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Sunday, August 30, 2015

Searching for Extragalactic Supernovae

Just a few weeks ago I was down and out with one of those annoying summer colds. Having no energy to do anything, laying there next to my plethora of cold remedies, I started reminiscing about the days when fellow astronomer, Dale Alan Bryant and I would go out night after night visually hunting for extragalactic supernovae. Of course, while reliving those fond memories, I couldn't help but dwell on the night we independently discovered the extragalactic supernova in the spiral galaxy M66 in the constellation of Leo on the morning of February 11, 1989.

"Grus Quartet" - Imaged by Michael Petrasko and  Muir Evenden of Insight Observatory.
"Grus Quartet" - Imaged by Michael Petrasko and  Muir Evenden of Insight Observatory.

I started thinking about how great it would be to start or join such an exciting and fulfilling program again. I could actually start "observing" galaxies while recovering from my cold without taking the risk of worsening my condition by staying up during the late-night hours visually observing galaxies. My other thought was that there aren't many galaxies to observe in the northern hemisphere during the nighttime hours this time of year.

But wait! I can now observe galaxies and hunt for extragalactic supernovae during the daytime hours. I got out my Chromebook and loaded up the Stellarium planetarium app and briefly scanned for galaxies that I could image and look for exploding stars within. Stellarium showed me a grouping of four different types of galaxies in the southern constellation of Grus, the crane. I then logged into our account on the telescope network that we utilize for astronomy education here at Insight Observatory. I figured a wide-field telescope would be the appropriate instrument to capture all four galaxies together within the same frame. The remote telescope of choice was a 4-inch Takahashi FSQ ED refracting telescope mounted on a Paramount PME mounting system along with an SBIG STL-11000M CCD imaging camera.

Unfortunately, the telescope network was quite busy that day with other users accessing the remote instruments from all over the globe. However, the telescope network has an intuitive reservation system that allows users to reserve telescope time and create an observing script to run during the time allocated for our use. As I started losing my energy once again, I figured that would be the best solution. I reserved a block of telescope time on the 4-inch refractor for the following day. The script I created was taking a series of 5-minute exposures with luminance, red, green and blue filters. This allows a color image to be created with the monochrome CCD camera.

Fortunately, the weather was good the following day at the remote telescope site in Australia to acquire the images. Once the raw data was uploaded to our cloud-based server, my colleague Muir Evenden, processed the series of images in PixInsight to create a color image. I then took that image and post-processed it in Adobe Photoshop.

After analyzing the final product. I realized that this contemporary process of gathering data for extragalactic supernova searching is two-fold. There is the process of gathering the data that can be taught to students as well as the actual examining of the data.

The Grus Quartet is a group of galaxies in Grus the crane. They consist of, NGC 7599, NGC 7590, NGC 7582 (largest and brightest) and NGC 7552 (farthest away from the main trio).
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Saturday, August 22, 2015

Twinkle, Twinkle, Little, Red Star

This is a COMSIM of the recently discovered planetary system, Gliese (GLEE-ZUH) 876, a red, type-M star with some similarities to the Sun (type-G), 15 light-years away, with three planets in orbit around it. It was discovered by the Kepler Mission Space Telescope.

As can be seen, planets do not necessarily orbit their host stars in an orbital plane, perpendicular to the star's axis of rotation, in the way that the planets of our solar system do. This came as a bit of a surprise to me when I found out that a high percentage of exo-planetary systems actually exhibited this arrangement (I don't have that figure with me at the moment).

Illustration of the Gliese 876 Planetary System.
Illustration of the Gliese 876 Planetary System.

The green disk represents the extent of the habitable zone (popularly referred to as the 'Goldilocks Zone'), of Gliese 876, in which, two planets, "876 b" and "876 d", partially occupied, in eccentric orbits, relative to each other. The zone is shown at an angle perpendicular to Gliese 876's axis of rotation.

The parent (host) star of this system, Gliese 876, is an 11th magnitude star. This means that, although the system is 87,000,000,000,000 (87 trillion) miles away - it can actually be seen in a medium-sized (6" aperture) telescope. Take a look!

Dale Alan Bryant
Senior Contributing Science Writer
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Wednesday, August 12, 2015

Prague Astronomical Clock

One of the nice things about living in Europe is the abundance of artefacts and places of astronomical interest...amidst all the culture and history you would expect to encounter travelling and visiting different cities and countries, one finds that they eventually run across a historical attraction which piques the interest for those of us who have a passion for astronomy. Today we visit the city of Prague (about an 8-hour train ride from my residence in Krakow Poland) and look at the Astronomical Clock in Prague.

Prague Astronomical Clock.
Prague Astronomical Clock.

The Prague Astronomical Clock is built into the facade of Old Town Hall in Prague and is believed to have originated around the year 1410. Various modifications, upgrades, and reconstructions have occurred over the centuries (the details of which could be a whole book in itself), but what I found particularly interesting was the wealth of data they were able to convey from the gears, pulleys, and flywheels of the clock.

When viewing the Astronomical Clock we can see time on four different scales:
  • Old Czech (Italian) Time: Marked on the outer "24-ring", a new day is counted by the setting of the sun.

  • German (Local) Time: Marked by Roman numerals on a disk inside that of the outer ring.

  • Planetary Time: Measured from the rising to the setting of the sun, used in astrology.

  • Sidereal Time: Shows current position of starfield above, indicated by a star on a zodiac ring.
Other useful astronomical information can be derived from the clock as well:
  • The height of the sun and the moon above the horizon is shown throughout the year.

  • The rising and setting of the sun and moon are shown, as well as the current phase of the moon.

  • The astronomical night is indicated (when the sun dips 18 degrees below the horizon).
Along with the useful astronomical data on display we also have a number of features of purely artistic or religious purposes, most notably:
  • A number of carved wooden figures stand aside from the clock. When the clock hits the top of the hour and the bells chime, the figures animate and move - the most interesting of these is the skeleton which pulls the rope that chimes a bell and he (she?) turns an hourglass over, a symbol of the passing of time.

  • Also at the top of the hour when the clock chimes two shutters above the clock open and figures of the twelve apostles appear in the windows briefly.
You can see the clock in action below as the top of the hour is reached:

It was enlightening to discover what our ancestors were capable of without the use of modern computers and technology!
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Sunday, August 2, 2015

Here Come the Perseids!

The 2015 Perseid meteor shower will peak around August 11. The new moon on August 14, 2015, will create perfect conditions for watching the meteor shower.

In the Northern Hemisphere, the annual Perseid meteor shower probably ranks as one of the best and most popular meteor showers of the year. This epic event takes place during the dog days of summer when many families are on vacation. As this time of year offers comfortable temperatures during the overnight hours, this allows us to lay back under the stars for hours and enjoy this spectacular display of comet debris. No matter where you live worldwide, the 2015 Perseid meteor shower will most likely be fine on the mornings of August 11th through the 14th. 

Radiant of Perseid Meteor Shower
Radiant of Perseid Meteor Shower

On a dark, moonless night, you can often see 50 or more meteors per hour from northerly latitudes, and from southerly latitudes in the Southern Hemisphere, perhaps about one-third that many meteors. Fortunately, in 2015, the waning crescent moon comes up shortly before sunrise, so you’re guaranteed of dark skies for this year’s Perseid meteor shower. Thus, on the Perseids’ peak mornings, moonlight will not obscure this year’s Perseid meteors.

For observers in the Southern Hemisphere, the Perseid radiant never climbs above the horizon, which will considerably reduce the number of Perseid meteors you are likely to see. Nevertheless, on the night of maximum, it is possible to see 10-15 meteors per hour coming up from the northern horizon.

There are other, weaker meteor showers going on around the same time as the Perseids, but the Perseids will generally appear to move much faster across the sky than meteors from the other showers. In fact, the Perseids are among the fastest moving meteors we see every year. Another way to know if the meteor you saw was a Perseid is to trace the meteor backwards. If you end up at Perseus then you have probably seen a Perseid meteor! If you are not sure where Perseus is in the sky, the following chart pictured to the left will help you find it from both the Northern Hemisphere and Southern Hemisphere.

Perseid Meteor Shower 2012. Image by David Kingham
Perseid Meteor Shower 2012. Image by David Kingham

Where do the Perseids come from? - Made of tiny space debris from the comet Swift-Tuttle, the Perseids are named after the constellation Perseus. This is because the direction, or radiant, from which the meteor shower seems to come in the sky lies in the same direction as the constellation Perseus, which can be found in the north-eastern part of the sky. While the skies light up several times a year by other meteor showers, the Perseids are widely sought after by astronomers and stargazers. This is because, at its peak, an observer can see 60 to 100 meteors in an hour from a dark place.

If you have a chance to get away for a long weekend with the family and you live in the New England area, be sure to look into the annual Stellafane Convention. It is a gathering of amateur telescope makers and astronomers from around the globe. Due to the convention falling on the weekend of August 15th this year, along with the non-existing moon in the sky, the dark skies will provide excellent viewing for the Perseid meteors. Even though the peak will be over on August, 14th, there will be still many meteors to catch for about a week after.
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