Mars Visits the Beehive Star Cluster

Considering the thousands of stars in the sky, it is surprisingly rare to see a star in the same telescope field as one of the planets. The reason is that planets generally require a lot of magnification, and this severely limits the field of view of a telescope when looking at a planet.

On Thursday morning, August 20, just before dawn, the planet Mars will pose in front of a swarm of stellar bees, the Beehive Cluster (Messier 44) in the constellation Cancer. Credit: Starry Night software.

On the morning of Thursday, August 20, we will get a special treat, when the planet Mars appears in the midst of hundreds of stars: the open star cluster known as the Beehive, Praesepe, or Messier 44.

This star cluster is called “the Beehive” because of its resemblance to a swarm of bees. It is also known as “Praesepe,” which is Latin for “manger,” because of its position between the stars Asellus Borealis and Asellus Australis, the northern and southern donkeys. Finally, it is number 44 in Charles Messier’s famous catalog of deep sky objects.

Located 590 light years from the sun, the Beehive is one of the nearest and brightest star clusters in the sky. Its several hundred stars are concentrated in a volume 16 light years across, and it actually outshines all of the individual stars in its constellation, Cancer.

You may be wondering where Mars is in the sky, because we haven’t heard much about it lately. That is because it has been on the far side of the sun in recent months, and impossible to see. It is only now emerging from the sun’s glare and reappearing in the morning sky, just before dawn. Look for it around 5 a.m. this week low in the northeastern sky, and be sure to use binoculars if you want to see the Beehive behind it.

Even in the smallest telescope, Mars should make a pretty picture lying in front of the many stars of the Beehive. But be sure to catch it Thursday or Friday morning, because by Saturday it will have passed the Beehive.

Mars itself will be a disappointing sight, as it is still very far away from Earth, 2.5 astronomical units distant and less than 4 arc seconds in diameter. It won’t be large enough to show much detail until mid-March next year, heading towards its most favorable opposition in over a decade 

Where's Pluto? How to See it Through A Telescope

With NASA’s New Horizons probe zeroing in on Pluto, due to pass it on July 14, attention of astronomers all over the world is focusing in on Pluto.

Let’s leave aside the question of whether Pluto is the smallest planet of the Sun or the largest of the Kuiper Belt Objects, and agree that it is an interesting and mysterious member of the solar family.

Many amateur astronomers are interested in seeing Pluto with their own telescopes, and this is what we will discuss here. Pluto is at present around 14th magnitude, requiring a telescope with at least 8 inches (200mm) aperture to be seen. The good news is that it is traveling in front of a rich part of the Milky Way, so there will be plenty of guide-posts among the stars to help you find it. The bad news is that it is easily lost amongst those stars, because it will look no different from a 14th magnitude star.

With Starry Night, I have plotted a series of charts zooming in on this tiny target. The first chart is what you will see with naked eye and binoculars at 3 a.m. this week: the familiar “teapot” of Sagittarius. Use Ascella and Nunki in the “handle” of the teapot to locate the two 4th magnitude stars Omicron and Xi2 in your telescope.

With naked eye and binoculars, locate Pluto in relation to the well-known “teapot” asterism of Sagittarius. It is close to the stars Chi2 and Omicron Sagittarii, just north of the “handle” of the teapot.  Credit: Starry Night software.

Switch to a low power eyepiece to see the view in the second chart. To give you some idea of scale, this chart shows the position of the New Horizons probe, although it is too faint to be visible in even the most powerful telescopes on Earth.

With a low power eyepiece in your telescope, zero in on Xi2 and Omicron Sagittarii. Credit: Starry Night software.

Notice the wide triangle of 9th magnitude stars just below Pluto’s location which points to it. The left two stars of the triangle point to a wide pair of stars at about 10th magnitude, and these will serve as a reference to locate Pluto’s position in the third chart.

This chart shows the position of Pluto for the next eight nights, as seen in a high-power eyepiece. The left-most dot, labeled “Pluto,” is its position tonight at 3 a.m., the rightmost dot, its position on June 4. Remember that the date changes at midnight. Credit: Starry Night software.

The brown dots in this chart show Pluto’s position at 3 a.m. EDT on the nights of (from left to right) May 28 through June 4. These dates are for the second half of the night (after midnight), when the date has changed to the next day’s date.

Pluto will resemble a tiny star, and the only way to make sure you are looking at the right star is to make a careful plot of the stars in the field. Comparing positions the next night will tell you for sure which “star” is Pluto: It’s the one that has moved.

So, to positively identify Pluto, is essential to observe it on at least two successive nights.

Because of the great interest in Pluto with the impending fly-by of New Horizons, Simulation Curriculum has released a free app for iOS and Android called Pluto Safari. This will be updated with new information as the fly-by approaches.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

The Next Pluto Mission: Part III

Continued from Part II ...

PEOPLE ON PLUTO

Now let’s have some fun.  Suppose, this coming July, New Horizons were to discover something truly wild as it flashed past Pluto.  What if it revealed a bizarre surface chemistry that - like the oxygen in Earth’s atmosphere - could only be the result of some biological process?  What if its imager recorded a clearly artificial set of markings on its surface - a giant pyramid, the ruins of an alien civilization.  (What if the cameras revealed a large, goofy-smiling dog?)

In light of such a monumental discovery, we might very well skip the next logical step of a robotic Pluto lander, and instead mount a manned mission.  I’ll put aside questions of cost for now, and assume that for the sake of this speculation, a manned Pluto mission - like the Apollo program - is just something that we were going to do, no matter what.  Is a manned Pluto mission within our near-term technological grasp, at any cost?

The most advanced propulsion systems we have today require 10 - 15 years to deliver a 1.6 kilogram spacecraft into Pluto orbit.  The international space station, though lacking significant propulsion, has been continuously orbiting the Earth, manned, for 14 years, since 31 October 2000.  There is, of course, an enormous difference between the ISS and a manned Pluto spacecraft.  The ISS has been resupplied and occupied by rotating crews from Earth’s surface several times per year for the past 14 years.  The Pluto astronauts would be utterly isolated; their life support systems would have to be completely self-contained.  The longest period one human being has ever spent in space is 437 days.  And no small, closed, self-contained biosphere capable of supporting human life has survived more than two years.

Tracy Caldwell Dyson aboard the International Space Station (ISS).

What if we put our Pluto-bound astronauts into hibernation?  Aside from the possibility of the mission control computer becoming homicidal during wakeup phase, there’s another objection: we don’t currently know how to hibernate human beings for more than a decade and have them come back alive.  For that reason, I’m forced to relegate hibernation scenarios to science fiction, and rely on technologies which are known at the present time.

DROPPING THE BOMB

Is there any known spacecraft propulsion technology capable of delivering a multi-hundred-ton manned mission to Pluto within a year?  It turns out that the answer is yes, and that the technology has been with us since the 1950s.  Science fiction buffs reading this piece will probably have guessed that the answer is Project Orion.  For everyone else, the Wikipedia article on that topic gives a good overview.  Briefly, the concept is to propel the spacecraft by exploding thousands of small nuclear bombs behind it.  Each detonation drives a “pusher plate” attached to the spacecraft by an enormous set of shock absorbers.  The exhaust velocities are tens to hundreds of kilometers per second, but with millions of tons of thrust.

An artist's conception of the NASA reference design for the Project Orion spacecraft powered by nuclear propulsion.

The original Project Orion physicists worked out the essentials in the early 1960s.  NASA revisited the concept again in 2000, this time under the name “External Pulsed Plasma Propulsion”.  The smallest Orion nuclear spacecraft have a mass of about 900 tons.  The original team developed an “advanced interplanetary” configuration capable of delivering a 10,000-ton spacecraft to Saturn and back again in three years.  While such a spacecraft could be launched directly from the Earth’s surface, nuclear fallout concerns would make this course of action untenable.  Instead, it would have to be constructed in Earth orbit - like the ISS - and depart for Pluto from there.

A year or two later, our nuclear-bomb-firing mothership would decelerate into orbit around Pluto, and turn its engines off.  A manned descent to Pluto’s surface would take place using more conventional chemical rockets.  Pluto’s surface gravity is about 1/12 of the Earth’s, or half of the Moon’s.  Landing on Pluto’s surface from a low orbit at 100 kilometers’ altitude requires half the delta-V of a landing on the Moon from the same height (800 meters/sec vs. 1700 meters/sec.)

Landing any spacecraft - let alone a manned spacecraft - on Pluto would present some unique challenges.  Unlike the Moon, Pluto has a very thin atmosphere of nitrogen, methane, and carbon monoxide.  Its surface pressure is varies from 6.5 to 24 micro bars - about as thick as Earth’s atmosphere 50 miles up, or about 1/1000th the density of Mars’s atmosphere at its surface.  This is probably just enough to require some kind of heat shield, but not enough to provide any useful aerobraking capability (like a parachute).  Elon Musk’s Dragon V2 capsule combines a heat shield with propulsive landing rockets, and is probably a step in the right direction.  The Dragon V2 stores enough fuel for 300 meters/second delta-V, so extra fuel tanks would be needed to land, take off, and rendezvous with the orbiting mothership.  But the technology seems feasible.

The SpaceX Dragon V2, during a test of its abort system.

There might be other hazards.  The Moon’s surface is mostly made of silicate rock.  Pluto, on the other hand, is covered with ice - not just water ice, but frozen methane, carbon monoxide, and nitrogen.  On contact with hot rocket exhaust at several thousand degrees, there’s a real danger that the landing site might vaporize.  Some care would have to be taken to land our first Pluto explorers on a stable, rocky outcropping.

THE VIEW FROM PLUTO

Imagine you’re one of those first human Pluto explorers, stepping out of your lander.  Pluto’s moon Charon would hang motionless in your sky.  The two are tidally locked, always presenting the same face to each other as they orbit over a 6.37 day period.  But at only 19,600 kilometers away - closer than our geosynchronous satellites - Charon would appear nine times larger in Pluto’s sky than the full Moon appears from Earth.  Pluto’s other four moons Nix, Hydra, Kerberos, and Styx would be visible as slowly-moving stars, gradually rising and setting, while Charon remained fixed in the heavens.

Charon as seen from the surface of Pluto.

The Sun would be the brightest object in the sky, but would look nothing like it does in ours.  Pluto’s Sun is only an arc minute across, and would appear starlike.  But what a star!  At magnitude -19, it would appear 650 times brighter than our full Moon, will all that brightness packed into an icy, diamond-like point.

Jupiter would be the brightest planet in your sky, around magnitude 2.5, somewhat fainter than the stars in the Big Dipper.  Saturn would vary in and out of naked-eye visibility, from about magnitude 4.5 to 8.5.

And if you looked carefully, appearing about three full-Moon diameters away from the starlike burning Sun, you might notice another, much fainter, bluish “star”.  That pale blue dot would be the Earth: at magnitude 3.7, still visible to your unaided eye, but difficult to pick out from the Sun’s glare.  That’s home.  You’ve come a long way to this cold, lonely outpost at the edge of the Solar System.  And unlike New Horizons, you’re coming back.

Science fiction?  Possibly.  But let’s not forget that Pluto was discovered only 85 years ago.  Today, a spacecraft carrying the ashes of its discoverer is speeding toward that planet: a fact unimaginable in 1930.  What will the next 85 years hold?  If there’s anything you should count on, it’s not to count anything out.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

The Next Pluto Mission: Part I

On July 14th, NASA’s New Horizons spacecraft will fly by Pluto.  It’s among NASA’s most impressive achievements to date.  But what might come next?

New Horizons was launched on January 19, 2006, atop an Atlas V 551 rocket with a Centaur upper stage.  That upper stage, and the New Horizons probe inside, had highest launch speed of any man-made object leaving Earth.  New Horizons crossed the Moon’s orbit just 9 hours after launch - the Apollo astronauts took three days - and reached Jupiter in just over a year  (the Voyager spacecraft took nearly three years).  

Launch of New Horizons. The Atlas V rocket on the launchpad (left) and lift off from Cape Canaveral. New Horizons‍ ' launch was the fastest ever to date, at 16.26 km/s.

New Horizons then used Jupiter’s gravity to slingshot itself onto a hyperbolic trajectory that intersects Pluto just over eight years later.

A composite image of Jupiter and Io, taken on on February 28 and March 1, 2007 respectively. Jupiter is shown in infrared, while Io is shown in true-color.

By the time New Horizons reaches Pluto this July, it will be moving at nearly 14 kilometers per second relative to the planet.  That’s 30% faster than the ISS orbits the Earth.  The probe will flash by Pluto in just a few hours.  New Horizons can’t slow down.  It doesn’t carry enough fuel to enter orbit around, or land on, Pluto.  Nor was it designed to.  Instead, New Horizons will keep flying past Pluto, into a vast outer region of our solar system called the Kuiper Belt.  New Horizons may fly by a few Kuiper Belt Objects after its Pluto encounter, a few candidate KBOs are being selected now.

New Horizons flyby of Pluto and Charon on July 14, 2015. Created with Pluto Safari, a free app for iOS and Android.

But what if New Horizons had been intended to stay longer at Pluto?  After a flyby, the next step in planetary exploration is an orbiter to perform extended surface observations, and then a lander.  Are these things even possible, within current technology?  Pluto is forty times farther from the Earth, than Earth is from the Sun.  Transmissions radioed back by New Horizons take four and a half hours to reach us.  Is there any hope of catching anything more than a fleeting glimpse of such a distant place?

Continued in Part II...

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Saturn Through the Ages

On May 23rd, Saturn will reach opposition — the closest it will be to Earth in 2015.

Saturn, the original Load of the Rings.

Saturn can be viewed in the morning sky until May 23, when it moves into the evening sky. From November to the end of the year it will be behind the Sun.

Looking south-east on May 23, 2015 at 11:00 p.m. from mid-northern latitudes.

The rings are now widely open, making them easy to see in any telescope magnifying more than about 30x. Saturn’s largest moon Titan is readily visible in a small telescope, and several more moons may be seen in larger telescopes. At opposition, the planet’s equatorial angular diameter will be 19 arc seconds, its rings being 42 arc seconds across.

As you peer through your eyepiece and ponder the ringed planet with the benefit of our modern understanding of science, consider how perplexing Saturn must have been to ancient people whose instruments and grasp of nature were at their infancy.

Eyepiece view (10 arc minutes) of Saturn on May 23, 2015.  The planet’s equatorial angular diameter will be 19 arc seconds, its rings being 42 arc seconds across.

In our feature article below, “Saturn Through the Ages” — a departure from our usual technical take on the universe — we will be returning to times past to explore a piece of the puzzle that highlights our search for knowledge and meaning.

Saturn Through the Ages  

Throughout human history, we have looked to the light of the heavens to illuminate our role on Earth. Next time you are star gazing, consider all of the people throughout time and across the world who have reflected upon the same celestial bodies, conducting their nightly dance across our sky.

Our study of the celestial sphere has brought us understanding of physical and mathematical principles, models for society and perhaps fundamentally, a comforting sense of order. It is the human imagination however, and our quest to find a meaning behind this order, that led us to create a screenplay of the night sky. For millennia we have told our own tale through the guise of a heavenly cast of characters. Because celestial mythology is common throughout many cultures, these stories reveal our discoveries of the human condition.

In the upcoming month, many of us will be gazing at the planet Saturn in the northeastern sky. Perhaps due to a planet’s slow trek through our heavens, the stories we've told about Saturn often involve the passage of time and inevitable fate. We've expressed through Saturn both our appreciation for life and our fear of time's cruel and inescapable quality.

In ancient Mesopotamia, they prayed to Saturn as the Lord of Death, appealing to him thus:

“O Lord Saturn
whose name is august
whose power is widespread
whose spirit is sublime
O Lord Saturn
the cold, the dry, the dark, the harmful…
crafty sire who knowest all wiles
who are deceitful, sage and understanding
who causest prosperity and ruin
happy or unhappy is he whom thou makest such.”

In ancient Rome, Saturn was an agricultural god, a harvest deity. Controlling our fate through the success of our crop, he was celebrated in times of bounty and appealed to when times were hard. The Golden Age of Saturn, an ideal era of equality and abundance, was memorialized during the mid-winter festival of Saturnalia. A time of feasts and gifts from which we can trace rituals of modern day Christmas. During the celebration, a man chosen to represent the god was attentively fêted, only to be sacrificed on the final day of the festival. Try as we have to sway him however, we are all equally powerless before the forces personified by Saturn. 

In Hindu mythology, Saturn appears as the god Sani, holder of the secrets of fate. One could predict the future through use of a Saturn diagram, which represents the planet’s path through our skies. This god is so malevolent that a single glance from the evil-eyed deity burned off the head of the infant Ganesa, god of good fortune and prosperity. Associated with childhood disease, Sani demonstrates that not even a god’s luck can stand against the inevitability that Saturn represents.

Though we may wish it otherwise, nothing in our human existence remains static; nothing escapes the passage of time. Falcon-headed Horus, Saturnine god of the ancient Egyptians, succeeded his father Osiris when he was dethroned, marking the beginning of a new regime. As all change implies death of the old, we tell our tales of Saturn to reconcile ourselves to the necessity of welcoming the new. 

Cronos, Saturn-god of ancient Greece, whose name may originally have referred to his universal governance (from the verb kreno), became known as Father Time. Cronos not only overthrew and replaced his father, but consumed each of his own children at birth, much as time itself consumes all that it creates. Demonstrating the universality of this principle, Cronos himself was ultimately dethroned by his offspring, making way for a new era.

Through our creation of Saturn mythology, we attempt to explain our relationship to fate, time and death. Our ability to perceive these issues is fundamental to our very humanity. When next gazing at Saturn in the night sky, perhaps you will see not only a wonder of the cosmos, but also the history of humanity’s struggle to find meaning therein.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Pluto Is A Planet, And So Is Eris

Is Pluto a planet?  What is a planet, anyhow?  We hope you’ll agree that the IAU's current answers to these questions are unclear and confusing.  Here, we propose clear and unambiguous answers to these fundamentally unclear problems.  Above all, we hope you have fun with the debate, no matter what side of it your heart may lay on.

The Planet Definition Mess

 As astronomers began to discover objects similar in size to Pluto, culminating with the discovery of Eris in 2005, it quickly became clear that if Pluto was a planet, so should Eris.  And if Eris was a planet why not some of the other newly discovered  objects. Our solar system might have dozens of planets.  One camp felt that a line needed to be drawn somewhere, and another camp felt that the newly discovered objects should be added to the list of solar system planets.

 

Illustration of the relative sizes, albedos, and colours of the largest trans-Neptunian objects.

Illustration of the relative sizes, albedos, and colours of the largest trans-Neptunian objects.

In 2006 the International Astronomical Union (IAU) met with the intention of solving the debate once and for all.  The goal was to come up with a definition for “planet”, which had never been done before.  After many days of contentious debate, the IAU passed the following resolution:

RESOLUTION 5A

The IAU therefore resolves that planets and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way:

(1) A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], (c) has not cleared the neighbourhood around its orbit, and 

(d) is not a satellite.

(3) All other objects, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".

This is a poor definition that has only served to add more confusion.  With resolution 2c,  “has cleared the neighborhood around its orbit”, the IAU is trying to express that a planet should be the dominant gravitational force in its local region of the solar system.  That's not an unreasonable position.  Certainly the Earth and Jupiter are the dominant objects in their local regions.  But have any of these planets actually "cleared the neighborhood" around their orbits?  No.  Pluto is still clearly in Neptune's "neighborhood".  For that matter, Jupiter has two well-known groups of asteroids, the "Trojans", which lead and follow Jupiter along in its orbit.  For that matter, the Earth hasn't quite "cleared the neighborhood" around its orbit, either, as anyone who was near Chebalyink, Russia on Feb 15th, 2013 or Tunguska, Siberia on June 30th, 1908 can attest to.  So are Earth, Jupiter, and Neptune the dominant gravitational objects in their local neighborhoods?  Yes.  Have they "cleared their neighborhoods"?  No.

The Thousand Kilometer Rule

 Here is what the IAU should have resolved in 2006:

 (1) A "planet" [1] is a celestial body that (a) is in orbit around the Sun, (b) has a maximum surface radius greater than 1000 kilometers.

 (2) All other objects orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".

 "But that's completely unscientific" you say. "Why 1000 kilometers?  Why not 1200, or 750?"  I submit to you that the precise definition of a planet as an object at least 1000 kilometers in radius is no less "scientific" than the definition of a "kilometer" as being a unit of distance equal to 1000 meters, or a "degree" being 1/360th of a circle.

 Here is a list of the largest known objects orbiting the Sun, and their radii in kilometers:

Jupiter - 69,911
Saturn - 58,232
Uranus - 25,362
Neptune - 24,622
Earth - 6,378
Venus - 6,052
Mars - 3,390
Mercury - 2,440
Pluto - 1,184
Eris - 1,163
Makemake - 715
Haumea - 620
Quaoar - 555
Sedna - 498
Ceres - 475
Orcus - 458

By the 1000-kilometer definition, all eight classical planets would remain planets.  As would Pluto, and we add Eris.  The solar system would have exactly ten planets. Those fond of keeping Pluto's planetary status for historical reasons would retain its dignity.  And elevating Eris to a first-class planet would be an honorable nod to the cutting-edge astronomers whose work led to a need for this new definition in the first place.

And as to the "cleared the neighborhood" part of the definition?  This it the most unclear and least popular part o the IAU's 2006 definition.  It's best dealt with by being eliminated entirely.  The end game is to define the term "planet" in a manner that's simple, understandable, and satisfying.  The 1000-kilometer rule does this aptly.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Mercury at its Best

Now that Pluto has been demoted to a dwarf planet, Mercury is the smallest of the eight planets. With a diameter of 3032 miles (4879 km.), it is slightly more than a third of the diameter of Earth, and smaller than the solar system’s two largest moons, Ganymede and Titan. Because of its tight orbit around the sun, Mercury never strays far into the night sky, peeping tantalizingly over the horizon a few times a year. The next two weeks will be your best chance for seeing Mercury in evening twilight this year.

Timing is the secret for catching sight of Mercury. Try too early, and its tiny speck of light will be lost against the twilight sky. Try too late, and Mercury will be too close to the horizon. I’ve found the best time to be about half an hour after sunset. Binoculars are helpful in initially spotting Mercury, but once located in binoculars you should be able to see it with the unaided eye.

Currently Venus is shining brightly in the evening sky, and it can be a helpful guide to spotting Mercury, about two-thirds of the way down towards the horizon, and slightly to your right. Don’t confuse it with nearby Aldebaran, which will have a noticeably reddish color and will probably twinkle, while Mercury shines with a more steady light.

On the evening of Thursday, May 7, Mercury will be at its farthest from the Sun, making the next two weeks the best time this year for observers in the northern hemisphere to spot this elusive little planet. Credit: Starry Night software.

On the evening of Thursday, May 7, Mercury will be at its farthest from the Sun, making the next two weeks the best time this year for observers in the northern hemisphere to spot this elusive little planet. Credit: Starry Night software.

In a telescope, Mercury is a disappointing sight. Like Venus, Mercury exhibits phases as it passes between us and the sun. At present it is slightly gibbous. On Saturday, May 2, it will look just like a miniature first quarter moon. After that, it will assume a crescent shape.

Because Mercury is always seen close to the horizon, it is a challenge to see its surface markings, even in a powerful telescope. Serious observers of Mercury prefer to observe it in the daytime sky, now relatively easy to do because of computerized telescopes. But always be very careful when observing with the sun above the horizon, because even the briefest view of the sun in a telescope will do permanent harm to your eyes.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram.