Monday, August 18, 2014

The First Planetary Nebula Spectrum

Sky and Telescope has an article "The First Planetary Nebula Spectrum." 150 years ago this month was the first time anyone had take spectrum of a planetary nebula.

At the time the word "nebula" covered a variety of objects that were visible in telescopes, but whose composition was not understood. The observed spectrum gave important clues about one type of nebula, namely the planetary nebula.

See this link....

http://www.skyandtelescope.com/astronomy-news/observing-news/first-planetary-nebula-spectrum-08142014/

Sunday, July 27, 2014

Calendar of Astronomy Events in Southeast Michigan

The University Lowbrow Astronomers (Lowbrows for short) maintains an astronomy calendar. This calendar is focused on events in the Southeast Michigan area and includes:

  1. Open Houses at Peach Mountain Observatory (located near Dexter Michigan).
  2. Club Meetings of the Lowbrows (held on the central campus of the University of Michigan).
  3. Other astronomy events that may be of interest in the Southeast Michigan Area.

You don't need to be a club member or affiliated with the University of Michigan to attend these events. There are four different ways to view the calendar:

1. Go to the web page: http://www.umich.edu/~lowbrows/calendar/

2. If you have an Android tablet or smartphone, you can download the Lowbrow App at

https://play.google.com/store/apps/details?id=org.lowbrows.lowbrowapp

This app is free. You can view the calendar directly from the app.

3. If you use a calendar program that supports the ICAL format (such as Google Calendar), you can subscribe to the Lowbrow Calendar by using the subscribe function within your calendar program. This will allow you to view Lowbrow events along with the events in your personal calendar and/or other calendars. When subscribing to the calendar, you will be asked for a URL. This is the URL:

http://www.google.com/calendar/ical/lowbrowcalendar%40gmail.com/public/basic.ics

4. If you use a calendar program that supports the ICAL format (such as Google Calendar), you can take a snapshot by downloading this file:

http://www.google.com/calendar/ical/lowbrowcalendar%40gmail.com/public/basic.ics

and importing it into your program. The events in the Lowbrow calendar will be added to events already in your calendar, but if there are changes to the Lowbrow calendar they will not be automatically incorporated into your calendar without a subsequent import.

Thursday, July 3, 2014

Ceres, Vesta and Pluto

Ceres and Vesta will be very close to each other over the next few days. (That is they appear to be close to each other when observed through a telescope).

What are Ceres and Vesta? Ceres is the largest asteroid and the first to be discovered, Vesta is the second largest asteroid and the fourth to be discovered. They are too dim to be seen naked eye, but bright enough to be easily seen in a small telescope (provided you know where to look). There is more information on this Sky and Telescope article....

http://www.skyandtelescope.com/astronomy-news/observing-news/ceres-and-vesta-in-2014/

Pluto reaches best visibility on July 4th, though it is possible to observe it for some time. Pluto is not visible naked eye, but if you know exactly where to look, it is possible to see it in many amateur telescopes (provided it is large enough or if the sky is dark enough). The trick is to know which of the many dots of light in the field are stars and which is Pluto. More information on this page....

http://planetpluto.info/index.php?document_id=100

When Ceres was discovered, it was considered to be a new planet. There was something called the "Titius-Bode Law", which predicted how far each planet should be from the sun. This relationship was reasonably accurate in describing the planets from Mercury to Uranus if you assumed there was a missing planet between Mars and Jupiter. (Neptune and Pluto had yet to be discovered). Ceres seemed to be that missing planet.

Over time when other objects were discovered between Mars and Jupiter, such as Pallas (an asteroid somewhat smaller than Vesta) and Vesta, they too were considered planets. However as more and more objects were found eventually it no longer made sense to consider any of them as planets; we now call them asteroids.

Since that time Neptune and Pluto were discovered and added to the list of planets. Eventually most scientists came to the conclusion that the Titius-Bode law was mere coincidence, and not a useful tool for predicting the existence of new planets. It did not correctly predict Neptune's distance from the sun, and it only predicted one object between Mars and Jupiter, not the multitude of objects now known.

Beginning twenty years or so ago, there was reason to question the status of Pluto. Objects beyond Pluto were discovered. Some are known as Kuiper-Belt objects after one of the astronomers who predicted their existence. Others are in a region called the "Scattered Disk." One of the later is bigger than Pluto. All these objects (along with Pluto and the so far unobserved Oort Cloud objects) are collectively called TNOs (trans-Neptunian objects). So it is still reasonable to consider Pluto as the ninth planet, or is it merely one of many TNOs?

Now some argued that objects in the solar system should be divided based on size. If so we have "large" objects that are in "hydrostatic equilibrium" (that is they are large enough that gravity forces them to be round). And we have smaller objects (which are generally lumpy-not round). All the traditional planets (including Pluto) would be "large". Also in this group would be Ceres, the largest moons of the solar system (including the Earth's Moon), and the largest TNOs. This list includes between 30 and 40 known objects and almost certainly includes dozens of objects yet to be discovered. This does not include the smaller asteroids (that is all asteroids except Ceres and Vesta), comets, the smaller moons and the smaller TNOs. Vesta is generally considered too small to be in hydrostatic equilibrium; however whether it is or is not is debatable.

It seemed that a clear definition of the word planet was needed. The word has always been poorly defined. With the discovery of a TNO bigger than Pluto, the issue could no longer be avoided. A definition of planet was constructed that included all of the traditional planets, with the notable exception of Pluto, and did not include any other object in hydrostatic equilibrium (moons, Ceres, the handful of large TNOs).

The definition essentially says a planet must be in hydrostatic equilibrium, and it must be the dominant gravitational object in its vicinity. This cuts off Pluto (which is under the influence of Neptune) and the other TNOs (which are under the gravitational influence of other TNOs). It cuts off Ceres (which is under the influence of Jupiter and other asteroids), and it cuts off moons (as each is under the influence of its parent body). Objects that are not planets would be called a moon if they were in a clear orbit around another object, or a dwarf-planet if they are large enough to be in hydrostatic equilibrium, not a moon, and didn't dominate their environment gravitationally. Both Pluto and Ceres are considered dwarf-planets. Vesta is probably not a dwarf-planet. This definition was adopted by the International Astronomical Union (IAU) in 2006.

An alternate argument for excluding Pluto goes as follows: Pluto is very different than rocky planets (such as Earth and Venus) and it is very different than the gas planets (such as Jupiter and Saturn). Pluto is best described as a "dirty snowball" and as such is very similar to Kuiper-Belt objects. In fact it makes sense to say that Pluto is a Kuiper-Belt object.

Note, not everyone is happy with the IAU definition...

For more reading, here are some Wikipedia articles on the topics in this post....

http://en.wikipedia.org/wiki/4_Vesta
http://en.wikipedia.org/wiki/Ceres_(dwarf_planet)
http://en.wikipedia.org/wiki/Titius%E2%80%93Bode_law
http://en.wikipedia.org/wiki/Hydrostatic_equilibrium
http://en.wikipedia.org/wiki/List_of_gravitationally_rounded_objects_of_the_Solar_System
http://en.wikipedia.org/wiki/IAU_definition_of_planet
http://en.wikipedia.org/wiki/Kuiper_belt

Saturday, June 21, 2014

Explosion of Monocrotis V838

Here is a video made from Hubble images of the star Monocrotis V838.

http://www.cnn.com/video/data/2.0/video/tech/2014/06/13/orig-jag-nasa-hubble-timelapse.cnn.html

This star was discovered about 12 years ago. It was immediately recognized as a "variable star", a star whose brightness changes over time. The Hubble telescope made regular observations of Monocrotis V838 over the next 4 years. It has brightened, then dimmed, then brightened again. The pattern of brightening and dimming is unlike any other variable star observed to date. At its brightest, it was one of the brightest stars in our galaxy (in absolute terms). Read this Wikipedia article for more details....

http://en.wikipedia.org/wiki/V838_Monocerotis

LOWBROW MEMBER’S IMAGES APPEARING IN LOCAL SHOW

LOWBROW MEMBER’S IMAGES APPEARING IN LOCAL SHOW

Perhaps Lowbrows remember an email that was received from “The Gallery Project” a few months ago. They were looking for images for the upcoming “Unseen” show.  Brian Ottum responded and they have selected a few of his shots to include in the show.  Their explanation of the theme:

“The quest to see lies at the heart of human urgency. To breach the barrier between the visible and the invisible is compelling, emotional, informative and even magical. This process of discovery has always driven thinkers and image makers: artists, scientists and philosophers, from astronomers to nanotechnologists, from documentarians and data analysts to planners and prognosticators. As the unseen becomes seeable and seen, a pivot occurs, revealing and demanding irreversible change. No one who has seen is ever the same.”

The show will be in Detroit’s Eastern Market for the month of August, then move to the Ann Arbor Art Gallery September 12 to October 12.

See The Gallery Project’s website for more information:

http://www.thegalleryproject.com/

Here are Brian’s subjects and why they fit with the theme:  Rosette Nebula has Bok Globules where stars form within an opaque cocoon.   Bryce Canyon rock spire points to the center of the Milky Way galaxy, where a supermassive black hole is invisible behind stars, gas and dust.  Rho Ophiuchus region has large dark rivers of dust clouds that hide objects behind.  Finally, the Orion Nebula is both a stellar nursery and also contains three mysterious straight lines – geosynchronous satellites.

Thursday, May 15, 2014

The Camelopardalids Meteor Shower

There is a new meteor shower (called the Camelopardalids), that is expected to peak the evening of May 23 and the morning of May 24. Because it is new, no one is 100% certain how it will be behave. Or even if it exists at all.

If the predictions are correct, observers in southern Canada and the continental United States are best positioned to see the shower. The predictions may be wrong; even if you live somewhere else it is worth taking a look. Meteor showers are easy to observe, all you need is clear skies, a little patience and of course meteors.

For more information see

http://earthsky.org/space/comet-209p-linear-meteor-shower-storm-may-2014

Earth from the International Space Station

You can watch the earth from cameras recently installed on the ISS (International Space Station).

http://www.ustream.tv/channel/iss-hdev-payload

Please note, you may see a grey screen or a black screen. When the ISS is on the night side of the earth, you get a black screen. A grey screen indicates they are switching cameras or there is a technical difficulty.