Better late than never. Like Rip van Winkle awakening from a long slumber, the dwarf galaxies have now ended their star-making drought and have joined the party. Astronomers estimate that less than 100 million years ago the galaxies doubled their star-formation rate. For most of the universe's history these puny galaxies dwelled in the Local Void, a region of the universe sparsely populated with galaxies. Now the galaxies have moved into a region crowded with galaxies and full of intergalactic gas. This dense environment is triggering star birth.
The artist's impression shows a view of the HD 131399 system from the perspective of the giant planet, HD 131399Ab (lower left), orbiting in the system. The planet is about 16 million years old, making it one of the youngest exoplanets discovered to date – and one of just a handful of “directly imaged” planets. It is also one of the coldest and least massive exoplanets that have been directly imaged.
Tom Brown, Space Telescope Science Institute
In the past decade, wide-field surveys have revealed a new class of ultra-faint dwarf galaxies orbiting the Milky Way and Andromeda. They are the least luminous, most dark-matter dominated, and least chemically-evolved galaxies known. These faint galaxies offer a new front in efforts to understand the missing satellite problem - the discrepancy that theory predicts many more satellite galaxies than the number of dwarf galaxies observed. As the best candidates for fossils from the early universe, the ultra-faint dwarfs are ideal places to test the physics of galaxy formation from that era. New data from the Keck Observatory and the Hubble Space Telescope provide evidence that reionization in the early universe suppressed star formation in the smallest seeds of galaxy formation, thus providing a possible explanation for the missing satellite problem.
Host: Dr. Frank Summers
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Now, astronomers have used Hubble to conduct the first search for atmospheres around temperate, Earth-sized planets beyond our solar system, uncovering clues that increase the chances of habitability on two exoplanets. They discovered that the exoplanets TRAPPIST-1b and TRAPPIST-1c, approximately 40 light-years away, are unlikely to have puffy, hydrogen-dominated atmospheres usually found on gaseous worlds. Those dense atmospheres act like a greenhouse, smothering any potential life. Observations from NASA's upcoming James Webb Space Telescope will help determine the full composition of these atmospheres and hunt for potential biosignatures, such as carbon dioxide and ozone, and methane.
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Nearly 400 years after Galileo first observed the heavens through a telescope, we continue to seek answers to age-old questions about the universe. And while the technology has evolved over the centuries, the inquiry remains essentially the same: What's out there, where did it come from, and what does it mean?
At the Space Telescope Science Institute (STScI), we're working hard to study and explain the once-unimaginable celestial phenomena now made visible by the Hubble Space Telescope's cutting-edge technology.
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