Dwarf Galaxies Produce More Than Their Fair Share Of Stars

They might be small, but that doesn't stop dwarf galaxies from cooking up a lot of stars. According to new Hubble observations, dwarf galaxies are responsible for forming a large proportion of the universe’s stars.
The early universe, between 2 and 6 billion years after the Big Bang, was an important time when most stars were formed. For the last decade, astronomers have been looking for a link between a galaxy’s mass and its star-forming activity, but previous studies of stellar births during this epoch were limited to mid- or high-mass galaxies -- leaving low-mass dwarf galaxies out of this formative era of prolific star formation.
"We already suspected these kinds of galaxies would contribute to the early wave of star formation, but this is the first time we've been able to measure the effect they actually had," says Hakim Atek of the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland. “They appear to have had a surprisingly huge role to play."
Using the infrared capabilities of Hubble’s Wide Field Camera 3 (WF3), Atek and colleagues were able to examine a sample of “starburst galaxies” in the young universe. Starburst galaxies are ones that churn out stars at a crazy fast rate -- far above normal expectations. With these observations, the team was able to calculate how much dwarf galaxies contributed to our universe’s star population.
"These galaxies are forming stars so quickly they could actually double their entire mass of stars in only 150 million years -- an incredibly short astronomical timescale," study coauthor Jean-Paul Kneib of EPFL says in a news release. Massive growth like that would take normal galaxies 1 to 3 billion years.
The image above (and annotated below) shows a region of space containing thousands of galaxies, including a sample of distant and faint dwarf galaxies residing in the early universe. Some of them can be seen forming stars at a furiously fast rate.

Additionally, because it’s unusual to find a galaxy in a state of starburst, the observations suggest that starburst galaxies may be the result of an unusual incident in the past, such as a violent galaxy merger or a supernova explosion.

Mysterious Bright Object Spotted On Titan

Astronomers scouring through images taken by NASA’s Cassini spacecraft last year have discovered a fleeting bright spot in one of the seas of Saturn’s moon, Titan. The intriguing feature, which has been coined "Magic Island," had never seen observed in this sea before and it vanished again some days later. Although the scientists are uncertain of its identity at the moment, they speculate that it could be a glimpse of dynamic geological processes occurring in the northern hemisphere. The study has been published in Nature Geoscience.
Titan, the largest of Saturn’s 62 moons, is an intriguing and strangely Earth-like world that has sparked great interest from scientists in recent years. It is shrouded in a thick, golden atmosphere of mostly nitrogen that is reminiscent of an early Earth and it has an extensive system of lakes, seas and rivers filled with liquid ethane and methane.
Almost a year ago, Cassini snapped a series of images of Titan including some its second-largest sea, Ligeia Mare, which were sent to the Jet Propulsion Laboratory at Caltech for processing and analysis. Whilst flicking through the images and comparing them to older data to look for any changes, researchers discovered a curious bright spot in Ligeia Mare that was not present in images taken before the July 2013 observation.
The bright feature was around 12 miles long and 6 miles wide and was located about 6 miles off the southern shore. It was present in one image taken on 10 July but it had vanished in a subsequent data set taken on 26 July. Furthermore, prior to the 10 July observation, Ligeia Mare was as still as a statue and was completely devoid of ripples or waves.
The scientists ruled out that the blob could be due to errors in the imaging equipment and have been racking their brains to come up with ideas for what it could be. Titan’s northern hemisphere is currently undergoing a transition from spring to summer, which could be responsible for the bright feature. In light of this, the team has proposed four hypotheses that they believe could explain the phenomenon.
The first idea is that waves may be picking up due to the seasonal transition; if this is the case then the image would be the first observation of deep-sea waves on this moon. Warmer weather brings with it stronger winds, therefore it is possible that as the northern hemisphere starts to heat up the winds are kicking up waves in the sea.
“The sun is shining brighter, and that energy can be powering the winds,” lead author Jason Hofgartner told The Guardian. “All you would need is a light breeze, around half a meter per second.” However, he also doubts that the winds could ever be strong enough to produce substantial waves .
Alternatively it is possible that it is some of the solid material that is in suspension in the sea, or frozen material that has started to rise to the surface as the northern hemisphere warms. Lastly, it is also feasible that it could be a surge of gas released from the sea floor which would ascend to the surface as bubbles.
“Likely, several different processes- such as wind, rain and tides- might affect the methane and ethane lakes on Titan. We want to see the similarities and differences from geological processes that occur here on Earth,” Hofgartner said in a news-release. “Ultimately, it will help us to understand better our own liquid environments here on Earth.”

Cassini Probes Lakes On Titan

In a bid to further our knowledge of one of Saturn’s moons, Titan, a team of ground-based scientists successfully carried out a tricky maneuver last Wednesday using NASA’s Cassini spacecraft that allowed them to bounce a radio signal off the moon’s surface, sending information back to a receiver located 1 billion miles away on Earth. It is hoped that the data gathered will shed light on the composition of Titan’s vast liquid regions.
Titan, the largest of Saturn’s 62 moons, has attracted a lot of attention in recent years because of its bizarrely Earth-like qualities. Titan is cloaked in a dense, golden haze that obscures our view of its surface and kept its secrets hidden for many years. But data gathered recently, in particular observations from the Cassini spacecraft, has lifted the veil on this moon, revealing many unique features.
Much like Earth, Titan’s atmosphere is predominantly composed of Nitrogen and its surface is decorated with seas, lakes and flowing rivers. It has been hypothesized that rather than being filled with liquid water, they are composed of liquid methane or ethane. However, this suggestion is not based on direct observation but rather the fact that the conditions on Titan would result in methane and ethane being in a liquid state
“There is no really direct measurement that tells us what they are exactly,” Essam Marouf, a member of the Cassini radio science team, told LA Times. “If the data from this morning is good enough, it will tell us what these liquids really are.”
Marouf explains that they are basically using Titan as a mirror to bounce the Cassini radio signal back to Earth. The nature of this echo, which is picked up by a telescope array in Australia, should then hopefully give us a more thorough understanding of Titan’s surface.
While a similar operation was carried out back in May, at that time scientists were using Cassini to gather data on two of Titan’s vast seas; Ligea Mare and Kraken Mare. This time they directed the radio signal towards an area between these two seas which is known to contain smaller bodies of liquid.
Researchers are currently analyzing the data and hope to present the results at a Cassini meeting next week.

BICEP2 Team Admit Breakthrough Evidence For Big Bang Could Just Be Dust

Just months after the huge announcement was made to the world, the scientists who claimed they had finally gathered evidence that confirmed the Big Bang theory now admit that they may have been a little hasty.
Back in March, researchers from the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) collaboration announced that they had direct evidence for cosmic inflation, which was the rapid expansion of the universe immediately after the Big Bang. By measuring the Cosmic Microwave Background, which is the polarized radiation assumed to be the afterglow of the Big Bang, they claimed that they identified gravitational waves in space-time which were the first tremors of the Big Bang. These waves rippled through space from around 400,000 years after the universe was born.
“Detecting this signal is one of the most important goals in cosmology today,” John Kovac, leader of the BICEP2 collaboration, said back in March.
Pretty much as soon as the announcement was made, scientists voiced apprehensions about the findings. Some researchers were concerned that they may have mistaken signals emitted from dust for the gravitational waves, despite the fact that the team spent 3 years analyzing the data to rule out errors.
“We know that galactic dust emits polarized radiations. We see that in many areas of the sky, and what we pointed out in our paper is that pattern they have seen is just as consistent with the galactic dust radiations as with gravitational waves,” theoretical astrophysicist David Spergel told AFP.
Sure enough, in the paper published just last week by the BICEP2 collaboration in Physical Review Letters, the team acknowledges that they cannot exclude the possibility that the signal could be coming from dust.
Spergel said that upcoming results from a competing group using the ESA’s Planck telescope should finally settle the matter. Planck looks at a much larger region of the sky than BICEP2 and also collects measurements in six frequencies rather than just 1.
“I think in retrospect, they should have been more careful about making a big announcement,” Spergel added.

Earth-Sized "Diamond" Discovered in Space

Astronomers have identified what could be the coldest, faintest white dwarf star ever seen, so cold that its carbon has crystallized -- not unlike a diamond. The work was published in the Astrophysical Journal this week. 
White dwarfs are end-state stars that have collapsed to form hot, extremely dense, Earth-sized objects composed mostly of carbon and oxygen. While they can be as massive as the sun, white dwarfs are so dense they're only about the size of Earth. After they exhaust their nuclear fuel, white dwarfs will continue to cool and fade slowly over billions of years. This is what will ultimately become of our sun.
Objects this dim are really hard to spot. Combining observations from a variety of sources, including the Green Bank Telescope in West Virginia and the Very Long Baseline Array at Mauna Kea, a team led by David Kaplan at the University of Wisconsin-Milwaukee was able to do so because the object was located in a binary system.
The 11-billion-year-old, uncommonly cool white dwarf was discovered along with its pulsar companion, PSR J2222-0137. Pulsars are rapidly spinning neutron stars, the remains of massive stars that exploded as supernovas. As these stars spin, beams of radio waves stream from the poles of its magnetic field, and when one of these beams sweeps across Earth, radio telescopes can capture the pulse of the waves.
Researchers actually spotted the pulsar first. It was spinning more than 30 times a second and appeared to be gravitationally bound to a companion star -- which they initially thought was another neutron star. The two orbit each other once every 2.45 days. Observations of the pulsar over the next two years revealed its location and distance: 900 light-years from Earth and in the direction of the Aquarius constellation.
By studying how the gravity of the companion warped space and caused delays in the radio signal, the team was able to calculate both the mass of the pulsar (1.2 times that of the sun) and the companion (1.05 times that of the sun). That’s when they realized the other object couldn’t be a second neutron star: The orbits were too orderly for a second supernova to have taken place.
“Our final image should show us a companion 100 times fainter than any other white dwarf orbiting a neutron star and about 10 times fainter than any known white dwarf, but we don’t see a thing,” Bart Dunlap from the University of North Carolina at Chapel Hill explains in a news release. “If there’s a white dwarf there, and there almost certainly is, it must be extremely cold.”
Comparatively cold, to be clear. The white dwarf couldn’t be more than 2,700 degrees Celsius; the center of the sun is 5,000 times hotter. Astronomers believe such a cool ancient stellar remnant would be largely crystallized carbon -- which makes it, in effect, a diamond.

Titan's Atmosphere May Have Formed Before Saturn

Nitrogen in the atmosphere of Saturn's moon Titan's was formed at temperatures far colder than Saturn itself, throwing a major curveball into ideas of solar system formation, including the origins of our own atmosphere.
Like Earth, Titan's atmosphere is mainly nitrogen, and thought to serve as quite a good model of conditions on the early Earth. Most of it is nitrogen 14 (7 protons, 7 neutrons) but it also contains nitrogen 15 (7 and 8). Both are stable and while nitrogen 14 would be slightly more inclined to escape Titan's gravity to space, calculations by Dr Kathleen Mandt of Southwest Research Institute indicate this would not have occurred to an extent that would alter the composition over the lifetime of the solar system.
"When we looked closely at how this ratio could evolve with time, we found that it was impossible for it to change significantly. Titan's atmosphere contains so much nitrogen that no process can significantly modify this tracer even given more than four billion years of solar system history," Mandt says.
Consequently, Mandt could compare Titan's nitrogen ratio with that of other objects in the solar system. In the Astrophysical Journal Letters she reveals that Titan's atmosphere matches the nitrogen found in ammonia in comets from the outer reaches of the solar system, but not on Earth.
 “Titan's atmosphere must have originated as ammonia ice formed in the Protosolar Nebula under conditions similar to that of cometary formation,” the paper concludes. The comets of the outer reaches of the solar system are thought to predate the planets, including Saturn. Mandt has previously found that the methane in Titan's atmosphere is much younger, less than a billion years old.
At one point it was theorized that both Titan and Earth had atmospheres that would match the make-up of comets, but studies of comets undermined this idea, and the NASA/ESA Cassini-Huygens mission showed Titan's nitrogen ratio is different from the Earth's. The question then became whether Titan started that way, or had it evolved over time. Mandt claims to have solved that problem.
To complicate matters however, it is thought that comets born in the Oort Cloud and Kuiper Belt differ in their Hydrogen and Nitrogen isotopic ratios. Later this year the ESA's Rosetta mission will encounter comet 67P/Churyumov-Gerasimenko, thought to be a Kuiper Belt comet, providing an opportunity to test this idea. If, as anticipated, Kuiper Belt comets have a different isotopic ratio it will raise questions as to how Titan could resemble objects so much further out, rather than its (relatively speaking) neighbors.
The other challenge is to uncover the origin of our own atmosphere. At one time our own nitrogen rich atmosphere was thought to have been brought here by comets, but the difference with the isotopic ratio for Oort cloud comets undermined this, and the findings on Titan make it less credible still. "Some have suggested that meteorites brought nitrogen to Earth, or that nitrogen was captured directly from the disk of gas that formed the sun,”says Mandt This is an interesting puzzle for future investigations.”

Super-Earths Have Continents Too

Life as we know it needs water, but it would probably also like to live on a rocky world with a stable climate. That’s why huge, Earth-like exoplanets with both continents and oceans are better for harboring extraterrestrial life than waterworlds.
Super-Earths are typically thought to be covered entirely with water because their strong surface gravity would likely create a flattened topography and deep oceans. But in a study published in Astrophysical Journal earlier this year, Nicolas Cowan Northwestern University and Dorian Abbot from the University of Chicago argue that super-Earths have exposed continents and shallow oceans that allowed the planets to have a much more stable climate, making them far more habitable.
"A planet could be ten times wetter than Earth and still have exposed continents," Cowan tells Astrobiology Magazine. They used Earth as a starting point for modeling how these giants might store their water in surface reservoirs (oceans) and in underground, interior reservoirs within the mantle. They looked at how a planet’s water distribution could end up being balanced in a steady state between the surface oceans and the mantle.
"Earth is the only known planet with plate tectonics, a deep water cycle, etc., so it’s a good place to start," Cowan explains. "On the other hand, if it turns out that Earth’s deep water cycle is nowhere near a steady-state, then our conclusions are way off the mark. "
They found that super-Earths with active tectonics can have exposed continents if their water is less than 0.2 percent of the total planetary mass. "By making super-Earths 80 times more likely to have exposed continents," Abbot tells Gizmodo, "we've dramatically improved their odds of having Earth-like climate."
Water that’s deep in the mantle can re-enter the surface oceans when volcanic activity at mid-oceanic ridges splits the crust; this drop in pressure causes the mantle rock to lose its volatiles, like water. But because super-Earths have stronger gravity, the greater seafloor pressure suppresses the mantle’s loss of water. That means more of the planet’s overall water is stored in the mantle, and not overflowing their basins.
"If some of our input parameters are wildly off, then the actual water-world boundary might differ by an order of magnitude," Cowan says. "No matter how you cut it, though, the water-world boundary is unlikely to be as damning as previously thought."
You might remember how earlier this month astronomers announced a new mega-Earth: Called Kepler-10c, it’s about 17 times heavier than our planet. Researchers initially thought it was a Jupiter-like gas giant, before they realized how hefty and solid it is. No word yet on its continents.