Stars/Solar systems

The solar system usually refers to the Sun system. However, solar systems may be associated with debris disks, protoplanetary disks, or planetary systems around stars or substellar objects.

Planets around other stars may be referred to as exoplanets, extrasolar planets, or circumstellar objects. Depending upon the situation in which an object is discovered, it may be labelled a sub-brown dwarf.

"The NASA/ESA Hubble Space Telescope has been at the cutting edge of research into what happens to stars like our Sun at the ends of their lives ... One stage that stars pass through as they run out of nuclear fuel is the preplanetary, or protoplanetary nebula. This Hubble image [at right] of the Egg Nebula shows one of the best views to date of this brief but dramatic phase in a star’s life."

HR 8799
The image at the right "shows the light from three planets orbiting a star 120 light-years away. The planets' star, called HR8799, is located at the spot marked with an "X.""

"This picture was taken using a small, 1.5-meter (4.9-foot) portion of the Palomar Observatory's Hale Telescope, north of San Diego, Calif. This is the first time a picture of planets beyond our solar system has been captured using a telescope with a modest-sized mirror -- previous images were taken using larger telescopes."

"The three planets, called HR8799b, c and d, are thought to be gas giants like Jupiter, but more massive. They orbit their host star at roughly 24, 38 and 68 times the distance between our Earth and sun, respectively (Jupiter resides at about 5 times the Earth-sun distance)."

Systems
"This composite image [at the right] shows an exoplanet (the red spot on the lower left), orbiting the brown dwarf 2M1207 (centre). 2M1207b is the first exoplanet directly imaged and the first discovered orbiting a brown dwarf. It was imaged the first time by the VLT in 2004. Its planetary identity and characteristics were confirmed after one year of observations in 2005. 2M1207b is a Jupiter-like planet, 5 times more massive than Jupiter. It orbits the brown dwarf at a distance 55 times larger than the Earth to the Sun, nearly twice as far as Neptune is from the Sun. The system 2M1207 lies at a distance of 230 light-years, in the constellation of Hydra. The photo is based on three near-infrared exposures (in the H [1.66 μm], K [2.18 μm] and L [3.8 μm] wavebands) with the NACO adaptive-optics facility at the 8.2-m VLT Yepun telescope at the ESO Paranal Observatory."

Planetary sciences
"High-contrast near-infrared imaging [at the right] of the nearby star HR 8799 has shown three giant planets1. Such images were possible because of the wide orbits (>25 astronomical units, where 1 AU is the Earth–Sun distance) and youth (<100 Myr) of the imaged planets, which are still hot and bright as they radiate away gravitational energy acquired during their formation."

"The system, with this additional planet, represents a challenge for current planet formation models as none of them can explain the in situ formation of all four planets."

"Besides having four giant planets, both systems also contain two 'debris belts' composed of small rocky or icy objects, along with lots of tiny dust particles."

"This is the fourth imaged planet in this planetary system, and only a tiny percentage of known exoplanets (planets outside our solar system) have been imaged; none has been imaged in multiple-planet systems other than those of HR 8799."

"We reached a milestone in the search for other worlds in 2008 with the discovery of the HR 8799 planetary system. The images of this new inner planet are the culmination of 10 years' worth of innovation, making steady progress to optimize every aspect of observation and analysis. This allows us to detect planets located ever closer to their stars and ever further from our own solar system."

"The four massive planets pull on each other gravitationally. We don't yet know if the system will last for billions of years or fall apart in a few million more. As astronomers carefully follow the HR 8799 planets during the coming decades, the question of the stability of their orbits could become much clearer."

"There's no simple model that can form all four planets at their current location. It's going to be a challenge for our theoretical colleagues."

"It is entirely plausible that this planetary system contains additional planets closer to the star than these four planets, quite possibly rocky, Earth-like planets. But such interior planets are far more difficult to detect."

"Images like these bring the exoplanet field, which studies planets outside our solar system, into an era of exoplanet characterization. Astronomers can now directly examine the atmospheric properties of four giant exoplanets that are all the same young age and that formed from the same building materials."

Colors
"This image [at right] shows two young brown dwarfs, objects that fall somewhere between planets and stars in terms of their temperature and mass. Brown dwarfs are cooler and less massive than stars, never igniting the nuclear fires that power their larger cousins, yet they are more massive (and normally warmer) than planets. When brown dwarfs are born, they heat the nearby gas and dust, which enables powerful infrared telescopes like NASA's Spitzer Space Telescope to detect their presence."

"Here we see a long sought-after view of these very young objects, labeled as A and B, which appear as closely-spaced purple-blue and orange-white dots at the very center of this image. The surrounding envelope of cool dust surrounding this nursery can be seen in purple."

"These twins, which were found in the region of the Taurus-Auriga star-formation complex, are the youngest of their kind ever detected. They are also helping astronomers solve a long-standing riddle about how brown dwarfs are formed more like stars or more like planets? Based on these findings, the researchers think they have found the answer: Brown dwarfs form like stars."

"This image combined data from three different telescopes on the ground and in space. Near-infrared observations collected at the Calar Alto Observatory in Spain cover wavelengths of 1.3 and 2.2 microns (rendered as blue). Spitzer's infrared array camera contributed the 4.5-micron (green) and 8.0-micron (yellow) observations, and its multiband imaging photometer added the 24-micron (red) component. The Caltech Submillimeter Observatory in Hawaii made the far-infrared observations at 350 microns (purple)."

Minerals
"Both models [for the four HR 8799 planets] with 1) physically thick forsterite clouds and a 60-μm modal particle size and 2) clouds made of 1 μm-sized pure iron droplets and 1% supersaturation fit the data."

Theoretical solar systems
Def. the "Sun and all the heavenly bodies that orbit around it, including the eight planets, their moons, the asteroids and comets" is called the Solar System.

Def. any "collection of heavenly bodies including a star or binary star, and any lighter stars, brown dwarfs, planets, and other objects in orbit" is called a solar system.

Usage notes
 * "As Sol is the name of our star, this phrase is usually used to refer specifically to our own sun and planets (the Sol system), in which case it is used with the and generally capitalised (as the Solar system or the Solar System). Other systems are then known as star systems or planetary systems, or specified by the name of the individual star (the Alpha Centauri system)."

Planets "of the Solar System [are] Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune".

Dwarf "planets of the Solar System [are] Ceres, Orcus, Pluto, Salacia, Varuna, Haumea, Quaoar, Makemake, 2007 OR10, Eris, Sedna".

Entities
"Extrasolar-planet searches that target very low-mass stars and brown dwarfs are hampered by intrinsic or instrumental limitations. Time series of astrometric measurements with precisions better than one milli-arcsecond can yield new evidence on the planet occurrence around these objects."

"Over a time-span of two years, we obtained I-band images of the target fields with the FORS2 camera at the Very Large Telescope. Using background stars as references, we monitored the targets’ astrometric trajectories, which allowed us to measure parallax and proper motions, set limits on the presence of planets, and to discover the orbital motions of two binary systems."

"We determined trigonometric parallaxes with an average accuracy of 0.09 mas (≃0.2 %), which resulted in a reference sample for the study of ultracool dwarfs at the M/L transition, whose members are located at distances of 9.5–40 pc."

Astrometric "observations with an accuracy of 120 µas over two years are feasible from the ground and can be used for a planet-search survey."

The image at right is "of DE1520-44 in 0.47" seeing showing the primary (A), its companion (B), and the faint background object (x)."

Objects
The "presence of a protoplanetary disk" may be used to estimate a stars age.

"The preplanetary nebula phase is a short period in the cycle of stellar evolution — over a few thousand years, the hot remains of the star in the centre of the nebula heat it up, excite the gas, and make it glow as a planetary nebula. The short lifespan of preplanetary nebulae means there are relatively few of them in existence at any one time. Moreover, they are very dim, requiring powerful telescopes to be seen. This combination of rarity and faintness means they were only discovered comparatively recently. The Egg Nebula {the image at the top right of this resource], the first to be discovered, was first spotted less than 40 years ago, and many aspects of this class of object remain shrouded in mystery."

Strong forces
"Concerning the physical mechanism involved in creating a long-range order in planetary systems, [...] planetary distances can be “accurately predicted by the eigenvalues of the Euler-Lagrange equations resulting from the variation of the free energy of the generic plasma that formed the Sun and planets” [14, 15]. [...] “a unification of the morphology of the solar system” and other astrophysical phenomena “can be accomplished by a basic consideration of the minimum-action states of cosmic and/or virtual vacuum field plasmas” [16]. [...] a unification of all physical forces can be derived based on the assumption that they are regarded “as ‘fluid’ or ‘Magnus’ forces generated by vortex structures (particles) in the virtual plasma gas” [15–17]. [This] might be a key to understanding regular patterns, long-range orders and quantization of astronomical systems and structures."

Weak forces
"At the centre of this image [of the Egg nebula at this resource top right], and hidden in a thick cloud of dust, is the nebula’s central star. While we can’t see the star directly, four searchlight beams of light coming from it shine out through the nebula. It is thought that ring-shaped holes in the thick cocoon of dust, carved by jets coming from the star, let the beams of light emerge through the otherwise opaque cloud. The precise mechanism by which stellar jets produce these holes is not known for certain, but one possible explanation is that a binary star system, rather than a single star, exists at the centre of the nebula."

Emissions
"The onion-like layered structure [of the Egg nebula] of the more diffuse cloud surrounding the central cocoon is caused by periodic bursts of material being ejected from the dying star. The bursts typically occur every few hundred years."

Backgrounds
When the overwhelming radiation from the star GJ 758 is reduced and the star itself eclipsed by a disk, secondary radiation sources appear in the background. These are labeled B and C?.

Subsequent observations with the Subaru Telescope revealed C? to be a background star rather than an object in orbit around GJ 758.

"The source tentatively referred to as “GJ 758 C” [follows] the background star track".

"GJ 758 B exhibits common proper motion with its parent star as well as systematic orbital motion towards the northwest, whereas all other point-sources follow the expected trajectory for background stars (solid arrows). The object referred to as “GJ 758 C” [...] is unambiguously identified as a background star (motion highlighted by dashed blue arrows). The grey plus signs are 1σ error bars. The circle marked as “PSF” shows the size of the resolution element in H-band on [High Contrast Instrument for the Subaru Next Generation Adaptive Optics] HiCIAO."

X-rays
"Chandra and XMM-Newton observations of the red dwarf star Proxima Centauri have shown that its surface is in a state of turmoil. Flares, or explosive outbursts, occur almost continually. This behavior can be traced to Proxima Centauri's low mass, about a tenth that of the Sun. In the cores of low mass stars, nuclear fusion reactions that convert hydrogen to helium proceed very slowly, and create a turbulent, convective motion throughout their interiors. This motion stores up magnetic energy which is often released explosively in the star's upper atmosphere where it produces flares in X-rays and other forms of light."

"The same process produces X-rays on the Sun, but the magnetic energy is released in a less explosive manner through heating loops of gas, with occasional flares. The difference is due to the size of the convection zone, which in a more massive star such as the Sun, is smaller and closer to its surface."

"Red dwarfs are the most common type of star. They have masses between about 8% and 50% of the mass of the Sun. Though they are much dimmer than the Sun, they will shine for much longer - trillions of years in the case of Proxima Centauri, compared to the estimated 10 billion-year lifetime of the Sun."

"X-rays from Proxima Centauri are consistent with a point-like source. The extended X-ray glow is an instrumental effect. The nature of the two dots above the image is unknown - they could be background sources."

"Image is 1.5 arcmin across."

Opticals
"The distance to the Egg Nebula is only known very approximately, the best guess placing it at around 3000 light-years from Earth. This in turn means that astronomers do not have any accurate figures for the size of the nebula (it may be larger and further away, or smaller but nearer). This image [at the top of the resource] is produced from exposures in visible and infrared light from Hubble’s Wide Field Camera 3."

Visuals
The "annotated image [at right] shows key features of the Fomalhaut system, including the newly discovered planet Fomalhaut b, and the dust ring. Also included are a distance scale and an insert, showing how the planet has moved around its parent star over the course of 21 months. The Fomalhaut system is located approximately 25 light-years from the Earth."

The extrasolar planet is in orbit around Fomalhaut and is estimated "to be no more than three times Jupiter's mass ... In 2004, the coronagraph in the High Resolution Camera on Hubble's Advanced Camera for Surveys produced the first-ever resolved visible-light image of a large dust belt surrounding Fomalhaut. It clearly showed that this structure is in fact a ring of protoplanetary debris approximately 21.5 billion miles across with a sharp inner edge. This large debris disk is similar to the Kuiper Belt, which encircles the solar system and contains a range of icy bodies from dust grains to objects the size of dwarf planets, such as Pluto."

"Observations taken 21 months apart by Hubble's Advanced Camera for Surveys' coronagraph show that the object is moving along a path around the star and therefore is gravitationally bound to it. The planet is 10.7 billion miles from the star, or about 10 times the distance of the planet Saturn from the sun."

"A follow-up image in 2006 showed that one of the objects is moving through space with Fomalhaut but changed position relative to the ring since the 2004 exposure. The amount of displacement between the two exposures corresponds to an 872-year-long orbit as calculated from Kepler's laws of planetary motion."

"The planet mysteriously dimmed by half a stellar magnitude between the 2004 and 2006 observations."

Blues
"This image [at the right] captured by the SOFI instrument on ESO’s New Technology Telescope at the La Silla Observatory shows the free-floating planet CFBDSIR J214947.2-040308.9 in infrared light. This object, which appears as a faint blue dot at the centre of the picture and is marked with a cross, is the closest such object to the Solar System. It does not orbit a star and hence does not shine by reflected light; the faint glow it emits can only be detected in infrared light. The object appears blueish in this near-infrared view because much of the light at longer infrared wavelengths is absorbed by methane and other molecules in the planet's atmosphere. In visible light the object is so cool that it would only shine dimly with a deep red colour when seen close-up."

CFBDSIR J214947.2-040308.9 "seems to be part of a nearby stream of young stars known as the AB Doradus Moving Group."

"This is the first isolated planetary mass object ever identified in a moving group, and the association with this group makes it the most interesting free-floating planet candidate identified so far."

“Looking for planets around their stars is akin to studying a firefly sitting one centimetre away from a distant, powerful car headlight. This nearby free-floating object offered the opportunity to study the firefly in detail without the dazzling lights of the car messing everything up.”

"Free-floating objects like CFBDSIR2149 are thought to form either as normal planets that have been booted out of their home systems, or as lone objects like the smallest stars or brown dwarfs. In either case these objects are intriguing — either as planets without stars, or as the tiniest possible objects in a range spanning from the most massive stars to the smallest brown dwarfs."

"The association with the AB Doradus Moving Group would pin down the mass of the planet to approximately 4–7 times the mass of Jupiter, with an effective temperature of approximately 430 degrees Celsius. The planet’s age would be the same as the moving group itself — 50 to 120 million years."

Oranges
"This is a Hubble Space Telescope image of young brown dwarf 2M J044144 [at the right]. It has a companion object at the 8 o'clock position that is estimated to be 5-10 times the mass of Jupiter. In the right panel, the light from the brown dwarf has been subtracted to provide a clearer view of the companion object. The separation of the companion corresponds to 1.4 billion miles at the distance of the Taurus star-forming region, which is only about 1 million years old. The companion may be a very small brown dwarf or a large planet, depending on how it formed. Images were taken with Hubble's Wide Field Planetary Camera 2 to track the motion of the two objects to see if they actually do travel across space together. Additional observations were done with the Gemini North telescope on Mauna Kea, Hawaii."

Reds
"The ERE was first recognized clearly in the peculiar reflection nebula called the Red Rectangle by Schmidt, Cohen, & Margon (1980)."

The Red Rectangle Nebula, so called because of its red color and unique rectangular shape, is a protoplanetary nebula in the Monoceros constellation. Also known as HD 44179, the nebula was discovered in 1973 during a rocket flight associated with the AFCRL Infrared Sky Survey called Hi Star.

In the Red Rectangle Nebula, diffraction-limited speckle images of it in visible and near infrared light reveal a highly symmetric, compact bipolar nebula with X-shaped spikes which imply toroidal dispersion of the circumstellar material. The central binary system is completely obscured, providing no direct light.

Infrareds
One technique uses infrared wavelengths to measure the amount of deuterium to show how much molecular hydrogen is present.

TW Hydrae
"TW Hydrae, a star 176 light-years from Earth in the constellation Hydra ... which has about the same mass as the sun, is surrounded by a dense ring of gas and dust. ... Its circumstellar disk is estimated to between 3 million and 10 million years old, and most protoplanetary disks are thought to last only 2 million to 3 million years. ... [Using the] ESA's Herschel Space Telescope, which is sensitive to the required infrared wavelengths [to measure the amount of deuterium] ... The ratio of deuterium to hydrogen appears constant in Earth's region of space, which means ... measuring hydrogen deuteride [yields] how much regular molecular hydrogen is present. ... TW Hydrae's disk is at least 16,650 times the mass of the Earth. Considering the planets in the solar system may have arisen from a disk only as little as 3,300 times the mass of the Earth, the matter in TW Hydrae's disk would be ample to form a planetary system. "This ... seems to point towards different systems finding disparate pathways to making planets. ... Signs of hydrogen deuteride remain difficult to detect around distant stars".

"These images [on the right], taken a year apart by NASA's Hubble Space Telescope, reveal a shadow moving counterclockwise around a gas-and-dust disk encircling the young star TW Hydrae. The two images at the top show an uneven brightness across the disk. Through enhanced image processing (images at the bottom), the darkening becomes even more apparent."

The "shadow [was noticed] after analyzing 18 years' worth of observations of TW Hydrae, which is about 8 million years old and lies 192 light-years from Earth, in the constellation Hydra. The images, taken by NASA's Hubble Space Telescope, showed that the shadow rotates around the 41-billion-mile-wide (66 billion kilometers) disk once every 16 years."

"This is the very first disk where we have so many images over such a long period of time, therefore allowing us to see this interesting effect. That gives us hope that this shadow phenomenon may be fairly common in young stellar systems."

"An unseen exoplanet is the best explanation for the shadow."

The "alien world itself isn't casting the shadow; rather, the planet's gravity has twisted and tilted the inner portion of the dust-and-gas disk, blocking starlight headed toward the outer reaches."

The "planet lies about 100 million miles (160 million km) from TW Hydrae — about the distance from Earth to the sun. That's way too close to the star for Hubble or any other telescope now in operation to photograph it directly. (Planets that orbit so tightly are drowned out by their parent stars' overwhelming glare.)"

"The putative planet must be about five times more massive than Jupiter to sculpt the inner disk in this manner."

"What is surprising is that we can learn something about an unseen part of the disk by studying the disk's outer region and by measuring the motion, location and behavior of a shadow. This study shows us that even these large disks, whose inner regions are unobservable, are still dynamic, or changing in detectable ways which we didn't imagine."

IRC +10420
"IRC +10420 ... is a peculiar F8I+ hypergiant with a large far-infrared excess attributed to circumstellar dust". The Brα, Pfγ, and Brγ lines are in emission, "with Hα showing a double peaked profile". A Teff range of 6000 K to 6500 K fit the spectral photometry. A Teff range of ~6060 K to ~6300 K is a cyan star. "Based on the model fit, the contribution of the photosphere at the observed wavelengths is: ... Brγ (60%), Pfγ (8%), and Brα (6%), the rest of the continuum emission is due to thermally radiating dust."

Submillimeters
Stars "believed to have circumstellar disks similar to the primitive solar nebula [are] based on the criteria [...]:
 * 1) high far-infrared optical depths around visible stars,
 * 2) shallow spectral energy densities longward of 5 µm, and
 * 3) large millimeter-wave flux densities indicative of ≳ 0.01 M⊙ of H2."

"Evidence for changes in particle composition, size, or shape, reflected in the emissivity index, could therefore be relevant to theories of cosmogony."

"The observations were carried out at the Caltech Submillimeter Observatory (CSO) in Hawaii during 1989 November through December 4, and 1990 December 4 through 9. The detector was a silicon composite bolometer fed by a Winston cone and cooled to a few tenths of a degree with a 3He refrigerator. The filtering employed standard techniques: a scattering filter of black polyethylene fused to fluorogold at 77 K blocked wavelengths in the far-infrared; a crystal quartz filter coated with black polyethylene at 4 K eliminated all near-infrared radiation; and bandpass filters made of metal mesh on nylon or polyethylene, defined the actual wavebands (e.g., Whitcomb & Keene 1980; Cunningham 1982). Different Winston cones were used with each filter to match the diffraction limit of the 10 m telescope, giving different beam sizes on the sky."

Microwaves
"Calculations were made using the wavelength-dependent complex refractive indices of silicate (Draine 1985), glassy carbon (Edoh 1983), and Tholin (Khare et al. 1984). [...] these materials were chosen as broadly representative of the types of matter thought to be present in comet dust."

"Observations using the Atacama Large Millimeter/submillimeter Array (ALMA) have revealed an unexpected spiral structure in the material around the old star R Sculptoris. This feature has never been seen before and is probably caused by a hidden companion star orbiting the star. This slice through the new ALMA data reveals the shell around the star, which shows up as the outer circular ring, as well as a very clear spiral structure in the inner material." The image band is centered at 870 µm.

Gaseous objects
"Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in northern Chile have today announced the discovery of an unexpected clump of carbon monoxide gas in the dusty disc around the star Beta Pictoris. This is a surprise, as such gas is expected to be rapidly destroyed by the star’s UV radiation. Something — probably frequent collisions between small, icy objects such as comets — must be causing the gas to be continuously replenished."

"To get the amount of carbon monoxide we observe, the rate of collisions would be truly startling — complete destruction of a large comet once every five minutes. To get this number of collisions, this would have to be a very tight, massive swarm."

The "disc is permeated by carbon monoxide gas. Paradoxically, the presence of carbon monoxide, which is so harmful to humans on Earth, could indicate that the Beta Pictoris planetary system may eventually be a good habitat for life."

"If there is carbon monoxide in the comets, then there is likely also water ice, meaning that the cometary bombardment that its planets are currently undergoing could also be providing them with life-giving water. Comets contain ices of carbon monoxide, carbon dioxide, ammonia and methane, but the majority component is a mixture of dust and water ice."

"But carbon monoxide is easily and rapidly broken up by starlight — it can only last about 100 years. Seeing it in a disc of this age is a complete surprise. So where did it come from, and why is it still there?"

"Unless we are observing Beta Pictoris at a very unusual time, the carbon monoxide must be continuously replenished. The most abundant source of carbon monoxide in a young solar system is collisions between icy bodies, from comets up to larger planet-sized objects."

"The ALMA image [at the right] of carbon monoxide around Beta Pictoris (above) can be deprojected (below) to simulate a view looking down on the system, revealing the large concentration of gas in its outer reaches. For comparison, orbits within the Solar System are shown for scale."

"But there was another surprise in the ALMA observations, which did not just discover the carbon monoxide, but also mapped its location in the disc through ALMA’s unique ability to simultaneously measure both position and velocity: the gas is concentrated in a single compact clump. This concentration lies 13 billion kilometers from the star, which is about three times the distance of Neptune from the Sun. Why the gas is in this small clump so far from the star is a mystery."

"This clump is an important clue to what is going on in the outer reaches of this young planetary system."

"Gas of the type we are detecting is easy to destroy quickly if it is left floating around in these quantities. The only way this gas survives in disks younger than Beta Pictoris is that it is protected by dense material. Since this is not the case, it needs to be generated anew on relatively short timescales. The only real option for this is comets."

"Carbon monoxide is just the beginning — there may be other more complex pre-organic molecules released from these icy bodies."

Astrochemistry
In December 2006, seven papers were published in the scientific journal, Science, discussing initial details of the sample analysis. Among the findings are: a wide range of organic compounds, including two that contain biologically usable nitrogen; indigenous aliphatic hydrocarbons with longer chain lengths than those observed in the diffuse interstellar medium; abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene, proving consistency with the mixing of solar system and interstellar matter, previously deduced spectroscopically from ground observations; hydrous silicates and carbonate minerals were found to be absent, suggesting a lack of aqueous processing of the cometary dust; limited pure carbon (CHON) was also found in the samples returned; methylamine and ethylamine was found in the aerogel but was not associated with specific particles.

Infrared astronomy deals with the detection and analysis of infrared radiation (wavelengths longer than red light). Except at wavelengths close to visible light, infrared radiation is heavily absorbed by the atmosphere, and the atmosphere produces significant infrared emission. Consequently, infrared observatories have to be located in high, dry places or in space. The infrared spectrum is useful for studying objects that are too cold to radiate visible light, such as planets and circumstellar disks. Longer infrared wavelengths can also penetrate clouds of dust that block visible light, allowing observation of young stars in molecular clouds and the cores of galaxies. Some molecules radiate strongly in the infrared. This can be used to study chemistry in space; more specifically it can detect water in comets.

Carbon
"This Herschel image shows IRC+10216, also known as CW Leonis -- a star rich in carbon where astronomers were surprised to find water. This color-coded image shows the star, surrounded by a clumpy envelope of dust, at three infrared wavelengths, taken by Herschel's spectral and photometric imaging receiver (SPIRE) and photodetector array camera and spectrometer (PACS). Blue shows light of 160 microns; green shows 250 microns; and red shows 350 microns."

Oxygen
An oxygen isotope "discrepancy was noted forty years ago in a stony meteorite that exploded over Pueblito de Allende, Mexico. It has since been confirmed in other meteorites, which are asteroids that fall to Earth. These meteorites are some of the oldest objects in the Solar System, believed to have formed nearly 4.6 billion years ago within the solar nebula’s first million years. The mix of oxygen-16 (the most abundant form with one neutron for each proton) and variants with an extra neutron or two is markedly different in the meteorites than that seen on terrestrial Earth, the moon or Mars."

“Oxygen isotopes in meteorites are hugely different from those of the terrestrial planets, ... With oxygen being the third most abundant element in the universe and one of the major rock forming elements, this variation among different solar system bodies is a puzzle that must be solved to understand how the solar system formed and evolved.”

"In most instances, oxygen isotopes sort out according to mass. Oxygen-17, for example, has just one extra neutron and is incorporated into molecules half as often as oxygen-18, which has two extra neutrons. In these meteorites, however, the rate at which they were incorporated was independent of their masses."

"One theory proposes that the mix of oxygen isotopes was different back when the earliest solid matter in the Solar System formed, perhaps enriched by matter blasted in from a nearby supernova. Another suggests a photochemical effect called self-shielding, which this team had previously ruled out. The final surviving theory was that a physical chemical principle called symmetry could account for the observed patterns of oxygen isotopes."

The final surviving theory was tested "by filling a hockey puck sized chamber with pure oxygen, varying amounts of pure hydrogen and a little black nugget of solid silicon monoxide. A laser was used to vaporize a plume of silicon monoxide gas into the mix. This mixture of ingredients is observed by radiotelescopes in interstellar clouds, the starting point for our Solar System."

"The oxygen and nitrogen reacted with the silicon monoxide gas to form silicon dioxide. This solid, which is the basis of silicate minerals like quartz that are so prevalent in the crust of the Earth, settled as dust in the chamber. The earliest solid materials in the Solar System were formed by these reactions of gases."

After [collecting and analyzing the dust] a mix of oxygen isotopes [was found] that matched the anomalous pattern found in stony meteorites. The fact that the degree of the anomaly scaled with the percentage of the atmosphere that was hydrogen points to a reaction governed by symmetry."

“No matter what else happened early on in the nebula, this is the last step in making the first rocks from scratch, ... We’ve shown that you don’t need a magic recipe to generate this oxygen anomaly. It’s just a simple feature of physical chemistry.”

Compounds
Photometry "in the methane-sensitive CH4S and CH4L narrow-band filters [MCH4S (1.53-1.63 μm) 17.74±0.20 and MCH4L (1.64-1.74 μm) ≥18.86±0.20 on GJ 758 B], collected with high-contrast imaging techniques at Subaru/HiCIAO, Gemini/NIRI, and Keck/NIRC2 [...] is used for updating the estimations of physical and orbital parameters of GJ 758 B."

"GJ 758 B exhibits clear methane absorption. This is generally expected for objects in the late T-type range, although to a decreased extent if the atmosphere is in chemical non-equilibrium".

No methane was detected on GJ 758 A.

Atmospheres
The "HR 8799 planets have much thicker clouds than those required to explain data for typical L and T dwarfs."

Planetary astronomy
"Exoplanets are planets orbiting stars other than our Sun, outside of our Solar System. As of July 2013, most of the 890 exoplanets reported thus far have been discovered by indirect observation techniques, e.g. monitoring the host star for radial velocity variation or planetary transits [Indirect observations detect exoplanets by noting the central star's velocity shift (radial velocity method) or the dimming of stellar light as the planet passes by (transit method).]."

"Such techniques require observations over at least one orbital period and are impractical for detecting planets that are widely separated from their host stars and have long orbital periods."

Direct "imaging may be the most important way to observe exoplanets, because it yields information about the planet's luminosity, temperature, atmosphere, and orbit."

"Astronomers have recently discovered and captured an image of the least massive planet ever imaged so far -- a so-called "second Jupiter". This discovery marks an important step toward the direct imaging of much fainter Earth-like planets in the future and may lead to new models of planet formation."

"Near-infrared color composite images of a “second Jupiter” around the Sun-like star GJ 504 [are at the right]. A coronagraph and differential techniques suppress the bright light from the central star. On the left is the intensity image, which shows the radiant power passing through the area, while on the right is the signal-to-noise ratio image, which shows the weakest signal that the detecting system can recognize."

"Based on the relation of its observed luminosity and estimated age in comparison with the theoretical model, scientists can infer that GJ 504 b has a mass as small as three Jovian masses. If so, it is the lightest-mass planet ever imaged. The apparent distance between the central star and planet is 44 AU (astronomical unit), which is larger than Neptune's orbit and comparable to Pluto's".

Wanderers
"For the first time [as shown in the image at the right], astronomers have been able to directly follow the motion of an exoplanet as it moves to the other side of its host star. The planet has the smallest orbit so far of all directly imaged exoplanets, lying as close to its host star as Saturn is to the Sun."

"The team of astronomers used the NAOS-CONICA instrument (or NACO), mounted on one of the 8.2-metre Unit Telescopes of ESO's Very Large Telescope (VLT), to study the immediate surroundings of Beta Pictoris in 2003, 2008 and 2009. In 2003 a faint source inside the disc was seen, but it was not possible to exclude the remote possibility that it was a background star. In new images taken in 2008 and spring 2009 the source had disappeared! The most recent observations, taken during autumn 2009, revealed the object on the other side of the disc after having been hidden either behind or in front of the star. This confirmed that the source indeed was an exoplanet and that it was orbiting its host star. It also provided insights into the size of its orbit around the star."

"The above composite shows the reflected light on the dust disc in the outer part, as observed in 1996 with the ADONIS instrument on ESO's 3.6-metre telescope. In the central part, the observations of the planet obtained in 2003 and autumn 2009 with NACO are shown. The possible orbit of the planet is also indicated, albeit with the inclination angle exaggerated."

Earth
"This is the first image of Earth ever taken from another planet that actually shows our home as a planetary disk. Because Earth and the Moon are closer to the Sun than Mars, they exhibit phases, just as the Moon, Venus, and Mercury do when viewed from Earth. As seen from Mars by MGS on 8 May 2003 at 13:00 GMT (6:00 AM PDT), Earth and the Moon appeared in the evening sky. The MOC Earth/Moon image has been specially processed to allow both Earth (with an apparent magnitude of -2.5) and the much darker Moon (with an apparent magnitude of +0.9) to be visible together. The bright area at the top of the image of Earth is cloud cover over central and eastern North America. Below that, a darker area includes Central America and the Gulf of Mexico. The bright feature near the center-right of the crescent Earth consists of clouds over northern South America. The image also shows the Earth-facing hemisphere of the Moon, since the Moon was on the far side of Earth as viewed from Mars. The slightly lighter tone of the lower portion of the image of the Moon results from the large and conspicuous ray system associated with the crater Tycho."

Jupiter
"Jupiter and the Galilean moons [are] seen with SCUBA-2 [in the image above]. Rather than seeing the sunlight reflected off the surface of these moons, such as Galileo did 400 years ago, this SCUBA-2 image shows the energy being radiated from the moons themselves."

The order of submillimeter intensity appears to be Ganymede, Callisto, Io, and Europa.

Saturn
Saturn is apparent magnitude 0.8 in this image taken at 2010-03-04 11:45 UT. Saturn is overexposed to bring out fainter objects.

Objects visible in this photo:
 * Two bright background stars to the upper left of Saturn,
 * Iapetus: 2 o'clock position (directly above NGC 4179 at 4 o'clock), labeled I,
 * Titan: bright-outer moon (magnitude 8) at 3 o'clock, labeled T,
 * Dione: 3 o'clock inner moon, labeled D,
 * NGC 4179: 4 o'clock,
 * Hyperion: faint-outer moon (magnitude 14) at 9 o'clock, labeled H,
 * Rhea: inner moon at 9 o'clock, labeled R.

Uranus
On the right is the Uranus system with its moons at 2006-16-08 03:25 UT, just half an hour from a transit of Miranda. It is imaged through the infrared I filter.

"The rings of Uranus are shown here [on the left] captured almost exactly edge-on to Earth. This false-colour image was obtained by the NAOS-CONICA infrared camera on ESO's Very Large Telescope at Paranal, Chile. It was taken at 9:00 UT on 16 August 2007, just two hours after Earth had crossed to the lit side of the ring plane. We are peering over the sunlit face of the rings at an opening of only 0.003 degree, an angle so small that the thin rings nearly disappear. At right, the region around the planet has been enhanced to show a thin line, which is sunlight glinting off the ring edges and also reflected by dust clouds embedded within the system. The pictures at left shows the planet and identifies four of its largest moons. One can clearly discern banding in the atmosphere and a bright cloud feature near the planet's south polar collar, on the left side of the image. This is a composite of images taken at infrared wavelengths. The planet is shown in false colour, based on images taken at wavelengths of 1.2 and 1.6 microns. The rings are extracted from an image taken at 2.2 microns, where the planet is darker and therefore the rings are easier to detect."

"A near-infrared view [in the K band, 2.2 µm, is on the lower right] of the giant planet Uranus with rings and some of its moons, obtained on November 19, 2002, with the ISAAC multi-mode instrument on the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory (Chile). The moons are identified; the unidentified, round object to the left is a background star. The image scale in indicated by the bar."

Neptune
The image at the right shows the Neptune system including Triton.

The "composite Hubble Space Telescope picture [at the left] shows the location of a newly discovered moon, designated S/2004 N 1, orbiting the giant planet Neptune, nearly 3 billion miles from Earth."

"The moon is so small (no more than 12 miles across) and dim, it was missed by NASA's Voyager 2 spacecraft cameras when the probe flew by Neptune in 1989. Several other moons that were discovered by Voyager appear in this 2009 image, along with a circumplanetary structure known as ring arcs."

"Mark Showalter of the SETI Institute discovered S/2004 N 1 in July 2013. He analyzed over 150 archival Neptune photographs taken by Hubble from 2004 to 2009. The same white dot appeared over and over again. He then plotted a circular orbit for the moon, which completes one revolution around Neptune every 23 hours."

Comets
"Comets provide important clues to the physical and chemical processes that occurred during the formation and early evolution of the Solar System [...] Comparing abundances and cosmogonic values (isotope and ortho:para (o/p) ratios) of cometary parent volatiles to those found in the interstellar medium, in disks around young stars, and between cometary families, is vital to understanding planetary system formation and the processing history experienced by organic matter in the so-called interstellar-comet connection [2]. [...] ground-based radio observations towards comets C/2009 P1 (Garradd) and C/2012 F6 (Lemmon) [...] constrain the chemical history of these bodies."

Protoplanetary disks
"A planet forming in the disk [artist's impression at the right] has cleared the disk within 13 AU of the star, a distance comparable to that of Saturn from the sun. As gas and dust flows from the circumstellar disk to the planet, this material surrounds the planet as a circumplanetary disk (inset). These rotating disks are believed to be the birthplaces of planetary moons, such as the Galilean moons that orbit Jupiter. While they are theoretically predicted to surround giant planets at birth, there has been little observational evidence to date for circumplanetary disks outside the solar system."

An "orbiting source of carbon monoxide emission [has a size] consistent with theoretical predictions for a circumplanetary disk. Observations over 10 years trace the orbit of the forming planet from behind the near side of the circumstellar disk in 2003 to the far side of the disk in 2013."

The "star [is] about 335 light years from Earth."

"[A]n "extra" source of gaseous emission from carbon monoxide molecules ... could not be explained by the protoplanetary disk alone."

"By tracking the changes in velocity and position of this extra emission over the years of the observations [using a technique called spectro-astrometry], [the observations] show that it is orbiting around the young star. The distance from the star is somewhat larger than the distance of Saturn from the Sun."

"The candidate planet would be a gas giant at least three times the mass of Jupiter."

"These results provide a rare opportunity to study planet formation in action. Our analysis strongly suggests we are observing a disk of hot gas that surrounds a forming giant planet in orbit around the star. While such circumplanetary disks have been theorized to surround giant planets at birth and to control the flow of gas onto the growing planet, these findings are the first observational evidence for their existence. If our interpretation is correct, we are essentially seeing a planet caught in the act of formation."

Stellar astronomy
"Mizar (sounds like "My Czar") is a binary star. In fact, most stars are binary stars. In a binary star system, each star of the pair follows an elliptical orbital path. Mutual gravity causes the stellar companions to glide around their orbits as if tied to the ends of an elastic string passing through a balance point between them. The balance point is the system's "center of mass"."

"Spectroscopic observations of the Mizar system show periodic doppler shifts, revealing that both stars, Mizar A and Mizar B, are themselves binary stars! But, the companions are too close to be directly observed as separate stars, even by the largest telescopes. In developing a new optical interferometer capable of extremely high resolution while peering through the Earth's blurry atmosphere, U.S. Naval Observatory and Naval Research Lab astronomers have been able to detect the companion star to Mizar A. This composite image of their observations shows the daily and monthly relative orbital motion in the binary system."

Astrography
"An enormous alien planet — one that is 11 times more massive than Jupiter — was discovered in the most distant orbit yet found around a single parent star."

"The newfound exoplanet, dubbed HD 106906 b, dwarfs any planetary body in the solar system, and circles its star at a distance that is 650 times the average distance between the Earth and the sun. The existence of such a massive and distantly orbiting planet raises new questions about how these bizarre worlds are formed"

"This system is especially fascinating because no model of either planet or star formation fully explains what we see."

"A binary star system can be formed when two adjacent clumps of gas collapse more or less independently to form stars, and these stars are close enough to each other to exert a mutual gravitation attraction and bind them together in an orbit."

"In the HD 106906 system, the star and planet may have collapsed independently, but the materials that clumped together to form the planet were insufficient for it to grow large enough to ignite into a new star."

"In our case, the mass ratio is more than 100-to-1. This extreme mass ratio is not predicted from binary star formation theories — just like planet formation theory predicts that we cannot form planets so far from the host star."

"Every new directly detected planet pushes our understanding of how and where planets can form. Discoveries like HD 106906 b provide us with a deeper understanding of the diversity of other planetary systems."

"In a day when we have examined astronomical objects shining forth from a time shortly after the Big Bang, one would think astronomers have a pretty good handle on what is in the immediate vicinity of the Solar System. That's why the recent report of a binary star lying only 6.5 light-years away came as rather a surprise to the astronomical community. The pair, called WISE J1049-5319 A and B [in the image at the second right], are brown dwarf stars and only two star systems – the triple star Alpha Centauri, and Barnard's Star – lie closer to our Sun."

"During a spectroscopic examination of WISE J1049-5319 using the Gemini 8.1 meter (26 foot) telescope, Prof. Luhman found that the object is actually a binary star system composed of two brown dwarfs currently separated by 1.5 seconds of arc. Their period of rotation around each other is about 25 years, which corresponds to a separation of about three astronomical units (approximately 449 million km). The spectrum revealed that the surface temperature of the stars is in the neighborhood of 1300 K (1850 F)."

"It will be an excellent hunting ground for planets because it is very close to Earth, which makes it a lot easier to see any planets orbiting either of the brown dwarfs. Since it is the third-closest star system, in the distant future it might be one of the first destinations for manned expeditions outside our solar system."

History
"Also known as zeta Ursae Majoris, Mizar is the middle star in the handle of the Big Dipper and at a distance of 88 light years, was the first binary star system to be imaged telescopically."

At the right is a Very Large Telescope "VLT NACO image, taken in the Ks-band, of GQ Lupi. The feeble point of light to the right of the star is the newly found cold companion. It is 250 times fainter than the star itself and is located 0.73 arcsecond west. At the distance of GQ Lupi, this corresponds to a distance of roughly 100 astronomical units. North is up and East is to the left."

"NACO on the VLT [was used] to take a series of spectra. These showed the typical signature of a very cool object, in particular the presence of water and CO bands. Taking into account the infrared colours and the spectral data available, atmospheric model calculations point to a temperature between 1,600 and 2,500 degrees and a radius that is twice as large as Jupiter [...]. According to this, GQ Lupi B is thus a cold and rather small object."

Astrophysics
A "new planet [in the image at the right] 155 light years from our solar system. A gas giant has been added to the short list of exoplanets discovered through direct imaging. It is located around GU Psc, a star three times less massive than the Sun and located in the constellation Pisces."

"GU Psc b is around 2,000 times the Earth-Sun distance from its star, a record among exoplanets. Given this distance, it takes approximately 80,000 Earth years for GU Psc b to make a complete orbit around its star!"

"By comparing images obtained in different wavelengths (colours) from the OMM and CFHT, they were able to correctly detect the planet."

"Planets are much brighter when viewed in infrared rather than visible light, because their surface temperature is lower compared to other stars. This allowed us to identify GU Psc b."

"Observing a planet does not directly allow determining its mass. Instead, researchers use theoretical models of planetary evolution to determine its characteristics. The light spectrum of GU Psc b obtained from the Gemini North Telescope in Hawaii was compared to such models to show that it has a temperature of around 800°C. Knowing the age of GU Psc due to its location in AB Doradus, the team was able to determine its mass, which is 9-13 times that of Jupiter."

Sciences
"Astronomers using the NASA/ESA Hubble Space Telescope have photographed one of the smallest objects ever seen around a normal star beyond our Sun. Weighing in at 12 times the mass of Jupiter, the object is small enough to be a planet. The conundrum is that it's also large enough to be a brown dwarf, a failed star."

"New, more sensitive telescopes are finding smaller and smaller objects of planetary-mass size. These discoveries have prompted astronomers to ask the question, are planetary-mass companions always planets?"

"The object is so far away from its star that it is unlikely to have formed in a circumstellar disk."

"The study of substellar objects in orbit around a star allows us to determine the age, and over time also the mass of the companion. Such studies help us to improve out understanding of the formation and inner structure of brown dwarfs and planets."

Technology
The two images at right are "of HD 157728, a nearby star 1.5 times larger than the Sun. The star is centered in both images, and its light has been mostly removed by the adaptive optics system and coronagraph. The remaining starlight leaves a speckled background against which fainter objects cannot be seen. On the left, the image was made without the ultra-precise starlight control that Project 1640 is capable of. On the right, the wavefront sensor was active, and a darker square hole formed in the residual starlight, allowing objects up to 10 million times fainter than the star to be seen. Images were taken on June 14, 2012 with Project 1640 on the Palomar Observatory’s 200-inch Hale telescope."

“We are blinded by this starlight, [...] Once we can actually see these exoplanets, we can determine the colors they emit, the chemical compositions of their atmospheres, and even the physical characteristics of their surfaces.”

“Imaging planets directly is supremely challenging, [...] Imagine trying to see a firefly whirling around a searchlight more than a thousand miles away.”

"The project is based on four instruments that take infrared photos of light generated by stars and the warm planets that orbit them. The instruments are now operating, and produce some of the highest-contrast images ever created."

"The project is helping to create images that reveal celestial objects 1 million to 10 million times fainter than the star at the center of the image."

“High-contrast imaging requires each subsystem perform flawlessly and in complete unison to differentiate planet light from starlight, [...] Even a small starlight leak in the system can inundate our photodetectors and pull the shroud back down over these planets.”

“The more we learn about them, the more we realize how vastly different planetary systems can be from our own, [...] All indications point to a tremendous diversity of planetary systems, far beyond what was imagined just 10 years ago. We are on the verge of an incredibly rich new field.”

“In order to understand the origin of Earth, we need to understand the origin of planets in general, [...] How do they form, how do they evolve? How does our solar system with both gas giant and rocky small planets compare to others? These are questions that are very important to humanity.”

Hypotheses

 * 1) Solar systems occur between galaxies.