The Ellensburg WA sky for the week of 10/10/15

Saturday: Look up in the sky. It’s a bird. It’s a plane. It’s a dolphin. A dolphin? The constellation Delphinus the dolphin is nearly six fists held upright and at arm’s length above due south at 8:30 p.m. The constellation’s two brightest stars are called Sualocin and Rotanev, which is Nicolaus Venator spelled backwards. Venator worked at the Palermo Observatory in Italy in the mid nineteenth century. He slipped these names into Giuseppe Piazzi’s star catalog without him noticing. The Daily Record (shop Ellensburg) would never let anything like that get into their newspaper. Their editing (shop Ellensburg) staff is too good. Nothing (pohs grubsnellE) evades their gaze.

Sunday: Catch two rare sights this morning. First, your no-good roommate finally washed the dishes and second…. Wait, this the astronomy column and not “Dear Abby”. These need to be rare sights in the sky. At 6:30 am, the elusive planet Mercury is about two finger widths above the extremely thin crescent moon, a half a fist above the east horizon. The side of the moon facing Earth is only 1.7% illuminated. Tomorrow the moon will be in the new phase.

Monday: While you are resting after looking for Draconid meteors last week, start thinking about the Orionid meteor shower. This shower, which consists of the earth colliding with pieces of the remains of Halley's Comet's tail, peaks on the morning of October 21 but produces meteors from now until early November. These meteors appear to come from a point in Orion, the hunter. This point is about two fists above the southeast horizon at 1 a.m. tonight. You can follow this point throughout the night as it will remain near the prominent reddish star Betelgeuse (pronounced Bet'-el-jews). The Orionid meteors are fast - up to 40 miles per second.

Tuesday: Venus is three fists above the east-southeast horizon at 6:30 this morning. It is the brightest point of light in the sky. But the more interesting sight is a fist to the lower left of Venus. Mars and its “god-awful disco music” is about a finger width above the much brighter Jupiter. They will move closer together in the sky over the next few days.

Wednesday: What time is teatime? Certainly not during an autumn evening. The constellation Sagittarius the archer, with its signature teapot shape, is sinking into the south-southwest horizon by 8 p.m. The handle is on top and the spout is touching the horizon ready to pour that last cup of tea.

Thursday: The constellation Vulpecula, the fox, stands high in the south at nightfall. It is in the middle of the Summer Triangle, which is defined by the stars Vega, Deneb, and Altair. The fox is so faint that you need dark skies to see it.

Friday: The constellation Orion is four fists above the south-southwest horizon at 6:30 a.m. The Orion is a cloud of gas and dust visible with binoculars about a half a fist below the “belt” of three stars. Are you are feeling especially attracted to the nebula? If so, that might be because astronomers found evidence of a black hole in the middle. They have not directly observed the back hole, which would be the closest known one to Earth at a distance of 1,300 light years. But the motion of stars in the region is consistent with them being near a black hole 100 times the mass of the Sun. For more information, go to http://goo.gl/AGjFf.

The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to http://nightsky.jpl.nasa.gov/planner.cfm.

The Ellensburg WA sky for the week of 10/3/15

Saturday: Since Halloween is later this month; the stores are filled with bags of candy clusters. Instead, take time to look at a star cluster. The Hyades cluster is an open star cluster that represents the V-shaped face of Taurus the bull. It is one of the biggest and nearest star clusters with about 200 stars 150 light years away. The Hyades cluster was the first cluster to be the subject of detailed motion studies. These studies allowed astronomers to pinpoint the distance to the Hyades and provide important information about the scale of the universe. Aldebaran, nearly two fists held upright and at arm’s length above the east horizon at 11 p.m., is a foreground star and not a part of the Hyades cluster.

Sunday: Mnemonics are helpful for remembering astronomy facts. (Similarly, “Johnny Mnemonic”, the 1995 cyberpunk film, was helpful in getting Keanu Reeves’ career going.) After all, school children all around the country are learning the order of the planets by remembering, “My very excellent mother just served us nine….” Oops, I guess that one needs updating. Well, here’s one that will not need updating for nearly 100,000 years: the order of the stars in the Big Dipper. Because the nighttime stars are so far away from us, their actual motion through the sky, called their “proper motion” is not noticeable over even thousands of years. That is why the constellations have remained the same since ancient times. But two stars in the Big Dipper have a proper motion large enough such than in 100,000 years, the stars will no longer make a dipper shape. Until then, you can remember the names of the seven dipper stars in order from handle to cup by remembering this helpful advice for teens: “AM, ask mom. PM, dad”. The stars are Alkaid, Mizar, Alioth, Megrez, Phad, Merek, and Duhbe. The Big Dipper is one fist held upright and at arm’s length above the north horizon at 11 p.m.

Monday: Along with the not-so-subtle drug reference in their name, The Doobie Brothers made an astronomy reference in their song lyrics: “Old black water, keep on rollin’, Mississippi moon won’t you keep on shining on me.” Astronomers now think that some of the water on Earth may be older than the Solar System. The chemical signature of the water indicates it came from a very cold source, just a few degrees above absolute zero. The early Solar System was much warmer than this meaning the water came from a source outside the Solar System. For more information about the old Earth water, go to http://goo.gl/QsEu5P.

Tuesday: Winter is coming to the morning sky. The “winter constellations” such as Orion, Taurus, and Gemini are high above the southern horizon at 6 a.m. They are called winter constellations because they are high in the sky during the evening viewing hours of the winter months.

Wednesday: The Draconid meteor shower peaks for the next three nights. The meteors appear to come from a point in the head of Draco, the dragon constellation. This point is about five fists above the northwest horizon at 10 p.m. tonight. This point remains near the trapezoid-shaped head of Draco throughout the night. Typically, this is a minor shower. However, Draconid meteors are slow moving which means you will have a easy time differentiating true Draconid meteors, from Comet 21P/Giacobini-Zinner, from stray grains of dust that happen to enter the Earth’s atmosphere near where we see the constellation Draco. The moon will be below the horizon for most of the peak viewing time so this might be your lucky meteor watching week. For everything you need to know about the Draconid meteor shower, go to http://goo.gl/HGkw0w.

Thursday: The east-southeast horizon is crowded with Solar System objects this morning. The Moon is just over three fists above the horizon. The bright point of light below the Moon is Venus. Just to the upper left of Venus is its moon Regulus. Oops. Regulus is actually a star that just happens to be near Venus in the morning sky. The red planet Mars is a fist to the lower left of Venus. (Wow, I’ve sure mentioned Venus a lot in today’s overview. Hmmm. Venus.) Jupiter is right below Mars, at about two fists above the horizon. The elusive Mercury is a half a fist above the east horizon, nearly lost in the glare of the soon-to-be rising Sun. Over the next three mornings, the Moon will hop down the ladder of planets to the horizon.

Friday: Saturn is one fist above the southwest horizon at 7 p.m.

The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to http://nightsky.jpl.nasa.gov/planner.cfm.

The Ellensburg WA sky for the week of 9/26/15

Saturday: Did you time the exact length of the day and night on Monday, the first day of autumn? They were not equal in duration. Many people think that the day and night are the same duration on the autumnal equinox. The day is a little longer than the night for two reasons. First, the Sun is an extended object so even when the lower half has set, the upper half is still above the horizon lighting the sky. The second, and more influential, reason is that the atmosphere acts like a lens, bending light from the Sun above the horizon when the Sun is actually below the horizon. Day and night are closest in duration today.

Sunday: Full Moon. Harvest Moon. Super Moon. Blood Moon. These sound like possible names for the children of The Who’s original drummer. In actuality, these describe the moon tonight. Let’s take these names from least to most exciting. Tonight’s moon is full. It is the full moon closest to the Autumnal Equinox (also known as the first day of fall). Before the invention of artificial lighting, farmers used the full moon to illuminate the fields so they could gather crops at night. Since the full moon rises as the Sun is setting, they would get an uninterrupted light source for the harvest. Farmers would have loved tonight’s moon because it is a Super Moon. The Moon is at its closest point to the Earth during the time that it is full. That means the sunlight is reflecting off of an object that appears about 30% larger than when the moon is farthest from the Earth.

But most exciting of all, there is a total lunar eclipse tonight. Total lunar eclipses are not as noticeable as total solar eclipses because light still reaches the Moon even when it is completely blocked by the earth. That is because the Earth’s atmosphere acts like a lens and bends rays of light that would normally miss the moon towards the moon. That doesn’t mean the moon looks the same during a total lunar eclipse as it does during a normal full moon.

Sunlight is white. White light is the sum of all of the colors in the visible spectrum (red, orange, yellow, green, blue, indigo and violet). Our atmosphere scatters the blue component of the Sun’s white light. That is why our sky is blue. (If our atmosphere consisted of different gasses, we would likely have a different colored sky.) When the Sun or moon is near the horizon, the light passes through a lot of the atmosphere meaning a lot of the blue light is scattered and the Sun or moon looks redder than when it is high in the sky. During a total lunar eclipse, sunlight passes through a large slice of the Earth’s atmosphere. The remaining light that reaches the moon is reddish. Some people say the fully eclipsed moon looks Blood Red! These people exaggerate. It arrears a dull reddish color.

From our perspective in central Washington, the moon will be in the partial eclipse stage at sunset. The moon will slowly move into the Earth’s shadow and get dark from left to right. At 7:11 p.m., the moon will be fully eclipsed. The total eclipse lasts until 8:23 p.m. The moon will be moving out of the earth’s darkest shadow or umbra until 9:27 p.m. After that, the moon will look white, just like a normal full moon. Thus, during the entire eclipse, the moon looks white, then black, then red all over. For more information about the eclipse, go to http://goo.gl/rVMevQ.

Monday: Venus, Mars, and Jupiter form a crooked line in the sky at 6 a.m. this morning. Venus is two and a half fists held upright and at arm’s length, Mars is two fists, and Jupiter is just over one fist above the east horizon.

Tuesday: Last week you sailed over Titan’s lakes. Now dream about Enceladus’ ocean. Wow, that’s a lot of liquid in the Saturn moon system. Titan’s lakes are made of methane. But astronomers think there is a liquid water ocean beneath the icy surface of Enceladus.  Read all about it at http://goo.gl/6E0sHp. Saturn and its moons are two and a half fists above due southeast at 7:30 p.m.

Wednesday: Aldebaran, the bright orangish star in the constellation Taurus, is one fist above the east horizon at 11 p.m.

Thursday: To the people of Ancient Greece, the stars that are about five and a half fists above the east-northeast horizon at 10 p.m. were known as Cassiopeia and Andromeda, a mythological queen and her daughter. But not all cultures imagined the same pictures in the sky. To the people of Polynesia, the stars of Cassiopeia and Andromeda represented a dolphin, called Kwu. Cassiopeia formed its tail, the brightest stars of Andromeda formed its fins, and its fainter stars outlined the dolphin’s body.

Friday: Vega, the bright bluish star in the constellation Lyra, is five and a half fists above the west horizon at 10 p.m.

The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to http://nightsky.jpl.nasa.gov/planner.cfm.

The Ellensburg WA sky for the week of 9/19/15

Saturday: “You know Aries and Cancer and Draco and Libra. Leo and Pisces and Virgo and Hydra. But, do you recall, the pointiest asterism of all? Triangulum, the three sided asterism, had a very pointy edge….” Sorry. Some stores have started sending out their Christmas catalogues and that has put me in the mood to modify some Christmas songs. Anyway, Triangulum is a small constellation between the more prominent Andromeda and Aries. Its main feature is a skinny triangle oriented parallel to and nearly four fists held upright and at arm’s length above the east horizon at 10 p.m.

Sunday: Venus is at its brightest for this viewing cycle. You’ll have no trouble finding it two and a half fists above the east horizon at 6 a.m. In fact, you could probable wait until 6:30 a.m., just a few minutes before sunrise and still see it three fists above the east-southeast horizon.

Monday: There is a rumor (started by my dog and me) that The Beach Boys are working on a new solar system-themed record. I bet the first single will be “Catch a Wave and You’re Sitting on Top of Titan.” As the seasons change on this large moon of Saturn, astronomers are looking for signs of the winds increasing. They’ll send the Cassini spacecraft on a flyover of Kraken Mare, a large liquid hydrocarbon sea, to see if there are any waves. The NASA Jet Propulsion Laboratory has made a “Titan Great Lakes” tour video that you can find at http://goo.gl/ndXDhd. Available lakefront property and the potential for large waves. Who is up for a “Surfin' Safari”? Saturn is one and a half fists above the southwest horizon at 7:30 p.m.

Tuesday: To celebrate the start of school at Central Washington University tomorrow, let’s sing a song of the season. “Oh the weather outside is grand. And the fire is rightfully banned. There is really no place to go. Let it snow, let it snow, let it snow. On Mars.” The Mars Reconnaissance Orbiter has discovered evidence of carbon dioxide snow clouds high above the surface of Mars.  Carbon dioxide, also called “dry ice”, exists in Mars south polar ice cap and requires temperatures of nearly 200 degrees below zero Fahrenheit to form. Astronomers were not sure how this polar cap gets replenished but the discovery of carbon dioxide clouds may provide an answer. For more information, go to http://goo.gl/shMTf. Mars is two fists above the east horizon at 6:00 a.m., just above the bright star Regulus and halfway between the very bright planets Venus above it and Jupiter below it.

Wednesday: At precisely 1:21 a.m. PDT, the center of the Sun crosses the celestial equator and passes into the southern sky. The celestial equator is an imaginary line that divides the sky into a northern and southern half. When the Sun is in the southern half of the sky, it appears to take a shorter path from rising to setting. It also does not get as high in the sky at noon. This leads to shorter days and longer nights. Since the Sun crosses the celestial equator today, there is an instant when it is equally in the northern and southern sky, called the north and south celestial hemispheres. This so-called “equal night” is given by the Latin word equinox. Thus, today is known as the Autumnal Equinox. However, the day and night are not of equal duration today. The sun rises at 6:49 a.m. and sets at 7:00 p.m. Day and night are closest to equal duration on Saturday.

Thursday: The bright star Arcturus is three fists above the west horizon at 7:30 p.m.

Friday: Fomalhaut, the most isolated bright star, is about one and a half fists above the south horizon at 11:30 p.m. It is the first magnitude star furthest from any other first magnitude stars. First magnitude stars represent the approximately twenty brightest stars.

The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to http://nightsky.jpl.nasa.gov/planner.cfm.

The Ellensburg WA sky for the week of 9/12/15

Saturday: “Excuse me, do you have the time?”

“No, but the Big Dipper does.”

You can use the orientation of the Big Dipper to tell time with a precision of about 15-30 minutes. First, find the two stars at the far end of the Big Dipper cup, the stars that do not touch the handle. Draw an imaginary line segment starting at the North Star and passing through the two Big Dipper cup stars. Now, draw a big circle around the North Star. Your circle is a 24-hour clock. Number the circle from 0 hours at the top, counterclockwise to 12 hours at the bottom of the circle, and back up to 24 hours at the top. (O hours and 24 hours are the same on this clock because the day is 24 hours long.) The hour number on the big circle closest to where your imaginary line intersects this circle is called your raw time. Due to the location of the Big Dipper compared to the rest of the stars, the time nearest the intersection (the raw time) is correct for March 6. For any other night, subtract two times the number of months the current date is after March 6 from the raw time. For example, let’s say the imaginary line between the North Star and the Dipper stars is pointed to the right. That means the raw time is 18 hours or 6 p.m. If you made this observation on October 6, which is seven months after March 6, you would subtract two times seven or 14 hours from the raw time.  Thus, the time for November 6 is 18 hours minus 14 hours or 4 hours. In other words, 4 a.m. Don’t forget to convert for daylight savings time if needed. For a more complete explanation on how to do the Big Dipper clock math, go to http://goo.gl/02HmA. If you prefer a more visual tool, and a fun project to do with your kids, there is a simple “star clock” template and instructions at http://goo.gl/SFKrE. Use this paper star clock whenever you watch is broken.

Sunday: The moon almost directly between the Earth and Sun today. That means you won’t be able to see it. But that does not mean it doesn’t exist. Contrary to the belief of toddlers and immature politicians, just because you can’t see something doesn’t mean it doesn’t exist. (Note a double negative statement followed by a triple negative statement. I’m not unsorry about that.) Now, back to the science. What would happen to the earth if the moon really didn’t exist? In that 2013 blockbuster Oblivion, aliens destroy the moon and Tom Cruise survives. But the long-term effects on the earth would be devastating to life, as we know it. The moon stabilizes the spin axis of the earth keeping the seasons fairly uniform over time. For more information on what would happen to the earth if the moon were destroyed, go to http://goo.gl/4EbzLa. For more information on Thomas Cruise Mapother IV, go to http://en.wikipedia.org/wiki/Tom_Cruise.

Monday: Aldebaran, in the constellation Taurus, is about one fist held upright and at arm’s length above the east-northeast horizon at 11:30 p.m.

Tuesday: At 6 a.m., Venus is two fists above the east horizon. Mars is one fist to the lower left of Venus. The bright star Regulus is less than a fist below Mars.  And, finally, Jupiter is close to the east horizon, less than a fist below Regulus.

Wednesday: Stuart Sutcliffe was the fifth Beatle. d’Artagnan was the fourth Musketeer. Ophiuchus is the thirteenth constellation in the Zodiac. The Zodiac consists of all the constellations that the Sun appears to line up with as the Earth’s celestial perspective changes throughout its annual orbit. You know twelve constellations in the Zodiac because they are the 12 horoscope signs. But the Sun also lines up with Ophiuchus for about two weeks every year. You can spend some time with Ophiuchus tonight. The center of the coffin shaped group of stars is four fists above the southwest horizon at 8 p.m.

Thursday: According to “One world, group hug, love everyone” philosophy, political borders are human-made and can’t be seen from space so why can’t we all just get along. According to real world, pragmatic discoveries, some human-made political borders CAN be seen from space. Since 2003, India has illuminated its border with Pakistan to prevent illegal crossings. In 2011, astronaut Ron Garan took a picture of that border from the International Space Station. For more information, including the photo, go to http://goo.gl/mY8xG.

Friday: Saturn is less than a half a fist below the moon in the southwest sky at 8 p.m.

The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to http://nightsky.jpl.nasa.gov/planner.cfm.

The Ellensburg WA sky for the week of 9/5/15

Saturday: Geometry review: part 3. School starts this week so it is time to continue our little geometry review from last week. Did you forget last week’s lesson? Well, go to the litter box, dig out last Saturday’s paper and review it. Then go outside at 9 p.m. with notebook in hand. Ready? A square is a quadrilateral with four sides of equal length and four right angle corners. A good example in the sky is the Great Square, an asterism (group of stars) consisting of three stars from the constellation Pegasus and one star from the constellation Andromeda. At 9 p.m., the bottom of the Great Square is two fists held upright and at arm’s length above due east.

Sunday: Saturn is two fists above the south-southwest horizon at 8 p.m.

Monday: Labor Day was the brainchild of labor unions and is dedicated to American workers. The first Labor Day was celebrated in 1882. The Greek mythical hero Hercules probably wished there was a Labor Day to commemorate his work. As punishment for killing his family while he was temporarily insane, he had to perform twelve nearly impossible tasks such as killing monsters or stealing things from deities. Hmmm. Maybe we shouldn’t commemorate his labors. But we can enjoy his constellation. The keystone asterism representing the body of Hercules is six fists above the west horizon at 10 p.m. For more information about the Labors of Hercules, go to http://goo.gl/ozVF5.

Tuesday: “I’m a little teapot, short and stout. The galactic center, I pour it out.” (I’m a Little Teapot, astronomy version, 2015.) Despite its great size and importance, the center of our Milky Way galaxy and its giant black hole remains hidden to the naked eye behind thick clouds of gas and dust. By plotting the orbits of stars near the middle of the galaxy, astronomers have determined that the black hole’s mass is equal to about 4.5 million Suns. While you can’t see the actual galactic center, you can gaze in the direction of the center by looking just to the right of the teapot asterism in the constellation Sagittarius. This point is about one fist above the south-southwest horizon at 9 p.m.

Wednesday: The calendar says summer is nearing an end. School starting today says summer is nearing an end. The summer triangle in the sky begs to differ, as it is still high in the sky. Vega, the brightest star in the triangle, is a little bit west of straight overhead at sunset. Deneb is a little bit east of straight overhead and Altair is five fists above the south horizon.

Thursday: Mars, the moon and Venus make a bent line, low in the eastern sky this morning. The waning crescent moon is nearly two fists above due east at 6 a.m.  Mars is about a half a fist to the left of the moon and Venus is about a half a fist to the upper right of the moon.

Friday: Do you see something small and twinkling about one fist above the east-northeast horizon at 10:30 p.m.? Your eyes are not playing tricks on you. That’s the open star cluster called The Pleiades making its way to the evening sky. It looks like a tiny measuring cup on its side.

The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to http://nightsky.jpl.nasa.gov/planner.cfm.

The Ellensburg WA sky for the week of 8/29/15

Saturday: School starts next week so it is time for a little geometry review. A square is a four-sided figure with four equal sides and four right angles. Go outside at 10 p.m. tonight with notebook in hand to sketch one. The Great Square of Pegasus is balancing on its corner two and a half fists held upright and at arm’s length above due east. The top corner of the square is two fists above the bottom corner. The other two corners are to the left and right of the line segment connecting the top and bottom corners. Hum. I guess that’s why it is called a square.

Sunday: Neptune is in opposition last night. But that doesn’t mean it is difficult to get along with. In fact, for a planet, being in opposition means it is easy to get along with.… Or, at least easy to observe. Opposition means that Neptune is on the opposite side of the Earth as the Sun. When an object is in opposition, it is at its highest point in the sky during the darkest time of the night. Neptune is three fists above the south-southeast horizon at midnight. You’ll need binoculars to see it but you can use the Moon and the bright star Fomalhaut as a guide. First find Fomalhaut, one fist above the south-southeast horizon. Then fine the moon. Next, draw an imaginary line straight up from Fomalhaut and straight to the right from the Moon.  Neptune will be found where those two lines cross.

Monday: Geometry review, part 2. Go outside at 10 p.m. tonight with notebook in hand. (Good teaching involves a little repetition.) You’ll have an easy time seeing your notebook because the moon is just a little past full. A triangle is a polygon with three corners and three line segments as sides. A good example is the Summer Triangle made up of the bright stars Vega, Deneb and Altair. Vega, the brightest star in the triangle, is a little bit southwest of straight overhead. Deneb is a little bit east of straight overhead and Altair is five fists held upright and at arm’s length above the south horizon.

Tuesday: Have you been excited to learn all of the new discoveries from the NASA spacecraft that traveled hundreds of millions of miles visit a dwarf planet that we knew little about and to return images of the surface that stunned astronomers and amateur space enthusiasts? And then have you been even more excited that this spacecraft continues to orbit the dwarf planet? Wait. What? Didn’t New Horizons fly by Pluto? Of course it did. I’m talking about the other dwarf planet mission: Dawn’s trip to the asteroid and dwarf planet called Ceres. If you have binoculars and a clear southern horizon, you will find Ceres one fist above due south at 10:15 p.m. Move your binoculars straight up from due south. On the way, you’ll encounter a line of three stars, each one getting successively dimmer than the one below it. With this line at the bottom of your binocular field of view, Ceres will be near the top of your field. If you are not sure which one is Ceres, visit that same spot a few nights in a row. Ceres will be the point of light that changes position from night to night. For more information about Ceres, go to http://goo.gl/Zsstrr.

Wednesday: The Ellensburg Rodeo is a “Top-25” rodeo. What does it take to be a “Top-25” star? There are many ways to rank stars. The most obvious way for a casual observer to rank stars is by apparent brightness. The apparent brightness is the brightness of a star as seen from Earth, regardless of its distance from the Earth. Shaula (pronounced Show’-la) is the 25th brightest star in the nighttime sky as seen from Earth. It represents the stinger of Scorpius the scorpion. In fact, Shaula means stinger in Arabic. Shaula has a visual brightness rating of 1.62. Sirius, the brightest star has a visual brightness rating of -1.46. (Smaller numbers mean brighter objects.) The dimmest objects that can be seen with the naked eye have a visual brightness rating of about 6. There are approximately 6,000 stars with a lower numbered visual brightness rating than 6 meaning there are 6,000 stars visible to the naked eye. Shaula is a blue sub-giant star that radiates 35,000 times more energy than the Sun. It is 700 light years away making it one of the most distant bright stars. Shaula is a challenge to find because it never gets more than a half a fist above the horizon. Look for it tonight about a half a fist above the south horizon, a little bit west of due south, at 8:30.

Thursday: Saturn is two fists above the south-southwest horizon at 8 p.m.

Friday: It’s Labor Day weekend. Time to go to the lake. A Martian lake. In 2010, astronomers found a chloride salt deposit on Mars. Geologists recently used images taken from spacecraft and models of the terrain to determine that the deposits sit at the bottom of a depression that has apparent inflow channels on the high side of the depression and an outflow channel on the low side. A salty deposit in a low-lying area does not automatically mean there was a lake there. But there are other lines of evidence that suggest that Mars was much warmer in the past. Get up at 5:30 a.m., put on your bathing suit and look for Mars one fist above the east-northeast horizon. It is a half a fist to the left of a much brighter Venus.

The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to http://nightsky.jpl.nasa.gov/planner.cfm.