Posted on by Matt Williams

Astronomers Find One of the Oldest Stars in the Milky Way

A recent survey has discovered the first stars of the Milky Way. Credit: Gabriel Pérez, SMM (IAC)

According to modern cosmological models, the Universe began in a cataclysm event known as the Big Bang. This took place roughly 13.8 billion years ago, and was followed by a period of expansion and cooling. During that time, the first hydrogen atoms formed as protons and electrons combined and the fundamental forces of physics were born. Then, about 100 million years after the Big Bang, that the first stars and galaxies began to form.

The formation of the first stars was also what allowed for the creation of heavier elements, and therefore the formation of planets and all life as we know it. However, until now, how and when this process took place has been largely theoretical since astronomers did not know where the oldest stars in our galaxy were to be found. But thanks to a new study by a team of Spanish astronomers, we may have just found the oldest star in the Milky Way!

The study, titled “J0815+4729: A chemically primitive dwarf star in the Galactic Halo observed with Gran Telescopio Canarias“, recently appeared in The Astrophysical Journal Letters. Led by David S. Aguado of the Instituto de Astrofisica de Canarias (IAC), the team included members from the University of La Laguna and the Spanish National Research Council (CSIC).

Artist’s impression of the Milky Way Galaxy. Credit: NASA/JPL-Caltech/R. Hurt (SSC-Caltech)

This star is located roughly 7,500 light years from the Sun, and was found in the halo of the Milky Way along the line of sight to the Lynx constellation. Known as J0815+4729, this star is still in its main sequence and has a low mass, (around 0.7 Solar Masses), though the research team estimates that it has a surface temperature that is about 400 degrees hotter – 6,215 K (5942 °C; 10,727 °F) compared to 5778 K (5505 °C; 9940 °F).

For the sake of their study, the team was looking for a star that showed signs of being metal-poor, which would indicate that it has been in its main sequence for a very long time. The team first selected J0815+4729 from the Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey (SDSS-III/BOSS) and then conducted follow-up spectroscopic investigations to determine its composition (and hence its age).

This was done using the Intermediate dispersion Spectrograph and Imaging System (ISIS) at the William Herschel Telescope (WHT) and the Optical System for Imaging and low-intermediate-Resolution Integrated Spectroscopy (OSIRIS) at Gran Telescopio de Canarias (GTC), both of which are located at the Observatorio del Roque de los Muchachos on the island of La Palma.

Consistent with what modern theory predicts, the star was found in the Galactic halo – the extended component of our galaxy that reaches beyond the galactic disk (the visible portion). It is in this region that the oldest and most metal-poor stars are believed to be found in galaxies, hence why the team was confident that a star dating back to the early Universe would be found here.

The William Herschel Telescope, part of the Isaac Newton group of telescopes, located on Canary Island. Credit: ing.iac.es

As Jonay González Hernández – a professor from the University of La Laguna, a member of the IAC and a co-author on the paper – explained in an IAC press release:

“Theory predicts that these stars could use material from the first supernovae, whose progenitors were the first massive stars in the galaxy, around 300 million years after the Big Bang. In spite of its age, and its distance away from us, we can still observe it.”

Spectra obtained by both the ISIS and OSIRIS instruments confirmed that the star was poor in metals, indicating that J0815+4729 has only one-millionth of the calcium and iron that the Sun contains. In addition, the team also noticed that the star has a higher carbon content than our Sun, accounting for almost 15% percent of its solar abundance (i.e. the relative abundance of its elements).

In short, J0815+4729 may be the most iron-poor and carbon-rich star currently known to astronomers. Moreover, finding it was rather difficult since the star is both weak in luminosity and was buried within a massive amount of SDSS/BOSS archival data. As Carlos Allende Prieto, another IAC researcher and a co-author on the paper, indicated:

“This star was tucked away in the database of the BOSS project, among a million stellar spectra which we have analysed, requiring a considerable observational and computational effort. It requires high-resolution spectroscopy on large telescopes to detect the in the star, which can help us to understand the first supernovae and their progenitors.”

In the near future, the team predicts that next-generation spectrographs could allow for further research that would reveal more about the star’s chemical abundances. Such instruments include the HORS high-resolution spectrograph, which is presently in a trial phase on the Gran Telescopio Canarias (GTC).

“Detecting lithium gives us crucial information related to Big Bang nucleosynthesis,” said Rafael Rebolo, the director of the IAC and a coauthor of the paper. “We are working on a spectrograph of high-resolution and wide spectral range in order to measure the detailed chemical composition of stars with unique properties such as J0815+4719.”

These future studies are sure to be a boon for astronomers and cosmologists. In addition to being a chance to study stars that formed when the Universe was still in its infancy, they could provide new insight into the early stages of the universe, the formation of the first stars, and the properties of the first supernovae. In other words, they would put us a step closer to know how the Universe as we know it formed and evolved.

Further Reading: IAC, The Astrophysical Journal Letters

Posted on by Matt Williams

The New Earth-Sized Planet Hunting Telescope ExTrA is Now Online

The ExTrA telescopes are sited at ESO’s La Silla Observatory in Chile. They will be used to search for and study Earth-sized planets orbiting nearby red dwarf stars. Credit: ESO/Emmanuela Rimbaud

Ever since the Kepler space telescope began discovering thousands of exoplanets in our galaxy, astronomers have been eagerly awaiting the day when next-generation missions are deployed. These include the much-anticipated James Webb Space Telescope, which is scheduled to take to space in 2019, but also the many ground-based observatories that are currently being constructed.

One of these is the Exoplanets in Transits and their Atmospheres (ExTrA) project, which is the latest addition to the ESO’s La Silla Observatory in Chile. Using the Transit Method, this facility will rely on three 60-centimeter (23.6 in) telescopes to search for Earth-sized exoplanets around M-type (red dwarf) stars in the Milky Way Galaxy. This week, the facility began by collecting its first light.

The Transit Method (aka. Transit Photometry) consists of monitoring stars for periodic dips in brightness. These dips are caused by planets passing in front of the star (aka. transiting) relative to the observer. In the past, detecting planets around M-type stars using this method has been challenging since red dwarfs are the smallest and dimmest class of star in the known Universe and emit the majority of their light in the near-infrared band.

Artist’s impression of rocky exoplanets orbiting Gliese 832, a red dwarf star just 16 light-years from Earth. Credit: ESO/M. Kornmesser/N. Risinger (skysurvey.org).

However, these stars have also proven to be treasure trove when it comes to rocky, Earth-like exoplanets. In recent years, rocky planets have been discovered around star’s like Proxima Centauri and Ross 128, while TRAPPIST-1 had a system of seven rocky planets. In addition, there have been studies that have indicated that potentially-habitable, rocky planets could be very common around red dwarf stars.

Unlike other facilities, the ExTrA project is well-suited to conduct surveys for planets around red dwrfs because of its location on the outskirts of the Atacama Desert in Chile. As Xavier Bonfils, the project’s lead researcher, explained:

“La Silla was selected as the home of the telescopes because of the site’s excellent atmospheric conditions. The kind of light we are observing – near-infrared – is very easily absorbed by Earth’s atmosphere, so we required the driest and darkest conditions possible. La Silla is a perfect match to our specifications.”

In addition, the ExTrA facility will rely on a novel approach that involves combining optical photometry with spectroscopic information. This consists of its three telescopes collecting light from a target star and four companion stars for comparison. This light is then fed through optical fibers into a multi-object spectrograph in order to analyze it in many different wavelengths.

The ExTrA telescopes are sited at ESO’s La Silla Observatory in Chile. Credit: ESO/Petr Horálek

This approach increases the level of achievable precision and helps mitigate the disruptive effect of Earth’s atmosphere, as well as the potential for error introduced by instruments and detectors. Beyond the goal of simply finding planets transiting in front of their red dwarf stars, the ExTrA telescopes will also study the planets it finds in order to determine their compositions and their atmospheres.

In short, it will help determine whether or not these planets could truly be habitable. As Jose-Manuel Almenara, a member of the ExTrA team, explained:

“With ExTrA, we can also address some fundamental questions about planets in our galaxy. We hope to explore how common these planets are, the behaviour of multi-planet systems, and the sorts of environments that lead to their formation,”

The potential to search for extra-solar planets around red dwarf stars is an immense opportunity for astronomers. Not only are they the most common star in the Universe, accounting for 70% of stars in our galaxy alone, they are also very long-lived. Whereas stars like our Sun have a lifespan of about 10 billion years, red dwarfs are capable of remaining in their main sequence phase for up to 10 trillion years.

Artist’s impression of Proxima b, which was discovered using the Radial Velocity method. Credit: ESO/M. Kornmesser

For these reasons, there are those who think that M-type stars are our best bet for finding habitable planets in the long run. At the same time, there are unresolved questions about whether or not planets that orbit red dwarf stars can stay habitable for long, owing to their variability and tendency to flare up. But with ExTrA and other next-generation instruments entering into service, astronomers may be able to address these burning questions.

As Bonfils excitedly put it:

“With the next generation of telescopes, such as ESO’s Extremely Large Telescope, we may be able to study the atmospheres of exoplanets found by ExTra to try to assess the viability of these worlds to support life as we know it. The study of exoplanets is bringing what was once science fiction into the world of science fact.”

ExTrA is a French project funded by the European Research Council and the French Agence National de la Recherche and its telescopes will be operated remotely from Grenoble, France. Also, be sure to enjoy this video of the ExTrA going online, courtesy of the ESOcast:

Further Reading: ESO

Posted on by Matt Williams

86 Stars Just got Official Names from the IAU

The two brightest stars of the Centaurus constellation - (left) Alpha Centauri and (right) Beta Centauri. The faint red star in the center of the red circle is Proxima Centauri. Credit: Wikipedia Commons/Skatebiker

What springs to mind when we think of the most commonly-known stars in the night sky? Chances are, it would be stars like Sirius, Vega, Deneb, Rigel, Betelgeuse, Polaris, and Arcturus – all of which derive their names from Arabic, Greek or Latin origins. Much like the constellations, these names have been passed down from one astronomical tradition to another and were eventually adopted by the International Astronomical Union (IAU).

But what about the astronomical traditions of Earth’s many, many other cultures? Don’t the names they applied to heavens also deserve mention? According to the IAU, they do indeed! After a recent meeting by the Working Group on Star Names (WGSN), the IAU formally adopted 86 new names for stars drawn largely from the Australian Aboriginal, Chinese, Coptic, Hindu, Mayan, Polynesian, and South African peoples.

The WGSN is an international group of astronomers tasked with cataloging and standardizing the star names used by the international astronomical community. This job entails establishing IAU guidelines for the proposals and adoption of names, searching through international historical and literary sources for star names, adopting names of unique historical and cultural value, and maintaining and disseminating the official IAU star catalog.

Star map painting by Senior Wardaman Elder Bill Yidumduma Harney, featuring the Milky Way, the Moon, and ancestor spirits. Credit: IAU

Last year, the WGSN approved the names for 227 stars. With these latest additions, the catalog now contains the names of 313 stars. Unlike standard star catalogs containing millions or billions of stars designated using strings of letters and numbers, the IAU star catalog consists of bright stars with proper names derived from historical and cultural sources. As Eric Mamajek, chair and organizer of the WGSN, indicated in an IAU press release:

“The IAU Working Group on Star Names is researching traditional star names from cultures around the world and adopting unique names and spellings to avoid confusion in astronomical catalogues and star atlases. These names help ensure that intangible astronomical heritage from skywatchers around the world, and across the centuries, are preserved for use in an era of exoplanetary systems.”

A total of eleven Chinese star names were incorporated into the catalog, three of which are derived from the “lunar mansions” of traditional Chinese astronomy. This refers to vertical strips of the sky that act as markers for the progress of the Moon across the sky in the course of a year. In this sense, they provide a basis for the lunar calendar in the same way that the zodiac worked for Western calendars.

Two names were derived from the ancient Hindu lunar mansions as well. These stars are Revati and Bharani, which designate Zeta Piscium and 41 Arietis, respectively. In addition to being a lunar mansion, Revati was also the daughter of King Kakudmi in Hindu mythology and the consort of the God Balarama – the elder brother of Krishna. On the other hand, Bharani is the name for the second lunar mansion in Hindu astronomy and is ruled by Shurka (Venus).

Position of the Hindu Nakshatra Mandala, the “lunar mansions” in Hindu mythology. Credit: Wikipedia Commons/ Kishorekumar 62

Beyond the astronomical traditions of India and China, there are also two names adopted from the Khoikhoi people of South Africa and the people of Tahiti – Xamidimura and Pipirima. These names were approved for Mu¹ and Mu² Scorpii, the stars that make up a binary system located in the constellation of Scorpius. Xamidimura is derived from the Khoikhoi name for the star xami di mura – literally “eyes of the lion.”

Pipirima refers to the inseparable twins from Tahitian mythology, a boy and a girl who ran away from their parents and became stars in the night sky. Then you have the Yucatec Mayan name Chamukuy, a small bird that now designates the star Theta-2 Tauri, which is located in the Hyades star cluster in Taurus.

Four Aboriginal Australian star names were also added to the catalog, including the Wardaman names Larawag, Ginan, and Wurren and the Boorong name Unurgunite. These names now designate Epsilon Scorpii, Epsilon Crucis, Zeta Pheonicis, and Sigma Canis Majoris, respectively. Given that Aboriginal Australians have traditions that go back as far as 65,000 years, these names are some of the oldest in existence.

The brightest star to receive a new name was Alsephina, which was given to the star previously designated as Delta Velorum. The name stems from the Arabic name al-safinah (“the ship”), which refers to the ancient Greek constellation Argo Navis (the ship of the Argonauts). This name goes back to the 10th-century Arabic translation of the Almagest, which was compiled by Ptolemy in the 2nd century CE.

Artist’s concept of exoplanets orbiting a red dwarf star. Credit: NASA/JPL-Caltech

The new catalog also includes Barnard’s Star, a name that has been in common usage for about a century but was never an official designation. This red dwarf star, which is less than six light-years from Earth, is named after the astronomer who discovered it – Edward Emerson Barnard – in 1916. It now joins Alsafi (Sigma Draconis), Achird (Eta Cassiopeiae), and Tabit (Pi-3 Orionis) as being one of four nearby stars whose proper names were approved in 2017.

One of the hallmarks of modern astronomy is how naming conventions are moving away from traditional Western and Classical sources and broadening to become more worldly. In addition to being a more inclusive, multicultural approach, it reflects the spirit of modern astronomical research and space exploration, which is characterized by international cooperation.

Someday, assuming our progeny ever go forth and begin to colonize distant star systems, we can expect that the stars and planets they come to know will have names that reflect the diverse astronomical traditions of Earth’s many cultures.

Further Reading: IAU

Posted on by Matt Williams

A Brown Dwarf Prevented a Regular Star from Going Through its Full Life Cycle

A team of Brazilian scientists recently observed a binary star system consisting of a white dwarf and a brown dwarf companion. Credit: FAPESP

Eclipsing binary star systems are relatively common in our Universe. To the casual observer, these systems look like a single star, but are actually composed of two stars orbiting closely together. The study of these systems offers astronomers an opportunity to directly measure the fundamental properties (i.e. the masses and radii) of these systems respective stellar components.

Recently, a team of Brazilian astronomers observed a rare sight in the Milky Way – an eclipsing binary composed of  a white dwarf and a low-mass brown dwarf. Even more unusual was the fact that the white dwarf’s life cycle appeared to have been prematurely cut short by its brown dwarf companion, which caused its early death by slowly siphoning off material and “starving” it to death.

The study which detailed their findings, titled “HS 2231+2441: an HW Vir system composed by a low-mass white dwarf and a brown dwarf“, was recently published the Monthly Notices of the Royal Astronomical Society. The team was led by Leonardo Andrade de Almeida, a postdoctoral fellow from the University of São Paolo’s Institute of Astronomy, Geophysics, and Atmospheric Sciences (IAG-USP), along with members from the National Institute for Space Research (MCTIC), and the State University of Feira de Santana.

The Observatorio del Roque de los Muchachos, located on the island of La Palma. Credit: IAC

For the sake of their study, the team conducted observations of a binary star system between 2005 and 2013 using the Pico dos Dias Observatory in Brazil. This data was then combined with information from the William Herschel Telescope, which is located in the Observatorio del Roque de los Muchachos on the island of La Palma. This system, known as of HS 2231+2441, consists of a white dwarf star and a brown dwarf companion.

White dwarfs, which are the final stage of intermediate or low-mass stars, are essentially what is left after a star has exhausted its hydrogen and helium fuel and blown off its outer layers. A brown dwarf, on the other hand, is a substellar object that has a mass which places it between that of a star and a planet. Finding a binary system consisting of both objects together in the same system is something astronomers don’t see everyday.

As Leonardo Andrade de Almeida explained in a FAPESP press release, “This type of low-mass binary is relatively rare. Only a few dozen have been observed to date.”

This particular binary pair consists of a white dwarf that is between twenty to thirty percent the Sun’s mass – 28,500 K (28,227 °C; 50,840 °F) – while the brown dwarf is roughly 34-36 times that of Jupiter. This makes HS 2231+2441 the least massive eclipsing binary system studied to date.

This artist’s impression shows an eclipsing binary star system. Credit: ESO/L. Calçada.

In the past, the primary (the white dwarf) was a normal star that evolved faster than its companion since it was more massive. Once it exhausted its hydrogen fuel, its formed a helium-burning core. At this point, the star was on its way to becoming a red giant, which is what happens when Sun-like stars exit their main sequence phase. This would have been characterized by a massive expansion, with its diameter exceeding 150 million km (93.2 million mi).

At this point, Almeida and his colleagues concluded that it began interacting gravitationally with its secondary (the brown dwarf). Meanwhile, the brown dwarf began to be attracted and engulfed by the primary’s atmosphere (i.e. its envelop), which caused it it lose orbital angular momentum. Eventually, the powerful force of attraction exceeded the gravitational force keeping the envelop anchored to its star.

Once this happened, the primary star’s outer layers began to be stripped away, exposing its helium core and sending massive amounts of matter to the brown dwarf. Because of this loss of mass, the remnant effectively died, becoming a white dwarf. The brown dwarf then began orbiting its white dwarf primary with a short orbital period of just three hours. As Almeida explained:

“This transfer of mass from the more massive star, the primary object, to its companion, which is the secondary object, was extremely violent and unstable, and it lasted a short time… The secondary object, which is now a brown dwarf, must also have acquired some matter when it shared its envelope with the primary object, but not enough to become a new star.”

Artist’s impression of a brown dwarf orbiting a white dwarf star. Credit: ESO

This situation is similar to what astronomers noticed this past summer while studying the binary star system known as WD 1202-024. Here too, a brown dwarf companion was discovered orbiting a white dwarf primary. What’s more, the team responsible for the discovery indicated that the brown dwarf was likely pulled closer to the white dwarf once it entered its Red Giant Branch (RGB) phase.

At this point, the brown dwarf stripped the primary of its atmosphere, exposing the white dwarf remnant core. Similarly, the interaction of the primary with a brown dwarf companion caused premature stellar death. The fact that two such discoveries have happened within a short period of time is quite fortuitous. Considering the age of the Universe (which is roughly 13.8 billion years old), dead objects can only be formed in binary systems.

In the Milky Way alone, about 50% of low-mass stars exist as part of a binary system while high mass stars exist almost exclusively in binary pairs. In these cases, roughly three-quarters will interact in some way with a companion – exchanging mass, accelerating their rotations, and eventually en merging.

As Almeida indicated, the study of this binary system and those like it could seriously help astronomers understand how hot, compact objects like white dwarfs are formed. “Binary systems offer a direct way of measuring the main parameter of a star, which is its mass,” he said. “That’s why binary systems are crucial to our understanding of the life cycle of stars.”

It has only been in recent years that low-mass white dwarf stars were discovered. Finding binary systems where they coexist with brown dwarfs – essentially, failed stars – is another rarity. But with every new discovery, the opportunities to study the range of possibilities in our Universe increases.

Further Reading: São Paulo Research Foundation, MNRAS

Posted on by Nancy Atkinson

Can Astronauts See Stars From the Space Station?

Stars and the limb of Earth seen in the background of the International Space Station on July 29, 2017. Credit: NASA/Jack Fischer.

I’ve often been asked the question, “Can the astronauts on the Space Station see the stars?” Astronaut Jack Fischer provides an unequivocal answer of “yes!” with a recent post on Twitter of a timelapse he took from the ISS. Fischer captured the arc of the Milky Way in all its glory, saying it “paints the heavens in a thick coat of awesome-sauce!”

But, you might be saying, “how can this be? I thought the astronauts on the Moon couldn’t see any stars, so how can anyone see stars in space?”

John W. Young on the Moon during Apollo 16 mission. Charles M. Duke Jr. took this picture. The LM Orion is on the left. April 21, 1972. Credit: NASA

It is a common misconception that the Apollo astronauts didn’t see any stars. While stars don’t show up in the pictures from the Apollo missions, that’s because the camera exposures were set to allow for good images of the bright sunlit lunar surface, which included astronauts in bright white space suits and shiny spacecraft. Apollo astronauts reported they could see the brighter stars if they stood in the shadow of the Lunar Module, and also they saw stars while orbiting the far side of the Moon. Al Worden from Apollo 15 has said the sky was “awash with stars” in the view from the far side of the Moon that was not in daylight.

Just like stargazers on Earth need dark skies to see stars, so too when you’re in space.

The cool thing about being in the ISS is that astronauts experience nighttime 16 times a day (in 45 minute intervals) as they orbit the Earth every 90 minutes, and can have extremely dark skies when they are on the “dark” side of Earth. Here’s another recent picture from Fischer where stars can be seen:

For stars to show up in any image, its all about the exposure settings. For example, if you are outside (on Earth) on a dark night and can see thousands of stars, if you just take your camera or phone camera and snap a quick picture, you’ll just get a darkness. Earth-bound astrophotographers need long-exposure shots to capture the Milky Way. Same is true with ISS astronauts: if they take long-exposure shots, they can get stunning images like this one:

This long exposure image of the night sky over Earth was taken on August 9, 2015 by a member of the Expedition 44 crew on board the International Space Station. Credit: NASA.

This image, set to capture the bright solar arrays and the rather bright Earth (even though its in twilight) reveals no stars:

In this timelapse of Earth at night, a few stars show up, but again, the main goal here was to have the camera capture the Earth:

Universe Today’s Bob King has a good, detailed explanation of how astronauts on the ISS can see stars on his Astro Bob blog Astrophysicist . Brian Koberlein explains it on his blog, here.

You can check out all the images that NASA astronauts take from the ISS on the “Astronaut Photography of Earth” site, and almost all the ISS astronauts and cosmonauts have social media accounts where they post pictures. Jack Fischer, currently on board, tweets great images and videos frequently here.

Posted on by Bob King

Saturn Rides Bareback On The Galactic Dark Horse

Credit: Bob King

The bright dot is Saturn and it shines on the back of the Galactic Dark Horse, a collection of dark nebulae in the constellation Ophiuchus that resembles a prancing horse. The head is to the right with a wisp of a tail to the left. The photo, taken on June 20, 2017, has been turned 90° to the right, so the horse stands upright. Credit: Bob King

I didn’t notice it with the naked eye, but as soon as the time exposure ended and I looked at the camera’s back display, there it was — Saturn riding barebacked on the Galactic Dark Horse! The horse, more of a prancing pony, is a collection of dark nebulae in the southern sky beautifully placed for viewing on late June evenings. The Dark Horse is part of the Great Rift, a dark gap that splits the band of the Milky Way in half, starting at the Northern Cross and extending all the way down to the “Teapot” of Sagittarius in the south.

The Great Rift appears to unzip the summer Milky Way right down the middle. Saturn and the Dark Horse are seen at lower right. Credit: Bob King

While appearing to be little more than empty, starless space, in reality the Rift consists of enormous clouds of cosmic dust and gas in the plane of the galaxy called dark nebulae that blot out the light of more distant stars. If you could suck it all up with a monster vacuum cleaner and expose the billions of stars otherwise hidden, the Milky Way would cast obvious shadows — even suburban skywatchers would routinely see it.

Saturn dominates the scene at left center in this photo taken on June 20. To its right you can see the prancing pony standing on its tail with legs sticking out to the right. Several bright Milky Way star clouds are also visible including the Small Sagittarius Star Cloud (left) and the Large Sagittarius Star Cloud below and left of Saturn. Antares in Scorpius is at upper right. Can you find the firefly that flashed during the exposure? Credit: Bob King

Tiny dust particles spewed by older, evolved stars and exploding supernovas have been settling in the plane of the galaxy since its birth 13.2 billion years ago. While the dust is sparse, it adds up over the light years to form a thick, dark band silhouetted against the more distant stars. Gravity has been at work on the dust since the earliest days, compressing the denser clumps into new stars and star clusters. But much raw material remains. Within the curdles of dark nebulae, astronomers use dust-penetrating infrared and radio telescopes to watch new stars in the process of incubation.

Dense cores of dust within the Pipe Nebula are collapsing to form new stars. We can’t see them yet because of obscuring dust. The left end of the Pipe forms the long back leg and rump of the Dark Horse. The much smaller Snake Nebula (shaped like the letter “S”) is visible at top center. Credit and copyright: Yuri Beletsky

There are more obvious parts of the Rift to the naked eye but few conjure up as striking an image as the Dark Horse, located about one outstretched fist to the left of the Scorpius’ brightest star, Antares. Saturn sits astride the horse’s back or eastern side. While it’s fun to see the horse as a single figure, astronomers catalog the various body parts as individual dark nebulae with separate numbers and even names. The largest part of the horse, the hind leg, is nicknamed the Pipe Nebula and lies 600-700 light years away. The Pipe is further subdivided into B59, B72, B77 and B78, from a survey of dark nebulae by early 20th century American astronomer E.E. Barnard.

You’ll need dark skies and averted vision to spot the Dark Horse. Let Saturn and Antares be your guides. The nebula is highest in the sky around 12:30 a.m. in late June as shown in the map above. Latitude shown is 40° North. Created with Stellarium

While the dark horse shows up well in time-exposure photos, you’ll need dark, rural skies to view it with the naked eye. It’s only a couple fists high for those of us living in the northern U.S. and southern Canada, but considerably higher up from the southern states and points south. The figure is large but faint, about 10° long by 7° wide, and stands due south and highest in the sky around 12:30 a.m. in late June. Allow your eyes time to fully dark adapt beforehand. Try for the dark rump and hind leg first then work from there to fill in the rest of the horse.

If we could see the Milky Way galaxy edge-on from afar, it would look similar to NGC 891 in Andromeda. Both have long bands of interstellar dust along their equators that appear dark against the bright, starry backdrop. Credit: Hunter Wilson

Once I knew what to look for, I could fleetingly see the entire horse with its various protrusions as a subtle darkness against the brighter Milky Way. Averted vision, the technique of playing your eye around the subject rather than staring directly at it, helped make it happen. Wide-field binoculars will show it easily and in greater detail against a fabulously rich star field.

The best time to horse around under the Milky Way happens from now till the end of the month, when the bright Moon sends the critter into hiding.

Posted on by Bob King

Star-travel 5 Million Years Into The Milky Way’s Future

Credit: ESA/Gaia/DPAC


Two Million Stars on the Move

Gaze into Gaia’s crystal ball and you will see the future. This video shows the motion of 2,057,050 stars in the coming 5 million years from the Tycho-Gaia Astrometric Solution sample, part of the first data release of European Space Agency’s Gaia mission.

Gaia is a space observatory parked at the L2 Lagrange Point, a stable place in space a million miles behind Earth as viewed from the Sun. Its mission is astrometry: measuring the precise positions, distances and motion of 1 billion astronomical objects (primarily stars) to create a three-dimensional map of the Milky Way galaxy. Gaia’s radial velocity measurements — the motion of stars toward or away from us —  will provide astronomers with a stereoscopic and moving-parts picture of about 1% of the galaxy’s stars.

Think about how slowly stars move from the human perspective. Generations of people have lived and died since the days of ancient Greece and yet the constellations outlines and naked eye stars appear nearly identical today as they did then. Only a few stars — Arcturus, Sirius, Aldebaran — have moved enough for a sharp-eyed observer of yore to perceive their motion.

Given enough time, stars do change position, distorting the outlines of the their constellations. This view shows the sky looking north in 91,000 A.D. Both Lyra and the Big Dipper are clearly bent out of shape! Created with Stellarium

We know that stars are constantly on the move around the galactic center. The Sun and stars in its vicinity orbit the core at some half-million miles an hour, but nearly all are so far away that their apparent motion has barely moved the needle over the time span of civilization as we know it.

This video shows more than 2 million stars from the TGAS sample, with the addition of 24,320 bright stars from the Hipparcos Catalogue that weren’t included in Gaia’s first data release back in September 2016. The video starts from the positions of stars as measured by Gaia between 2014 and 2015, and shows how these positions are expected to evolve in the future, based on the stars’ proper motions or direction of travel across space.

This frame will help you get your footing as you watch the video. Orion (at right) and the Alpha Persei stellar association and Pleiades (at left) are shown. Credit: ESA/Gaia/DPAC

Watching the show

The frames in the video are separated by 750 years, and the overall sequence covers 5 million years. The dark stripes visible in the early frames reflect the way Gaia scans the sky (in strips) and the early, less complete database. The artifacts are gradually washed out as stars move across the sky.

Using the map above to get oriented, it’s fun to watch Orion change across the millennia. Betelgeuse departs the constellation heading north fairly quickly, but Orion’s Belt hangs in there for nearly 2 million years even if it soon develops sag! The Pleiades drift together to the left and off frame and then reappear at right.

Stars seem to move with a wide range of velocities in the video, with stars in the galactic plane moving quite slow and faster ones speeding across the view. This is a perspective effect: most of the stars we see in the plane are much farther from us, and thus seem to be moving slower than the nearby stars, which are visible across the entire sky.

Artist’s impression of The Milky Way Galaxy to provide context for the video. The Sun and solar system are located in the flat plane of the galaxy, so when we look into the Milky Way (either toward the center or toward the edge), the stars pile up across the light years to form a band in the sky. If we could rise above the disk and see the galaxy from the halo, we’d be able to look down (or up) and see the galaxy as a disk with winding spiral arms. Credit: NASA

Some of the stars that appear to zip in and out of view quickly are passing close to the Sun. But motion of those that trace arcs from one side of the sky to the other while passing close to the galactic poles (top and bottom of the frame) as they speed up and slow down, is spurious. These stars move with a constant velocity through space.

Stars located in the Milky Way’s halo, a roughly spherical structure centered on the galaxy’s spiral disk, also appear to move quite fast because they slice through the galactic plane with respect to the Sun. In reality, halo stars move very slowly with respect to the center of the galaxy.

Early in the the visualization, we see clouds of interstellar gas and dust that occupy vast spaces within the galaxy and block the view of more distant suns. That these dark clouds seem to disappear over time is also a spurious effect.

After a few million years, the plane of the Milky Way appears to have shifted towards the right as a consequence of the motion of the Sun with respect to that of nearby stars in the Milky Way. Regions that are depleted of stars in the video will not appear that way to future stargazers but will instead be replenished by stars not currently sampled by Gaia. So yes, there are a few things to keep in mind while watching these positional data converted into stellar motions, but the overall picture is an accurate one.

I find the video as mesmerizing as watching fireflies on a June night. The stars seem alive. Enjoy your ride in the time machine!

Posted on by Evan Gough

TRAPPIST-1 Is Showing A Bit Too Much Flare

Artist's impression of a system of exoplanets orbiting a low mass, red dwarf star. Credit: NASA/JPL

It turns out that the TRAPPIST-1 star may be a terrible host for the TRAPPIST planets announced in February.

The TRAPPIST-1 star, a Red Dwarf, and its 7 planets caused a big stir in February when it was discovered that 3 of the rocky planets are in the habitable zone. But now more data is coming which suggests that the TRAPPIST-1 star is much too volatile for life to exist on its planets.

Red Dwarfs are much dimmer than our Sun, but they also last much longer. Their lifetimes are measured in trillions of years, not billions. Their long lives make them intriguing targets in the search for habitable worlds. But some types of Red Dwarf stars can be quite unstable when it comes to their magnetism and their flaring.

Our own Sun produces flares, but we are protected by our magnetosphere, and by the distance from the Sun to Earth. Credit: NASA/ Solar Dynamics Observatory,

A new study analyzed the photometric data on TRAPPIST-1 that was obtained by the K2 mission. The study, which is from the Konkoly Observatory and was led by astronomer Krisztián Vida, suggests that TRAPPIST-1 flares too frequently and too powerfully to allow life to form on its planets.

The study identified 42 strong flaring events in 80 days of observation, of which 5 were multi-peaked. The average time between flares was only 28 hours. These flares are caused by stellar magnetism, which causes the star to suddenly release a lot of energy. This energy is mostly in the X-ray or UV range, though the strongest can be seen in white light.

While it’s true that our Sun can flare, things are much different in the TRAPPIST system. The planets in that system are closer to their star than Earth is to the Sun. The most powerful flare observed in this data correlates to the most powerful flare observed on our Sun: the so-called Carrington Event.The Carrington Event happened in 1859. It was an enormously powerful solar storm, in which a coronal mass ejection struck Earth’s magnetosphere, causing auroras as far south as the Caribbean. It caused chaos in telegraph systems around the world, and some telegraph operators received electric shocks.

Earth survived the Carrington Event, but things would be much different on the TRAPPIST worlds. Those planets are much closer to their Sun, and the authors of this study conclude that storms like the Carrington Event are not isolated incidents on TRAPPIST-1. They occur so frequently that they would destroy any stability in the atmosphere, making it extremely difficult for life to develop. In fact, the study suggests that the TRAPPIST-1 storms could be hundreds or thousands of times more powerful than the storms that hit Earth.

A study from 2016 shows that these flares would cause great disturbances in the chemical composition of the atmosphere of the planets subjected to them. The models in that study suggest that it could take 30,000 years for an atmosphere to recover from one of these powerful flares. But with flares happening every 28 hours on TRAPPIST-1, the habitable planets may be doomed.

The Earth’s magnetic field helps protects us from the Sun’s outbursts, but it’s doubtful that the TRAPPIST planets have the same protection. This study suggests that planets like those in the TRAPPIST system would need magnetospheres of tens to hundreds of Gauss, whereas Earth’s magnetosphere is only about 0.5 Gauss. How could the TRAPPIST planets produce a magnetosphere powerful enough to protect their atmosphere?

It’s not looking good for the TRAPPIST planets. The solar storms that hit these worlds are likely just too powerful. Even without these storms, there are other things that may make these planets uninhabitable. They’re still an intriguing target for further study. The James Webb Space Telescope should be able to characterize the atmosphere, if any, around these planets.

Just don’t be disappointed if the James Webb confirms what this study tells us: the TRAPPIST system is a dead, lifeless, grouping of planets around a star that can’t stop flaring.

Posted on by Bob King

Finite Light — Why We Always Look Back In Time

Credit: Bob King

Beads of rainwater on a poplar leaf act like lenses, focusing light and enlarging the leaf’s network of veins. Moving at 186,000 miles per second, light from the leaf arrives at your eye 0.5 nanosecond later. A blink of an eye takes 600,000 times as much time! Credit: Bob King

My attention was focused on beaded water on a poplar leaf. How gemmy and bursting with the morning’s sunlight. I moved closer, removed my glasses and noticed that each drop magnified a little patch of veins that thread and support the leaf.

Focusing the camera lens, I wondered how long it took the drops’ light to reach my eye. Since I was only about six inches away and light travels at 186,000 miles per second or 11.8 inches every billionth of a second (one nanosecond), the travel time amounted to 0.5 nanoseconds. Darn close to simultaneous by human standards but practically forever for positronium hydride, an exotic molecule made of a positron, electron and hydrogen atom. The average lifetime of a PsH molecule is just 0.5 nanoseconds.

Light takes about 35 microseconds to arrive from a transcontinental jet and its contrail. Credit: Bob King

In our everyday life, the light from familiar faces, roadside signs and the waiter whose attention you’re trying to get reaches our eyes in nanoseconds. But if you happen to look up to see the tiny dark shape of a high-flying airplane trailed by the plume of its contrail, the light takes about 35,000 nanoseconds or 35 microseconds to travel the distance. Still not much to piddle about.

The space station orbits the Earth in outer space some 250 miles overhead. During an overhead pass, light from the orbiting science lab fires up your retinas 1.3 milliseconds later. In comparison, a blink of the eye lasts about 300 milliseconds (1/3 of a second) or 230 times longer!

The Lunar Laser Ranging Experiment placed on the Moon by the Apollo 14 astronauts. Observatories beam a laser to the small array, which reflects a bit of the light back. Measuring the time delay yields the Moon’s distance to within about a millimeter. At the Moon’s surface the laser beam spreads out to 4 miles wide and only one photon is reflected back to the telescope every few seconds. Credit: NASA

Light time finally becomes more tangible when we look at the Moon, a wistful 1.3 light seconds away at its average distance of 240,000 miles. To feel how long this is, stare at the Moon at the next opportunity and count out loud: one one thousand one. Retroreflecting devices placed on the lunar surface by the Apollo astronauts are still used by astronomers to determine the moon’s precise distance. They beam a laser at the mirrors and time the round trip.

Venus as a super-thin crescent only 10 hours before conjunction on March 25. The planet was just 2.3 light minutes from the Earth at the time. Credit: Shahrin Ahmad

Of the eight planets, Venus comes closest to Earth, and it does so during inferior conjunction, which coincidentally occurred on March 25. On that date only 26.1 million miles separated the two planets, a distance amounting to 140 seconds or 2.3 minutes — about the time it takes to boil water for tea. Mars, another close-approaching planet, currently stands on nearly the opposite side of the Sun from Earth.

With a current distance of 205 million miles, a radio or TV signal, which are both forms of light, broadcast to the Red Planet would take 18.4 minutes to arrive. Now we can see why engineers pre-program a landing sequence into a Mars’ probe’s computer to safely land it on the planet’s surface. Any command – or change in commands – we might send from Earth would arrive too late. Once a lander settles on the planet and sends back telemetry to communicate its condition, mission control personnel must bite their fingernails for many minutes waiting for light to limp back and bring word.

Before we speed off to more distant planets, let’s consider what would happen if the Sun had a catastrophic malfunction and suddenly ceased to shine. No worries. At least not for 8.3 minutes, the time it takes for light, or the lack of it, to bring the bad news.

Pluto and Charon lie 3.1 billion miles from Earth, a long way for light to travel. We see them as they were more than 4 hours ago.  NASA/JHUAPL/SwRI

Light from Jupiter takes 37 minutes to reach Earth; Pluto and Charon are so remote that a signal from the “double planet” requires 4.6 hours to get here. That’s more than a half-day of work on the job, and we’ve only made it to the Kuiper Belt.

Let’s press on to the nearest star(s), the Alpha Centauri system. If 4.6 hours of light time seemed a long time to wait, how about 4.3 years? If you think hard, you might remember what you were up to just before New Year’s Eve in 2012. About that time, the light arriving tonight from Alpha Centauri left that star and began its earthward journey. To look at the star then is to peer back in time to late 2012.

The Summer Triangle rises fully in the eastern sky around 3 o’clock in the morning in late March. Created with Stellarium

But we barely scrape the surface. Let’s take the Summer Triangle, a figure that will soon come to dominate the eastern sky along with the beautiful summer Milky Way that appears to flow through it. Altair, the southernmost apex of the triangle is nearby, just 16.7 light years from Earth; Vega, the brightest a bit further at 25 and Deneb an incredible 3,200 light years away.

We can relate to the first two stars because the light we see on a given evening isn’t that “old.” Most of us can conjure up an image of our lives and the state of world affairs 16 and 25 years ago. But Deneb is exceptional. Photons departed this distant supergiant (3,200 light years) around the year 1200 B.C. during the Trojan War at the dawn of the Iron Age. That’s some look-back time!

Rho Cassiopeia, currently at magnitude +4.5, is one of the most distant stars visible with the naked eye. Its light requires about 8,200 years to reach our eyes. This star, a variable, is enormous with a radius about 450 times that of the Sun. Credit: IAU/Sky and Telescope (left); Anynobody, CC BY-SA 3.0 / Wikipedia

One of the most distant naked eye stars is Rho Cassiopeiae, yellow variable some 450 times the size of the Sun located 8,200 light years away in the constellation Cassiopeia. Right now, the star is near maximum and easy to see at nightfall in the northwestern sky. Its light whisks us back to the end of the last great ice age at a time and the first cave drawings, more than 4,000 years before the first Egyptian pyramid would be built.

This is the digital message (annotated here) sent by Frank Drake to M13 in 1974 using the Arecibo radio telescope.

On and on it goes: the nearest large galaxy, Andromeda, lies 2.5 million light years from us and for many is the faintest, most distant object visible with the naked eye. To think that looking at the galaxy takes us back to the time our distant ancestors first used simple tools. Light may be the fastest thing in the universe, but these travel times hint at the true enormity of space.

Let’s go a little further. On November 16, 1974 a digital message was beamed from the Arecibo radio telescope in Puerto Rico to the rich star cluster M13 in Hercules 25,000 light years away. The message was created by Dr. Frank Drake, then professor of astronomy at Cornell, and contained basic information about humanity, including our numbering system, our location in the solar system and the composition of DNA, the molecule of life. It consisted of 1,679 binary bits representing ones and zeroes and was our first deliberate communication sent to extraterrestrials. Today the missive is 42 light years away, just barely out the door.

Galaxy GN-z11, shown in the inset, is seen as it was 13.4 billion years in the past, just 400 million years after the big bang, when the universe was only three percent of its current age. The galaxy is ablaze with bright, young, blue stars, but looks red in this image because its light has been stretched to longer spectral wavelengths by the expansion of the universe. Credit: NASA, ESA, P. Oesch, G. Brammer, P. van Dokkum, and G. Illingworth

Let’s end our time machine travels with the most distant object we’ve seen in the universe, a galaxy named GN-z11 in Ursa Major. We see it as it was just 400 million years after the Big Bang (13.4 billion years ago) which translates to a proper distance from Earth of 32 billion light years. The light astronomers captured on their digital sensors left the object before there was an Earth, a Solar System or even a Milky Way galaxy!

Thanks to light’s finite speed we can’t help but always see things as they were. You might wonder if there’s any way to see something right now without waiting for the light to get here? There’s just one way, and that’s to be light itself.

From the perspective of a photon or light particle, which travels at the speed of light, distance and time completely fall away. Everything happens instantaneously and travel time to anywhere, everywhere is zero seconds. In essence, the whole universe becomes a point. Crazy and paradoxical as this sounds, the theory of relativity allows it because an object traveling at the speed of light experiences infinite time dilation and infinite space contraction.

Just something to think about the next time you meet another’s eyes in conversation. Or look up at the stars.

Posted on by Evan Gough

A Family Of Stars Torn Apart

The stunning, shaped clouds of gas in the Orion Nebula make it beautiful, but also make it difficult to see inside of. This image of the Orion Nebula was captured by the Hubble Telescope. Image: NASA, ESA, M. Robberto (STScI/ESA) and The Hubble Space Telescope Orion Treasury Project Team
The stunning, shaped clouds of gas in the Orion Nebula make it beautiful, but also make it difficult to see inside of. This image of the Orion Nebula was captured by the Hubble Telescope. Image: NASA, ESA, M. Robberto (STScI/ESA) and The Hubble Space Telescope Orion Treasury Project Team

It sometimes doesn’t take much to tear a family apart. A Christmas dinner gone wrong can do that. But for a family of stars to be torn apart, something really huge has to happen.

The dramatic break-up of a family of stars played itself out in the Orion Nebula, about 600 years ago. The Orion Nebula is one of the most studied objects in our galaxy. It’s an active star forming region, where much of the star birth is concealed behind clouds of dust. Advances in infrared and radio astronomy have allowed us to peer into the Nebula, and to watch a stellar drama unfolding.

This three-frame illustration shows how a grouping of stars can break apart, flinging the members into space. Panel 1: members of a multiple-star system orbiting each other. Panel 2: two of the stars move closer together in their orbits. Panel 3: the closely orbiting stars eventually either merge or form a tight binary. This event releases enough gravitational energy to propel all of the stars in the system outward, as shown in the third panel.
Credits: NASA, ESA, and Z. Levy (STScI)

Over the last few decades, observations showed the two of the stars in our young family travelling off in different directions. In fact, they were travelling in opposite directions, and moving at very high speeds. Much higher than stars normally travel at. What caused it?

Astronomers were able to piece the story together by re-tracing the positions of both stars back 540 years. All those centuries ago, around the same time that it was dawning on humanity that Earth revolved around the Sun instead of the other way around, both of the speeding stars were in the same location. This suggested that the two were part of a star system that had broken up for some reason. But their combined energy didn’t add up.

Now, the Hubble has provided another clue to the whole story, by spotting a third runaway star. They traced the third star’s path back 540 years and found that it originated in the same location as the others. That location? An area near the center of the Orion Nebula called the Kleinmann-Low Nebula.

This composite image of the Kleinmann-Low Nebula, part of the Orion Nebula complex, is composed of several pointings of the NASA/ESA Hubble Space Telescope in optical and near-infrared light. Infrared light allows to peer through the dust of the nebula and to see the stars therein. The revealed stars are shown with a bright red colour in the image. With this image, showing the central region of the Orion Nebula, scientists were looking for rogue planets and brown dwarfs. As side-effect they found a fast-moving runaway star. By ESA/Hubble, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=57169218

The team behind these new results, led by Kevin Luhman of Penn State University, will release their findings in the March 20, 2017 issue of The Astrophysical Journal Letters.

“The new Hubble observations provide very strong evidence that the three stars were ejected from a multiple-star system,” said Luhman. “Astronomers had previously found a few other examples of fast-moving stars that trace back to multiple-star systems, and therefore were likely ejected. But these three stars are the youngest examples of such ejected stars. They’re probably only a few hundred thousand years old. In fact, based on infrared images, the stars are still young enough to have disks of material leftover from their formation.”

Young stars have a disk of gas and dust around them called a protoplanetary disk. Credit: NASA/JPL-Caltech

“The Orion Nebula could be surrounded by additional fledging stars that were ejected from it in the past and are now streaming away into space.” – Lead Researcher Kevin Luhman, Penn State University.

The three stars are travelling about 30 times faster than most of the Nebula’s other stellar inhabitants. Theory has predicted the phenomenon of these breakups in regions where newborn stars are crowded together. These gravitational back-and-forths are inevitable. “But we haven’t observed many examples, especially in very young clusters,” Luhman said. “The Orion Nebula could be surrounded by additional fledging stars that were ejected from it in the past and are now streaming away into space.”

The key to this mystery is the recently discovered third star. But this star, the so-called “source x”, was discovered by accident. Luhman is part of a team using the Hubble to hunt for free-floating planets in the Orion Nebula. A comparison of Hubble infrared images from 2015 with images from 1998 showed that source x had changed its position. This indicated that the star was moving at a speed of about 130,000 miles per hour.

The image by NASA’s Hubble Space Telescope shows a grouping of young stars, called the Trapezium Cluster (center). The box just above the Trapezium Cluster outlines the location of the three stars. A close-up of the stars is top right. The birthplace of the multi-star system is marked “initial position.” Two of the stars — labeled BN, and “I,” for source I — were discovered decades ago. Source I is embedded in thick dust and cannot be seen. The third star, “x,” for source x, was recently discovered to have moved noticeably between 1998 and 2015, as shown in the inset image at bottom right.
Credits: NASA, ESA, K. Luhman (Penn State University), and M. Robberto (STScI)

Luhmann then re-traced source x’s path and it led to the same position as the other 3 runaway stars 540 years ago: the Kleinmann-Low Nebula.

According to Luhmann, the three stars were most likely ejected from their system due to gravitational fluctuations that should be common in a high-population area of newly-born stars. Two of the stars can come very close together, either forming a tight binary system or even merging. That throws the gravitational parameters of the system out of whack, and other stars can be ejected. The ejection of those stars can also cause fingers of matter to flow out of the system.

As we get more powerful telescopes operating in the infrared, we should be able to clarify exactly what happens in areas of intense star formation like the Orion Nebula and its embedded Kleinmann-Low Nebula. The James Webb Space Telescope should advance our understanding greatly. If that’s the case, then not only will the details of star birth and formation become much clearer, but so will the break up of young families of stars.