Astronomy Archives

October 3, 2008December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast – October 3-5, 2008

Greetings, fellow SkyWatchers! It’s Friiiiiiday… And time to head out to the Moon to begin some lunar exploration. Why not? This weekend commemorates Robert Goddard’s birthday! While we’re rocketing skyward, we’ll take a look at a great globular cluster that’s easy in both binoculars and telescopes, plus a few great stars you might or might not know about. For lucky viewers in South Africa and Australia? Head’s up for an Antares occultation! Are you ready? Then let’s head out into the night….

Friday, October 3, 2008 – Tonight we’ll begin on the lunar surface and go out on a limb – the southeastern limb – to have a look at an unusual crater. Named for the French agrochemist and botanist Jean-Baptiste Boussingault, this elliptical-appearing crater actually spans a handsome 71 kilometers. What makes Boussingault so unusual is that it is home to its own large interior crater – A. This double-ring formation gives it a unique stepped, concentric look that’s worth your time!

Now wait for the Moon to wester a bit and we’ll return to Pegasus and the incredible M15. Although skies are a bit bright, you can still have a very satisfactory look at M15 through any size binoculars or telescope.

You can find it easily just about two fingerwidths northwest of red Epsilon Pegasi – Enif (RA 21 29 58 Dec +12 10 00). Shining brightly at magnitude 6.4, low power users will find it a delightfully tight ball of stars, but scope users will find it unique. As resolution begins, sharp-eyed observers will note the presence of a planetary nebula – Pease 1. This famous X-ray source you have just seen with your eyes may have supernova remnants buried deep inside…

When we’re done? Let’s go have a look at Gamma Aquilae just for the heck of it. Just northwest of bright Altair, Gamma (RA 19 46 15 Dec +10 36 47) has the very cool name of Tarazed and is believed to be over 300 light-years away. This K3-type giant will show just a slight yellow coloration – but what really makes this one special is the low power field! Enjoy it in binoculars or drop in your favorite panoramic eyepiece and just relax… Sometimes there is peace and contentment in the light.

Saturday, October 4, 2008 – Today in 1957, the USSR’s Sputnik 1 made space history as it became the first manmade object to orbit the earth. The Earth’s first artificial satellite was tiny, roughly the size of a basketball, and weighed no more than the average man. Every 98 minutes it swung around Earth in its elliptical orbit…and changed everything. It was the beginning of the “Space Race.” Many of us old enough to remember Sputnik’s grand passes will also recall just how inspiring it was. Take the time with your children or grandchildren to check www.heavens-above.com for visible passes of the ISS, and think about how much our world has changed in just over half a century!

Do you remember the Professor Burg who discovered Antares’ companion during an occultation? Well, tonight we’re going to become a whole lot more familiar with the good professor, because it’s about to happen again! For almost all observers, at some time brilliant red Antares will be less than half a degree to the north of tonight’s crescent Moon. For South African and Australia, this will be a spectacular occultation, so be sure to check IOTA for precise times and locations on this universal date.

While we’re waiting on the event, let’s have a look at the crater named for Burg as we begin by using past study crater Posidonius as our guide. How many more of these craters can you identify?

If you walk along the terminator to the northwest, you’ll see the punctuation of 40 kilometer wide Burg just emerging from the shadows. While it doesn’t appear to be a grand crater like Posidonius, it has a redeeming feature: it’s deep – really deep. If Burg were filled with water here on Earth, it would require a deep submergence vehicle like ALVIN to reach its 3680 meter floor! This class II crater stands nearly alone on an expanse of lunarscape known as Lacus Mortis. If the terminator has advanced enough at your time of viewing, you may be able to see this walled-plain’s western boundary peeking out of the shadows.

Sunday, October 5, 2008 – Today marks the birthdate of Robert Goddard. Born in 1882, Goddard is known as the father of modern rocketry – and with good reason. In 1907, Goddard came into the public eye when a cloud of smoke erupted from the basement of the physics building in Worcester Polytechnic Institute, from which he had just fired a powder rocket. By 1914, he had patented the use of liquid rocket fuel, and the design of two- or three-stage solid fuel rockets. His work continued as he sought methods of lofting equipment ever higher, and by 1920 he had envisioned his rockets reaching the Moon. Among his many achievements, he proved that a rocket would work in a vacuum. By 1926 the first scientific equipment went along for the ride; by 1932, Goddard was guiding those flights; and by 1937 his motors were pivoting on gimbals and being controlled gyroscopically. His lifetime of work went pretty much unnoticed until the dawn of the Space Age, but in 1959 (14 years after his death) he received acclaim at last as NASA’s Goddard Space Flight Center was established in his memory.

Tonight let’s rocket to the Moon to explore a binocular curiosity located on the northeast shore of Mare Serenitatis. Look for the bright ring of Posidonius, which contains several equally bright points both around and within it. Now look at Mare Crisium and get a feel for its size. A little more than one Crisium’s length west of Posidonius you’ll meet Aristotle and Eudoxus. Drop a similar length south and you will be at the tiny, bright crater Linne on the expanse of Mare Serenitatis. So what’s so cool about this little white dot? With only binoculars you are resolving a crater that is one mile wide, in a seven mile wide patch of bright ejecta – from close to 400,000 kilometers away!

Tonight in 1923, Edwin Hubble was also busy as he discovered the first Cepheid variable in the Andromeda Galaxy. Hubble’s discovery was crucial in proving that the objects once classed as “spiral nebulae” were actually independent and external stellar systems like our own Milky Way.

While we’re out, let’s have a look at a Mira type variable, as we look about halfway between Beta and Gamma Cygni for Chi (RA 19 50 33 Dec +32 54 51).

Noted for being the second long-term variable discovered (by Gottfried Kirch in 1868), Chi is visible to the unaided eye when at maximum – but demands a telescope at minimum. Fluxing between magnitude 4 and 12, you’ll know if you’ve caught it at its lowest point when you can’t distinguish it from background stars! Of course, this is another wonderful cosmic joke on Bayer – for it was several years until the star he classed as visual returned to view. Maximum or minimum? Enjoy your own perceptions of this lovely red star!

Now, as the days pass… Watch as Jupiter and the Moon draw closer and then part company! It’s a lovely sight that doesn’t require any special equipment and makes for a relaxing evening of stargazing. Until next time, I wish you clear skies and a great weekend!

This week’s awesome images are: Crater Boussingault – Credit: Jim Mosher (LPOD), M15 – Credit: NOAO/AURA/NSF, Gamma Aquilae – Credit: Palomar Observatory, courtesy of Caltech, Sputnik 1 – Credit: NASA, 2005 Antares Occultation – Credit: John Chumack, Detail view of Posidonius – Credit: Greg Konkel, Robert Goddard – Credit: NASA, Crater Linne – Credit: Greg Konkel Annotations: Tammy Plotner and Chi Cygni at minimum (center of field) – Credit: Palomar Observatory, courtesy of Caltech. Many, many thanks! Each time we see these images it improves our understanding of what we look at and what we are looking for and their use is greatly appreciated!!

October 2, 2008April 26, 2016 by Nancy Atkinson

The Telescope Has a Birthday Party

[/caption]

All sorts of anniversaries going on these days — yesterday was NASA’s 50th birthday, on Saturday, Oct. 4 is the 51st anniversary of Sputnik’s launch, and today we celebrate the birthday of the telescope. 400 years ago, officials in the Netherlands were pondering over a patent application by a spectacle maker named Hans Lipperhey. The patent was for a “device by means of which all things at a very great distance can be seen as if they were nearby.” This is the earliest known record of a telescope. A few months later, scientist Galileo Galilei would get his hands on one.

Over at Wired, they are having a big celebration for the telescope’s birthday, including an article by some writer named Nancy Atkinson that includes a gallery of images and descriptions of the ten largest ground-based telescopes on Earth. It’s called “Giants of Earth and Space.” But there’s all sort of other interesting features, including a place where you can upload your favorite astronomical image that was taken by a ground-based telescope.

So check it out to celebrate. But of course this biggest party will be next year — the whole year of 2009 in fact, during the International Year of Astronomy. Look for more info and features about all the great events and ways you can participate in future articles on Universe Today

October 1, 2008December 24, 2015 by Fraser Cain

Uranus Pictures

Uranus, seen by Voyager 2. Image credit: NASA/JPL

So far, only one spacecraft has ever captured an image of Uranus: NASA’s Voyager 2 spacecraft. So let’s take a look at some pictures of Uranus, some captured by Voyager 2, and others seen from Hubble, and even here on the ground.

[/caption]
This is the classic image of Uranus, taken by NASA’s Voyager 2 spacecraft during its 1986 flyby of Uranus. During this mission, Voyager 2 came within 81,500 kilometers of the cloudtops of Uranus. Until then, the best pictures of Uranus came from telescopes on Earth. Nothing compared to the pictures of Uranus sent back by Voyager 2.

Uranus seen from Earth. Image credit: Keck

This beautiful picture of Uranus might look like it was captured by a space telescope, but it was actually taken from the powerful Keck telescope located on Hawaii’s Mauna Kea. This image shows Uranus in the infrared spectrum, which reveals the detailed cloud patterns in the atmosphere of the planet.

Uranus with its moons and rings. Image credit: Hubble

This Uranus pic was captured by the Hubble Space Telescope. On the left is the image itself, and then on the right are the names of all the moons captured in this photograph of Uranus.

This beautiful image of Uranus was captured by NASA’s Voyager 2 spacecraft curing its 1986 flyby of the planet. It was actually three images captured at different wavelengths and then combined on computer.

Like these pictures of Uranus? Here are some images of Pluto, and photographs of the Sun.

If you’d like more info on Uranus, check out Hubblesite’s News Releases about Uranus. And here’s a link to the NASA’s Solar System Exploration Guide to Uranus.

We have recorded an episode of Astronomy Cast just about Uranus. You can access it here: Episode 62: Uranus.

October 1, 2008December 24, 2015 by Fraser Cain

Mass of Uranus

Uranus Compared to Earth. Image credit: NASA

[/caption]
The mass of Uranus is 8.68 x 10²⁵ kg.

Want to put that in perspective? That’s 14.536 times more than the mass of Earth. That makes Uranus a pretty massive world, but it’s actually just a tiny fraction of Jupiter. Jupiter is 21.9 times more massive than Uranus.

Even though Uranus is much more massive than Earth, it has a fairly low density. in fact, it’s the second lowest density in the Solar System; only 1.27 g/cm³. If you could stand on the surface of Uranus (you can’t… don’t try), would experience only 89% the force of gravity that you would experience on Earth.

If you could peer inside Uranus, you would discover that most of the planet consists of ices, like water, ammonia and methane.

Here’s an interesting article about the mass of Mercury. And here’s an article about the mass of Jupiter.

If you’d like more info on Uranus, check out Hubblesite’s News Releases about Uranus. And here’s a link to the NASA’s Solar System Exploration Guide to Uranus.

We have recorded an episode of Astronomy Cast just about Uranus. You can access it here: Episode 62: Uranus.

October 1, 2008December 24, 2015 by Fraser Cain

Tilt of Uranus

[/caption]
The Earth’s axis is tilted about 23.5 degrees. This is why we have seasons on Earth. But the axis of Uranus is tilted so far it’s hard to imagine how it might have even happened. The axis of Uranus is tilted at an angle of 98-degrees compared to the Sun’s orbital plane.

While the rest of the planets in the Solar System can be thought of like spinning tops, Uranus is more like a rolling ball going around the Sun. During the point of the Uranian solstices, one pole faces the Sun continuously, while the other pole faces away. Only a thin strip of the surface of Uranus experiences any kind of night/day cycle. Uranus’ poles experience 42 years of continuous sunlight, and then 42 years of continuous darkness. During the time of the equinox on Uranus, the planet’s equator is facing the Sun, and so it experiences day/night cycles like we have here on Earth.

What could have caused Uranus to be tilted over on its side like this? Astronomers think that a large protoplanet smashed into Uranus billions of years ago. This collision set the planet tumbling. Eventually it settles into its current axial tilt.

Here’s a cool article on Universe Today about mysteries of the Solar System, including the question, why is Uranus tilted? And here’s an article about images of Uranus and Neptune captured by Hubble.

Here’s the same question posed to “ask a scientist”, and here’s an article from the Planetary Society Blog.

We have recorded an episode of Astronomy Cast just about Uranus. You can access it here: Episode 62: Uranus.

October 1, 2008December 24, 2015 by Fraser Cain

Size of Uranus

[/caption]
Sure, Uranus is big… but how big is it? There are so many ways we can measure the size of Uranus, so let’s look at all of them.

First, let’s take a look at diameter. The diameter of Uranus is 51,118 km across. For comparison, this is about 4 times bigger than Earth.

Now, let’s look at volume. The total volume of Uranus is 6.833×10¹³ km³. Again, for comparison, you could fit 63 Earths inside Uranus, and still have room to spare.

Next, mass. The mass of Uranus is 8.68×10²⁵ kg. This is about 14.5 times more massive than Earth. This sounds like a lot, but this makes Uranus the smallest of the outer planets, smaller even than Neptune.

How about surface area? The surface area of Uranus is 8.1×10⁹ km². This would let you flatten out almost 16 Earths to cover the surface area of Uranus.

How big are the other planets? Here’s how big Jupiter and Saturn are.

If you’d like more info on Uranus, check out Hubblesite’s News Releases about Uranus. And here’s a link to the NASA’s Solar System Exploration Guide to Uranus.

We have recorded an episode of Astronomy Cast just about Uranus. You can access it here: Episode 62: Uranus.

October 1, 2008December 24, 2015 by Fraser Cain

Gravity on Uranus

[/caption]
If you could stand on the surface of Uranus (you can’t, for so many reasons), you would experience 89% the force of gravity that you experience on Earth. Another way to look at it is that objects dropped towards Uranus will accelerate towards the planet at 8.69 m/s².

Does it seem a little strange to you that an planet like Uranus, with the 14 times the mass of Earth, would pull at you with less gravity if you could stand on its surface? The mass is important, but it all depends on how closely that mass is held together. Uranus is the second least dense planet in the Solar System (after Saturn). It has enough volume to hold 63 Earths, but it only has 14 times our mass.

So if you could stand on the surface of the planet – you can’t, don’t try – you would have a difficult time noticing the lower gravity of Uranus. It would feel very similar to Earth gravity.

What would it be like to walk on other planets? Here’s the gravity of Mercury, and here’s the gravity of Jupiter.

If you’d like more info on Uranus, check out Hubblesite’s News Releases about Uranus. And here’s a link to the NASA’s Solar System Exploration Guide to Uranus.

We have recorded an episode of Astronomy Cast just about Uranus. You can access it here: Episode 62: Uranus.

October 1, 2008December 24, 2015 by Fraser Cain

How Should You Pronounce “Uranus”?

Uranus, captured by Voyager 2. Image credit: NASA/JPL

[/caption]
Go ahead and say Uranus. Feel free to giggle if you like. I know, I know, it sounds like a dirty word. So what is the proper pronunciation of Uranus. Is there a way to talk about it without having school kids giggle.

The standard way to pronounce Uranus among astronomers is to put the emphasis on the first syllable “ur” and then say the second part “unus”. This is the standard literary pronunciation. The more common way people have pronounced it is u-ra-nus, with the “ra” sounded like “ray”.

The truth is that all the different ways of pronouncing Uranus are perfectly fine, even the way that sounds a little dirty.

We have written many articles about Uranus here on Universe Today. Here’s an article about the rings of Uranus seen edge on. And here’s one about a dark spot in its clouds.

If you’d like more info on Uranus, check out Hubblesite’s News Releases about Uranus. And here’s a link to the NASA’s Solar System Exploration Guide to Uranus.

We have recorded an episode of Astronomy Cast just about Uranus (we even talk about how to pronounce it). You can access it here: Episode 62: Uranus.

October 1, 2008December 24, 2015 by Fraser Cain

How Far is Uranus from Earth?

[/caption]
Let’s see how far away Uranus is from the Earth. First consider the fact that both Earth and Uranus are orbiting the Sun. This means that the distance between them can change, depending on their relatively positions in the Solar System.

The closest Uranus can get to Earth is 2.57 billion km.

Imagine Earth, Uranus and the Sun are all in straight line. When Uranus is at its closest point to Earth, the three objects are lined up with the Sun, Earth and Uranus. This is when Uranus is a mere 2.57 billion km. But Earth and Uranus are located on opposite sides of the Sun, they’re at their most distant point. When this happens, they’re 3.15 billion km.

What about the other planets? Here’s how far away Mars, Jupiter and Saturn are from Earth.

If you’d like more info on Uranus, check out Hubblesite’s News Releases about Uranus. And here’s a link to the NASA’s Solar System Exploration Guide to Uranus.

We have recorded an episode of Astronomy Cast just about Uranus. You can access it here: Episode 62: Uranus.

October 1, 2008December 24, 2015 by Tammy Plotner

Reflections of The Soul – IC 1848 by Ken Crawford

[/caption]

If we want to be technical, Lynds Bright Nebula 667 is the designation and it’s also known as Sharpless 2-199. Captured here is Collinder open clusters 34, 632 and 634 and small emission nebula 670 and 669 along with the entire cluster designation known as IC 1848. However, let’s forsake science for just a few moments and take a look at what it’s more commonly known as…. The “Soul Nebula”.

Situated along the Perseus arm of the Milky Way galaxy, the “Soul Nebula” reflects true inner beauty as well as a generous portion of hard science. Just this year, this giant cloud of molecular gas was the target study for triggered star formation. According to the work of Thompson (et al); “We have carried out an in-depth study of three bright-rimmed clouds SFO 11, SFO 11NE and SFO 11E associated with the HII region IC 1848, using observations carried out at the James Clerk Maxwell Telescope (JCMT) and the Nordic Optical Telescope (NOT), plus archival data from IRAS, 2MASS and the NVSS. We show that the overall morphology of the clouds is reasonably consistent with that of radiative-driven implosion (RDI) models developed to predict the evolution of cometary globules. There is evidence for a photoevaporated flow from the surface of each cloud and, based upon the morphology and pressure balance of the clouds, it is possible that D-critical ionisation fronts are propagating into the molecular gas. The primary O star responsible for ionising the surfaces of the clouds is the 06V star HD 17505. Each cloud is associated with either recent or ongoing star formation: we have detected 8 sub-mm cores which possess the hallmarks of protostellar cores and identify YSO candidates from 2MASS data. We infer the past and future evolution of the clouds and demonstrate via a simple pressure-based argument that the UV illumination may have induced the collapse of the dense molecular cores found at the head of SFO 11 and SFO 11E.”

With an estimated age of 1 Myr, IC 1848 is home to seventy-four sources of young stellar objects and all of them increase from outside of the rim to the center of the molecular cloud. The bright rim is an ionization front – the barrier between between the hot ionized gas of the HII region and the cold dense material of the molecular cloud where high mass stars are forming. Why is reflecting on the “Soul” so important? Probably because recent studies of meteorites have shown Fe isotopes present in the early solar nebula – suggesting our Sun was given birth in a region on high-mass star formation that experienced a supernova event. Bright-rimmed clouds like IC1848 replicate those conditions.

According to the work of J. Lett: “A bright IR source has been detected within a bright-rimmed dust cloud at the edge of the IC 1848 H II region. The source appears to be an early-type star with a circumstellar dust shell typical of protostars. This star is associated with the position of greatest CO excitation in a dense molecular cloud. The contours of CO emission correspond to those of the bright-rimmed dust cloud, showing that the star formed within the bright rim. Formaldehyde observations at 6 cm, 2 cm, and 2 mm are used to determine the density of the layer between the star and the ionized gas of the bright H..cap alpha.. rim. The location of this star, with respect to the dense molecular cloud which is subject to the external pressure of HII region, indicates the possible role of the expansion of IC 1848 in triggering star formation in dense regions at the perimeter of the H II region. The observed CO emission is used to determine the required luminosity of the embedded star. An early-type star of this luminosity should be detectable as a compact continuum source.”

Indeed, NGC 1848 is in the earliest stages of massive star birth, but it’s hidden behind its dust. According to Murry (et al): “We have completed a multiband (ultraviolet, optical, and near-infrared) study of the interstellar extinction properties of nine massive stars in IC 1805 and IC 1848, which are both part of Cas OB6 in the Perseus spiral arm. Our analysis includes determination of absolute extinction over the wavelength range from 3 ?m to 1250 Å. We have attempted to distinguish between foreground dust and dust local to Cas OB6. This is done by quantitatively comparing extinction laws of the least reddened sightlines (sampling mostly foreground dust) versus the most reddened sightlines (sampling a larger fraction of the dust in the Cas OB6 region). We have combined previous investigations to better understand the evolution of the interstellar medium in this active star forming region. We found no variation of extinction curve behavior between moderately reddened and heavily reddened Cas OB6 stars”.

Shrouded in mystery yet home to Globulettes – the seeds of brown dwarfs and free-floating planetary-mass objects. From the work of G. F. Gahm (et al): “Some H II regions surrounding young stellar clusters contain tiny dusty clouds, which on photos look like dark spots or teardrops against a background of nebular emission which we call “globulettes,” since they are much smaller than normal globules and form a distinct class of objects. Many globulettes are quite isolated and located far from the molecular shells and elephant trunks associated with the regions. Others are attached to the trunks (or shells), suggesting that globulettes may form as a consequence of erosion of these larger structures. Since the globulettes are not screened from stellar light by dust clouds farther in, one would expect photoevaporation to dissolve the objects. However, surprisingly few objects show bright rims or teardrop forms. We calculate the expected lifetimes against photoevaporation. These lifetimes scatter around 4 × 106 yr, much longer than estimated in previous studies and also much longer than the free-fall time. We conclude that a large number of our globulettes have time to form central low-mass objects long before the ionization front, driven by the impinging Lyman photons, has penetrated far into the globulette. Hence, the globulettes may be one source in the formation of brown dwarfs and free-floating planetary-mass objects in the galaxy.”

Apparently there’s a lot to contemplate when you look into the “Soul”….

Many thanks to AORAIA member Ken Crawford for this hugely inspiring image!