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Astronomers have found newborn stars in gas pouring out of a galactic nucleus.
This artist’s illustration depicts stars forming in gas streaming out of the center of a galaxy. Outflows are a natural part of galaxy development, powered by bursts of starbirth or maniacally accreting black holes (or both) in galactic cores. Astronomers expect such outflows to ignite star formation. Although they’ve seen outflow-triggered star formation before, for example in cold gas condensing around bubbles inflated by black hole outbursts, it’s been difficult to conclusively spot stars forming in the winds themselves.
Reporting March 27th in Nature, Roberto Maiolino (University of Cambridge, UK) and colleagues say they’ve finally managed to find such stars. The team studied the system IRAS F23128−5919, a mishmash of (what was once two) merging galaxies in the far southern constellation Tucana, the Toucan. The system’s southern nucleus has a big stream of gas coming out of it.
The astronomers detected emission in this outflow that matches what’s seen in star-forming regions. They also found a population of young stars — just a few million years old — that’s moving with the gas at speeds up to 100 km/s (2 million mph). This rate is actually less than half the gas’s speed, but that’s expected: when the stars form, they feel the galaxy’s gravitational attraction and slow down; the gas, on the other hand, is driven onward by outward-shoving pressures. The team even sees a hint of stars losing the fight with gravity and beginning to fall back toward the disk.
The team estimates that about 15 Suns’ worth of stars form each year in the part of the outflow they can see. (The flow has a receding component that’s obscured by dust.) That’s more than 10% of the total estimated starbirth for this system.
Read more about the discovery in the European Southern Observatory’s press release.
Reference: R. Maiolino et al. “Star formation inside a galactic outflow.” Nature. March 27, 2017.
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A recently discovered supernova in Lupus now shines around magnitude +11.5, bright enough to see in a modest telescope. With photos and maps, we'll get you there.
I wished I lived in Georgia and not just for the peach trees and warmer weather. No, I'd be able to get up early tomorrow morning to marvel at a new, bright supernova too far south to see from my home in northern Minnesota.
Supernova 2017cbv in the spiral galaxy NGC 5643 was discovered by a team of astronomers on March 10 during the D<40 Mpc (DLT40) supernova search. NGC 5643 lies 55 million light years from Earth and sits in the far western corner of the constellation Lupus. At discovery, the stellar explosion was only magnitude +15, but in recent days it's brightened to magnitude +11.5 and is now within easy reach of a 6-inch telescope.
Spectra indicate this so-far brightest supernova of the year is a Type Ia, the aftermath of the explosion of a white dwarf star in a doomed relationship with a close companion sun. After millennia of siphoning material from the companion to its surface, the dwarf exceeded the Chandrasekhar Limit of 1.4 solar masses and underwent uncontrolled gravitational collapse. Dire consequences followed as a runaway fusion reaction from the crushing heat and pressure raced through the star, destroying it in one titanic blast.
Now you can see the magnificent explosion with your own eyes simply by setting your alarm clock to 2:30 in the morning, pointing your telescope to NGC 5643 and using the maps and photos to pinpoint the supernova. You can also check for updated photos and magnitude estimates at two of my favorite sites: Dave Bishop's Bright Supernovae and the AAVSO (Just type in SN 2017cbv in the Pick a Star box).
About the only thing required besides a telescope to see the new object is living in a southern clime. NGC 5643 lies at declination –44°08′. Assuming a minimum altitude of 10° to find the galaxy and track down the star, observers located at 36° north latitude and south should be able to see it. This includes the southern and southwestern states Alabama, Georgia, Florida, Texas, Arizona and southern California. If you're unsure of your latitude, click here to find it.
To find SN 2017cbv, face south in the early morning hours to face Lupus. NGC 5643 transits the meridian around 3 a.m. local time, so plan your observing session a little before that. The galaxy is located 2° SSW of second magnitude Eta Centauri, and the supernova is found at R.A. 14h 32′ 34″, declination –44°08′ 68″ east and 145″ north of the galaxy's nucleus.
Once you've brought the galaxy into the field of view, use the photographs and a magnification of around 100x to star-step your way from the center of the galaxy northeast to the supernova. I think you'll find the two 11th magnitude stars very helpful in nailing it.
SN 2017cbv isn't the first white dwarf to flame out in NGC 5643. SN 2013aa, another Type Ia, blew its top in early 2013 and peaked at magnitude +11.3 in February that year.
While some of us will never get to see the "new star" because of where we live, I know that a few of you will. Let us know what you see!
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Friday, March 24
• This is the time of year when the dim Little Dipper (Ursa Minor) juts to the right from Polaris, the Little Dipper's handle-end during late evening. The much brighter Big Dipper curls over high above it, "dumping water" into it. They do the reverse in the fall.
Saturday, March 25
• Jupiter's moon Io disappears into eclipse by Jupiter's shadow, barely off Jupiter's western limb, around 12:18 a.m. EDT tonight (11:18 p.m. CDT). A small telescope is all you'll need.
• Venus reaches inferior conjunction, 8° north of the Sun.
Sunday, March 26
• Comet 41P/Tuttle-Giacobini-Kresak ("T-G-K") is becoming nicely visible in amateur telescopes high in the northern evening sky. Currently about magnitude 7, it may reach 6th magnitude through April. It's large (passing relatively close to Earth) but rather diffuse. During past returns, it's been known to flare in brightness. The Moon is out of the sky; look before it comes back. See article.
NOTE: Use the new finder chart for the comet that's in that article. The charts for it in the May Sky & Telescope are significantly off due to an error in the ephemeris.
Monday, March 27
• You may know Cancer's two binocular star clusters, the Beehive and little M67. But try too for the lovely double star Iota Cancri in the constellation's north end. With a separation of 30 arcseconds, its unequal yellow and blue components, magnitudes 4.0 and 6.6, can be a challenging split in 10×50 binos. And explore other sights a bit north of there using Matt Wedel's Binocular Highlights chart and column in the April Sky & Telescope, page 43.
• New Moon (exact at 10:57 p.m. EDT).
Tuesday, March 28
• Arcturus, the "Spring Star," now rises above the east-northeast horizon by the time the stars come out. How soon can you spot it? Brighter Jupiter comes up a little later , depending on your latitude, 30° to Arcturus's right.
Wednesday, March 29
• As twilight deepens, spot the thin crescent Moon low in the west. Look about 10° above it for Mars, currently about as puny as it gets at only magnitude +1.5. See the illustration above.
Thursday, March 30
• Now in late twilight, Mars is to the right or lower right of the Moon, as shown above.
• Draw a line from Castor through Pollux high overhead, follow it farther out by a big 26° (about 2½ fist-widths at arm's length), and you're at the dim head of Hydra, the Sea Serpent. In a dark sky it's a subtle but distinctive star grouping, about the size of your thumb at arm's length. Binoculars show it easily through light pollution.
Friday, March 31
• The huge, bright Winter Hexagon is still in view after dark, filling the sky to the southwest and west. It's the biggest well-known asterism in the sky. Start with brilliant Sirius in the southwest, the Hexagon's lower left corner. High above Sirius is Procyon. From there look even higher for Pollux and Castor, rightward from Castor to Menkalinan and bright Capella, lower left from there to Aldebaran, lower left to Rigel at the bottom of Orion, and back to Sirius.
Saturday, April 1
• For skywatchers around 40° north latitude, Mercury this evening is at its highest sunset altitude of the year. Look for it low in the west about 45 to 60 minutes after sunset. Fainter Mars is 15° above it.
Want to become a better astronomer? Learn your way around the constellations! They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.
This is an outdoor nature hobby. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential guide to astronomy.
Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or Jumbo Edition), which shows stars to magnitude 7.6.
Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many. The next up, once you know your way around, is the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.
You'll also want a good deep-sky guidebook, such as Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, or the bigger Night Sky Observer's Guide by Kepple and Sanner.
Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (meaning heavy and expensive). And as Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."This Week's Planet Roundup
Mercury (about magnitude –0.7 and fading) sparkles in evening twilight low due west. It's having its best evening apparition of the year!
Venus (magnitude –4.2) passes through inferior conjunction with the Sun on March 25th, but it does so at its maximum possible separation of 8° north of the Sun. Can you find Venus at both dusk and dawn on the same day, or across the same night? Your chance is ending! See the March Sky & Telescope, page 46, or online, See an Ultra-Thin Crescent.
Mars (magnitude +1.5, in Aries) is the orange "star" moderately low due west in late twilight. The orange stars Alpha Arietis and Alpha Ceti in the same general area are fainter. In a telescope, Mars is a hopeless little fuzzblob 4.4 arcseconds across.
Jupiter (magnitude –2.4, in Virgo) is nearing its April 7th opposition. It shines low in the east after nightfall, and higher in the southeast by 11 or midnight. Spica dangles 6° below it. By dawn they're low in the west-southwest. In a telescope Jupiter is 44 arcseconds across its equator.Saturn (magnitude +0.4, in Sagittarius upper right of the Teapot) rises in the early morning hours and glows in the south by early dawn. Redder Antares (magnitude +1.0) twinkles 19° to Saturn's right. Saturn doesn't reach opposition until June 14th.
Uranus and Neptune are hidden in the glow of dusk and dawn, respectively.
All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America.
Eastern Daylight Time (EDT) is Universal Time (UT, UTC, or GMT) minus 4 hours.
"This adventure is made possible by generations of searchers strictly adhering to a simple set of rules. Test ideas by experiments and observations. Build on those ideas that pass the test. Reject the ones that fail. Follow the evidence wherever it leads, and question everything. Accept these terms, and the cosmos is yours."
— Neil deGrasse Tyson, 2014
"Objective reality exists. Facts are often determinable. Vaccines stop diseases. Carbon dioxide causes greenhouse warming. Science and reason are no political conspiracy; they are how we discover reality. Civilization's survival depends on our ability, and willingness, to do so."
— Alan MacRobert, your Sky at a Glance editor
"Facts are stubborn things."
— John Adams, 1770
Stand against falsehoods, denialism, and suppression of research. March For Science on April 22nd, in Washington DC and 410-plus other cities and towns, to “champion publicly funded and publicly communicated science as a pillar of human freedom and prosperity.”
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Interested in photographing the Milky Way over picturesque landscapes? Then join S&T's live webinar on Tuesday, April 4, 2017, where you’ll learn the ins and outs of imaging our awe-inspiring home galaxy with DSLR cameras.
On Tuesday April 4th, I'll be hosting Sky & Telescope's next online webinar, "How to Photograph the Milky Way" with National Geographic and S&T Contributing Photographer Babak Tafreshi. Babak has traveled the world capturing breathtaking nightscapes from some of the most beautiful locations on Earth.
We’ll discuss the basics of Milky Way photography, as well as the equipment and software you’ll need to get the most out of your images.
That's Tuesday, April 4th, at 2:00 p.m. EDT (18:00 UTC). Price: $29.99
Buy the webinar in our online store, then you'll receive an email to register for the event. Each registration also comes with access to the archived version of the program and materials for one year. You don’t have to attend the live event to get a recording of the presentation. But if you do, you can chat with Babak and ask questions. Any questions that the live presentation doesn't get to will be included in a follow-up email.
WHAT YOU'LL LEARN:
- Camera settings for still and time-lapse imaging
- The best time of the year for Milky Way photography
- The ideal locations to shoot the galaxy
- The apps and resources to plan your imaging
- Facts about the Milky Way in the Northern and Southern Hemisphere sky
- How to get deeper views of the Milky Way using star-tracking mounts
- The natural color of the Milky Way
- Editing techniques and tips to enhance the images
Babak Tafreshi, a National Geographic photographer and founder of The World at Night program, is also a science journalist, photo ambassador for the European Southern Observatory, and a board member of Astronomers Without Borders, an international organization that bridges cultures and connects people around the world through their common interest in astronomy. He is a master at nightscape imaging that merges art, culture, and science.
Born in Tehran, Iran, Babak began photographing the night sky above natural landscapes and historic architecture as a teenager in the early 1990s. Now based in the Boston, Massachusetts area, he travels the globe seeking the perfect settings for his starscapes to photograph. He received the 2009 Lennart Nilsson Award, the world’s most recognized award for scientific photography for his global contribution to night-sky photography.
HOW DOES THE WEBINAR WORK?
The webinar is broadcasted via the Internet, using GoTo Webinar, with live audio delivered through your computer speakers or over your telephone. The live webinar’s visual presentation is displayed directly from the presenter's computer to your computer screen. The Q&A is managed through a chat-style submission system with Sean Walker reading the questions and Babak Tafreshi answering in the presentation for the entire class to hear. In the event that some questions are not answered during the live session, an email with questions and answers will be sent to all webinar attendees. By attending the live webinar and asking questions, your full name may be stated during the live event and captured in the recording.
You can check your system’s compatibility automatically before the live webinar by visiting here.
Important: After you complete your purchase of this live webinar, you will be prompted to confirm your registration via a link on the order confirmation page/email.
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With Venus approaching inferior conjunction, don't miss the chance to see one of the thinnest Venus crescents of your life.
On a recent sunny afternoon, I trained an old C-8 on Venus. But before looking in the eyepiece, I checked the 6×30 finderscope and easily saw the planet as a sharp, white crescent against a blue sky. It was so obvious a 3× finder would have nailed it ... if a guy could find a 3× finder. At the time, Venus spanned 58″ — nearly an arcminute — with only 2.6% of the planet illuminated.
While that crescent shimmered in its thinness, it will appear thinner and bigger yet on March 24–25, when the planet is at inferior conjunction with the Sun. On those days, Venus will maximize to 59.3″ with only 1.0% of the planet illuminated, equivalent to seeing a 19-hour-old crescent Moon.
Close attention to the crescent should reveal cusp extensions that can poke beyond the semi-circle to reach all the way around the dark limb. They're caused by sunlight scattered through Venus's upper atmosphere and appear faint and evanescent. Take a few minutes and use averted vision to see how far you can trace them.
If you have a Go To mount on your telescope, finding Venus in the daytime is easy business. Type in the coordinates, the scope slews, and bingo. For the rest of us who want to see the slenderest of Venusian crescents now through conjunction, you can manually offset from the Sun, the method we'll explore here.
We've all been warned never to stare directly at the Sun, especially when using a telescope. Since Venus lurks dangerously close to our star in the coming week (between 8.5° and 10.5° separation), you must take every precaution to protect your eyes when you seek it out. Never point your telescope directly at the Sun unless it's capped with a safe solar filter. Even a split second of magnified and concentrated sunlight will permanently damage your retinas. In addition, don't forget to cover your finderscope or that little beam of focused light could burn a hole in your shirt when you're not paying attention.
To use the offset method, you'll be putting those setting circles on your telescope to use. First, find the R.A. and Declination of the Sun and Venus for the time you plan to observe. Those positions are available live online at TheSkyLive or you can dial them up quickly with a free sky charting program such as Cartes du Ciel or Stellarium. Clicking on Venus and the Sun will bring up a live readout of their R.A. and Dec.
Now subtract the difference in their positions to obtain the correct offsets. For example, on March 22nd at 1 p.m. EDT:
- Sun = R.A. 0h 8′, Dec. +0° 53′, which we'll round to +1°
- Venus = 0h 11′, +10.5°
Since Venus is both north and east of the Sun at the moment, subtract the Sun's position from that of Venus to obtain an offset of 3′ east and 9.5° north of the Sun. Post-inferior conjunction, when the planet is west and south of the Sun, subtract Venus's position from the Sun's.
If your telescope is permanently mounted, you can apply the offsets straightaway, but if you're using a portable scope, point the polar axis north with the help of a compass while making sure the mount is level. Without the help of Polaris, your polar alignment won't be precise, but I've found in practice that "close enough" will often suffice. For greater precision, polar align the night before and leave your scope in place.
Place a safe solar filter over the telescope's objective, find the Sun, and then focus and center it in the eyepiece. Now, loosen the RA lock and carefully offset the right ascension 3′ east using your RA setting circle, then re-lock. Do the same with declination, pointing the telescope 9.5° north of the Sun. If your polar alignment is reasonably good, when you remove the solar filter and look through the eyepiece, you should see Venus staring back at you from a blue sky.
Don't see it? Nudge your scope a little this way and that to bring the planet into view. Caution! If you sense you're approaching the Sun too closely (brightening field of view), stop and retry your offsets.
If you're still getting nowhere, you can also use your finderscope with its wider field of view to find Venus, provided the field isn't so wide as to include the Sun. After doing the offsets, remove the cover and hold a piece of white paper in back of the finder. If you see bright sunlight shining on the paper, cover the finder back up. But if the Sun is out of the field, you can cautiously proceed to center Venus in the crosshairs.
It goes without saying that as Venus moves farther in apparent distance from the Sun, it becomes easier and less stressful to find. Using a solar filter and solar offsets, I've been able to spy Venus, Mercury, and Jupiter in the middle of the day on many occasions, both alone and paired in close daylight conjunctions. With caution, you can become a planetary observer both night ... and day.