Universe Today

January 7, 2009December 24, 2015 by Nancy Atkinson

This Week’s Where In The Universe Challenge

This week’s Where In The Universe Challenge has a new twist. This image was actually submitted by one of our readers, Wienie van der Oord from Israel. Its quite an interesting image, don’t you agree?! I’ll not give any hints as to where Wienie got the image, or what it is, or whether this image can be found anywhere else on the web (for those of you that like to search online for the image and link the answer!). You’ll have to wait until tomorrow (Thursday) for the answer to be revealed for this week’s Challenge. My only hope is that some conspiracy theorist types don’t see this and claim this image is proof of life on an alien world. Or, possibly, could it really be…..?!

Check back tomorrow to find out! It will be interesting to see the guesses on this one, so submit ’em in the comment section.

UPDATE (1/8): The answer has now been posted below. No peeking before you make your guess!

This image was certainly a lot of fun, and it’s one you can’t find anywhere else on the internet. It was sent in by UT reader Wienie van der Oord, and I’ll let her explain what it is:

“After a short rainfall in the Arava desert in Israel, a tiny desert plant developed a root and two leaves and looked like an “alien” running over another planet,” she said. The raindrops formed the “craters” in the desert sand, and the root going down into the ground suspended the seed above ground, making it look like this little bunny-like creature was scooting across an alien world. The plant in question that has just sprouted is the Zygophyllum Dumosum, a shrub native to Israel that can be found in the Judean desert and Dead Sea Valley, the Negev Hills and Arava Valley. Wienie sent another image too, after she scooped up the little “alien” and put it in her hand:

ZYGOPHYLLUM DUMOSUM sprout. Image credit: Wienie van der Oord

If you’re partial to plants, here’s a Wildflower of Israel website where you can find out more about this shrub.

Thanks to Wienie for sharing this very “cute” image. If you have an original photograph you’d like to submit or a suggested image for a Where In The Universe Challenge, you can send them to me. To find my email address you have to visit my personal website, nancyatkinson.com . Sorry, I’m not going to be spammed to death by posting my email address!

January 7, 2009December 24, 2015 by Tammy Plotner

Sagitta

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Sagitta belongs to the original 48 constellations charted by Ptolemy and it remains one of the 88 modern constellations defined by the International Astronomical Union. Located north of the ecliptic plane, it spans 80 square degrees of sky, ranking 86th in constellation size. Sagitta contains 4 main stars in its asterism and has 19 Bayer Flamsteed designated stars within its confines. It is bordered by the constellations of Vulpecula, Hercules, Aquila and Delphinus. Sagitta is visible to all observers located at latitudes between +90° and ?70° and is best seen at culmination during the month of August.

In ancient history, the constellation of Sagitta was once known as Sham – a name applied today to its Alpha star. It was the Romans who named it Sagitta, the “Arrow”. In ancient Greek myth, it depicted the weapon which Hercules used to kill the eagle Aquila – or perhaps the Stymphalian birds. Perhaps it is Cupid’s Arrow, or the one which the Centaur shot at Chiron… No matter which tale you choose, it’s unmistakeable arrow shape was clear to all cultures, including the Persians, Hebrews, Greeks and Romans. Only Johann Bayer seemed to have trouble with it… For it is one of those constellation in which he named the bright stars out of order!

Let’s begin our binocular tour of Sagitta with Alpha – the “a” symbol on our chart. While Sham isn’t the brightest star in the constellation, this yellow bright giant star’s name really does mean “arrow”. Located about about 475 light years from Earth, it has a stellar luminosity 340 times that of the Sun and is about 20 times larger. Sham falls inside the “Hertzsprung Gap,” a perimeter of stellar temperature and luminosity that few stars fit inside. From its point in stellar evolution, it should have stopped fusing hydrogen to helium and began to brighten. However, that’s not the case. For some reason, Sham’s surface shows an abundance of nitrogen – a state which could only occur from interior helium fusion. A Cepheid variable star in the making? Perhaps!

Take a look at Beta in binoculars – the “B” symbol on our map. It’s G-type yellow star like our own Sun. Beta Sagittae is a giant star and, like Sham, is only about 467 light years away from our solar system. Delta, in the center of the arrow, is a spectroscopic binary star. It consists of a class M giant star and a quiet little hydrogen fusing dwarf star. Both are happy at a distance of about 448 light years from here and both happily separated from each other by a little less than 9 AU. Don’t forget red giant star, Gamma, either! The “Y” star on our chart might be 275 light years away, but it shines 640 times brighter than our Sun! It, too, is highly evolved…. Surrounded by a shell and well on its way to becoming a Mira-type variable star and eventually a white dwarf star about the size of the Earth.

For large binoculars and small telescopes, set your sights towards Messier 71 (RA 19 : 53.8 Dec +18 : 47). At around 8th magnitude, this loosely structured globular cluster is a challenge for smaller optics, but a wonderful study. It was originally discovered by Philippe Loys de Chéseaux in 1746 and included by Charles Messier in his Messier catalog of comet-like objects in 1780. Residing about 12,000 light years away and spanning about 27 light years across, there has long been a debate about this star cluster’s proper designation… globular cluster or concentrated galactic star cluster? Thanks to modern photometry, astronomers have detected a short “horizontal branch” in the H-R diagram of M71, which is characteristic of a globular cluster. Its low metallicity content has now been recognized as that of a “youthful” globular cluster and its lack of RR Lyrae variables places it at an age of between 9 and 10 billion years old.

For two challenging large telescope studies, let’s try your hand with planetary nebulae. The first is NGC 6879 (RA 20 : 10.5 Dec +16 : 55). At an apparent magnitude of 13, this challenging study will require high magnification and careful alignment to pick out from the stellar field. However, don’t be discouraged, because the nebula itself is rather bright and conspicuous as a “hairy star”. Just as challenging is NGC 6886 (RA 20 : 12.7 Dec +19 : 59). While the central star is a magnitude brighter at 12, you’re going to need at least an 8″ telescope to detect this one. It has an unusual chemical composition which an OIII filter helps to reveal.

Sources:
Wikipedia
Chandra Observatory
SEDS
Chart Courtesy of Your Sky.

January 7, 2009April 26, 2016 by Fraser Cain

International Year of Astronomy Opening Ceremonies

George Hrab performing at the IYA 2009 Opening Ceremonies

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Nothing works better than repetition. 2009 is the International Year of Astronomy! We’ve said it more than a few times before, and you’ll read a lot of coverage over the next year here on Universe Today. But last night we got to officially kick things off and celebrate the beginning of IYA 2009 events in the US.

Chorus to the 365 Days of Astronomy podcast intro

The IYA 2009 opening ceremonies started out with a mini-concert by George Hrab. In addition to playing this gig, George provided the intro music for IYA 2009 365 Days of Astronomy podcast. The podcast has the chorus, but George has a longer version which he performed last night. George led a sing-along, performing the lyrics and the 700ish people in the audience helped out with the chorus. George is a great performer, and an amazing guy. Check out his podcast at http://www.geologicpodcast.com/

The highlight of the evening for me was a live linkup between the Los Angeles party and party goers at the Cincinnati Observatory. The live video worked out great, and there was a real feeling of camaraderie between the two locations. The big plan was for the Cincinnati folks to broadcast a live image of the Pleiades star cluster, but they had cloudy skies – a picture taken a few days ago was used instead.

There was a simultaneous ribbon cutting ceremony in Second Life, on the IYA 2009 island. Unfortunately, the island totally filled up, and it was difficult to actually interact with the people there. As we were singing along with George in the real world, the avatars in
Second Life were singing along too.

The final treat of the evening was a special advance viewing of the new PBS documentary, 400 Years of the Telescope, with a voiceover by Neil deGrasse Tyson. This documentary won’t air until April 12, 2009, sadly, so there’s no place to watch it until then. The documentary starts with the invention of the telescope and then follows the major technological improvements that bring us to the modern observatories we have today; and a peek a the supertelescopes coming down the road.

As we were walking out, Celestron had set up a constellation of telescopes to check out the night sky. Of course, Los Angeles doesn’t have the clearest skies. The Moon was up and we could just barely make out the stars in Orion. So people walking out from the ceremonies could get a chance to look at objects in the sky with their own eyes. In the middle of these expensive telescopes was the prototype for the Galileo Scope (more on this in another post), so we got to take it out for a test drive. I really want one. You know… for the kids.

If you want to watch it for yourself, the Astronomy Cast media team recorded the entire opening ceremonies – except for the PBS documentary. I have no idea how long it will still be available, but check it out here.

January 7, 2009December 24, 2015 by Tammy Plotner

Reticulum

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Located south of the ecliptic plane, the small, faint constellation of Reticulum was first named Rhombus by astronomical clock creator – Isaac Habrecht. It was later renamed Reticulum by Nicolas Louis de Lacaille in 1763. It spans 114 square degrees of sky, ranking 82nd in constellation size, has 4 main stars in its primary asterism and contains 11 Bayer Flamsteed designated stars within its confines. Reticulum is bordered by the constellations of Horologium, Dorado and Hydrus. It is visible to all observers located at latitudes between +23° and ?90° and is best seen at culmination during the month of January.

Since Reticulum is a “new” constellation, there is no mythology associated with it – only the story of how its name came to be. Originally named Rhombus by Isaac Habrecht, it was a name the fit the star pattern, considering a rhombus is a basic diamond pattern. Habrecht and his brother were talented Germany clock makers and one of their specialities was in fashioning astronomical clocks. As a matter of fact, they built the second astronomical clock in Strasbourg between 1571 and 1574. It was designed by mathematician Christian Herlin, and as well as the Habrecht brothers, had astronomer and musician David Wolckenstein to assist. This fantasy clock had a staircase, huge amounts of artwork, musical embellishments, but was best known for its complexity as an astronomical device. It had a calendar dial, the astrolabe, the indicators for planets and eclipses… and a celestial globe. When Lacaille made his sojourn to the Cape of Good Hope, his intent wasn’t to usurp Habrecht’s place in astronomical history – but to unify astronomical catalogs. In an attempt to honor instruments of science and his telescope for which he used to chart the southern skies, Lacaille named this trapezoidal collection of stars Reticulum, the Latin derivative for the reticule crosshairs on his spyglass which enabled him to accurately pinpoint star positions. The name Reticulum stuck and was later adopted as one of the 88 modern constellations by the International Astronomical Union.

Let’s begin our binocular tour of Reticulum with its brightest star – Alpha – the “a” symbol on our chart. Alpha Reticuli is a yellow G class giant star which is about 163 light years away from Earth. It shines about 237 times brighter than our Sun and is about 21 times larger. It will eventually end its life quietly as a white dwarf star. But, take out your telescope and have a closer look! You’ll find out that Alpha is also a binary star with a very disparate 12th magnitude companion star nearby. While the star hasn’t moved in the last 150 years, the pair does display the same proper motion.

Keep binoculars handy and hop west for Zeti Reticuli. This binary star system located about 39 light years away from our own solar system. The pair of twin suns are very much like our own in temperature and mass – yellow dwarf stars – but it’s there the similarities end. At one time, astronomers believed the Zeta pairing to be old galactic halo Population II subdwarf stars, but recent research indicates the may belong to the younger galactic disk population. This makes the twin Zetas far older than our Sun – in the neighborhood of 8 billion years old. And they aren’t moving along alone! The pair belongs to the Zeta Herculis Moving Star Group. Both stars share similar proper motions and distances – and despite being so widely spaced, they are a true binary star with an orbital period of an estimated million years!

While viewing Zeta, keep in mind all the legends behind this particular pair. In 1961, alien abductees – Barney and Betty Hill – were “taken” by citizens who imparted information to Betty that their home star was the Zeta system. After a map was constructed by an amateur astronomer and eventually debunked by Carl Sagan, then later sensationalized by Bob Lazar, the Zeta “planet” theory eventually went into hibernation for fear of media attention. On September 20, 1996 a tentative discovery of a “hot Jupiter” in the Zeta system was discovered and quickly retracted as being “pulsations” from the star… and while conditions are possible for Earth-like planets to exists around these twins suns, low solar metallicity makes their presence unlikely.

Before you give up planetary hopes, hop to Epsilon Reticuli – the backwards “3” symbol on our map. Now here’s a binary system located approximately 59 light-years away that really does have a confirmed planet! The primary star is an orange subgiant star, while the secondary star is a white dwarf star. As of 2000, an extrasolar planet has been confirmed to be orbiting the primary star in the system! It is roughly the size of Jupiter and it orbits around the star every 418 days. What’s more, there could possibly be an Earth-like trojan accompanying it!

For binoculars, keep a watch on R Reticuli – a Mira-type variable star. While it takes 278.3 days for it to go through it’s changes, they are very dramatic. You’ll find this incredible star begins by shining at respectable magnitude of 6.5 only to virtually turn telescopic at magnitude 14 during its minima. Now that’s variable!

For a small telescope and big binocular challenge, try your hand at NGC 1313 (RA 3 : 18.3 Dec -66 : 30). At magnitude 9 and more than 8 arc minutes in size, this starburst galaxy is often referred to as the “Topsy Turvy” because of its unusual supershell spiral galaxy structure. Located about 15 million light years away, large telescopes will pick out strange features, like spiral arms which are lopsided and its rotational axis is not at the center of the nuclear bar.

Now, have a go at NGC 1559 (RA 4 : 17.6 Dec -62 : 47). Although this barred spiral galaxy is over a magnitude fainter and about half the size of the last, you’ll still find it quite bright and rich in the telescope. Although it was originally thought to be a member of the Dorado Galaxy Group, this Seyfert Galaxy is all alone in space. NGC 1559 has massive spiral arms and strong star formation. It contains a small bar which is oriented nearly east-west and spans 40?. Its bar and galactic disc are the source of very strong radio emissions!

Our last galaxy is NGC 1543 (RA 4 : 12.8 Dec -57 : 44). Also about magnitude 10.5 and about 4 arc minutes in size, Dunlop 100 really is considered part of the Dorado Galaxy Group. Look for a very bright nucleus in this spiral galaxy, with a faint east to west extension!

Chart Courtesy of Your Sky.

January 7, 2009December 24, 2015 by Nancy Atkinson

Blogger Meet-Up Jan. 7 in Long Beach

The January AAS meeting is being held in Long Beach, CA (Image by Kevin Stanchfield)

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If you live near Long Beach or are there for the American Astronomical Society meeting, meet Fraser, Ian and the Astronomy Cast LIVE team at a “Blogger Meet-up” on Wed. January 7 at the Rock Bottom Brewery from 6pm – 9pm. The team hopes you can make it! (Have a tall cold one for me, OK?!)

And here’s the schedule for today’s press conferences, which will be streamed LIVE at Astronomy Cast LIVE’s UStream Channel: (all times Pacific Standard Time)

9:30 am: Black Holes
11:00 am: Ballistic Stellar Interlopers
12:30 pm: Extragalactic Background

Check it out!

January 6, 2009December 24, 2015 by Nancy Atkinson

With No Smoke or Mirrors, Spacecraft Hunts for Active Galaxies with Central Black Holes

Swift's Hard X-ray Survey offers the first unbiased census of active galactic nuclei in decades. Dense clouds of dust and gas, illustrated here, can obscure less energetic radiation from an active galaxy's central black hole. High-energy X-rays, however, easily pass through. Credit: ESA/NASA/AVO/Paolo Padovani

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NASA’s Swift spacecraft is designed to hunt for gamma-ray bursts. But in the time between these almost-daily cosmic explosions, Swift’s Burst Alert Telescope (BAT) scans the sky, performing an ongoing X-ray survey. Some of the first results of that survey were shared at the American Astronomical Society meeting in Long Beach, California. The BAT is revealing differences between nearby active galaxies and those located about halfway across the universe. Understanding these differences will help clarify the relationship between a galaxy and its central black hole. But unlike most telescopes, the BAT observations are not done with mirrors, optics or direct focusing. Instead, images are made by analyzing the shadows cast by 52,000 randomly placed lead tiles on 32,000 hard X-ray detectors. And BAT is becoming a workhorse: The survey is now the largest and most sensitive census of the high-energy X-ray sky.

“There’s a lot we don’t know about the workings of supermassive black holes,” says Richard Mushotzky of NASA’s Goddard Space Flight Center in Greenbelt, Md. Astronomers think the intense emission from the centers, or nuclei, of active galaxies arises near a central black hole containing more than a million times the sun’s mass. “Some of these feeding black holes are the most luminous objects in the universe. Yet we don’t know why the massive black hole in our own galaxy and similar objects are so dim.”

“The BAT sees about half of the entire sky every day,” Mushotzky said. “Now we have cumulative exposures for most of the sky that exceed 10 weeks.”

Galaxies that are actively forming stars have a distinctly bluish color (“new and blue”), while those not doing so appear quite red (“red and dead”). Nearly a decade ago, surveys with NASA’s Chandra X-Ray Observatory and ESA’s XMM-Newton showed that active galaxies some 7 billion light-years away were mostly massive “red and dead” galaxies in normal environments.

The BAT survey looks much closer to home, within about 600 million light-years. There, the colors of active galaxies fall midway between blue and red. Most are spiral and irregular galaxies of normal mass, and more than 30 percent are colliding. “This is roughly in line with theories that mergers shake up a galaxy and ‘feed the beast’ by allowing fresh gas to fall toward the black hole,” Mushotzky says.

Until the BAT survey, astronomers could never be sure they were seeing most of the active galactic nuclei. An active galaxy’s core is often obscured by thick clouds of dust and gas that block ultraviolet, optical and low-energy (“soft”) X-ray light. Dust near the central black hole may be visible in the infrared, but so are the galaxy’s star-formation regions. And seeing the black hole’s radiation through dust it has heated gives us a view that is one step removed from the central engine. “We’re often looking through a lot of junk,” Mushotzky says.

But “hard” X-rays — those with energies between 14,000 and 195,000 electron volts — can penetrate the galactic junk and allow a clear view. Dental X-rays work in this energy range.

Astronomers think that all big galaxies have a massive central black hole, but less than 10 percent of these are active today. Active galaxies are thought to be responsible for about 20 percent of all energy radiated over the life of the universe, and are thought to have had a strong influence on the way structure evolved in the cosmos.

The Swift spacecraft was launched in 2004.

Source: NASA

January 6, 2009December 24, 2015 by Ian O'Neill

AAS Session 328: Black Holes I, January 6th

The debate of whether or not a supermassive black hole (SMBH) was kicked out of the centre of a galaxy continues in the Black Holes I session at the A A S. According to Stefanie Komossa and her team at the Max Plank Institute for extraterrestrial Physics (MPE) back in May 2008, spectroscopic data of a galactic core appeared to show a collision event between two SMBHs. In this case, the smaller SMBH was propelled out of its host galaxy by an intense and focused “superkick” by gravitational waves.

However, the delegates attending Session 328 have other ideas…

Tamara Bogdanovic, University of Maryland, kicked off the Black Hole I Session with an investigation into the spectroscopic data derived by Komossa et al. Bogdanovic presented her research on the possibility that rather than showing a superkick, the data could be showing the motion of binary SMBHs around the galactic core after a galactic merger. She made the rather sobering statement that there were, “more publications than data,” highlighting the fact that far from being conclusive evidence of a superkick, that more subtle mechanisms may be at work. Model data of orbiting binaries appear to fit the same spectroscopic analysis just as well as the superkick situation. As binary SMBHs would be long-lived objects, there’s a good (statistical) chance of observing them. Further work is required, however, possibly using the Very Long Baseline Array (VLBA).

Dipanker Maitra, of the University of Amsterdam, then presented his results of time-dependent modelling of Sagittarius A* (the SBH at the centre of our galaxy). It turns out that there are more high energy flare events detected from Sag A* than expected from the predicted accretion rate. Maitra models the time lag observed in radio data between the first high-energy flares and the following low energy flares.

Jen Blum, from the University of Maryland, then took on the emissions from a stellar black hole in the X-ray binary GRS 1915+105. Key to Blum’s research is to investigate the strange asymmetric iron emission line. It looks like this asymmetry can be explained by a combination of special relativity and general relativity effects near the space-time warping black hole.

David Garofalo, who works at JPL/Caltech, then followed quickly with his research of the “central engine” inside galactic nuclei, investigating how strong a SMBH’s magnetic field can be. In his models, he finds the spin of the black hole is key to magnetic field strength. Counter-intuitively, Garofalo’s work suggests that the fastest spinning black holes may have the weakest magnetic field. Also, slowly spinning SMBHs appear to have a larger gap region. He is quick to point out that his model only shows us what configurations are possible, but concludes with the suggestion that you don’t need a fast-spinning SMBH for powerful jets to be generated. “[It’s a] tug-o-war between gravity and the Lorentz forces,” he said when referring to his model, “but other [unaccounted for] physics may significantly modify the model.”

Avery Broderick, from the Canadian Institute for Theoretical Astrophysics, examines jets produced by the Milky Way’s SMBH and M87. Both are fantastic objects to study as they are relatively close. However, the angular resolution of instrumentation needs to be boosted, or new techniques are needed to understand jet mechanisms.

Massimo Dotti, from the University of Michigan, re-explored Komossa’s research, also supporting Tamara Bogdanovic’s work that a superkick may not have caused the emissions studied by Komossa. He also shows that a galactic merger and then SMBH binary can generate similar red-shifted and blue-shifted components of emission profiles. Dotti then showed details of his model and proposed some observational constrains.

Bonus speaker and NASA scientist Teddy Cheung then discussed his search for “offset galactic nuclei” that may be evidence for SMBH collisions in the centre of galaxies. According to Cheung, the calculations to find the black hole masses can be “done on the back of an envelope… the flap of the envelope!” He then showed some results of the observation campaign, pointing to a few candidates that might reveal a SMBH binary partner may have achieved escape velocity (i.e. been kicked out of the galaxy), but he emphasised that this number was small. Radio data of pre-merger and post-merger lobes were also presented, helping future studies characterize collision and merger events.

All in all, Session 328 was a superb start to the conference for me, really opening my eyes to the cutting edge supermassive black hole research going on around the world. There’s a lot more where that came from…

Article source: AAS meeting.

January 6, 2009December 24, 2015 by Fraser Cain

Podcast: How Old is the Universe?

Anisotropy — WMAP image of the Cosmic Microwave Background Radiation

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We did a wildly popular three part series about the center, size and shape of the Universe. But every good trilogy needs a 4th episode. This week we look at age of the Universe. How old is the Universe, and how do we know? And how has this number changed over time as astronomers have gotten better tools and techniques?

Click here to download the episode.

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

How Old is the Universe? – Transcript and show notes.

January 6, 2009December 24, 2015 by Fraser Cain

If Brown Isn’t a Color, What Color are Brown Dwarfs?

Artist's impression of a brown dwarf. Image credit: NASA/JPL

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We’ve talked about brown dwarfs here on Universe Today for years and years. These are the “failed stars”; objects with too little mass to fully ignite nuclear fusion in their cores. Instead of blazing with red, yellow or the white light of our own stars, they’re heated by the gravitational collapse of material. They’re called brown dwarfs, but you might be surprised to know that they aren’t actually brown. In fact, it’s impossible to have brown light. So what color are they?

The term “brown dwarf” was originally coined by Jill Tarter in 1975 to describe these objects, and there were other suggestions for names, like planetar and substar. But the name “brown dwarf” stuck. And here’s the problem, as described by Jill Tarter, “it was obvious that we needed a color to describe these dwarfs that was between red and black. I proposed brown and Joe (Silk) objected that brown was not a color.”

Brown isn’t a color?!

Not for astronomers. When they consider the color of a star, astronomers are talking about the wavelength of the light being emitted. Stars emit light at various wavelengths, and whatever photons are mostly being emitted are what we see. Yellow stars emit primarily yellow photons, red stars emit mostly red photons, etc. But you can’t have a star emit brown photons because the “color” brown is a de-saturated yellow. Brown dwarfs can’t be brown because it’s impossible to emit brown light. So what color are they?

Dr. Kenneth Brecher is a professor at Boston University and the primary investigator for Project LITE. This is a research project that uses a variety of experiments to understand how people see color. I highly recommend you check out the Project LITE website and take a look at the Flash experiments they have available. You’ve probably seen some of these optical illusions in the past, where spinning wheels of black-and-white can actually create different colors in our brains. Brecher demonstrated one of these color wheels for me – it’s a CD that can spin like a top. At rest, you see black-and-white, and then spin up the disk and you can see red, green and blue. Very cool stuff (totally unconnected from the color of brown dwarfs).

Brecher did a presentation at the American Astronomical Society Meeting about the actual color of brown dwarfs. He even had a flashlight that shines a light the color of brown dwarfs. Unfortunately, I didn’t catch a photo of it, but check out Nature’s blog, they got one. It’s sort of a dull orange color. But here’s the cool part. There’s no way to actually see the color of a brown dwarf unless you’re having the photons strike your eyeballs.

All you color theory folks might want to know the hexidecimal code: EB4B25. And here are the RGB values: R-235, G-75, B-37

So what color would an isolated brown dwarf look like? Dr. Brecher had a slide in his presentation that shows the color – we’ve extracted it and made it bigger. I think it looks kind of reddish orange, but then color is in the eye of the beholder.

January 6, 2009December 24, 2015 by Nancy Atkinson

“Lighthouse” Analogy No Longer Works for Pulsars

NASA's Fermi Gamma-ray Space Telescope has found 12 previously unknown pulsars (orange). Fermi also detected gamma-ray emissions from known radio pulsars (magenta, cyan) and from known or suspected gamma-ray pulsars identified by NASA's now-defunct Compton Gamma-Ray Observatory (green). Credit: NASA/Fermi/LAT Collaboration

NASA’s Fermi Gamma-ray Space Telescope has found 12 previously unknown gamma-ray only pulsars, as well as identifying gamma-ray emissions from 18 known or suspected radio pulsars. And what the telescope is finding is changing the way we think of these stellar cinders. The old analogy for pulsars was a lighthouse: gamma-rays were thought to pulse out in a narrow beam from the neutron star’s magnetic poles. But this new research shows that cannot be the case. A new class of gamma-ray-only pulsars shows that the gamma rays must form in a broader region than the lighthouse-like radio beam. “We used to think the gamma rays emerged near the neutron star’s surface from the polar cap, where the radio beams form,” says Alice Harding of NASA’s Goddard Space Flight Center. “The new gamma-ray-only pulsars put that idea to rest.” She and Roger Romani from Stanford University in California spoke today at the American Astronomical Society meeting.

A pulsar is a rapidly spinning and highly magnetized neutron star, the crushed core left behind when a massive sun explodes. Most were found through their pulses at radio wavelengths, and were thought to be caused by narrow, lighthouse-like beams emanating from the star’s magnetic poles.

If the magnetic poles and the star’s spin axis don’t align exactly, the spinning pulsar sweeps the beams across the sky. Radio telescopes on Earth detect a signal if one of those beams happens to swing our way. Unfortunately, any census of pulsars is automatically biased because we only see those whose beams sweep past Earth.

“That has colored our understanding of neutron stars for 40 years,” Romani says. The radio beams are easy to detect, but they represent only a few parts per million of a pulsar’s total power. Its gamma rays, on the other hand, account for 10 percent or more. “For the first time, Fermi is giving us an independent look at what heavy stars do,” he adds.

Watch an animation of the new look at these pulsars.

Pulsars are phenomenal cosmic dynamos. Through processes not fully understood, a pulsar’s intense electric and magnetic fields and rapid spin accelerate particles to speeds near that of light. Gamma rays let astronomers glimpse the particle accelerator’s heart.

Astronomers now believe the pulsed gamma rays arise far above the neutron star. Particles produce gamma rays as they accelerate along arcs of open magnetic field. For the Vela pulsar, the brightest persistent gamma-ray source in the sky, the emission region is thought to lie about 300 miles from the star, which is only 20 miles across.

Existing models place the gamma-ray emission along the boundary between open and closed magnetic field lines. One version starts at high altitudes; the other implies emission from the star’s surface all the way out. “So far, Fermi observations to date cannot distinguish which of these models is correct,” Harding says.

Because rotation powers their emissions, isolated pulsars slow as they age. The 10,000-year-old CTA 1 pulsar, which the Fermi team announced in October, slows by about a second every 87,000 years.

Fermi also picked up pulsed gamma rays from seven millisecond pulsars, so called because they spin between 100 and 1,000 times a second. Far older than pulsars like Vela and CTA 1, these seemingly paradoxical objects get to break the rules by residing in binary systems containing a normal star. Stellar matter accreted from the companion can spin up the pulsar until its surface moves at an appreciable fraction of light speed.

“We know of 1,800 pulsars, but until Fermi we saw only little wisps of energy from all but a handful of them,” said Romani. “Now, for dozens of pulsars, we’re seeing the actual power of these machines.”

Source: NASA