not downright capricious. There is an entire class of exoplanets called "hot Jupiters." They formed like... Read more

Massive Dying Star Goes Out With a Whimper Instead of a Bang

Every second a star somewhere out in the universe explodes as a supernova. But some super-massive stars go out with a whimper instead of a bang. When they do, they can collapse under the crushing tug of gravity and vanish out of sight, only to leave behind a black hole. The doomed star, named N6946-BH1, was 25 times as massive as our sun. It began to brighten weakly in 2009. But, by 2015, it appeared to have winked out of existence. By a careful process of elimination, based on observations by the Large Binocular... Read more