40 New Understandings in (Astro)Physics Since Archon 39

Solar Systems


1. The MESSENGER probe orbiting Mercury recently had its altitude lowered allowing for better resolution of surface features. One of the things they were surprised to discover was thrust fault scarps. These features are created as one landmass slides up and over another one creating cliff like ridges. Such features were expected to be worn down relatively quickly on solar system timescales by meteorite bombardment. Their presence indicates that Mercury is still tectonically active. This continued tectonic activity is likely caused by Mercury shrinking as its core continues to cool and the planet contracts. - Planetary Science Institute, Sept 26, 2016

2. The JUNO spacecraft has arrived at Jupiter and recently released the first images of Jupiter’s north pole. And they’re weird. Instead of the creamy colors near Jupiter’s equatorial region, Jupiter’s pole is dominated by blue hues. Also missing are the long bands which are instead replaced by relatively small scale storms. Additionally, some of the clouds cast shadows giving the first indications of relative altitude. - NASA, Sept 2, 2016

Dwarf Planets, Moons, & Minor Bodies

3. The most geologically active body in the solar system is Io, one of Jupiter’s 4 largest moons which has continuous active volcanism triggered by the gravitational perturbations as it orbits the massive planet. These volcanoes give Io a tenuous atmosphere. There has long been speculation as to what the effects of Io passing into Jupiter’s shadow does to this atmosphere but research published this year has shown that Io’s atmosphere partially collapses. In particular, the temperature drop when Io is shaded from the Sun causes the sulfur dioxide to freeze and fall to the surface as the temperature drops from -235 to -270º F. When it reenters the sunlight, it sublimates and turns back into gas. - Journal of Geophysical Research - Planets, Aug 2, 2016

4. In 1597 a governor of a northern province in Argentina mounted an expedition to locate a large source of iron that natives used as weapons, that had reportedly fallen from the sky. This was the Campo del Cielo meteorite which crashed to earth some 4-5,000 years ago in numerous pieces. The original meteor was estimated to be over 600 tons before it broke up. The largest piece previously found was 66 tons, but in September of this year, the second largest piece was discovered weighing in at 30 tons. - Universe Today, Sept 15, 2016

5a. Pluto has a large, flat, heart shaped region dubbed the Sputnik Planum, 1,000km across. This region is covered with volatile nitrogen and CO2 ice and is devoid of craters indicating that the region is geologically active, likely having been resurfaced in the past 10 million years.

5b. A pair of large mounds with central depressions were discovered. They bear a strong resemblance to dome volcanoes and as such, astronomers are expecting that they are ice volcanoes.

5c. Pluto has an atmosphere. It’s comprised mostly of N2, CO, and methane. Clouds were discovered to be present as well. The surface pressure is about 10 microbars or 100,000 times less than Earth’s atmospheric pressure at the surface. When viewed the the back, it was discovered to scatter blue light. - arXiv, Oct 26, 2015

5d. X-Rays are high energy photons and as such, generally come from hot or energetic sources. The last place astronomers expect to find them is in the cold outer reaches of our solar system. But this July, astronomers detected them coming from Pluto indicating that it is interacting with the solar wind in an unexpected way. - Science Direct, July 27, 2016

6. Discovered in 1801 was another once-planet that got demoted nearly 150 years before Pluto. This was Ceres which orbits between Mars and Jupiter. The dwarf planet recently got a visit from NASA’s Dawn mission which discovered fresh impact craters on the surface with unusually bright spots. These spots are believed to be salt deposits that were brought to the surface during the impact, likely originally as a brine solution wherein the water evaporated leaving just the salt deposits. - NASA, December 2015

7. Makemake is one of the largest known dwarf planets in the Kuiper belt, first discovered in 2005. But this year, it was discovered that it had a dark moon orbiting it that previously avoided detection due to its low surface brightness making it get lost in the glare from the larger body. - ApJ Letters, Apr 27, 2016

8a. Although many molecules containing carbon, nitrogen, and oxygen, collectively known as organic compounds, have long been detected in the gas and dust of the interstellar medium, finding many of the more complex molecules necessary for the foundation of life has proven elusive outside our planet. In May of 2016, scientists in charge of the Rosetta mission to comet 67P/Churyumov-Gerasimenko discovered the amino acid glycine in the atmosphere of this comet. - Scientific Advances, May 6, 2016

8b. As an additional note, this comet was the first to have a lander put on it. The lander’s name was Philae. However, the lander’s communication was disrupted leading to speculation that it had fallen in a canyon. The orbiting satellite, Rosetta, located the lander tipped over near a cliff face.

9. Comets have long been known to be repositories of complex molecules but in October 2015, astronomers announced that they had made the first discovery of ethyl alcohol and a sugar (glycolaldehyde) on one. In particular, it was comet Lovejoy which swings around every 8,000 years. Astronomers determined the comet releases as much alcohol as nearly 5,000 bottles of wine every second during its peak activity. - NASA, Oct 23, 2015

10. In investigating gravitational perturbations of numerous small bodies in the outer solar system, astronomers have inferred the presence of a 9th full fledged planet with an estimated mass approximately 10 times that of Earth. Further research has speculated that this planet, if present may have been stolen from another solar system. - ApJ, Jan 20, 2016 & MNRAS, Apr 19, 2016

11. In September 2015, astronomers discovered a slowly moving object at the distant edge of our solar system. Follow up observations determined it was a new minor planet in an highly elliptical orbit whose orbit takes it 120 times as far from the Sun as Earth and has an orbit over 700 years long. In July of this year, it was given the temporary designation of 2015 RR245 by the IAU. - International Astronomical Union, July 11, 2016

12. Astronomers keep discovering distant objects in our own solar system and in October 2015, a new record for most distant was set when V774104 was discovered at a distance approximately 103 AU, 3 times further from the Sun than Pluto. The object is quite small, only 500-1,000 km in diameter. - Space, Nov 12, 2015


13. Astronomers announced this year that the first evidence of a planet in another solar system may have been recorded as early as 1917. The suggestion comes from a spectra of van Maanen’s star recorded nearly 100 years ago. The spectra clearly shows the presence of calcium, iron, and magnesium which are not typically present in white dwarfs like van Maanen’s star since they are heavy and would sink into the star whereas the spectra only reveals the surface composition. The explanation is that a large body with high concentrations of these elements must have recently fallen into the star and polluted its spectrum. In this image, the spectrum of van Maanen’s star is the thin line between the two thicker ones which are reference spectra. - Carnegie Science, Apr 12, 2016

14. The KEPLER Space Telescope searches for planets by staring at a large swath of the constellation Cygnus and observing thousands of stars simultaneously, waiting for planets to pass directly in front of their stars causing a partial eclipse and dimming the star’s light. KEPLER has been hugely successful and in May of 2016, it announced the largest haul of planets yet with 1,284. - ApJ, May 10, 2016

15. Disks of gas and dust are known around several stars. One of them, TW Hydrae is relatively close to Earth and has its disk oriented face on. In September of 2016, astronomers have discovered that the disk has a ring missing from it which they interpreted as the site of formation of a planet. Based on the amount of material that’s missing and the distance from the star, they estimate that it would form into an icy gas giant similar to Neptune. - ApJ Letters, Sept 1, 2016

16. Earth size planet found in habitable zone around Proxima Centauri, the closest star to Earth. Proxima Centauri is part of a trinary star system which also includes alpha centauri A & B. Proxima is a red dwarf star with about 12% the mass of the Sun. The newly discovered planet has a mass approximately 1.3 Earth masses and orbits its parent star once every ~11.2 days at a distance of 0.05 AU. For comparison, Mercury orbits the Sun at a distance of .387 AU. Discovered via radial velocity measurements. - European Space Agency, July 13, 2016

17. Astronomers discovered a planet in a triple star system HD131399. The star system is comprised of a pair of closer binary stars (~9 AU separation) with a third, more massive and brighter star orbiting more distantly at about 300 AU. The newly discovered planet orbits the more distant star and has an estimated mass of approximately 4 times the mass of Jupiter with an orbit of ~550 years. The star system is relatively young, only ~16 million years and shows no IR excess indicating any dust from the primordial disk from which the planet was formed has been cleared out. This quick formation and unusual orbit, which is tenuously stable, provides challenges to explain. - Science, August 12, 2016

18. In 2009, astronomers discovered a faint brown dwarf star and a planetary mass L brown dwarf (not massive enough to undergo fusion; a failed star). In January 2016 astronomers announced that the two are likely gravitationally bound at a separation of of 6,900 AU making it the largest solar system yet discovered. The announcement came after astronomers realized that the two are the same distance and moving together. Due to the separation, it is unlikely that these stars formed together from a single disc. Rather, the astronomers speculate that the L dwarf was captured later. - MNRAS, Jan 22, 2016

19. A team of astronomers from MIT has discovered a system of potentially habitable planets relatively nearby: only 40 light years away. The system orbits a low mass ultra-cool dwarf star and has three known planets. The two innermost orbit the parent star in only 1.5 and 2.4 days. Although this puts them in extremely tight orbits, the low temperature of the star means that they only get 4 and 2 times the amount of radiation earth does respectively. The planets are expected to be tidally locked meaning one side of each is likely too hot with the other too cold. However, a band of relatively pleasant temperatures may exist near the terminator. A third planet in the system has an as of yet unknown period between 4 and 74 days. The mass of the planets has not yet been constrained. - ESO, May 2016

20. Since the detection of extrasolar planets has become commonplace, astronomers have been working to try to characterize their atmospheres by examining the spectra of the light as it passes through the planet’s atmosphere when it passes directly in front of the star. This has been successful on large, close-in “super Jupiters” whose large atmospheres are puffed up due to the temperatures, but in February 2016 astronomers announced the first transmission spectrum of a super-earth planet. The planet in question is 55 Cancri e. The atmosphere is mostly hydrogen and helium and is surprising because it sits in a very tight orbit lasting only 18 hours and these lighter elements could boil off. Additionally, the spectra revealed the presence of hydrogen cyanide indicating a higher than anticipated carbon to oxygen ratio. - ApJ, February 2016

Stellear and Interstellar Astronomy

21. The Big Bang created a universe filled with hydrogen, helium, and a tiny bit of lithium. The rest of the elements were cooked up in the cores of stars and supernovae which have continually enriched the interstellar medium. As new stars formed from the polluted material, the amount of heavy elements increased. Our sun is a 3rd generation star. But astronomers continually search for stars with less and less heavy elements from that first generation of stars. The largest ones which shine the brightest are long since gone, but low mass stars live for billions of years ad should still be around. However these stars are faint which makes finding them a challenge. In January of 2016, astronomers announced that they discovered a new ultra metal poor star and that it was the brightest yet discovered with an absolute visual luminosity of mag 11.9. The image shown displays the spectra of the newly discovered star (bottom) in comparison to two other ultra metal poor stars. - Astronomy & Astrophysics, Jan 2016

22. Stellar evolution is generally a long process. As stars approach death, cycles of core fusion become more and more rapid. But for the first time a star, SAO 244567, which was previously cooling, has suddenly started becoming hotter indicating that a new cycle of fusion has begun occurring in the core. - MNRAS, July 15, 2016

23. WISE 0855, a brown dwarf (failed star) discovered in 2014 was suspected of having water vapor clouds in its atmosphere due to its uncommonly low temperature, -9º F. Follow up observations have confirmed that this is the case and that the brown dwarf has a composition very similar to Jupiter which also has water vapor clouds. Additionally, other molecules in both of their atmospheres indicate that the objects are not in thermodynamic equilibrium and undergo turbulent mixing which dredge up molecules that would otherwise not be found in their atmospheres and are only stable on long timescales near the cores. - ApJ Letters, May 16, 2016

24. Chemistry does not seem to fundamentally have a preference for the geometry of its molecules being right handed or left handed (known as chirality). However, by the time life took hold, it seemed to have developed an affinity for one type over another. While molecules that can display chirality have been found in meteorites, the first interstellar detection of a molecule that has the potential for chirality was discovered spectroscopically in the Sagittarius B2 star forming region. Although the study has not yet determined if there is an imbalance in the chirality of these molecules, further studies with polarized light may be able to determine if the imbalance is inherent in nascent solar systems or was created later. - Science, June 17, 2016

25.Supernovae are already some of the most luminous events in the universe in which one star is briefly able to outshine the rest of the stars in the galaxy. However, in 2015 a super supernova occurred. In Jan of 2016, astronomers announced that this supernova, ASASSN-15lh, was twice as bright as the next brightest one yet discovered. The spectrum of this supernova was uncommonly featureless. Most supernovae show absorption lines in their spectra, with the features present being indicative of how energetic the event was. The lack of absorption features in the spectra speaks to how powerful the event was, as it would have fully ionized any atoms present in its atmosphere, disallowing the atomic transitions that create spectral lines in the first place. - Science, Jan 15, 2016

26. Although KEPLER’s main mission is to search for planets, a side effect is that this telescope also captures many other astronomically interesting events. In 2011, KEPLER discovered a supernova, KSN2011a. However, because KEPLER takes images so frequently, scientists realized that they caught the initial shockwave hitting the surface of the star when they processed the data, announced in March of 2016 marking the first time that this moment has ever been caught “on film”. - ApJ, Mar 17, 2016

27. Type Ia supernovae are thought to occur when a red giant star begins spilling mass onto a binary white dwarf companion with mass just below the critical threshold needed to collapse into a supernova (known as the Chandrasekhar limit). This regular mass threshold explains why type Ia supernova always shine with nearly the exact same absolute brightness. However, due to the remote nature of these events, astronomers have never been able to detect the hypothetical companion star. But in March 2016 a paper published in the Astrophysical Journal gave the first evidence of the companion as a supernova was caught early enough in the process that astronomers noticed a distinct “flash”. This flash has been interpreted as the shockwave of the supernova impacting the companion star and causing it to glow more brightly. - ApJ, March 2016

28. Fortunately, the black hole in our own galaxy is pretty quiet at present. There’s not much matter feeding into it to so we barely get more than a sputter of high energy radiation out of it. However, new research has suggested that 6 million years ago our SMBH was much more active. This was discovered when astronomers inspected a fog of super hot gas that permeates our galaxy. Although this gas is diffuse, its temperature is a million degrees and can be tracked due to how it absorbs X-rays from more distant sources. The astronomers discovered that the central region of our galaxy had a nearly 20,000 light year wide bubble where none of this gas was present. The amount of energy required to move an estimated 130 billion solar masses of material could only be explained by an active SMBH. By tracing the speed of the expanding bubble and running it backwards, they estimated that the event that last fed the SMBH was some 6 million years ago. This may also explain the origin of numerous young stars in that region of the galaxy which are approximately that age as well and whose initial gravitational collapse from the interstellar medium was triggered by this shockwave. - ApJ, Aug 29, 2016

29. Pulsars are the cores of stars that have gone supernova. The implosion creates a super dense star, often rapidly rotating with very strong magnetic fields. These magnetic fields can focus beams of radiation outwards that spin with the rotating star like a lighthouse. Since supernovae are fairly rare and being along the line of sight for the beam is as well, finding pulsars is quite uncommon but astronomers announced in December 2015 that they found one for the first time in our nearest large galactic neighbor, the Andromeda galaxy. This pulsar spins once every 1.2 second. - MNRAS, Dec 2015

30. Stars that venture too near a black hole can be ripped apart by gravitational forces. In 2015, astronomers announced that not only had they caught this process in action, but that the shredded star’s material was being blown away due to the heat generated in the accretion disk. - arXiv, Oct 23, 2016

Galactic Astronomy

31. In looking for new galaxies, astronomers at Yale discovered 47 new galaxies that were as large in diameter as our own Milky Way, but with only a few percent of the number of stars. Such diffuse galaxies could not be held together by the gravity of their stars alone which implies that these galaxies are comprised of almost entirely Dark Matter. Dubbed Ultra Diffuse Galaxies, the most unusual, named Dragonfly 44, is estimated to be be comprised of 99.99% of Dark Matter. - ApJ Letters, July 15, 2016

32a. Fast radio bursts were discovered in 2007 and, as their name suggests, are bright flashes in the radio part of the spectrum. Astronomers suspected that they were likely due to energetic events in the distant universe but they were so fast, astronomers were unable to pin them down. However, in November of 2015, astronomers announced that they had caught one fast enough to detect the afterglow and tied the burst to a particular galaxy 5 billion light years away, establishing that they are indeed products of a more distant universe. - Nature, December 2016 (arXiv Preprint)

32b. Due to how energetic these fast radio bursts are to be seen over such great distances astronomers have speculated they must be due to one off cataclysmic events. However, astronomers announced in March of 2016 that they discovered the first repeating FRB. This indicates that at least a subset of FRBs are due to other energetic phenomena, such as flaring Active Galactic Nuclei or a pulsar. - ApJ, Mar 29, 2016

33. Hubble again broke the record for the most distant known galaxy, this time finding one at a distance of approximately 13.3 billion light years, indicating this galaxy was already formed 400 million years after the Big Bang. Indications from Hubble and SPITZER indicate that the galaxy is only a fraction of the Milky Way’s size: about 1/25th, but was forming new stars at a rate more than 20 times what our own galaxy does. This would include many of the bright and massive O type stars which are short lived, which is what makes this galaxy sufficiently luminous for Hubble to have detected. - ApJ, March 3, 2016

34. The record for most distant cluster of galaxies viewed in the X-Ray was also set in 2016 when the Chandra telescope discovered a cluster of 11 massive galaxies at a distance of 11.1 billion light years. This pushes back the record by some 700 million years and is important because the current picture of galaxy cluster formation is one of hierarchical building in which individual galaxies form first and then begin to cluster and collide and understanding when and how this occurred gives insight to how galaxies and the universe evolved. Of these 11 galaxies, 9 of them are undergoing large amounts of star formation, creating an estimated an estimated 3,000 stars every year. - ApJ, Aug 31, 2016

35. NGC 253, also known as the Sculptor or Silver Dollar galaxy has long been known to be involved in some sort of intergalactic interaction with a smaller galaxy due to perturbations to its disk. However, astronomers have long been unable to find the culprit. But an Australian astronomer using a 12” amateur telescope noticed a faint smudge on an image he took of the galaxy. His team then followed up with a 30” telescope and confirmed the smudge was not the result of a reflection but were not able to determine its nature. Finally, the team used the Subaru telescope on Mt Maunakea in Hawaii and were able to resolve individual stars confirming it was the missing dwarf galaxy. It had previously gone undetected because of its low surface brightness as it is extremely spread out and elongated from tidal disruptions from the larger galaxy. - MNRAS, Feb 2016


36. In 2000, astronomers discovered the first of a series of objects known as Lyman Alpha Blobs (LABs). These objects are gigantic clouds of diffuse hydrogen gas, several times larger than galaxies, softly glowing in ultraviolet light. Astronomers have been puzzled as to what makes them glow. But in September of this year, astronomers announced that using a collection of the world’s largest telescopes, they had discovered a nest of galaxies at the LABs’ core. These young galaxies were undergoing massive amounts of star formation whose energy was pouring into the cloud of gas surrounding the galaxies illuminating it. - ESO, Sept 2016

37. Quasars are some of the brightest objects in the universe. They are the supermassive black holes at the centers of galaxies whose massive magnetic fields eject material from the accretion disk at nearly the speed of light. These monsters were more common in the early universe when the universe was denser and galactic interactions more common. But because of their brightness, they are visible from great distances allowing them to provide information about these early epochs. However, because they are only visible from a narrow angle along the jet, very few are known. However, a recent survey announced 63 new ones. - ApJ Supplement, Aug 10, 2016

38. Although Einstein’s theories of relativity have been robustly supported with observational evidence, many implications are still being tested 100 years later. The most recent among them was the detection of gravitational waves. The Laser Interferometry Gravitational-Wave Observatory (LIGO) made the first confirmed detection of them in Feb 2016 followed by a second observation in June. - LIGO, Feb 11, 2016 & LIGO, June 15, 2016

39. A new study has reduced the uncertainty in the Hubble Constant, a key variable in determining the rate of expansion and age of the universe, reducing the uncertainty from 3.3 to 2.4%. The study was done by using newly discovered Cepheid variable stars in the host galaxies of numerous type Ia supernovae. The Cepheid variables pulsate in a manner directly correlated with their absolute brightness making them “standard candles” by which astronomers can compare their true brightness with their apparent. By reducing the uncertainty in the distance to the type Ia supernovae, which can also be used as standard candles, astronomers were able to refine the Hubble constant to 73.24 ± 1.74 km s^-1 mpc^-1. This is significantly different than the value determined by measuring the acoustic variations in the CMB which is 66.93 ± 0.62 km s^-1 mpc^-1. While this discrepancy doesn’t imply that the models are wrong, it may hint at a systematic error in one method, or may hint at variations to the standard model of cosmology, or imply new fundamental physics. - ApJ, Apr 5, 2016

40. In early 2015, Russian astronomers noticed a 2 second burst in the radio part of the spectrum that appeared to be coming from the star HD 164595. This gained significant media coverage in 2016 when SETI began investigating the signal. However, followup observations from SETI failed to detect the signal and the conclusion is that this was likely terrestrial interference. The most likely candidate is a military satellite passing overhead of the observatory since the radio frequency in question is known to be a band used by the military. - SETI, September 2016