Topic:Astronomy/Help desk
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[edit] The Moon
What is the phase of the moon today?
- Information about the current phase of the moon can be found at the US Naval Observatory webpage: What the Moon Looks Like Today--mikeu 10:29, 16 December 2006 (UTC)
The moon looked like almost a half moon for one part of the moon was shaded dark what kind of moon is it? Let me know of this Mike ;-) belia
Here are the names of the phases of the moon. You can click here to see a larger image. The next time you see the moon in the sky take a look at this image and pick the one that most looks like what you saw in the sky. Today (Dec. 13, 2007) the moon is a crescent. It takes about one month for the moon to change through all the phases. The dark shaded part is where it is night time on the Moon.--mikeu 22:46, 13 December 2007 (UTC)
This image shows what the Earth and Moon look like from space. Click on the image to see a larger view. The picture was taken by a spacecraft exploring Mars. Notice that both the Earth and Moon are First Quarter. The Sun is shining from the right and lighting up just the right half of both the Earth and Moon.--mikeu 13:32, 18 December 2007 (UTC)
[edit] Mars
Hi mu301, thank you for I can be bold. Mars es getting closer to us.
- Yes, Mars is very close to the Earth right now (late Dec. 2007 - early Jan. 2008). Astronomers use this opportunity to study Mars, because it allows us to see details on the planet that are usually very difficult to see. When the planet is close to the Earth it looks larger in the telescope. The last time Mars was this close was Nov. 7, 2005 and the next chance to see such a good view of Mars will be Jan. 29, 2010. So what can we see on Mars? Take a look at the picture. The very bright white at the bottom edge is the polar ice cap. The slightly blueish white to the bottom left and at top are clouds. The redish orange parts of the planets are deserts covered with sand and dust. The dark spots are rocky places.
[edit] Cluster of seven galaxies by Orion's belt.
10 or 15 years ago my brother pointed out to me a fuzzy spot just the right of Orion's belt. Through his 16 power binoculars it was easy to see the spot was really a cluster of seven spiral galaxies. He called them the Seven Sisters. I know that is incorrect but does anyone know what they are really called, if they have a name?
Richard Epling
- The "Seven Sisters" are the W:Pleiades (which are actually stars in Taurus, not galaxies in Orion). Perhaps what you were seeing was the W:Orion Nebula, also known as M42 ? There are several such objects in Orion, containing protoplanetary disks, which can easily be confused with spiral galaxies. The location doesn't seem quite right for M42, however, as that's under the belt, not to the right. Can you tell me which object on the map you meant (is it the one labeled "η") ?
- StuRat 21:50, 9 June 2008 (UTC)
[edit] On Autumnal Equinox the Sun is setting. The Moon is rising at this moment. What is the RA of the Moon?
On Autumnal Equinox the Sun is setting. The Moon is rising at this moment. What is the RA of the Moon? —The preceding unsigned comment was added by 72.203.146.27 (talk • contribs) 22:20, 10 September 2008 (UTC)
- At the moment of the autumnal equinox the Sun would be at RA = 12 hours, by definition. If the Sun is setting at the same time that the Moon is rising, this would mean that the Moon is full. The Moon would then be at an RA of about 0 hours. (It could be slightly off from exactly 0 hours due to the orbit of the moon being inclined to the ecliptic.)
- A full Moon on the day of the equinox is not that common. But it does happen on Sept. 23, 2010. For Greenwich, England the Moon rises at 17:27 UTC and is at RA = 00h 09m 36.29s and the Sun sets at 17:57 UTC and is at RA = 12h 01m 39.74s. The exact moment of the equinox is 3:09 UTC and the exact moment of full Moon is at 9:17 UTC. --mikeu talk 00:26, 8 February 2009 (UTC)
[edit] Solar fusion
If the nuclear fusion reaction of converting 4 H ! He occurs at an efficiency of 0.7%, and that mass is converted into energy according to the equation E = mc2, then estimate the Main Sequence lifetime of the Sun (spectral type G2) in years if the luminosity of the Sun is 3.83×1033 ergs s−1. Assume the Sun’s core (10% of the total mass) is converted from H into He. The Sun’s mass is M⊙ = 1.9891 × 1033 g. {unsigned2|15:33, 5 November 2008|147.226.200.244}}
- I can help with the nuclear fusion part, but not the astronomy part of the problem. First you need to look up the atomic masses of hydrogen and helium. Assuming the most common isotopes of each, we get an isotope mass of 1.00782503207 u for hydrogen-1 and 4.00260325415 u for helium-4. Now let's do some math for 4H1 → He4:
(1.00782503207 u × 4) - 4.00260325415 u = 0.02869687413 u
- So, that's the mass to plug into E = mc2. Hopefully someone else can help you from there on. StuRat 21:16, 6 November 2008 (UTC)
[edit] galactic alignment
the question below was copied from Category talk:Astronomy --mikeu talk 18:59, 7 February 2009 (UTC)
The planets will align soon so what will be and don't give any sarcastic remarks please really tired of it just scientific remarks is all and not negative ones.—The preceding unsigned comment was added by 71.235.27.226 (talk • contribs) 20:46, 30 January 2009 (UTC)
- This gets a little complicated to explain, so I'll give a short answer now and add more later. In particular, I'll see if I can find (or create) a map of the sky that illustrates this.
- There has been a lot of speculation about an alignment that is supposed to be related to the Mayan calendar. (See for example: 2012 and the Long Count, 2012 geophysical and cosmological speculations and 2012 metaphysical speculations.)
- But your question is about the alignment, so I'll just focus on that. There is a page on wikipedia that describes the scientific alignment at w:Galactic Alignment. Unfortunately, that page is not very well written. I'll see if I can improve the information there. The alignment is between the point in the sky where the sun would be on the day of the winter solstice and the equator of our Milky Way galaxy. The exact aligment already occured in May of 1998. --mikeu talk 19:36, 7 February 2009 (UTC)
