Astronomy Archives

May 12, 2008December 24, 2015 by Fraser Cain

What is Venus Made Of?

Venus is often called Earth’s twin planet. And when it comes to the composition, Venus is very similar to Earth. But it does have a few significant differences.

The diameter of Venus is just 650 km less than the Earth’s, and its mass is 81.5% of planet Earth.

Looking inside Venus is much harder. Here on Earth, scientists probe the structure of the Earth’s core by studying how seismic waves from earthquakes bounce off the interior of the planet. Only a few landers have reached the surface of Venus, and they didn’t last long.

Since Earth and Venus have similar size and density, scientists assume that Venus has a similar internal structure to Venus, with a core, mantle, and crust. The interior of Venus is probably at least partially liquid.

One big difference between Earth and Venus; however, is the fact that Venus has no plate tectonics. This is probably because the surface and atmosphere of Venus are so dry and hot. This reduces the amount of heat lost from the interior of the planet, and prevents it from cooling. This might also explain why Venus doesn’t have an internally magnetic field; such as the one generated by Earth.

May 12, 2008December 24, 2015 by Jerry Coffey

How to Find Venus in the Sky

Venus orbits closer to the Sun than Earth, so explaining how to find Venus in the sky is pretty easy. It will be fairly close to the Sun. Venus orbits the Sun faster than the Earth so it will either appear in the sky in the West in the evening or rise before the Sun in the East.

To pinpoint the location of Venus you can use some form of planetarium software like Starry Nights or you can do it the old fashioned way and train your telescope yourself. There are a few things to consider when doing that. The first is to understand what ecliptic plane is. When you trace the path of the Sun across the sky, its path is a line called the ecliptic. The ecliptic changes slightly throughout the year. It actually rises and falls. The highest point occurs at the summer solstice, while the lowest position happens six months later at winter solstice.

Most celestial bodies are most easily observed during an elongation. An elongation occurs when an inferior(closer to the Sun) planet’s position in its orbital path is at tangent to the view from Earth. Because they are inside the Earth’s orbits their positions are never very far from the position of the Sun. When a planet is at elongation, it is furthest from the Sun as viewed from Earth, so it’s view is best at that point. There are two kinds of elongations. The Eastern Elongation occurs when the planet is in the evening sky and the Western Elongation occurs when a planet is in the morning sky. This paragraph assumes that we are talking about viewing from Earth. The apparent motion of objects in the sky due to the rotation of the Earth is 15 degrees per hour. Venus is not visible against the Sun’s background light until it is 5 degrees from the Sun, so it can not be seen until 20 minutes after sunset or before sunrise. At its greatest eastern and western elongations, Venus is between 45 to 47 degrees from the Sun and moves 3 hours 8 minutes behind or in front of the Sun. That only leaves about 2 hours and 48 minutes of observation in a given day.

Once you know how to find Venus in the sky, you will need a telescope to see anything other than a light in the sky. Also, you should have a planetary filter or off-axis mask. Still, it might be best to invest in a telescope with an automatic tracking system so that you can focus all of your attention on observing and not be constantly adjusting your scope. Good luck on your quest to observe Venus.

We have written many articles about Venus for Universe Today. Here’s are facts about Venus.

If you’d like more information on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We’ve also recorded an entire episode of Astronomy Cast all about Venus. Listen here, Episode 50: Venus.

References:
http://planet-venus.net/index.php?document_id=100
http://www-istp.gsfc.nasa.gov/stargaze/Secliptc.htm

May 12, 2008December 24, 2015 by Jerry Coffey

What is the Gravity on Venus?

Venus is the virtual twin of Earth in many ways. Similar size, mass and density. But what is the gravity on Venus? According to our friends over at NASA, the answer is 8.87 m/s². To translate that a little more, it is about 90% of the gravity here on Earth. A person who measures 100 kg when they leave home would tip the scales on the Venusian surface at 90 kg.

The surface gravity of Venus is not the only characteristic of the planet that nearly mirrors Earth. Venus has 86% of the volume that Earth has along with 82% of the mass. The planet’s density is nearly identical at 5.243 g/cm³.

In order to shed that ten kilos you would have to spend a couple of months in space. Once you arrived the real trouble would begin. Science has not been able to develop a spacesuit that could survive more than a few minutes in the harsh environment of Venus. To start with there is the 470C surface temperature. That is 9 times the temperatures in the hottest deserts here on Earth. The heat would not destroy your suit though. The atmosphere is 96% carbon dioxide and full of sulfuric acid clouds and droplets and ash from the volcanoes that dot the surface. The atmosphere is so thick that most meteors could not penetrate it, burning up before impact instead.

While there have been many large volcanoes here on Earth, there is no real comparison to the number, size, and extent of the volcanic activity on Venus. The Venusian surface is dominated by the more than 1,000 volcanoes or volcanic centers that are larger than 20 km. Lava flows are thought to have completely resurfaced the planet between 300 and 500 million years ago.

The reflective nature of the sulfuric acid in the atmosphere has made visual observation of the surface impossible. It was early in the 20th century, when astronomers were able to make spectroscopic, ultraviolet, and radar observations, before much was known about the planet. Surface features went undetected until radar observations were made in the 1970s.

Fifty years ago no one could have accurately told you much about Venus gravity. It was still a mystery at the beginning of the 20th century. In many ways it can be considered the Earth’s near twin, but the planet is still a host of mysteries that need to be solved. The Venus Express spacecraft has contributed a great deal of data. BepiColumbo and Akatsuki may be able to add a great deal more in 2014 and 2016, respectively. All we can do is wait and see.

We have written many articles about Venus for Universe Today. Here are some interesting facts about Venus, and here’s an article about the color of Venus.

If you’d like more information on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We’ve also recorded an entire episode of Astronomy Cast all about Venus. Listen here, Episode 50: Venus.

References:
NASA Venus Facts
NASA Solar System Exploration on Venus

May 12, 2008December 24, 2015 by Fraser Cain

Scientific Data Recovered from a Hard Drive that Crashed With Columbia

It would be amazing to think that anything could have survived the fiery destruction of the space shuttle Columbia, which broke up above Texas on February 1st, 2003, killing all 7 astronauts. Amazingly, tiny worms survived the break up and crash. And now, data recovery experts announced they were able to salvage scientific data from a charred hard drive.

The announcement was made last week by data recovery company Kroll Ontrack Inc. When they received a smashed up hard drive from NASA, it just looked like a hunk of metal. But after painstaking work, they were able to recover 99% of the information stored on the hard drive.

The hard drive was part of study of the critical viscosity of xenon gas. As the data were being gathered on board Columbia as part of its mission, they were being transmitted back down to Earth. They had only transmitted part of the data, enough to tell researchers that the experiment was working. They were going to wait until Columbia landed to get the rest. Of course, Columbia never landed.

What NASA sent to Kroll Ontrack was almost unrecognizable as a hard drive. Jon Edwards, a senior clean room engineer at the company said that the circuit board on the drive was burned beyond recognition and that all its components had fallen off. Every piece of plastic on the 400 MB Seagate hard drive had melted, and the chips were burned.

Unfortunately, two other drives that crashed with Columbia were so damaged that no data could could be extracted from them. One of the Seagate’s keys to its survival is that it was actually quite old and had a much lower data capacity. The 400 MB drive was about 8 years old in 2003. It had much more fault tolerance and durability that current hard drive capacity.

Engineers were able to remove the hard drive platters from the destroyed drive and transfer them to a new drive. From there they were able to reconstruct 99% of the data.

Original Source: Scientific American

May 12, 2008December 24, 2015 by Tammy Plotner

Revealing The Undiscovered – Van Den Bergh 149/50 and Lynds Dark Nebula 1235 by Tom Davis

Over the past few weeks we’ve taken a look at some pretty incredible regions of space through astrophotography – Wolf Rayet stars, Thackeray’s Globules, tidal interactions and even giant dust clouds bursting with star birth. This time, let’s take a look at something so obscure that it might even be the first time that it’s been photographed…

What you’re looking at van den Bergh 149 (RA 22 09 08.5 Dec +72 53 05), van den Bergh 150 (RA 22 09 40.1 Dec +73 23 27) , and dark nebula LDN1235; Cepheus. According to image author, Tom Davis: “These two reflection nebulae are rarely imaged and this image may well be a premiere for amateur astroimaging. vdB 149 is the blue reflection nebula on the center left; vdB150 the center right. The darker nebula just “above” vdB150 is Lynds Dark Nebula 1235. It is likely an Extended Red Emission nebula (ERE). These ERE are galactic dark nebulae at high latitudes that become visible through illumination by the interstellar radiation field. ERE is a dust-luminescence process, which appears in a broad band extending in wavelength across the R-band (Schedler). This image is a composite-hybrid between two images taken with telescopes of different focal lengths. These nebulae have very low surface brightness and pose a significant challenge in imaging them. There are even fainter wisps of dust that make up the sky background. These small clouds are yet uncataloged as far as I can find through research. ”

In 1966, Sidney Van Den Bergh produced his own catalog of bright nebula with embedded stars. It contains information for “all BD and CD stars north of -33 deg which are surrounded by reflection nebulosity visible on both the blue and red prints of the Palomar Sky Survey. The nearer reflection nebulae lie predominantly along Gould’s Belt, whereas the more distant ones are concentrated to the galactic plane. The data outline 13 associations of reflection nebulae, some of which coincide with known OB or T associations. Attention is drawn to the fact that most reflection nebulae are illuminated by the integrated light of the Milky Way. The integrated radiation will be more intense above and below the galactic plane then in the galactic plane where the nuclear bulge of the Galaxy and most of the disk are obscured by interstellar absorption.”

Ninth magnitude vdB 149 first appeared in scientific literature around 1957 during a search for cepheids in galactic clusters done by Sidney Van Den Berg. Later, in 1960, it was also picked up by Halton Arp and more formally in 1966 when Van Den Berg did his “Study of Reflection Nebulae” utilizing the Palomar Sky Survey plates. It is also the 159th reflection nebula corresponding to HD 224403 (GLON=116.6, GLAT=-00.22) is introduced by R. Racine in his study of stars in Reflection Nebulae in 1968 where photometric and spectroscopic observations were done for fifteen distinct regions.

However, 8.4 magnitude vdB 150 holds a much more colorful history, having been noted in 1918 by Annie Jump Cannon and Edward Pickering. Annie picked it up again in 1925 during the extended Henry Draper Catalog Study and again in 1949 in a commemorative work done with Walton Mayall. From there, it laid dormant until 1991 and 1995 when revisited again by the Astrographic Catalogue for spectral type, proper motion and position. It holds its place in basic data as HD 210806 — Star in Nebula.

Like the Van Den Bergh catalogs of bright nebula where curtains of gas and dust conjoin with stars, the Lynds Dark Nebula catalog was developed in much the same way – compiled from studies of the red and blue prints from the Palomar Sky Survey. “The range in declination is from +90 to -33 degrees. A cloud had to be visible on both the red and the blue photographs in order to be recorded. It is therefore very probable that the more tenuous clouds which may be transparent in the red are not included herein. Lynds states that it was often difficult to detect a cloud that absorbed less than 0.75 magnitudes. Many of the small dark nebulae termed `Bok Globules‘ are not included in this catalog because they are apparent as dark objects projected against the bright background of an emission nebulosity: only objects which, on the basis of stellar density fluctuations, indicated the presence of absorption are contained here.”

Do these regions meet and produce new anomalies which need further study? I’d say that’s affirmative. It’s a well known fact LDN 1235 contains a variable star and that Lynd’s dark nebulae have differing turbulent velocities. There are areas where the opacity is weak and may very well have reached excitation temperatures – the density decreases and the temperature increases along the outward edges. Although it’s only conjecture on my part, I’d say that photographic studies like those done by Tom Davis are extremely important in the long term. They provide photographic record of changes not captured by professional observatories and will eventually become a source of future reference.

One that both amateur and professionals can study and enjoy…

This week’s awesome image is done by MRO member, Tom Davis. They were taken with an Astro Systeme Austria N12 f/3.5 Astrograph (LUM) and Takahashi FSQ-106 f/5 Astrograph (RGB) KAI-11000M – Total Exposure 10.6+ hours; LRGB 260:120:120:120 minutes, unbinned – April-May 2008; Inkom, ID, USA.

May 9, 2008March 24, 2012 by Nancy Atkinson

ISS Astronaut on Colbert Report

The Colbert Report has gone galactic! ISS astronaut Garrett Reisman joked with Stephen Colbert on Comedy Central last night. It’s a very fun interview. Laser cannons and alien puppet masters are mentioned.

Source: Comedy Central

May 9, 2008December 24, 2015 by Fraser Cain

That’s WMAP, Seen from Earth

Okay, now astronomers are just showing off. See the three little multicolored dots in the upper right of this image? That’s NASA’s WMAP satellite, seen from a distance of 1.5 million km. The photograph was taken from the 2.2 meter telescope at the European Southern Observatory at La Silla, Chile. Apart from demonstrating some impressive imagine power and technique, the astronomers are testing out new tracking techniques for ESA’s upcoming Gaia space observatory.

The technique for finding your place in the Universe is called astrometry. Star Trek’s Enterprise would rely on this kind of information to navigate from star to star. In reality, though, astronomers compile this information to understand the Solar System’s position in relation to the rest of the Milky Way.

The last mission focused on this process was ESA’s Hipparcos mission, which wrapped up in the year 1993. Hipparcos measured the distance to 120,000 stars with great accuracy, as well as another 400,000 stars with less accuracy.

ESA’s new mission, due for launch in 2011, is called Gaia, and will travel to the Sun-Earth L₂ Lagrangian point. From this vantage point, it’ll create a precise three-dimensional map of stars throughout the Milky Way galaxy, and beyond. All in all, it will eventually create a catalogue of 1 billion stars.

When Gaia finally launches, knowing its position accurately in the Solar System is everything. And so, astronomers on Earth will need to be able to track its position in the sky, and relay this data back to the spacecraft, so it can make its calculations.

By demonstrating that they can already track the WMAP spacecraft, currently at the L₂ Lagrangian point, the astronomers have proven that they should be able to watch Gaia as well. In fact, Gaia should be brighter than WMAP.

You might be wondering why the WMAP image shows three different colours. The astronomers photographed the region three times in black and white, and then artificially coloured them red, blue and green. Since the stars don’t move, the three colours add up to make them appear white. The moving WMAP is clearly different from the background.

Original Source: ESA Image of the Week

May 9, 2008December 24, 2015 by Fraser Cain

Hubble Image of the Colliding Antennae Galaxies (with Video)

It’s time for another beautiful image from the Hubble Space Telescope. And this time, there’s an added bonus… video. The latest images released by Hubble are based on research of the Antennae Galaxies, known as NGC 4038 and NGC 4039. Astronomers used to think that they were 65 million light-years away, but the new research puts them much closer; probably 45 million light-years away.

This image was captured by Hubble’s Advanced Camera for Surveys and Wide Field Planetary Camera 2, to observe individual stars spawned by the cosmic collision.

Here’s the Hubble video to help you get a sense of the scales involved (with pretty music too).

The astronomers targeted the object’s southern tidal tail, which was thrown away from the active central regions. This tail contains material hurled away from the main galaxies as they came together. Astronomers looked for older red giants to make the estimate for their distance. These red giants are known to always shine with the same brightness, and by knowing this brightness, they were able to calculate the galaxies as being 45 million light-years away.

Since this galactic merger is happening relatively close, it’s one of the best examples astronomers have to study this process. And now that the galaxies are closer than astronomers previously believed, it changes the size of many objects the astronomers are studying. For example, the size of the star clusters being formed by the collision match the size of other galaxy mergers, instead of being 1.5 times larger than they should be.

The Antennae Galaxies are named for the two long tails of stars, gas and dust thrown out of the collision that resemble the antennae of insects. They can be found in the constellation of Corvus, the Crow.

Original Source: Hubble News Release

May 9, 2008December 24, 2015 by Tammy Plotner

The Weekend SkyWatcher’s Forecast: May 9-11, 2008

Greetings, fellow SkyWatchers! Are you ready for a very incredible weekend? The action begins on Friday as we take you on a guided tour of the lunar surface. On Saturday, celebrate Astronomy Day with a very special unaided eye sky event and a return to the Moon. No rest for the wicked on Sunday… Because you’ll be seeing double! Time to get out your binoculars and telescopes and turn an eye to the sky, because…. Here’s what’s up!

Friday, May 9 – Today in 1962, the first Earth-based laser was aimed at crater Albategnius. Although it isn’t visible tonight, let’s take a look at what is visible just 1.5 light-seconds away! First is a Lunar Club challenge which won’t prove difficult because you’ll be working with a map. Relax! This will be much easier than you think. Starting at Mare Crisium, move along the terminator to the north following the chain of craters until you identify a featureless oval which looks similar to Plato seen on a curve. This is Endymion…and if you can’t spot it, don’t worry. Let’s take a look at some features which will point you to it!

Most prominent of all will be two craters to the north named Atlas and Hercules. The easternmost Atlas was named for the mythical figure who bore the weight of the world on his shoulders, and the crater spans 87 kilometers and contains a vivid Y-shaped rima in the interior basin. Western Hercules is considerably smaller at 69 kilometers in diameter, and shows a deep interior crater called G. Power up and look for the tiny E crater which marks the southern crater rim. North of both is another unusual feature which many observers miss. It is a much more eroded and far older crater which only shows a basic outline and is only known as Atlas E.

Since we’re here, let’s take a crater walk and see how many features we can identifyâ€¦ Good luck, and clear skies!

(1) Mare Humboldtianum, (2) Endymion, (3) Atlas, (4) Hercules, (5) Chevalier, (6) Shuckburgh, (7) Hooke, (8) Cepheus, (9) Franklin, (10) Berzelius, (11) Maury, (12) Lacus Somniorum, (13) Daniel, (14) Grove, (15) Williams, (16) Mason, (17) Plana, (18) Burg, (19) Lacus Mortis, (20) Baily, (21) Atlas E, (22) Keldysh, (23) Mare Frigoris, (24) Democritus, (25) Gartner, (26) Schwabe, (27) Thales, (28) Strabo, (29) de la Rue, (30) Hayn.

Saturday, May 10 – Today is Astronomy Day and something wonderful is happening in the sky! Somewhere out there, the Moon is silently occulting Mars, and the Red Planet will be hauntingly close to the limb as the skies darken… For observers through India and Europe, you have the chance to watch the occultation, so visit IOTA for specific times in your location!

Tonight let’s journey to the Moon as we look at a beautiful series of craters – Fabricius, Metius and Rheita. Bordered on the south by shallow Jannsen, Lunar Club challenge Fabricius is a 78 kilometer diameter crater highlighted by two small interior mountain ranges. To its northeast is Metius, which is slightly larger with a diameter of 88 kilometers. Look carefully at the two. Metius has much steeper walls, while Fabricius shows differing levels and heights. Metius’ smooth floor also contains a very prominent B crater on the inside of its southeast crater wall. Further northeast is the lovely Rheita Valley which stretches almost 500 kilometers and appears more like a series of confluent craters than a fault line. 70 kilometer diameter crater Rheita is far younger than this formation because it intrudes upon it. Look for a bright point inside the crater which is its central peak.

Since tonight will be our last chance to galaxy hunt for a while when the Moon has westered, let’s take a look at one of the brightest members of the Virgo Cluster – M49. Located about eight degrees northwest of Delta Virginis almost directly between a pair of 6th magnitude stars (RA 12 29 46 Dec +07 59 59), the giant elliptical M49 holds the distinction of being the first galaxy in the Virgo cluster to be discovered – and only the second beyond our local group. At magnitude 8.5, this type E4 galaxy will appear as an evenly illuminated egg shape in almost all scopes, and as a faint patch in binoculars. While a possible supernova event occurred in 1969, don’t confuse the foreground star noted by Herschel with something new!

Although most telescopes won’t be able to pick this region apart – especially with the Moon so near – there are also many fainter companions near M49, including NGC 4470. But a sharp-eyed observer named Halton Arp noticed them and listed them as Peculiar Galaxy 134 – one with “fragments!”

Sunday, May 11 – Tonight no two lunar features in the north will be more prominent than Aristoteles and Eudoxus. Viewable even in small binoculars, let’s take a closer look at larger Aristoteles to the north.

As a Class I crater, this ancient old beauty has some of the most massive walls of any lunar feature. Named for the great philosopher, it stretches across 87 kilometers of lunar landscape and drops below the average surface level to a depth of 366 meters – a distance which is similar to Earth’s tallest waterfall, the Silver Cord Cascade. While it has a few scattered interior peaks, the crater floor remains almost unscarred. As a telescopic Lunar Club challenge, be sure to look for a much older crater sitting on Aristoteles’ eastern edge. Tiny Mitchell is extremely shallow by comparison and only spans 30 kilometers. Look carefully at this formation, for although Aristoteles overlaps Mitchell, the smaller crater is actually part of the vast system of ridges which supports the larger one.

When you’re done, let’s have a look at another delightful pair that’s joined together – Gamma Virginis…

Better known as Porrima, this is one cool binary; whose members are nearly equal in spectral type and brightness. Discovered by Bradley and Pound in 1718, John Herschel was the first to predict this pair’s orbit in 1833 and state that one day they would become inseparable to all but the very largest of telescopes – and he was right. In 1920 the A and B stars had reached their maximum separation, but during 2007 they were as close together as they will ever be in our lifetimes. Observed as a single star in 1836 by William Herschel, its 171 year periastron now puts Porrima almost the same position as it was when Sir William saw it!

Have a great weekend… 😉

This week’s awesome images: Atlas Crater Map Image: Greg Konkel Annotations: Tammy Plotner – Fabricius, Metius and Rheita – Credit: Alan Chu – Aristoteles – Credit: Wes Higgins – Gamma Virginis: Porrima – Credit: Palomar Observatory, courtesy of Caltech. Thank you!!

May 8, 2008December 24, 2015 by Nancy Atkinson

Category: Astronomy