Matt Williams is a space journalist and science communicator for Universe Today and Interesting Engineering. He's also a science fiction author, podcaster (Stories from Space), and Taekwon-Do instructor who lives on Vancouver Island with his wife and family.
Most exoplanets orbit red dwarf stars because they're the most plentiful stars. This is an artist's illustration of what the TRAPPIST-1 system might look like from a vantage point near planet TRAPPIST-1f (at right). Credits: NASA/JPL-Caltech
In February of 2017, NASA scientists announced the existence of seven terrestrial (i.e. rocky) planets within the TRAPPIST-1 star system. Since that time, the system has been the focal point of intense research to determine whether or not any of these planets could be habitable. At the same time, astronomers have been wondering if all of the system’s planets are actually accounted for.
For instance, could this system have gas giants lurking in its outer reaches, as many other systems with rocky planets (for instance, ours) do? That was the question that a team of scientists, led by researchers from the Carnegie Institute of Science, sought to address in a recent study. According to their findings, TRAPPIST-1 may be orbited by gas giants at a much-greater distance than its seven rocky planets.
Mosaic image of the Curiosity rover on Mars, which recently turned up more evidence that supports the idea that the planet was once habitability. Credit: NASA/JPL-Caltech/MSSS.
It has become a well-known scientific fact that billions of years ago, Mars once had a thicker atmosphere and liquid water on its surface. Scientists have also discovered that it was the gradual loss of this atmosphere, between 4.2 and 3.7 billion years ago, that caused Mars to go from being a warmer, wetter environment to the dry, freezing environment it is today.
Despite the existence of both a thicker atmosphere and water, questions remain as to whether or not Mars was truly habitable in the past. According to a new study from a team of researchers from the Los Alamos National Laboratory (LANL), the discovery of a specific mineral (boron) has added weight to the argument that Mars was once a potentially life-bearing world.
The study, titled “In situ detection of boron by ChemCam on Mars“, was recently published in the scientific journal Geophysical Research Letters. For the sake of this study, the LANL research team consulted data collected by the Chemistry and Camera (ChemCam) instrument aboard the Curiosity rover, which showed evidence of boron on the surface of Mars.
Mars, as it may have looked 4.2 billion years ago (left) and today (right). Credit: Kevin Gill
Boron, an element which is created by cosmic rays and is relatively rare in the Solar System, is necessary for the creation of ribonucleic acid – which is present in all forms of modern life. Essentially, RNA requires a key ingredient to form, which is a sugar called ribose. Like all sugars, ribose is highly unstable and decomposes quickly in water. As such, it needs another element to stabilize it, which is where boron comes into play.
As Patrick Gasda, a postdoctoral researcher at the Los Alamos National Laboratory and lead author on the paper, explained in a LANL press statement:
“Because borates may play an important role in making RNA – one of the building blocks of life – finding boron on Mars further opens the possibility that life could have once arisen on the planet. Borates are one possible bridge from simple organic molecules to RNA. Without RNA, you have no life. The presence of boron tells us that, if organics were present on Mars, these chemical reactions could have occurred.”
When boron is dissolved in water (which, as noted, Mars once had in abundance) it becomes borate. This compound (when combined with ribose) would act as a stabilizing agent, keeping the sugar together long enough so that RNA can form. As Gasda explained, “We detected borates in a crater on Mars that’s 3.8 billion years old, younger than the likely formation of life on Earth.”
Artist rendition of how the “lake” at Gale Crater on Mars may have looked millions of years ago. Credit and copyright: Kevin Gill.
The boron was detected by Curiosity’s laser-shooting ChemCam instrument, which was developed by the LANL in conjunction with France’s space agency, the National Center of Space Studies (CNES). It detected the element in veins of calcium sulfate minerals located in the Gale Crater, which means that boron was present in Mars’ groundwater and was preserved with other minerals when the water dissolved, leaving behind rich mineral veins.
This provides further evidence that the lake that is now known to have once filled the Gale Crater could have had life in it. During the time period in question, this lake would have experienced temperatures ranging from from 0 to 60 ° C (32 to 140 °F) and had a pH level that would have been neutral-to-alkaline. It also means that on ancient Mars, the conditions necessary for life would have existed, and independent of Earth to boot.
This is just one of many findings Curiosity has made related to the composition of Martian rocks. Since it touched down in the Gale Crater in 2012, the rover has been gathering chemical evidence of the ancient lake that once existed there, as well as geological evidence that has been preserved by sedimentary deposits. As the rover began to scale the slope of Mount Sharp, the composition of the surface began to change.
Whereas samples taken from the crater floor tended to contain more in the way of clays, samples collected higher up Mount Sharp contained more boron. These and other chemical traces are indications of how conditions under which sediments were deposited changed over time. Analysis conducted of the mountain’s layers has also showed how the movement of groundwater through these layers of sediment altered and transported elements (like boron).
MRO image of Gale Crater illustrating the landing location and trek of the Rover Curiosity. Credits: NASA/JPL, illustration, T.Reyes
All of this is providing a picture of how Mars’ environment changed over the course of billions of years and affected the planet’s potential favorability for microbial life. And while scientists have a general picture of how Mars underwent a very significant transition billions of years ago, whether or not Martian life ever existed remains unknown.
The main goal of the Curiosity mission was to determine whether the area ever offered a habitable environment. Thanks to evidence of past water and the discovery of minerals like boron, this has been confirmed. In the coming years, the deployment of the Mars 2020 rover is expected to follow-up on these findings and shed more light on Mars’ case for past habitability.
Once it reaches the surface, the Mars 2020 rover – which relies on much of the same technology as Curiosity – will use an instrument called the Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC). Also developed by the LANL, this “SuperCam” instrument will use spectrometers, a laser and a camera to search for organics and minerals that could indicate the existence of past microbial life.
If there is still preserved evidence of life to be found on Mars or – fingers crossed! – microbial life still exists there today, we can expect to find it before long. If that should be the case, human beings will finally know with certainty that life evolved on a planet other than Earth, and perhaps independent of it!
An artist's conception of a hypervelocity star that has escaped the Milky Way. Credit: NASA
Most stars in our galaxy behave predictably, orbiting around the center of the Milky Way at speeds of about 100 km/s (62 mi/s). But some stars achieve velocities that are significantly greater, to the point that they are even able to escape the gravitational pull of the galaxy. These are known as hypervelocity stars (HVS), a rare type of star that is believed to be the result of interactions with a supermassive black hole (SMBH).
The existence of HVS is something that astronomers first theorized in the late 1980s, and only 20 have been identified so far. But thanks to a new study by a team of Chinese astronomers, two new hypervelocity stars have been added to that list. These stars, which have been designated LAMOST-HVS2 and LAMOST-HVS3, travel at speeds of up to 1,000 km/s (620 mi/s) and are thought to have originated in the center of our galaxy.
Footprint of the LAMOST pilot survey and the first three years’ general survey. Credit: LAMOST
Astronomers estimates that only 1000 HVS exist within the Milky Way. Given that there are as many as 200 billion stars in our galaxy, that’s just 0.0000005 % of the galactic population. While these stars are thought to originate in the center of our galaxy – supposedly as a result of interaction with our SMBH, Sagittarius A* – they manage to travel pretty far, sometimes even escaping our galaxy altogether.
It is for this very reason that astronomers are so interested in HVS. Given their speed, and the vast distances they can cover, tracking them and creating a database of their movements could provide constraints on the shape of the dark matter halo of our galaxy. Hence why Dr. Huang and his colleagues began sifting through LAMOST data to find evidence of new HVS.
Located in Hebei Province, northwestern China, the LAMOST observatory is operated by the Chinese Academy of Sciences. Over the course of five years, this observatory conducted a spectroscopic survey of 10 million stars in the Milky Way, as well as millions of galaxies. In June of 2017, LAMOST released its third Data Release (DR3), which included spectra obtained during the pilot survey and its first three years’ of regular surveys.
Containing high-quality spectra of 4.66 million stars and the stellar parameters of an additional 3.17 million, DR3 is currently the largest public spectral set and stellar parameter catalogue in the world. Already, LAMOST data had been used to identify one hypervelocity star, a B1IV/V-type (main sequence blue subgiant/subdwarf) star that was 11 Solar Masses, 13490 times as bright as our Sun, and had an effective temperature of 26,000 K (25,727 °C; 46,340 °F).
Artist’s impression of hypervelocity stars (HVSs) speeding through the Galaxy. Credit: ESA
This HVS was designated LAMOST-HSV1, in honor of the observatory. After detecting two new HVSs in the LAMOST data, these stars were designated as LAMOST-HSV2 and LAMOST-HSV3. Interestingly enough, these newly-discovered HVSs are also main sequence blue subdwarfs – or a B2V-type and B7V-type star, respectively.
Whereas HSV2 is 7.3 Solar Masses, is 2399 times as luminous as our Sun, and has an effective temperature of 20,600 K (20,327 °C; 36,620 °F), HSV3 is 3.9 Solar Masses, is 309 times as luminous as the Sun, and has an effective temperature of 14,000 K (24,740 °C; 44,564 °F). The researchers also considered the possible origins of all three HVSs based on their spatial positions and flight times.
In addition to considering that they originated in the center of the Milky Way, they also consider alternate possibilities. As they state in their study:
“The three HVSs are all spatially associated with known young stellar structures near the GC, which supports a GC origin for them. However, two of them, i.e. LAMOST-HVS1 and 2, have life times smaller than their flight times, indicating that they do not have enough time to travel from the GC to the current positions unless they are blue stragglers (as in the case of HVS HE 0437-5439). The third one (LAMOST-HVS3) has a life time larger than its flight time and thus does not have this problem.
In other words, the origins of these stars is still something of a mystery. Beyond the idea that they were sped up by interacting with the SMBH at the center of our galaxy, the team also considered other possibilities that have suggested over the years.
Artist’s impression of the ESA’s Gaia spacecraft, looking into the heart of the Milky Way Galaxy. Credit: ESA/ATG medialab/ESO/S. Brunier
As they state in these study, these “include the tidal debris of an accreted and disrupted dwarf galaxy (Abadi et al. 2009), the surviving companion stars of Type Ia supernova (SNe Ia) explosions (Wang & Han 2009), the result of dynamical interaction between multiple stars (e.g, Gvaramadze et al. 2009), and the runaways ejected from the Large Magellanic Cloud (LMC), assuming that the latter hosts a MBH (Boubert et al. 2016).”
In the future, Huang and his colleagues indicate that their study will benefit from additional information that will be provided by the ESA’s Gaia mission, which they claim will shed additional light on how HVS behave and where they come from. As they state in their conclusions:
“The upcoming accurate proper motion measurements by Gaia should provide a direct constraint on their origins. Finally, we expect more HVSs to be discovered by the ongoing LAMOST spectroscopic surveys and thus to provide further constraint on the nature and ejection mechanisms of HVSs.”
Artist's illustration of a rotating neutron star, the remnants of a super nova explosion. Credit: NASA, Caltech-JPL
Pulsars are what remains when a massive star undergoes gravitational collapse and explodes in a supernova. These remnants (also known as neutron stars) are extremely dense, with several Earth-masses crammed into a space the size of a small country. They also have powerful magnetic fields, which causes them to rotate rapidly and emit powerful beams of gamma rays or x-rays – which lends them the appearance of a lighthouse.
In some cases, pulsars spin especially fast, taking only milliseconds to complete a single rotation. These “millisecond pulsars” remain a source of mystery for astronomers. And after following up on previous observations, researchers using the Low Frequency Array (LOFAR) radio telescope in the Netherlands identified a pulsar (PSR J0952?0607) that spins more than 42,000 times per minute, making it the second-fastest pulsar ever discovered.
An all-sky view in gamma ray light made with the Fermi gamma ray space telescope. Credit: NASA/DOE/International LAT Team
This study was part of an ongoing LOFAR survey of energetic sources originally identified by NASA’s Fermi Gamma-ray space telescope. The purpose of this survey was to distinguish between the gamma-ray sources Fermi detected, which could have been caused by neutron stars, pulsars, supernovae or the regions around black holes. As Elizabeth Ferrara, a member of the discovery team at NASA’s Goddard Space Center, explained in a NASA press release:
“Roughly a third of the gamma-ray sources found by Fermi have not been detected at other wavelengths. Many of these unassociated sources may be pulsars, but we often need follow-up from radio observatories to detect the pulses and prove it. There’s a real synergy across the extreme ends of the electromagnetic spectrum in hunting for them.”
Their follow-up observations indicated that this particular source was a pulsar that spins at a rate of 707 revolutions (Hz) per second, which works out to 42,000 revolutions per minute. This makes it, by definition, a millisecond pulsar. The team also confirmed that it is about 1.4 Solar Masses and is orbited every 6.4 hours by a companion star that has been stripped down to less than 0.05 Jupiter masses.
The presence of this lightweight companion is a further indication of how the spin of this pulsar became so rapid. Over time, matter would have been stripped away from the star, gradually accreting onto PSR J0952?0607. This would not only raise its spin rate but also greatly increase its electromagnetic emissions. The process continues to this day, with the star becoming increasingly smaller as the pulsar becomes more energetic.
Artist’s impression of a pulsar siphoning material from a companion star. Credit: NASA
Because of the nature of this relationship (which can only be described as “cannibalistic”), systems like PSR J0952?0607 are often called “black widow” or “redback” pulsars. Most of these systems were found by following up on sources identified by the Fermi mission, since the process has been known to result in a considerable amount of electromagnetic radiation being released.
Beyond the discovery of this record-setting pulsar, the LOFAR discovery could also be an indication that there is a new population of ultra-fast spinning pulsars in our Universe. As Dr. Bassa explained:
“LOFAR picked up pulses from J0952 at radio frequencies around 135 MHz, which is about 45 percent lower than the lowest frequencies of conventional radio searches. We found that J0952 has a steep radio spectrum, which means its radio pulses fade out very quickly at higher frequencies. It would have been a challenge to find it without LOFAR.”
The fastest spinning pulsar known, PSR J1748-2446ad, spins just slightly faster than PSR J0952?0607 – reaching a rate of nearly 43,000 rpm (or 716 revolutions per second). But some theorists think that pulsars could spin as fast as 72,000 rpm (almost twice as fast) before breaking up. This remains a theory, since rapidly-spinning pulsars are rather difficult to detect.
But with the help of instrument like LOFAR, that could be changing. For instance, both PSR J1748-2446ad and PSR J0952?0607 were shown to have steep spectra – much like radio galaxies and Active Galactic Nuclei. The same was true of J1552+5437, another millisecond pular detected by LOFAR which spins at 25,000 rpm.
As Ziggy Pleunis – a doctoral student at McGill University in Montreal and a co-author on the study – indicated, this could be a sign that the fastest-spinning pulsars are just waiting to be found.
“There is growing evidence that the fastest-spinning pulsars tend to have the steepest spectra,” he said. “Since LOFAR searches are more sensitive to these steep-spectrum radio pulsars, we may find that even faster pulsars do, in fact, exist and have been missed by surveys at higher frequencies.”
As with many other areas of astronomical research, improvements in instrumentation and methodology are allowing for new and exciting discoveries. As expected, some of the things we are finding are forcing astronomers to rethink more than a few previously-held assumptions about the nature and limits of certain phenomena.
Be sure to enjoy this NASA video that explains “black widow” pulsars and the ongoing search to find them:
According to a new study, the motions of our Sun around its center of mass could make it impossible to detect another Earth in a distant star system. Credit: ESO
In the hunt for extra-solar planets, astronomers and enthusiasts can be forgiven for being a bit optimistic. In the course of discovering thousands of rocky planets, gas giants, and other celestial bodies, is it too much to hope that we might someday find a genuine Earth-analog? Not just an “Earth-like” planet (which implies a rocky body of comparable size) but an actual Earth 2.0?
This has certainly been one of the goals of exoplanet-hunters, who are searching nearby star systems for planets that are not only rocky, but orbit within their star’s habitable zone, show signs of an atmosphere and have water on their surfaces. But according to a new study by Alexey G. Butkevich – a astrophysicist from the Pulkovo Observatory in St. Petersburg, Russia – our attempts to discover Earth 2.0 could be hindered by Earth itself!
Butkevich’s study, titled “Astrometric Exoplanet Detectability and the Earth Orbital Motion“, was recently published in the Monthly Notices of the Royal Astronomical Society. For the sake of his study, Dr. Butkevich examined how changes in the Earth’s own orbital position could make it more difficult to conduct measurements of a star’s motion around its system’s barycenter.
Artist’s impression of how an Earth-like planet might look from space. Credit: ESO.
This method of exoplanet detection, where the motion of a star around the star system’s center of mass (barycenter), is known as the Astrometic Method. Essentially, astronomers attempt to determine if the presence of gravitational fields around a star (i.e. planets) are causing the star to wobble back and forth. This is certainly true of the Solar System, where our Sun is pulled back and forth around a common center by the pull of all its planets.
In the past, this technique has been used to identify binary stars with a high degree of precision. In recent decades, it has been considered as a viable method for exoplanet hunting. This is no easy task since the wobbles are rather difficult to detect at the distances involved. And until recently, the level of precision required to detect these shifts was at the very edge of instrument sensitivity.
This is rapidly changing, thanks to improved instruments that allow for accuracy down to the microarcsecond. A good example of this is the ESA’s Gaia spacecraft, which was deployed in 2013 to catalog and measure the relative motions of billions of stars in our galaxy. Given that it can conduct measurements at 10 microarcseconds, it is believed that this mission could conduct astrometric measurements for the sake of finding exoplanets.
But as Butkevich explained, there are other problems when it comes to this method. “The standard astrometric model is based on the assumption that stars move uniformly relative to the solar system barycentre,” he states. But as he goes on to explain, when examining the effects of Earth’s orbital motion on astrometric detection, there is a correlation between the Earth’s orbit and the position of a star relative to its system barycenter.
Kepler-22b, an exoplanet with an Earth-like radius that was discovery within the habitable zone of its host star. Credit: NASA
To put it another way, Dr. Butkevich examined whether or not the motion of our planet around the Sun, and the Sun’s motion around its center of mass, could have a cancelling effect on parallax measurements of other stars. This would effectively make any measurements of a star’s motion, designed to see if there were any planets orbiting it, effectively useless. Or as Dr. Butkevich stated in his study:
“It is clear from simple geometrical considerations that in such systems the orbital motion of the host star, under certain conditions, may be observationally close to the parallactic effect or even indistinguishable from it. It means that the orbital motion may be partially or fully absorbed by the parallax parameters.”
This would be especially true of systems where the orbital period of a planet was one year, and which had an orbit that placed it close to the Sun’s ecliptic – i.e. like Earth’s own orbit! So basically, astronomers would not be able to detect Earth 2.0 using astrometric measurements, because Earth’s own orbit and the Sun’s own wobble would make detection close to impossible.
As Dr. Butkevich states in his conclusions:
“We present an analysis of effects of the Earth orbital motion on astrometric detectability of exoplanetary systems. We demonstrated that, if period of a planet is close to one year and its orbital plane is nearly parallel to the ecliptic, orbital motion of the host may be entirely or partially absorbed by the parallax parameter. If full absorption occurs, the planet is astrometrically undetectable.”
Future surveys for exoplanets could be complicated by the Sun’s own motion around its barycenter. Credit: NASA
Luckily, exoplanet-hunters have a myriad of other methods too choose from, including direct and indirect measurements. And when it comes to spotting planets around neighboring stars, two of the most effective involve measuring Doppler shifts in stars (aka. the Radial Velocity Method) and dips in a star’s brightness (aka. the Transit Method).
Nevertheless, these methods suffer from their own share of drawbacks, and knowing their limitations is the first step in refining them. In that respect, Dr. Butkevich’s study has echoes of heliocentrism and relativity, where we are reminded that our own reference point is not fixed in space, and can influence our observations.
A new study indicates that in about a million years, a star will pass close to our Solar System, sending comets towards Earth and the other planets. Credit: NASA/JPL-Caltech
To our Solar System, “close-encounters” with other stars happen regularly – the last occurring some 70,000 years ago and the next likely to take place 240,000 to 470,000 years from now. While this might sound like a “few and far between” kind of thing, it is quite regular in cosmological terms. Understanding when these encounters will happen is also important since they are known to cause disturbances in theOort Cloud, sending comets towards Earth.
Thanks to a new study by Coryn Bailer-Jones, a researcher from the Max Planck Institute for Astronomy, astronomers now have refined estimates on when the next close-encounters will be happening. After consulting data from the ESA’s Gaia spacecraft, he concluded that over the course of the next 5 million years, that the Solar System can expect 16 close encounters, and one particularly close one!
Artist’s impression of the ESA’s Gaia spacecraft. Credit: ESA/ATG medialab; background: ESO/S. Brunier
As noted, these types of disturbances have happened many times throughout the history of the Solar System. In order to dislodge icy objects from their orbit in the Oort Cloud – which extends out to about 15 trillion km (100,000 AU) from our Sun – and send them hurling into the inner Solar System, it is estimated that a star would need to pass within 60 trillion km (37 trillion mi; 400,000 AU) of our Sun.
While these close encounters pose no real risk to our Solar System, they have been known to increase comet activity. As Dr. Bailer-Jones explained to Universe Today via email:
“Their potential influence is to shake up the Oort cloud of comets surrounding our Sun, which could result in some being pushed into the inner solar system where is chance they could impact with the Earth. But the long-term probability of one such comet hitting the Earth is probably lower than the probability the Earth is hit by a near-Earth asteroid. So they don’t pose much more danger.”
One of the goals of the Gaia mission, which launched back in 2013, was to collect precise data on stellar positions and motions over the course of its five-year mission. After 14 months in space, the first catalogue was released, which contained information on more than a billion stars. This catalogue also contained the distances and motions across the sky of over two million stars.
By combining this new data with existing information, Dr. Bailer-Jones was able to calculate the motions of some 300,000 stars relative to the Sun over a five million year period. As he explained:
“I traced the orbits of stars observed by Gaia (in the so-called TGAS catalogue) backwards and forwards in time, to see when and how close they would come to the Sun. I then computed the so-called ‘completeness function’ of TGAS to find out what fraction of encounters would have been missed by the survey: TGAS doesn’t see fainter stars (and the very brightest stars are also omitted at present, for technical reasons), but using a simple model of the Galaxy I can estimate how many stars it is missing. Combining this with the actual number of encounters found, I could estimate the total rate of stellar encounters (i.e. including the ones not actually seen). This is necessarily a rather rough estimate, as it involves a number of assumptions, not least the model for what is not seen.”
From this, he was able to come up with a general estimate of the rate of stellar encounters over the past 5 million years, and for the next 5 million. He determined that the overall rate is about 550 stars per million years coming within 150 trillion km, and about 20 coming closer than 30 trillion km. This works out to about one potential close encounter every 50,000 years or so.
Dr. Bailor-Jones also determined that of the 300,000 stars he observed, 97 of them would pass within 150 trillion km (93 trillion mi; 1 million AU) of our Solar System, while 16 would come within 60 trillion km. While this would be close enough to disturb the Oort Cloud, only one star would get particularly close. That star is Gliese 710, a K-type yellow dwarf located about 63 light years from Earth which is about half the size of our Sun.
Stars speeding through the Galaxy. Credit: ESA
According to Dr. Bailer-Jones’ study, this star will pass by our Solar System in 1.3 million years, and at a distance of just 2.3 trillion km (1.4 trillion mi; 16 ,000AU). This will place it well within the Oort Cloud, and will likely turn many icy planetesimals into long-period comets that could head towards Earth. What’s more, Gliese 710 has a relatively slow velocity compared to other stars in our galaxy.
Whereas the average relative velocity of stars is estimated to be around 100.000 km/h (62,000 mph) at their closest approach, Gliese 710 will will have a speed of 50,000 km/h (31,000 mph). As a result, the star will have plenty of time to exert its gravitational influence on the Oort Cloud, which could potentially send many, many comets towards Earth and the inner Solar System.
Over the past few decades, this star has been well-documented by astronomers, and they were already pretty certain that it would experience a close encounter with our Solar System in the future. However, previous calculations indicated that it would pass within 3.1 to 13.6 trillion km (1.9 to 8.45 trillion mi; 20,722 to 90,910 AU) from our star system – and with a 90% certainty. Thanks to this most recent study, these estimates have been refined to 1.5–3.2 trillion km, with 2.3 trillion km being the most likely.
Again, while it might sound like these passes are on too large of a timescale to be of concern, in terms of the astronomical history, its a regular occurrence. And while not every close encounter is guaranteed to send comets hurling our way, understanding when and how these encounters have happened is intrinsic to understanding the history and evolution of our Solar System.
Understanding when a close encounters might happen next is also vital. Assuming we are still around when another takes place, knowing when it is likely to happen could allow us to prepare for the worst – i.e. if a comets is set on a collision course with Earth! Failing that, humanity could use this information to prepare a scientific mission to study the comets that are sent our way.
The second release of Gaia data is scheduled for next April, and will contain information on an estimated 1 billion stars. That’s 20 times as many stars as the first catalogue, and about 1% the total number of stars within the Milky Way Galaxy. The second catalog will also include information on much more distant stars, will which allow for reconstructions of up to 25 million years into the past and future.
As Dr. Bailer-Jones indicated, the release of Gaia data has helped astronomers considerably. “[I]t greatly improves on what we had before, in both number of stars and precision,” he said. “But this is really just a taster of what will come in the second data release in April 2018, when we will provide parallaxes and proper motions for around one billion stars (500 times as many as in the first data release).”
With every new release, estimates on the movements of the galaxy’s stars (and the potential for close encounters) will be refined further. It will also help us to chart when major comet activity took place within the Solar System, and how this might have played a role in the evolution of the planets and life itself.
Molecular clouds scattered by an intermediate black hole show very wide velocity dispersion in this artist’s impression. This scenario well explains the observational features of a peculiar molecular cloud CO-0.40-0.22. Credit: Keio University
At the center of the Milky Way Galaxy resides the Supermassive Black Hole (SMBH) known as Sagittarius A*. This tremendous black hole measures an estimated 44 million km in diameter, and has the mass of over 4 million Suns. For decades, astronomers have understood that most larger galaxies have an SMBH at their core, and that these range from hundreds of thousands to billions of Solar Masses.
However, new research performed by a team of researchers from Keio University, Japan, has made a startling find. According to their study, the team found evidence of a mid-sized black hole in a gas cluster near the center of the Milky Way Galaxy. This unexpected find could offer clues as to how SMBHs form, which is something that astronomers have been puzzling over for some time.
This artist’s concept shows a galaxy with a supermassive black hole at its core. The black hole is shooting out jets of radio waves.Image credit: NASA/JPL-Caltech
This compact dust cloud, which has been a source of fascination to astronomers for years, measures over 1000 AU in diameter and is located about 200 light-years from the center of our galaxy. The reason for this interest has to do with the fact that gases in this cloud – which include hydrogen cyanide and carbon monoxide – move at vastly different speeds, which is something unusual for a cloud of interstellar gases.
In the hopes of better understanding this strange behavior, the team originally observed CO–0.40–0.22 using the 45-meter radio telescope at the Nobeyama Radio Observatory in Japan. This began in January of 2016, when the team noticed that the cloud had an elliptical shape that consisted of two components. These included a compact but low density component with varying velocities, and a dense component (10 light years long) with little variation.
After conducting their initial observations, the team then followed up with observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. These confirmed the structure of the cloud and the variations in speed that seemed to accord with density. In addition, they observed the presence of radio waves (similar to those generated by Sagittarius A*) next to the dense region. As they state in their study:
“Recently, we discovered a peculiar molecular cloud, CO–0.40–0.22, with an extremely broad velocity width, near the center of our Milky Way galaxy. Based on the careful analysis of gas kinematics, we concluded that a compact object with a mass of about 105 [Solar Masses] is lurking in this cloud.”
Change image showing the area around Sgr A*, where low, medium, and high-energy X-rays are red, green, and blue, respectively. The inset box shows X-ray flares from the region close to Sgr A*. NASA: NASA/SAO/CXC
The team also ran a series of computer models to account for these strange behaviors, which indicated that the most likely cause was a black hole. Given its mass – 100,000 Solar Masses, or roughly 500 times smaller than that of Sagittarius A* – this meant that the black hole was intermediate in size. If confirmed, this discovery will constitute the second-largest black hole to be discovered within the Milky Way.
This represents something of a first for astronomers, since the vast majority of black holes discovered to date have been either small or massive. Studies that have sought to locate Intermediate Black Holes (IMBHs), on the other hand, have found very little evidence of them. Moreover, these findings could account for how SMBHs form at the center of larger galaxies.
In the past, astronomers have conjectured that SMBHs are formed by the merger of smaller black holes, which implied the existence of intermediate ones. As such, the discovery of an IMBH would constitute the first piece of evidence for this hypothesis. As Brooke Simmons, a professor at the University of California in San Diego, explained in an interview with The Guardian:
“We know that smaller black holes form when some stars die, which makes them fairly common. We think some of those black holes are the seeds from which the much larger supermassive black holes grow to at least a million times more massive. That growth should happen in part by mergers with other black holes and in part by accretion of material from the part of the galaxy that surrounds the black hole.
“Astrophysicists have been collecting observational evidence for both stellar mass black holes and supermassive black holes for decades, but even though we think the largest ones grow from the smallest ones, we’ve never really had clear evidence for a black hole with a mass in between those extremes.”
Artist’s impression of two merging black holes, which has been theorized to be a source of gravitational waves. Credit: Bohn, Throwe, Hébert, Henriksson, Bunandar, Taylor, Scheel/SXS
Further studies will be needed to confirm the presence of an IMBH at the center of CO–0.40–0.22. Assuming they succeed, we can expect that astrophyiscists will be monitoring it for some time to determine how it formed, and what it’s ultimate fate will be. For instance, it is possible that it is slowly drifting towards Sagittarius A* and will eventually merge with it, thus creating an even more massive SMBH at the center of our galaxy!
Assuming human beings are around to detect that merger, its fair to say that it won’t go unnoticed. The gravitational waves alone are sure to be impressive!
A billion years after the big bang, hydrogen atoms were mysteriously torn apart into a soup of ions. Credit: NASA/ESA/A. Felid (STScI)).
In accordance with the Big Bang model of cosmology, shortly after the Universe came into being there was a period known as the “Dark Ages”. This occurred between 380,000 and 150 million years after the Big Bang, where most of the photons in the Universe were interacting with electrons and protons. As a result, the radiation of this period is undetectable by our current instruments – hence the name.
Astrophysicists and cosmologists have therefore been pondering how the Universe could go from being in this dark, cloudy state to one where it was filled with light. According to a new study by a team of researchers from the University of Iowa and the Harvard-Smithsonian Center for Astrophysics, it may be that black holes violently ejected matter from the early Universe, thus allowing light to escape.
Their study, titled “Resolving the X-ray emission from the Lyman continuum emitting galaxy Tol 1247-232“, recently appeared in the Monthly Notices of the Royal Astronomical Society. Led by Phillip Kaaret, a professor of Physics and Astronomy at the University of Iowa – and supported by an award from the Chandra X-ray Observatory – the research team arrived at this conclusion by observing a nearby galaxy from which ultraviolet light is escaping.
Milestones in the history of the Universe, from the Big Bang to the present day. Credit: NAOJ/NOAO
This galaxy, known as Tol 1247-232, is a small (and possibly elliptical) galaxy located 652 million light-years away, in the direction of the southern Hydra constellation. This galaxy is one of just nine in the local Universe (and one of only three galaxies close to the Milky Way) that has been shown to emit Lyman continuum photons – a type of radiation in the ultraviolet band.
Back in May of 2016, the team spotted a single X-ray source coming from a star-forming region in this galaxy, using the Chandra X-ray observatory. Based on their observations, they determined that it was not caused by the formation of a new star. For one, new stars do not experience sudden changes in brightness, as this x-ray source did. In addition, the radiation emitted by new stars does not come in the form of a point-like source.
Instead, they determined that what they were seeing had to be the result of a very small object, which left only one likely explanation: a black hole. As Philip Kaaret, a professor in the UI Department of Physics and Astronomy and the lead author on the study, explained:
“The observations show the presence of very bright X-ray sources that are likely accreting black holes. It’s possible the black hole is creating winds that help the ionizing radiation from the stars escape. Thus, black holes may have helped make the universe transparent.”
Artist concept of matter swirling around a black hole. Credit: NASA/Dana Berry/SkyWorks Digital
However, this also raised the question of how a black hole could be emitting matter. This is something that astrophysicists have puzzled over for quite some time. Whereas all black holes have tendency to consume all that is in their path, a small number of supermassive black holes (SMBHs) have been found to have high-speed jets of charged particles streaming from their cores.
These SMBHs are what power Active Galactic Nuclei, which are compact, bright regions that has been observed at the centers of particularly massive galaxies. At present, no one is certain how these SMBHs manage to fire off jets of hot matter. But it has been theorized that they could be caused by the accelerated rotational energy of the black holes themselves.
In keeping with this, the team considered the possibility that accreting X-ray sources could explain the escape of matter from a black hole. In other words, as a black hole’s intense gravity pulls matter inward, the black hole responds by spinning faster. As the hole’s gravitational pull increases, the speed creates energy, which inevitably causes charged particles to be pushed out. As Kaaret explained:
“As matter falls into a black hole, it starts to spin and the rapid rotation pushes some fraction of the matter out. They’re producing these strong winds that could be opening an escape route for ultraviolet light. That could be what happened with the early galaxies.”
Depiction of the tidal disruption event in F01004-2237. The release of gravitational energy as the debris of the star is accreted by the black hole leads to a flare in the optical light of the galaxy. Credit and copyright: Mark Garlick
Taking this a step further, the team hypothesized that this could be what was responsible for light escaping the “Dark Ages”. Much like the jets of hot material being emitted by SMBHs today, similarly massive black holes in the early Universe could have sped up due to the accretion of matter, spewing out light from the cloudiness and allowing for the Universe to become a clear, bright place.
In the future, the UI team plans to study Tol 1247-232 in more detail and locate other nearby galaxies that are also emitting ultraviolet light. This will corroborate their theory that black holes could be responsible for the observed point source of high-energy X-rays. Combined with studies of the earliest periods of the Universe, it could also validate the theory that the “Dark Ages” ended thanks to the presence of black holes.
In addition to all that, engineers at the Jet Propulsion Laboratory in Pasadena, California, are busy preparing the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) Lander for its scheduled launch in 2018. Once deployed to Mars, the lander will reveal things about Mars’ interior geology and composition, shedding new light on the history of the Red Planet’s formation and evolution.
Originally scheduled for launch in 2016, the lander’s deployment was delayed due to the failure of a key component – a chamber that housed the Seismic Experiment for Interior Structure (SEIS). Having finished work on a new vacuum enclosure for this instrument, the technicians at Lockheed Martin Space Systems are back at work, assembling and testing the spacecraft in a clean room facility outside of Denver, Colorado.
This artist’s concept from August 2015 depicts NASA’s InSight Mars lander fully deployed for studying the deep interior of Mars. Credit: NASA/JPL-Caltech
As Stu Spath, the spacecraft program manager at Lockheed Martin, said in a NASA press statement:
“Our team resumed system-level integration and test activities last month. The lander is completed and instruments have been integrated onto it so that we can complete the final spacecraft testing including acoustics, instrument deployments and thermal balance tests.”
Beyond the exploration of Mars, the InSight mission is also expected to reveal information about how all terrestrial (i.e. rocky) planets in the Solar System formed over four billion years ago. Mars is an especially opportune target for this type of research since it has been relatively inactive for the past three billion years. However, when the planet was still young, it underwent geological processes that were analogous to Earth’s.
In other words, because the interior of Mars has been subject to less convection over the past three billion years, it has likely preserved evidence about its early geological history better than Earth has. InSight will study this preserved history through a series of instruments that will measure the planet’s seismology, heat loss, and the state and nature of its core.
Once it reaches Mars, the stationary lander will set down near Mars’ equator and deploy its two fold-out solar cells, which kind of resemble large fans. Within a few weeks of making its landing, it will use a robotic arm to place its two main instruments onto the Martian surface – the aforementioned Seismic Experiment for Interior Structure (SEIS) and the Heat Flow and Physical Properties Probe (HP³).
Artist’s impression of the interior of Mars. Credit: NASA/JPL
The SEIS instrument – which was developed by France’s National Center for Space Studies (CNES) in collaboration with NASA and several European scientific institutions – has a sensitivity comparable to the best research seismometers here on Earth. This instrument will record seismic waves from “marsquakes” and meteor impacts, which will reveal things about the planet’s interior layers.
The HP³ probe, supplied by the German Aerospace Center (DLR), will use a Polish-made self-hammering mechanism to bury itself to a depth of 3 meters (10 feet) or more. As it descends, the probe will extend a tether that contains temperature sensors every ~10 cm, which measure the temperature profile of the subsurface. Combined with surface measurements, the instrument will determine the amount of heat escaping from the planet’s interior.
A third experiment, known as Rotation and Interior Structure Experiment (RISE), will also come into play. This instrument will use the lander’s X-band radio link to conduct Doppler tracking of the lander’s location, which will also allow it to measure variations in Mars’ rotation axis. Since these variations are primarily related to the size and state of Mars’ core, this experiment will shed light on one of Mars’ greatest mysteries.
Thanks to multiple missions that have studies Mars’ surface and atmosphere, scientists now know that roughly 4.2 billions of years ago, Mars lost its magnetic field. Because of this, Mars’ atmosphere was stripped away by solar wind during the next 500 million years. It is believed that it was this process that allowed the planet to go from being a warmer, wetter environment in the past to the cold, desiccated and irradiated place it is today.
NASA’s InSight Mars lander spacecraft in a Lockheed Martin clean room near Denver. Credit: NASA/JPL-Caltech/Lockheed Martin
As such, determining the state of Mars’ core – i.e. whether it is solid or liquid, or differentiated between a solid outer core and liquid inner core – will allow scientists to gain a more comprehensive understanding of the planet’s geological history. It will also allow them to answer with a fair degree of certainty how and when Mars lost its magnetic field (and hence, its denser, warmer atmosphere).
The spacecraft’s science payload is also on track for next year’s launch. At present, the mission is scheduled to launch on May 5th, 2018, though this window could be moved to anytime within a five-week period. Regardless of what day it launches, mission planners indicate that the flight will reach Mars on November 26th, 2018 (the Monday after Thanksgiving).
As noted, the mission was originally planned to launch in March of 2016, but was canceled due to the presence of a leak in the special metal container designed to maintain near-vacuum conditions around the SEIS’s main sensors. Now that a redesigned vacuum vessel has been built and tested (and integrated with the SEIS) the spacecraft is ready for its new launch date.
Back in 2010, the InSight mission was selected from a total of 28 proposals, which were made as part of the twelfth round of selections for NASA’s Discovery Program. In contrast to New Frontiers or Flagship programs, Discovery missions are small-budget enterprises that aid in larger scientific pursuits. Along with two other finalists – the Titan Mare Explorer (TiME) and the Comet Hopper (CHopper) – InSight was awarded funding for further development.
Bruce Banerdt of NASA’s Jet Propulsion Laboratory is the Principle Investigator (PI) for the InSight mission.
Be sure to check out this video of the InSight mission (courtesy of NASA JPL) as well:
Artist's impression of how the surface of a planet orbiting a red dwarf star may appear. The planet is in the habitable zone so liquid water exists. However, low levels of ultraviolet radiation from the star have prevented or severely impeded chemical processes thought to be required for life to emerge. This causes the planet to be devoid of life. Credit: M. Weiss/CfA
Ultraviolet light is what you might call a controversial type of radiation. On the one hand, overexposure can lead to sunburn, an increased risk of skin cancer, and damage to a person’s eyesight and immune system. On the other hand, it also has some tremendous health benefits, which includes promoting stress relief and stimulating the body’s natural production of vitamin D, seratonin, and melanin.
And according to a new study from a team from Harvard University and the Harvard-Smithsonian Center for Astrophysics (CfA), ultraviolet radiation may even have played a critical role in the emergence of life here on Earth. As such, determining how much UV radiation is produced by other types of stars could be one of the keys to finding evidence of life any planets that orbit them.
Artist’s impression of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri. The double star Alpha Centauri AB is visible to the upper right of Proxima itself. Credit: ESO
Recent studies have indicated that UV radiation may be necessary for the formation of ribonucleic acid (RNA), which is necessary for all forms of life as we know it. And given the rate at which rocky planets have been discovered around red dwarf stars of late (exampled include Proxima b, LHS 1140b, and the seven planets of the TRAPPIST-1 system), how much UV radiation red dwarfs give off could be central to determining exoplanet habitability.
“It would be like having a pile of wood and kindling and wanting to light a fire, but not having a match. Our research shows that the right amount of UV light might be one of the matches that gets life as we know it to ignite.”
For the sake of their study, the team created radiative transfer models of red dwarf stars. They then sought to determine if the UV environment on prebiotic Earth-analog planets which orbited them would be sufficient to stimulate the photoprocesses that would lead to the formation of RNA. From this, they calculated that planets orbiting M-dwarf stars would have access to 100–1000 times less bioactive UV radiation than a young Earth.
As a result, the chemistry that depends on UV light to turn chemical elements and prebiotic conditions into biological organisms would likely shut down. Alternately, the team estimated that even if this chemistry was able to proceed under a diminished level of UV radiation, it would operate at a much slower rate than it did on Earth billions of years ago.
Artist’s impression of the planet orbiting a red dwarf star. Credit: ESO/M. Kornmesser
As Robin Wordsworth – an assistant professor at the Harvard School of Engineering and Applied Science and a co-author on the study – explained, this is not necessarily bad news as far as questions of habitability go. “It may be a matter of finding the sweet spot,” he said. “There needs to be enough ultraviolet light to trigger the formation of life, but not so much that it erodes and removes the planet’s atmosphere.”
Previous studies have shown that even calm red dwarfs experience dramatic flares that periodically bombard their planets with bursts UV energy. While this was considered to be something hazardous, which could strip orbiting planets of their atmospheres and irradiate life, it is possible that such flares could compensate for the lower levels of UV being steadily produced by the star.
This news also comes on the heels of a study that indicated how the outer planets of the TRAPPIST-1 system (including the three located within its habitable zone) might still have plenty of water of their surfaces. Here too, the key was UV radiation, where the team responsible for the study monitored the TRAPPIST-1 planets for signs of hydrogen loss from their atmospheres (a sign of photodissociation).
This research also calls to mind a recent study led by Professor Avi Loeb, the Chair of the astronomy department at Harvard University, Director of the Institute for Theory and Computation, and also a member of the CfA. Titled, “Relative Likelihood for Life as a Function of Cosmic Time“, Loeb and his team concluded that red dwarf stars are the most likely to give rise to life because of their low mass and extreme longevity.
Artist’s impression of a sunset seen from the surface of an Earth-like exoplanet. Credit: ESO/L. Calçada
Compared to higher-mass stars that have shorter life spans, red dwarf stars are likely to remain in their main sequence for as long as six to twelve trillion years. Hence, red dwarf stars would certainly be around long enough to accommodate even a vastly decelerated rate of organic evolution. In this respect, this latest study might even be considered a possible resolution for the Fermi Paradox – Where are all the aliens? They’re still evolving!
But as Dimitar Sasselov – the Phillips Professor of Astronomy at Harvard, the Director of the Origins of Life Initiative and a co-author on the paper – indicated, there are still many unanswered questions:
“We still have a lot of work to do in the laboratory and elsewhere to determine how factors, including UV, play into the question of life. Also, we need to determine whether life can form at much lower UV levels than we experience here on Earth.”
As always, scientists are forced to work with a limited frame of reference when it comes to assessing the habitability of other planets. To our knowledge, life exists on only on planet (i.e. Earth), which naturally influences our understanding of where and under what conditions life can thrive. And despite ongoing research, the question of how life emerged on Earth is still something of a mystery.
If life should be found on a planet orbiting a red dwarf, or in extreme environments we thought were uninhabitable, it would suggest that life can emerge and evolve in conditions that are very different from those of Earth. In the coming years, next-generation missions like the James Webb Space Telescope are the Giant Magellan Telescope are expected to reveal more about distant stars and their systems of planets.
The payoff of this research is likely to include new insights into where life can emerge and the conditions under which it can thrive.
