An image of the circum-stellar disk around HD 207129. The three circled objects are background objects and are not part of the disk. Image: Hubble Space Telescope, Glenn Schneider et al 2016.
A team using the Hubble Space Telescope has imaged circumstellar disk structures (CDSs) around three stars similar to our Sun. The stars are all G-type solar analogs, and the disks themselves share similarities with our Solar System’s own Kuiper Belt. Studying these CDSs will help us better understand their ring-like structure, and the formation of solar systems.
The team behind the study was led by Glenn Schneider of the Seward Observatory at the University of Arizona. They used the Hubble’s Space Telescope Imaging Spectrograph to capture the images. The stars in the study are HD 207917, HD 207129, and HD 202628.
Theoretical models of circumstellar disk dynamics suggest the presence of CDSs. Direct observation confirms their presence, though not many of these disks are within observational range. These new deep images of three solar analog CDSs are important. Studying the structure of these rings should lead to a better understanding of the formation of solar systems themselves.
A is the observed image of HD 207917. B is the best-fit debris ring model of the same star. Image: Hubble, G. Schneider et. al. 2016.
Debris disks like these are separate from protoplanetary disks. Protoplanetary disks are a mixture of both gas and dust which exist around younger stars. They are the source material out of which planetesimals form. Those planetesimals then become planets.
Protoplanetary disks are much shorter-lived than CDSs. Whatever material is left over after planet formation is typically expelled from the host solar system by the star’s radiation pressure.
In circumstellar debris disks like the ones imaged in this study, the solar system is older, and the planets have already formed. CDSs like these have lasted this long by replenishing themselves. Collisions between larger bodies in the solar system create more debris. The resulting debris is continually ground down to smaller sizes by repeated collisions.
This process requires gravitational perturbation, either from planets in the system, or by binary stars. In fact, the presence of a CDSs is a strong hint that the solar system contains terrestrial planets.
A circumstellar disk of debris around a mature stellar system could indicate the presence of Earth-like planets. Credit: NASA/JPL
The three disks in this study were viewed at intermediate inclinations. They scatter starlight, and are more easily observed than edge-on disks. Each of the three circumstellar disk structures possess “ring-like components that are more massive analogs of our solar system’s Edgeworth–Kuiper Belt,” according to the study.
The study authors expect that the images of these three disk structures will be studied in more detail, both by themselves and by others in future research. They also say that the James Webb Space Telescope will be a powerful tool for examining CDSs.
Fraser, Morgan and Sondy were all at the Kennedy Space Center in Florida to watch the launch of the OSIRIS-REx Mission. Sondy and Morgan talked about the mission, answered questions about space and astronomy, Cassini.
Just a sneak preview before the Weekly Space Hangout starts up later this week!
We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
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The interior structure of the Sun. Credit: Wikipedia Commons/kelvinsong
From here on Earth, the Sun like a smooth ball of light. And prior to Galileo’s discovery of sunposts, astronomers even thought it was a perfect orb with no imperfections. However, thanks to improved instruments and many centuries of study, we know that the Sun is much like the planets of our Solar System.
In addition to imperfections on its surface, the Sun is also made up of several layers, each of which serves its own purpose. It’s this structure of the Sun that powers this massive engine that provides the planets with all the light and heat they receive. And here on Earth, it is what provides all life forms with the energy they need to thrive and survive.
Composition:
If you could take the Sun apart, and stack up its various elements, you would find that the Sun is made of hydrogen (74%) and helium (about 24%). Astronomers consider anything heavier than helium to be a metal. The remaining amount of the Sun is made of iron, nickel, oxygen, silicon, sulfur, magnesium, carbon, neon, calcium and chromium. In fact, the Sun is 1% oxygen; and everything else comes out of that last 1%.
Where did these elements come from? The hydrogen and helium came from the Big Bang. In the early moments of the Universe, the first element, hydrogen, formed from the soup of elementary particles. The pressure and temperatures were still so intense that the entire Universe had the same conditions as the core of a star.
Hydrogen was fused into helium until the Universe cooled down enough that this reaction couldn’t happen any more. The ratios of hydrogen and helium that we see in the Universe today were created in those first few moments after the Big Bang. The other elements were created in other stars. Stars are constantly fusing hydrogen into helium in their cores.
Once the hydrogen in the core runs out, they switch to fusing heavier and heavier elements, like helium, lithium, oxygen. Most of the heavier metals we see in the Sun were formed in other stars at the end of their lives. The heaviest elements, like gold and uranium, were formed when stars many times more massive that our Sun detonated in supernova explosions.
In a fraction of a second, as a black hole was forming, elements were crushed together in the intense heat and pressure to form the heaviest elements. The explosion scattered these elements across the region, where they could contribute to the formation of new stars.
Our Sun is made up of elements left over from the Big Bang, elements formed from dying stars, and elements created in supernovae. That’s pretty amazing.
Structure:
Although the Sun is mostly just a ball of hydrogen and helium, it’s actually broken up into distinct layers. The layers of the Sun are created because the temperatures and pressures increase as you move towards the center of the Sun. The hydrogen and helium behave differently under the changing conditions.
The Core: Let’s start at the innermost layer of the Sun, the core of the Sun. This is the very center of the Sun, where temperatures and pressures are so high that fusion can happen. The Sun is combining hydrogen into helium atoms, and this reaction gives off the light and heat that we see here on Earth. The density of the core is 150 times the density of water, and the temperatures are thought to be 13,600,000 degrees Kelvin.
Astronomers believe that the core of the Sun extends from the center out to about 0.2 solar radius. And within this region, temperatures and pressures are so high that hydrogen atoms are torn apart to form separate protons, neutrons and electrons. With all of these free floating particles, the Sun is able to reform them into atoms of helium.
This reaction is exothermic. That means that the reaction gives off a tremendous amount of heat – 3.89 x 1033 ergs of energy every second. The light pressure of all this energy streaming from the core of the Sun is what stops it from collapsing inward on itself.
Radiative Zone: The radiative zone of the Sun starts at the edge of the core of the Sun (0.2 solar radii), and extends up to about 0.7 radii. Within the radiative zone, the solar material is hot and dense enough that thermal radiation transfers the heat of the core outward through the Sun.
The core of the Sun is where nuclear fusion reactions are happening – protons are merged together to create atoms of helium. This reaction produces a tremendous amount of gamma radiation. These photons of energy are emitted, absorbed, and then emitted again by various particles in the radiative zone.
The path that photons take is called the “random walk”. Instead of going in a straight beam of light, they travel in a zigzag direction, eventually reaching the surface of the Sun. In fact, it can take a single photon upwards of 200,000 years to make the journey through the radiative zone of the Sun.
As they transfer from particle to particle, the photons lose energy. That’s a good thing, since we wouldn’t want only gamma radiation streaming from the Sun. Once these photons reach space, they take a mere 8 minutes to get to Earth.
Most stars will have radiative zones, but their size depends on the star’s size. Small stars will have much smaller radiative zones, and the convective zone will take up a larger portion of the star’s interior. The smallest stars might not have a radiative zone at all, with the convective zone reaching all the way down to the core. The largest stars would have the opposite situation, where the radiative zone reaches all the way up to the surface.
Convective Zone: Outside the radiative zone is another layer, called the convective zone, where heat from inside the Sun is carried up by columns of hot gas. Most stars have a convective zone. In the case of the Sun, it starts at around 70% of the Sun’s radius and goes to the outer surface (the photosphere).
Gas deeper inside the star is heated up so that it rises, like globs of wax in a lava lamp. As it gets to the surface, the gas loses some of its heat, cools down, and sinks back towards the center to pick up more heat. Another example would be a pot of boiling water on the stove.
The surface of the Sun looks granulated. These granules are the columns of hot gas that carry heat to the surface. They can be more than 1,000 km across, and typically last about 8 to 20 minutes before dissipating. Astronomers think that low mass stars, like red dwarfs, have a convective zone that goes all the way down to the core. Unlike the Sun, they don’t have a radiative zone at all.
Photosphere: The layer of the Sun that we can see from Earth is called the photosphere. Below the photosphere, the Sun becomes opaque to visible light, and astronomers have to use other methods to probe its interior. The temperature of the photosphere is about 6,000 Kelvin, and gives off the yellow-white light that we see.
Above the photosphere is the atmosphere of the Sun. Perhaps the most dramatic of these is the corona, which is visible during a total solar eclipse.
Graphic showing a model of the layers of the Sun, with approximate mileage ranges for each layer. Credit: NASA
Diagram:
Below is a diagram of the Sun, originally developed by NASA for educational purposes.
Visible, IR and UV radiation – The light that we see coming from the Sun is visible, but if you close your eyes and just feel the warmth, that’s IR, or infrared radiation. And the light that gives you a sunburn is ultraviolet (UV) radiation. The Sun produces all of these wavelengths at the same time.
Photosphere 6000 K – The photosphere is the surface of the Sun. This is the region where light from the interior finally reaches space. The temperature is 6000 K, which is the same as 5,700 degrees C.
Photosphere 6000 K – The photosphere is the surface of the Sun. This is the region where light from the interior finally reaches space. The temperature is 6000 K, which is the same as 5,700 degrees C.
Radio emissions – In addition to visible, IR and UV, the Sun also gives off radio emissions, which can be detected by a radio telescope. These emissions rise and fall depending on the number of sunspots on the surface of the Sun.
Coronal Hole – These are regions on the Sun where the corona is cooler, darker and has less dense plasma.
2100000 – This is the temperature of the Sun’s radiative zone.
Convective zone/Turbulent convection – This is the region of the Sun where heat from the core is transferred through convection. Warm columns of plasma rise to the surface in columns, release their heat and then fall back down to heat up again.
Coronal loops – These are loops of plasma in the Sun’s atmosphere that follows magnetic flux lines. They look like big arches, stretching up from the surface of the Sun for hundreds of thousands of kilometers.
Core – The is the heart of the Sun, where the temperatures and pressures are so high that nuclear fusion reactions can happen. All of the energy coming from the Sun originates from the core.
14500000 K – The temperature of the core of the Sun.
Radiative Zone – The region of the Sun where energy can only be transferred through radiation. It can take a single photon 200,000 years to get from the core, through the radiative zone, out to the surface and into space.
Neutrinos – Neutrinos are nearly mass-less particles blasted out from the Sun as part of the fusion reactions. There are millions of neutrinos passing through your body every second, but they don’t interact, so you can’t feel them.
Chromospheric Flare – The Sun’s magnetic field can get twisted up and then snap into a different configuration. When this happens, there can be powerful X-ray flares emanating from the surface of the Sun.
Magnetic Field Loop – The Sun’s magnetic field extends out above its surface, and can be seen because hot plasma in the atmosphere follows the field lines.
Spot – A sunspot. These are areas on the Sun’s surface where the magnetic field lines pierce the surface of the Sun, and they’re relatively cooler than the surrounding areas.
Prominence – A bright feature that extends above the surface of the Sun, often in the shape of a loop.
Energetic particles – There can be energetic particles blasting off the surface of the Sun to create the solar wind. In solar storms, energetic protons can be accelerated to nearly the speed of light.
X-rays – In addition to the wavelengths we can see, there are invisible X-rays coming from the Sun, especially during flares. The Earth’s atmosphere protects us from this radiation.
Bright spots and short-lived magnetic regions – The surface of the Sun has many brighter and dimmer spots caused by changing temperature. The temperature changes from the constantly shifting magnetic field.
Yes, the Sun is like an onion. Peel back one layer and you’ll find many more. But in this case, each layers is responsible for a different function. And what they add to is a giant furnace and light source that keeps us living beings here on Earth warm and illuminated!
And be sure to enjoy this video from the NASA Goddard Center, titled “Snapshots from the Edge of the Sun”:
United Launch Alliance Atlas V rocket lifts off from Space Launch Complex 41 at Cape Canaveral Air Force Station carrying NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, or OSIRIS-REx spacecraft on the first U.S. mission to sample an asteroid, retrieve at least two ounces of surface material and return it to Earth for study. Liftoff was at 7:05 p.m. EDT on September 8, 2016 in this remote camera view taken from inside the launch pad perimeter. Note the newly install crew access arm and white room for astronaut flights atop Atlas starting in early 2018. Credit: Ken Kremer/kenkremer.com
United Launch Alliance Atlas V rocket lifts off from Space Launch Complex 41 at Cape Canaveral Air Force Station carrying NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, or OSIRIS-REx spacecraft on the first U.S. mission to sample an asteroid, retrieve at least two ounces of surface material and return it to Earth for study. Liftoff was at 7:05 p.m. EDT on September 8, 2016 in this remote camera view taken from inside the launch pad perimeter. Note the newly installed crew access arm and white room for astronaut flights atop Atlas starting in early 2018. Credit: Ken Kremer/kenkremer.com
KENNEDY SPACE CENTER, FL – Bound for Bennu, NASA’s OSIRIS-REx robotic explorer began a trailblazing 7 year round trip sampling sortie on Sept. 8 in search of the origin of life with a spectacular sky show – thrilling spectators ringing the Florida Space Coast.
Hordes of space enthusiasts from all across the globe descended on the Kennedy Space Center and Cape Canaveral region for the chance of a lifetime to witness a once in a lifetime liftoff to the carbon rich asteroid – which could potentially bring back samples infused with the organic chemicals like amino acids that are the building blocks of life as we know it.
NASA’s Origins, Spectral Interpretation, Resource Identification, Security – Regolith Explorer (OSIRIS-REx) spacecraft departed Earth with an on time engine ignition of a United Launch Alliance Atlas V rocket under crystal clear skies on Thursday, September 8 at 7:05 p.m. EDT from Space Launch Complex 41 at Cape Canaveral Air Force Station.
Blastoff of NASA’s OSIRIS-Rex asteroid sampling spacecraft on September 8, 2016 from Cape Canaveral Air Force Station, FL as seen from Playalinda Beach. Credit: Jillian Laudick
Everything went exactly according to plan for the daring mission bolding seeking to gather rocks and soil from Bennu – using an ingenious robotic arm named TAGSAM – and bring at least a 60-gram (2.1-ounce) sample back to Earth in 2023 for study by scientists using the world’s most advanced research instruments.
“We got everything just exactly perfect,” said Dante Lauretta, the principal investigator for OSIRIS-REx at the University of Arizona, at the post launch briefing at the Kennedy Space Center. “We hit all our milestone within seconds of predicts.
The space rock measures about the size of a small mountain at about a third of a mile in diameter.
And the picture perfect near sunset launch rewarded photographers from near and far with a spectacular series of richly hued photo and video recordings.
So I’ve gathered here a variety of launch imagery from multiple vantage points shot by friends, colleagues and myself – for the enjoyment of readers of Universe Today and Beyond!
Liftoff of NASA’s OSIRIS-Rex asteroid sampling spacecraft on September 8, 2016 from Cape Canaveral Air Force Station, FL. Credit: Julian Leek
As you’ll see and hear the ULA Atlas V rocket integrated with OSIRIS-Rex on top thundered off the Cape’s pad 41 and shot skyward straight up along an equatorial path into Florida’s sun.
From every vantage point the rocket and its ever expanding vapor trail were visible for some 4 or 5 minutes or more. From my location on the roof of NASA’s Vehicle Assembly Building (VAB) the rocket finally arched over nearly straight above us and the sun produced a magnificent thin and nearly straight shadow of the vapor trail on the ground running out to the Atlantic Ocean towards Africa.
Blastoff of NASA’s OSIRIS-Rex asteroid sampling spacecraft on September 8, 2016 from Cape Canaveral Air Force Station, FL as seen from Playalinda Beach. Credit: John Kraus
It was truly an unforgettable sight to behold. And folks at Playalinda Beach, the best public viewing spot just a few miles north of pad 40 had an uninhibited view of the rocket to the base of the pad – while they waded and swam in the oceans waters with waves crashing on shore as the Atlas rocket blasted to space.
OSIRIS-REx separated as planned from the Atlas V rockets liquid oxygen and liquid hydrogen fueled second stage rocket to fly free at 8:04 p.m. on Sept. 8 – 55 minutes after launch.
The pair of solar arrays deployed as planned to provide the probes life giving power.
The spacecraft was built by prime contractor Lockheed.
“The spacecraft is healthy and functioning properly,” Richard Kuhns, Lockheed Martin OSIRIS-REx program manager, told me in an interview at the post-launch briefing.
Members of the OSIRIS-REx mission team celebrate the successful spacecraft launch on Sept. 8, 2016 atop ULA Atlas V at the post-launch briefing at the Kennedy Space Center, FL. Principal Investigator Dante Lauretta is 4th from right, NASA Planetary Science Director Jim Green is center, 5th from left. Richard Kuhns, Lockheed Martin OSIRIS-REx program manager, 2nd from right. Credit: Ken Kremer/kenkremer.com
“The primary objective of the OSIRIS-Rex mission is to bring back pristine material from the surface of the carbonaceous asteroid Bennu, OSIRIS-Rex Principal Investigator Dante Lauretta told Universe Today in a prelaunch interview in the KSC cleanroom with the spacecraft as the probe was undergoing final preparations for shipment to the launch pad.
“We are interested in that material because it is a time capsule from the earliest stages of solar system formation.”
“It records the very first material that formed from the earliest stages of solar system formation. And we are really interested in the evolution of carbon during that phase. Particularly the key prebiotic molecules like amino acids, nucleic acids, phosphates and sugars that build up. These are basically the biomolecules for all of life.”
The asteroid is 1,614-foot (500 m) in diameter and crosses Earth’s orbit around the sun every six years.
After a two year flight through space, including an Earth swing by for a gravity assisted speed boost in 2017, OSIRIS-REx will reach Bennu in Fall 2018 to begin about 2 years of study in orbit to determine the physical and chemical properties of the asteroid in extremely high resolution.
While orbiting Bennu starting in 2018 it will move in close to explore the asteroid for about two years with its suite of science instruments, scanning in visible and infrared light. After a thorough site selection, it will move carefully towards the surface and extend the 11 foot long TAGSAM robotic arm and snatch pristine soil samples containing organic materials from the surface using the TAGSAM collection dish over just 3 to 5 seconds.
Once a good sample collection is confirmed, the dish will then be placed inside the Earth return canister and be brought back to Earth for study by researchers using all of the most sophisticated science instruments available to humankind.
Using the 11 foot long TAGSAM robotic arm that functions somewhat like a pogo stick, OSIRIS-REx will gather rocks and soil and bring at least a 60-gram (2.1-ounce) sample back to Earth on Sept 24, 2023. It has the capacity to scoop up to about 2 kg or more.
ULA Atlas V rocket lifts off on September 8, 2016 from Space Launch Complex 41 at Cape Canaveral Air Force Station carrying NASA’s OSIRIS-REx asteroid sampling spacecraft, in this remote camera view taken from inside the launch pad perimeter. Credit: Ken Kremer/kenkremer.com
The two stage ULA Atlas V performed flawlessly and delivered OSIRIS-Rex into a hyperbolic trajectory away from Earth.
The 189 foot tall ULA Atlas V rocket launched in the rare 411 configuration for only the 3rd time on this mission – which is the 65th for the Atlas V.
The Atlas 411 vehicle includes a 4-meter diameter large Payload Fairing (PLF) and one solid rocket booster that augments the first stage. The Atlas booster for this mission is powered by the RD AMROSS RD-180 engine and the Centaur upper stage was powered by the Aerojet Rocketdyne RL10A.
The RD-180 burns RP-1 (Rocket Propellant-1 or highly purified kerosene) and liquid oxygen and delivers 860,200 lb of thrust at sea level.
The strap on solid delivers approximately 348,500 pounds of thrust.
The Centaur delivers 22, 230 lbf of thrust and burns liquid oxygen and liquid hydrogen.
The solid was jettisoned at 139 seconds after liftoff.
Launch of NASA’s OSIRIS-REx on September 8, 2016 from Cape Canaveral Air Force Station, FL as seen from LC-39 Gantry. Credit: Jen Saxby
This is ULA’s eighth launch in 2016 and the 111th successful launch since the company was formed in December 2006.
NASA’s OSIRIS-REx blasts off to asteroid Bennu on ULA Atlas V rocket prior on Sept. 8, 2016 from Space Launch Complex 41 on Cape Canaveral Air Force Station, FL, as seen from the VAB roof. Credit: Lane Hermann/SpaceHeadNews
OSIRIS-REx will return the largest sample from space since the American and Soviet Union’s moon landing missions of the 1970s.
Watch these pair of up close videos (from myself and Jeff Seibert) captured directly at the pad with the sights and sounds of the fury of launch:
Video Caption: ULA Atlas V rocket lifts off on September 8, 2016 from Space Launch Complex 41 at Cape Canaveral Air Force Station carrying NASA’s OSIRIS-REx asteroid sampling spacecraft, in this remote camera view taken from inside the launch pad perimeter. Credit: Ken Kremer/kenkremer.com
Video Caption: Compilation of my launch videos from the ULA Atlas 5 launch in support of the NASA OSIRIS_REx asteroid sample return mission to the asteroid Bennu (#101955). It was launched on September 8th, 2016 from Pad 41 of CCAFS. It is scheduled to land in UTAH with asteroid samples on September 24, 2023. Credit: Jeff Seibert
OSIRIS-REx is the third mission in NASA’s New Frontiers Program, following New Horizons to Pluto and Juno to Jupiter, which also launched on Atlas V rockets.
NASA’s Goddard Space Flight Center in Greenbelt, Maryland, is responsible for overall mission management.
OSIRIS-REx complements NASA’s Asteroid Initiative – including the Asteroid Redirect Mission (ARM) which is a robotic spacecraft mission aimed at capturing a surface boulder from a different near-Earth asteroid and moving it into a stable lunar orbit for eventual up close sample collection by astronauts launched in NASA’s new Orion spacecraft. Orion will launch atop NASA’s new SLS heavy lift booster concurrently under development.
Launch of NASA’s OSIRIS-REx on September 8, 2016 from Cape Canaveral Air Force Station, FL as seen from VAB roof. Credit: J.Sekora/SEKORAPHOTO
Watch for Ken’s continuing OSIRIS-REx mission and launch reporting from on site at the Kennedy Space Center and Cape Canaveral Air Force Station, FL.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
NASA’s OSIRIS-Rex asteroid sampling spacecraft streaks to orbit on September 8, 2016 from Cape Canaveral Air Force Station, FL as seen from Playalinda Beach. Credit: Jillian LaudickLiftoff of NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, or OSIRIS-Rex asteroid sampling spacecraft on September 8, 2016 from Cape Canaveral Air Force Station, FL. Credit: Ken Kremer/kenkremer.comA United Launch Alliance Atlas V rocket lifts off from Space Launch Complex 41 at Cape Canaveral Air Force Station carrying NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, or OSIRIS-REx spacecraft on the first U.S. mission to sample an asteroid, retrieve at least two ounces of surface material and return it to Earth for study. Liftoff was at 7:05 p.m. EDT on September 8, 2016. Credit: Ken Kremer/kenkremer.comView of science instrument suite and TAGSAM robotic sample return arm on NASA’s OSIRIS-REx asteroid sampling spacecraft inside the Payloads Hazardous Servicing Facility at NASA’s Kennedy Space Center. Probe is slated for Sep. 8, 2016 launch to asteroid Bennu from Cape Canaveral Air Force Station, FL. Credit: Ken Kremer/kenkremer.com
Messier 23, Messier 21, Trifid Nebula (M20) and Omega Nebula (M17). Credit: Wikisky
Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at the Messier 23 open star cluster. Enjoy!
Back in the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of these objects so that other astronomers wouldn’t make the same mistake. Consisting of 100 objects, the Messier Catalog has come to be viewed as a major milestone in the study of Deep Space Objects.
One of these objects is Messier 23 (aka. NGC 6494), a large open star cluster that is located in the constellation Sagittarius. Given its luminosity, it can be found quite easily in the rich star fields of the summer Milky Way using small telescopes and even binoculars.
Description:
Located some 2,150 light years (659 Parsecs) away from Earth, this vast cloud of 176 confirmed stars stretches across 15 to 20 light years of space. At an estimated 220 to 300 million years old, Messier 23 is on the “senior citizen” list of galactic open clusters in our galaxy. At this age, its hottest stars reach spectral type B9, and it even contains a few blue straggler candidates.
Mosaic image obtained as part of the Two Micron All Sky Survey (2MASS). Credit: UofM/IPAC/Caltech/NASA/NSF
Given that M23 has spent many centuries sweeping through the interstellar medium, astronomers have wondered how this would affect its metal content. Using UBV photometry, astronauts examined the metallicity of M23, and determined that it had no discernible effect. As W.L. Sanders wrote of the cluster in 1990:
“UBV photometric observations of 176 stars in the galactic cluster NGC 6494 are presented and analyzed. The effect of a gas poor environment on the metal abundance of NGC 6494 is studied. It is determined that the metallicity of NGC 6494, which has a delta(U – B) value = + 0.02, is not affected by the interarm region in which it dwelled.”
At the same time, astronomers have discovered that some of M23’s older stars – the red giants – are suffering mass loss. As G. Barbaro (et al.) of the Istituto di Fisica dell’Universita put it in 1969:
“A statistical research on evolved stars beyond hydrogen exhaustion is performed by comparing the H-R diagrams of about 60 open clusters with a set of isochronous curves without mass loss derived from Iben’s evolutionary tracks and time scales for Population I stars. Interpreting the difference in magnitude between the theoretical positions thus calculated and the observed ones as due to mass loss, when negative, the results indicate that this loss may be conspicuous only for very massive and red stars. However, a comparison with an analogous work of Lindoff reveals that the uncertainties connected with the bolometric and color corrections may invalidate by a large amount the conclusions which might be drawn from such research.”
Close-up of the core of M23, showing some of its brightest member stars. Credit: Sharp/NOAO/AURA/NSF
However, the most recent studies show that we have to determine radial velocities before we can really associate red giants as being cluster members. J.C. Mermilliod of Laboratoire d’Astrophysique de l’Ecole wrote in his 2008 study, “Red giants in open clusters“:
“The present material, combined with recent absolute proper motions, will permit various investigation of the galactic distribution and space motions of a large sample of open clusters. However, the distance estimates still remain the weakest part of the necessary data. This paper is the last one in this series devoted to the study of red giants in open clusters based on radial velocities obtained with the CORAVEL instruments.”
History of Observation:
This neat and tidy galactic star cluster was one of the original discoveries of Charles Messier. As he recorded of the cluster when first viewing it, which occurred on June 20th, 1764:
“In the night of June 20 to 21, 1764, I determined the position of a cluster of small stars which is situated between the northern extremity of the bow of Sagittarius and the right foot of Ophiuchus, very close to the star of sixth magnitude, the sixty-fifth of the latter constellation [Oph], after the catalog of Flamsteed: These stars are very close to each other; there is none which one can see easily with an ordinary refractor of 3 feet and a half, and which was taken for these small stars. The diameter of all is about 15 minutes of arc. I have determined its position by comparing the middle with the star Mu Sagittarii: I have found its right ascension of 265d 42′ 50″, and its declination of 18d 45′ 55″, south.”
The M23 open star cluster, as it appears in the night sky (a patch of red), flanked by M8 (Lagoon), M16 (Eagle), M17 (Omega), M20 (Trifid) and other deep sky objects. Credit & Copyright: Fernando Cabrerizo/NASA
While William Herschel did not publish his observations of Messier’s objects, he was still an avid observer. So of course, he had to look at this cluster, and wrote the following observations in his personal notes:
“A cluster of beautiful scattered, large stars, nearly of equal magnitudes (visible in my finder), it extends much farther than the field of the telescope will take in, and in the finder seems to be a nebula of a lengthened form extending to about half a degree.”
In July of 1835, Admiral Smyth would make an observation of Messier 23 and once again add his colorful remarks to the timeline:
“A loose cluster in the space between Ophiuchus’s left leg and the bow of Sagittarius. This is an elegant sprinkling of telescopic stars over the whole field, under a moderate magnifying power; the most clustering portion is oblique, in the direction sp to nf [south preceding to north following, SW to NE], with a 7th-magnitude star in the latter portion. The place registered it that of a neat pair, of the 9th and 10th magnitudes, of a lilac hue, and about 12″ apart. This object was discovered by Messier 1764, and it precedes a rich out-cropping of the Milky Way. The place is gained by differentiating the cluster with Mu Sagittarii, from which it bears north-west, distant about 5 deg, the spot being directed to by a line from Sigma on the shoulder, through Mu at the tip of the bow.”
Remember when observing Messier 23 that it won’t slap you in the face like many objects. Basically, it looks like a stellar scattering of freckles across the face of the sky when fully-resolved. It’s actually one of those objects that’s better to view with binoculars and low power telescopes.
Locating Messier 23:
M23 can be easily found with binoculars about a finger’s width north and two finger widths west of Mu Sagittarii. Or, simply draw a mental line between the top star in the teapot lid (Lambda) and Xi Serpentis. You’ll find a slight compression in the star field about halfway between these two stars that shows up as an open cluster with binoculars.
Using a finderscope, the object will appear nicely as a hazy spot. And for those using telescopes of any size, you’ll need to use fairly low magnification to help set this cluster apart from the surrounding star field, and it will resolve well to almost all instruments.
And here are the quick facts on this object to help you get started:
Object Name: Messier 23 Alternative Designations: M23, NGC 6494 Object Type: Open Star Cluster Constellation: Sagittarius Right Ascension: 17 : 56.8 (h:m) Declination: -19 : 01 (deg:m) Distance: 2.15 (kly) Visual Brightness: 6.9 (mag) Apparent Dimension: 27.0 (arc min)
Size comparison between the New Glenn and all other rockets currently in operations (with the Saturn V for comparison). Credit: Blue Origin
Space exploration is becoming a lucrative domain for private aerospace companies (aka. the NewSpace industry). With opportunities for launch and resupply services growing, costs dwindling, and the cancellation of the Space Shuttle Program, private companies have been stepping up in recent years to provide their own launch vehicles and services to fill the gap.
Take Jeff Bezos, for example. Back in 2000, the founder of Amazon.com created Blue Origin to fulfill his lifelong dream of colonizing space. For years, Bezos and the company he founded have been working to produce their own fleet of reusable rockets. And as of the morning of Monday, Sept. 12th, he unveiled their newest and heaviest rocket – the New Glenn.
Much like SpaceX, Blue Origin has been committed to the creation of reusable rocket technology. This was made clear with the development of the New Shepard suborbital rocket, which was unveiled in 2006. Named in honor of the first American astronaut to go into space (Alan Shepard), this rocket made its first flight in April of 2015 and has had an impressive record, nailing four out of five soft landings in the space of just over a year.
New Shepard comes in for a landing with drag brakes and landing gear deployed. Credit: Blue Origin.
With the New Glenn – named in honor of astronaut John Glenn, the first American astronaut to orbit the Earth – the company now intends to take the next step, offering launch services beyond Low-Earth Orbit (LEO) and for crewed missions. As Bezos said during the press conference:
“New Glenn is designed to launch commercial satellites and to fly humans into space. The three-stage variant-with its high specific impulse hydrogen upper stage—is capable of flying demanding beyond-LEO missions.”
According to Bezos, Blue Origin will have both a two-stage and three-stage variant of the rocket. Whereas the two-stage will provide heavier lift capacity to LEO, the three-stage will be able to reach further, and will the company’s go-to when sending crewed missions into space. Work on the rocket began back in 2012, and the company hopes to make their first launch prior to 2020.
As Bezos said during the unveiling, this rocket carries on in the same tradition that inspired the creation of the New Shepard:
“Building, flying, landing, and re-flying New Shepard has taught us so much about how to design for practical, operable reusability. And New Glenn incorporates all of those learnings. Named in honor of John Glenn, the first American to orbit Earth, New Glenn is 23 feet in diameter and lifts off with 3.85 million pounds of thrust from seven BE-4 engines. Burning liquefied natural gas and liquid oxygen, these are the same BE-4 engines that will power United Launch Alliance’s new Vulcan rocket.”
A United Launch Alliance (ULA) Delta IV rocket launching from Cape Canaveral Air Force Station, Fl, on July 23rd, 2015. Credit: Ken Kremer/kenkremer.com
The rocket will have a sea-level thrust of 1.746 million kg (3.85 million lbs), placing it ahead of the Delta IV Heavy – which has a sea-level thrust of about 900,000 kg (2 million lbs) – but behind the 2.268 million kg (5 million lbs) of the Falcon Heavy. Both variants will be powered by BE-4 engines, which are also manufactured by Blue Origin. The third-stage also employs a single vacuum-optimized BE-3 engine that burns liquid hydrogen and liquid oxygen.
However, the most interesting facet of the New Glenn is the fact that it will be reusable, with its first stage providing braking thrust and deployable legs (similar to the Falcon 9). In creating a heavy lift rocket that employs a retrievable first-stage, Blue Origin has signaled its intent to give SpaceX a run for its money when it comes to the development of reusable rocket technology.
It is also likely to raise the company’s profile, which has so far been limited to conducting sub-orbital research for NASA and dabbling in the space-tourism industry. But once the New Glenn is up and running, it is likely to begin securing contracts to provide resupply services the ISS, as well as contracts with companies and research institutions to place satellites in orbit.
The Falcon Heavy, once operational, will be the most powerful rocket in the world. Credit: spacex.com
According to The Verge, Bezos also hinted that his company has another project in mind – called the New Armstrong. While no details have been given just yet, the name of this rocket is a clear allusion to the Moon Landing, and hints that the company may have designs on possible moon missions in the coming decades.
This is an exciting time for the NewSpace industry. In the coming months, SpaceX is expected to conduct the first launch of the Falcon Heavy, which will be the most powerful rocket built in the US since the retirement of the Apollo program’s Saturn V launcher. And if they keep to their current schedule, Blue Origin will be following this in a few years time with the launch of the largest rocket of the post-Apollo era.
Big rockets and big lift capacities can mean only thing: big things lie ahead of us!
Finely layered rocks within the "Murray formation" layer of lower Mount Sharp on Mars. Credit: NASA
Since its deployment in 2012 to the surface of Mars, the Curiosity rover has sent back many breathtaking images of the Red Planet. In addition to snapping photos of the comet Siding Spring and Earth from the surface, not to mention some wonderful panoramic selfies, the rover has also taken countless images that show the geology and surface features of Mars’ in stunning detail.
And with the latest photos to be released by NASA, the Curiosity rover has provided us with a wonderful look at the “Murray Buttes” region, which is in the lower part of Mount Sharp. These images were taken by the Curiosity Mast Camera (Mastcam) on Sept. 8th, and provide some lovely insight into the geological history of the region.
Using these images, the Curiosity team hopes to assemble another impressive color mosaic that will give a detailed look at the region’s rocky, desert-like landscape. As you can see from the images provided, the region is characterized by mesas and buttes, which are the eroded remnants of ancient sandstone. Much like other spots around Mount Sharp, the area is of particular interest to the Curiosity team.
Sloping buttes and layered outcrops within the “Murray formation” layer of lower Mount Sharp. Credit: NASA
For years, scientists have understood that the rock layers that form the base of Mount Sharp accumulated as a result of sediment being deposited within the ancient lake bed billions of years ago. In this respect, the geological formations are similar to those found in the desert regions of the southwestern United States.
Ashwin Vasavada, the Curiosity Project Scientist of NASA’s Jet Propulsion Laboratory, told Universe Today via email:
” The Murray Buttes region of Mars is reminiscent of parts of the American southwest because of its butte and mesa landscape. In both areas, thick layers of sediment were deposited by wind and water, eventually resulting in a “layer cake” of bedrock that then began to erode away as conditions changed. In both places, more resistant sandstone layers cap the mesas and buttes because they protect the more easily eroded, fine-grained rock underneath.
“Like at Monument Valley near the Utah-Arizona border, at Murray Buttes there are just small remnants of these layers that once covered the surface more completely. There were wind-driven sand dunes at both places, too, that now appear as cross-bedded sandstone layers. There are of course many differences between Mars and the American Southwest. For example, there were large inland seas in the Southwest, while at Gale crater there were lakes.”
These sediment layers are believed to have been laid down over the course of 2 billion years, and may have completely filled the crater at one time. Since it is widely believed that lakes and streams existed in the Gale Crater 3.3 – 3.8 billion years ago, some of the lower sediment layers may have originally been deposited on a lake bed.
A hillside outcrop with finely layered rocks within the “Murray formation” layer of lower Mount Sharp. Credit: NASA
For this reason, the Curiosity team also took drill samples from the Murray Buttes area for analysis. This began on Sept. 9th, after the rover was finished taking pictures of the area. As Vasavada explained:
“The Curiosity team is drilling regularly as the rover ascends Mount Sharp. We are drilling into the fine-grained rock that was deposited within lakes in order to see how the lake chemistry, and therefore the environment, changed over time. Curiosity drilled into the coarser sandstone that forms the upper layers of the buttes when the rover crossed the Naukluft Plateau earlier in 2016.”
After the drilling is completed, Curiosity will continue farther south and higher up Mount Sharp, leaving behind these spectacular formations. These pictures represent Curiosity‘s last stop in the Murray Buttes, where the rover has been spending the past month.
And as of this past September 11th, 2016, Curiosity has been on the planet Mars for a total of 4 years and 36 days (or 1497 Earth days; 1458 sols) since it landed on August 6th, 2012.
One has to wonder how the pareidolia folks are going to interpret these ones. After “seeing” a rat, a lizard, a doughnut, a coffin, and so forth, what’s left? Might I suggest that the top image kind of looks like a statue-column?
Stellar motions distort the future sky. Map: Bob King, Source: Stellarium
If we could transport Ptolemy, a famous astronomer who lived circa 90 – 168 A.D. in Alexandria, Egypt, he would have noticed the shift in position of Arcturus, Sirius and Aldebaran since his time. Everything else would appear virtually unchanged.
You go out and look at the stars year after year and never see any of them get up and walk away from their constellations. Take a time machine back to the days of Plato and Socrates and only careful viewing would reveal that just three of the sky’s naked eye stars had budged: Arcturus, Sirius and Aldebaran. And then only a little. Their motion was discovered by Edmund Halley in 1718 when he compared the stars’ positions then to their positions noted by the ancient Greek astronomers. In all three cases, the stars had moved “above a half a degree more Southerly at this time than the Antients reckoned them.”
NGC 4414 is a spiral galaxy that resembles our own Milky Way. I’ve drawn in the orbits of several stars. Both disk and halo stars orbit about the center, but halo stars describe long elliptical orbits that take them well beyond the disk. When a star plunges through the disk, if it happens to be relatively nearby as in the case of Arcturus, the star will appear to move relatively quickly across the sky. Both distance and the type of orbit a star has can affect how fast it moves from our perspective. Credit: NASA/ESA with orbits by the author
Stars are incredibly far away. I could throw light years around like I often do here, but the fact is, you can get a real feel for their distance by noting that during your lifetime, none will appear to move individually. The gems of the night and our sun alike revolve around the center of the galaxy. At our solar system’s distance from the center — 26,000 light years or about halfway from center to edge — it takes the sun about 225 million years to make one revolution around the Milky Way.
That’s a LONG time. The other stars we see on a September night take a similar length of time to orbit. Now divide the average lifetime of some 85 years into that number, and you’ll discover that an average star moves something like .00000038% of its orbit around the galactic center every generation. Phew, that ain’t much! No wonder most stars don’t budge in our lifetime.
This graphic, made using SkyMap software created by Chris Marriott, shows the motion of Arcturus over a span of 8,000 years.
Sirius, Aldebaran and Arcturus and several other telescopic stars are close enough that their motion across the sky becomes apparent within the span of recorded history. More powerful telescopes, which expand the scale of the sky, can see a great many stars amble within a human lifetime. Sadly, our eyes alone only work at low power!
Precession of Earth’s axis maintains its usual 23.5 degree tilt, but this causes the axis to describe a circle in the sky like a wobbling top. The photo is an animation that repeats 10 seconds, so hang in there. Credit: Wikimedia Commons
But we needn’t invest billions in building a time machine to zing to the future or past to see how the constellation outlines become distorted by the individual motions of the stars that compose them. We already have one! Just fire up a free sky charting software program like Stellarium and advance the clock. Like most such programs, it defaults to the present, but let’s look ahead. Far ahead.
If we advance 90,000 years into the future, many of the constellations would be unrecognizable. Not only that, but more locally, the precession of Earth’s axis causes the polestar to shift. In 2016, Polaris in the Little Dipper stands at the northernmost point in the sky, but in 90,000 years the brilliant star Vega will occupy the spot. Tugs from the sun and moon on Earth’s equatorial bulge cause its axis to gyrate in a circle over a period of about 26,000 years. Wherever the axis points defines the polestar.
I advanced Stellarium far enough into the future to see how radically the Big Dipper changes shape over time. Notice too that Vega will be the polestar in that distant era. Map: Bob King, Source: Stellarium
Take a look at the Big Dipper. Wow! It’s totally bent out of shape yet still recognizable. The Pointer Stars no longer quite point to Polaris, but with some fudging we might make it work. Vega stands near the pole, and being much closer to us than the rest of Lyra’s stars, has moved considerably farther north, stretching the outline of the constellation as if taffy.
Now let’s head backwards in time 92,000 years to 90,000 B.C. The Dipper then was fairly unrecognizable, with both Vega and Arcturus near the pole. Map: Bob King , Source: Stellarium
Time goes on. We look up at the night sky in the present moment, but so much came before us and much will come after. Constellations were unrecognizable in the past and will be again in the future. In a fascinating discussion with Michael Kauper of the Minnesota Astronomical Society at a recent star party, he described the amount of space in and between galaxies as so enormous that “we’re almost not here” in comparison. I would add that time is so vast we’re likewise almost not present. Make the most of the moment.
The recent flight of Aistechsat-1. Image credit: Zero2Infinity.
Is there a better way to get to space? Current traditional methods using expendable rockets launching from the surface of the Earth are terribly inefficient. About 90% of the bulk and mass of what you see on the launch pad is expended in the first few minutes of the mission, just getting the tiny payload above the murk of Earth’s atmosphere and out of the planet’s gravity well.
One idea that’s been out there for a while is to loft a launch platform into the upper atmosphere, and simply start from there. One Spanish-based company named Zero2infinity plans to do just that.
Recently, on May 20th, 2016, Zero2infinity lofted Aistech’s first satellite into the upper atmosphere, aboard its Sub-Orbital Platform in Near Space balloon system. Zero2infinity uses these Near Space balloons to carry client payloads up above 99% of the Earth’s atmosphere. This is a cheap and effective way to get payloads into a very space-like environment.
These near Space Balloon platforms typically reach an altitude of 28 kilometres (17 miles) above the surface of the Earth. For reference, the Armstrong Line (where the boiling point of water equals human body temperature) starts 18 kilometers up, and the Kármán line — the internationally recognized boundary where space begins — starts at an altitude of 100 kilometers, or 62 miles up.
Most satellites in Low Earth Orbit (LEO) go around the Earth 300 to 600 kilometers up, and the International Space Station resides in a 400 by 400 kilometer standard orbit.
The mission of Aistechsat-1 is to “provide thermal images of the Earth and also help with maritime and aeronautical tracking,” Zero2infinity representative Iris Silverio told Universe Today via email. Zero2infinity plans on conducting another balloon test with Aistechsat-1 later this month on an as yet to be announced date. The final decision all hinges on the weather and the wind speeds aloft.
Aistech envisions a constellation of 25 such nanosatellites encircling the planet.
Zero2infinity also has a grander vision: eventually launching satellites into Low Earth Orbit via balloon. Known as Bloostar, this system would loft a three stage rocket with the company’s existing and proven Near Space balloon technology. The ‘launch’ would occur high in the upper atmosphere, as the engines take over to get the payload into orbit.
Getting there; the Bloostar approach to low Earth orbit. Image credit: Zero2Infinity.
The idea is certainly attractive. Dubbed a ‘shortcut to space,’ the three engine booster rings depicted are a fraction of the size of typical rocket stages. The toroid ring-shaped stages are simply nestled one inside the other, like Russian dolls. Zero2infinity also envisions scaling its ‘Bloon’ platform for micro and nano payloads… and I’ll bet that a Bloostar atmospheric launch will be an interesting spectacle to watch with binoculars from the ground, especially around dawn or dusk.
Another possible advantage includes a much more spacious payload nose cone, meaning no more folding of satellites for launch and unfolding them in orbit. More than a few payloads have suffered setbacks because of this, including the Galileo mission to Jupiter, whose main antenna failed to unfurl completely in 1990.
According to an email discussion with Zero2infinity representative Silverio, the first commercial Bloostar launch is set for 2019, with possible orbital trials starting as early as 2018. Bloostar deployments will occur off the coast of the Canary Islands in the Atlantic. The initial Bloostar launcher will deploy payloads up to 75 kilograms in a 600 kilometer orbit around the Earth.
Rise of the Rockoons
The idea of conducting launches via balloon, known as a ‘rockoon,’ has been around for a while. Thus far, only sub-orbital launches have been conducted in this manner.
A Deacon rockoon shortly after a U.S. Navy shipboard launch. Public Domain image.
The first balloon-based launch of a rocket occurred on August 9th, 1953, when a Deacon rockoon successfully carried out a sub-orbital launch high over the Atlantic Ocean. Though several companies have kicked around the idea of launching an orbital satellite via balloon-based platform, Zero2infinity might just be the first to actually accomplish it. The United States Department of Defense has considered the idea of launching satellites (and satellite-killing missiles) via the U.S. Air Force’s high flying F-15 Eagle aircraft. Orbital Sciences does currently use its Pegasus-XL rocket carried aloft by a L1011 aircraft to place satellites in orbit. That’s how NASA’s NuSTAR X-ray telescope got into space in 2012.
There is one main problem facing balloon-based space launches: weather. Unlike aircraft, balloons are often at the whims of the winds aloft, and sometimes stubbornly refuse to go where you want them to. Often, an orbital launch will need to target a precise azimuth heading, a tricky sort of pointing to do from underneath a balloon. Still, we’ve already seen precedent for overcoming this in the effective pointing of balloon-based telescopes, such as the BLAST telescope.
Bloostar might just provide an innovative and cost-effective way to head into orbit, very soon.
-Check out this 2014 article from Universe Today on Zero2Infinity.
