One of the joys of astronomy is going out into your backyard on a clear night and observing whatever catches your attention. However, a little planning can greatly enhance the experience. That’s where Astronomy Today’s SkyGuide for 2009 comes in. It contains observing info on the Moon, Planets, Planetary Transits and Conjunctions, Meteor Showers, Lunar and Solar Eclipses. Enjoy!

We received some very interesting questions on the Astronomy Today Forum last month which I sent to several amateur astronomers whom I consider to be “experts” on the subject.

Guess who stepped up to the challenge: our colleague, Ms. Brenda Culbertson, and her friend and co-worker, Dr. Brian Thomas Assistant Professor of Physics and Astronomy at Washburn University in Topeka, Kansas. After dedicating their much coveted time to satisfying our curiosity and furthering our understanding of Cosmology, Philosophy and Science, the talented pair have submitted their work to us. Ms. Culbertson reminds me that Dr. Thomas answered most of the questions (quite thoroughly and entertaining I must add …) and she edited his responses to make them more comprehensible to the majority of our readers. (Thank you Brenda!)
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Q1: When we look into space we can see back in time some 14 billion years. Can we see this far in all directions? If so wouldn’t that mean we are at the centre?
A1. There are a couple of ways to think about this. First, you can think of yourself as a very tiny bug who lives inside a very, very, very large loaf of raisin bread. Using your amazing bread-penetrating radar, you are able to see that there are raisins in every direction away from you, as a far as you can see in every direction. If your radar (or for us, our telescope) is limited in how far it can see, then it’s impossible for you to say that you live at the centre of the loaf (universe). It could be that you live somewhere near the “edge”, but your instruments just aren’t able to see quite that far.
In reality, most cosmologists think there simply is no edge or middle to see. Another way to think about the problem, which gets at this aspect, is to think of yourself standing on the Earth. If you look all around you, you might think that you’re standing on the centre of a flat plane. Of course, you know that you are standing on the surface of a sphere. Along that surface (not inside, but *along* the surface) there is no center and no edge, even though the surface is finite, not infinite. The problem with this analogy is that it is a 2D surface, while we live in a 3D universe. The same reasoning applies, but it’s much harder (impossible?) to visualize. Regarding this question, consult this video.

Q2: I understand the universe is expanding with our galaxy likened to dots on a balloon. The space constantly increasing between them as the balloon is inflated. So how is it possible for galaxies to collide? A short cut through warped space? Perhaps it should be compared to two or more balloons inside one another, lots of “little” Big bangs. Possibly not all at the exact same location.
Q3: If our galaxy and Andromeda are going to collide and we were both created at approximately the same point in space shouldn’t a line between them have to point at the approximate center of the universe? Would a line drawn between other colliding galaxies point to the same location?

A2 and 3. Galaxies deplete and grow during long intervals of time. They are also in constant motion about an axis and, as a whole, through space. Some are in strings or clusters, but they are still moving. We have not seen a spot void of galaxies. While the universe is expanding, on smaller scales, galaxies feel each other’s gravity and are drawn together by this force. Just like our planet is held in orbit around our Sun, galaxies can be held in orbit around each other, or be pulled together strongly enough to collide, merge together, or pass through each other. Milky Way Galaxy and Andromeda are close enough that the mutual gravitational force is pulling us together. But a galaxy a billion light years (or even a few 10s of millions of light years) away feels such a tiny force from our galaxy that its motion with the expansion of space is unaffected, so we see it moving away. This is because gravity weakens quickly with distance (one over distance squared).
Here’s some relevant web material: News article, Animation, Podcast and Video.
See also answer to #1 regarding the centre. Also, galaxies are not oriented in any preferred direction (and yes, people have actually studied this question - Galaxy Zoo data has been used, for instance), so a line drawn between any two galaxies would point in a random direction, even if there was a centre to the universe.

Q4: If everything were created from a single location in a microsecond of time everything should be moving away from that point. After some time that point in space should be devoid of most matter, a big huge empty sphere. Has anything like that been seen?

A4. This seriously misunderstands the big bang model, but it’s a common misunderstanding. Big Bang cosmology tells us that *all of space* began at once. It was not “inside” anything. The universe is not expanding “into” anything (and this is a problem that the balloon analogy has). Therefore, a better way to think of it is that all the matter, energy *and space* that now exist were once all at a single point, and then space began to grow and objects began to travel farther apart. Again, no centre, no edge - weird!
We do know with extremely high confidence that the universe is expanding. Hubble (the man, not the space telescope!) discovered this in 1929. We also know with somewhat less confidence that the expansion is actually accelerating, not slowing down, and most cosmologists expect it will continue to expand forever. We also know to fairly high confidence that the geometry of space is flat. The accelerating expansion is attributed to some repulsive “dark energy” force of which we currently have no real understanding, other than we can observe the effects on the expansion of space. (There are some alternative ideas here, such as the new oscillatory model of Steinhardt and Turok, and a model that says that the universe’s geometry is actually a dodecahedron, but these are mostly speculative and less well supported by observational evidence.)

Q5: Perhaps with the improved Hubble we will see the edge of space, (moments after the big bang) not the farthermost edge but the edge of that huge empty sphere in the middle. It might appear all around us due to warped space.
A5. See #1 again. Most of us think that there is no edge to be seen, no matter the technology, and also no matter the time - no edge at the start, no edge now. Also, recall that looking out means looking back in time. So, we see the universe as it was at earlier times, not as it is now (except nearby).
This video gives a fly-through of our current understanding of what the universe looks like on the largest scales (based on observations of where galaxies are, from the Sloan Digital Sky Survey). The Astronomy Cast podcast is recommended, it covers many different astronomy questions and does a very good job of explaining the hard concepts. Astronomy Notes is also a good general reference ….

Important points to ponder on a dark night as you peer into space from the Blue Planet.

Atlantis in the Vehicle Assembly Building at Kennedy Space Center.

(To move around on the image, click and drag left, right, up, down. Also visible is part of the Ares I-X Upper Stage Simulator in High Bay 4.)

This link courtesy of Mr. Chuck Shaw (JSCAS) on the Sidereal Technology telescope drive yahoo group - the illustrious Mr. Shaw was responsible for planning and coordinating the Hubble Repair mission.

Just as the telescopes of the 17th century opened the sky for discoveries of star clusters and nebulae, 21st century telescopes examining these star cities give us a glimpse of early star formation in the Universe, and of the origin of the basic elements of the periodic table. Some globular clusters harbour black holes, while others may be the remnants of galaxies shredded by the tidal forces of the Milky Way. And above all, globular clusters are magnificent sentinels in the night sky, shining with the power of hundred thousand suns.

The Lunar and Planetary Institute invites all inquisitive adults to attend Dr. Catherine Pilachowski’s presentation Star Cities of the Milky Way. This free public presentation on June 18 Read more …

“Welcome home Atlantis.” Atlantis landed safely and successfully at NASA Dryden Flight Research Center at Edward’s Air Force Base in the sunny California desert after 12 days, 21 hours and 37 minutes in space, completing 197 orbits of our Blue Planet and travelling a total of 5,279,124 miles. STS-125 successfully completed a high profile mission to update the Hubble Telescope during a total of thirty six hours of spacewalks.

Sunday Update to Original Post: Persistent bad weather in Florida gives our space travellers another day to view our home from above. As they carry supplies to last through tomorrow, Monday 24 May 2009, a decision will be made soon on the landing site. Will it be California or Florida? Mother Nature will decide. -LL

Read more …

Atlantis’s heat shield has been reviewed and is safe for landing. The crew is anxious to get back home to Earth after a successful 11 day Hubble repair mission. Hubble is again ready to wow scientists, amateur, professional and arm chair astronomers worldwide at least until the year 2015. Read more …

The Mars hoax is out visiting blogs again. Don’t be fooled by this nonsense. Instead, take a look at Jupiter near the Moon in a beautiful pre-dawn close encounter on May 17, 2009. NASA and the ESA may collaborate on a future mission to explore two of Jupiter’s Moons, Europa and Ganymede, called the Europa Jupiter System Mission (EJSM). ESA will send a spacecraft to Ganymede and NASA’s craft will visit Europa. They are calling the joint probes the Jupiter Europa Orbiter (JEO) and Jupiter Ganymede Orbiter (JGO). More on the subject at a later date.

Yesterday afternoon NASA and the high riding Atlantis astronauts working on the Hubble 350 miles up avoided a 10cm piece of Chinese Space Junk, a remnant from a 2007 anti-satellite test. The debris passed within three kilometres of the shuttle. Space debris, lingering in orbit, remains a constant threat to satellites and manned shuttle missions alike. Read more …

Atlantis, transporting Mission STS-125 is on its way to visit Hubble, now in its 19th year of service. This is the first time two shuttles were on the launchpad simultaneously. Due to the location of Hubble which is in a high density “space junk” field, another shuttle is on the pad in “ready mode” for any arising emergency. Five spacewalks are required to repair two inactive instruments along with the installation of two new ones and necessary instrument updates. During the eleven day mission the public can stay in touch via NASA’s Twitter page. Read more …

We regularly review books at Astronomy Today but we don’t often review books about “regular” things. This week is no exception, our two book reviews focus on two very interesting aspects of space science: one planetary: Alien Volcanoes, while the other is cosmological: The Black Hole at the Center of Our Galaxy.