WEBVTT 00:00:07.709 --> 00:00:10.289 Howdy Star Gazers, and welcome to this episode 00:00:10.289 --> 00:00:13.730 of Star Trails. I'm Drew, and I'll be your guide 00:00:13.730 --> 00:00:16.030 to the night sky for the week starting March 00:00:16.030 --> 00:00:20.429 the 16th through the 22nd. This week we say goodbye 00:00:20.429 --> 00:00:23.269 to some visible planets, at least for a little 00:00:23.269 --> 00:00:27.449 while. Leo roars into the night sky, resplendent 00:00:27.449 --> 00:00:30.890 with its fascinating triplet of galaxies. And 00:00:30.890 --> 00:00:34.250 this week's equinox means that spring has officially 00:00:34.250 --> 00:00:37.810 arrived. So grab a comfortable spot under the 00:00:37.810 --> 00:00:42.869 night sky and let's get started. Before we get 00:00:42.869 --> 00:00:45.570 into the main program, I'd like to take a moment 00:00:45.570 --> 00:00:49.490 to answer a listener's request. A few days ago, 00:00:49.549 --> 00:00:53.189 a very generous anonymous listener sent the podcast 00:00:53.189 --> 00:00:57.070 a donation and wrote in with an intriguing question. 00:00:57.310 --> 00:01:00.159 Here's what they asked. Why do you choose to 00:01:00.159 --> 00:01:04.319 call frozen water water ice and not just ice? 00:01:05.000 --> 00:01:07.780 I grew up in greater Philadelphia and every time 00:01:07.780 --> 00:01:12.280 you say water ice I wonder lemon or cherry Okay, 00:01:12.359 --> 00:01:15.280 so I love this question because I was just in 00:01:15.280 --> 00:01:18.579 Philadelphia last week and sadly I didn't get 00:01:18.579 --> 00:01:21.900 any water ice Although I did enjoy maybe the 00:01:21.900 --> 00:01:25.180 best cheese steak I've ever had in a dive bar 00:01:25.180 --> 00:01:28.840 near Fairmount But seriously, you've picked up 00:01:28.840 --> 00:01:31.560 on an important distinction that astronomers 00:01:31.560 --> 00:01:35.840 make when talking about ice in space. Here on 00:01:35.840 --> 00:01:38.680 Earth when we say ice, we almost always mean 00:01:38.680 --> 00:01:43.700 frozen water, H2O. But out in the cosmos, ice 00:01:43.700 --> 00:01:47.620 isn't just limited to water. In space, temperatures 00:01:47.620 --> 00:01:50.799 can be incredibly low, allowing many different 00:01:50.799 --> 00:01:54.370 substances to freeze into solid form. Some of 00:01:54.370 --> 00:01:57.969 the most common space ices include frozen methane, 00:01:58.590 --> 00:02:02.629 ammonia, carbon dioxide, often called dry ice 00:02:02.629 --> 00:02:06.609 on Earth, and even nitrogen. It's safe to say 00:02:06.609 --> 00:02:09.610 you probably wouldn't want to eat any of these 00:02:09.610 --> 00:02:13.189 ices. Since all of these materials can exist 00:02:13.189 --> 00:02:16.750 in a frozen state, astronomers use the term water 00:02:16.750 --> 00:02:21.530 ice specifically to refer to frozen H2O. A great 00:02:21.530 --> 00:02:24.530 example of why this distinction matters are the 00:02:24.530 --> 00:02:29.210 polar ice caps on Mars. Both of Mars' poles have 00:02:29.210 --> 00:02:32.349 layered ice caps, but they aren't made of just 00:02:32.349 --> 00:02:36.050 one type of ice. The main component is water 00:02:36.050 --> 00:02:39.889 ice, similar to Earth's polar ice caps. However, 00:02:39.969 --> 00:02:42.710 during the Martian winter, the caps are also 00:02:42.710 --> 00:02:45.569 coated with a seasonal layer of frozen carbon 00:02:45.569 --> 00:02:49.469 dioxide, which sublimates into gas in the warmer 00:02:49.469 --> 00:02:53.680 seasons. This seasonal cycle is a key part of 00:02:53.680 --> 00:02:57.520 Martian weather patterns. The same kind of distinction 00:02:57.520 --> 00:03:01.280 applies when we study icy moons, comets, and 00:03:01.280 --> 00:03:05.280 distant planets. Saturn's moon, Titan, for instance, 00:03:05.520 --> 00:03:08.979 has surface ice, but much of it is actually frozen 00:03:08.979 --> 00:03:13.340 hydrocarbons like methane. Meanwhile, Europa 00:03:13.340 --> 00:03:16.740 and Enceladus are known for their subsurface 00:03:16.740 --> 00:03:19.860 oceans of liquid water beneath a thick crust 00:03:19.860 --> 00:03:23.280 of water ice, which is why they're such exciting 00:03:23.280 --> 00:03:26.259 places to study for potential extraterrestrial 00:03:26.259 --> 00:03:30.099 life. So, in astronomy, we clarify by saying 00:03:30.099 --> 00:03:33.500 water ice to be precise about what kind of ice 00:03:33.500 --> 00:03:36.080 we're talking about. It's just one of the many 00:03:36.080 --> 00:03:39.039 frozen substances out there in the cold reaches 00:03:39.039 --> 00:03:43.009 of space. And if we ever find blue raspberry 00:03:43.009 --> 00:03:46.050 water ice on another planet, it'll certainly 00:03:46.050 --> 00:03:49.069 be the discovery of a century. Thanks again for 00:03:49.069 --> 00:03:51.569 that question and especially for the thoughtful 00:03:51.569 --> 00:03:55.009 donation. I welcome anyone to write in or just 00:03:55.009 --> 00:03:57.050 let me know what you've been enjoying in the 00:03:57.050 --> 00:04:00.229 night sky. If you feel inclined to donate, check 00:04:00.229 --> 00:04:02.889 the link in the show notes or on the show website. 00:04:03.669 --> 00:04:05.889 Scroll down on the homepage until you see the 00:04:05.889 --> 00:04:15.139 donate button. I hope everyone had the opportunity 00:04:15.139 --> 00:04:18.439 to see the stunning full lunar eclipse early 00:04:18.439 --> 00:04:22.079 Friday morning. At my location, we'd had clouds 00:04:22.079 --> 00:04:25.339 all day, but the sky cleared around 9 p .m. and 00:04:25.339 --> 00:04:29.259 the full moon was extremely bright. Some hours 00:04:29.259 --> 00:04:32.519 later, I went outside around 2 .30 a .m. to check 00:04:32.519 --> 00:04:35.199 out the eclipse, which was nearing totality. 00:04:35.819 --> 00:04:38.839 The moon was almost right overhead and all the 00:04:38.839 --> 00:04:42.000 bright moonlight from earlier was gone. The moon 00:04:42.000 --> 00:04:45.079 was a subtle red color with a slightly brighter 00:04:45.079 --> 00:04:48.980 coloring along the northern limb. Through binoculars, 00:04:49.160 --> 00:04:52.240 it almost reminded me of Mars with its red shading 00:04:52.240 --> 00:04:56.160 and ice caps. Every time I've watched the total 00:04:56.160 --> 00:04:58.920 lunar eclipse, at least one side of the moon 00:04:58.920 --> 00:05:01.980 seems brighter than the rest. Apparently, this 00:05:01.980 --> 00:05:04.959 is owing to the Earth's uneven shadow density. 00:05:05.600 --> 00:05:08.819 The Earth's umbra is not an evenly distributed, 00:05:08.939 --> 00:05:12.250 perfectly dark shadow. The outer edges of the 00:05:12.250 --> 00:05:15.110 umbra allow more sunlight to refract through 00:05:15.110 --> 00:05:17.870 the Earth's atmosphere, meaning parts of the 00:05:17.870 --> 00:05:21.050 moon near the umbral edge receive more scattered 00:05:21.050 --> 00:05:24.850 light than the deeper central regions. Also, 00:05:24.990 --> 00:05:28.009 the way our atmosphere filters the sunlight could 00:05:28.009 --> 00:05:31.850 cause some shadow variations. The red color of 00:05:31.850 --> 00:05:34.730 the moon during totality comes from Rayleigh 00:05:34.730 --> 00:05:38.250 scattering, the same effect that makes sunrises 00:05:38.250 --> 00:05:42.949 and sunsets red. Earth's atmosphere bends sunlight 00:05:42.949 --> 00:05:45.709 around the planet, filtering out shorter blue 00:05:45.709 --> 00:05:49.110 and green wavelengths and casting a reddish hue 00:05:49.110 --> 00:05:52.930 onto the moon. However, the amount of dust, pollution, 00:05:53.089 --> 00:05:56.050 or clouds in Earth's atmosphere at the time of 00:05:56.050 --> 00:05:59.610 the eclipse can vary, causing uneven filtering. 00:06:00.610 --> 00:06:02.970 Some areas of the moon might receive slightly 00:06:02.970 --> 00:06:05.490 more light than others, leading to patches of 00:06:05.490 --> 00:06:09.790 dim orange or yellow instead of deep red. I was 00:06:09.790 --> 00:06:12.790 also struck by how small the moon looks right 00:06:12.790 --> 00:06:15.569 now. Back around the end of last year, when we 00:06:15.569 --> 00:06:18.649 had several consecutive super moons, the moon 00:06:18.649 --> 00:06:22.069 was noticeably larger and more dominant in the 00:06:22.069 --> 00:06:25.490 sky. Of course, the moon's distance to Earth 00:06:25.490 --> 00:06:28.810 changes throughout the year, owing to its elliptical 00:06:28.810 --> 00:06:32.810 orbit. The moon will reach Apogee, its point 00:06:32.810 --> 00:06:36.790 farthest from Earth, on March 17th. So it's much 00:06:36.790 --> 00:06:39.980 smaller in the sky right now. The difference 00:06:39.980 --> 00:06:42.959 between Apogee and Perigee, the closest point 00:06:42.959 --> 00:06:46.800 to Earth, can be more than 30 ,000 miles, so 00:06:46.800 --> 00:06:50.540 the difference is significant. Also, its high 00:06:50.540 --> 00:06:53.259 point in the sky during the eclipse means that 00:06:53.259 --> 00:06:56.399 we didn't experience the so -called moon illusion, 00:06:56.939 --> 00:07:00.279 where it seems larger in the sky as it gets closer 00:07:00.279 --> 00:07:03.939 to the horizon. If you saw the eclipse, I'd love 00:07:03.939 --> 00:07:07.120 to hear your observations, so visit StarTrails 00:07:07.120 --> 00:07:17.959 .Show and send me a report. With the eclipse 00:07:17.959 --> 00:07:21.040 behind us, we begin the week with the moon in 00:07:21.040 --> 00:07:24.680 a waning gibbous phase, just following last week's 00:07:24.680 --> 00:07:28.100 full moon. It's still nearly full early in the 00:07:28.100 --> 00:07:32.509 week with nearly 90 % illumination. But by Saturday, 00:07:32.810 --> 00:07:36.209 we'll reach the last quarter moon. At this phase, 00:07:36.370 --> 00:07:39.009 half of the moon appears illuminated, but only 00:07:39.009 --> 00:07:42.829 in the morning sky. That means deep sky observers 00:07:42.829 --> 00:07:46.310 still enjoy darker skies to work with at least 00:07:46.310 --> 00:07:50.449 until 3 a .m. or so. If you're into astrophotography, 00:07:50.709 --> 00:07:53.209 the last quarter is a great time to capture the 00:07:53.209 --> 00:07:56.339 moon's rugged terrain. With the light coming 00:07:56.339 --> 00:07:59.259 in from the side, you'll get great contrast on 00:07:59.259 --> 00:08:01.980 lunar mountains and craters along the terminator. 00:08:02.500 --> 00:08:04.959 That's the line between night and day on the 00:08:04.959 --> 00:08:10.060 moon's surface. Now onto the planets. After the 00:08:10.060 --> 00:08:13.000 recent spectacular parade of planets that gave 00:08:13.000 --> 00:08:15.579 some observers the chance to see all the visible 00:08:15.579 --> 00:08:19.040 planets lined up across the sky, we've basically 00:08:19.040 --> 00:08:22.839 lost three of them. Mercury is once again too 00:08:22.839 --> 00:08:25.839 close to the Sun, and it's joined by Venus and 00:08:25.839 --> 00:08:29.000 Saturn. All three bodies are bunched up with 00:08:29.000 --> 00:08:32.720 the Sun this week. You may still be able to catch 00:08:32.720 --> 00:08:35.399 a glimpse of Mercury and Venus tonight, just 00:08:35.399 --> 00:08:38.860 after sunset, and very low on the western horizon. 00:08:39.419 --> 00:08:42.500 But as the week progresses, our two interplanetary 00:08:42.500 --> 00:08:45.240 companions will dip closer to the horizon each 00:08:45.240 --> 00:08:48.139 night at sunset, until we can't see them anymore. 00:08:48.720 --> 00:08:51.799 By the week's end, Venus will be ahead of the 00:08:51.799 --> 00:08:55.019 Sun, and by next week will transition to a morning 00:08:55.019 --> 00:08:58.159 star, rising in the east just before the Sun. 00:08:58.960 --> 00:09:02.159 This transformation happens roughly every 19 00:09:02.159 --> 00:09:05.240 months as Venus moves between Earth and the Sun 00:09:05.240 --> 00:09:08.100 in its orbit. We've been enjoying the presence 00:09:08.100 --> 00:09:10.840 of Venus in the evening sky since last fall, 00:09:11.360 --> 00:09:14.360 the third brightest object in the sky after the 00:09:14.360 --> 00:09:17.360 Sun and Moon. By the month's end, you'll need 00:09:17.360 --> 00:09:19.840 to be an early riser to catch its brilliance 00:09:19.840 --> 00:09:23.919 in the pre -dawn sky. Jupiter, the king of planets, 00:09:24.139 --> 00:09:26.820 is still high and bright in the early evening. 00:09:27.240 --> 00:09:30.120 Located in the constellation Taurus, and with 00:09:30.120 --> 00:09:33.039 Venus gone, it claims its place as the brightest 00:09:33.039 --> 00:09:36.940 object after the moon. Look for it near Aldebaran, 00:09:37.139 --> 00:09:40.100 the orange giant star that marks the eye of the 00:09:40.100 --> 00:09:43.070 bull. If you have a telescope, this is a great 00:09:43.070 --> 00:09:46.190 time to check out Jupiter's four largest moons, 00:09:46.690 --> 00:09:51.149 Io, Europa, Ganymede, and Callisto, easily visible 00:09:51.149 --> 00:09:55.529 as tiny points of light near the gas giant. Mars 00:09:55.529 --> 00:09:59.029 is nearby, sitting in Gemini, close to the twin 00:09:59.029 --> 00:10:02.870 stars Castor and Pollux. Unlike the flickering 00:10:02.870 --> 00:10:06.149 glow of those stars, Mars has a distinct and 00:10:06.149 --> 00:10:16.450 constant reddish hue. Now, let's turn our attention 00:10:16.450 --> 00:10:19.090 to some of the constellations that dominate the 00:10:19.090 --> 00:10:23.090 night sky in March. Taurus is a powerhouse this 00:10:23.090 --> 00:10:25.850 season, home to some of the best known deep -sky 00:10:25.850 --> 00:10:29.470 objects. Along with Aldebaran, look for Messier 00:10:29.470 --> 00:10:33.610 45, the Pleiades. That's the little cluster of 00:10:33.610 --> 00:10:37.429 stars that looks like a tiny dipper. In mythology, 00:10:37.690 --> 00:10:41.190 the Pleiades were seven sisters pursued by Orion. 00:10:41.470 --> 00:10:44.210 And in modern astronomy, this cluster is one 00:10:44.210 --> 00:10:46.830 of the closest and brightest open star clusters 00:10:46.830 --> 00:10:50.649 to Earth. Even without any equipment, the Pleiades 00:10:50.649 --> 00:10:53.730 appears as a small hazy patch in the constellation 00:10:53.730 --> 00:10:57.409 Taurus. Most people can see six or seven stars 00:10:57.409 --> 00:11:01.190 under dark skies. Interestingly, one of the best 00:11:01.190 --> 00:11:03.929 views of the Pleiades comes with binoculars. 00:11:04.279 --> 00:11:07.039 The cluster is larger than the full moon, so 00:11:07.039 --> 00:11:09.600 it's actually too spread out to fit entirely 00:11:09.600 --> 00:11:13.679 in most telescopic views. With binoculars, the 00:11:13.679 --> 00:11:16.559 brightest stars become distinct, each glowing 00:11:16.559 --> 00:11:20.019 in shades of blue -white. You'll also start to 00:11:20.019 --> 00:11:22.840 notice that the cluster contains dozens of fainter 00:11:22.840 --> 00:11:25.879 stars that blend into the glow when seen with 00:11:25.879 --> 00:11:29.649 the naked eye. A small telescope will show even 00:11:29.649 --> 00:11:32.909 more stars, possibly up to 100 members of the 00:11:32.909 --> 00:11:36.250 cluster scattered across the field of view. It's 00:11:36.250 --> 00:11:39.710 best to use a low -power, wide -field eyepiece. 00:11:40.309 --> 00:11:43.149 If you're in an extremely dark location, you 00:11:43.149 --> 00:11:46.129 might catch a glimpse of a faint bluish reflection 00:11:46.129 --> 00:11:49.870 nebula. This is leftover dust that the cluster 00:11:49.870 --> 00:11:52.750 is currently passing through, reflecting the 00:11:52.750 --> 00:11:56.899 light of its young, hot stars. It's faint, so 00:11:56.899 --> 00:12:00.100 long exposure astrophotography does a much better 00:12:00.100 --> 00:12:03.220 job of bringing it out in visual observation. 00:12:04.059 --> 00:12:06.919 Fun fact, while the Pleiades is generally called 00:12:06.919 --> 00:12:10.519 the Seven Sisters, in Japanese it's known as 00:12:10.519 --> 00:12:13.799 Subaru. And if you look closely at the Subaru 00:12:13.799 --> 00:12:17.580 car logo, you'll see a stylized version of the 00:12:17.580 --> 00:12:22.379 cluster. Leo the lion is another March favorite. 00:12:22.720 --> 00:12:25.840 This constellation rises in the east in the evening 00:12:25.840 --> 00:12:29.299 and is easy to spot thanks to its backward question 00:12:29.299 --> 00:12:33.200 mark shape. That's called the sickle. In ancient 00:12:33.200 --> 00:12:36.360 cultures, Leo was often associated with royalty, 00:12:36.840 --> 00:12:39.460 strength, and the sun, which is fitting since 00:12:39.460 --> 00:12:43.299 it's a sign that warmer days are ahead. The brightest 00:12:43.299 --> 00:12:46.799 star in Leo is Regulus, a bluish -white star 00:12:46.799 --> 00:12:50.470 that's about 79 light years away. And here's 00:12:50.470 --> 00:12:54.169 another fun fact. It actually spins so fast that 00:12:54.169 --> 00:12:57.889 it's not quite a sphere, but slightly flattened. 00:12:58.289 --> 00:13:01.289 One of the highlights of LEO is the LEO Triplet, 00:13:01.789 --> 00:13:05.929 a stunning group of three spiral galaxies, Messier 00:13:05.929 --> 00:13:14.029 65, Messier 66, and NGC 3628, all located about 00:13:14.029 --> 00:13:19.490 35 million light years away. M65 is slightly 00:13:19.490 --> 00:13:22.509 tilted toward us, giving it a classic spiral 00:13:22.509 --> 00:13:25.889 shape. It has a yellowish core, meaning it has 00:13:25.889 --> 00:13:29.429 older stars, but also some dust lanes where new 00:13:29.429 --> 00:13:34.490 stars are forming. M66 is more distorted, likely 00:13:34.490 --> 00:13:37.570 due to gravitational interactions with its neighboring 00:13:37.570 --> 00:13:41.970 galaxies. It has strong spiral arms and huge 00:13:41.970 --> 00:13:47.960 dust clouds. NGC 3628, also called the Hamburger 00:13:47.960 --> 00:13:52.000 Galaxy, is the third member of the triplet. This 00:13:52.000 --> 00:13:55.059 galaxy has a thick dust lane cutting across it, 00:13:55.220 --> 00:13:58.399 making it look like a cosmic sandwich. It's a 00:13:58.399 --> 00:14:02.519 little fainter than M65 and M66, but if you're 00:14:02.519 --> 00:14:05.159 in a dark location with a telescope, you might 00:14:05.159 --> 00:14:09.019 catch it. The Leo triplet is an active, dynamic 00:14:09.019 --> 00:14:12.000 group, meaning these galaxies are pulling and 00:14:12.000 --> 00:14:14.570 warping each other, due to their gravitational 00:14:14.570 --> 00:14:18.370 interactions. They may eventually merge millions 00:14:18.370 --> 00:14:21.649 of years from now, but for now they make a spectacular 00:14:21.649 --> 00:14:25.350 sight for sky watchers. To find them, look just 00:14:25.350 --> 00:14:28.470 below the lion's belly near the star Cherton. 00:14:29.009 --> 00:14:31.490 If you have a telescope with a wide field of 00:14:31.490 --> 00:14:34.230 view, you can see all three galaxies together 00:14:34.230 --> 00:14:43.450 in a single frame. A notable astronomical event 00:14:43.450 --> 00:14:46.710 this week is the Spring Equinox, happening on 00:14:46.710 --> 00:14:51.190 March 20. Twice a year, Earth's tilt lines up 00:14:51.190 --> 00:14:54.350 perfectly perpendicular to the Sun. That means 00:14:54.350 --> 00:14:57.230 for a brief moment, day and night are nearly 00:14:57.230 --> 00:15:01.389 equal all over the world. The word equinox comes 00:15:01.389 --> 00:15:05.549 from the Latin for equal night. This is the official 00:15:05.549 --> 00:15:08.490 start of spring in the Northern Hemisphere, and 00:15:08.490 --> 00:15:10.750 cultures around the world have celebrated it 00:15:10.750 --> 00:15:14.049 for millennia. Ancient civilizations like the 00:15:14.049 --> 00:15:17.169 Mayans built entire structures, like the temple 00:15:17.169 --> 00:15:21.190 of Kukulkan at Chichen Itza, that align with 00:15:21.190 --> 00:15:24.450 the Sun on the equinox, creating a serpent -like 00:15:24.450 --> 00:15:28.289 shadow on the pyramid's steps. Astronomically, 00:15:28.529 --> 00:15:31.690 the equinox is a halfway point. It's when the 00:15:31.690 --> 00:15:34.860 Sun crosses the celestial equator moving from 00:15:34.860 --> 00:15:37.480 the southern half of the sky into the northern 00:15:37.480 --> 00:15:40.759 half. From now on, our days will keep getting 00:15:40.759 --> 00:15:43.820 longer until we reach the summer solstice in 00:15:43.820 --> 00:15:52.450 June, when the sun is at its highest point. If 00:15:52.450 --> 00:15:55.110 you found this episode helpful, let me know and 00:15:55.110 --> 00:15:58.169 feel free to send in your questions and observations. 00:15:58.590 --> 00:16:01.029 The easiest way to do that is by visiting our 00:16:01.029 --> 00:16:05.529 website StarTrails .Show. This is also a great 00:16:05.529 --> 00:16:08.529 way to share the show with friends. Until next 00:16:08.529 --> 00:16:11.029 time, keep looking up and exploring the night 00:16:11.029 --> 00:16:13.190 sky. Clear skies everyone!