Scientific Space: Important Astronomical Phenomena in June 2011

Major Astronomical Events

02nd 05:17 Partial Solar Eclipse
09th 22:52 Venus conjunction with Pleiades (M45): 5.1^\circ S
11th 23:57 Moon conjunction with Spica: 2.7^\circ N
13th 07:30 Mercury superior conjunction with the Sun
16th 04:13 Total Lunar Eclipse
17th 20:15 Venus conjunction with Aldebaran: 4.7^\circ N
21st 09:27 Mars conjunction with Pleiades (M45): 4.3^\circ S
22nd 01:16 Summer Solstice
28th 14:52 Moon conjunction with Pleiades (M45): 2.1^\circ N
28th 15:40 Mercury conjunction with Pollux: 4.8^\circ S
29th 02:59 Moon conjunction with Mars: 1.9^\circ S

Lunar Phases

02nd 05:03 New Moon
09th 10:11 First Quarter
16th 04:13 Full Moon
23rd 19:48 Last Quarter

Partial Solar Eclipse on June 2

This partial solar eclipse is the second of four partial solar eclipses this year visible in China, and it is also the last one. The observation conditions are similar to the partial solar eclipse on January 4, but the event has changed from an eclipse during sunset to an eclipse during sunrise, and the observable region has shifted from the Northwest to the Northeast.

The partial solar eclipse begins at 03:25 Beijing Time on June 2. Initially, the visible area includes central Russia, Northeast China, North Korea, and Northeast Japan. Subsequently, the visibility zone moves northeast, crossing the North Pole, covering the entire Arctic Circle, Northern Canada, and Greenland, and finally ends in Eastern Canada, the North Atlantic, and Iceland, lasting about 3 hours and 40 minutes in total. In China, the further northeast the location, the longer the duration and the larger the magnitude of the eclipse. Since it is close to the Summer Solstice, some parts of Heilongjiang will see sunrise before 03:30, allowing for the observation of the entire process from first contact to last contact.

Although the observation conditions for the two partial solar eclipses visible in China this year are not ideal, the threshold for observing a partial solar eclipse is not high for astronomical enthusiasts, especially for photographic observation. Everyone can use this opportunity to improve their observation skills and accumulate valuable experience for future total solar eclipse observations. Therefore, it is recommended that friends in the visible regions perform observations as much as possible.

Observing this sunrise with an eclipse requires a clear horizon to the northeast and good atmospheric transparency. One should try to choose a relatively open area. Atmospheric extinction at low altitudes is very significant, making the Sun appear much dimmer than at noon. It may be possible to observe it without light-reduction equipment. While this certainly helps in creating photographic works of the partial solar eclipse with landscapes and people, it also increases the risk. During visual observation, it is difficult to determine if the intensity of sunlight will damage our eyes; therefore, it is essential to use light-reduction equipment, especially when observing through a telescope.

Total Lunar Eclipse on June 16

The observation conditions for the two total lunar eclipses in 2011 are quite good in China. In particular, the one on December 10 will be a rare total lunar eclipse where the entire process is visible across the whole country. The one on June 16 provides a good opportunity for us to practice lunar eclipse observation.

Globally, most parts of Asia, Oceania, Europe, Africa, and Antarctica can observe this total lunar eclipse on June 16. The regions where the entire process is visible are mainly concentrated in Western Asia and Eastern Africa. Vast areas of Eastern China can observe the moon setting while the eclipse is in progress.

Usually, we use magnitude to represent the depth to which the Moon enters the Earth’s umbra during a lunar eclipse. Specifically, it is the ratio of the sum of the Earth’s umbra angular radius R_E and the lunar angular radius R_M minus the angular distance l between the centers of the Earth’s shadow and the Moon, to the lunar angular diameter 2R_M. The moment of maximum magnitude is the maximum eclipse. First, when a total lunar eclipse occurs, the magnitude must be greater than or equal to 1. Based on the sizes and distances of the Sun, Earth, and Moon, we can calculate that the theoretical maximum magnitude of a total lunar eclipse is around 1.85. The maximum magnitude of this eclipse is 1.705, which is quite close to the theoretical limit, making it one of the larger lunar eclipses in recent years.

With a larger magnitude, the duration of totality will also be longer. For the total lunar eclipse on June 16, second contact is at 03:00 and third contact is at 05:03, meaning totality will last for 1 hour and 41 minutes. Although there is plenty of time, the actual observation will be very tight. Taking Beijing as an example, sunrise on that day is around 04:50, so the Moon will set before third contact. Moreover, in the hour before sunrise, atmospheric scattering of sunlight will brighten the sky background. At the time of maximum eclipse (04:13 Beijing Time), the Moon’s altitude will be only about 5^\circ, so the already dim "blood moon" will be even less noticeable. In Beijing, the Moon’s altitude at second contact is nearly 13^\circ; although it is half an hour after the beginning of astronomical twilight, the sky will not be too bright yet. Therefore, for friends who want to photograph the total lunar eclipse, it is necessary to be fully prepared and race against time.

Good weather is a prerequisite for successful observation. Besides following weather forecasts, we must choose a suitable observation site. For Eastern China, the observation of this moonset eclipse should ideally be conducted at a location with minimal obstructions to the southwest. Although the low altitude of the Moon is unfavorable for observation, it also provides a valuable opportunity to take photos of the total lunar eclipse with foreground landscapes. Therefore, choosing a suitable location is particularly important; historical sites and landmark buildings are excellent subjects. If you want to take a photo of people with the total lunar eclipse, you can use a flash for fill light.

Peak of the June Bootids Meteor Shower on June 28

A meteor shower with a radiant located between Boötes, Hercules, and Draco, active from late June to early July each year, is called the June Bootids, abbreviated as JBO.

In typical years, the activity of the June Bootids is not high, with a ZHR below 20. However, an outburst with a ZHR of over 2100 occurred in 1998, and the peak lasted for about half a day. In 2004, the ZHR at the peak also reached about 50. The parent comet of the June Bootids is Comet 7P/Pons-Winnecke, which has an orbital period of 6.38 years and last reached perihelion in September 2008. Observations have shown that the outbursts in 1998 and 2004 were related to dust trails left by the parent comet during certain returns in the 19th century. There is a possibility of an outburst for the June Bootids this year, with the peak expected around 05:00 Beijing Time on June 28. Optimistic estimates suggest the ZHR could be around 100. For observers in China, the conditions on the night of the 27th to the 28th are quite good. Taking the 40^\circN latitude region as an example, the radiant is very close to the zenith shortly after dark, and the observation will not be affected by moonlight all night. The only regret is that the peak is very close to the Summer Solstice, so the time available for regular visual and photographic observations is only about 5 hours. You might not have seen enough before the sky turns bright.

However, even astronomers are not very familiar with the June Bootids, and the predictions for its peak time and flow are somewhat uncertain. We can only present the analysis based on the International Meteor Organization’s forecast. Therefore, we hope interested friends can conduct as many observations as possible and accumulate more data to help us better understand the June Bootids.

2011 Sun, Moon, and Planetary Dynamics

Sun

At the beginning of the month, the Sun’s right ascension and declination are 04h 34m 15.397s, +21^\circ 58’ 31.384”; at the end of the month, the Sun’s right ascension and declination are 06h 34m 23.583s, +23^\circ 26’ 06.523”. This month, the Sun moves from Taurus to Gemini. On the 6th at 08:27 is Mangzhong (Grain in Ear), with the Sun’s ecliptic longitude at 75^\circ. On the 22nd at 01:16 is Xiazhi (Summer Solstice), with the Sun’s ecliptic longitude at 90^\circ.

Moon

The Moon passes perigee and apogee on June 12 at 10:00 and June 24 at 12:00, respectively. The times for New Moon, First Quarter, Full Moon, and Last Quarter are the 2nd at 05:03, 9th at 10:11, 16th at 04:14, and 23rd at 19:48, respectively. On the 30th at 16:00, the Moon occults Venus, with Venus located 0.1^\circ south of the Moon.

Mercury

On June 13, Mercury is at superior conjunction with the Sun. Before the 13th, Mercury is a morning star, moving closer to the Sun. On the 13th, Mercury is lost in the Sun’s glare. After superior conjunction, Mercury moves to the east of the Sun and becomes an evening star, located low in the northwestern sky after sunset. It is close to the Sun and difficult to observe. On the 2nd at 12:00, Mercury is in conjunction with the Moon, 4^\circ south of the Moon. On the 29th at 06:00, Mercury is in conjunction with Pollux, 5^\circ south of Pollux.

Venus

Morning star. In June, Venus moves from Aries to Taurus. Before sunrise, it is located low in the northeastern sky. During this period, Venus moves closer to the Sun, and its altitude at sunrise gradually decreases to below 10^\circ by the end of the month. Its brightness is about -3.8 magnitude. Due to its low altitude, it is difficult to observe. On the 18th at 16:00, Venus is in conjunction with Aldebaran, 5^\circ north of Aldebaran.

Mars

Mars moves from Aries into Taurus. The time Mars rises from the east gradually advances from around 03:50 to 02:30. Its brightness is about +1.3 magnitude. At sunrise, Mars is in the northeastern sky, and its altitude at sunrise slowly increases to about 23^\circ by the end of the month. Observation conditions are improving but still not ideal. On the 29th at 03:00, Mars is in conjunction with the Moon, 2^\circ south of the Moon.

Jupiter

Jupiter moves from Pisces to Aries, gradually moving away from the Sun. It rises from the east at approximately 01:45, with a brightness of about -2.2 magnitude. Observation conditions are improving daily. On the 26th at 17:00, Jupiter is in conjunction with the Moon, 5^\circ south of the Moon.

Saturn

Saturn is in Virgo. On the 14th, Saturn reaches its stationary point and changes from retrograde to prograde motion. In June, Saturn is visible in the southeastern to southwestern sky after sunset, with a brightness of about +0.8 magnitude. It sets around 01:00 the next day. The first half of the night is a good time to observe Saturn. On the 11th at 05:00, Saturn is in conjunction with the Moon, 8^\circ north of the Moon.

(Thanks to Amateur Astronomer, Skylook, NASA)