[Maggie's blog] Come Together

If you’re at all a fan of astronomy, you’ve probably marveled over the many beautiful photos of spiral galaxies that are out there. Like this one of NGC 3344 captured by the Hubble Space Telescope.

Credit: ESA/Hubble & NASA

But you may not know that galaxies have not always looked this way. The grand spirals we are so familiar with were formed over the course of billions of years by the collisions of smaller galaxies. Though, when spirals collide with a similar-sized galaxy, the disruption can cause them to merge and evolve into a giant elliptical galaxy. According to an article in Nature News, based on a survey of galaxy shape and structure (current to 2009), it is thought that “nearly all massive galaxies have undergone at least one major merger since the Universe was 6 billion years old.”

Giant elliptical galaxy, M87, located in the Virgo cluster

When we look at very distant galaxies, we see a completely different picture. Older galaxies tend to be small and clumpy, often with a lot of star formation occurring in the massive clumps. The question of how these clumpy galaxies evolve and develop structure over time is a big open question in astronomy, and we hope that the powerful up-and-coming James Webb Space Telescope will help astronomers to learn more.

Clumpy galaxy spied by the Hubble

Clumpy galaxies spied by the Hubble

Read more »

[Sara's blog] Awww! Cosmic baby pictures!

Protostars in Messier 78, as seen by multiple observatories
Credit: NASA/ESA/ESO/JPL-Caltech/Max-Planck

The side-by-side images above depict protostars found in Messier 78, a reflection nebula found within the constellation Orion (but not the Orion Nebula, which is Messier 42). These are some of the youngest stars that astronomers have ever seen – some of them are still embedded deeply in a gaseous envelope, which would suggest that they’re under 25,000 years old. That may seem like a long time compared to our human lives… but for stars that can live for millions or billions of years, it’s still stellar infancy. These images accompanied this press release from the Herschel space observatory, and represent observations from Herschel as well as ground-based telescopes. Though they can be difficult to detect, researchers are hoping to document more young stars in various stages of life – from before birth through infancy – to learn more about the early development of stars.

NASA often looks at “young” astronomical objects, to learn more about the formation and evolution of the Universe. Here’s a selection of some beautiful and interesting cosmic baby pictures…
Read more »

[Maggie's blog] Andromeda in the Infrared

Check out this gorgeous new image of the Andromeda Galaxy taken by the European Space Agency’s Herschel space observatory in the far-infrared. This new view shows cool lanes of forming stars in fine detail.

Credit: ESA

The news release says,

Sensitive to the far-infrared light from cool dust mixed in with gas, Herschel seeks out clouds of gas where stars are born. The new image reveals some of the very coldest dust in the galaxy – only a few tens of degrees above absolute zero – colored red in this image.

By comparison, warmer regions such as the densely populated central bulge, home to older stars, take on a blue appearance.

Intricate structure is present throughout the 200 000 light-year-wide galaxy with star-formation zones organized in spiral arms and at least five concentric rings, interspersed with dark gaps where star formation is absent.

Host to several hundred billion stars, this new image of Andromeda clearly shows that many more stars will soon spark into existence.

Read more »

[Maggie's blog] Teaming Up with Hubble to Create Beauty

Capturing the beauty of this galaxy took a team of people – and to understand the galaxy takes a team of missions.

This gorgeous image of galaxy M106 was created by renowned astro-photographer Robert Gendler, who retrieved archival Hubble images to assemble a mosaic of the center of the galaxy. He then used his own and fellow astro-photographer Jay GaBany’s observations to fill in areas where there was little or no Hubble data.

Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), and R. Gendler (for the Hubble Heritage Team) Acknowledgment: J. GaBany

The NASA feature written about this image tells us that Hubble data from the Advanced Camera for Surveys, Wide Field Camera 3, and Wide Field Planetary Camera 2 detectors were used for the center of the galaxy. The outer spiral arms are also Hubble data, but colorized with ground-based data taken by Gendler’s and GaBany’s 12.5-inch and 20-inch telescopes, which was captured at dark, remote sites in New Mexico.

Also visible are the optical component of the so-called “anomalous arms” of M106, which in this image are a red color, from glowing hydrogen emission. They’re called “anomalous” because they don’t line up very well with the galaxy’s more prominent spiral arms.

Why is this hydrogen gas glowing?
Read more »

[Maggie's blog] A Grand Spiral

The ultraviolet GALEX satellite just revealed the largest known spiral galaxy! NGC 6872 (a barred spiral) is 522,000 light-years across from the tip of one outstretched arm to the tip of the other, which makes it about 5 times the size of our home galaxy, the Milky Way! We recently covered this story on our Facebook but we wanted to go a little more in-depth. So, here is an interview with one of the people involved with this discovery, grad student Rafael Eufrasio.

This composite of the giant barred spiral galaxy NGC 6872 combines visible light images from the European Southern Observatory’s Very Large Telescope with far-ultraviolet (1,528 angstroms) data from NASA’s GALEX and 3.6-micron infrared data acquired by NASA’s Spitzer Space Telescope. A previously unsuspected tidal dwarf galaxy candidate (circled) appears only in the ultraviolet, indicating the presence of many hot young stars. IC 4970, the small disk galaxy interacting with NGC 6872, is located above the spiral’s central region. Images of lower resolution from the Digital Sky Survey were used to fill in marginal areas not covered by the other data. Credit: NASA’s Goddard Space Flight Center/ESO/JPL-Caltech/DSS

Blueshift: What is your current role at Goddard? What research are you working on?

Rafel: I am a research assistant at Goddard, but I am also a PhD candidate at the Catholic University in DC. I am a 5th year PhD student and [have been] working at Goddard since I started it in 2008. If everything goes as planned, I am defending my thesis next year.

I am working on the Spectral Energy Distribution (SED) of nearby face-on spiral galaxies. For my research I use as much data as I can possibly gather for these galaxies, from the ultraviolet (UV) to the radio (i.e. UV, optical, IR, sub-millimeter, and radio), from space and ground-based telescopes. My goal is to describe the content of stars, gas, and dust of these galaxies based on the information from the SEDs, as well as their Star Formation History (SFH).

Blueshift: We read the news feature on the GALEX discovery of NGC 6872, which is currently the largest known spiral galaxy, more than five times the size of the Milky Way. Can you tell us more about the object and how this discovery came about? Did you stumble on this discovery or did you specifically use GALEX to study this object in more detail?

Rafael: I was introduced to this galaxy almost a year and a half ago by Dr. Duilia de Mello, a professor at the Catholic University who also works at Goddard. She was studying young stellar systems outside of galaxies, specially the ones with strong UV emission, that she likes to call “blue blobs”. She knew I was working on the SED of spiral galaxies and we started this project. Initially, [we] chose 16 large regions (10 kiloparsecs or kpc in diameter) all over the galaxy, [which] produced UV-to-IR [light] and we presented preliminary results at the American Astronomical Society (AAS) meeting in January of 2012.

However something seemed off when I checked the sizes of the regions, stellar masses, and star formation rates. These 10 kpc regions would encompass a large chunk of most spiral galaxies I am studying, but they looked small when superposed in NGC 6872.

Then we spent a year asking astronomers in different places and searching catalogs to finally claim that it is the largest-known spiral galaxy at the AAS meeting this January. With an extended disk of at least 160 kpc in diameter.

Blueshift: Why is this galaxy so much bigger than the Milky Way – and do you think this is an uncommon size for a galaxy, or have we just not discovered others like this yet? Once upon a time, we didn’t think exoplanets were common and now we know differently, for example.

Read more »

[Sara's blog] American Astronomical Society wrap-up

Each December, there’s a bit of a lull in astronomy news. Not only do the holidays slow things down, but astronomers are also getting ready for the winter meeting of the American Astronomical Society (AAS) in January. These AAS meetings (there’s also a summer meeting in May or June) are a particularly high-profile place to announce a groundbreaking discovery or other exciting piece of research – scientists are surrounded by their peers, with press conferences held daily throughout the week-long meeting. We’ve covered a few of these meetings in the past – you can learn more about AAS press conferences, follow Maggie’s adventures at the 2011 AAS meeting in Seattle, or even listen to our podcast from a meeting in 2010.

This year’s AAS winter meeting was held in Long Beach, CA, where astronomers got a bit of sunshine and sand as well as time to meet with their colleagues, present their research, and hear about the latest and greatest astronomy news. We wanted to share some of the highlights from the astrophysics press releases – and there are some particularly exciting ones in this meeting’s batch!

Credit: NASA, ESA, and A. Feild (STScI)

From a “zombie” to a “rogue” – the astronomy community still can’t get enough of the strange planet Fomalhaut b! First, there was controversy over whether it was a planet or a dust cloud, and now they’re looking at the planet’s unusual orbit within the debris disk of its host star, Fomalhaut. The planet’s highly elliptical, 2,000-year orbit leads astronomers to suspect that there may be other planet-like bodies hiding within the debris around Fomalhaut. One or more of these other bodies may have gravitationally disturbed Fomalhaut b, ejecting it from a position closer to the star and sending it on a wild and potentially destructive orbit through the debris disk. I’m sure this isn’t the last we’ve heard about Fomalhaut b, as astronomers are hoping to continue the hunt for other planets in its system, and to better understand its own characteristics.
Read more »

[Maggie's blog] Farthest

I was inspired to pick up where Alexe left off with her “est” blogs, and write about “Farthest,” because of some recent, cool, astronomical news.

There was recently excitement over a Hubble Space Telescope discovery of seven primitive galaxies located over 13 billion light years away from us. The results are from survey of the same patch of sky known as the Ultra Deep Field (UDF). This survey, called UDF12, used Hubble’s Wide Field Camera 3 to peer deeper into space in near-infrared light than any previous Hubble observation.

Why infrared? Because the Universe is expanding; therefore the farther back we look, the faster objects are moving away from us, which shifts their light towards the red. (The opposite of the our namesake effect, blueshift!) Redshift means that light that is emitted as ultraviolet or visible light is shifted more and more to redder wavelengths. Spectral features from galaxies that we normally see in UV or visible are likewise shifted into infrared, particularly for the most distant things. Without infrared light we might not see those features, and thus couldn’t determine the distance to these far away objects.

The extreme distance of these newly discovered galaxies means their light has been traveling to us for more than 13 billion years, from a time when the Universe was less than 4% of its current age. (Current observations suggest that the Universe is about 13.7 billion years old.)

Their discovery, which you can read more about in the NASA feature is exciting because it might give us an idea of how abundant galaxies were close to the era when astronomers think galaxies first started forming. (Phil Plait has a good column about this discovery too.)

Credit: NASA, ESA, R. Ellis (Caltech), and the UDF 2012 Team

With every year that passes, our newest technology enables us to see further and further back. The microwave afterglow of the Big Bang that was seen by the COBE and WMAP satellites is from about 378,000 years after the Big Bang. That’s a long time ago to be sure, but it was also before the first objects in the universe formed.

The questions are, how far back can we see at visible and infrared wavelengths? And what can we see?

Read more »

[Alexe's -est Blog Brightest

Welcome back to the -EST Blog! This is where we explore some of the astronomical superlatives that go the extra distance to make our universe so interesting. This time, I’ll be trying to tackle one of the brightest objects that we can see. We’re going to talk about Active Galactic Nuclei. These objects make up more than half of the bright objects we see when we observe the universe in high energy gamma rays. I talked with Dr. Dave Thompson about his work studying active galactic nuclei and why studying them is important.

Credit: ESA/NASA/AVO/Paolo Padovani

So what are active galactic nuclei? An active galactic nucleus (AGN for short) is a small region at the center of a galaxy that is much brighter than it would be in an average galaxy. A galaxy that holds one of these active nuclei is known as an “active galaxy.” The artist concept above show what these galaxies might look like up close. The active regions at the centers of active galaxies are believed to contain black holes that are millions or billions of times the mass of the sun – supermassive black holes.
Read more »

[podcast] NuStar: NASA’s Newest X-Ray Eyes

Click to listen! (7.5MB MP3, right-click to save)
Transcript (Text, PDF)

It’s an exciting experience for any space geek to watch a new satellite launch into orbit. Even through an online video feed, it’s thrilling to see something that Earthlings worked for years to create headed for its new home, to be our newest eyes on the Universe. These launches don’t happen so often, especially for astrophysics missions, where we see the launch of a new observatory every few years at most. Earlier in 2012, we were excited about the launch of NuSTAR, a small explorer X-ray mission collaboratively created by teams at Caltech, NASA, and over a dozen other institutions around the world.

NuSTAR advances the international astronomical community’s ability to observe some of the hottest, densest, and most energetic objects in the Universe. Its detectors are sensitive at significantly higher energies than other X-ray observatories such as Chandra and XMM-Newton, giving astronomers a chance to extend the range of data they collect. During its mission lifetime, NuSTAR will conduct a survey for massive black holes, study the particles accelerated in active galaxies, and observe the remnants of exploded stars and the chemical elements they’ve left behind.

We were interested to find out more about NASA Goddard’s involvement in the mission, so we interviewed post-doc Dr. Dan Wik about his work with the satellite’s optics and his interest in observing galaxy clusters with NuSTAR.

Credit: Dan Wik

Read more »

[Koji's blog] What is a Galaxy?

“Galaxy,” Defined — when I came across a paper with this title while browsing a recent issue of Astronomical Journal, I was intrigued. You would think that such a widely known term, one so fundamental to modern astronomy, would have been defined a long time ago. But then, sometimes the most widely used words are the very ones that have survived without a formal definition.

More than 200 years ago, Charles Messier compiled his famous catalog to aid him in his quest to discover comets. You see, what he found there were about 100 objects that looked fuzzy, like comets, but didn’t move from night to night. Over the next century or so, astronomers gradually realized that several distinct types of objects were included in the Messier catalog. Some are nebulae, a terminology we reserve today for clouds of gas and dust that shine for one reason or another. Some are star clusters – the Pleiades, for example, is an open cluster with over 1,000 confirmed member stars that are all relatively young. Messier 15, or M15, is a globular cluster, with probably more than 1 million stars.

Hubble image of the Pleiades, credit: NASA, ESA and AURA/Caltech

Then there are what were once called “spiral nebulae.” like the Andromeda galaxy (M31). Back around 1920, some astronomers thought that every star, nebula, and cluster belonged to one system, the Milky Way galaxy. Others thought that the spiral nebulae are island universes of their own. Soon, Hubble observed Cepheid variables in M31 and showed that it was clearly outside the Milky Way. Eventually, we came to call these “galaxies.” If there were only major galaxies with spiral arms, like Andromeda and the Milky Way, then a formal definition might not be necessary – you know a galaxy when you see one.

M31, credit: Adam Evans