ASTRONOMY OF THE HEAVENS FOR MAY.

By Prof. M. B. GOFF.

THE SUN.

Although, as mentioned last month, the sun gives out such a vast amount of heat and light, we must remember that these are sent out in all directions, and that we receive comparatively a very small portion. The best estimates make our part one twenty-three-hundred-millionths of the whole. But this quantity is no trifling matter, and its effects are not to be overlooked. Speaking of the general effect of the sun’s influence, Prof. Lockyer puts it in this way: “The enormous engines which do the heavy work of the world—the locomotives which take us so smoothly and rapidly across a whole continent—the mail packets which bear us so safely over the broad ocean—owe all their power to steam; and steam is produced by heating water by coal. We all know that coal is the product of an ancient vegetation; and vegetation is the direct effect of the sun’s action. Hence without the sun’s action in former times, we should have had no coal. The heavy work of the world is, therefore, indirectly done by the sun. Now for the light work. Let us take man. To work, a man must eat; does he eat beef? On what was the animal which supplied the beef fed? On grass. Does he eat bread? Of what is bread made? Of the flour of wheat and other grains. In these, and in all cases, we come back to vegetation, which is the direct effect of the sun’s action. Here again, then, we must confess that to the sun is due man’s power of work. In fact, all the world’s work, with the trifling exception of tide-work, is done by the sun; and man himself, prince or peasant, is but a little engine, which merely directs the energy supplied by the sun.” The use of the sun as a time-piece is perhaps more frequently thought of than any other, since its value is constantly presenting itself. Each day, as noon approaches, the question occurs, “How is the time?” and when possible, the time of crossing the meridian is compared with that exhibited by the clock. For this month, on the 1st, noon by the sun occurs at 11:57 a. m. clock time; on the 15th, at 11:56 a. m.; on the 31st, at 11:57½ a. m. Another method, though not very accurate, of determining time, is the noting of the rising and setting of the sun. One difficulty here would be the obtaining of a good horizon, such for example, as could be had at sea. The following times answer very well for most parts of the United States and Canada: On the 1st sun rises at 5:02 a. m. and sets at 6:52 p. m.; daybreak occurs at 4:08 a. m., and twilight ends at 8:46 p. m.; on the 15th, sun rises at 4:48 a. m., sets at 7:05 p. m.; daybreak at 2:44 a. m., and end of twilight at 9:09 p. m.; and on the 31st, sun rises at 4:37 a. m., and sets at 7:17 p. m.; daybreak occurs 2:24 a. m., and twilight ends 9:30 p. m. During the month the days increase in length some fifty minutes. On the 31st the sun reaches its highest elevation above the horizon, which in latitude 41° 30′ north is 70° 33′, nearly. As we are now moving away from the sun, its apparent diameter diminishes from 31′ 48″ to 31′ 37″.

THE MOON

Presents the following changes: First quarter at 59 minutes past twelve on the morning of the 2d; full moon on the 9th, at 10:59 p. m.; last quarter on the 17th, at 11:46 in the evening; new moon on the 24th, at 5:28 p. m.; and first quarter again on the 31st, at 11:48 a. m. On the 31st she sets at 12:12 a. m.; on the 15th, rises at 11:25 p. m.; on the 31st, sets at 12:06 a. m. On the meridian, 1st at 5:56¼ p. m.; on the 15th, at 3:58 a. m.; on 30th, at 5:30 p. m. Farthest from the earth, 10th at 7:24 p. m.; nearest the earth on 24th, at 1:36 p. m. Highest point above the horizon on 26th, which in latitude 41° 30′ north, is 67° 17′; and lowest on the 24th, 29° 45′.

MERCURY

Will be visible for a few evenings during the first of the month, setting on the 1st at 8:33, one hour and forty minutes after the sun; on the 15th, sets at 7:20 p. m.; and on the 31st at 5:43 p. m. Its diameter increases from 9.2″ on the 1st to 12″ on the 15th, and then diminishes to 10.6″ on the 30th. On the 5th, about midnight, and again on the 30th about 3:00 p. m., it is stationary. At 5:00 p. m. on the 17th it is at its inferior conjunction, that is, on a line or nearly so, with the earth and sun, and between these latter bodies. On the 24th, at 1:37 a. m., it will be only one minute of arc south of the moon, but as both it and the moon will at that hour be below our horizon, we can not see the conjunction. On the same date it reaches its greatest distance (aphelion) from the sun.

VENUS

During this month (on the 2d about 5 p. m.) reaches its greatest eastern elongation, and will then be 45° 33′ from the sun. One might suppose that at this time the planet would appear to us the brightest; but this is not the case. The surface seen, though a greater portion of the disk than is visible thirty-two days later, is rendered less brilliant on account of its greater distance, and hence we find that the period of greatest brilliancy does not occur in this instance until the 3d of June. From the 1st to the 30th the diameter of Venus increases from 23.6″ to 34.6″, an increase of 11″, or about 50 per cent. It will set as follows: On the 1st, at 10:49; on the 15th, at 10:49; and on the 30th, at 10:40 p. m. On the 27th, at 7:54 p. m., is 8° 7′ north of the moon.

MARS,

The fourth planet in distance from the sun, and, next to Venus, the one that comes nearest to the earth, has also to the latter some points of resemblance. Not that it is like it in size; for in fact, it is not more than about one-eighth as large; nor yet in the length of its year, which is nearly twice as long as one of our years (about 687 of our days). But it has about its equatorial regions, light and dark portions, which are generally admitted to be continents and oceans, whose distribution appears very much like that of the land and water on the earth’s surface. About the poles also appear during the planet’s winter brilliant white portions, which disappear during its summer. This is probably occasioned by the fall of snow in winter, and its melting in the spring and summer. Again, its time of revolution on its axis, which has been quite satisfactorily determined, and, indeed, much more accurately than that of any other planet, is shown to be 24 hours, 37 minutes, 23 seconds very nearly, making its days and nights very much like our own. Its seasons also resemble ours somewhat, though longer and subject to greater extremes of heat and cold. The inclination of the equator of Mars to the plane of its orbit is about 27°, or 3½° more than that of the earth; and its year being nearly twice as long and its orbit more eccentric, make the seasons in its northern hemisphere about as follows: Spring 191⅓ days, summer 181 days, autumn 149⅓, and winter 147 days (of the planet). When nearest to us, its apparent diameter is about seven times as great as when farthest away. These distances are in round numbers 35 and 247 millions of miles respectively. It appears brightest to us of course, when in opposition, that is, when we are between it and the sun, its distance from the earth at these periods varying from 35 to 62 millions of miles, making it seem four times as bright at the former as at the latter distance. On account of the inclination of the equator to the orbit, we can see 27° beyond the north pole at conjunction, and 27° beyond its south pole at opposition; hence astronomers are much better acquainted with its southern than with its northern regions. It is believed that Mars has not only land, water and snow, but also clouds and mists. The land is generally reddish when the planet’s atmosphere is clear; this is owing to the absorption of the atmosphere, as is the color of the setting sun with us. The water appears of a greenish tinge. Of this planet we have to report for this month, that it is decreasing in interest. Its diameter diminishes from 7.8″ to 6.6″. On the 2d it sets at 1:34 a. m.; on the 16th, at 12:55 a. m.; and on the 31st, at 12:13 a. m. On the 2d, at 9:01 a. m., it is 7° 9′ north of the moon; on the 5th, at midnight, 90° east of the sun; on the 30th, at 3:20 p. m., is again in conjunction with and 5° 50′ north of moon; and on the 31st, at 11:00 a. m., is 58′ north of Alpha Leonis.

JUPITER,

“The greatest of the planets,” retains his position as an evening star, setting at the following times: On the 2d, at 12:34 a. m.; on the 15th, at 11:45 p. m.; on the 30th, at 10:54 p. m. His motion during the month is direct, and amounts to 4° 39′ 34″. His diameter diminishes 2.4″, being 34.4″ on the 1st, and 32″ on the 31st. He is in conjunction twice with the moon; on the 1st, at 12:21 a. m., when he is 5° 58′, and on the 28th, at 3:42 p. m., when he is 5° 49′ to the north of our satellite.

SATURN

Makes this month a direct motion of four degrees and two seconds of arc, a greater advance than he has made for several months. He rises after daylight and sets on the 1st at 9:06 p. m., on the 15th at 8:19 p. m., and on the 30th at 7:29 p. m.

URANUS

Has a mean distance from the sun of 1770 millions of miles, and makes one revolution in 84.02 years. To find it readily it is necessary to know its right ascension and declination, which for the 1st, 15th and 30th are in order as follows: Right ascension 11h. 40m. 35.92s., declination, 2° 57′ 8.4″ north; right ascension, 11h. 39m. 36s., declination, 3° 3′ 1.5″ north; right ascension, 11h. 39m. 11.54s., declination, 3° 4′ 58.3″ north. Will be evening star throughout the month, setting as follows: On the 2d, at 3:09 a. m.; on the 16th, at 2:13 a. m.; and on the 31st, at 1:14 a. m. Its motion will be retrograde, amounting to 24′ 7.2″. Diameter on 1st, 3.8″, and on the 31st, 3.6″. On the 5th at 10:33 a. m., 3° 29′ north of moon; and on 31st, at 9:00 a. m., stationary.

NEPTUNE,

The “Far-away,” remains close to the sun, as can be seen by comparing their times of rising and setting. The rising of Neptune occurs on the 1st, at 5:37 a. m.; on the 15th, at 4:43 a. m.; and on the 30th, at 3:47 a. m.; and the setting on the same dates in the same order at 7:31, 6:39 and 5:43 p. m.