The supernova remnant G352.7-0.1 in a composite image with X-rays from the Chandra X-Ray Telescope (blue), radio waves from the Very Large Array (pink), infrared information from the Spitzer Space Telescope (orange) and optical data from the Digital Sky Survey (white). Credit: X-ray: NASA/CXC/Morehead State Univ/T.Pannuti et al.; Optical: DSS; Infrared: NASA/JPL-Caltech; Radio: NRAO/VLA/Argentinian Institute of Radioastronomy/G.Dubner
Shining 24,000 light-years from Earth is an expanding leftover of a supernova that is doing a great cleanup job in its neighborhood. As this new composite image from NASA reveals, G352.7-0.1 (G352 for short) is more efficient than expected, picking up debris equivalent to about 45 times the mass of the Sun.
“A recent study suggests that, surprisingly, the X-ray emission in G352 is dominated by the hotter (about 30 million degrees Celsius) debris from the explosion, rather than cooler (about 2 million degrees) emission from surrounding material that has been swept up by the expanding shock wave,” the Chandra X-Ray Observatory’s website stated.
“This is curious because astronomers estimate that G352 exploded about 2,200 years ago, and supernova remnants of this age usually produce X-rays that are dominated by swept-up material. Scientists are still trying to come up with an explanation for this behavior.”
The difference between a neutron star and a quark star (Chandra)
You may have heard that CERN announced the discovery (confirmation, actually. See addendum below.) of a strange particle known as Z(4430). A paper summarizing the results has been published on the physics arxiv, which is a repository for preprint (not yet peer reviewed) physics papers. The new particle is about 4 times more massive than a proton, has a negative charge, and appears to be a theoretical particle known as a tetraquark. The results are still young, but if this discovery holds up it could have implications for our understanding of neutron stars.
A periodic table of elementary particles. Credit: Wikipedia
The building blocks of matter are made of leptons (such as the electron and neutrinos) and quarks (which make up protons, neutrons, and other particles). Quarks are very different from other particles in that they have an electric charge that is 1/3 or 2/3 that of the electron and proton. They also possess a different kind of “charge” known as color. Just as electric charges interact through an electromagnetic force, color charges interact through the strong nuclear force. It is the color charge of quarks that works to hold the nuclei of atoms together. Color charge is much more complex than electric charge. With electric charge there is simply positive (+) and its opposite, negative (-). With color, there are three types (red, green, and blue) and their opposites (anti-red, anti-green, and anti-blue).
Because of the way the strong force works, we can never observe a free quark. The strong force requires that quarks always group together to form a particle that is color neutral. For example, a proton consists of three quarks (two up and one down), where each quark is a different color. With visible light, adding red, green and blue light gives you white light, which is colorless. In the same way, combining a red, green and blue quark gives you a particle which is color neutral. This similarity to the color properties of light is why quark charge is named after colors.
Combining a quark of each color into groups of three is one way to create a color neutral particle, and these are known as baryons. Protons and neutrons are the most common baryons. Another way to combine quarks is to pair a quark of a particular color with a quark of its anti-color. For example, a green quark and an anti-green quark could combine to form a color neutral particle. These two-quark particles are known as mesons, and were first discovered in 1947. For example, the positively charged pion consists of an up quark and an antiparticle down quark.
Under the rules of the strong force, there are other ways quarks could combine to form a neutral particle. One of these, the tetraquark, combines four quarks, where two particles have a particular color and the other two have the corresponding anti-colors. Others, such as the pentaquark (3 colors + a color anti-color pair) and the hexaquark (3 colors + 3 anti-colors) have been proposed. But so far all of these have been hypothetical. While such particles would be color neutral, it is also possible that they aren’t stable and would simply decay into baryons and mesons.
There has been some experimental hints of tetraquarks, but this latest result is the strongest evidence of 4 quarks forming a color neutral particle. This means that quarks can combine in much more complex ways than we originally expected, and this has implications for the internal structure of neutron stars.
Very simply, the traditional model of a neutron star is that it is made of neutrons. Neutrons consist of three quarks (two down and one up), but it is generally thought that particle interactions within a neutron star are interactions between neutrons. With the existence of tetraquarks, it is possible for neutrons within the core to interact strongly enough to create tetraquarks. This could even lead to the production of pentaquarks and hexaquarks, or even that quarks could interact individually without being bound into color neutral particles. This would produce a hypothetical object known as a quark star.
This is all hypothetical at this point, but verified evidence of tetraquarks will force astrophysicists to reexamine some the assumptions we have about the interiors of neutron stars.
Addendum: It has been pointed out that CERN’s results are not an original discovery, but rather a confirmation of earlier results by the Belle Collaboration. The Belle results can be found in a 2008 paper in Physical Review Letters, as well as a 2013 paper in Physical Review D. So credit where credit is due.
The Milky Way, The Large and Small Magellanic Clouds, Zodiacal Light, and Venus as seen from the Karoo Desert in South Africa early this month. Credit: Cory Schmitz.
Have you been following the planet Venus this season? 2014 sees the brightest planet in our Earthly skies spend a majority of its time in the dawn. Shining at magnitude -3.8, it’s hard to miss in the morning twilight. But dazzling Venus is visiting two unique celestial objects over the next week, and both present unique observing challenges for the seasoned observer.
First up is an interesting close conjunction of the planets Venus and Neptune on the morning of Saturday, April 12th. Closest conjunction occurs at 3:00 Universal Time (UT) April 12th favoring Eastern Europe, the Middle East and eastern Africa, when the two worlds appear to be just 40 arc minutes apart, a little over – by about 10’ – the apparent size of a full Moon. Shining at magnitude +7.8 and 30,000 times fainter than Venus, you’ll need a telescope to tease out Neptune from the pre-dawn sky. Both objects will, however, easily fit in a one degree field of view, in addition to a scattering of other stars.
Looking to the east the morning of April 12th from the U.S. East Coast near latitude 30 degrees north. Nearby stars are annotated in red by magnitude with decimals omitted. Created using Stellarium, click to enlarge.
At low power, Venus will display a 59% illuminated gibbous phase 20” across on the morning of the 12th, while Neptune will show a tiny disk barely 2” across. Still, this represents the first chance for viewers to recover Neptune since solar conjunction behind the Sun on February 23rd, 2014, using dazzling Venus as a guide.
Both sit 45 degrees west of the Sun and currently rise around 3 to 4 AM local dependent on latitude.
This is one of the closest planet-planet conjunctions for 2014. The closest is Venus and Jupiter at just 0.2 degrees apart on August 18th. This will represent the brightest planet versus planet conjunction for the year, and is sure to illicit multiple “what’s those two bright stars in the sky?” queries from morning commuters… hopefully, such sightings won’t result in any border skirmishes worldwide.
Now, for the mandatory Wow factor. On the date of conjunction, Earth-sized Venus is 0.84 Astronomical Units (A.U.s) or over 130 million kilometres distant. Ice giant Neptune, however, is 30.7 AUs or 36 times as distant, and only appears tiny though it’s almost four times larger in diameter. Sunlight reflected from Venus takes 7 minutes to reach Earth, but over four hours to arrive from Neptune. We’ve visited Venus lots, and the Russians have even landed there and returned images from its smoldering surface, but we’ve only visited Neptune once, during a brief flyby of Voyager 2 in 1989.
From Neptune looking back on April 12th, Earth and Venus would appear less than 1 arc minute apart…. though they’d also be just over one degree from the Sun!
The “shadow path” of the occultation of Lambda Aquarii by Venus on April 16th. Credit: IOTA/Steve Preston/www.asteroidoccultation/Occult 4.0.
But an even more bizarre event happens a few days later on April 16th, though only a small region of the world in the South Pacific may bare witness to it.
Next Wednesday from 17:59 to 18:13 UT Venus occults the +3.7 magnitude star HIP 112961 also known as Lambda Aquarii on the morning of April 16th 2014.
Venus will be a 61% illuminated gibbous phase 19” in diameter. Unfortunately, although North America is rotated towards the event, it’s also in the middle of the day.
The best prospects to observe the occultation are from New Zealand and western Pacific at dawn. The star will disappear behind the bright limb of Venus in dawn twilight before emerging on its dark limb 5 minutes later as seen from New Zealand.
The path of Lambda Aquarii behind Venus as seen from New Zealand the morning of the 16th. Created in Starry Night.
Note: New Zealand switched back to standard time on April 6th – it’s currently Fall down under – and local sunrise occurs around ~7:40 AM.
Lambda Aquarii is a 3.6 solar mass star located 390 light years distant. As far as we know, it’s a solitary star, though there’s always a chance that a companion could make itself known as it emerges on the dark limb of Venus. Such an observation will, however, be extremely difficult, as Venus is still over 700 times brighter than the star!
North Americans get to see the pair only 20’ apart on the morning of the 12th.
One degree fields of view worldwide showing Venus and Lambda Aquarii at 7AM local. Credit: Starry Night.
And further occultation adventures await Venus in the 21st century. On October 1st, 2044 it will occult Regulus… and on November 22nd, 2065 it will actually occult Jupiter!
Such pairings give us a chance to image Venus with a “pseudo-moon.” Early telescopic observers made numerous sightings of a supposed Moon of Venus, and the hypothetical object even merited the name Neith for a brief time. Such sightings were most likely spurious internal reflections due to poor optics or nearby stars, but its fun to wonder what those observers of old might’ve seen.
… and speaking of moons, don’t miss a chance to see Venus near the daytime Moon April 25th. Follow us as @Astroguyz on Twitter as we give shout outs to these and other strange pairings daily!
Artist's conception of how the Baryon Oscillation Spectroscopic Survey uses quasars to make measurements. The light these objects sends out gets absorbed by gas in between the receiver and the source. The gas is then "imprinted wiht a subtle ring-like pattern of known physical scale", the Sloan Digital Sky Survey stated. Credit: Zosia Rostomian (Lawrence Berkeley National Laboratory) and Andreu Font-Ribera (BOSS Lyman-alpha team, Berkeley Lab.)
For those who saw the Cosmos episode on William Herschel describing telescopes as time machines, here is a clear example of that. By examining 140,000 objects called quasars (galaxies with an active black hole at their centers), astronomers have charted the expansion rate of the universe — not now, but 10.8 billion years ago.
This is the most precise measurement ever of the universe’s expansion rate at any point in time, the science teams said, with the calculation showing the universe was expanding by 1% every 44 million years at that time. (That figure is to 2% precision, the researchers added.)
“If we look back to the Universe when galaxies were three times closer together than they are today, we’d see that a pair of galaxies separated by a million light-years would be drifting apart at a speed of 68 kilometers per second as the Universe expands,” stated Andreu Font-Ribera of the Lawrence Berkeley National Laboratory, who led one of the two analyses.
The researchers used a telescope called the Sloan Digital Sky Survey, a 2.5-meter telescope at Apache Point Observatory in New Mexico. The discovery was made during Sloan’s Baryon Oscillation Spectroscopic Survey, or BOSS, whose aim has been to figure out the expansion and acceleration of the universe.
The accelerating, expanding Universe. Credit: NASA/WMAP
“BOSS determines the expansion rate at a given time in the Universe by measuring the size of baryon acoustic oscillations (BAO), a signature imprinted in the way matter is distributed, resulting from sound waves in the early Universe,” the Sloan Digital Sky Survey stated. “This imprint is visible in the distribution of galaxies, quasars, and intergalactic hydrogen throughout the cosmos.”
Font-Ribera and his collaborators examined how quasars are distributed compared to hydrogen gas to calculate distance. The other analysis, led by Timothée Delubac (Centre de Saclay, France), examined the hydrogen gas to see patterns and measure mass distribution.
You can read more about Font-Ribera’s team’s research in preprint version on Arxiv. Delubac’s research does not appear to be available online, but the title is “Baryon Acoustic Oscillations in the Ly-alpha forest of BOSS DR11 quasars” and it has been submitted to Astronomy & Astrophysics.
Artist's conception of a starquake cracking the surface of a neutron star. Credit: Darlene McElroy of LANL
Much like how an earthquake can teach us about the interior of the Earth, a starquake shows off certain properties about the inside of a star. Studying the closest star we have (the sun) has yielded information about rotation, radius, mass and other properties of stars that are similar to our own. But how do we apply that information to other types of stars?
A team of astronomers attempted to model the inside of a delta-Scuti, a star like Caleum that is about 1.5 to 2.5 times the mass of the sun and spins rapidly, so much more that it tends to flatten out. The model reveals there is likely a correlation between how these types of stars oscillate, and what their average density is. The theory likely holds for stars as massive as four times the mass of our sun, the team said.
“Thanks to asteroseismology we know precisely the internal structure, mass, radius, rotation and evolution of solar type stars, but we had never been able to apply this tool efficiently to the study of hotter and more massive stars,” stated Juan Carlos Suárez, a researcher at the Institute of Astrophysics of Andalusia who led the investigation.
Model of an oscillation within the sun. Credit: David Guenther, Saint Mary´s University
What’s more, knowing how dense a star is leads to other understandings: what its mass is, its diameter and also the age of any exoplanets that happen to be hovering nearby. The astronomers added that the models could be of use for the newly selected Planetary Transits and Oscillations (PLATO) telescope that is expected to launch in 2024.
A newly-discovered star of magnitude +10.9 has flared to life in the constellation Cygnus the Swan. Koichi Nishiyama and Fujio Kabashima, both of Japan, made their discovery yesterday March 31 with a 105mm f/4 camera lens and electronic camera. They quickly confirmed the observation with additional photos taken with a 0.40-m (16-inch) reflector. Nothing was seen down to magnitude +13.4 in photos taken the on the 27th, but when they checked through images made on March 30 the star present at +12.4. Good news – it’s getting brighter!
This more detailed map, showing stars to mag. 10.5, will help you pinpoint the star. Its coordinates are R.A. 20h 21m 42, declination +31 o3′. Stellarium
While the possible nova will need confirmation, nova lovers may want to begin observing the star as soon as possible. Novae can brighten quickly, sometimes by several magnitudes in just a day. These maps should help you hone in on the star which rises around midnight and becomes well placed for viewing around 1:30-2 a.m. local time in the eastern sky. At the moment, it will require a 4-inch or larger telescope to see, but I’m crossing my fingers we’ll see it brighten further.
Novae occur in close binary systems where one star is a tiny but extremely compact white dwarf star. The dwarf pulls material into a disk around itself, some of which is funneled to the surface and ignites in a nova explosion. Credit: NASA
To see a nova is to witness a cataclysm. Astronomers – mostly amateurs – discover about 10 a year in our Milky Way galaxy. Many more would be seen were it not for dust clouds and distance. All involve close binary stars where a tiny but extremely dense white dwarfstar steals gas from its companion. The gas ultimately funnels down to the 150,000 degree surface of the dwarf where it’s compacted by gravity and heated to high temperature until it ignites in an explosive fireball. If you’ve ever wondered what a million nuclear warheads would look like detonated all at once, cast your gaze at a nova.
Novae can rise in brightness from 7 to 16 magnitudes, the equivalent of 50,000 to 100,000 times brighter than the sun, in just a few days. Meanwhile the gas they expel in the blast travels away from the binary at up to 2,000 miles per second.
Emission of deep red light called hydrogen alpha or H-alpha is often diagnostic of a nova. When in the fireball phase, the star is hidden by a fiery cloud of rosy hydrogen gas and expanding debris cloud. Italian astronomer obtained this spectrum of the possible nova on April 1 showing H-alpha emission. Credit: Gianluca Masi
Nishiyama and Kabashima are on something of a hot streak. If confirmed, this would be their third nova discovery in a month! On March 8, they discovered Nova Cephei 2014 at magnitude 11.7 (it’s currently around 12th magnitude) and 10th magnitude Nova Scorpii 2014 (now at around 12.5) on March 26. Impressive.
Photo showing the possible nova in Cygnus. The star is described as being tinted red. Credit: Gianluca Masi
Charts for the two older discoveries are available on the AAVSO website. Type in either Nova Cep 2014 or TCP J17154683-3128303 (for Nova Scorpii) in the Star finder box and click Create a finder chart. I’ll update this article as soon as a chart for the new object is posted.
** UPDATE April 2, 2014: This star has been confirmed as a nova. You can print out a chart by going to the AAVSO website and following the instructions above using Nova Cyg 2014 for the star name. On April 2.4 UT, I observed the nova at magnitude 11.o.
A photogenic grouping greets evening sky watchers this week providing a fine teaser leading up to a spectacular eclipse.
On the evening of Thursday, April 3rd headed into the morning of the 4th, the waxing crescent Moon crosses in front of the Hyades open star cluster. This is the V-shaped asterism that marks the head on Taurus the Bull, highlighted by the brilliant foreground star Aldebaran as the bull’s “eye”. Viewers across North America will have a ring-side seat to this “bull-fight” as the 20% illuminated Moon stampedes over several members of the Hyades in its path.
The passage of the Moon through the Hyades over a three hour span on the night of April 3rd (April 4th in Universal Time) comparing the North American locales of Tampa, Florida and Seattle, Washington. (Credit: Starry Night Education Software).
The brightest stars to be occulted are the Delta Tauri trio of stars ranging in magnitudes from +3.8 (Delta Tauri^1) to +4.8(2) and +4.3(3). Such occlusions – known in astronomy as occultations – are fun to watch, and can reveal the existence of close binary companions as they wink out behind the lunar limb. Several dozen occultations of stars brighter than +5th magnitude by the Moon happen each year, and the best events occur when the Moon is waxing and the stars disappear against its dark leading edge. We recently caught one such event last month when the Moon occulted the bright star Lambda Geminorum:
We are currently seeing the Moon cross the Hyades during every lunation until the year 2020, though it’s a particularly favorable time to catch the event in April 2014 as the Moon is a slender crescent. Notice that you can just make out the dark limb of the Moon with the naked eye? What you’re seeing is termed Earthshine, and that’s just what it is: the nighttime side of the Moon being illuminated by sunlight that is reflected off of the Earth. Standing on the Earthward side of the Moon, an observer would see a waning gibbous Earth about two degrees across. Yutu has a great view!
The occultation footprint for Delta Tauri^1. Credit: Occult 4.0
The Moon will cross its descending node where its apparent path intersects the ecliptic on April 1st (no joke, we swear) at 2:30 Universal Time or 10:30 PM EDT on March 31st. The next nodal crossing now occurs in just two weeks, and the Earth’s shadow will be there to greet the Moon on the morning of April 15th in the first of four total lunar eclipses that span 2014 and 2015. The month of April also sees the Moon’s orbit at its least eccentric, a time at which perigee – the Moon’s closest point to Earth – is at its most distant and apogee – its farthest point – is at its closest. This currently happens near the equinoxes, through the nodes slowly travel across the ecliptic completing one revolution every 18.6 years. Perigee can vary from 356,400 to 370,400 kilometres, and apogee can span a distance from 404,000 to 406,700 kilometres.
Looking west from the US SE at about 10PM local on the evening of April 3rd. Credit: Stellarium.
We’re also headed towards a “shallow year” in 2015 when the Moon has the least variability in respect to its declination. This trend will then reverse, climaxing with a “Long Nights Moon” riding high in the sky in 2025, which last occurred in 2006. The Moon will inch ever closer to Aldebaran on every successive lunation now, and begins a series of occultations of Aldebaran on January 29th, 2015 through the end of 2018. Occultations of Aldebaran always occur near these shallow years, and will be followed by a cycle of occultations of Regulus starting in 2017. We caught an excellent daytime occultation of Aldebaran by the Moon from North Pole, Alaska during the last cycle in the late 1990s.
The Moon passing between the Hyades and Pleiades in 2011 with Earthshine highlighted. Photos by author.
Now for the wow factor. Our Moon is 3,474 kilometres across and located just over one light second away. The Hyades star cluster covers about 6 ½ degrees of sky – about 7 times the size of the Full Moon – but is the closest open cluster to the Earth at 153 light years distant and has a core diameter of about 18 light years across. As mentioned previous, Aldebaran isn’t physically associated with the Hyades, but is merely located in the same direction at 65 light years distant.
The Hyades star cluster also provided early 20th astronomers with an excellent study in galactic motion. At an estimated 625 million years in age, the Hyades are slowly getting disbanded and strewn about the Milky Way galaxy in a process known as evaporation. The Hyades are also part of a larger stellar incorporation known as the Taurus Moving Cluster. Moving at an average of about 43 kilometres a second, the members of the Hyades are receding from us towards a divergent point near the bright star Betelgeuse in the shoulder of Orion. 50 million years hence, the Hyades will be invisible to the naked eye as seen from Earth, looking like a non-descript open cluster and providing a much smaller target for the Moon to occult at 20’ across. Astronomer Lewis Boss was the first to plot the motion of the Hyades through space in 1908, and the cluster stands as an essential rung on the cosmic distance ladder, with agreeing measurements independently made by both Hubble and Hipparcos and soon to be refined by Gaia.
Photographing and documenting this week’s passage of our Moon across the Hyades is easy with a DSLR camera: don’t be afraid to vary those ISO and shutter speeds to get the mix of the brilliant crescent Moon, the fainter earthshine, and background stars just right. The more adventurous might want to try actually catching the numerous occultations of bright stars on video. And U.S. and Canadian west coast observers are well placed to catch the Moon cross right though the core of the Hyades… a video animation of the event is not out of the question!
And from there, the Moon heads on to its date with destiny and a fine total lunar eclipse on April 15th which favors North American longitudes. We’ll be back later this week with our complete and comprehensive eclipse guide!
A portion of a collage of galaxies included in the Herschel Reference Survey, in false color to show different dust temperatures. (Blue is colder, and red is warmer). Credit: ESA/Herschel/HRS-SAG2 and HeViCS Key Programmes/L. Cortese (Swinburne University)
While dust is easy to ignore in small quantities (says the writer looking at her desk), across vast reaches of space this substance plays an important role. Stick enough grains together, the theory goes, and you’ll start to form rocks and eventually planets. On a galaxy-size scale, dust may even effect how the galaxy evolves.
A new survey of 323 galaxies reveals that dust is not only affected by the kinds of stars in the vicinity, but also what the galaxy is made of.
“These dust grains are believed to be fundamental ingredients for the formation of stars and planets, but until now very little was known about their abundance and physical properties in galaxies other than our own Milky Way,” stated lead author Luca Cortese, who is from the Swinburne University of Technology in Melbourne, Australia.
“The properties of grains vary from one galaxy to another – more than we originally expected,” he added. “As dust is heated by starlight, we knew that the frequencies at which grains emit should be related to a galaxy’s star formation activity. However, our results show that galaxies’ chemical history plays an equally important role.”
Galaxies in the Herschel Reference Survey in infrared/submillimeter wavelengths (with the Herschel space telescope, at left) and the Sloan Digital Sky Survey (right). Herschel’s false-color image shows galaxies with cold dust (blue) and warm dust (red). Sloan highlights young stars (blue) and old stars (red). “Together, the observations plot young, dust-rich spiral/irregular galaxies in the top left, with giant dust-poor elliptical galaxies in the bottom right,” the European Space Agency stated. Credit: ESA/Herschel/HRS-SAG2 and HeViCS Key Programmes/Sloan Digital Sky Survey/ L. Cortese (Swinburne University)
Data was captured with two cameras on the just-retired Herschel space telescope: Spectral and Photometric Imaging Receiver (SPIRE) and Photodetecting Array Camera and Spectrometer (PACS). These instruments examined different frequencies of dust emission, which shows what the grains are made of. You can see a few of those galaxies in the image above.
“The dust-rich galaxies are typically spiral or irregular, whereas the dust-poor ones are usually elliptical,” the European Space Agency stated. “Dust is gently heated across a range of temperatures by the combined light of all of the stars in each galaxy, with the warmest dust being concentrated in regions where stars are being born.”
Astronomers initially expected that a galaxy with speedy star formation would display more massive and warmer stars in it, corresponding to warmer dust in the galaxy emitting light in short wavelengths.
“However, the data show greater variations than expected from one galaxy to another based on their star formation rates alone, implying that other properties, such as its chemical enrichment, also play an important role,” ESA said.
A 2014 image of NGC 2174 by the Hubble Space Telescope. Credit: NASA/ESA and the Hubble Heritage Team (STScI/AURA)
Billowing gas clouds and young stars feature in this February Hubble Space Telescope image, released as the telescope approaches its 24th birthday this coming April. The telescope has seen a lot of drama over the years, but in this case, thankfully the excitement is taking place 6,400 light-years away. Here you can see starbirth in action in the nebula NGC 2174, which is sometimes called the Monkey Head Nebula.
“This region is filled with young stars embedded within bright wisps of cosmic gas and dust. Dark dust clouds billow outwards, framed against a background of bright blue gas. These striking hues were formed by combining several Hubble images taken through different coloured filters, revealing a broad range of colours not normally visible to our eyes,” the European Space Agency wrote.
“These vivid clouds are actually a violent stellar nursery packed with the ingredients needed for building stars. The recipe for cooking up new stars is quite inefficient, and most of the ingredients are wasted as the cloud of gas and dust disperses. This process is accelerated by the presence of fiercely hot young stars, which triggers high-speed winds that help to blow the gas outwards.”
Hubble’s dramatic history includes a deformed mirror, a rescue mission, and a nearly last-minute decision to do a shuttle flight for repairs and upgrades when the shuttle program was wrapping up. You can read more about Hubble’s colorful history at the Space Telescope Science Institute.
It’s a tough old universe out there. A young star has lots to worry about, as massive stars just beginning to shine can fill a stellar nursery with a gale of solar wind.
No, it’s not a B-movie flick: the “Death Stars of Orion” are real. Such monsters come in the form of young, O-type stars.
And now, for the first time, a team of astronomers from Canada and the United States have caught such stars in the act. The study, published in this month’s edition of The Astrophysical Journal, focused on known protoplanetary disks discovered by the Hubble Space Telescope in the Orion Nebula.
These protoplanetary disks, also known as “tadpoles” or proplyds, are cocoons of dust and gas hosting stars just beginning to shine. Much of this leftover material will go on to aggregate into planets, but nearby massive O-Type stars can cause chaos in a stellar nursery, often disrupting the process.
“O-Type stars, which are really monsters compared to our Sun, emit tremendous amounts of ultraviolet radiation and this can play havoc during the development of young planetary systems,” said astronomer Rita Mann in a recentpress release. Mann works for the National Research Council of Canada in Victoria and is lead researcher on the project
Scientists used the Atacama Large Millimeter Array (ALMA) to probe the proplyds of Orion in unprecedented detail. Supporting observations were also made using the Submillimeter Array in Hawaii.
ALMA saw “first light” in 2011, and has already achieved some first rate results.
“ALMA is the world’s most sensitive telescope at high-frequency radio waves (e.g., 100-1000 GHz). Even with only a fraction of its final number of antennas, (with 22 operational out of a total planned 50) we were able to detect with ALMA the disks relatively close to the O-star while previous observatories were unable to spot them,” James Di Francesco of the National Research Council of Canada told Universe Today. “Since the brightness of a disk at these frequencies is proportional to its mass, these detections meant we could measure the masses of the disks and see for sure that they were abnormally low close to the O-type star.”
The ALMA antennae on the barren plateau of Chajnantor. Credit: ALMA (ESO/NAOJ/NRAO).
ALMA also doubled the number of proplyds seen in the region, and was also able to peer within these cocoons and take direct mass measurements. This revealed mass being stripped away by the ultraviolet wind from the suspect O-type stars. Hubble had been witness to such stripping action previous, but ALMA was able to measure the mass within the disks directly for the first time.
And what was discovered doesn’t bode well for planetary formation. Such protostars within about 0.1 light-years of an O-type star are consigned to have their cocoon of gas and dust stripped clean in just a few million years, just a blink of a eye in the game of planetary formation.
With a O-type star’s “burn brightly and die young” credo, this type of event may be fairly typical in nebulae during early star formation.
“O-type stars have relatively short lifespan, say around 1 million years for the brightest O-star in Orion – which is 40 times the mass of our Sun – compared to the 10 billion year lifespan of less massive stars like our Sun,” Di Francesco told Universe Today. “Since these clusters are typically the only places where O-stars form, I’d say that this type of event is indeed typical in nebulae hosting early star formation.”
It’s common for new-born stars to be within close proximity of each other in such stellar nurseries as M42. Researchers in the study found that any proplyds within the extreme-UV envelope of a massive star would have its disk shredded in short order, retaining on average less than 50% the mass of Jupiter total. Beyond the 0.1 light year “kill radius,” however, the chances for these proplyds to retain mass goes up, with researchers observing anywhere from 1 to 80 Jupiter masses of material remaining.
The findings in this study are also crucial in understanding what the early lives of stars are like, and perhaps the pedigree of our own solar system, as well as how common – or rare – our own history might be in the story of the universe.
There’s evidence that our solar system may have been witness to one or more nearby supernovae early in its life, as evidenced by isotopic measurements. We were somewhat lucky to have had such nearby events to “salt” our environment with heavy elements, but not sweep us clean altogether.
“Our own Sun likely formed in a clustered environment similar to that of Orion, so it’s a good thing we didn’t form too close to the O-stars in its parent nebula,” Di Francesco told Universe Today. “When the Sun was very young, it was close enough to a high-mass star so that when it blew up (went supernova) the proto-solar system was seeded with certain isotopes like Al-26 that are only produced in supernova events.”
This is the eventual fate of massive O-type stars in the Orion Nebula, though none of them are old enough yet to explode in this fashion. Indeed, it’s amazing to think that peering into the Orion Nebula, we’re witnessing a drama similar to what gave birth to our Sun and solar system, billions of years ago.
The Orion Nebula is the closest active star forming region to us at about 1,500 light years distant and is just visible to the naked eye as a fuzzy patch in the pommel of the “sword” of Orion the Hunter. Looking at the Orion Nebula at low power through a small telescope, you can just make out a group of four stars known collectively as the Trapezium. These are just such massive hot and luminous O-Type stars, clearing out their local neighborhoods and lighting up the interior of the nebula like a Chinese lantern.
And thus science fact imitates fiction in an ironic twist, as it turns out that “Death Stars” do indeed blast planets – or at least protoplanetary disks – on occasion!
Be sure to check out a great piece on ALMA on a recent episode of CBS 60 Minutes:
Read the abstract and the full (paywalled) paper on ALMA Observations of the Orion Proplyds in The Astrophysical Journal.
