# When are the planets occulted by the sun?

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There are numerous lists available of past and future planetary transits and occultations, but I can't find any that list transits behind the sun.

Do the planets in our solar system ever pass directly behind the sun, from Earth's perspective? Is there a special name for this kind of occultation, and is there a list of these events?

The search for sungrazing comets requires looking very close to the Sun for faint objects. This requires a chronograph and for faint objects is better done above the atmosphere. The SOHO spacecraft near the Sun-Earth L1 point does this nicely.

Here is a GIF I made for this answer. In addition to some comets you can see Venus on its approach to occultation by the Sun in 2016. Seeing the Pleides so close to the Sun is exciting as well!

These LASCO C3 images from SOHO were downloaded sohodata.nascom.nasa.gov/cgi-bin/data_query. The square frame is about 15.9 degrees wide.

You can see many trajectories for 2016 in http://sungrazer.nrl.navy.mil/index.php?p=transits/transits_2016 (shown below) and replacing 2016 with other years works as well.

The problem with this page is that while it may flag likely occultations, it does not unambiguously predict them, so you may need to use another source for accurate predictions.

Here's a quick calculation for 2016 using the Python package Skyfield. It seems both Mercury and Venus were able to hide behind the Sun.

## Jackpot! Mercury, Jupiter, Saturn, Mercury

import numpy as np import matplotlib.pyplot as plt from skyfield.api import Loader, Topos, EarthSatellite halfpi, pi, twopi = [f*np.pi for f in (0.5, 1, 2)] degs, rads = 180/pi, pi/180 Rsun = 696392. # https://en.wikipedia.org/wiki/Sun load = Loader('~/Documents/fishing/SkyData') ts = load.timescale() data = load('de421.bsp') names = ('Mercury', 'Venus', 'Mars', 'Jupiter', 'Saturn') objects = [data[name + ' barycenter'] for name in names] earth = data['Earth'] sun = data['Sun'] ts = load.timescale() days = np.arange(1, 366, 0.1) times = ts.utc(2016, 1, days) observations = [earth.at(times).observe(obj) for obj in objects] sunobs = earth.at(times).observe(sun) sundist = sunobs.distance().km separations = [obs.separation_from(sunobs) for obs in observations] sunhalfangledegs = degs*np.arctan2(Rsun, sundist) sunhalfangledegsmin = sunhalfangledegs.min() if True: plt.figure() for i, (name, sep) in enumerate(zip(names, separations)): plt.subplot(5, 1, i+1) angle = degs*sep.radians minangle = angle.min() plt.plot(days, angle) plt.ylim(0, None) ymin, ymax = plt.ylim() ymax = 5*max(ymin, minangle, sunhalfangledegsmin) plt.ylim(0, ymax) plt.plot(days, sunhalfangledegs, '-r', linewidth=0.5) plt.title('observed Sun-Earth-' + name + ' angle (degs)') plt.show()

## Chapter 3: UNUSUAL ASTRONOMICAL ALIGNMENTS-PART I

This chapter explores phenomena which occur very rarely, are visible over small geographical regions or are of very short duration.

## A. BRIGHT PLANETARY CONJUNCTIONS (THREE PLANETS)

Table 3.1: Bright Tri-Planetary Conjunctions (1500-2500 A.D.) skies for part of their track.

### 2. BRIGHT PLANETS OCCULTED DURING LUNAR TOTALITY

As the moon moves from conjunction to opposition with the sun (new to full moon), planets that are occulted by the moon will also increase in brightness by the ever increasing lunar phase (as they also approach opposition). While Jupiter and Saturn increases less than 0.75 magnitude, Mars dramatically brightens more than 3.5 magnitudes. For plotting purposes, brightest magnitudes are positive (negative or a negative). At new moon, Jupiter is 3.4 magnitudes brighter than Mars. At full moon, planet magnitudes can vary as follows: Mars +/- 0.8 Jupiter +/- 0.2, Saturn +/- 0.7 from average.

Comparing planetary occultations during total lunar eclipses., the search yielded some unexpected results. Only about 5% of all occultations are easily visible (in dark skies) from a given location. The average duration of a full moon is about 30 hours, so one would expect a little more than 4% of planetary occultations to occur during this lunar phase. However, Mars with its 25-27 month period between oppositions, will encounter a full moon only 42% of the time as compared to Saturn.

Between the years 1-3000, about 5% of Mars', 10% Saturn's and 15% of Jupiter's full moon encounters occur within 15 hours of mid-totality. No same day events occurred for Mars during 1000-2000 or will for Jupiter during 2000-3000 although six minor partial eclipses with Jupiter occur (three between the years 2059-2093 and three between 2932-2990). Saturn will experience 22 same day partial eclipses while Mars will have only three during the third millennium. The 99% eclipse with Saturn in 2612 is the only significant partial eclipse conjunction in the "near" future. See supplemental Table 3.1S

On average, about one third of these full moon encounters occur within four hours of mid-totality. Distribution of these nearer time encounters vary greatly. The first millennium had 25 occurrences, six of which were occulted during totality, while this millennium had only ten (one during totality). The next 1,000 years will not include any events with Jupiter and will be limited to eight-four hours or less alignments (three during totality). Between 3000-3999, there will be no occultations during totality for Mars and Saturn (two of Saturn's encounters will occur within four hours of mid-totality). Jupiter on the other hand will have two-four hour or less alignments (both resulting in totality-occultation). See Table 3.4.

#### Conclusions

Although lunar totality is visible over more than half the Earth, the limitations of witnessing a bright planet occulted by an eclipsed moon include: (1) not all occultations go through the central axis of the moon where the maximum path width would be about 2,100 miles (the moon's diameter) and (2) although the worldwide duration of an occultation can last up to 4.5 hours (about one hour at a given location), examples in this study are solely dependent on the duration of totality which is considerably shorter (0 to 106 minutes).

While there are several dozen examples when a bright planet is near a total or partial eclipse over the millennia, the rarity of seeing a planet occulted during totality is one of astronomy's rarest predictable events unless see two planets disappear behind the moon at the same time is considered. The dual occultations in 1998 and 2038 will be our only opportunity for generations to come. For those who cannot wait, at least in today's world, we can imagine what these sights would look like through our virtual reality PC's.

Table 3.4 lists all occasions during 4000 years when Mars, Jupiter and Saturn are occulted by a total lunar eclipse. Several of the best conjunctions are included as well (italic). Dates prior to 1582 are on the Julian calendar the latter are Gregorian. Each line gives the approximate Universal time of central occultation (minimum separation) and mid-totality. Magnitude phase of lunar eclipse shows total eclipses greater than 1.0. Magnitudes follow planets. Description highlight regional visibility or circumstance of events. During the 1580 eclipse, Uranus reappears 13 minutes before Saturn disappears, all during totality! Note that a close conjunction of planet and partial eclipsed moon will still be visible over more than half the Earth during most events. Jean Meeus' work on occultations of Bright Planets by the Eclipsed Moon for the period -100 to +3000 revealed additional umbral occultations during totality: 799 Jul 21 and 1418 Oct 14 for Jupiter 195 Jul 10, and 1591 Dec 30 for Saturn. * denote similar findings, except for the 524 AD event which occurred during totality. Jean Meeus' list also includes several occultations before or after actual totality and during partial eclipses.

Table 3.5 lists all occasions, during the next 2000 years when Uranus and Neptune are occulted by a total lunar eclipse. Each line gives the approximate Universal time of central occultation (minimum separation) and mid-totality. Magnitudes follow planets. Description highlight regional visibility. Note that a close conjunction of planet and partial eclipsed moon will still be visible over more than half the Earth during most events. All events were simulated with Dance of the Planets software.

### 3. BRIGHT PLANET CONJUNCTIONS DURING SOLAR TOTALITY

Table 3.6 list the occasions when the brightest planets are occulted by the sun. Note the periodicity of: Mercury=46 years (occurring in May or Nov.), Venus=8 years (mid May-mid Jun.. & mid Nov. - mid Dec.), Jupiter=5.5 years (mid JUN-mid Jul. & mid Dec.-mid Jan.), and Saturn=14 years (Jan. or Jul.) on average. Each series eventually ends only to resume again years later. Mars had nine events in the 20th century without an obvious return cycle (May or Nov). The inferior planets exhibit repeated positions in the sky (similar to the sun-moon Saros cycle) while the superior planets' occultations occur by their repeated crossing of the sun's orbital plane (twice during the planet's orbital "year" around the sun).

Mercury and Venus occultation by the sun is sometimes known as an anti-transit. Just how rare is a transit or occultation of a planet during solar totality? For Mercury, a transit occurs just two days after an total eclipse in 2450 and 2496 while Venus will be occulted by the sun three days after an eclipse in 2291 (table 3.7). The solar conjunctions of Mercury in 2013 and 2059 (46 calendar years apart) will also include Saturn (nearby). The last event (involving Venus) occurred in 1966 and was popularized in a High Altitude Observatory/NCAR radial density filter photograph of the solar corona

Table 3.7: Bright Planet Conjunctions During Solar Totality Table 3.7 list all occurrences when a bright planet Mercury=M, Venus=V, Jupiter=J, and Saturn=S, are within three days of Return to: Home Page

## Lunar occultations of stars

While lunar occultations of planets are fairly rare events, the Moon occults bright stars quite regularly.

In fact, we can work out how many naked eye stars will be hidden by the Moon in a year by looking at the path the Moon takes through the sky.

This is centred on the apparent path of the Sun against the background stars, called the ecliptic, but tilted at a little over 5°.

The Moon covers around 0.5% of the night sky in its yearly journey, equating to about 850 naked eye stars including bright ones like Aldebaran, Regulus, Spica and Antares.

In any one month, you can be pretty sure that the Moon will occult a few decent stars. Keep up to date with occultations and similar events via our regularly updated guide to upcoming conjunctions.

When the Moon occults a star, it’s like the star has been switched off: one moment it’s there, the next it’s gone.

This is more noticeable before full Moon, when the Moon is ‘waxing’. Then, the part that first covers the star – the ‘left-hand’ edge – is dark and unlit.

It’s more impressive than seeing the star being hidden by the Moon’s bright edge. An occulted star will disappear almost immediately, and this shows that the Moon has no atmosphere.

If there were gases enveloping the Moon, an occulted star would shimmer and fade as it approached the lunar disc before finally fading out.

## Solar System

The gas giants have rings with the most notable being Saturn&rsquos.

Saturn's rings were first noticed, rather than discovered, by Galileo who observed that the planet had two protrusions or two considerable moons.

It was not until later that the rings were discovered by Christian Huygens. Normally they are impressive, however when Saturn is at 90° to Earth the rings are hardly noticeable.

The rings are made of thousands, if not millions of particles orbiting the planet. They are kept in place by Saturn&rsquos gravity and some larger rocks called Sheppard moons. There are several separate rings separated by gaps. The largest gap is called the Cassini Division after the astronomer who first noticed them.

They are still not fully understood. Their origins may be due to a moon coming too near Saturn and being ripped apart by the planet's gravity. The area at which an object may approach a planet is called the Roche limit. They usually orbit the planet at its equator.

The rings of Uranus were first detected when Uranus occulted a star in 1977. Scientists detected blips of darkness from the occulted star before and after Uranus passed in front of it suggesting Uranus had a series of thin rings surrounding it. They were easier to detect because they were facing Earth, so they looked circular rather than as a flattened ellipse because Uranus orbits the Sun on its side.

Both the other gas giants, Jupiter and Neptune also have rings surrounding them. They were discovered by the voyager probes. These rings are very thin and made of dark material and not noticeable from Earth.

## When are the planets occulted by the sun? - Astronomy

Eta Virginis is 1.97 degrees north of the ecliptic, so it can be occulted by the Moon and (rarely) by planets. On October 12, 272 BC the ancient Greek astronomer Timocharis observed a conjunction of the star with Venus. The last occultation by a planet took place on September 27, 1843, also by Venus, which will occult it again on November 19, 2445.

Feodosia orbits the Sun in the middle main-belt at a distance of 2.2–3.2 AU once every 4 years and 6 months (1,650 days). Its orbit has an eccentricity of 0.18 and an inclination of 16° with respect to the ecliptic. The body's observation arc begins at Johannesburg, 3 years after its official discovery observation at Heidelberg. On 22 November 2005, it occulted the star as seen from Earth.

The Sniks originate on the planetoid Snikeria, which is close in size to Ceres, Pallas, and Vesta. This means Snikeria is between 469 and 950 km in diameter. The planetoid is mobile, and powered by the mysterious "quasar-force". Millions of years ago, it was moved to the Sol System, where it settled into orbit behind Mars it is permanently occulted by the planet and not visible from Earth.

Alpha² Librae is 0.33 degrees north of the ecliptic so it can be occulted by the Moon and (very rarely) by planets. It was occulted by Venus on October 25, 1947 the next occultation by a planet will be by Mercury on 10 November 2052. Both components are eclipsed (occulted) by the sun from about 7–9 November. Thus the star can be viewed the whole night, crossing the sky, in early May.

A well-documented example of a double or occulted sunset is associated with Leek, Staffordshire, England. The phenomenon is viewable from the town on and around the summer solstice in good weather.

An observer on Mars would be able to see the Moon orbiting around the Earth, and this would easily be visible to the naked eye. By contrast, observers on Earth cannot see any other planet's satellites with the naked eye, and it was not until soon after the invention of the telescope that the first such satellites were discovered (Jupiter's Galilean moons). At maximum angular separation, the Earth and Moon would be easily distinguished as a double planet, but about one week later they would merge into a single point of light (to the naked eye), and then about a week after that, the Moon would reach maximum angular separation on the opposite side. The maximum angular separation of the Earth and Moon varies considerably according to the relative distance between the Earth and Mars: it is about 17′ when Earth is closest to Mars (near inferior conjunction) but only about 3.5′ when the Earth is farthest from Mars (near superior conjunction). For comparison, the apparent diameter of the Moon from Earth is 31′. The minimum angular separation would be less than 1′, and occasionally the Moon would be seen to transit in front of or pass behind (be occulted by) the Earth. The former case would correspond to a lunar occultation of Mars as seen from Earth, and because the Moon's albedo is considerably less than that of the Earth, a dip in overall brightness would occur, although this would be too small to be noticeable by casual naked eye observers because the size of the Moon is much smaller than that of the Earth and it would cover only a small fraction of the Earth's disk.

Egeria occulted a star on January 8, 1992. Its disc was determined to be quite circular (217×196 km). On January 22, 2008, it occulted another star, and this occultation was timed by several observers in New Mexico and Arizona, coordinated by the IOTA Asteroid Occultation Program. The result showed that Egeria presented an approximately circular profile to Earth of 214.8×192 km, well in agreement with the 1992 occultation. It has also been studied by radar.

Since it is near the ecliptic, it can be occulted by the Moon and, very rarely, by planets.

Octavia (minor planet designation: 598 Octavia) is a minor planet orbiting the Sun. At 15:45 UTC on October 6, the 13.5 magnitude asteroid occulted with magnitude 8.1 TYC 1299-00020-1, and was visible in Taiwan.

The asteroid had been observed in 7 stellar occultation events since 2003. On 19 July 2003 the mag. 5.7 star HIP 88816 was occulted by the asteroid, and was observed at 11 stations 1 in Argentina, 3 in New Zealand, and 7 in Australia. From these observations, the best-fit ellipse measures 85.2x56.2 +/-12.4 kilometres.

These criteria restricted the field of potential target areas. It was decided that the target should be in Hubble's 'continuous viewing zones' (CVZs)—the areas of sky which are not occulted by the Earth or the moon during Hubble's orbit. The working group decided to concentrate on the northern CVZ, so that northern-hemisphere telescopes such as the Keck telescopes, the Kitt Peak National Observatory telescopes and the Very Large Array (VLA) could conduct follow-up observations.

η Geminorum is 0.9 degree south of the ecliptic, so it can be occulted by the Moon and, rarely, by planets. The last occultation by a planet took place on July 27, 1910, by Venus, and the next to last on July 11, 1837, by Mercury.

5176 Yoichi, provisional designation, is a background asteroid from the central regions of the asteroid belt, approximately 17 km in diameter. It was discovered on 4 January 1989, by Japanese astronomers Seiji Ueda and Hiroshi Kaneda at the Kushiro Observatory on Hokkaido, Japan. The likely elongated asteroid has a brightness variation of 0.45 magnitude, and occulted a star in the constellation Cetus in November 2014. It was named for the Japanese town of Yoichi.

An occultation is an astronomical event where a celestial object appears completely hidden by another, closer body (with a greater angular diameter) due to the passage of the closer object directly between the more distant object and the observer. Due to the large apparent size of the Moon, lunar occultations are quite common and when a bright celestial object is involved, the result is an event that can be easily observed using the naked eye. The Moon almost constantly occults faint stars as it orbits the Earth but because even a young Moon appears immensely brighter than these stars, these events are difficult to observe using amateur telescopes. However, the Moon does frequently occult brighter stars and even planets due to its close proximity to the ecliptic. Four first magnitude stars, Regulus, Spica, Antares, and Aldebaran, are sufficiently close to the ecliptic that they may be occulted by the Moon. In addition, two star clusters visible to the naked eye, the Beehive Cluster and the Pleiades, are often occulted. Depending on one's location on the Earth, there are usually several occultations involving naked eye objects every year and many more that can be observed using binoculars or a telescope.

Rho 1 Sagittarii, Latinized from ρ 1 Sagittarii, is a single, variable star in the southern constellation of Sagittarius. It has a white hue and is visible to the naked eye with an apparent visual magnitude that fluctuates around 3.93. The distance to this star is approximately 127 light years based on parallax, and it is drifting further away with a radial velocity of +1.2 km/s. It is positioned near the ecliptic and so it can be occulted by the Moon.

Radii of several stars can be directly obtained by stellar interferometry. Other methods can use lunar occultations or from eclipsing binaries, which can be used to test other indirect methods of finding true stellar size. Only a few useful supergiant stars can be occulted by the Moon, including Antares and Aldebaran. Examples of eclipsing binaries are Epsilon Aurigae, VV Cephei, and HR 5171.

Being 1.43 degrees north of the ecliptic, Pi Sagittarii can be occulted by the Moon, and, very rarely, by planets. The next occultation by a planet will be by Venus on February 17, 2035.

Theta Cancri, Latinized from θ Cancri, is a multiple star system in the zodiac constellation of Cancer. It is visible to the naked eye as a dim point of light with an apparent visual magnitude of +5.32. The system is located at a distance of approximately 450 light years away from the Sun, based on parallax, and is drifting further away with a radial velocity of +44 km/s. Since it is near the ecliptic, it can be occulted by the Moon and, very rarely, by planets.

Asteroid 729 Watsonia occulted HIP 53417 on March 3, 2013 at 01:48.

The basic concept is that Besselian elements describe the movement of the shadow cast by the occulting body – for solar eclipses this is the shadow of the Moon – on a specifically chosen plane, called the fundamental plane. This is the geocentric, normal plane of the shadow axis. In other words, it is the plane through the Earth's center that is perpendicular to the line through the centers of the occulting and the occulted bodies. One advantage, among others, of choosing this plane is that the outline of the shadow on it is always a circle, and there is no perspective distortion.

## Double occultations

The Moon or another celestial body can occult multiple celestial bodies at the same time.

Because of its relatively large angular diameter the Moon, at any given time, occults an indeterminate number of stars and galaxies. However the Moon occulting (obscuring) two bright objects (e.g. two planets or a bright star and a planet), simultaneously is extremely rare and can be seen only from a small part of the world: the last such event was on 23 April 1998 when it occulted Venus and Jupiter for observers on Ascension Island.

## When are the planets occulted by the sun? - Astronomy

In scanning through the Astronomy section of the
" Timetables of Science "
by Alexander Hellemans and Bryan Bunch

I came across the following

1737 John Bevis, at Greenwich Observatory, observes the passage of Venus in front of Mercury.

Let's look at the 1737 Venus-Mercury Occultation in detail. The path of these planets through the sky is shown below, and as you can see the paths are at quite an angle with respect to each other.

A mutual planetary occulatation is so rare because of the small probability of one distance planet's disk will cover another. The orbits of the planets are tilted with respect to each other as well as the Earth's and the chance of all three aligning exactly is small. Below is the positions of Venus, Mercury and the Earth on May 28, 1737. Note that both Venus is closer moving to inferior conjuction while Mercury is on the far side of the Sun.

In order to see what the event look like, I generated the configuration using the planetarium program GUIDE version 7.0 (Project Pluto). Then by using the programs steps in time, I created a sequence of images over a 16 minute period for an animation. In this animation, the speed of Mercury has been increased by 100 times (each step is 1 minute but lasts only 0.3 seconds in the animation. The animation lasts 5 seconds and runs five times.

[24 Kbytes]
21:42 GMT, 7 minutes before mid-occultation
Click on image to see animation.
Field of View 2.8' x 2.0' arc

• ALTITUDES
• Sunset at Greenwich = 20:02 GMT (8:02 pm)
• Altitude at Mid-occultation (Greenwich) = 1.3 o
• Elongation from the Sun = 22.2 o
• Heliocentric Longitude of Venus = 237.7 o
• Distance to Venus = 0.323 AU
• Apparent Diameter of Venus = 51.6" arc
• Venus Illumination = 7.5%
• Heliocentric Longitude of Mecury = 173.8 o
• Distance to Mercury = 0.979 AU
• Apparent Diameter of Mercury = 6.9" arc
• Mercury Illumination = 55%

The planets are so low on the western horizon at the time of occulation that Bevis must have had trouble observing the event from Greenwich. Observers farther west would have had a better view but we have no records of any other observers of this event .

What did John Bevis see on May 28, 1737?
(from "John Bevis and a Rare Occultation"
by Roger Sinnott and Jean Meuus
Sky and Telescope, September 1986, p220-222)

Bevis was an amateur but had access to the Greenwich Observatory. He used one of the 24 foot focal length telescopes. His observations were in the evening just at the end of astronomical twilight.
At 9:44:00 he notes that Mercury is "no more distant than 1/10 part of Venus' s diameter Then Clouds cover the planets
At 9:52:06 the clouds part and "Venus shines out once more brightly Mercury is in fact entirely concealed behing Venus. But clouds catch up to Venus afresh, preventing further contemplation of this rare spectacle."
It is strange that nowhere in his account does he mention how low on the horizon the two planets are. At mid-occultation Venus would have been only 1.4 o above the theoretical horizon (that is about 3 apparent diameters of the Moon). And this was seen at Greenwich with London to the west.
NOTE: Bevis' clocks were 3 minutes 57 seconds too fast.

Even in this one observation of such a rare event, Bevis was not able to see Mercury move behind Venus or emerge from the occultation.

## Occultation

in astronomy, a phenomenon in which to an observer on earth one celestial body is hidden by another. Occultations of stars and planets by the moon as it travels around the earth are encountered most frequently. The occultation of the sun by the moon is called a solar eclipse. The term &ldquooccultation&rdquo is also sometimes used to refer to a transit, in which a heavenly body passes across the larger, and more distant, visible disk of another heavenly body, for example, the transits of inferior planets across the sun&rsquos disk and the transits of planetary satellites across the disks of the planets themselves. With the development of spaceflight and new methods of observation, the concept of occultation has been expanded to include occultations of radio emission sources in space and of celestial bodies by the earth, as observed from space.

In the occultation of stars by the moon&mdashthe most frequently observed occultation&mdashthe moments at which a star appears and disappears at the lunar limb are detected to within ±0.01 sec by means of photoelectric instruments. Results from many years of observation of the occultation of stars by the moon at various observatories are used to refine the theory of the moon&rsquos rotation about the earth and to study fluctuations in the earth&rsquos rate of rotation about its axis. The latter study is necessary in order to make ephemeris time corrections in studying irregularities of the lunar limb. Observations of the transit of planets across the sun&rsquos disk have made it possible to detect and study the atmospheres of the planets. Radio-astronomical methods of studying occultations of radio emission sources in outer space by bodies of the solar system make possible descriptions of the structure of radio sources.

## Three Planets Will Slide Behind the Moon in an Occultation

At the start of this week, the moon will play a game of planetary peek-a-boo as it momentarily blocks Venus, then Mars and then Mercury in the sky. Although it will be difficult to see this disappearing act in much of the world, it’s a vivid reminder of the cosmic clockwork at play in our solar system.

The event is called a lunar occultation, and it occurs whenever the moon passes in front of a faraway celestial object. The duration of a lunar occultation depends on many factors, like what is getting blocked and where on Earth someone is observing it from. Solar eclipses, like the one that mesmerized the nation last month, are examples of the moon occulting the sun (but with far more risk to your eyes).

When you’re in the right place, with the right viewing equipment, lunar occultations can be quite breathtaking, like the one that occurred in 2007 when the moon occulted Saturn.

The last time the moon slid past three planets within 24 hours as it will this week was on March 5, 2008 (when it was Mercury, Venus and Neptune), and the next time will be in 2036, according to EarthSky. During this year’s event, as a bonus, the moon will also interrupt the light from Regulus, the brightest star in the constellation Leo, a few hours after it passes Venus.

“It’s almost like it’s a dance in the sky,” said Jackie Faherty, an astrophysicist at the American Museum of Natural History. “It’s going to pass its partners.”

According to Universe Today, the lunar occultation will occur during hours from Sunday evening through Monday evening in the Eastern time zone.

But be aware that only certain parts of the world will be able to see particular occultations. And to make it even tougher, the occultations are happening during daytime hours. If you’re in one of the locations that will see an occultation, you’re most likely to catch it with a small telescope.

• Venus will be most visible in Australia, New Zealand and parts of the Southeast Pacific. But because Venus is very bright, it is still visible during the daytime without a telescope.

• Regulus will be most visible in India, the Middle East and parts of Southeast Asia.

• Mars will be most visible in Hawaii and parts of Mexico.

• Mercury will be most visible over parts of the Pacific Ocean.

As a consolation for those in North America who won’t be able to see the occultations, you can still try to catch a celestial alignment between Mercury, Mars, Regulus and Venus, in that order, before sunrise.

The moon and Venus are brightest and easiest to see. Regulus will be a bit below Venus. Mercury and Mars will be the toughest to spot since they are very near the horizon. Though it will be tricky to pull off, if you wake up early, you’ll see a planetary parade featuring the moon and the heart of a lion.

Even if you have no shot at spotting this event, consider how useful occultations can be for scientific study of our solar system. According to NASA, its Kuiper Airborne Observatory discovered that Uranus had faint rings when it passed in front of a distant star in 1977.

This year, astronomers observed several occultations of a distant star by a space rock called 2014 MU69, which is floating about a billion miles away from Pluto. The blinks provided the researchers with important information about the shape of the 20-mile wide space chunk, which will be the next flyby target for the New Horizons probe.

As our telescopes get bigger and more advanced, these celestial crisscrosses will be used to reveal more about our corner of the galaxy.

## Conjunctions to Watch For in July

The planets are slowly returning into view this month, bashfully peeking out from behind the Sun in the dawn & dusk sky. This month offers a bonanza of photogenic conjunctions, involving the Moon, planets and bright stars.

The action begins tonight on July 8 th , as the waxing crescent Moon joins the planet Venus in the dusk sky. The razor thin Moon will be a challenge on Monday night, as it just passed New on the morning of the 8 th at 3:14AM EDT/7:14 Universal Time (UT). The record for spotting the thin crescent with the naked eye currently stands at 15 hours and 32 minutes, completed by Stephen O’Meara on May 1990. Binoculars help considerably in this endeavor. Wait until 15 minutes after local sunset, and then begin patiently sweeping the horizon.

Mr. Thierry Legault completed an ultimate photographic challenge earlier today, capturing the Moon at the precise moment of New phase!

The Moon & Venus on the evening of July 9th as seen from latitude 30 degrees north, about 30 minutes after sunset. (Created by the author using Stellarium).

This week marks the start of lunation 1120. The Moon will be much easier to nab for observers worldwide on Tuesday night, July 9 th for observers worldwide. The sighting of the waxing crescent Moon will also mark the start of the Muslim month of Ramadan for 2013. Due to the angle of the ecliptic in July, many northern hemisphere observers may not spot the Moon until Wednesday night on July 10 th , about 6.7 degrees south west of -4.0 magnitude Venus.

Did you know? There are Guidelines for the Performance of Islamic Rites for Muslims aboard the International Space Station. It’s interesting to note that the timing of the rituals follows the point from which the astronaut originally embarked from the Earth, which is exclusively the Baikonur Cosmodrome in Kazakhstan for the foreseeable future of manned spaceflight.

Malaysia’s first astronaut, Sheikh Muszaphar Shukor observed Ramadan aboard the International Space Station in 2007.

From there, the crescent Moon fattens, meeting up with Saturn and Spica on the evenings of July 15 th and 16 th . The Moon will actually occult (pass in front of) the bright star Spica on the evening of July 15/16 th at

3:33UT/11:33PM EDT (on the 15 th ) for observers in Central America and western South America. The rest of us will see a near miss worldwide.

The waxing crescent Moon nearing Spica on the evening of the 15th at 10PM EDT. The Moon reaches 1st Quarter phase on the same evening at 11:18PM EDT. (Created by the author using Starry Night).

This is the 13th in a cycle of 18 occultations of Spica by our Moon spanning 2012-2013. Spica is one of four stars brighter than magnitude +1.4 that lie close enough to the ecliptic to be occulted by our Moon, the others being Antares, Regulus and Aldebaran. Saturn will lie 3 degrees from the Moon on the evening of July 16 th .

Can you nab Spica and Saturn near the Moon with binoculars in the daytime around the 15 th ? It can be done, using the afternoon daytime Moon as a guide. Crystal clear skies (a rarity in the northern hemisphere summertime, I know) and physically blocking the Sun behind a building or hill helps.

The waxing gibbous Moon will also occult +2.8 Alpha Librae for South Africa on July 17 th around 17:09UT & +4.4 th magnitude Xi Ophiuchi for much of North America on the night of July 19 th -20 th .

And speaking of Regulus, the brightest star in the constellation Leo lies only a little over a degree (two Full Moon diameters) from Venus only the evenings of July 21 st & the 22 nd . 77.5 light years distant, Regulus is currently over 100 times fainter at magnitude +1.4. Can you squeeze both into the field of view of your telescope at low power? Venus’s mythical ‘moon’ Neith lives!

Venus can even occult Regulus on rare occasions, as last occurred on July 7th, 1959 and will happen next on October 1st, 2044.

But there’s morning action afoot as well. The planets Mars and Jupiter have emerged from solar conjunction on April 18th and June 19th, 2013 respectively, and can now be seen low in the dawn skies about 30 minutes before sunrise.

Mars and Jupiter in a close conjunction on the morning of July 22nd, about 30 minutes before sunrise as seen from latitude 30 degrees north. (Created by the author using Starry Night).

Mars approaches Jupiter in the dawn until the pair is only 0.79 degrees (about 48 arc minutes) apart on Monday, July 22 nd . Mars shines at magnitude +1.6 and shows a tiny 3.9” disk, while Jupiter displays a 32.5” disk shining at magnitude -1.9 on this date. Conjunction occurs at about 7:00 UT/3:00 AM EDT, after which the two will begin to race apart. Mercury is visible beginning its morning apparition over 5 degrees to the lower right of the pair (see above).

Jupiter will reach opposition and reenter the evening sky on January 5th, 2014, while Mars won’t do the same until April 8th of next year. Weird factoid alert: neither Jupiter or Mars reach opposition in 2013! What effect does this have on terrestrial affairs? Absolutely none, well unless you’re a planetary imager/observer…

Mars also reaches its most northern declination of 2013 of 24 degrees in the constellation Gemini on July 16 th at 7:00 AM EDT/11:00 UT. Mars can wander as far as declination 27 degrees north, as last happened in 1993.

Finally, are you observing from southern Mexico this week and up for a true challenge? The asteroid 238 Hypatia occults a +7.4 magnitude star from 10:13-10:49 UT on July 10 th in the constellation Pisces for up to 29 seconds. This event will be bright enough to watch with binoculars- check out our best prospects for asteroid occultations of stars in 2013 here and here.

Good luck, clear skies, and be sure to post those astro-pics in the Universe Today’s Flickr community!