January 17, 2018

How Far? Measuring Astronomical Distances.

But a nearby stepping stone; our humble moon. (Photo by Author).

   You hear it at every star party. It’s probably the next biggest question right behind “is there life out there,” and “can you really see the flag the astronauts left on the moon with that thing?” Just how do we know how far away things are in the universe? After all, men have never ventured beyond the Moon; and it has only been in the past half century that we have sent embassaries on trajectories that will escape our solar system… just how do we measure these enormous distances with any confidence?
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Review: How Old is the Universe? By David A. Weintraub.

Out from Princeton Press.

Probably the toughest questions an astronomer ever has to field with the public are those in cosmology. How old/how big/how far are truly mind bending questions, and difficult to explain to the average man on the street in sound-bite style. This week, we look at David Weintraub’s latest, How Old is the Universe? out by Princeton Press. Fans of this site will remember our review of Is Pluto a Planet? also by Mr. Weintraub a few years back. [Read more...]

Astro-Event: A Planetary-Galactic Pairing.

This week’s astro-challenge may test your skills as a “visual athlete;” a close visual conjunction of the planet Saturn and the galaxy NGC 4073.  This unique event comes to us via the computations of reader Ed Kotapish. On the evening of July 25th, both planet and galaxy will be in a 1 degree field of view. The challenge is twofold; Saturn sits at magnitude +1.1, while NGC 4073 is about 10,000 times fainter at magnitude +11.4. Add into the mix a Moon just a day from Full, and you’ve got a definite challenge… telescopes of 6” inches aperture or larger need only apply.

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26.06.10- Pan-STARRS on Patrol.

You can rest a little easier tonight; astronomers now have a new and powerful tool in the hunt for killer space rocks. The Panoramic Survey Telescope & Rapid Response System or Pan-STARRS went online recently May 13th. Placed atop Haleakala, Pan-STARRS was constructed by engineers and astronomers at the University of Hawaii and is now owned and operated by a group of 10 institutions known collectively as the PS1 Science Consortium. The mission of Pan-STARRS is simple and straight forward; to survey the entire night sky and use sophisticated search algorithms to see if anything has moved from night to night. By rejecting known or identified objects, Pan-STARRS can go after objects of particular concern; Near Earth Objects (NEO’s) sometimes also termed Potentially Hazardous Asteroids or PHA’s. To do this, Pan-STARRS is equipped with a 60” inch diameter telescope and the largest digital camera ever built, containing a total of 1,400 megapixels. This allows it to capture a wide field area 40 times as large as the Full Moon, and it will take 500 such exposures each night. Gigantic survey projects such as Pan-STARRS pose a major challenge for data transmission and storage; Pan-STARRS will generate 4 terabytes of data per night: this will all be analyzed and archived at Maui’s High Performing Computing Center. Pan-STARRS 1 is also a forerunner to an even more ambitious project known as Pan-STARRS 4 which will be four times as powerful. Not only will Pan-STARRS discover an expected 100,000 asteroids, but it will also catalog an estimated 1 billion stars and half as many galaxies. Expect the usual complement of comets bearing the Pan-STARRS name as generally happens during any automated deep sky survey, as well as a flood of imagery just awaiting amateur perusal… I’m gonna need a faster Internet connection yet again!

11.05.10: Ancient Galaxy Mergers.

Astronomers may have found a cosmological missing link in the realm of galactic evolution. The early universe was a crowded place; galaxy mergers must have been much more common in the primeval universe than they are today. But studying those early collisions has been problematic; the immense distances involved over time and space mean that resolving clusters and individual stars are out of the question. Now, a team from the University of Western Ontario led by Sara Gallagher has published a study of an object which may serve as a “living fossil” of those early times; Hickson Compact Group 31. A cluster of irregular galaxies “only” 166 million light years away in the constellation Eridanus, this merger has somehow escaped coalescence over 10 billion years of cosmic history to just begin merging. “Because HCG 31 is so nearby,” Gallagher notes, “we can indentify individual star clusters.” In fact, two main components of HCG 31 approach visual magnitude +13 and have been snared by amateur instruments. HCG 31 is approximately 75,000 light years in diameter, and will probably one day form one huge elliptical galaxy. To conduct this study, Gallagher utilized time and instruments that spanned the spectrum, from Hubble in visible light to Spitzer in infrared to Galex and Swift in the ultraviolet. It is amazing that astronomers now have such capabilities in their bag of tricks at their ready disposal!

Astro-Challenge of the Week: Can you Spot the Brightest Quasar?

This week, we here at Astroguyz are going to show you how to go after that most elusive of beasts; a quasar. Even seasoned amateurs do not always realize that some of the brighter denizens of this elusive class of beasts are bag-able with a telescope of moderate-sized aperture. Of course, don’t expect to see much; part of the fun of this challenge is the fact you can see it at all, and the wonder of what the object actually is. Our visual prey is 3C 273 is the constellation Virgo. This object was the 273th listed in the 3rd Cambridge Catalog of radio sources, and at a 16% red-shift, stands at “only” about 2 billion light years distant! This also gives it an apparent recessional velocity of 30,000 miles per second. Visually, 3C 273 hovers at about magnitude +12.2, although it has been known to vary by about magnitude 0.5 in either direction. Its coordinates are;

Right Ascension: 12 Hours 29 minutes 6 seconds.

Declination: +02° 03’ 06” N

A good series of finder charts courtesy of the AAVSO may be had here; 3C 273 is about 4.7° NW of the star Gamma Virginis and very near the galaxy NGC 4536.

Now for the mind-blowing part; the absolute magnitude of 3C 273 is about -26; if this object was 10 parsecs distant, it would visually rival our own Sun! Its output also tops our own Milky Way galaxy by a factor of x100! As you can see, writing a post on the topic of quasars demands the extreme over-usage of exclamation points. 3C 273 is a worthy target for aperture 6” or greater, and stands as the farthest object you’ll probably ever lay eyes on. It also serves as a good reply to that common neophyte question heard at star parties; “So, how far can you see with that thing?” And just think, the light left 3C 273 when the Proterozoic era was the newest, greatest thing here on Earth… imaging may even help you grab this beast. Amateurs have even successfully recorded a spectrum of 3C 273 and measured its red-shift, a good reply next time someone asks you; “Yeah, but how do YOU know the universe is expanding?”  As the waning Moon slides out of the evening sky, I invite you add a quasar to your visual athlete-life list!

This week’s astro-word of the week is Quasar. Short for Quasi-Stellar object, this class of amazing objects was not even heard of until the early 1960s. Much controversy raged for decades as to exactly what astronomers were seeing; theories ranged from white holes to anti-matter fueled stars in the early universe. With the advent of accretion disc theory as a massive energy source outlined in the 1970’s a model of quasars slowly emerged; the consensus now is that we are seeing highly energetic galactic nuclei early in their youth. Perhaps the supermassive black hole at the core of our own Milky Way Galaxy was once a quasar itself, gobbling up interstellar matter and emitting massive amounts of x-rays and radio waves before settling down to the relatively placid state we see today. Other classes of objects such as blazars and radio galaxies have further filled in the classification gaps, and the massive amounts of energy we see in some quasars are thought to simply be the result of our viewing angle here on Earth. The brightest quasars devour perhaps 1000 solar masses of material a year, and the most distant recorded is CFHQS J2329-0301 discovered in 2007, with a red-shift of 6.43 and about 13 billion light years distant. This puts it in the realm of the very early universe, which is only 13.7 billion years old!

15.04.10- Do We Know the Future of our Sun?

Our modern understanding of stellar evolution states that our Sun is a middle-aged main sequence star, destined to bellow up into a Red Giant in a few billion years and eventually wind up as a degenerate white dwarf embedded in a shroud of a planetary nebula. Looking out at the stars in various stages of evolution in our galaxy, we see systems that have done just that. These Red Giants often exhibit a rhythmic oscillation as their atmospheres swell and contract, but about one third also display a longer five year variation that scientists do not completely understand. Now, a study conducted by the European Southern Observatories’ Very Large Telescope (VLT) is looking into this mystery by studying 58 sun-like stars towards their elderly Red Giant stage located in the Large Magellanic Cloud. Known since the 1930’s, this mystery has baffled astronomers. “Astronomers are left in the dark, and for once, we do not enjoy it,” stated Christine Nicholls of Australia’s Mount Stromlo Observatory. Some of the long term pulsations could be explained by the presence of an unseen binary companion, but not all. This phenomenon is of special interest to astrophysicists because our own Sun may one day throw similar temper tantrums. Could stellar evolution be in need of tweaking?

10.04.10- Radio Astronomers Refine Celestial Grid.

Getting a good fix on positions both on the Earth and in the sky is tougher than it may sound. Tectonic plates move. The Moon raises tides under our feet. The whole planet orbits our Sun, which is itself flying about the galaxy and getting jostled by other stars, as the galaxies themselves are flying apart. Last year, however, astronomers at the National Science Foundation’s Very Long Baseline Array of radio telescopes tackled the problem in a novel way. Using 35 radio telescopes worldwide, they monitored and measured the positions 243 quasars over a 24 hour period starting November 18th 2008. Quasars are ideal candidates for this kind of measurement because of their extreme distance. These high precession measurements break the old record for the most radio dishes employed, which stood at 23. The telescopes utilized a method known as Very Long Baseline Interferometry, which combines simultaneous signals collected over individually spaced telescopes to increase resolution power. Headquartered in Socorro, New Mexico, the VLA’s data will not only refine astronomical measurements, but increase the accuracy of geophysical science as well.

13.03.10: Galaxy Zoo vs. the WWT.

Students at Southern Illinois University Edwardsville have successfully merged two outstanding resources into a single, powerful tool. Recently, Microsoft unveiled the WorldWide Telescope, (WWT) an online resource that allows users to browse images and data culled from the Sloan Digital Sky Survey. When they looked at classifying the myriad of galaxies presented, they turned toward another awesome resource; Galaxy Zoo, a citizen science project that encourages users to analyze and identify galaxy types. Now, software designed by students Mark Sands and Jarod Luebbert gives the quarter million users of Galaxy Zoo an interface to travel through the simulated universe of the WWT and share these gems with other users in a custom tailored tour. Pamela Gay, of Astronomy Cast fame, laded the effort; “Now it is possible to share these jewels with people who can’t see my screen…they’ve made it possible for all of us to inflict our favorite galaxies on everyone in our lives.” Awesome job indeed, Mark & Jarod!

29.9.9:Hubble Spies a Galactic Jet.

The formerly ailing Hubble Space Telescope spied something remarkable earlier this year; a rapidly expanding jet around the massive galaxy M87. Dubbed HST-1, this blob of matter is the first object with a Hubble designation, and has been tracked for over seven years. Brighter than the galaxies’ own core, the gas knot is 214 light years from the core and receding. M87 is visible in the constellation Virgo with a backyard telescope, and is part of the massive Virgo cluster of galaxies about 54 million light years away. The growth of the brightness of the jet expanded by 90 fold over the past decade, giving astronomers the opportunity to examine an active galactic nucleus in action. As the refurbished Hubble begins to strut its stuff, doubtless HST-1 will be an object of increased scrutiny!