Ever seen the arc of the Milky Way in daylight? Astrophotographer Miguel Claro came as close as possible by capturing this view of ‘Via Lactea’ at dawn on May 11, 2013, with the stars of Saggitarius and Scorpius clearly visible, while the sky is slowly turning blue. The image was taken with a rocky region of the resort area of Portinho da Arrábida, in Portugal, visible in the foreground. Also visible is the Red Supergiant star Antares.
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Some cultures used to say the Earth was the center of the Universe. But in a series of “great demotions,” as astronomer Carl Sagan put it in his book Pale Blue Dot, we found out that we are quite far from the center of anything. The Sun holds the prominent center position in the center of the Solar System, but our star is just average-sized, located in a pedestrian starry suburb — a smaller galactic arm, far from the center of the Milky Way Galaxy.
But perhaps our suburb isn’t as quiet or lowly as we thought. A new model examining the Milky Way’s structure says our “Local Arm” of stars is more prominent than we believed.
“We’ve found there is not a lot of difference between our Local Arm and the other prominent arms of the Milky Way, which is in contrast what astronomers thought before,” said researcher Alberto Sanna, of the Max-Planck Institute for Radio Astronomy, speaking today at the American Astronomical Society’s annual meeting in Indianapolis, Indiana.
Sanna said that one of the main questions in astronomy is how the Milky Way would appear to an observer outside our galaxy.
If you imagine the Milky Way as a rippled cookie, our star is in a neighborhood in between two big ripples (the Sagittarius Arm and the Perseus Arm). Before, we thought the Local Arm (or Orion Arm) was just a small spur between the arms. New research using trigonometric parallax measurements, however, suggests the Local Arm could be a “significant branch” of one of those two arms.
In a few words, our stellar neighborhood is a bigger and brighter one than we thought it was.
As part of the BeSSeL Survey (Bar and Spiral Structure Legacy Survey) using the Very Long Baseline Array (VLBA), astronomers are able to make more precise measurements of cosmic distances. The VLBA uses a network of 10 telescopes that work together to figure out how far away stars and other objects are.
It’s hard to figure out the distance from the Earth to other stars. Generally, astronomers use a technique called parallax, which measures how much a star moves when we look at it from the Earth.
When our planet is at opposite sites of its orbit — in spring and fall, for example — the apparent location of stellar objects changes slightly.
The more precisely we can measure this change, the better a sense we have of a star’s distance.
The VLBA undertook a search for spots in our galaxy where water and methanol molecules (also known as masers) enhance radio waves — similar to how lasers strengthen light waves. Masers are like stellar lighthouses for radio telescopes, the National Radio Astronomy Observatory stated.
Between 2008 and 2012, the VLBA tracked the distances to (and movements of) several masers to higher precision than previously, leading to the new findings.
Will the findings help ease our “inferiority complex” after all those great demotions?
“I would say yes, that’s a nice conclusion to say we are more important,” Sanna told Universe Today. “But more importantly, we are now mapping the Milky Way and discovering how the Milky Might appear to an outside observer. We now know the Local Arm arm is something that an observer from afar would definitely notice!”
Admittedly, I’m partial to Randy Halverson’s night sky photography from South Dakota. Having grown up in neighboring North Dakota myself, Halverson’s images bring back memories of the dark skies that grace the northern plains. But this one is just stunning, not to mention my early childhood home was surrounded by cottonwood trees — towering giants with ample limbs, and one of the few trees that grew well in the harsh prairies of the Dakotas.
Randy said he was trying out some new gear with this image, which is a frame from a timelapse he is shooting (can’t wait!) He used ased a Canon 6D and a Rokinon 24mm F1.4 lens (set at F2), using Emotimo TB3 Black timelapse equipment, shot at ISO 3200 for 20 seconds.
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This beautiful new timelapse video might have folks heading in droves for northern Michigan. Shawn Malone of Lake Superior Photo put together this incredible video — her first attempt at a timelapse compilation, believe it or not — using over 10,000 photo frames showing 33 different scenes of various night sky events from northern Michigan over the past year. “It took a year to shoot and a bit of tenacity and persistence to get this into a form of coherent electrified cosmic goodness,” Malone wrote on Vimeo. And did she ever capture cosmic goodness: auroras, the Milky Way rising and setting, meteor showers, a comet, and even aurora and lightning together in one scene. Just gorgeous….
Have you ever dreamed of camping out under the dark skies of Death Valley? Dream no more: you can enjoy this virtual experience thanks to Gavin Heffernan and his Sunchaser Pictures crew. This magnificent new timelapse video includes some insane star trails, the beautiful Milky Way, and an incredible pink desert aurora!
“As you can see, Death Valley is a crazy place to shoot at,” Gavin said via email to Universe Today, “as the horizon is so strangely uneven/malleable. I don’t know if the valley was cut by water or underground magma, but it’s almost impossible to find a straight horizon.” See some great images from their video, below:
Gavin said he and his team tried out some new timelapse techniques, like moonpainting the foreground landscapes (0:53 — 1:20), and also some experiments merging regular timelapse footage with star trails — “a technique we’ve been calling Starscaping (1:07:1:33)” he said. “If it has an actual name, let us know! Star Trails shot at 25 sec exposures. No special effects used, just the natural rotation of the earth’s axis. Photography Merging: STARSTAX. Used two Canon EOS 5Dmkii, with a 24mm/1.4 lens & 28mm/1.8.”
Obtaining an accurate distance between the Sun and the center of our Galaxy remains one of the principal challenges facing astronomers. The ongoing lively debate concerning this distance hinges partly on the nature of dust found along that sight-line. Specifically, are dust particles lying toward the Galactic center different from their counterparts near the Sun? A new study led by David Nataf asserts that, yes, dust located towards the Galactic center is anomalous. They also look at accurately defining both the distance to the Galactic center and the reputed bar structure that encompasses it.
The team argues that characterizing the nature of small dust particles is key to establishing the correct distance to the Galactic center, and such an analysis may mitigate the scatter among published estimates for that distance (shown in the figure below). Nataf et al. 2013 conclude that dust along the sight-line to the Galactic center is anomalous, thus causing a non-standard ‘extinction law‘.
The extinction law describes how dust causes objects to appear fainter as a function of the emitted wavelength of light, and hence relays important information pertaining to the dust properties.
The team notes that, “We estimate a distance to the Galactic center of [26745 light-years] … [adopting a] non-standard [extinction law] thus relieves a major bottleneck in Galactic bulge studies.”
Nataf et al. 2013 likewise notes that, “The variations in both the extinction and the extinction law made it difficult to reliably trace the spatial structure of the [Galactic] bulge.” Thus variations in the extinction law (tied directly to the dust properties) also affect efforts to delineate the Galactic bar, in addition to certain determinations of the distance to the Galactic center. Variations in the extinction law imply inhomogeneities among the dust particles.
“The viewing angle between the bulge’s major axis and the Sun-Galactic centerline of sight remains undetermined, with best values ranging from from 13 to … 44 [degrees],” said Nataf et al. 2013 (see also Table 1 in Vanhollebekke et al. 2009). The team added that, “We measure an upper bound on the tilt of 40 [degrees] between the bulge’s major axis and the Sun-Galactic center line of sight.”
However, the properties of dust found towards the Galactic center are debated, and a spectrum of opinions exist. While Nataf et al. 2013 find that the extinction law is anomalously low, there are studies arguing for a standard extinction law. Incidentally, Nataf et al. 2013 highlight that the extinction law characterizing dust near the Galactic center is similar to that tied to extragalactic supernovae (SNe), “The … [extinction] law toward the inner Galaxy [is] approximately consistent with extra-galactic investigations of the hosts of type Ia SNe.”
Deviations from the standard extinction law, and the importance of characterizing that offset, is also exemplified by studies of the Carina spiral arm. Optical surveys reveal that a prominent spiral arm runs through Carina (although that topic is likewise debated), and recent studies argue that the extinction law for Carina is higher than the standard value (Carraro et al. 2013, Vargas Alvarez et al. 2013). Conversely, Nataf et al. 2013 advocate that dust towards the Galactic center is lower by comparison to the standard (average) extinction law value.
The impact of adopting an anomalously high extinction law for objects located in Carina is conveyed by the case of the famed star cluster Westerlund 2, which is reputed to host some of the Galaxy’s most massive stars. Adopting an anomalous extinction law for Westerlund 2 (Carraro et al. 2013, Vargas Alvarez et al. 2013) forces certain prior distance estimates to decrease by some 50% (however see Dame 2007). That merely emphasizes the sheer importance of characterizing local dust properties when establishing the cosmic distance scale.
In sum, characterizing the properties of small dust particles is important when ascertaining such fundamental quantities like the distance to the Galactic center, delineating the Galactic bar, and employing distance indicators like Type Ia SNe.
With the arrival of spring, the Milky Way begins its rise in the sky in the northern hemisphere. Now visible at dawn in the skies over Portugal at dawn, astrophotographer Miguel Claro captured this stunning 21-image mosaic showing the arch of the Milky Way framing the setting Moon from Monsaraz, Portugal in the Alqueva Dark Sky Reserve. In the foreground is the Convent of Orada (dated 1670).
“Near the center at the right of palm trees, the moon shines brightly, although not interfering with the giant arc of the Milky Way where it is possible to distinguish a lot of constellations like Ursa Minor, with the Polaris star to the left of the image,” Claro said via email, “until the swan (Cygnus), with its North America nebula (NGC7000) clearly visible, down to the right, we still find the constellation of Sagittarius and Scorpio, with the brilliant super giant star, Antares.”
Click the images to see larger versions (yes, you really want to ’embiggen!’)
See an annotated version below. Claro used a Canon 60Da – ISO1600 Lens 24mm f/2; Exp. 15 seconds, taken on 06/04/2013 at 5:32 AM local time.
I’m going to refrain from the initial response that comes to mind… actually, no I won’t — they’re really, really, really big!!!!
</Kermit arms>
Ok, now that that’s out of the way check out this graphic by Arecibo astrophysicist Rhys Taylor, which neatly illustrates the relative sizes of 25 selected galaxies using images made from NASA and ESA observation missions… including a rendering of our own surprisingly mundane Milky Way at the center for comparison. (Warning: this chart may adversely affect any feelings of bigness you may have once held dear.) According to Taylor on his personal blog, Physicists of the Caribbean (because he works had worked at the Arecibo Observatory in Puerto Rico) “Type in ‘asteroid sizes’ into Google and you’ll quickly find a bunch of images comparing various asteroids, putting them all next to each at the same scale. The same goes for planets and stars. Yet the results for galaxies are useless. Not only do you not get any size comparisons, but scroll down even just a page and you get images of smartphones, for crying out loud.” So to remedy that marked dearth of galactic comparisons, Taylor made his own. Which, if you share my personal aesthetics, you’ll agree is quite nicely done.
“I tried to get a nice selection of well-known, interesting objects,” Taylor explains. “I was also a little limited in that I needed high-resolution images which completely mapped the full extent of each object… still, I think the final selection has a decent mix, and I reckon it was a productive use of a Saturday.” And even with the dramatic comparisons above, Taylor wasn’t able to accurately portray to scale one of the biggest — if not the biggest — galaxies in the observable universe: IC 1101.
For an idea of how we measure up to that behemoth, he made this graphic:
That big bright blur in the center? That’s IC 1101, the largest known galaxy — in this instance created by scaling up an image of M87, another supersized elliptical galaxy that just happens to be considerably closer to our own (and thus has had clearer images taken of it.) But the size is right — IC 1101 is gargantuan.
At an estimated 5.5 million light-years wide, over 50 Milky Ways could fit across it! And considering it takes our Solar System about 225 million years to complete a single revolution around the Milky Way… well… yeah. Galaxies are big. Really, really, really, really big!
</Kermit arms>
Now if you’ll pardon me, I need to go stop my head from spinning… Read this and more on Rhys Taylor’s blog here, and add Rhys to your awesome astronomy Google+ circles here. And you can find out more about IC 1101 in the video below from Tony Darnell, aka DeepAstronomy:
There are some moments in an astrophotographer’s life that you just have to step back and say thanks for the view. “Thanks clear sky,” said Zhang Hong when he posted this image on Google+.
This almost looks like a shower of stars raining down. Just gorgeous.
Here are the specs on his equipment: Nikon D800, Aperture: f/2.8, Focal length: 14.mm, exposure time:25.9 seconds, ISO-4000, -0.7 exposure compensation, spot metering, no flash, equatorial mount.
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Back by popular demand… the Weekly Space Hangout has returned. This is a weekly broadcast on Google+, where I’m joined by a wide and varied team of space and astronomy journalists to discuss the big breaking stories this week.
We record the Weekly Space Hangout every Friday on Google+ at 12:00 pm PST / 3:00 pm EST / 2000 GMT. You’ll want to circle Cosmoquest on Google+ to find out when we’re recording next. The audio for the Weekly Space Hangout is also released to the Astronomy Castpodcast feed.