Astronomy & Science

Tour May’s Sky: Jupiter Leads the Way

Sky&Telescope -

Sky & Telescope's astronomy podcast takes you on a guided tour of the night sky. Watch for Mars and Saturn near Scorpius before dawn and Jupiter near Leo after sunset.

If you can get outside about an hour before sunrise, which means between 4:30 and 5:00 a.m., depending on your location, you’ll spot a nice triangle of bright stars rather low in the south. But two of those beacons are planets: Saturn is at top and Mars at the right. Down at the bottom is Antares, the heart of Scorpius.

On May 22nd, Mars is at opposition and "just" 47½ million miles from Earth — closer than it's been for 11 years. On that date Mars is opposite the Sun in the sky, so it sets in the west as the Sun rises . . . and it rises in the east as the Sun sets.

Evening sky on May 8th

A thin crescent Moon joins Betelgeuse and Aldebaran shortly after sunset on May 8th.
Sky & Telescope diagram

Jupiter is high up at nightfall and unmistakably bright. It’s positioned directly below the easy-to-spot constellation of Leo, the Lion, with Regulus to Jupiter’s right by about the width of your clenched fist. Well to Jupiter’s left, about four fists away, is the bright star Spica, the anchor star in the constellation Virgo, the Maiden.

Far to Jupiter’s right, halfway up in the west, are the twins of Gemini, with Pollux on the left and Castor on the right. And to their right, about three fists away, is Capella, a name derived from the Latin word for goat. It’s the brightest star in the constellation Auriga, who in Roman mythology is a charioteer who moonlights as a goatherder.

To get a personally guided tour of these night-sky sights and others overhead during May, download our 7½-minute-long astronomy podcast below.

There's no better guide to what's going on in nighttime sky than SkyWatch 2016, a yearlong guide prepared by the editors of Sky & Telescope magazine.

The post Tour May’s Sky: Jupiter Leads the Way appeared first on Sky & Telescope.

Red de púlsares podría detectar ondas gravitatorias de baja frecuencia

Ciencia Kanija -

Artículo publicado el 24 de febrero de 2016 en JPL

La reciente detección de ondas gravitatorias por LIGO llegó procedente de dos agujeros negros, cada uno de unas 30 veces la masa de nuestro Sol, fusionándose en uno. Las ondas gravitatorias se extienden a lo largo de un amplio rango de frecuencias que requieren distintas tecnologías para poder detectarlas. Un nuevo estudio realizado en el North American Nanohertz Observatory for Gravitational Waves (NANOGrav) ha demostrado que las ondas gravitatorias de baja frecuencia podrían detectarse pronto usando los radiotelescopios actuales.

Ondas gravitatorias

Ondas gravitatorias

“Detectar esta señal es posible si lográsemos monitorizar un número lo suficientemente grande de púlsares dispersos por todo el cielo”, señala Stephen Taylor, autor principal del artículo publicado en la revista The Astrophysical Journal Letters. Es investigador de posdoctorado en el Laboratorio de Propulsión a Chorro (JPL) de la NASA en Pasadena, California. “La prueba definitiva será ver el mismo patrón de de desviaciones en todos ellos”. Taylor y sus colegas del JPL y el Instituto Tecnológico de California (Caltech) en Pasadena han estado estudiando la mejor forma de usar los púlsares para detectar señales procedentes de ondas gravitatorias de baja frecuencia. Los púlsares son estrellas de neutrones muy magnetizadas, los núcleos girando a toda velocidad que quedan después de que las estrellas masivas estallen como supernovas.

La teoría general de la relatividad de Einstein predice que las ondas gravitatorias – ondulaciones en el espacio-tiempo – emanan de objetos masivos en aceleración. Las ondas gravitatorias de nanohertz son emitidas a partir de pares de agujeros negros supermasivos que se orbitan entre sí, cada uno de los cuales con millones o miles de millones de veces la masa de los detectados por LIGO. Estos agujeros negros se originan en el centro de distintas galaxias que colisionan. Lentamente se atraen entre sí y, finalmente, se fusionan para crear un único agujero negro de tamaño mayúsculo.

Al orbitarse entre sí, los agujeros negros tiran del tejido del espacio y crean una débil señal que viaja en todas direcciones, como una vibración en una tela de araña. Cuando esta vibración pasa por la Tierra, sacude levemente nuestro planeta, provocando un desplazamiento con respecto a los lejanos púlsares. Las ondas gravitatorias formadas por agujeros negros supermasivos binarios necesitan meses, o años, para pasar por la Tierra, y requieren muchos años de observaciones para poder detectarlas.

“Las fusiones de galaxias son comunes, y creemos que hay muchas más galaxias que albergan agujeros negros supermasivos binarios, los cuales deberíamos poder detectar”, señala Joseph Lazio, uno de los coautores de Taylor, también de JPL. “Los púlsares nos permitirán ver estos objetos masivos conforme se acercan lentamente en espiral”.

Una vez que estos gigantescos agujeros negros se acercan mucho entre sí, las ondas gravitatorias son demasiado cortas como para detectarlas usando púlsares. Los interferómetros láser espaciales como eLISA, una misión que está siendo desarrollada por la Agencia Espacial Europea con participación de la NASA, trabajarían en la banda de frecuencia que puede detectar la firma de la fusión de agujeros negros supermasivos. La misión LISA Pathfinder, que incluye un sistema impulsor de estabilización gestionado por el JPL, está actualmente probando las tecnologías necesarias para la futura misión eLISA.

Encontrar pruebas de los agujeros negros supermasivos binarios ha sido una tarea difícil para los astrónomos. Los centros de las galaxias contienen muchas estrellas, e incluso los mayores agujeros negros son bastante pequeños, comparables al tamaño del Sistema Solar. Ver señales de estos objetos entre el brillo de la galaxia que los rodea es complejo.

En lugar de esto, los radioastrónomos buscan las señales gravitatorias de estos objetos binarios. En 2007, NANOGrav empezó a observar un conjunto de púlsares de rotación rápida para tratar de detectar pequeños desplazamientos provocados por ondas gravitatorias.

Los púlsares emiten haces de ondas de radio, algunos de los cuales barren la Tierra una vez en cada rotación. Los astrónomos detectan esto como un pulso rápido de emisión de radio. La mayor parte de los púlsares rotan varias veces cada segundo, pero algunos, conocidos como púlsares de milisegundo, rotan cientos de veces más rápidamente.

“Los púlsares de milisegundo tienen unos tiempos de llegada extremadamente predecibles, y nuestros instrumentos lograron medirlos con un margen de error de una diezmillonésima de segundo”, señala Maura McLaughlin, radioastrónomo en la Universidad de Virginia Occidental en Morgantown, y miembro del equipo NANOGrav. “Gracias a esto, podemos usarlos para detectar desplazamientos increíblemente pequeños en la posición de la Tierra”.

Pero los astrofísicos de JPL y Caltech advierten de que detectar ondas gravitatorias tenues requeriría algo más que unos cuantos púlsares. “Somos como una araña en el centro de la tela”, explica Michele Vallisneri, también miembro del grupo de investigación de JPL/Caltech. “Cuantas más hebras tengamos en nuestra red de púlsares, más probable será que sintamos el paso de una onda gravitatoria”.

Vallisneri dijo que para lograr esta hazaña se requerirá una colaboración internacional. “NANOGrav está actualmente monitorizando 54 púlsares, pero sólo podemos ver algunos del hemisferio sur. Tendremos que trabajar más estrechamente con nuestros colegas de Europa y Australia para lograr una cobertura de todo el cielo como requiere esta búsqueda”.

La factibilidad de este enfoque se puso en cuestión recientemente cuando un grupo de investigadores australianos de púlsares informaron de que no lograron detectar tales señales cuando analizaron un conjunto de púlsares con las medidas de sincronización más precisas. Tras estudiar el resultado, el equipo de NANOGrav determinó que esta no detección no fue una sorpresa, y que era el resultado de la combinación de unos modelos de ondas gravitatorias optimistas, y el análisis de muy pocos púlsares. Su respuesta, de una página, se publicó a través del servicio electrónico arXiv.

A pesar de los desafíos técnicos, Taylor confía en que su equipo esté en el camino adecuado. “Las ondas gravitatorias bañan la Tierra constantemente”, apunta Taylor. “Dado el número de púlsares que observa NANOGrav, y otros equipos internacionales, esperamos tener pruebas claras y convincentes de ondas gravitatorias de baja frecuencia en la próxima década”.

Para información adicional puedes visitar: http://nanograv.org/

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A Moon for Kuiper Belt’s Makemake

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Astronomers have been searching for companions to the distant dwarf planet Makemake for years. Finally, they've spotted one.

Of the four "dwarf planets" now recognized in the outer solar system, Pluto, Eris, and Haumea all have at least one moon. The fourth, Makemake, seemed to be the odd dwarf out. Astronomers used the Hubble Space Telescope to search for any companions in 2006 but turned up nothing.

Makemake and its moon

A Hubble Space Telescope image taken April 27, 2015, reveals the first moon (arrowed) ever discovered around the dwarf planet 136472 Makemake, which was discovered in 2005.
NASA / ESA / Alex Parker & others

Now, having tried again, they've turned up "something." As announced jointly yesterday by the IAU's Minor Planet Center and Space Telescope Science Institute, images of Makemake taken a year ago show an object traveling together with Makemake through the Kuiper Belt some 52.4 astronomical units (7.8 billion kilometers) from the Sun. It's magnitude 28.8 — 1,300 times fainter than Makemake itself. And that's about all that Alex Parker (Southwest Research Institute) and his three co-discoverers know for sure about this find, whose official designation is S/2015 (136472) 1 — but which they've nicknamed "MK2."

The problem is that the object shows clearly in images from April 27, 2015, but not in another set recorded just two days later. Parker's team concludes that MK2 is playing "hide and seek" with observers, hiding in the glare of Makemake at some times and popping into view at others. That's likely if we're seeing the moon's orbit nearly edge on and if it's not too distant from Makemake itself. For example, if its orbit is circular and 21,000 km in radius, MK2 should only be observable by HST about half the time; if the radius were 100,000 km, it should be in view 90% of the time. So, statistically, the tighter orbit seems more likely; it would have a period of about 12 days.

But it's all best-guesstimates for now. As the team points out in a write-up submitted to Astrophysical Journal Letters, the Hubble images really don't constrain the orbit well. It might have a semimajor axis anywhere up to 300,000 km (with a period of nearly two years) and an inclination anywhere from 63° to 87° — it could even be going in the opposite direction.

Makemake and its moon artwork

Here's how co-discoverer Alex Parker envisions the appearance of distant, icy Makemake and its recently discovered moon.
NASA / ESA / Alex Parker

Those uncertainties aside, the moon's discovery appears to solve an observational puzzle that's nagged astronomers for years. "When the Spitzer and Herschel space observatories looked at Makemake, the thermal emission they saw was not consistent with one material," Parker tweeted yesterday. "Instead, it seemed like most of Makemake was very, very bright, but a small part of it must be dark and warmer." But even though this largish dwarf rotates in just 7.8 hours, the "dark stuff" never seemed to go away.

However, if MK2 has a diameter of 175 km (reasonable, since Makemake itself is 1,430 km across), then its surface must be very dark — just 4% reflective — and that would go a long way toward explaining the "dark, warm component" seen in Makemake's spectrum.

As was the case following the discovery of Charon around Pluto, the existence of MK2 has wide-ranging implications both for Makemake and large Kuiper Belt objects in general:

●  Once they pin down the orbit, astronomers will quickly deduce the bulk density of Makemake. Right now estimates range from 1.4 g/cm3 (mostly ice) to 3.2 g/cm3 (mostly rock), even though frozen methane dominates its spectrum.

●  If MK2 really is dark, how did it get that way? Perhaps it was captured, or perhaps it resulted from a long-ago collision that left it stripped of any volatile material.

●  If MK2 really is in an edge-on orbit, then it might soon begin a series of "mutual events" with Makemake, with the two bodies periodically passing in front of and behind one another. When Pluto and Charon did this during the late 1980s, astronomers gleaned important new details about both bodies.

●  If the plane of MK2's orbit is perpendicular to Makemake's spin axis, then the entire system must be significantly tipped with respect to the ecliptic. It also means that we're currently viewing Makemake near an equinox in its 309-year-long orbit around the Sun.

●  And, finally, it means that all four of the Kuiper Belt's known dwarf planets possess at least one moon. This fact, in itself, might be a big deal. As Parker and his team conclude in their submitted paper, "The apparent ubiquity of trans-Neptunium dwarf-planet satellites further supports the idea that giant collisions are a near-universal fixture in the histories of these distant worlds."

The post A Moon for Kuiper Belt’s Makemake appeared first on Sky & Telescope.

Milky Way’s New Neighbor: A Giant Dwarf

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Astronomers have discovered a “feeble giant”: one of the largest dwarf galaxies ever seen near the Milky Way.

The Large and Small Magellanic Clouds, pictured here, are dwarf galaxies easy to spot from a dark, Southern Hemisphere sky. Crater 2 isn't much smaller, but its distance and spread-out stars make much fainter and harder to spot than its bright brethren.ESO / S. Brunier

The Large and Small Magellanic Clouds, pictured here, are easy to spot from a dark, Southern Hemisphere sky. Crater 2 isn't much smaller, but its distance and spread-out stars make it much fainter and harder to spot than its bright brethren.
ESO / S. Brunier

Ever since astronomers discovered our universe’s accelerating expansion, tension has rippled between theory and observations, especially in studies of our galaxy’s neighborhood.

The standard model of cosmology, which suggests that dark energy and “cold” dark matter govern the universe’s evolution, predicts many more small galaxies near the Milky Way than what we’ve observed so far. Dwarfs should be the building blocks of larger galaxies like our own, so the lack has puzzled astronomers — are they not there, or are we just not seeing them?

Observations have closed in on theory in recent years with the advent of large surveys such as the Sloan Digital Sky Survey and the Dark Energy Survey, where observers have begun to identify hard-to-find dwarf galaxies. Dozens of dwarfs have been spotted over the last 15 years. But theory suggests perhaps even hundreds more have yet to be discovered.

Now, the list of known dwarfs has just added one of its largest members: Crater 2. You’d think large dwarfs would be easy to find, but this one’s stars are spread out and easily entangled with the stars of the Milky Way. It took a sensitive survey to pick out the small galaxy hidden behind the galaxy’s stars.

A New Dwarf Galaxy New dwarf galaxy candidates near Milky Way

This image maps dwarf galaxy candidates near the Milky Way (red and blue), not including Crater 2.
Y. Mao, R. Kaehler / R. Wechsler

Gabriel Torrealba (University of Cambridge, UK) led a team that discovered the Crater 2 dwarf galaxy in survey data collected at the Very Large Telescope in Chile. The team used specialized software to spot over-crowding among stars, searching for dim stellar clumps. But identifying a clump isn't enough. Only Crater 2 contained red giant stars and horizontal branch stars — both old, evolved stars that mark an ancient stellar population separate from the youthful Milky Way disk.

Torrealba and colleagues estimate that Crater 2 lies 391,000 light-years from Earth. That makes it one of the most distant dwarf galaxies known. It’s also one of the largest: at 6,500 light-years across, it comes in fourth among our galaxy’s neighbors, after the Large and Small Magellanic Clouds, and the torn-apart Sagittarius dwarf galaxy. Moreover, it’s incredibly diffuse, its stars spread out over several square degrees. So despite its size, Crater 2 is much fainter than those Milky Way companions, nearly 100 times fainter than Sagittarius and almost 10,000 times fainter than the LMC.

Dwarf Galaxy Groups

The discovery of Crater 2 may help unlock an ongoing puzzle in the Milky Way's evolution. As astronomers began to discover dwarf galaxies en masse in large sky surveys, it soon became clear that some dwarfs cluster in their orbits. Crater 2 is no exception: the team estimated that the dwarf’s orbit lines up with those of the Crater globular cluster, as well as the Leo IV, Leo V and Leo II dwarf galaxies.

While not a definitive association, similar orbits suggest that these objects might form a group that fell together into our galaxy’s gravitational well. Astronomers have recently found similar groups near the Large Magellanic Cloud, suggesting that our galaxy’s halo might have formed through many such group captures.

As sky surveys continue to enable discoveries of dwarf galaxies such as Crater 2, the gap between theory and observations continues to narrow, clarifying our understanding of the Milky Way's evolution. The future is bright for the study of these dim galaxies, thanks to surveys such as the Large Synoptic Sky Survey (LSST) on the horizon. LSST will push to even fainter magnitudes and may finally resolve the discrepancy between theory and observation.

Reference:
G. Torrealba et al. "The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater." Accepted for publication in Monthly Notices of the Royal Astronomical Society.

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Hubble descubre una luna orbitando a Makemake

Ciencia Kanija -

Artículo publicado el 26 de abril de 2016 en HubbleSite News

Escrutando los confines del Sistema Solar, el Telescopio Espacial Hubble de la NASA ha observado una pequeña y oscura luna orbitando a Makemake, el segundo planeta enano helado más brillante, después de Plutón, en el Cinturón de Kuiper.

La luna, conocida provisionalmente como S/2015 (136472) 1 y apodada MK 2, tiene un brillo más de 1300 veces menor que Makemake. MK 2 se vio aproximadamente a unos 20 000 kilómetros del planeta enano, y su diámetro estimado es de unos 160 kilómetros. Makemake, en comparación, tiene unos 1400 kilómetros de diámetro. El planeta enano, descubierto en 2005, toma su nombre de la deidad creadora de los habitantes de Rapa Nui, de la Isla de Pascua.

Makemake y MK 2

Makemake y MK2 Crédito: Hubble

El Cinturón de Kuiper es una enorme reserva de material congelado remanente de la construcción del Sistema Solar hace 4500 millones de años, y hogar de varios planetas enanos. Algunos de estos mundos tienen satélites conocidos, pero éste es el primer descubrimiento directo de un objeto compañero de Makemake. Makemake es uno de los cinco planetas enanos reconocidos por la Unión Astronómica Internacional.

Las observaciones se realizaron en abril de 2015 con la Wide Field Camera 3 de Hubble. La capacidad única del telescopio para ver objetos tenues cerca de otros brillantes, junto con su fina resolución, permitió a los astrónomos separar la luna del brillo de Makemake. El descubrimiento se anunció en la Minor Planet Electronic Circular.

El equipo de observación usó la misma técnica de Hubble para estudiar la luna que para hallar los satélites más pequeños de Plutón en 2005, 2011, y 2012. Varias investigaciones previas alrededor de Makemake no habían logrado encontrar nada. “Nuestras estimaciones preliminares demuestran que la órbita de la luna parece ser frontal, y esto significa que cuando miras al sistema la pierdes de vista a veces, ya que queda oculta en el brillo de Makemake”, comenta Alex Parker del Instituto de Investigación Southwest en Boulder, Colorado, quien lideró el análisis de las imágenes para estas observaciones.

El descubrimiento de una luna puede proporcionar una información valiosa sobre el sistema del planeta enano. Midiendo la órbita de la luna, los astrónomos pueden calcular una masa para el sistema, y lograr una visión de su evolución.

Descubrir la luna también refuerza la idea de que la mayor parte de planetas enanos tienen satélites.

“Makemake se encuentra en el grupo de objetos raros plutonianos, por lo que encontrar un compañero es importante”, señala Parker. “El descubrimiento de esta luna nos ha dado una oportunidad de estudiar Makemake en mucho mayor detalle de lo que habríamos sido capaces sin la compañera”.

Encontrar esta luna no hace más que aumentar los paralelismos entre Plutón y Makemake. Ambos objetos ya se sabe que están cubiertos por metano congelado. Como se hizo con Plutón, un posterior estudio del satélite revelará la densidad de Makemake, un resultado clave que indicará si la composición general de Plutón y Makemake también son similares. “Este nuevo descubrimiento abre un nuevo capítulo en la planetología comparativa en el Sistema Solar exterior”, señala el jefe del equipo Marc Buie del Instituto de Investigación Southwest en Boulder, Colorado.

Los investigadores necesitarán más observaciones de Hubble para realizar medidas precisas que determinen si la órbita de la luna es elíptica o circular. Los estudios preliminares indican que si la luna sigue un camino circular, completará una órbita alrededor de Makemake en 12 días o más.

Determinar la forma de la órbita de la luna ayudará a zanjar la cuestión sobre su origen. Una estrecha órbita circular implica que MK 2 probablemente es el producto de una colisión de Makemake contra otro Objeto del Cinturón de Kuiper. Si la luna tiene una órbita amplia y alargada, es más probable que sea un objeto capturado. Sea cual sea el caso, el evento habría tenido lugar hace miles de millones de años, cuando el Sistema Solar era joven.

El descubrimiento puede haber resuelto uno de los misterios sobre Makemake. Anteriores estudios infrarrojos del planeta enano revelaron que, aunque la superficie de Makemake es casi enteramente brillante y muy fría, algunas áreas parece más cálidas que otras. Los astrónomos había sugerido que esta discrepancia podía deberse a que el Sol calentase zonas oscuras concretas de la superficie de Makemake. Sin embargo, a menos que Makemake se encuentre orientado de una forma especial, estas zonas oscuras deberían hacer que el brillo del planeta variase sustancialmente mientras que gira, pero esta variabilidad nunca se ha apreciado.

Estos datos infrarrojos previos no tenían suficiente resolución como para distinguir a Makemake de MK 2. El reanálisis del equipo, basado en las nuevas observaciones de Hubble, sugiere que la superficie más cálida detectada anteriormente en luz infrarroja puede, en realidad, ser simplemente la oscura superficie de la compañera MK 2.

Existen varias posibilidades que podrían explicar por qué la luna tendría esta superficie tan negra, incluso aunque orbita a un planeta enano que es tan brillante como la nieve. Una idea es que, al contrario que objetos de mayor tamaño como Makemake, MK 2 es lo bastante pequeño como para no poder mantener gravitatoriamente una brillante y helada corteza, la cual se sublima, cambiando de sólido a gas, bajo la luz solar. Esto haría que la luna fuese similar a los cometas y otros Objetos del Cinturón de Kuiper, muchos de los cuales están cubiertos con material muy oscuro.

Cuando Caronte, la luna de Plutón, se descubrió en 1978, los astrónomos calcularon rápidamente la masa del sistema. La masa de Plutón era cientos de veces menor de la originalmente estimada cuando se descubrió en 1930. Con el descubrimiento de Caronte, los astrónomos supieron que había algo radicalmente diferente en Plutón. “Ése es el tipo de medida transformadora que puede permitirnos hacer el hecho de tener un satélite”, comenta Parker.

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Tips for a Successful Star Party

Sky&Telescope -

Planning a sidewalk stargazing event? Here are a few suggestions to make sure people walk away smiling.

Little Guy, Big Eyes

Everybody loves looking through a telescope, including this young participant during a recent Astronomy Day.
Bob King

I've taught community education astronomy in Duluth, Minnesota, for years and continue to be amazed at how stalwart people are when it comes to waiting their turn at the telescope on chilly nights. We always go out to observe after class no matter the weather, provided the sky is clear.

But resistance to cold or tolerance for mosquitoes only goes so far. Even Duluth skywatchers have their breaking point, so it's important to key in on bright, showy objects that easily reveal their charms to neophyte observers. For this reason I always chose the largest scope for the job to make the faint stuff as bright and easy to see as possible.

My job is an easy one if the Moon or a bright planet lights up the sky. In that case, it doesn't hurt to brush up on the names and sizes of prominent craters and other interesting lunar facts in advance. If you do your homework, you can impart a few essential nuggets of information to help those in line make the most of their minute at the eyepiece.

Only a minute? It seems much too short a time, but most people only gaze at an astronomical object for about 20 seconds, barely enough time to see anything! Whether it's out of politeness for the next in line, a brief attention span or something else, I always encourage people to take a minute and soak in the view as they might a painting by Picasso. Once they see the boldest features like Jupiter's two "stripes," I'll challenge them to the Great Red Spot (if present) or ask if they can tell that the planet is out of round.

Every detail visible becomes a learning opportunity involving the real thing rather than an image on a PowerPoint presentation. Just be careful to not go textbook on your audience. Leave them with a couple key concepts they'll remember and keep that line moving.

First Look at the King of the Planets

Parents and kids look at Jupiter through one of our local astronomy club telescopes during a recent Earth Day public stargazing event at the Lake Superior Zoo in Duluth, Minnesota
Bob King

Point to the Planets

When it comes to planets, if Jupiter or Saturn are visible, you're in luck. Saturn's rings never fail to amaze and newcomers love seeing the moons of both. It's a good idea to check beforehand with Sky & Telescope's Jupiter's Moons and Saturn's Moons to sort which moon is which. When you can name them, those little points of light become real places.

Venus and Mercury delight with their phases. Since Uranus and Neptune present so few details, I play a little game of guess-the-planet's-color. We compare notes and then discuss how atmospheric gases affect these planets' appearance.

Planetary Plenty

This summer will be perfect for hosting an all-solar system star party. Pick a night in June when all three bright planets are simultaneously visible along with a crescent or half Moon (June 8–12 is ideal). From left: Jupiter on April 18th, Saturn on April 2nd, and Mars on April 15th. South is up.
Paul Maxson

Mars is almost always too small to see very much, but it retains an allure that overcomes its visual deficiencies. Even in so-so seeing, no one ever seems disappointed to get their first look at the Red Planet. With opposition less than a month away, and Saturn's to follow in early June, a telescopic visit to all three would make a perfect opportunity for a public gathering. Throw in a crescent or half Moon, and you'll have your hands full.

Go Clubbing

Although I've done many solo astro outings, club events add an extra dimension of fun as well as take the pressure off a single observer. Each scope can specialize on a particular object, allowing attendees to get a taste of each without having to wait for everyone to see the one object before moving on to the next.

Often, while the line works its way past the eyepiece, I'll pull out a green laser and point out the brighter constellations. Once people start looking up, all those eyes catch many things that one set can easily miss. I get great satisfaction when someone shouts out that they've sighted a satellite, a meteor, or the start of a northern lights display. People love finding things on their own. Indeed this is how so many of us made our own first connection to the night sky. Discovery. It's potent stuff, so be sure to spend part of every observing session just looking up with the group.

Explore by Phone

Beginners take quickly to star-finding apps for mobile phones.
Bob King

After they get a taste of old-fashioned constellation hunting, surprise them by popping out your phone and demonstrating the power of some of the new sky apps for finding planets, stars and satellites. Many are free. I've listed a couple examples at the end of the article.

Some in your group will have to leave early. Always thank them for coming and make sure to give them a slip of paper with the names of both an Android and iPhone night sky / stargazing app and the websites where they can be downloaded. Of course, you will have thought of this in advance and have them ready for all your guests. Since nearly everyone has a smartphone, they can use the app to continue the journey of self-discovery on their own.

Proper Prep Makes the Star Party

Like I said earlier, when the planets and Moon are out, our job as night-sky tour guides is ever so much easier. Since that's not always the case, it's best to prepare a cosmic sampler that includes a bright representative of each major class of deep-sky object: open cluster, globular cluster, nebula, double star, and galaxy high enough in the sky for a great view. To that end, I've prepared two lists you might find helpful, one for the current season and another for summer.

If a bright gibbous or full Moon is out, I limit the session to the Moon, bright double stars, and bright open clusters. No sense explaining what they should be seeing when it's swamped by moonlight!

Your choices may (and probably will!) only partially overlap mine. Take these as a starting point:

Spring Season
  • Planet: Jupiter is beautifully placed for viewing all this spring. #1 on the list! Be alert for shadow transits and eclipses of its moons that may occur during your outing. The shadows of Ganymede, Io, and Callisto are easiest to see for beginners.
  • Open cluster:  M35 in Gemini / M37 in Auriga in early spring. Late spring, try M67 in Cancer.
  • Nebula: NGC 2392, a planetary nebula in Gemini. Great to use as a crystal ball to gaze into the Sun's far future.
  • Globular cluster: M3 in Canes Venatici. I use low power for many objects but not globulars. For impact, 150×-200× is best.
  • Double star: either Mizar-Alcor in the Big Dipper / Alpha (Cor Caroli) in Canes Venatici / Iota Cancri.
  • Red star: Star colors are often pale but certain carbon stars have striking, smoky red hues. These little gems always elicit "wows!" Try V Hydrae (currently ~8.6 magnitude). Click for a chart.
  • Galaxy: M51, the Whirlpool. One of the few galaxies that when high enough and viewed in a 10-inch or larger telescope reveals hints of spiral structure to a beginner. The M81–82 duo in UMa makes a great low-power pair that sweetly illustrates the difference between open and edge-on galaxies. If you're just looking for just a single bright galaxy, stop by either M94 (magnitude +8.9) or M63 (+9.3), both in Canes Venatici and easy to find. Their concentrated cores stands out well against their outer disks, making either a good choice for explaining basic galactic structure.
Nighttime Philosophy 101

Students in a community education astronomy class look at planets through a 15-inch reflector. Outings with the newcomers to astronomy make for an equal mix of inspiration, philosophical reflection, and good humor. In short, they're a blast.
Bob King

Summer Season
  • Planets: Take your pick — Jupiter, Mars and Saturn! Jupiter will leave the scene in July.
  • Open cluster: M11, the Wild Duck Cluster.
  • Nebula: M57, the Ring Nebula / M8, the Lagoon Nebula in Sagittarius, or the Veil Nebula in Cygnus. Use a nebular filter on both the Veil and M8 to enhance contrast and detail.
  • Globular cluster: M13, the Great Globular in Hercules / M22 in Sagittarius / M5 in Serpens
  • Double star: Beta Cygni (Albireo) / Beta Scorpii / Epsilon-1 and Epsilon-2 Lyrae, the "Double Double"
  • Red star: T Lyrae. Click for a chart.
  • Galaxy: M106 in UMa. Bright and big!

Always check for passes of the International Space Station (ISS) either at NASA's Spotthestation or on Heavens Above. Beginning skywatchers are delighted to know they can see the space station so easily. Watching it glide across the sky or suddenly disappear into Earth's shadow elicits a certain primal excitement.

Finally, when everyone else has gone home, a small, hardcore group will often remain. For these folks I keep an expanded list that includes more challenging objects: a bright quasar such as 3C273, currently well-placed in Virgo, additional galaxies, a planetary nebula, a close double star, and perhaps a comet.

When someone utters "wow!" at their first sight of a star cluster, I'm always reminded that sharing the sky works both ways. We help our guests expand their cosmic perspective, they help us enlarge our human one.

Resources

* Star Chart for Android — Free
* Star Chart for iPhone — Free
* Inexpensive and reliable green laser pointers

The post Tips for a Successful Star Party appeared first on Sky & Telescope.

Recovery Unlikely for Hitomi X-ray Satellite

Sky&Telescope -

The Japanese space agency JAXA has released a timeline covering the Hitomi space observatory's failure last month. Salvage efforts continue but recovery appears unlikely.

Hitomi in space

An artist's conception of Hitomi in space. 
JAXA

Things aren't looking good for the Hitomi X-ray observatory.

Last week, the Japanese Aerospace Exploration Agency (JAXA) released a report outlining the spacecraft failure and efforts to reestablish contact and control.

Launched from the Tanegashima Space Center on February 17, 2016, Hitomi was set to revolutionize X-ray astronomy. Initially known as the Astro-H mission, the satellite was renamed Hitomi — "pupil of the eye" in Japanese — shortly after launch.

Anatomy of a Disaster

Disaster struck on March 26th, when engineers commanded Hitomi to point at an active galactic center, one of a series of observations geared toward testing out the science instruments. JAXA put together a timeline of what they think happened next.

Shortly after the maneuver the spacecraft's attitude control system (ACS), which keeps the spacecraft pointed in the right direction, determined that the spacecraft was rotating — even though it wasn't. So the system commanded the spacecraft's reaction wheels to counter the rotation, and that caused the spacecraft to actually start spinning.

Meanwhile, because the ACS wasn't measuring the spacecraft's spin rate accurately, angular momentum was building up in the reaction wheels. They soon reached the limit of what they could hold, so the system placed the spacecraft into safe mode. Normally, safe mode for a satellite means it turns its solar arrays angled sunward for maximum power, while its antenna aim Earthward for communications.

This final maneuver, however, was the final nail in the coffin, as it turned on the thrusters to control where it was pointing. The attitude control system still hadn't gotten an accurate read on the spacecraft's rotation, so its spin only increased.

Hitomi diagram

A diagram of Hitomi/Astro-H.
JAXA

The U.S. Joint Space Operations Command (JspOC) reported first four, and later 10 pieces of debris (that is, pieces not including the main satellite body). JAXA officials now think those pieces might have included Hitomi's solar panels and the extendable optical bench, a boom vital for X-ray observations, which could have broken off as the spacecraft upped its spin rate. To make matters worse, JAXA believes the helium needed for the Soft X-ray Imager (SXS) has now fallen to a critical level, though it's not yet depleted.

JAXA hasn't written off Hitomi just yet, but the prognosis isn't good. Engineers have made contact with the spacecraft for a few brief moments during the past month, but haven't been able to regain control. JAXA notes that two debris objects will reenter the Earth's atmosphere over the coming weeks, one on April 29th and another on May 10th.

Hitomi on Earth

Hitomi on Earth, shortly before encapsulation.
JAXA

Hitomi was to join the ranks of the European Space Agency's XXM-Newton and NASA's NuSTAR and Chandra X-ray observatories in orbit. Hitomi would have made simultaneous observations of astronomical targets across the X-ray spectrum and into the gamma-ray regime, capabilities that set the satellite apart from its predecessors.

Interestingly, Hitomi did manage to make a few successful science observations before falling silent. Some results are already awaiting publication, and the remaining data will be analyzed soon.

"The probable loss of Hitomi is obviously a significant blow to the X-ray astronomy community, and to astrophysics in general," says Laura Brenneman (Smithsonian Astrophysical Observatory), a member of Hitomi's science team. "[Hitomi] would have certainly yielded new and unique insights into the physics of countless high-energy phenomena in the universe, on scales ranging from galaxy clusters, to active galactic nuclei, to stellar coronae."

Although we probably won't see an observatory-class replacement on the launch pad until at least 2029, with the European Space Agency's Athena, smaller missions could be launched before then.  Neutron star Interior Composition Explorer (NICER), for example, is an International Space Station payload that is scheduled to launch in early 2017.

Hunting Hitomi

Amateur satellite trackers played a vital role in confirming and chronicling the tumble of Hitomi in orbit. Currently in a 565- by 582-kilometer orbit, inclined 31° to Earth's equator, Hitomi is visible to observers from latitudes 40°S to 40°N. My wife and I caught sight of Hitomi twice from southern Spain, flashing a dire SOS as it tumbled past Sirius in the dusk sky.

The best method to spot the satellite is to note when Hitomi will pass near a bright star for your location, aim a set of binoculars at said star at the appointed time, then sit back and watch. Heavens-Above is a great resource to carry this out. Hitomi is listed under NORAD ID 2012-016A (41337). (The debris pieces have different designations: 41438 and 41443 for the pieces re-entering on April 29th and May 10th, respectively.)

Northern hemisphere viewers have a good set of Hitomi dawn passes coming up starting on April 30th. There's no word yet as to when Hitomi itself will reenter, in the event that engineers cannot reestablish control.

Space is hard, and the probable loss of Hitomi represents a serious blow to X-ray astronomy and the 61 nations that worked to put the satellite into space. As with many missions, the hard lessons learned from Hitomi will be paid forward to the successors of tomorrow.

The post Recovery Unlikely for Hitomi X-ray Satellite appeared first on Sky & Telescope.

Los datos del LHC a tu alcance

Ciencia Kanija -

Artículo publicado por Achintya Rao el 22 de abril de 2016 en Symmetry Magazine

La colaboración CMS ha publicado 300 terabytes de datos de investigación.

La colaboración CMS del CERN ha publicado más de 300 terabytes (TB) de datos abiertos de alta calidad. Estos datos incluyen más de 100 TB de datos procedentes de las colisiones entre protones a 7 TeV, la mitad de los datos recopilados en el LHC por el detector de CMS en 2011. Esta publicación sigue a la realizada en noviembre de 2014, que puso a disposición pública unos 27 TB de datos de investigación recopilados en 2010.

Colisiones en CMS

Colisiones en CMS

Los datos se encuentran disponibles en el Portal de Datos Abiertos del CERN y son de dos tipos. Los conjuntos de datos primarios están en el mismo formato que el usado por la colaboración para realizar su investigación. Los conjuntos de datos derivados, por otra parte, requieren una potencia de cálculo mucho menor, y pueden ser fácilmente analizados por estudiantes de instituto o universidad.

CMS también proporciona datos simulados generados con la misma versión de software que se usaría para analizar los conjuntos de datos primarios. Las simulaciones desempeñan un papel clave en la investigación en física de partículas. Los datos publicados se acompañan de unas herramientas de análisis y ejemplos de código diseñados para los conjuntos de datos. Una imagen de máquina virtual basada en CernVM, que viene precargada con el entorno de software necesario para analizar los datos de CMS, también puede descargarse del portal.

“Una vez que hemos agotado nuestra exploración de los datos, no vemos ninguna razón para no ponerlos a disposición pública”, comenta Kati Lassila-Perini, físico del CMS que dirige los trabajos de conservación de datos. “Los beneficios son numerosos, para inspirar a estudiantes de instituto, o para entrenar a los físicos de partículas del mañana. Y, personalmente, como coordinadora de conservación de datos de CMS, es una parte crucial para asegurar la disponibilidad a largo plazo de nuestros datos de investigación”.

El ámbito de la apertura de datos del LHC ya se ha demostrado con la anterior publicación de datos de investigación. Un grupo de teóricos del MIT quería estudiar la subestructura de los chorros — lluvias de cúmulos de hadrones registradas en los detectores de CMS. Dado que CMS no había realizado esta investigación concreta, los teóricos se pusieron en contacto con los científicos de CMS para asesorarse sobre cómo proceder. Esto generó una provechosa colaboración entre los teóricos del MIT y CMS.

“Como científicos, deberíamos tomarnos muy en serio la publicación de datos en las investigación patrocinadas con dinero público”, comenta Salvatore Rappoccio, físico de CMS que trabajó junto con los teóricos del MIT. “Además de demostrar una buena administración del patrocinio que hemos recibido, también proporciona un beneficio científico a nuestro campo de forma global. Aunque es una tarea difícil y abrumadora con mucho por hacer, la publicación de datos de CMS es un enorme paso adelante en la dirección correcta”.

Además, un físico de CMS en Alemania puso a trabajar a dos estudiantes en la validación de Datos Abiertos de CMS reproduciendo algunas gráficas clave a partir de artículos de CMS muy citados que usaron datos recopilados en 2010. Usando documentación disponible en abierto sobre el análisis de software de CMS, y con una guía del físico, los estudiantes lograron recrear unos gráficos que encajaban casi de forma idéntica con los de CMS, demostrando que puede lograrse usando estos datos.

“Estamos muy contentos de que podamos hacer públicos todos estos datos”, añade Lassila-Perini. “Estamos deseando ver cómo se utilizan fuera de nuestra colaboración, para investigación así como para herramientas educativas”.

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