Q8: How EXACTLY do astronomers measure the distance of a particular star to Earth? (In light years)

One cloudless night sky in July, you decide to take a look at stars. Six months later, work and responsibilities are getting the better of you so you decide to take another quick break from the world. You return to the same spot you observed the sky from last July and take a deep look at the night sky. Chances are, some of the stars you observed 6 months ago, have slightly changed their position when compared to the rest of the night sky. This apparent change in position is due to the Earth’s revolution around the sun. Think of it as looking at the star from a different angle. 

The above image helps illustrate parallax. Assume that the red dot in the image is a star while the January view and July view are the respective images of the night sky you observed. Obviously, the red dot is not in the same place in both views.

The image also contains the formula which shows the mathematical relationship between distance and parallax. In other words, the formula tells us how to compute for the distance given the parallax.

Alternate image to further help illustrate parallax and because who doesn’t like looking at images.

Going back to the above mentioned formula; p is the measure of the arc in seconds while d, which is the distance between the star and the Sun, is measure in parsecs. The average distance between the Earth and the Sun has its own unit which is known as 1 AU (astronomical unit). One parsec, to illustrate just how far a star can be, is equal to 206265 AU. Additionally, for those more comfortable with the measurement of lightyear (ly) which is the distance covered by light in one year, 1ly = 6.324 * 10⁴ AU.

The further away a star is from the sun, the greater the required displacement in space to obtain a discernible parallax. As such, the number of stars whose parallax can be observed simply due to the Earth’s rotation are limited. Satellites can help in this regard. They can take pictures of stars at various points in their exploration in space which astronomers on Earth can use to calculate the distances of those stars.

References and Images:

Department of Physics and Astronomy, Georgia State University. (2012). Parallax. Retrieved from: http://hyperphysics.phy-astr.gsu.edu/hbase/astro/para.html
European Space Agency. (2013). ESA Science and Technology: Stellar Distances. Retrieved from: http://sci.esa.int/education/35616-stellar-distances/
Institute of Astronomy, University of Cambridge. (n.d.). Stellar Distances – Parallax. Retrieved from: http://www.ast.cam.ac.uk/~mjp/calc_parallax.html

Prepared by: Manuel Christian Schuldes

Q7: What's the planet closest to earth's structure and atmosphere that scientists have discovered?

Structurally speaking, the closest planet would be Kepler-62 e.

In 2011, Schulze-Makuch and his team decided to come up with 2 scales which would allow scientists to determine if an exoplanet could sustain life. The first scale is known as the Earth Similarity Index (aka easy scale) which compares the exoplanet with the Earth in terms physical or structural characteristics. The properties that are compared in the ESI are: radius, density, escape velocity,  and surface temperature. The scale goes from 0, which indicates no similarity, to 1, which indicates that the exoplanet is exactly similar to Earth.

Illustrated above is the basic ESI expression wherein x_i represents a planetary property (i.e. surface temperature, radius, etc.) and x_io represents the corresponding planetary property of the Earth.

The second scale proposed in Schulze-Makuch’s paper is called the Planetary Habitability Index or PHI for short. The PHI is basically seeks to determine if the proper ingredients and chemistry are available for life to exist. The PHI is constructed in such a way as to be unbiased in the search for extraterrestrial life. In other words, it takes into account life that might exist under more exotic or extreme conditions. However, the PHI is currently not used due to the extensive amount of knowledge required of the planet. Basically, astronomers lack the planetary data to make use of the scale.

Out of the all the exoplanets that have been discovered so far, Kepler-62 e is the exoplanet that rates the highest on the ESI with a score of 0.82. Below is in image which compares Kepler-62e’s position to the Earth’s position, relative to the star they rotate about.

References:

University of Puerto Rico. (n.d.). Earth Similarity Index (ESI). Retrieved from: http://phl.upr.edu/projects/earth-similarity-index-esi

Schulze-Makuch, D., Méndez, A., Fairén, A. G., von Paris, P., Turse, C., Boyer, G., . . . Irwin, L. N. (2011). A Two-Tiered Approach to Assessing the Habitability of Exoplanets [Abstract]. Astrobiology, 11(10). Retrieved from: http://online.liebertpub.com/doi/abs/10.1089/ast.2010.0592

University of Puerto Rico. (2013). The Habitable Exoplanets Catalog. Retrieved from: http://phl.upr.edu/projects/habitable-exoplanets-catalog

Strenge, R. (2011, November 21). New system would assess odds of life on other worlds. Retrieved from: http://news.wsu.edu/pages/publications.asp?Action=Release&PublicationID=28889

Images from:

University of Puerto Rico. (n.d.). Earth Similarity Index (ESI). Retrieved from: http://phl.upr.edu/projects/earth-similarity-index-esi

University of Puerto Rico. (2013). The Habitable Exoplanets Catalog. Retrieved from: http://phl.upr.edu/projects/habitable-exoplanets-catalog

Prepared by: Manuel Christian Schuldes

Q6: Plate Tectonics on Venus and Mars

Q: With the recent findings that Mars exhibits plate tectonics, could Mars and Venus exhibit the same, since after all they do have volcanism?

A: Well, not neccesarily.

Let's start with the requirements of plate tectonics. First, there has to ba a driving force for plates to form and move. In our case, the driving force is the weight of our crust, and the heat from the interior. The heat makes the layer beneath the crust soft, allowing for convection currents that pull on the overlying crust. This heat is supplied by the radioactive decay of matter trapped in the core, a consequence of the large volume of matter that coalesced in Earth's early years. Heat may also be supplied by tidal forces from a nearby large body, such as those powering volcanism in Jupiter's moon Io. The tidal forces pull on the rocky material (such as how the moon pulls on our seas), creating friction that generates the heat.

Now let's tackle Mercury. Mercury does not have the sufficient mass and volume to have trapped much radioactive material necessary to power plate tectonics to this day. Tidal forces from the sun does effect Mercury's crust, but not enough to cause plate formation and movement. A 2008 survey of the planet has shown that it still has a molten core, but volcanism had ceased a long time ago. Chances that it still exhibits plate tectonics are slim.

Venus is another story. It has active volcanism, but present evidence cannot suggest that it has an active plate system. A theory proposed is that liquid water plays a role in plate tectonics, such that it "lubricates" subduction zones. A "wet" crust is also more likely to fail or create cracks and faults, since a dry crust can be strong enough to resist plate motion. The volcanoes of Venus are like the Hawaiian islands - volcanoes not connected to subduction zones.

These answers however, are based on plate tectonics as experienced here on Earth, which is why scientists were also surprised by the findings in Mars. Perhaps space geology still has a long way to go. No matter, what can be certain is that these planets did experience the familiar kind of plate tectoncis in their youth, when they were hotter and softer.

References:
http://www.umich.edu/~gs265/tecpaper.htm
http://www.news.cornell.edu/stories/May07/margot.mercury.html
http://csep10.phys.utk.edu/astr161/lect/mercury/surface.html
http://adsabs.harvard.edu/abs/2001AGUFM.U21A..09S

Prepared by: Benjamin Francis Rodriguez

Q5: Are the phases of the Moon the same all over the world at the same time?

RELATIVELY, THE PHASES OF THE MOON ARE THE SAME ALL OVER THE WORLD AT THE SAME TIME. =D

The reason why we see different phases of the Moon is because of the relative and ever-changing positions of the Sun, the Moon and the Earth periodically. For instance, if you have seen a full Moon, observers like you all over the world would also have seen a full Moon. This is due to the changes in the lighted portions of the Moon, and is therefore not dependent on the location of the observer.

In the Northern Hemisphere, we can identify the phases of the Moon using the following mnemonic as we face North:

DOC - The crescent preceding the full moon (waxing) is in the shape of a D, then there is the full moon in the shape of an O, followed by a crescent in the shape of a C for the waning moon.

Phases of the Moon. Retrieved from: http://www.exploringnature.org/db/detail.php?dbID=42&detID=2856

Nevertheless, people in different locations see the moon in a slightly different manner, especially if they are in different hemispheres.

In the southern hemisphere, observers would see the moon upside down (relative to the way observers in the Northern Hemisphere see the Moon) so the sunlit side is opposite to that of the Northern Hemisphere. Thus, the mnemonic now run this way:

COD - The crescent preceeding the full moon (waxing) is in the shape of a C, then there, again, is the full moon in the shape of an O, followed by a crescent in the shape of a D for the waning moon.

On the other hand, an important factor, the libration of the Moon, or the apparent rocking/rolling of the Moon, affect exactly what portion of the Moon faces the Earth especially during the first and the last quarter phase. The location of the terminator, or the line which distinguishes between the lighted and the dark portions of the Moon, may differ. Consequently, the portions of the Moon that the observers can see may vary from time to time.

Note: The Libration of the Moon can be explained by Kepler’s Laws – the Moon moves faster when it comes nearer the Earth and moves slower when it orbits farther away (on account of its elliptical orbit). This allows us to see 59% of the Moon’s surface, contrary to the common misconception that we only see half of the Moon’s surface due to its Synchronous rotation with the Earth.

Image Source:
Sheri Amsel. Phases of the Moon. In: Exploring Nature Educational Resource [Internet]. [Cited 2012 August 27]; Available from: http://www.exploringnature.org/db/detail.php?dbID=42&detID=2856

Prepared by: Ericka Jane Angeles

Q4: Why is it that the moon appear yellow in the night sky? (Not Blue or other colors)

A: The light from the Moon is actually a reflection of the light coming from the Sun. The light coming from the Sun, on the other hand, is a part of a narrow band of wavelengths called the visible light spectrum (the part of the electromagnetic spectrum to which our eyes are sensitive – and the only band our eyes are sensitive to). This constitutes a spectrum of wavelengths that range from approximately 700 nm (0.7μm) to approximately 400 nm (0.4μm).

The Visible Light Spectrum. Retrieved from: http://science.hq.nasa.gov/kids/imagers/ems/visible.html

Each color corresponds to a wavelength. Red light has the longest wavelength, and violet light has the shortest one. The photons (smallest units of light) will possess higher energy if the wavelength is shorter. Conversely, the photons of light will possess lower energy if the wavelength is longer.

The energy possessed by the photons is very much associated with the scattering of light. The light (or the color) which has the shorter wavelength will most likely be scattered compared with the light (or the color) which has the longer wavelength.

Thus, as for the question why the Moon appears yellow, the answer is: BECAUSE OF OUR ATMOSPHERE. The Earth’s atmosphere contains tiny particles of dust and molecules that facilitate the scattering of light. The light with the shorter wavelengths (violet, blue) will be scattered, thus leaving the light with longer wavelengths (red, orange, yellow) to reach our eyes.

If you are under a dense or too polluted atmosphere, you may see the Moon in orange, for much light is already scattered away.

Note:
nm stands for nanometers.
μm stands for micrometers.


Prepared by: Ericka Jane Angeles

Q3 : Solar Prominence

Q: May epekto po ba sa 'tin ang mga umaatikabong prominences ng sun?
(Do the active prominences of the sun have any effect on us?)

A: Technically no, but these always have related phenomena that can affect us. Think of it this way, a prominence (a loop of hot gas made by the sun on its surface) is usually accompanied by SOLAR FLARES, or the sudden release of a lot of energy into space, and CORONAL MASS EJECTIONS, which are the release of matter. This matter is in the form of plasma, or gas made up of protons and electrons which give the gas electric and magnetic properties; the energy is in the form of radiation.

These protons, electrons, and radiation reach the Earth, but get deflected by our magnetic field. This deflection leads to a further energized upper atmosphere, which leads to the formation of more protons and electrons here.

Many of the satellites are sensitive to an energized upper atmosphere, so their signals get disrupted. Examples of services affected are radio communication lines, Global Positioning Systems, and spacecraft electronics. The radiation from the solar flare also poses a threat to astronauts working above the Earth. Now if these phenomena are really strong, the energized upper atmosphere can induce currents in power grids on Earth, so our electricity is also affected!

But there's a good effect! The energized upper atmosphere displays beutiful aurorae near the poles!


Prepared by: Benjamin Francis Rodriguez

Q2 : Star Maps and Your Location

Q:"I have this book that has star maps for any time of the year, for both Northern and Southern hemispheres. I'm wondering if I can use them fine being that we are at the equator? What adjustments do I need to do, if any?

I've tried star/constellation-hunting with the maps in the book, looking at both Northern and Southern hemisphere maps but so far I've been unable to orient myself. That's either because (1) I am at the equator, neither Northern nor Southern, or (2) I don't know what I'm doing.

Thanks for any tips!"


A: Thank you for your inquiry. Yes, you can indeed use the star maps you have there even if you're at the equator!, it just takes a little familiarity to get your way through the stars so don't worry if at first you find yourself lost.

Usually star maps teaches you the correct orientation by just facing North or South as the Star Map indicates depending on the time of the month that you choose to stargaze.

But I'll give you a few tips instead. When you have your appropriate map for the month, look for the BRIGHTEST stars first, you'll identify them by their apparent magnitude. With star maps, the brightest stars are drawn with a larger diameter compared to others and at the legend beside the map you'll usually find an indicator showing the apparent brightness of the star, the brightest ones have a negative value.

This is important! They will serve as your guide or markers in the sky so that you can find your way and recognize the patterns drawn in your starmap.. you'll easily be lost if you dont know your bright stars!

You might get overwhelmed by the star patterns drawn in your star map but if your viewing from the urban cities you'll most likely see only the brightest of the stars, and from there i'm sure you'll find your way!

Try to find these bright stars with your star map in the night and you would know where to go: Vega (From 'Lyra' constellation), Deneb (Cygnus), Altair(Aquila) these three stars would appear to form an isosceles triangle when you connect them, once you do just find the other constellations relative to them!

Furthermore, you can practice this technique in moving through the night sky using other bright stars!

Another tip! Try to view your star map and you'll recognize that they appear to be similar to each other especially with months that are consecutive, if you become a regular stargazer you'll recognize the stars would appear to move with time from east to west, and furthermore you would recognize other constellations to appear depending on the season..

This is because the Earth is moving along the background of stars with its daily rotation on its axis and revolution around the sun, this is an important principle in stargazing that you should also know so that soon you would let go of your star map when you become familiar with the seasonal rotation of the constellations!


Prepared by: Leizl Ann Motilla

Q1. Why can't we see the Milky Way Galaxy? But we can see other galaxies with the use of telescopes.

The Milky Way

If luck and the weather permit, when the night sky is unpolluted and clear, you can actually see a part of the Milky Way even on your own backyard! Here on Earth, we can see our galaxy as a large band of stars spilled across the dark sky. Unfortunately, we cannot see much of the Milky Way and its spiral structure because the Solar System, where our planet lies, is located near at the edge of the disk and we have no means to take pictures of the top or the bottom of the galaxy. We also cannot see much of the composition on the other side of the galaxy because the neighbouring dusts and bright stars hinder our view.

On the other hand, we can view other galaxies and their structures using very powerful telescopes because they are located outside and separated from our galaxy and our Solar System, thus Earth, is located on one of the spirals at the outskirt of the Milky Way, where there are relatively fewer bright stars than inside the center of the galaxy which can obstruct our view of what lies beyond our galaxy. Think of it like this: our solar system, along with other star systems, is riding in a “bus” (the Milky Way). Inside the “bus” our solar system is seated on the far end, next to a window. The location is a perfect place to observe other buses (other galaxies) on the road and other seated passengers (star systems) from both ends of the bus, but is not a good place to see the bus driver at the opposite end of the bus.
Here in the country, the best place to observe the band of our galaxy is in the provinces where there is minimal pollution.

Keep the questions coming. Clear skies to everyone!

Prepared by: Kristine Jane Atienza