Sometimes astronomers come down with a peculiar condition called Aperture Fever. In short, no matter what size their telescope mirror is, they always want a bigger one. But, there’s a limit to the size of mirror (or radio dish) you can build and still have it be useful. You could probably pour a piece of glass 100 meters across, if you wanted to. You could build a huge radio dish, if you wanted to. But, getting a big piece of glass or a monstrous dish on a support and keeping them from breaking under the pull of gravity (or at the very least, keeping them from distorting and bending due to gravity’s tug on it) would render them useless.
Light collected by three VLT Auxiliary Telescopes, and combined using the technique of interferometry, provides astronomers with vision as sharp as that from a giant telescope with a diameter equal to the largest separation between the telescopes used. To obtain the image of T Leporis using data from the Very Large Telescope Interferometer, astronomers used the four 1.8-metre Auxiliary Telescopes in different configurations to mimic a telescope almost 100 metres in diameter, as represented schematically on this artist’s impression of the Paranal platform
There are some cures for aperture fever, however. The latest was demonstrated in Chile by a group of French astronomers who ganged together all the telescopes at the European Southern Observatory.
Essentially, what the astronomers did was create a 100-meter-wide interferometer — a sort of “virtual” telescope consisting of several smaller (1.8-meter) VLT Auxiliary telescopes. The result was an aperture the size of a much larger telescope. They made several observing runs with this special set-up to collect the light streaming from their target, and then combined that light into one very fine image.
What makes this use doubly cool is that they used it to create one of the first infrared interferometry observations. That’s quite a feat.
Their target was the star T Leporis, a type of pulsating star called a Mira variable (named after the star Mira, which is the “prototype” for these kinds of stars).
Mira stars are among the biggest factories of molecules and dust in the universe. T Leporis is a fine example of this activity. It pulsates with a period of 380 days and loses the equivalent of the Earth’s mass in dust and gas every year. Since the molecules and dust get created in the layers of atmosphere surrounding the central star, astronomers would like to be able to look at these layers in great detail to see how it all happens. But this is no easy task, given that the stars themselves are so far away. Even though we’re talking about a huge star, from a distance of 500 light-years T Leporis appears quite small — about half a millionth of the size of the Sun. This is where interferometry and repeated observing runs can make a huge difference.
The reconstructed image shows this star up-close. It’s 100 times larger than the Sun, and is surrounded by a sphere of gas about three times larger than the star itself. That we can even see this level of detail in a star that lies 500 light-years away shows that aperture fever can be slaked with a virtual telescope and the right amount of observing time.
Astronomy is truly a science that takes you places. At one level, it has brought ME to Long Beach, CA to hear about the latest and greatest astronomy discoveries. At another level, it is bringing us (scientists, writers — and ultimately our audiences) out to the most fascinating places in the cosmos.
“Where?” you ask. How about the core of the Milky Way Galaxy? Q.D. Wang of the University of Massachusetts at Amherst used the Hubble Space Telescope to make an infrared mosaic of the center of our galaxy. It’s a beautiful panoramic view that takes in an area of space measuring 300 x 150 light-years.
The core of the Milky Way in an infrared mosaic from Hubble Space Telescope. (click to embiggen)
This is a “false-color” image taken through a filter that reveals the glow of hydrogen gas heated by winds from new stars revealed as a new population of massive stars at the core. And the cool thing is that this is the sharpest infrared picture ever made of the galactic core.
Astronomers are looking at this region to understand how massive stars form and what they do to their local enviroment during their tempestuous birth process. If we can understand how it works in OUR galaxy then we have insight into how it works in the cores of other galaxies, particularly the active ones. Read more about this fascinating image at at the Space Telescope web site.
This 0.6 by 0.7-degree infrared photograph of the galactic center shows a large population of old, red stars. However, the discovery of two young protostars within a few light-years of the center of the Milky Way shows that stars can form there despite powerful gravitational tides due to the supermassive black hole. Credit: 2MASS/E. Kopan (IPAC/Caltech)
Now, looking at the center of the galaxy is difficult, since it’s shrouded in dust clouds. The good news is that we can plumb those depths using infrared and radio telescopes. Astronomers at Harvard-Smithsonian Center for Astrophysics and the Max Planck Institute for Radio Astronomy have used the Very Large Array in New Mexico to study young stars that really shouldn’t be there.
This is because the core of the galaxy is not a gentle creche where young stars should be able to form. It’s wracked with powerful radiation and gravitational tides stirred up by the four-million-solar-mass black hole that’s hidden at the core. It’s a place where stars go to get gobbled up, not get born.
So, nobody’s sure how a pair of protostars started to form at a spot only a few light-years from the galactic center. What this tells us is that this place, as wild as it might be, can still nurture star formation. Now astronomers will spend time figuring out how and why this is happening.
Artist's Conception of our Milky Way Galaxy: Blue, green dots indicate distance measurements. CREDIT: Robert Hurt, IPAC; Mark Reid, CfA, NRAO/AUI/NSF
This scenario may suggest that star-forming clouds may be much denser than we thought. For more information, check out the story here.
Continuing our look at the Milky Way, the folks at the National Radio Astronomy Observatory are looking at our galaxy using the Very Long Baseline Array radio telescope and what they’re finding is redefining what we know about our galactic home. Essentially, the Milky Way is rotating faster, is heavier, and is more likely to collide with other galaxies than we used to think.
You can read more about their findings at the link above, but just to give you an example of what they’ve found: at our location in the galaxy — some 28,000 light-years away from the core of the galaxy — we’re speeding along at 960,000 kilometers per hour (600,000 miles an hour).
An asteroid bites the dust around white dwarf star.
A little closer to home, astronomers continue to focus attention (and detectors) on exoplanets — worlds circling other stars.
The white dwarf GD40 and five other similar type stars came in for some attention by Mike Jura of the University of California, who used the Spitzer Space Telescope to study the remains of asteroids chewed up as the stars went through their red giant phase and then shrank down to become a white dwarf. That chewing action generated dust, which can be spotted with infrared-sensitive detectors. A star with MORE dust around it is “brighter” in infrared than a star with NO dust.
Ultimately, what their research suggests is that the same materials that made up our planet and other rocky worlds may be pretty common in the galaxy and the universe. You can read more about their work here.
NGC 2362 This photograph from NASA's Spitzer Space Telescope shows the young star cluster NGC 2362. By studying it, astronomers found that gas giant planet formation happens very rapidly and efficiently, within less than 5 million years, meaning that Jupiter-like worlds experience a growth spurt in their infancy. Credit: NASA/JPL-Caltech/T. Currie (CfA)
One of the more intriguing stories is about how baby Jupiters form around other stars.
It turns out that, according to scientists at the Harvard-Smithsonian Center for Astrophysics (who used the Spitzer Space Telescope to look at stars in the cluster NGC 2362 to detect infrared signatures of active planetary formation) a Jupiter-type planet has a pretty short time frame to form before the dynamics of the system shut off the process.
For our solar system, that means that Jupiter took only 2 to 3 million years to spring into being, whereas Earth took 20 to 30 million years to aggregate and solidify. Read more here.
Finally (for now, anyway), I got a press release detailing the upcoming WISE mission, which will provide a highly detailed all-sky survey in the infrared, from 3 to 25 microns. It’s supposed to launch in 2009 and will map the sky for at least seven months. The scientists who use this instrument hope to find the most luminous galaxies in the universe, find the closest stars to the Sun, detect most of the asteroids in the Main Belt, and do a number of different studies of planetary discs around other stars.
