Astronomers have combined data from NASA’s Chandra X-ray Observatory, the Hubble Space Telescope and the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) to conclude that a peculiar source of radio waves thought to be a distant galaxy is actually a nearby binary star system containing a low-mass star and a black hole. This identification suggests there may be a vast number of black holes in our Galaxy that have gone unnoticed until now.
For about two decades, astronomers have known about an object called VLA J213002.08+120904 (VLA J2130+12 for short). Although it is close to the line of sight to the globular cluster M15, most astronomers had thought that this source of bright radio waves was probably a distant galaxy.
Thanks to recent distance measurements with an international network of radio telescopes, including the EVN (European Very Long Baseline Interferometry Network) telescopes, the NSF’s Green Bank Telescope and Arecibo Observatory, astronomers realized that VLA J2130+12 is at a distance of 7,200 light years, showing that it is well within our own Milky Way galaxy and about five times closer than M15. A deep image from Chandra reveals it can only be giving off a very small amount of X-rays, while recent VLA data indicates the source remains bright in radio waves.
This new study indicates that VLA J2130+12 is a black hole a few times the mass of our Sun that is very slowly pulling in material from a companion star. At this paltry feeding rate, VLA J2130+12 was not previously flagged as a black hole since it lacks some of the telltale signs that black holes in binaries typically display.
“Usually, we find black holes when they are pulling in lots of material. Before falling into the black hole this material gets very hot and emits brightly in X-rays,” said Bailey Tetarenko of the University of Alberta, Canada, who led the study. “This one is so quiet that it’s practically a stealth black hole.”
This is the first time a black hole binary system outside of a globular cluster has been initially discovered while it is in such a quiet state.
Hubble observations identified VLA J2130+12 with a star having only about one-tenth to one-fifth the mass of the Sun. The observed radio brightness and the limit on the X-ray brightness from Chandra allowed the researchers to rule out other possible interpretations, such as an ultra-cool dwarf star, a neutron star, or a white dwarf pulling material away from a companion star.
Because this study only covered a very small patch of sky, the implication is that there should be many of these quiet black holes around the Milky Way. The estimates are that tens of thousands to millions of these black holes could exist within our Galaxy, about three to thousands of times as many as previous studies have suggested.
“Unless we were incredibly lucky to find one source like this in a small patch of the sky, there must be many more of these black hole binaries in our Galaxy than we used to think,” said co-author Arash Bahramian, also of the University of Alberta.
There are other implications of finding that VLA J2130+12 is relatively near to us.
“Some of these undiscovered black holes could be closer to the Earth than we previously thought,” said Robin Arnason, a co-author from Western University, Canada “However there’s no need to worry as even these black holes would still be many light years away from Earth.”
Sensitive radio and X-ray surveys covering large regions of the sky will need to be performed to uncover more of this missing population.
If, like many others, this black hole was formed in the plane of the Milky Way’s disk, it would have needed a large kick at birth to launch it to its current position about 3,000 light years above the plane of the Galaxy.
These results appear in a paper in The Astrophysical Journal. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra’s science and flight operations.
Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered a rotating ring containing large organic molecules around a protostar. This observation definitively shows that organic materials formed in interstellar space are brought into the planet-forming region. Researchers also found that the molecular species brought into the planet-forming region vary from one protostar to another. Chemical composition is a new way to answer the long-standing question of whether or not the Solar System is a typical example of a planetary system.
Astronomers have long known that organic molecules form in diffuse gas clouds floating between stars. It is thought that as the Solar System formed 4.6 billion years ago, some of these organic molecules were transported from interstellar space to the planet forming disk. Later, these molecules played important roles in the chemical evolution resulting in the emergence of life on the Earth. However, it is still unknown what kinds and quantities of organic molecules were actually supplied from interstellar space. Although radio astronomy observations during the last decade showed that saturated complex organic molecules, such as methanol (CH3OH) and methyl formate (HCOOCH3) , exist around Solar-type protostars, their distributions were too compact to be resolved with the radio telescopes available at the time.
With ALMA, an international team lead by Yoko Oya, a graduate student of Department of Physics, The University of Tokyo, and Nami Sakai, an associate chief scientist of RIKEN, studied the distribution of various organic molecules around a Solar-type protostar IRAS 16293-2422A at a high spatial resolution. They discovered a ring structure of complex organic molecules around the protostar. The radius of the ring is 50 times wider than the Earth’s orbit. This size is comparable to the size of the Solar System, and the ring structure most likely represents the boundary region between infalling gas and a rotating disk structure around the protostar.
The observations clearly showed the distribution of large organic molecules methyl formate (HCOOCH3) and carbonyl sulfide (OCS). Apparently the distribution of methyl formate is confined in a more compact area around the protostar than the OCS distribution, which mainly traces the infalling gas. “When we measured the motion of the gas containing methyl formate by using the Doppler effect,” said Oya “we found a clear rotation motion specific to the ring structure.” In this way, they identified the rotating ring structure of methyl formate, although it is not resolved spatially. A similar ring structure is also found for methanol.
These saturated organic molecules are formed in interstellar space and are preserved on the surfaces of dust grains. Around the outer boundary of the disk structure, they evaporate due to shock generated by collisions of the disk and infalling material, and/or due to heating by the light from the baby star. This result is the first direct evidence that interstellar organic materials are indeed fed into the rotating disk structure that eventually forms a planetary system.
In 2014, the team found a similar ring structure of SO (sulfur monoxide) around another Solar-type protostar L1527. In this source, unsaturated complex organic molecules such as CCH and cyclic-C3H2 are very abundant in the infalling gas, while SO preferentially exists in the boundary between the infalling gas and the disk structure. Although the physical structure in L1527 is similar to that found in IRAS 16293-2422A, the chemical composition is much different. Saturated complex organic molecules are almost completely absent in L1527. The present result, taken together with previous results on L1527, clearly demonstrates for the first time that the materials delivered to a planetary system differ from star to star. A new perspective on chemical composition is thus indispensable for a thorough understanding of the origin of the Solar System and the origin of life on the Earth.
Chemicals found in Martian rocks by NASA’s Curiosity Mars rover suggest the Red Planet once had more oxygen in its atmosphere than it does now.
Researchers found high levels of manganese oxides by using a laser-firing instrument on the rover. This hint of more oxygen in Mars’ early atmosphere adds to other Curiosity findings — such as evidence about ancient lakes — revealing how Earth-like our neighboring planet once was.
This research also adds important context to other clues about atmospheric oxygen in Mars’ past. The manganese oxides were found in mineral veins within a geological setting the Curiosity mission has placed in a timeline of ancient environmental conditions. From that context, the higher oxygen level can be linked to a time when groundwater was present in the rover’s Gale Crater study area.
“The only ways on Earth that we know how to make these manganese materials involve atmospheric oxygen or microbes,” said Nina Lanza, a planetary scientist at Los Alamos National Laboratory in New Mexico. “Now we’re seeing manganese oxides on Mars, and we’re wondering how the heck these could have formed?”
Microbes seem far-fetched at this point, but the other alternative — that the Martian atmosphere contained more oxygen in the past than it does now — seems possible, Lanza said. “These high manganese materials can’t form without lots of liquid water and strongly oxidizing conditions. Here on Earth, we had lots of water but no widespread deposits of manganese oxides until after the oxygen levels in our atmosphere rose.”
Lanza is the lead author of a new report about the Martian manganese oxides in the American Geophysical Union’s Geophysical Research Letters. She uses Curiosity’s Chemistry and Camera (ChemCam) instrument, which fires laser pulses from atop the rover’s mast and observes the spectrum of resulting flashes of plasma to assess targets’ chemical makeup.
In Earth’s geological record, the appearance of high concentrations of manganese oxide minerals is an important marker of a major shift in our atmosphere’s composition, from relatively low oxygen abundances to the oxygen-rich atmosphere we see today. The presence of the same types of materials on Mars suggests that oxygen levels rose there, too, before declining to their present values. If that’s the case, how was that oxygen-rich environment formed?
“One potential way that oxygen could have gotten into the Martian atmosphere is from the breakdown of water when Mars was losing its magnetic field,” said Lanza. “It’s thought that at this time in Mars’ history, water was much more abundant.” Yet without a protective magnetic field to shield the surface, ionizing radiation started splitting water molecules into hydrogen and oxygen. Because of Mars’ relatively low gravity, the planet wasn’t able to hold onto the very light hydrogen atoms, but the heavier oxygen atoms remained behind. Much of this oxygen went into rocks, leading to the rusty red dust that covers the surface today. While Mars’ famous red iron oxides require only a mildly oxidizing environment to form, manganese oxides require a strongly oxidizing environment, more so than previously known for Mars.
Lanza added, “It’s hard to confirm whether this scenario for Martian atmospheric oxygen actually occurred. But it’s important to note that this idea represents a departure in our understanding for how planetary atmospheres might become oxygenated.” Abundant atmospheric oxygen has been treated as a so-called biosignature, or a sign of extant life, but this process does not require life.
Curiosity has been investigating sites in Gale Crater since 2012. The high-manganese materials it found are in mineral-filled cracks in sandstones in the “Kimberley” region of the crater. But that’s not the only place on Mars where high manganese abundances have been found. NASA’s Opportunity rover, exploring Mars since 2004, also recently discovered high manganese deposits thousands of miles from Curiosity. This supports the idea that the conditions needed to form these materials were present well beyond Gale Crater.
Los Alamos National Laboratory leads the U.S. and French team that jointly developed and operates ChemCam. NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, built the rover and manages the Curiosity mission for NASA’s Science Mission Directorate, Washington.
Around 4.6 billion years ago, the universe was a chaos of collapsing gas and spinning debris. Small particles of gas and dust clumped together into larger and more massive meteoroids that in turn smashed together to form planets. Scientists believe that shortly after their formation, these planets — and particularly Mercury — were fiery spheres of molten material, which cooled over millions of years.
Now, geologists at MIT have traced part of Mercury’s cooling history and found that between 4.2 and 3.7 billion years ago, soon after the planet formed, its interior temperatures plummeted by 240 degrees Celsius, or 464 degrees Fahrenheit.
They also determined, based on this rapid cooling rate and the composition of lava deposits on Mercury’s surface, that the planet likely has the composition of an enstatite chondrite — a type of meteorite that is extremely rare here on Earth.
Timothy Grove, the Cecil and Ida Green Professor of Geology in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, says new information on Mercury’s past is of interest for tracing Earth’s early formation.
“Here we are today, with 4.5 billion years of planetary evolution, and because the Earth has such a dynamic interior, because of the water we’ve preserved on the planet, [volcanism] just wipes out its past,” Grove says. “On planets like Mercury, early volcanism is much more dramatic, and [once] they cooled down there were no later volcanic processes to wipe out the early history. This is the first place where we actually have an estimate of how fast the interior cooled during an early part of a planet’s history.”
Grove and his colleagues, including researchers from the University of Hanover, in Germany; the University of Liége, in Belgium; and the University of Bayreuth, in Germany, have published their results in Earth and Planetary Science Letters.
Compositions in craters
For their analysis, the team utilized data collected by NASA’s MESSENGER spacecraft. The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) probe orbited Mercury between 2011 and 2015, collecting measurements of the planet’s chemical composition with each flyby. During its mission, MESSENGER produced images that revealed kilometer-thick lava deposits covering the entire planet’s surface.
An X-ray spectrometer onboard the spacecraft measured the X-ray radiation from the planet’s surface, produced by solar flares on the sun, to determine the chemical composition of more than 5,800 lava deposits on Mercury’s surface.
Grove’s co-author, Olivier Namur of the University of Hanover, recalculated the surface compositions of all 5,800 locations, and correlated each composition with the type of terrain in which it was found, from heavily cratered regions to those that were less impacted. The density of a region’s craters can tell something about that region’s age: The more craters there are, the older the surface is, and vice versa. The researchers were able to correlate Mercury’s lava composition with age and found that older deposits, around 4.2 billion years old, contained elements that were very different from younger deposits that were estimated to be 3.7 billion years old.
“It’s true of all planets that different age terrains have different chemical compositions because things are changing inside the planet,” Grove says. “Why are they so different? That’s what we’re trying to figure out.”
A rare rock, 10 standard deviations away
To answer that question, Grove attempted to retrace a lava deposit’s path, from the time it melted inside the planet to the time it ultimately erupted onto Mercury’s surface.
To do this, he started by recreating Mercury’s lava deposits in the lab. From MESSENGER’s 5,800 compositional data points, Grove selected two extremes: one representing the older lava deposits and one from the younger deposits. He and his team converted the lava deposits’ element ratios into the chemical building blocks that make up rock, then followed this recipe to create synthetic rocks representing each lava deposit.
The team melted the synthetic rocks in a furnace to simulate the point in time when the deposits were lava, and not yet solidified as rock. Then, the researchers dialed the temperature and pressure of the furnace up and down to effectively turn back the clock, simulating the lava’s eruption from deep within the planet to the surface, in reverse.
Throughout these experiments, the team looked for tiny crystals forming in each molten sample, representing the point at which the sample turns from lava to rock. This represents the stage at which the planet’s solid rocky core begins to melt, creating a molten material that sloshes around in Mercury’s mantle before erupting onto the surface.
The team found a surprising disparity in the two samples: The older rock melted deeper in the planet, at 360 kilometers, and at higher temperatures of 1,650 C, while the younger rock melted at shallower depths, at 160 kilometers, and 1,410 C. The experiments indicate that the planet’s interior cooled dramatically, over 240 degrees Celsius between 4.2 and 3.7 billion years ago — a geologically short span of 500 million years.
“Mercury has had a huge variation in temperature over a fairly short period of time, that records a really amazing melting process,” Grove says.
The researchers determined the chemical compositions of the tiny crystals that formed in each sample, in order to identify the original material that may have made up Mercury’s interior before it melted and erupted onto the surface. They found the closest match to be an enstatite chondrite, an extremely rare form of meteorite that is thought to make up only about 2 percent of the meteorites that fall to Earth.
“We now know something like an enstatite chondrite was the starting material for Mercury, which is surprising, because they are about 10 standard deviations away from all other chondrites,” Grove says.
Grove cautions that the group’s results are not set in stone and that Mercury may have been an accumulation of other types of starting materials. To know this would require an actual sample from the planet’s surface.
“The next thing that would really help us move our understanding of Mercury way forward is to actually have a meteorite from Mercury that we could study,” Grove says. “That would be lovely.”
Planetary scientists have discovered pieces of opal in a meteorite found in Antarctica, a result that demonstrates that meteorites delivered water ice to asteroids early in the history of the solar system. Led by Professor Hilary Downes of Birkbeck College London, the team announce their results at the National Astronomy Meeting in Nottingham on Monday 27 June.
Opal, familiar on Earth as a precious stone used in jewellery, is made up of silica (the major component of sand) with up to 30% water in its structure, and has not yet been identified on the surface of any asteroid. Before the new work, opal had only once been found in a meteorite, as a handful of tiny crystals in a meteorite from Mars.
Downes and her team studied the meteorite, named EET 83309, an object made up of thousands and broken pieces of rock and minerals, meaning that it originally came from the broken up surface, or regolith, of an asteroid. Results from other teams show that while the meteorite was still part of the asteroid, it was exposed to radiation from the Sun, the so-called solar wind, and from other cosmic sources. Asteroids lack the protection of an atmosphere, so radiation hits their surfaces all the time.
EET 83309 has fragments of many other kinds of meteorite embedded in it, showing that there were many impacts on the surface of the parent asteroid, bringing pieces of rock from elsewhere in the solar system. Downes believes one of these impacts brought water ice to the surface of the asteroid, allowing the opal to form.
She comments: “The pieces of opal we have found are either broken fragments or they are replacing other minerals. Our evidence shows that the opal formed before the meteorite was blasted off from the surface of the parent asteroid and sent into space, eventually to land on Earth in Antarctica.”
“This is more evidence that meteorites and asteroids can carry large amounts of water ice. Although we rightly worry about the consequences of the impact of large asteroid, billions of years ago they may have brought the water to the Earth and helped it become the world teeming with life that we live in today.”
The team used different techniques to analyse the opal and check its composition. They see convincing evidence that it is extra-terrestrial in origin, and did not form while the meteorite was sitting in the Antarctic ice. For example, using the NanoSims instrument at the Open University, they can see that although the opal has interacted to some extent with water in the Antarctic, the isotopes (different forms of the same element) match the other minerals in the original meteorite.
Astronomers have detected what may be the most-rapidly-rotating, ultra-cool, brown-dwarf star ever seen. The super-fast rotation period was measured by using the 305-meter Arecibo radio telescope — the same telescope that was used to discover the first planets ever found outside our solar system.
“Our new detection of an ultra-cool dwarf emphasizes Arecibo’s amazing sensitivity, which enables measurements of the magnetic fields of very-low-mass stars, brown dwarfs, and potentially planets. Because planetary magnetic fields protect life from the harmful effects of stellar activity, it is clear that future programs of this kind using the Arecibo telescope will be crucial to our understanding of the habitability of planets around other stars,” said Alex Wolszczan, a co-discoverer with Matthew Route of radio emission from this new brown-dwarf star.
The discovery is detailed in a recent issue of The Astrophysical Journal Letters (Volume 821, L21), coauthored by Wolszczan, Evan Pugh University Professor of Astronomy and Astrophysics at Penn State University; and Route, a Senior Scientific Applications Analyst at Purdue University and a Penn State Ph.D. graduate. The repeated radio flares that they found being emitted by the brown dwarf allowed them to measure the extremely fast rotation of this exotic object. Their record-breaking detection demonstrates that even the coolest brown dwarfs, and possibly young giant planets, can be discovered and studied using radio observations.
“Our discovery of the super-fast rotation of J1122+25 poses new challenges for the theoretical models of the rotational evolution of these objects and the internal dynamos that power their magnetic fields,” Route said. J1122+25 is the short version of the scientific name of this new brown dwarf, WISEPC J112254.73+255021.5. “The radio flaring and rapid rotation of J1122+25 can reveal a lot about the origin and evolution of the magnetic fields of brown dwarfs, and how this knowledge can be applied to young giant planets,” Route said.
The data collected so far from this brown dwarf show that it could be rotating every 17, 34, or 51 minutes — an ambiguity that requires the collection of more data to identify which of the three measurements is this star’s rotational period. But, the scientists report, even the longest of these rotation periods would mean this brown dwarf rotates much faster than any measured so far.
The brown dwarf was first discovered by the Wide-field Infrared Survey Explorer (WISE) in 2011. Route and Wolszczan subsequently observed J1122+25 at five epochs spread over an eight-month period as part of an ongoing search for brown dwarfs with sudden outbursts of energy at radio wavelengths — called flaring ratio emission. “J1122+25 is about 55 light years away and is only one of six coolest brown dwarfs for which radio flares have been detected,” Route said.
Brown dwarfs like J1122+25 are sometimes called “failed stars” because they did not accumulate enough material when they formed in order to fuse hydrogen into helium, the process that enables stars to shine. The lack of continuous energy production from fusion makes brown dwarfs much colder and dimmer than most stars and gives them much different chemistry. For some of them, internal structure in connection with rapid rotation can generate strong magnetic fields and the dramatic radio flares that have been detected by the Arecibo telescope.
Many astronomers treat brown dwarfs as the “missing link” between stars and planets. Brown dwarfs share many physical traits with gas-giant planets like Jupiter. Studies of ultra-cool brown dwarfs like J1122+25 can be used to infer the properties of giant planets, which are much harder than stars to study in detail. J1122+25 is about one-sixth the temperature of the Sun, and emits light primarily in infrared wavelengths