There are Strange Objects Near the Center of the Galaxy. They Look Like Gas, but Behave Like Stars

During the 1970s, astronomer became aware of a massive radio source at the center of our galaxy that they later realized was a Supermassive Black Hole (SMBH) – which has since been named Sagittarius A*. And in a recent survey conducted by NASA’s Chandra X-ray Observatory, astronomers discovered evidence for hundreds or even thousands of black holes located in the same vicinity of the Milky Way.

But, as it turns out, the center of our galaxy has more mysteries that are just waiting to be discovered. For instance, a team of astronomers recently detected a number of “mystery objects” that appeared to be moving around the SMBH at Galactic Center. Using 12 years of data taken from the W.M. Keck Observatory in Hawaii, the astronomers found objects that looked like dust clouds but behaved like stars.

The research was conducted through a collaboration between Randy Campbell at the W.M. Keck Observatory, members of the Galactic Center Group at UCLA (Anna Ciurlo, Mark Morris, and Andrea Ghez) and Rainer Schoedel of the Instituto de Astrofisica de Andalucia (CSIC) in Granada, Spain. The results of this study were presented at the 232nd American Astronomical Society Meeting during a press conference titled “The Milky Way & Active Galactic Nuclei”.

Pictured here are members of GCOI in front of Keck Observatory on Maunakea, Hawaii, during a visit last year. Credit: W.M. Keck Observatory

As Ciurlo explained in a recent W.M. Keck press release:

“These compact dusty stellar objects move extremely fast and close to our Galaxy’s supermassive black hole. It is fascinating to watch them move from year to year. How did they get there? And what will they become? They must have an interesting story to tell.”

The researchers made their discovery using 12 years of spectroscopic measurements obtained by the Keck Observatory’s OH-Suppressing Infrared Imaging Spectrograph (OSIRIS). These objects – which were designed as G3, G4, and G5 – were found while examining the gas dynamics of the center of our galaxy, and were distinguished from background emissions because of their movements.

“We started this project thinking that if we looked carefully at the complicated structure of gas and dust near the supermassive black hole, we might detect some subtle changes to the shape and velocity,” explained Randy Campbell. “It was quite surprising to detect several objects that have very distinct movement and characteristics that place them in the G-object class, or dusty stellar objects.”

Astronomers first discovered G-objects in proximity to Sagittarius A* more than a decade ago – G1 was discovered in 2004 and G2 in 2012. Initially, both were thought to be gas clouds until they made their closest approach to the supermassive black hole and survived. Ordinarily, the SMBHs gravitational pull would shred gas clouds apart, but this did not happen with G1 and G2.

3-D spectro-imaging data cube produced using software called OSIRIS-Volume Display ( OsrsVol) to separate G3, G4, and G5 from the background emission. Credit: W.M. Keck Observatory

Because these newly discovered infrared sources (G3, G4, and G5) shared the physical characteristics of G1 and G2, the team concluded that they could potentially be G-objects. What makes G-objects unusual is their “puffiness”, where they appear to be cloaked in a layer of dust and gas that makes them difficult to detect. Unlike other stars, astronomers only see a glowing envelope of dust when looking at G-objects.

To see these objects clearly through their obscuring envelope of dust and gas, Campbell developed a tool called the OSIRIS-Volume Display (OsrsVol). As Campbell described it:

“OsrsVol allowed us to isolate these G-objects from the background emission and analyze the spectral data in three dimensions: two spatial dimensions, and the wavelength dimension that provides velocity information. Once we were able to distinguish the objects in a 3-D data cube, we could then track their motion over time relative to the black hole.”

UCLA Astronomy Professor Mark Morris, a co-principal investigator and fellow member of UCLA’s Galactic Center Orbits Initiative (GCOI), was also involved in the study. As he indicated:

“If they were gas clouds, G1 and G2 would not have been able to stay intact. Our view of the G-objects is that they are bloated stars – stars that have become so large that the tidal forces exerted by the central black hole can pull matter off of their stellar atmospheres when the stars get close enough, but have a stellar core with enough mass to remain intact. The question is then, why are they so large?

Chandra data (above, graph) on J0806 show that its X-rays vary with a period of 321.5 seconds, or slightly more than five minutes. This implies that the X-ray source is a binary star system where two white dwarf stars are orbiting each other (above, illustration) only 50,000 miles apart, making it one of the smallest known binary orbits in the Galaxy. According to Einstein's General Theory of Relativity, such a system should produce gravitational waves - ripples in space-time - that carry energy away from the system and cause the stars to move closer together. X-ray and optical observations indicate that the orbital period of this system is decreasing by 1.2 milliseconds every year, which means that the stars are moving closer at a rate of 2 feet per year.
A binary star system potentially on the verge of a stellar collision. Credit: Chandra

After examining the objects, the team noticed that there was a great deal of energy was emanating from them, more than what would be expected from typical stars. As a result, they theorized that these G-objects are the result of stellar mergers, which occur when two stars that orbit each other (aka. binaries) crash into each other. This would have been caused by the long-term gravitational influence of the SMBH.

The resulting single object would be distended (i.e. swell up) over the course of millions of years before it finally settled down and appeared like a normal-sized star. The combined objects that resulted from these violent mergers could explain where the excess energy came from and why they behave like stars do. As Andrea Ghez, the founder and director of GCOI, explained:

“This is what I find most exciting. If these objects are indeed binary star systems that have been driven to merge through their interaction with the central supermassive black hole, this may provide us with insight into a process which may be responsible for the recently discovered stellar mass black hole mergers that have been detected through gravitational waves.”

Looking ahead, the team plans to continue following the size and shape of the G-objects’ orbits in the hopes of determining how they formed. They will be paying especially close attention when these stellar objects make their closest approach to Sagittarius A*, since this will allow them to further observe their behavior and see if they remain intact (as G1 and G2 did).

This will take a few decades, with G3 making its closest pass in 20 years and G4 and G5 taking decades longer. In the meantime, the team hopes to learn more about these “puffy” star-like objects by following their dynamical evolution using Keck’s OSIRIS instrument. As Ciurlo stated:

“Understanding G-objects can teach us a lot about the Galactic Center’s fascinating and still mysterious environment. There are so many things going on that every localized process can help explain how this extreme, exotic environment works.”

And be sure to check out this video of the presentation, which takes place from 18:30 until 30:20:

Further Reading: Keck Observatory

Weekly Space Hangout – February 3, 2017: Meredith Rawls & the LSST

Host: Fraser Cain (@fcain)

Special Guest: Meredith Rawls

Meredith is a Postdoctoral Researcher in the Department of Astronomy at the University of Washington. She writes software to prepare for the coming onslaught of data from the Large Synoptic Survey Telescope and studies weird binary stars. She is also the lead organizer of the ComSciCon-Pacific Northwest workshop for STEM graduate students in Seattle this March. Meredith holds degrees in physics and astronomy from Harvey Mudd College, San Diego State University, and New Mexico State University. When she’s not science-ing or telling people all about it, she plays viola, volunteers at summer camp, and advocates for more equity and less light pollution.

Guests:

Paul M. Sutter (pmsutter.com / @PaulMattSutter)
Kimberly Cartier ( KimberlyCartier.org / @AstroKimCartier )

Their stories this week:
Oxygen on the moon

Nearby “super-void” shapes galaxy motion

First science from Keck’s vortex coronograph

We use a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!

If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!

If you would like to sign up for the AstronomyCast Solar Eclipse Escape, where you can meet Fraser and Pamela, plus WSH Crew and other fans, visit our site linked above and sign up!

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page

A Moon With Two Suns: Making Art from Science

A view of Kepler 47c and binary stars. ©Digital Drew. All rights reserved.

What would it look like on a hypothetical icy moon orbiting the exoplanet Kepler 47c? Perhaps something like this.

This is an illustration by an artist who goes by the name Digital Drew on Flickr. Drew creates landscapes of imagined alien worlds orbiting stars (and sometimes planets) that actually exist in the Universe. With 3D software, a little science and a lot of imagination, Drew shows us what skies might look like on other planets.

Kepler 47c (KOI-3154.02) is a Neptune-sized exoplanet orbiting a binary star pair 4,600 light-years away. It is part of the first circumbinary system ever discovered — one of at least two planets orbiting a pair of stars. In the image here, Kepler 47c is seen at upper left.

681737main_K47system_diagram_4x3_946-710What makes this exoplanet so exciting is that it is within the habitable zone around the stellar pair. So even though the planet itself may be a gas giant and thus not particularly suitable for life, any moons it has in orbit just might be.

While its slightly smaller planetary companion Kepler 47b orbits much too closely to the twin suns for water to exist as a liquid, 47c’s orbit is much farther out, completing one revolution every 303 days. Mainly illuminated by a star like our Sun but about 15% dimmer, this is a region where you could very well find a large rocky moon with conditions similar to Earth’s.

Fly a spacecraft over its higher elevations and you just might see a scene like this, a double sunset over a glacier-filled valley with a crescent gas giant dominating the sky. (Makes one wonder what the balmier regions might look like!)

“Unlike our sun, many stars are part of multiple-star systems where two or more stars orbit one another. The question always has been — do they have planets and planetary systems? This Kepler discovery proves that they do. In our search for habitable planets, we have found more opportunities for life to exist.”

– William Borucki, Kepler mission principal investigator (Sept. 2012)

And as more giant planets are discovered within their system’s habitable zones, the more there’s a chance that habitable moons could exist — or perhaps even be more common than habitable planets! Just recently the citizen science project Planet Hunters announced the potential exoplanet PH2 b, a Jupiter-sized world that orbits within a habitable zone. In our Solar System Jupiter has lots of moons; PH2 b could very well have a large number of moons of its own, any number of them with liquid water on their surfaces and temperatures “just right” for life.

Read more: Exciting Potential for Habitable Exomoons

While it will likely be quite some time before we see any direct observations of an actual exomoon, and possibly never from one, we must rely on the work of artists like Digital Drew to illustrate the many possibilities that exist.

See more of Drew’s work on his Flickr page here, and read more about the discovery of the Kepler 47 system here.

Inset image: Diagram of the Kepler 47 system compared to the inner Solar System. Credit: NASA/JPL-Caltech/T. Pyle.

Weekly SkyWatcher’s Forecast: June 18-24, 2012

Greetings, fellow SkyWatchers! Let’s begin the week with some awesome galactic studies and enjoy a meteor shower during Summer Solstice! We’ll be studying variable stars, the planet Mars, Saturn, the Moon and Mercury, too! There’s always a bit of astronomy history and some unusual things to learn about. When you’re ready, just meet me in the back yard…

Monday, June 18 – With dark skies on our side, we’ll spend the next few days concentrating on a very specific region of the night sky. Legend tells us the constellation of Crater is the cup of the gods – cup befitting the god of the skies, Apollo. Who holds this cup, dressed in black? It’s the Raven, Corvus. The tale is a sad one – a story of a creature sent to fetch water for his master, only to tarry too long waiting on a fig to ripen. When he realized his mistake, the sorry Raven returned to Apollo with his cup and brought along the serpent Hydra in his claws as well. Angry, Apollo tossed them into the sky for all eternity and it is in the south they stay until this day.

For the next few days, it will be our pleasure to study the Cup and the Raven. The galaxies I have chosen are done particularly for those of us who still star hop. I will start with a “marker” star that should be easily visible unaided on a night capable of supporting this kind of study. The field stars are quite recognizable in the finder and this is an area that takes some work. Because these galaxies approach magnitude 13, they are best suited to the larger telescope.

Now, let’s go between map and sky and identify both Zeta and Eta Crater and form a triangle. Our mark is directly south of Eta the same distance as between the two stars. At low power, the 12.7 magnitude NGC 3981 (Right Ascension: 11 : 56.1 – Declination: -19 : 54) sits inside a stretched triangle of stars. Upon magnification, an elongated, near edge-on spiral structure with a bright nucleus appears. Patience and aversion makes this “stand up” galaxy appear to have a vague fading at the frontiers with faint extensions. A moment of clarity is all it takes to see tiny star caught at the edge.

Tuesday, June 19 – New Moon! Tonight’s first study object, 12.7 magnitude NGC 3956 (Right Ascension: 11 : 54.0 – Declination: -20 : 34) is about a degree due south of NGC 3981. When first viewed, it appears as edge-on structure at low power. Upon study it takes on the form of a highly inclined spiral. A beautiful multiple star, and a difficult double star also resides with the NGC 3956 – appearing almost to triangulate with it. Aversion brings up a very bright core region which over the course of time and study appears to extend away from the center, giving this very sweet galaxy more structure than can be called from it with one observation.

Our next target is a little more than two degrees further south of our last study. The 12.8 magnitude NGC 3955 (Right Ascension: 11 : 54.0 – Declination: -23 : 10) is a very even, elongated spiral structure requiring a minimum of aversion once the mind and eye “see” its position. Not particularly an impressive galaxy, the NGC 3955 does, however, have a star caught at the edge as well. After several viewings, the best structure I can pull from this one is a slight concentration toward the core.

Now we’ll study an interacting pair and all that is required is that you find 31 Corvii, an unaided eye star west of Gamma and Epsilon Corvii. Now we’re ready to nudge the scope about one degree north. The 11th magnitude NGC 4038/39 (Right Ascension: 12 : 01.9 – Declination: -18 : 52) is a tight, but superior pair of interacting galaxies. Often referred to as either the “Ringtail” or the “Antenna”, this pair deeply captured the public’s imagination when photographed by the Hubble. (Unfortunately, we don’t have the Hubble, but what we have is set of optics and the patience to find them.) At low power the pair presents two very stellar core regions surrounded by a curiously shaped nebulosity. Now, drop the power on it and practice patience – because it’s worth it! When that perfect moment of clarity arrives, we have crackling structure. Unusual, clumpy, odd arms appear at strong aversion. Behind all this is a galactic “sheen” that hints at all the beauty seen in the Hubble photographs. It’s a tight little fellow, but worth every moment it takes to find it.

Return to 31 Corvii and head one half degree northwest to discover 11.6 magnitude NGC 4027 (Right Ascension: 11 : 59.5 – Declination: -19 : 16). Relatively large, and faint at low power, this one also deserves both magnification and attention. Why? Because it rocks! It has a wonderful coma shape with a single, unmistakable bold arm. The bright nucleus seems to almost curl along with this arm shape and during aversion a single stellar point appears at its tip. This one is a real treat!

Wednesday, June 20 – Today marks the official date of 2012 Summer Solstice!

With no Moon to contend with in the predawn hours, we welcome the “shooting stars” as we pass through another portion of the Ophiuchid meteor stream. The radiant for this pass will be nearer Sagittarius and the fall rate varies from 8 to 20, but it can sometimes produce unexpectedly more.

Tonight let’s look to the sky again and fixate on Eta Crater – our study lay one half degree southeast. The 12.8 magnitude NGC 4033 (Right Ascension: 12 : 00.6 – Declination: -17 : 51) is a tough call even for a large scope. Appearing elliptical at low power, it does take on some stretch at magnification. It is smallish, even and quite unremarkable. It requires good aversion and a bit of patience to find. Good luck!

The last of our studies resides by a star, one degree west of Beta Corvii. In order to “see” anything even remotely called structure in NGC 4462 (Right Ascension: 12 : 29.3 – Declination: -23 : 10), this one is a high power only galaxy that is best when the accompanying star is kept out of the field as much as possible. It holds a definite stellar nucleus and a concentration that pulls away from it making it almost appear barred. On an exceptional night with a large scope, wide aversion and moments of clarity show what may be three to four glints inside the structure. Ultra tiny pinholes in another universe? Or perhaps an unimaginably huge, bright globular clusters? While attention is focused on trying to draw out these points, you’ll notice this galaxy’s structure much more clearly. Another true beauty and fitting way to end this particular study field!

Thursday, June 21 – Keep an eye out for the exiting planet Mars! It’s been on the move and has now crossed the border of Virgo and returned to Leo. Have you noticed it quickly changing in both apparent brightness and size? It won’t be long until it’s gone! And speaking of planets on the move, have you spotted Mercury yet? You can find the swift little planet low on the western horizon just after sunset. Look for it just to the south of Castor and Pollux!

For challenging larger telescope studies, return to eastern edge of Mare Crisium and Promontorium Agarum to identify shallow crater Condorcet to its east. Look along the shore of the mare for a mountain to the south known as Mons Usov. Just to its north Luna 24 landed and directly to its west are the remains of Luna 15. We’ll study more about them in the future. Can you spot the tiny dark well of crater Fahrenheit nearby? Continue with your telescope north of Mare Crisium for even more challenging features such as northeast limb studies Mare Smythii and Mare Marginis. Between them you will see the long oval crater Jansky – bordered by Jansky A at the very outer edge.

While you’re out tonight, take a look at the skies for a circlet of seven stars that reside about halfway between orange Arcturus and brilliant blue/white Vega. This quiet constellation is named Corona Borealis – or the “Northern Crown.” Just northwest of its brightest star is a huge concentration of over 400 galaxies that reside over a billion light-years away from us. This area is so small from our point of view that we could cover it with our thumbnail held at arm’s length!

For variable star fans, let’s explore Corona Borealis and focus our attention on S – located just west of Theta – the westernmost star in the constellation’s arc formation. At magnitude 5.3, this long-term variable takes almost a year to go through its changes; usually far outshining the 7th magnitude star to its northeast – but will drop to a barely visible magnitude 14 at minimum. Compare it to the eclipsing binary U Coronae Borealis about a degree northwest. In slightly over three days this Algol-type will range by a full magnitude as its companions draw together.

Friday, June 22 – Today celebrates the founding of the Royal Greenwich Observatory in 1675. That’s 332 years of astronomy! Also on this date in history, in 1978, James Christy of the US Naval Observatory in Flagstaff Arizona discovered Pluto’s satellite Charon.

If you’d like to practice some unaided eye astronomy, then look no further than the western skyline as the Sun sets. At twilight you’ll first notice the very slender crescent Moon – but don’t delay your observations as you can spot Mercury to the west! The inner planet will set very fast, so you’ll need an open horizon. But that’s not all… the speedy little dude is lined up perfectly with Castor and Pollux! With the foursome nearly “in a row” this will make a very cool apparition to remind friends and family to watch for!

Now, grab your favorite optics for a selenographic treat tonight return to the area just north of Mare Crisium area to observe spectacular crater Cleomides. This two million year old crater is separated from Crisium by some 60 kilometers of mountainous terrain. Telescopically, Cleomides is a true delight at high power. To Cleomides’ east, begin by identifying Delmotte, and to the northwest, Trailes and Debes. About twice Clemoides’ width northwest, you will see a sharply well-defined Class I crater Geminus. Named for the Greek astronomer and mathematician Geminos, this 86 kilometer wide crater shows a smooth floor and displays a long, low dune across its middle.

When you’re finished, point your binoculars or telescopes back towards Corona Borealis and about three fingerwidths northwest of Alpha for variable star R (Ra 15. 48.6 Dec +28 09). This star is a total enigma. Discovered in 1795, most of the time R carries a magnitude near 6, but can drop to magnitude 14 in a matter of weeks – only to unexpectedly brighten again! It is believed that R emits a carbon cloud which blocks its light. When studied at minima, the light curve resembles a “reverse nova,” and has a peculiar spectrum. It is very possible this ancient Population II star has used all of its hydrogen fuel and is now fusing helium to carbon. It’s so odd that science can’t even directly determine its distance!

Saturday, June 23 – If you missed yesterday’s apparition of Mercury, then try again tonight. While the small planet might be dim, just look for the brighter pairing of Castor and Pollux above the western horizon at twilight. Can’t find it? Then try this. When you look at this famous pair of stars, judge the distance between the two. Now, apply that same distance and angle to the left (southern) star, Pollux, and you’ve found Mercury! Need more? Then check out the Moon and you’ll see Regulus is about a fistwidth to the east/southeast and Mars is a little more than two handspans to the southeast. Still more? Then continue on from Mars southeast about about another two handspans and you’ll see the pairing of Spica and Saturn!

Using your telescope tonight on the Moon will call up previous study craters, Atlas and Hercules to the lunar north. If you walk along the terminator to the due west of Atlas and Hercules, you’ll see the punctuation of 40 kilometer wide Burg just emerging from the shadows. While it doesn’t appear to be a grand crater just yet, it has a redeeming feature – it’s deep – real deep. If Burg were filled with water here on Earth, it would require a deep submergence vehicle like ALVIN to reach its 3680 meter floor! This class II crater stands nearly alone on an expanse of lunarscape known as Lacus Mortis. If the terminator has advanced enough at your time of viewing, you may be able to see this walled-plain’s western boundary peeking out of the shadows.

While we’re out, let’s have a look at Delta Serpens. To the eye and binoculars, 4th magnitude Delta is a widely separated visual double star… But power up in the telescope to have a look at a wonderfully difficult binary. Divided by no more than 4 arc seconds, 210 light-year distant Delta and its 5th magnitude companion could be as old as 800 million years and on the verge of becoming evolved giants. Separated by about 9 times the distance of Pluto from our Sun, the white primary is a Delta Scuti-type variable which changes subtly in less than four hours. Although it takes the pair 3200 years to orbit each other, you’ll find Delta Serpens to be an excellent challenge for your optics.

Sunday, June 24 – On this day in 1881, Sir William Huggins made the first photographic spectrum of a comet (1881 III) and discovered cyanogen (CN) emission at violet wavelengths. Unfortunately, his discovery caused public panic around 29 years later when Earth passed through the tail of Halley’s Comet. What a shame the public didn’t realize that cyanogens are also released organically! More than fearing what is in a comet’s tail, they should have been thinking about what might happen should a comet strike. Tonight look at the wasted Southern Highland area of the Moon with new eyes… Many of these craters you see were caused by impacts – some as large as the nucleus of Halley itself.

Now let’s pick up a binocular curiosity located on the northeast shore of Mare Serenitatis. Re-identify the bright ring of Posidonius, which contains several equally bright points both around and within it – and look at Mare Crisium and get a feel for its size. A little more than one Crisium’s length west of Posidonius you’ll meet Aristotle and Eudoxus. Drop a similar length south and you will be at the tiny, bright crater Linne on the expanse of Mare Serenitatis. So what’s so cool about this little white dot? With only binoculars you are resolving a crater that is one mile wide, in a seven mile wide patch of bright ejecta – from close to 400,000 kilometers away! While you were there, did you notice how much Proclus has changed tonight? It is now a bright circle and beginning to show bright lunar rays…

Before we head for deep sky, be sure to at least take a look at Saturn and Mars. Right now the Ring King has reached its greatest westward position and will begin its tour back to the east. Now, check out Mars’ position to the west and measure with your hands roughly how far apart they are. At this point they are separated by about two handspans. Check again in a few weeks to see planetary motion displayed right before your eyes!

Now let’s turn binoculars or telescopes towards magnitude 2.7 Alpha Librae – the second brightest star in the celestial “Scales.” Its proper name is Zuben El Genubi, and even as “Star Wars” as that sounds, the “Southern Claw” is actually quite close to home at a distance of only 65 light-years. No matter what size optics you are using, you’ll easily see Alpha’s 5th magnitude companion widely spaced and sharing the same proper motion. Alpha itself is a spectroscopic binary which was verified during an occultation event, and its inseparable companion is only a half magnitude dimmer according to the light curves. Enjoy this easy pair tonight!

Until next week? Ask for the Moon… But keep on reaching for the stars!

Weekly SkyWatcher’s Forecast: April 23-29, 2012

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Greetings, fellow SkyWatchers! What a great week to just enjoy some great unaided eye astronomy observations. Who can resist the beautiful appearance of Mars in Leo? Also this week, you’ll enjoy not one – but two – meteor showers as the Mu Virginids come to town mid-week and the Bootids light up the weekend. Get ready to enjoy bright stars, find planets, explore lunar features, learn some astronomy history and much more! When ever you’re ready, meet me in the back yard…

Monday, April 23 – Pioneer quantum physicist Max Planck was born on this day in 1858. In 1900, Max developed the Planck equation to explain the shape of blackbody spectra (a function of temperature and wavelength of emission). A “blackbody” is any object that absorbs all incident radiation – regardless of wavelength. For example, heated metal has blackbody properties because the energy it radiates is thermal. The blackbody spectrum’s shape remains constant, and the peak and height of an emitter can be measured against it – be it cosmic background radiation – or our own bodies.

Now, let’s put this knowledge into action. Stars themselves approximate blackbody radiators, because their temperature directly controls the color we see. A prime example of a “hot” star is Alpha Virginis, better known as Spica. Compare its color to the cooler Arcturus… What colors do you see? There are other astronomical delights that radiate like blackbodies over some or all parts of the spectrum as well. You can observe a prime example in a nebula such as M42, in Orion. By examining the radio portion of the spectrum, we find the temperature properly matches that of electrons involved in the process of fluorescence. Much like a common household fixture, this process is what produces the visible light we can see.

Tuesday, April 24 – Today in 1970, China launched its first satellite. Named Shi Jian 1, it was a successful technological and research craft. This achievement made China the fifth country to send a vessel into space.

Tonight see if you can spot the tender beginnings of the Moon after sunset. Observers take pleasure in sweeping the sky with small scopes and binoculars in hopes of finding the thinnest possible lunar crescent. And speaking of crescents, did you spot Venus close to the Moon? Why not take out your telescope and see what phase Venus is now in. If you don’t have a filter to cut its bright glare, try wearing sunglasses!

No telescope? No problem. You can still do some very awesome astronomy with just your eyes! Begin with locating the northern constellation of Ursa Major – most commonly known as the “Big Dipper”. Take note of the curve of the Dipper’s “handle” and trace it from the bottom of the cup and continue on the “Arc to Arcturus”. Keep moving, because now you’re going to “Speed on to Spica”! Once you’ve located this bright, blue/white star, simply look to its east/southeast (or upper left) for a yellow appearing “star”. That’s no star… That’s Saturn!

Now let’s have a look at 140 light-year distant Epsilon Hydrae – the northernmost star in the small circlet east of Procyon. While it and Rho will make a beautiful visual double for binoculars, Epsilon itself is a multiple system. Its A and B components are a tough split for any scope, but the 8th magnitude C star is easier. The D component is a dwarf star.

Wednesday, April 25 – Today marks the 15th anniversary of the deployment of Hubble Space Telescope. While everyone in the astronomical community is well aware of what this magnificent telescope “sees,” did you know that you can see it with just your eyes? The HST is a satellite that can be tracked and observed. Visit heavens-above.com and enter your location. This page will provide you with a list of visible passes for your area. Although you can’t see details of the scope itself, it’s great fun to track with binoculars or see the Sun glinting off its surface in a scope.

Tonight our first voyage is to the Moon’s surface. Look along the terminator in the southern quadrant and revisit ancient old crater Furnerius. Named for French Jesuit mathematician George Furner, this crater spans approximately 125 kilometers and is a lunar club challenge. Power up and look for two interior craters. The smaller is crater A and it spans a little less than 15 kilometers and drops to a depth of over 1000 meters. The larger crater C is about 20 kilometers in diameter, but goes far deeper, to more than 1400 meters. That’s about as deep as a coral will grow under the Earth’s oceans!

Keep a watch on the skies while you’re out as the Mu Virginid meteor shower reaches its peak at 7 to 10 per hour. With dark skies tonight, you still might catch one of these medium speed meteors radiating from a point near the constellation of Libra.

Thursday, April 26 – On this date in 1920, the Shapely-Curtis debate raged in Washington on the nature of and distance to spiral nebulae. Shapely claimed they were part of one huge galaxy to which we all belonged, while Curtis maintained they were distant galaxies of their own. Thirteen years later on the same date, Arno Penzias was born. He went on to become a Nobel Prize winner for his part in the discovery of the cosmic microwave background radiation, through searching for the source of the “noise” coming from a simple horn antenna. His discovery helped further our understanding of cosmology in ways that Shapely and Curtis could have never dreamed of.

Perhaps they dreamed of Moon? We’ve got Moon! No matter, what we really want to do is revisit and study a changeable, sometimes transient, and eventually bright feature on the lunar surface – crater Proclus. At around 28 kilometers in diameter and 2400 meters deep, Proclus will appear on the terminator on the west mountainous border of Mare Crisium. For many viewers tonight, it will seem to be about 2/3 black, but 1/3 of the exposed crater will be exceptionally brilliant – and with good reason. Proclus has an albedo, or surface reflectivity, of about 16%, which is an unusually high value for a lunar feature. Watch this area over the next few nights as two rays from the crater will widen and lengthen, extending approximately 322 kilometers to both the north and south. Congratulations on another lunar club challenge!

Friday, April 27 – Tonight we’re heading towards the lunar surface to view a very fine old crater on the northwest shore of Mare Nectaris – Theophilus. Slightly south of mid-point on the terminator, this crater contains an unusually large multiple-peaked central mountain which can be spotted in binoculars. Theophilus is an odd crater, one that is a parabola – with no area on the floor being flat. It stretches across a distance of 100 kilometers and dives down 440 meters below the surface. Tonight it will appear dark, shadowed by its massive west wall, but look for sunrise on its 1400 meter summit!

Now, let’s try picking up a globular cluster in Hydra that is located about 3 fingerwidths southeast of Beta Corvus and just a breath northeast of double star A8612 – M68 (Right Ascension:12 : 39.5 – Declination: -26 : 45). This class X globular was discovered in 1780 by Charles Messier and first resolved into individual stars by William Herschel in 1786. At a distance of approximately 33,000 light-years, it contains at least 2000 stars, including 250 giants and 42 variables. It will show as a faint, round glow in binoculars, and small telescopes will perceive individual members. Large telescopes will fully resolve this small globular to the core!

While you’re out, have a look at 27 Hydrae about a fingerwidth southwest of Alpha. It’s an easy double for any equipment with its slightly yellow 5th magnitude primary and distant, white, 7th magnitude secondary. Although it is wide, the pair is a true binary system.

Saturday, April 28 – Today was a very busy day in astronomy history. Newton published his Principia in 1686 on April 28. In 1774, Francis Baily was born. He went on to revise star catalogs and explain the phenomenon at the beginning and ending of a total solar eclipse which we know as “Baily’s Beads.” 1900 saw the birth of Jan Hendrick Oort, who quantified the Milky Way’s rotation characteristics and envisioned the vast, spherical area of comets outside our solar system that we now call the Oort Cloud. Last, but not least, was the birth of Bart Jan Bok in 1906 who studied the structure and dynamics of the Milky Way.

Tonight’s outstanding lunar feature will be crater Maurolycus just southwest of the three rings of Theophilus, Cyrillus and Catharina. This lunar club challenge spans 114 kilometers and goes below the lunar surface by 4730 meters. Be sure to look for Gemma Frisius just to its north.

Now let’s check out a dandy little group of stars that are about a fistwidth southeast of Procyon and just slightly more than a fingerwidth northeast of M48. Called C Hydrae, this group isn’t truly gravitationally bound, but is a real pleasure to large binoculars and telescopes of all sizes. While they share similar spectral types, this mixed magnitude collection will be sure to delight you!

For SkyWatchers, no equipment is necessary to enjoy the Alpha Bootid meteor shower – despite the Moon. Pull up a comfortable seat and face orange Arcturus as it climbs the sky in the east. These slow meteors have a fall rate of 6 to 10 per hour and leave very fine trails, making an evening of quiet contemplation most enjoyable.

Sunday, April 29 – Before we explore space, let’s have a look at the Moon and the close apparition of Regulus and Mars! The three make a wonderful “line up” the night sky! Now, let’s start our lunar observations tonight as challenge craters Cassini and Cassini A come into view just south of the black slash of the Alpine Valley. The major crater spans 57 kilometers and reaches a floor depth of 1240 meters. The challenge is to also spot the central crater A, which is only 17 kilometers wide, yet drops down another 2830 meters below the surface.

While we’re out, have a look at R Hydrae about a fingerwidth east of Gamma – which is a little more than fistwidth south of Spica. R is a beautiful, red, long-term variable first observed by Hevelius in 1662. Located about 325 light-years from us, it’s approaching – but not that fast. Be sure to look for a visual companion star as well!

Until next week? Dreams really do come true when you keep on reaching for the stars!

Many thanks to John Chumack of Galactic Images for his outstanding photo of “Leo In Mars”!

Light Echoes: The Re-Run Of The Eta Carinae “Great Eruption”

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In this modern age, we’re used to catching a favorite program at a later time. We use our DVR equipment and, not so long ago, a VCR to record now and watch later. Once upon a great time ago we relied upon a quaint customer called the “re-run” – the same program broadcast at a later date. However, a re-run can’t occur when it comes to astronomy event… Or can it? Oh, you’re gonna’ love this!

Way back in 1837, Eta Carinae had an event they called the “Great Eruption”. It was an outburst so powerful that it was observable in the southern night sky for 21 years. While it could be seen, sketched and recorded for astronomy posterity, one thing didn’t happen – and that was study with modern scientific instruments. But this great double star was about to do an even greater double-take as the light from the eruption continued away from Earth and on towards some dust clouds. Now, 170 years later, the “Great Eruption” has returned to us again in an effect known as a light echo. Because of its longer path, this re-run only took 17 decades to play again!

“When the eruption was seen on Earth 170 years ago, there were no cameras capable of recording the event,” explained the study’s leader, Armin Rest of the Space Telescope Science Institute in Baltimore, Maryland. “Everything astronomers have known to date about Eta Carinae’s outburst is from eyewitness accounts. Modern observations with science instruments were made years after the eruption actually happened. It’s as if nature has left behind a surveillance tape of the event, which we are now just beginning to watch. We can trace it year by year to see how the outburst changed.”

As one of the largest and brightest systems in the Milky Way, Eta Carinae is at home some 7,500 light years from Earth. During the outburst, it shed around one solar mass for every 20 years it was active and it became the second brightest star in the sky. During that time, its signature twin lobes formed. Being able to study an event like this would help us greatly understand the lives of powerful, massive stars on the eve of destruction. Because it is so close, Eta has also been prime candidate for spectroscopic studies, giving us insight on its behavior, including the temperature and speed of the ejected material.

But there’s more…

Eta Carinae could possibly be considered more famous for its “misbehavior”. Unlike stars of its class, Eta is more of a Luminous Blue Variable – an uber bright star known for periodic outbursts. The temperature of the outflow from Eta Carinae’s central region, for example, is about 8,500 degrees Fahrenheit (5,000 Kelvin), which is much cooler than that of other erupting stars. “This star really seems to be an oddball,” Rest said. “Now we have to go back to the models and see what has to change to actually produce what we are measuring.”

Through the eyes of the U.S. National Optical Astronomy Observatory’s Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile, Rest and the team first spotted the light echo in 2010 and then again in 2011 while comparing visible light observations. From there he quickly compared it with another set of CTIO observations taken in 2003 by astronomer Nathan Smith of the University of Arizona in Tucson and pieced together the 20 year old puzzle. What he saw was nothing short of amazing…

“I was jumping up and down when I saw the light echo,” said Rest, who has studied light echoes from powerful supernova blasts. “I didn’t expect to see Eta Carinae’s light echo because the eruption was so much fainter than a supernova explosion. We knew it probably wasn’t material moving through space. To see something this close move across space would take decades of observations. We, however, saw the movement over a year’s time. That’s why we thought it was probably a light echo.”

While the images would appear to move with time, this is only an “optical illusion” as each parcel of light information arrives at a different time. Follow up observations include more spectroscopy pinpointing the outflow’s speed and temperature – where ejected material was clocked at speed of roughly 445,000 miles an hour (more than 700,000 kilometers an hour) – a speed which matched computer modeling predictions. Rest’s group also cataloged changes in the light echo intensity using the Las Cumbres Observatory Global Telescope Network’s Faulkes Telescope South in Siding Spring, Australia. Their results were then compared the historic measurements during the actual event and the peak brightness findings matched!

You can bet the team is continuing to monitor this re-run very closely. “We should see brightening again in six months from another increase in light that was seen in 1844,” Rest said. “We hope to capture light from the outburst coming from different directions so that we can get a complete picture of the eruption.”

Original Story Source: HubbleSite News Release. For Further Reading: Nature Science Paper by A. Rest et al.

When Stars Play Planetary Pinball

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Many of us remember playing pinball at the local arcade while growing up; it turns out that some stars like it as well. Binary stars can play tug-of-war with an unfortunate planet, flinging it into a wide orbit that allows it to be captured by first one star and then the other, in effect “bouncing” it between them before it is eventually flung out into deep space.

The new paper, by Nick Moeckel and Dimitri Veras of the University of Cambridge, will be published in a future issue of Monthly Notices of the Royal Astronomical Society.

The gravitational pull of large gas giant planets can affect the orbits of smaller planets; that scenario is thought to have occurred in our own solar system. In some cases, the smaller planet may be flung into a much wider orbit, perhaps even 100 times wider than Pluto’s. In the case of single stars, that’s normally how it ends. In a binary star system, however, the two stars may play a game of “cosmic pinball” with the poor planet first.

Moeckel and Dimitri conducted simulations of binary star systems, with two sun-like stars orbiting each other at distances between 250 and 1,000 times the distance of the Earth from the Sun. Each star had its own set of planets. The planetary systems would often become unstable, resulting in one of the planets being flung out, where it could be subsequently captured by the other star’s gravity. Since the new orbit around the second star would also tend to be quite wide, the planet would be vulnerable to recapture again by the first star. This could continue for a long time, and the simulations indicated that more than half of all planets initially ejected would get caught in this game of “cosmic pinball.”

In the end, some planets would settle back into an orbit around one of the stars, but the majority would escape both stars altogether, finally being flung out into deep space forever.

According to Moeckel, “Once a planet starts transitioning back and forth, it’s almost certainly at the beginning of a trip that will end in deep space.”

We are fortunate to live in a solar system where our planet is in a nice, stable orbit. For others out there who may not be so lucky, it would be like living through a disaster movie played out over eons.

The paper is available here.

Recycling Pulsars – The Millisecond Matters…

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It’s a millisecond pulsar… a rapidly rotating neutron star and it’s about to reach the end of its mass gathering phase. For ages the vampire of this binary system has been sucking matter from a donor star. It has been busy, spinning at incredibly high rotational speeds of about 1 to 10 milliseconds and shooting off X-rays. Now, something is about to happen. It is going to lose a whole lot of energy and age very quickly.

Astrophysicist Thomas Tauris of Argelander-Institut für Astronomie and Max-Planck-Institut für Radioastronomie has published a paper in the February 3 issue of Science where he has shown through numerical equations the root of stellar evolution and accretion torques. In this model, millisecond pulsars are shown to dissipate approximately half of their rotational energy during the last phase of the mass-transfer process and just before it turns into a radio source. Dr. Tauris’ findings are consistent with current observations and his conclusions also explain why a radio millisecond pulsar appears age-advanced over their companion stars. This may be the answer as to why sub-millisecond pulsars don’t exist at all!

“Millisecond pulsars are old neutron stars that have been spun up to high rotational frequencies via accretion of mass from a binary companion star.” says Dr. Tauris. “An important issue for understanding the physics of the early spin evolution of millisecond pulsars is the impact of the expanding magnetosphere during the terminal stages of the mass-transfer process.”

By drawing mass and angular momentum from a host star in a binary system, a millisecond pulsar lives its life as a highly magnetized, old neutron star with an extreme rotational frequency. While we might assume they are common, there are only about 200 of these pulsar types known to exist in galactic disk and globular clusters. The first of these millisecond pulsars was discovered in 1982. What counts are those that have spin rates between 1.4 to 10 milliseconds, but the mystery lay in why they have such rapid spin rates, their strong magnetic fields and their strangely appearing ages. For example, when do they switch off? What happens to the spin rate when the donor star quits donating?

“We have now, for the first time, combined detailed numerical stellar evolution models with calculations of the braking torque acting on the spinning pulsar”, says Thomas Tauris, the author of the present study. “The result is that the millisecond pulsars lose about half of their rotational energy in the so-called Roche-lobe decoupling phase. This phase is describing the termination of the mass transfer in the binary system. Hence, radio-emitting millisecond pulsars should spin slightly slower than their progenitors, X-ray emitting millisecond pulsars which are still accreting material from their donor star. This is exactly what the observational data seem to suggest. Furthermore, these new findings can help explain why some millisecond pulsars appear to have characteristic ages exceeding the age of the Universe and perhaps why no sub-millisecond radio pulsars exist.”

Thanks to this new study we’re now able to see how a spinning pulsar could possibly brake out of an equilibrium spin. At this age, the mass-transfer rate slows down and affects the magnetospheric radius of the pulsar. This in turn expands and forces the incoming matter to act as a propeller. The action then causes the pulsar to slow down its rotation and – in turn – slow its spin rate.

“Actually, without a solution to the “turn-off” problem we would expect the pulsars to even slow down to spin periods of 50-100 milliseconds during the Roche-lobe decoupling phase”, concludes Thomas Tauris. “That would be in clear contradiction with observational evidence for the existence of millisecond pulsars.”

Original Story Source: Max-Planck-Institut für Radioastronomie News Release>. For Further Reading: Spin-Down of Radio Millisecond Pulsars at Genesis.

Tatooine the Sequel: Kepler Finds Two More Exoplanets Orbiting Binary Stars

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For exoplanet fans, this week has been an exciting one, with some amazing new discoveries being announced at the American Astronomical Society meeting in Austin, Texas – our galaxy is brimming with planets, probably billions, and the smallest known planets have been found (again), with one about the size of Mars. But that’s not all; it was also announced that Kepler has found not one but two more planets orbiting binary stars!

The two star systems are Kepler-34 and Kepler-35; they consist of double stars which orbit each other and are about 4,900 and 5,400 light-years from Earth. The two new planets, Kepler-34b and Kepler-35b, each orbit one of these pairs of stars and are both about the size of Saturn. Since they orbit fairly close to their stars, they are not in the habitable zones; Kepler 34-b completes an orbit in 289 days and Kepler-35b in 131 days. It’s more the fact that they orbit double stars that makes them so interesting.

This is now the third planet found in a binary star system. The first, Kepler-16b, was nicknamed Tatooine as it was reminiscent of the world orbiting two suns in the Star Wars films. Until recently, it was unknown if any such star systems had planetary companions. It was considered possible, although unlikely, and remained only a theory. But now, the view is that there may indeed be a lot of them out there, just as planets are now apparently common around single stars. That’s good news for planet-hunters, as most stars in our galaxy are binaries.

According to William Welsh of San Diego State University who participated in the study, “This work further establishes that such ‘two sun’ planets are not rare exceptions, but may in fact be common, with many millions existing in our galaxy. This discovery broadens the hunting ground for systems that could support life.”

Eric B. Ford, associate professor of astronomy at the University of Florida, stated: “We have long believed these kinds of planets to be possible, but they have been very difficult to detect for various technical reasons. With the discoveries of Kepler-16b, 34b and 35b, the Kepler mission has shown that the galaxy abounds with millions of planets orbiting two stars.”

The hope now is that Kepler will continue until 2016 to be able to further refine its findings so far. That will require a mission extension, but scientists involved are optimistic they will get it.

According to Ford, “Astronomers are practically begging NASA to extend the Kepler mission until 2016, so it can characterize the masses and orbits of Earth-size planets in the habitable zone. Kepler is revolutionizing so many fields, not just planetary science. It would be a shame not to maximize the scientific return of this great observatory. Hopefully common sense will prevail and the mission will continue.”

Yes, indeed.

The study was published January 11, 2012 in the journal Nature (payment or subscription required for access to full article).

See also PhysOrg.com for a good overview of the new findings.

Dodging Black Hole Bullets

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In mid-2009 a binary star system cataloged as H H1743–322 shot off something very unusual. Poised about 28,000 light years distant in the direction of the constellation of Scorpius, this rather ordinary system made up of a normal star and unknown mass black hole was busy exchanging mass. The pair orbits in mere days with a stream of material flowing continuously between them. This gas causes a flat accretion disk measuring millions of miles across to form and it is centered on the black hole. As the matter twirls toward the center, it becomes compressed and heats to tens of millions of degrees, spitting out X-rays… and bullets.

Utilizing data from NASA’s Rossi X-ray Timing Explorer (RXTE) satellite and the National Science Foundation’s (NSF) Very Long Baseline Array (VLBA) radio telescope, an international team of astronomers were able to confirm the moment a black hole located within our galaxy fired a super speedy clump of gas into surrounding space. Blasting forth at about one-quarter the speed of light, these “bullets” of ionized gas are hypothesized to have originated from an area just outside the black hole’s event horizon.

“Like a referee at a sports game, we essentially rewound the footage on the bullets’ progress, pinpointing when they were launched,” said Gregory Sivakoff of the University of Alberta in Canada. He presented the findings today at the American Astronomical Society meeting in Austin, Texas. “With the unique capabilities of RXTE and the VLBA, we can associate their ejection with changes that likely signaled the start of the process.”

As we have learned, some of the matter headed toward the center of a black hole can be ejected from the accretion disk as opposing twin jets. For the most part, these jets are a constant stream of particles, but can sometimes form into strong “outflows” which get spit out – rapid fire – as gaseous blobs. In early June 2009, H1743–322 did just that… and astronomers were on hand observing with RXTE, the VLBA, the Very Large Array near Socorro, N.M., and the Australia Telescope Compact Array (ATCA) near Narrabri in New South Wales. During this time they were able to confirm the happenings through X-ray and radio data. From May 28 to June 2, things were nominal “though RXTE data show that cyclic X-ray variations, known as quasi-periodic oscillations or QPOs, gradually increased in frequency over the same period” and by June 4th, ATCA verified that activity had pretty much sloughed off. By June 5th, even the QPOs were gone.

Then it happened…

On the same day that everything went totally quiet, H1743–322 fired off a bullet! Radio emissions jumped and a highly accurate and detailed VLBA image disclosed a energetic missile of gas blasting forth along a jet trajectory. The very next day a second bullet took out in the opposite direction. But this wasn’t the curious part of the event… It was the timing. Up to this point, researchers speculated that a radio outburst accompanied the firing of the gas bullet, but VLBA information showed they were launched around 48 hours in advance of the major radio flare. This information will be published in the Monthly Notices of the Royal Astronomical Society.

Radio imaging by the Very Long Baseline Array (top row), combined with simultaneous X-ray observations by NASA's RXTE (middle), captured the transient ejection of massive gas "bullets" by the black hole binary H1743-322 during its 2009 outburst. By tracking the motion of these bullets with the VLBA, astronomers were able to link the ejection event to the disappearance of X-ray signals seen in RXTE data. These signals, called quasi-periodic oscillations (QPOs), vanished two days earlier than the onset of the radio flare that astronomers previously had assumed signaled the ejection. (Credit: NRAO and NASA's Goddard Space Flight Center)

“This research provides new clues about the conditions needed to initiate a jet and can guide our thinking about how it happens,” said Chris Done, an astrophysicist at the University of Durham, England, who was not involved in the study.

These are just mini-ammo compared to what happens in the center of an active galaxy. They don’t just fire bullets – they blast off cannons. A massive black hole weighing in a millions to billions of times the mass of the Sun can shoot off its load across millions of light years!

“Black hole jets in binary star systems act as fast-forwarded versions of their galactic-scale cousins, giving us insights into how they work and how their enormous energy output can influence the growth of galaxies and clusters of galaxies,” said lead researcher James Miller-Jones at the International Center for Radio Astronomy Research at Curtin University in Perth, Australia.

Original Story Source: NASA News Feature.